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Abstract

Critical limb ischemia (CLI) is the advanced stage of peripheral artery disease spectrum and is defined by limb pain or impending limb loss because of compromised blood flow to the affected extremity. Current conventional therapies for CLI include amputation, bypass surgery, endovascular therapy, and pharmacological approaches. Although these conventional therapeutic strategies still remain as the mainstay of treatments for CLI, novel and promising therapeutic approaches such as proangiogenic gene/protein therapies and stem cell‐based therapies have emerged to overcome, at least partially, the limitations and disadvantages of current conventional therapeutic approaches. Such novel CLI treatment options may become even more effective when other complementary approaches such as utilizing proper bioscaffolds are used to increase the survival and engraftment of delivered genes and stem cells. Therefore, herein, we address the benefits and disadvantages of current therapeutic strategies for CLI treatment and summarize the novel and promising therapeutic approaches for CLI treatment. Our analyses also suggest that these novel CLI therapeutic strategies show considerable advantages to be used when current conventional methods have failed for CLI treatment.

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... Major constraints of this common model, including acute vascular injury disparate from clinical disease manifestation and small muscle volumes incomparable to human leg vascular inflow and metabolic activity, lead to failure in predicting PAD patient efficacy [7][8][9]. Unknowns also remain regarding the optimal therapeutic delivery strategy in humans in terms of dosage, location, method, and frequency [7,10,11]. Therefore, many phase II and III trials showed no primary outcome efficacy vs. placebo [12][13][14][15][16]. JUVENTAS cited functional neovascularization in rat HLI, but no differences in major amputation nor secondary outcomes were seen with bone marrow mononuclear cells vs. placebo in humans [12,17]. TAMARIS noted vascular growth using an FGF-1 plasmid in hamster HLI but no clinical improvements vs. placebo in amputation nor death [14,18]. ...
... These swine models have neither exhibited sustained limb dysfunction nor muscle perfusion deficits for multiple weeks post-model creation, making it difficult to assess therapeutic potency and guide clinical trial design [21][22][23][24][25][26][27]. Large animal optimization may be particularly beneficial for cellular therapies, which show low retention post-administration in ischemic tissue [3,7,10,11,28,29]. Real-time localization of viable cells preclinically begins to ascertain the duration of beneficial effects in patients. ...
... Swine gait patterns were quantified pre-and post-ligation with a 16-ft custom animal walkway system (Tekscan, Inc.) and analyzed with accompanying software. Multiple trotting passes (2)(3)(4)(5)(6)(7)(8)(9)(10)(11) were used for each session with data averaged to obtain one value per animal at each time point. ...
Article
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Currently, there is no large animal model of sustained limb ischemia suitable for testing novel angiogenic therapeutics for peripheral artery disease (PAD) such as drugs, genes, materials, or cells. We created a large animal model suitable for efficacy assessment of these therapies by testing 3 swine hind limb ischemia (HLI) variations and quantifying vascular perfusion, muscle histology, and limb function. Ligation of the ipsilateral external and bilateral internal iliac arteries produced sustained gait dysfunction compared to isolated external iliac or unilateral external and internal iliac artery ligations. Hyperemia-dependent muscle perfusion deficits, depressed limb blood pressure, arteriogenesis, muscle atrophy, and microscopic myopathy were quantifiable in ischemic limbs 6 weeks post-ligation. Porcine mesenchymal stromal cells (MSCs) engineered to express a reporter gene were visualized post-administration via positron emission tomography (PET) in vivo. These results establish a preclinical platform enabling better optimization of PAD therapies, including cellular therapeutics, increasing bench-to-bedside translational success. Graphical abstract A preclinical platform for porcine studies of peripheral artery disease therapies including (1) a hind limb ischemia model and (2) non-invasive MSC viability and retention assessment via PET
... 20-30% of patients with CLI are ineligible for revascularization, or the surgery has failed due to distal flow impairment [8]. The Food and Drug Administration (FDA) has not yet approved any additional effective CLI therapies, underlining the essential requirement to explore alternative treatment options to recover the blood flow and to enhance the grade of healthcare services for life-threatening conditions [9,10]. As extensive gene therapy trials studies have failed, even though there is continuing attention to assessing HGF [9], and there are concerns regarding cell therapy, such therapy has not yet been approved for clinical Open Access *Correspondence: Soleim_m@modares.ac.ir ...
... Disease-specific quality of life measures are ideal for CLI populations because they address the patient's specific restrictions, making them more able to identify significant clinical changes in health conditions regarding the progression of the disease or treatment [2]. Another functional outcome is improved wound healing that an independent physician evaluates and evidences by photography at the end of the follow-up period [10]. ...
... Therefore, cell therapy must show efficacy in terms of amputation and death to become a generally accepted treatment [71]. Amputation is correlated with poor overall survival; Amputation is the only choice when ischemic tissues are exposed to uncontrollable infections and when surgical or non-surgical techniques cannot repair rest pain or tissue loss [10]. ...
Article
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Critical limb ischemia (CLI), the terminal stage of peripheral arterial disease (PAD), is characterized by an extremely high risk of amputation and vascular issues, resulting in severe morbidity and mortality. In patients with severe limb ischemia with no alternative therapy options, such as endovascular angioplasty or bypass surgery, therapeutic angiogenesis utilizing cell-based therapies is vital for increasing blood flow to ischemic regions. Mesenchymal stem cells (MSCs) are currently considered one of the most encouraging cells as a regenerative alternative for the surgical treatment of CLI, including restoring tissue function and repairing ischemic tissue via immunomodulation and angiogenesis. The regenerative treatments for limb ischemia based on MSC therapy are still considered experimental. Despite recent advances in preclinical and clinical research studies, it is not recommended for regular clinical use. In this study, we review the immunomodulatory features of MSC besides the current understanding of different sources of MSC in the angiogenic treatment of CLI subjects and their potential applications as therapeutic agents. Specifically, this paper concentrates on the most current clinical application issues, and several recommendations are provided to improve the efficacy of cell therapy for CLI patients.
... 70 ischemic gangrene as a result of compromised blood flow to the affected extremity. Approximately 40 % of patients with CLI are ineligible for surgical or endovascular revascularization (no-option CLI patients) with 1-year mortality rate from 10 % to 40 % and 25 % 1-year amputation rate (Becker et al. 2011, Hassanshahi et al. 2019. Chronic ischemic diseases are characterized by macrovascular alterations accompanied by microvascular abnormalities, involving endothelial dysfunction mediated by inflammation, oxidative stress and ischemia (Vemulapalli et al. 2015). ...
... Despite the modern development of therapeutic techniques and methods, the treatment of no-option CLI patients is still very limited, among which stem cell transplantation appears to be one of the most promising alternative option. Stem cells are a class of undifferentiated cells with unique self-renewal capacity and the ability to differentiate into various cell types (Hassanshahi et al. 2019). ...
Article
Autologous stem cell therapy is the most promising alternative treatment in patients with chronic ischemic diseases, including ischemic heart disease and critical limb ischemia, which are characterized by poor prognosis related to serious impair of quality of life, high risk of cardiovascular events and mortality rates. However, one of the most serious shortcomings of stem cell transplantation are low survival after transplantation to the site of injury, as large number of stem cells are lost within 24 hours after delivery. Multiple studies suggest that combination of lipid-lowering drugs, statins, and stem cell transplantation might improve therapeutic efficacy in regenerative medicine. Statins are inhibitors of HMG-CoA reductase and belong to recommended therapy in all patients suffering from critical limb ischemia. Statins possess non-lipid effects which involve improvement of endothelial function, decrease of vascular inflammation and oxidative stress, anti-cancer and stem cell modulation capacities. These non-lipid effects are explained by inhibition of mevalonate synthesis via blocking isoprenoid intermediates synthesis, such as farnesylpyrophospate and geranylgeranylpyrophospate and result in modulation of the PI3K/Akt pathway. Moreover, statin-mediated microRNA regulation may contribute to the pleiotropic functions. MicroRNA interplay in gene regulatory network of IGF/Akt pathway may be of special significance for the treatment of critical limb ischemia. We assume further studies are needed for detailed analysis of statin interactions with microRNA at the molecular level and their link to PI3K/Akt and IGF/Akt pathway in stem cells, which are currently the most promising treatment strategy used in chronic ischemic diseases.
... Conventional treatments for CLI include arterial bypass and endovascular therapy. However, these therapeutic approaches are rather invasive, and are not suitable for CLI patients with severe comorbidity or sepsis [5,6]. There has been extensive interest in alternative approaches to address current limitations, such as proangiogenic growth factor therapy [7], gene therapy [8], and stem cell therapy [9]. ...
... The stem cells may also have the capacity of differentiating into endothelial cells for vascularization [10,12,13]. Therefore, stem cell therapy possesses greater potentials than the other approaches in promoting ischemic tissue regeneration [6]. ...
Article
Stem cell transplantation has been extensively explored to promote ischemic limb vascularization and skeletal muscle regeneration. Yet the therapeutic efficacy is low due to limited cell survival under low oxygen environment of the ischemic limbs. Therefore, continuously oxygenating the transplanted cells has potential to increase their survival. During tissue regeneration, the number of blood vessels are gradually increased, leading to the elevation of tissue oxygen content. Accordingly, less exogenous oxygen is needed for the transplanted cells. Excessive oxygen may induce reactive oxygen species (ROS) formation, causing cell apoptosis. Thus, it is attractive to develop oxygen-release biomaterials that are responsive to the environmental oxygen level. Herein, we developed oxygen-release microspheres whose oxygen release was controlled by oxygen-responsive shell. The shell hydrophilicity and degradation rate decreased as the environmental oxygen level increased, leading to slower oxygen release. The microspheres were capable of directly releasing molecular oxygen, which are safer than those oxygen-release biomaterials that release hydrogen peroxide and rely on its decomposition to form oxygen. The released oxygen significantly enhanced mesenchymal stem cell (MSC) survival without inducing ROS production under hypoxic condition. Co-delivery of MSCs and microspheres to the mouse ischemic limbs ameliorated MSC survival, proliferation and paracrine effects under ischemic conditions. It also significantly accelerated angiogenesis, blood flow restoration, and skeletal muscle regeneration without provoking tissue inflammation. The above results demonstrate that the developed microspheres have potential to augment cell survival in ischemic tissues, and promote ischemic tissue regeneration in a safer and more efficient manner.
... Unfortunately, not all the patients are amenable to surgical revascularization through coronary artery bypass surgery, percutaneous coronary intervention, or the deployment of intracoronary stents [5]. Pharmacological treatment with a wide array of drugs, including statins, prostanoids, and phosphodiesterase inhibitors, can be exploited as an adjuvant therapy to alleviate the symptoms and burden of PAD when surgical intervention is not feasible or fails to restore blood flow [6]. Therefore, novel and more efficient therapeutic approaches to promote neovascularization and rescue blood supply to ischemic tissues are urgently required. ...
... Current strategies to induce vascular regrowth of ischemic tissues include the delivery of pro-angiogenic genes or peptides, e.g., vascular endothelial growth factor (VEGF)-A and fibroblast growth factor (FGF)-4 [5], or stem cell transplantation [7]. Cellbased therapy consists of the mobilization or transplantation of multiple types of pro-angiogenic stem cells, including bone marrow-derived mesenchymal stem cells (MSCs), hematopoietic cells, and endothelial progenitor cells (EPCs) [6][7][8][9]. As vascular endothelial cells possess limited regenerative capacity, there is growing interest in circulating EPCs due to their recognized role in the maintenance of endothelial integrity, function, and postnatal neovascularization [10][11][12][13]. ...
Article
Full-text available
Cardiovascular disease (CVD) comprises a range of major clinical cardiac and circulatory diseases, which produce immense health and economic burdens worldwide. Currently, vascular regenerative surgery represents the most employed therapeutic option to treat ischemic disorders, even though not all the patients are amenable to surgical revascularization. Therefore, more efficient therapeutic approaches are urgently required to promote neovascularization. Therapeutic angiogenesis represents an emerging strategy that aims at reconstructing the damaged vascular network by stimulating local angiogenesis and/or promoting de novo blood vessel formation according to a process known as vasculogenesis. In turn, circulating endothelial colony-forming cells (ECFCs) represent truly endothelial precursors, which display high clonogenic potential and have the documented ability to originate de novo blood vessels in vivo. Therefore, ECFCs are regarded as the most promising cellular candidate to promote therapeutic angiogenesis in patients suffering from CVD. The current briefly summarizes the available information about the origin and characterization of ECFCs and then widely illustrates the preclinical studies that assessed their regenerative efficacy in a variety of ischemic disorders, including acute myocardial infarction, peripheral artery disease, ischemic brain disease, and retinopathy. Then, we describe the most common pharmacological, genetic, and epigenetic strategies employed to enhance the vasoreparative potential of autologous ECFCs by manipulating crucial pro-angiogenic signaling pathways, e.g., extracellular-signal regulated kinase/Akt, phosphoinositide 3-kinase, and Ca 2+ signaling. We conclude by discussing the possibility of targeting circulating ECFCs to rescue their dysfunctional phenotype and promote neovascularization in the presence of CVD.
... Wounds are divided into two categories of acute and chronic wounds. Acute wounds heal at a predictable and expected rate of healing, while wounds that fail to heal within 6 weeks and exhibit inefficient cellular and molecular functions are termed chronic wounds, which may lead to limb amputation if left without proper treatment [2][3][4]. It has been suggested that about 188 proteins are expressed more than twofold in chronic wounds, which may cause chronic inflammation, impaired angiogenesis, and dampened cell survival [5]. ...
Article
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Macrophages are key immune cells that respond to infections, and modulate pathophysiological conditions such as wound healing. By possessing phagocytic activities and through the secretion of cytokines and growth factors, macrophages are pivotal orchestrators of inflammation, fibrosis, and wound repair. Macrophages orchestrate the process of wound healing through the transitioning from predominantly pro-inflammatory (M1-like phenotypes), which present early post-injury, to anti-inflammatory (M2-like phenotypes), which appear later to modulate skin repair and wound closure. In this review, different cellular and molecular aspects of macrophage-mediated skin wound healing are discussed, alongside important aspects such as macrophage subtypes, metabolism, plasticity, and epigenetics. We also highlight previous studies demonstrating interactions between macrophages and these factors for optimal wound healing. Understanding and harnessing the activity and capability of macrophages may help to advance new approaches for improving healing of the skin.
... Recently, in the field of clinical research for treating CLI and intractable foot-ulcer due to diabetes mellitus (DM), there are many reports describing the applications of regenerative medicine employing stem cells [5e7], scaffold [8], nanoparticle [9], and proangiogenic growth factor including vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), hepatocyte growth factor (HGF), and insulin-like growth factor (IGF-1) [10]. Although conventional therapeutic strategies for CLI treatment attempt to increase the processes of neoangiogenesis, neovascularization at the ischemic tissues is known to be difficult. ...
Article
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Introduction The treatment of intractable toe ulcer with critical limb ischemia (CLI) is a challenge because of its poor blood flow and the wound. Here, a novel fixation technique for artificial dermis with negative pressure wound therapy (NPWT) was reported. Method After the amputation of toe, artificial dermis made of collagen-gelatin sponge (CGS) was grafted onto the wound where human recombinant basic fibroblast growth factor (bFGF) was sprayed. The foot was put on adhesive iodine-impregnated drape, the artificial-dermis area was covered with a sponge dressing of which another end reached to the drape, and the vacuum port was applied on the dressing sponge sandwiched with two drapes and connected to an NPWT system. Since the shape of sponge-dressing was similar to that of elephant-trunk, the technique in this study was named an “Elephant-trunk” technique. Result During NPWT period, no complications such as air leakage, skin erosion, ischemic around tissue were confirmed. The artificial dermis was engrafted completely at one week after surgery, and the wound was confirmed to close completely. Conclusion This NPWT technique with bFGF and CGS accelerated the healing of wound treated conservatively with artificial dermis in CLI patients.
... Conservative management for CLI treatment is considered to complement physical revascularization, to modify the risk factors of CLI, [7] including antiplatelet therapy, anticoagulant therapy, antihypertensive therapy, lipid-lowering therapy, glycemic control in diabetes, smoking cessation, and regular physical activity, [7][8][9] and conservative management including intermittent pneumatic compression is even the only choice for the patients who are not suitable for surgery. [10][11][12] Conservative management has a certain effect in delaying atherosclerosis and improving the symptoms, but its effect on the prognosis of CLI is limited. Revascularization remains the main treatment option to improve the perfusion of the affected limb and has also been regarded as the cornerstone majority of the shortcomings of PTA. ...
Article
The treatment of critical limb ischemia (CLI) has long been a “hot spot” in medical science. It is widely believed that revascularization is the cornerstone of CLI therapy. However, there is currently no consensus on the best revascularization approach. Traditional open surgery is traumatic and associated with many complications. In recent years, great progress has been witnessed in terms of endovascular technology, gradually replacing open surgery in the treatment of CLI. In this review, the role of endovascular therapies in clinical practice, including conventional percutaneous transluminal angioplasty, bare-metal stent, and innovated drug-coated balloon, drug-eluting stent, bioresorbable vascular scaffold, cutting balloon angioplasty, atherectomy, intravascular lithotripsy, cryoplasty, and percutaneous deep venous arterialization is discussed.
... Current therapies for CLI comprise amputation, bypass surgery, endovascular therapy, and pharmacological approaches. In addition to these conventional therapeutic strategies, proangiogenic gene/protein therapy and transplantation of stem cells such as mesenchymal stem cells and endothelial progenitors have been recently applied for the treatment of CLI and associated wound complications [1,2]. The impaired wound healing in CLI results from multiple factors that affect many cell types and their behavior. ...
Article
Full-text available
Impaired wound healing in critical limb ischemia (CLI) results from multiple factors that affect many cell types and their behavior. Epidermal keratinocytes and dermal fibroblasts play crucial roles in wound healing. However, it remains unclear whether these cell types irreversibly convert into a non-proliferative phenotype and are involved in impaired wound healing in CLI. Here, we demonstrate that skin keratinocytes and fibroblasts isolated from CLI patients maintain their proliferative potentials. Epidermal keratinocytes and dermal fibroblasts were isolated from the surrounding skin of foot wounds in CLI patients with diabetic nephropathy on hemodialysis, and their growth potentials were evaluated. It was found that keratinocytes from lower limbs and trunk of patients can give rise to proliferative growing colonies and can be serially passaged. Fibroblasts can also form colonies with a proliferative phenotype. These results indicate that skin keratinocytes and fibroblasts maintain their proliferative capacity even in diabetic and ischemic microenvironments and can be reactivated under appropriate conditions. This study provides strong evidence that the improvement of the cellular microenvironments is a promising therapeutic approach for CLI and these cells can also be used for potential sources of skin reconstruction.
... Методы клеточной и генной терапии активно изучаются в настоящее время. Оба этих подхода предполагают создание в ишемизированной области пула клеток, выделяющих факторы, стимулирующие неоангиогенез (факторы роста фибробластов, гепатоцитов, эндотелия сосудов и другие), либо непосредственно участвующих в нем [8]. При клеточной терапии из периферической крови, костного мозга или мезенхимы пациента отбираются стволовые клетки, переводятся в необходимое состояние и вводятся в область ишемии. ...
Article
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p> Background. Several previous studies have demonstrated that spinal cord stimulation (SCS) can reduce the amputation rate in patients with critical lower limb ischemia (CLLI) and improve blood circulation parameters of the lower limbs. However, there is a lack of studies on the long-term effects of SCS on the quality of life (QoL) of patients with CLLI. Aim. The present study aimed to assess QoL changes in patients with CLLI after SCS system implantation in the long run (i.e., 30–60 months). Methods. This study included 38 patients with CLLI (10 females, 28 males; age range: 39–83 years) who underwent surgery in 2012–2016. QoL was analyzed using the SF-36 questionnaire before and 30–60 months after SCS. The mortality and amputation rates and amputation levels of the patients were also analyzed. The SF-36 questionnaire scores were normalized according to the data of the respective sex and age groups in the general Russian population. The obtained scores were analyzed in their dynamics and compared with the scores of the general population. Results. The preoperative scores of three of four physical well-being QoL parameters of the patients significantly reduced compared with the scores of the general population (p < 0.001). However, the scores of mental well-being QoL parameters were close to those of the general population. The total physical well-being score reduced (37.9 ± 9.2 points), whereas the total mental well-being score was within the medium range (48.1 ± 8.3 points). At 30–60 months after SCS system implantation, 5 patients or their representatives were unavailable, 12 died, 3 underwent amputation at the tibial level, and 16 showed preserved support function of the legs (2 of these patients underwent toe amputation). SCS system failure was noted in 3 patients. Patients with preserved support function of the legs completed the SF-36 questionnaire at 30–60 months after SCS system implantation. All QoL parameter scores showed increases, and the total postoperative physical well-being score of these patients was close to that of the general population (46.3 ± 10.6 points, p = 0.050 compared with the preoperative score). However, the total mental well-being score of the patients was higher than that of the general population (57.9 ± 3.8 points, p = 0.041). Conclusion. SCS does not reduce the mortality rate in patients with CLLI compared with conservative therapy. However, it reduces the amputation rate in patients who survive. Significant positive changes in QoL persist for a long time after SCS system implantation in most patients. Funding: The study did not have sponsorship. Conflict of interest: Authors declare no conflict of interest.</p
Chapter
Atherosclerosis is a systemic disease that affects all vascular beds, including coronary, cerebral, and peripheral arteries. With an estimated 236.6 million people living with peripheral artery disease (PAD), its prevalence ranks only behind coronary artery disease (CAD) and ischemic stroke in atherosclerotic diseases (Song et al., Lancet Glob Health 7(8):e1020–e1030, 2019). PAD is a common, underrecognized, and debilitating atherosclerotic disease of the lower extremities. Recognition and treatment of PAD remain relatively poor, in part due to the absence or subtlety of symptoms of early disease. Advanced PAD can manifest as a severely morbid condition resulting in progressive loss of function, as well as rest pain from claudication, gangrene, and limb amputation. Ischemic heart disease and stroke remain the leading causes of death globally and were responsible for 27% of all deaths in 2019 (The top 10 causes of death. World Health Organization, Geneva, 2020). Remarkably, however, the risk of an atherosclerotic cardiovascular disease (ASCVD) event is only modestly lower in patients with PAD compared to patients with CAD or prior stroke, and patients with PAD have an even higher risk of all-cause mortality (Colantonio et al., J Am Coll Cardiol 76(3):251–264, 2020). Our understanding of atherosclerosis has significantly advanced from earlier theories. In 1858, Virchow proposed that atherosclerosis was due to arterial injury propagating a maladaptive inflammatory and cellular process to generate atherosclerotic plaques (Basatemur et al., Nat Rev Cardiol 16(12):727–744, 2019). Work in the early 1900s by Ignatowski and Anichkov demonstrated that cholesterol was a critical mediator of atherosclerosis and recognized that lipid-rich diets increase the burden of atherosclerosis (Konstantinov and Jankovic, Tex Heart Inst J 40(3):247–249, 2013; Konstantinov et al., Tex Heart Inst J 33(4):417–423, 2006). Ross spearheaded the “response-to-injury” hypothesis in the 1970s, which further developed Virchow’s vascular injury theory to include platelet-derived factors, smooth muscle proliferation, and extracellular matrix deposition (Ross et al., Am J Pathol 86(3):675–684, 1977). Two decades later, the “response-to-retention” hypothesis proposed that atherogenic lipids are retained in arterial walls and induce an inflammatory cascade (Williams and Tabas, Arterioscler Thromb Vasc Biol 15(5):551–562, 1995; Ross, N Engl J Med 340(2):115–126, 1999). Since then, remarkable advances in scientific capabilities have greatly expanded our understanding of atherogenesis. The pathogenesis of PAD likely shares many common features of atherosclerosis in the coronary and cerebral arteries. Yet, the phenotype of PAD is unique, notable for intimal thickening with a paucity of inflammatory cells, a high prevalence of vascular calcification, and evidence that severe PAD that manifests as critical limb ischemia is at least in part a thromboembolic disease. This chapter will describe PAD, including its risk factors and epidemiology, normal and abnormal vascular function, pathogenesis of atherosclerosis, and the unique phenotype of PAD.
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This study aimed to evaluate the protective effect of chronic intermittent hypobaric hypoxia (CIHH) against limb ischemic injury. C57BL/6 mice were randomly divided into three groups: limb ischemic injury group (Ischemia, induced by ligation and excision of the left femoral artery), limb ischemia following CIHH pretreatment group (CIHH+Ischemia, simulated a 5000-m altitude hypoxia, 6 h per day for 28 days, before induction of hind-limb ischemia.), and sham group (Sham). The blood flow in the mouse models of hind-limb ischemia was examined using laser doppler imaging. The functional and morphological performance of ischemic muscle was evaluated using contraction force and hematoxylin-eosin and Masson's trichrome staining. Angiogenesis was determined by immunohistochemistry staining of the endothelial markers CD31 and CD34. The protein expressions of angiogenesis-related genes were detected using western blot assay. Chronic ischemia resulted in reduced blood perfusion, decreased contraction tension, and morphological destruction in gastrocnemius muscle. CIHH pretreatment increased the contractile force and muscle fiber diameter, decreased necrosis and fibrosis of the ischemic muscle. Also, CIHH significantly increased the density of CD31+ and CD34+ cells and promoted the expression of angiogenesis-related molecules in ischemic muscle. These data demonstrate that CIHH has a protective effect against chronic limb ischemia by promoting angiogenesis.
Article
Critical limb ischemia (CLI) is a severe state of peripheral artery disease with high unmet clinical needs. Further, there are no effective treatment options for CLI patients. Based on preclinical study results, predicting the clinical efficacy of CLI treatments is typically difficult because conventional hindlimb ischemia (HLI) rodent models display spontaneous recovery from ischemia, which is not observed in CLI patients. Therefore, we aimed to develop a novel chronic and severe HLI model to properly evaluate the therapeutic effects of drug candidates for CLI. Severe HLI mice (Type-N) were generated by increasing the excised area of blood vessels in a hindlimb of NOG mice. We selected chronic Type-N mice without spontaneous recovery of blood flow based on the number of necrotic nails and blood flow rate at 2 weeks after surgery. Immunohistochemistry and gene expression analysis at 9 weeks after the Type-N operation revealed that the ischemic limb was in a steady state with impaired angiogenesis, like that observed in CLI patients. Therapeutic treatment with cilostazol, which is used for intermittent claudication, did not restore blood flow in chronic Type-N mice. In contrast, therapeutic transplantation of pericytes and vascular endothelial cells, which can form new blood vessels in vivo, significantly improved blood flow in a subset of Type-N mice. These findings suggest that this novel chronic and severe HLI model may be a valuable standard animal model for therapeutic evaluation of the angiogenic effects of CLI drug candidates.
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For patients with angiitis‐induced critical limb ischemia (AICLI), cell transplantation, such as purified CD34+ cells (PCCs) and peripheral blood mononuclear cells (PBMNCs), is gradually being used as a promising treatment. This was the first randomized single‐blinded noninferiority trial (number: NCT 02089828) specifically designed to evaluate the therapeutic efficacies of the transplantation of PCCs vs those of PBMNCs for the treatment of AICLI. We aimed to compare the mid‐term safety and efficacy between the two groups and determine their respective advantages. From April 2014 to September 2019, 50 patients with AICLI were equally allocated to the two groups, except for 1 lost patient, 1 amputee, and 1 patient who died of heart disease. The other 47 patients completed the 36‐month follow‐up. The endpoints were as follows: major amputation‐free survival and total amputation‐free survival at 6 months, which were 96.0% and 84.0% in the PBMNCs group and 96.0% and 72.0% in the PCCs group, respectively. These rates remained stable at 12, 24, and 36 months. The PCCs group had a significant higher probability of rest pain relief than the PBMNCs group, whereas earlier significant improvements in the Rutherford classification were observed in the PBMNCs group. Accordingly, PCCs would be preferred for patients with significant pain, whereas PBMNCs may be a good option for patients with two or more critically ischemic limbs. Concerning cost‐effectiveness, PCCs are not more cost‐effective than PBMNCs. These outcomes require verification from long‐term trials involving larger numbers of patients. The two therapies demonstrated similar mid‐term safety and efficacy, while each cell therapy had its unique advantages and is recommended for certain conditions: for example, peripheral blood mononuclear cells for patients with two or more critical ischemic limbs and purified CD34+ cells for patients with significant pain.
Preprint
Cardiovascular disease (CVD) comprises a group of heart and circulatory disorders, which are regarded as a global medical issue with high prevalence and mortality rates. Currently, vascular regenerative surgery represents the most employed therapeutic option to treat ischemic disorders, even though not all the patients are amenable to surgical revascularization. Therefore, more efficient therapeutic approaches are urgently required to promote neovascularization. Therapeutic angiogenesis represents an emerging strategy that aims at reconstructing the damaged vascular network by stimulating local angiogenesis and/or promoting de novo blood vessel formation according to a process known as vasculogenesis. Circulating endothelial colony forming cells (ECFCs), in turn, represent truly endothelial precursors able to aggregate into bidimensional tube networks and to originate patent vessels. Accordingly, ECFCs provide the most rationale and promising cellular candidate for therapeutic purposes. The current review provides a brief outline on the origin and characterization of ECFCs and a summary of the progress in preclinical studies aiming at assessing their efficacy in a variety of ischemic disorders, including AMI, PAD, ischemic brain disease and retinopathy. We also describe how to enhance the vasoreparative potential of ECFCs by boosting specific pro-angiogenic signalling pathways either pharmacologically or through gene manipulation. Taken together, these observations suggest that ECFCs represent a useful strategy to treat ischemic diseases.
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Chronic wounds are a major complication in patients with cardiovascular diseases. Cell therapies have shown potential to stimulate wound healing, but clinical trials using adult stem cells have been tempered by limited numbers of cells and invasive procurement procedures. Induced pluripotent stem cells (IPSCs) have several advantages of other cell types, for example they can be generated in abundance from patients' somatic cells (autologous) or those from a matched donor. IPSCs can be efficiently differentiated to functional endothelial cells (IPSC-ECs). Here, we used a murine excisional wound model to test the pro-angiogenic properties of iPSC-ECs in wound healing. Two full-thickness wounds were made on the dorsum of NOD-SCID mice and splinted. IPSC-ECs (5x105) were topically applied to one wound, with the other serving as a control. Treatment with iPSC-ECs significantly increased wound perfusion and accelerated wound closure. Expression of endothelial cell (EC) surface marker, PECAM-1 (CD31), and pro-angiogenic EC receptor, Tie1, mRNA was upregulated in iPSC-EC treated wounds at 7 days post-wounding. Histological analysis of wound sections showed increased capillary density in iPSC-EC wounds at day 7 and day 14 post-wounding, and increased collagen content at day 14. Anti-GFP fluorescence confirmed presence of iPSC-ECs in the wounds. Bioluminescent imaging showed progressive decline of iPSC-ECs over time, suggesting that iPSC-ECs are acting primarily through short-term paracrine effects. These results highlight the pro-regenerative effects of iPSC-ECs and demonstrate that they are a promising potential therapy for intractable wounds.
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Objective Critical limb ischemia (CLI) is the most dangerous stage of peripheral artery disease (PAD). Many basic researches and clinical treatment had been focused on stem cell transplantation for CLI. This systematic review was performed to review evidence for safety and efficacy of autologous stem cell therapy in CLI. Methods A systematic literature search was performed in the SinoMed, PubMed, Embase, ClinicalTrials.gov, and Cochrane Controlled Trials Register databases from building database to January 2018. Results Meta-analysis showed that cell therapy significantly increased the probability of ulcer healing (RR = 1.73, 95% CI = 1.45–2.06), angiogenesis (RR = 5.91, 95% CI = 2.49–14.02), and reduced the amputation rates (RR = 0.59, 95% CI = 0.46–0.76). Ankle-brachial index (ABI) (MD = 0.13, 95% CI = 0.11–0.15), TcO2 (MD = 12.22, 95% CI = 5.03–19.41), and pain-free walking distance (MD = 144.84, 95% CI = 53.03–236.66) were significantly better in the cell therapy group than in the control group (P < 0.01). Conclusions The results of this meta-analysis indicate that autologous stem cell therapy is safe and effective in CLI. However, higher quality and larger RCTs are required for further investigation to support clinical application of stem cell transplantation.
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Adipose tissue-derived stem cells (ADSCs) are mesenchymal cells with the capacity for self-renewal and multipotential differentiation. This multipotentiality allows them to become adipocytes, chondrocytes, myocytes, osteoblasts and neurocytes among other cell lineages. Stem cells and, in particular, adipose tissue-derived cells, play a key role in reconstructive or tissue engineering medicine as they have already proven effective in developing new treatments. The purpose of this work is to review the applications of ADSCs in various areas of regenerative medicine, as well as some of the risks associated with treatment with ADSCs in neoplastic disease.
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Peripheral artery disease (PAD) is one of the major vascular complications in individuals suffering from diabetes and in the elderly that can progress to critical limb ischemia (CLI), portending significant burden in terms of patient morbidity and mortality. Over the last two decades, stem cell therapy (SCT) has risen as an attractive alternative to traditional surgical and/or endovascular revascularization to treat this disorder. The primary benefit of SCT is to induce therapeutic neovascularization and promote collateral vessel formation to increase blood flow in the ischemic limb and soft tissue. Existing evidence provides a solid rationale for ongoing in-depth studies aimed at advancing current SCT that may change the way PAD/CLI patients are treated.
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It is very well known that bone marrow (BM) microvasculature may possess a crucial role in the maintenance of homeostasis of BM due to mutual interactions between BM microvascular system and other physiological functions including haematopoiesis and osteogenesis. Chemotherapy and radiotherapy are known as main approaches for cancer treatment and also are known as the main cause of damage to the BM microvascular system. However, despite the importance of BM microvasculature in orchestrating various biological functions, less attention has been drawn to address the underlying mechanisms for the damage and to explore cellular and molecular mechanisms by which the recovery/regeneration of chemotherapy- and/or radiotherapy-induced BM microvascular system damage can occur. Therefore, in this review we firstly discuss the ultra-/structure and biological characteristics of BM microvascular system (sinusoids). Secondly, potential contribution of BM sinusoids is discussed in pathophysiological circumstances (bone remodelling, haematopoiesis, cancer bone metastasis, and haematological cancers). Thirdly, we address previous preclinical and clinical studies regarding chemotherapy- and irradiation-induced BM microvasculature damage. Finally, potential cellular and molecular mechanisms are discussed for the recovery/regeneration of damaged BM microvascular system, including the potential roles of endothelial progenitor cells, haematopoietic stem/progenitor cells, and stimulation of VEGF/VEGFR and Ang-1/Tie-2 signalling pathways.
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Background Critical limb ischaemia (CLI) is a severe manifestation of peripheral arterial disease, characterised by chronic ischaemic rest pain, ulcers or gangrene. Management of ischaemic pain is challenging in patients with no options for revascularisation and optimal pharmacological therapies have not been established. Objectives To identify and evaluate the effectiveness of pharmacological therapies to treat ischaemic pain secondary to non-reconstructable CLI. Methods This systematic review was reported in accordance with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guideline. Comprehensive searches of three electronic databases, a PubMed-related articles link search, grey literature search and hand-searches of the bibliographies of relevant papers and textbooks were performed. Studies recruiting adult patients with CLI of any aetiology were eligible for inclusion. Surgical and revascularisation procedures, and all invasive interventions were excluded. Results Of 792 studies, six met full inclusion criteria. These studies researched the use of intravenous lidocaine, intravenous ketamine, oral gabapentin and the combination of transdermal buprenorphine and epidural morphine/ropivacaine infusion. All studies showed an improvement in severity of ischaemic pain in CLI but with varying side effect profiles and quality. The extracted studies showed substantial heterogeneity and therefore a meta-analysis was not performed. Conclusion The pharmacological management of pain secondary to non-reconstructable CLI is a challenging review topic. No recommendations of pharmacological agents can be made following this review but a number of novel approaches to manage pain in this cohort have shown positive results and require further investigation.
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Ischemic stroke is one of the leading causes of human death and disability worldwide. So far, ultra-early thrombolytic therapy is the most effective treatment. However, most patients still live with varying degrees of neurological dysfunction due to its narrow therapeutic time window. It has been confirmed in many studies that endothelial progenitor cells (EPCs), as a kind of adult stem cells, can protect the neurovascular unit by repairing the vascular endothelium and its secretory function, which contribute to the recovery of neurological function after an ischemic stroke. This paper reviews the basic researches and clinical trials of EPCs especially in the field of ischemic stroke and addresses the combination of EPC application with new technologies, including neurovascular intervention, synthetic particles, cytokines, and EPC modification, with the aim of shedding some light on the application of EPCs in treating ischemic stroke in the future.
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Ischemic diseases, the leading cause of disability and death, are caused by the stenosis or obstruction of arterioles/capillaries that is not compensated for by vessel dilatation or collateral circulation. Angiogenesis is a complex process leading to new blood vessel formation and is triggered by ischemic conditions. Adequate angiogenesis, as a compensatory mechanism in response to ischemia, may increase oxygen and nutrient supplies to tissues and protect their function. Therapeutic angiogenesis has been the most promising therapy for treating ischemic diseases. In recent years, stem cell transplantation has been recognized as a new technique with therapeutic angiogenic effects on ischemic diseases. Adipose-derived stem cells, characterized by their ease of acquisition, high yields, proliferative growth, and low immunogenicity, are an ideal cell source. In this review, the characterization of adipose-derived stem cells and the role of angiogenesis in ischemic attack are summarized. The angiogenic effects of adipose-derived stem cells are discussed from the perspectives of in-vitro, in-vivo, and clinical trial studies for the treatment of ischemic diseases, including ischemic cardiac, cerebral, and peripheral vascular diseases and wound healing. The microvesicles/exosomes released from adipose-derived stem cells are also presented as a novel therapeutic prospect for treating ischemic diseases.
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Background Transplantation of allogeneic adipose-derived regenerative cells (ADRCs) is a promising treatment modality for severe ischemic diseases. However, minimal information is available on the in vivo effects, fate, and migration of ADRCs, as well as the mechanisms of their therapeutic angiogenesis. Materials and methods In this study, green fluorescent protein-expressing ADRCs (GFP-ADRCs) were obtained, labeled with acetylated 3-aminopropyltrimethoxysilane (APTS)-coated iron oxide nanoparticles (APTS NPs), and injected into an old apolipoprotein E knockout (ApoE-KO) mouse model with hind limb ischemia. Then, 3.0 T magnetic resonance imaging (MRI) was performed to dynamically trace the role of ADRCs targeting hind limb ischemia in the ApoE-KO mice model. Results Labeled cells were visualized as large hypointense spots in ischemic muscles by serial 3.0 T MRI scans during a 4-week follow-up. The presence of labeled GFP-ADRCs was confirmed by Prussian blue staining and fluorescence microscopy on postmortem specimens. Conclusion This study showed that allogeneic ADRCs offer great potential application for therapeutic angiogenesis in severe ischemic disease based on the efficacy and feasibility of ADRC transplantation and on the available amounts of tissue.
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Demonstrate the safety and effectiveness of highly purified CD133+ autologous stem cells in critical limb ischemia (CLI). Prospective single-center not randomized. Clinicaltrials.gov identifier: NCT01595776 Eight patients with a history of stable CLI were enrolled in a period of 2 years. After bone marrow stimulation and single leukapheresis collection, CD133+ immunomagnetic cell selection was performed. CD133+ cells in buffer phosphate suspension was administered intramuscularly. Muscular and arterial contrast enhanced ultra sound (CEUS), lesion evolution and pain management were assessed preoperatively and 3, 6 and 12 months after the implant. No patient had early or late complications related to the procedure. Two patients (25 %) didn’t get any relief from the treatment and underwent major amputation. Six patients (75 %) had a complete healing of the wounds, rest pain cessation and walking recovery. An increase in CEUS values was shown in all eight patients at 6 months and in the six clinical healed patients at 12 months and had statistical relevance. Highly purified autologous CD133+ cells can stimulate neo-angiogenesis, as based on clinical and CEUS data.
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Critical limb ischemia (CLI) represents the most advanced stage of peripheral arterial obstructive disease (PAOD) with a severe obstruction of the arteries which markedly reduces blood flow to the extremities and has progressed to the point of severe rest pain and/or even tissue loss. Recent therapeutic strategies have focused on restoring this balance in favor of tissue survival using exogenous molecular and cellular agents to promote regeneration of the vasculature. These are based on stimulation of angiogenesis by extracellular and cellular components. This review article carries out a systematic analysis of the most recent scientific literature on the application of stem cells in patients with CLI. The results obtained from the detailed analysis of the recent literature data have confirmed the beneficial role of cell therapy in reducing the rate of major amputations in patients with CLI and improving their quality of life.
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Peripheral arterial disease (PAD) continues to grow in global prevalence and consumes an increasing amount of resources in the United States health care system. Overall rates of intervention for PAD have been rising steadily in recent years. Changing demographics, evolution of technologies, and an expanding database of outcomes studies are primary forces influencing clinical decision making in PAD. The management of PAD is multidisciplinary, involving primary care physicians and vascular specialists with varying expertise in diagnostic and treatment modalities. PAD represents a broad spectrum of disease from asymptomatic through severe limb ischemia. The Society for Vascular Surgery Lower Extremity Practice Guidelines committee reviewed the evidence supporting clinical care in the treatment of asymptomatic PAD and intermittent claudication (IC). The committee made specific practice recommendations using the GRADE (Grades of Recommendation Assessment, Development and Evaluation) system. There are limited Level I data available for many of the critical questions in the field, demonstrating the urgent need for comparative effectiveness research in PAD. Emphasis is placed on risk factor modification, medical therapies, and broader use of exercise programs to improve cardiovascular health and functional performance. Screening for PAD appears of unproven benefit at present. Revascularization for IC is an appropriate therapy for selected patients with disabling symptoms, after a careful risk-benefit analysis. Treatment should be individualized based on comorbid conditions, degree of functional impairment, and anatomic factors. Invasive treatments for IC should provide predictable functional improvements with reasonable durability. A minimum threshold of a > 50% likelihood of sustained efficacy for at least 2 years is suggested as a benchmark. Anatomic patency (freedom from restenosis) is considered a prerequisite for sustained efficacy of revascularization in IC. Endovascular approaches are favored for most candidates with aortoiliac disease and for selected patients with femoropopliteal disease in whom anatomic durability is expected to meet this minimum threshold. Conversely, caution is warranted in the use of interventions for IC in anatomic settings where durability is limited (extensive calcification, small-caliber arteries, diffuse infrainguinal disease, poor runoff). Surgical bypass may be a preferred strategy in good-risk patients with these disease patterns or in those with prior endovascular failures. Common femoral artery disease should be treated surgically, and saphenous vein is the preferred conduit for infrainguinal bypass grafting. Patients who undergo invasive treatments for IC should be monitored regularly in a surveillance program to record subjective improvements, assess risk factors, optimize compliance with cardioprotective medications, and monitor hemodynamic and patency status. Copyright © 2015 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.
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Wound healing is a complex process that involves interaction of soluble mediators, extracellular matrix and infiltrating blood cells. Chronic and non-healing skin defects contribute significantly to morbidity and mortality of many patients. Recently, despite the current medical progress, the chronic and non-healing wounds still represent a serious medical problem. In many cases, conventional therapeutic approaches, such as dermal substitutes and growth factor therapy failed and do not produce the expected results, patients are exposed to a high risk of infection, sepsis or amputation. For that reason clinicians and researchers are forced to searching for alternative methods to induce healing process which may result into complete wound closure. Mesenchymal stem cells (MSCs) represent a unique tool of tissue engineering and regenerative medicine and a promising therapeutic strategy. Due to their unique biological properties, MSCs seem to be the perspective modality method for these patients. Many preclinical and clinical studies suggest the possibility of using these cells in tissue regeneration, healing acute and chronic wounds and scar remodelling. The objective of the present review is to summarize the current information and preclinical data about MSCs, their biological characteristics and mode of action during regenerative and healing processes, as well as their clinical application in chronic wounds treatment.
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For the treatment of critical limb ischemia, collaboration with wound specialists and cardiologists performing revascularization is important. The foot care unit affiliated with related departments opened at our hospital in July 2010 for limb salvage, mainly under the leadership of the departments of cardiovascular internal medicineand plastic surgery. We have treated 194 patients up until October 2012. The primary diseases included 81 cases (87 limbs) of foot ulcer and gangrene, with complications of peripheral arterial diseases (PADs) in all cases. Intravascular treatment was conducted for 69 limbs with PAD complications, and the initial success rate was 85.5%, of which surgical debridement or minor amputation was performed on 32 limbs. Regarding open wounds following operation and chronic ulcer, platelet-rich plasma therapy was conducted in 29 limbs and negative pressure wound therapy in 15 limbs. Among all of the patients treated, 58 limbs healed, 10 cases died, and the others are currently receiving ongoing treatment. Cardiovascular internal medicine specialists and plastic surgeons examine patients together at the outpatient clinic and prepare and implement a multidisciplinary treatment plan including vascular reconstructions and operation. We cooperate with physicians in each related department and efforts in team medicine have been made for the purpose of limb salvage.
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Stem cells have been successfully employed for the treatment of critical limb ischemia (CLI). We conducted a clinical trial to determine the feasibility of using autologous adipose-derived MSCs (AdMSCs) for the treatment of CLI. Unexpectedly, two diabetic patients developed peripheral microthrombosis. This adverse effect, which contrasts with the reported anti-thrombotic properties of MSCs, may stem from the diabetic environment that alters the fibrinolitic activity of AdMSCs thereby increasing the probability of developing thrombosis. Herein, we confirm this premise by demonstrating that diabetic AdMSCs cultured in the presence of blood sera expressed and released higher levels of plasminogen activator inhibitor type 1 (PAI-1), reduced levels of tissue plasminogen activator (tPA) and lower D-dimer formation as compared to non-diabetic AdMSCs. Thus to establish an appropriate cell therapy for diabetic patients, we recommend including new preclinical safety tests such as the D-dimer and/or tPA/PAI-1 ratio tests in order to assess fibrinolytic activity of cells prior to implantation.
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Obesity is associated with a higher risk of developing cancer and co-morbidities that are part of the metabolic syndrome. Adipose tissue is recognized as an endocrine organ, as it affects a number of physiological functions, and contains adipose tissue-derived stem cells (ASCs). ASCs can differentiate into cells of multiple lineages, and as such are applicable to tissue engineering and regenerative medicine. Yet the question of whether ASC functionality is affected by the donor's body mass index (BMI) still exists. ASCs were isolated from patients having different BMIs (BMI-ASCs), within the ranges of 18.5-32.8. It was hypothesized that overweight BMI-ASCs would be more compromised in early adipogenic and osteogenic potential, and ability to form colonies in vitro. BMI was inversely correlated with ASC proliferation and colony forming potential as assessed by CyQUANT proliferation assay (fluorescence- based measurement of cellular DNA content), and colony forming assays. BMI was positively correlated with early time point (day 7) but not later time point (day 15) intracytoplasmic lipid accumulation as assessed by Oil-Red-O staining. Alizarin red staining and RT-PCR for alkaline phosphatase demonstrated that elevated BMI resulted in compromised ASC mineralization of extracellular matrix and decreased alkaline phosphatase mRNA expression. These data demonstrate that elevated BMI resulted in reduced ASC proliferation, and potentially compromised osteogenic capacity in vitro; thus BMI is an important criterion to consider in selecting ASC donors for clinical applications.
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Background: Peripheral vascular disease of the lower extremities comprises a clinical spectrum that extends from no symptoms to presentation with critical limb ischemia (CLI). Bone marrow derived Mesenchymal Stem Cells (BM- MSCs) may ameliorate the consequences of CLI due to their combinatorial potential for inducing angiogenesis and immunomodulatory environment in situ. The primary objective was to determine the safety of BM- MSCs in patients with CLI. Methods: Prospective, double blind randomized placebo controlled multi-center study was conducted in patients with established CLI as per Rutherford classification in category II-4, III-5, or III-6 with infra-inguinal arterial occlusive disease and were not suitable for or had failed revascularization treatment. The primary end point was incidence of treatment - related adverse events (AE). Exploratory efficacy end points were improvement in rest pain, increase in Ankle Brachial Pressure Index (ABPI), ankle pressure, healing of ulcers, and amputation rates. Twenty patients (BM-MSC: Placebo = 1:1) were administered with allogeneic BM-MSCs at a dose of 2 million cells/kg or placebo (PlasmaLyte A) at the gastrocnemius muscle of the ischemic limb. Results: Improvement was observed in the rest pain scores in both the arms. Significant increase in ABPI and ankle pressure was seen in BM-MSC arm compared to the placebo group. Incidence of AEs in the BM-MSC arm was 13 vs. 45 in the placebo arm where as serious adverse events (SAE) were similar in both the arms (5 in BM-MSC and 4 in the placebo group). SAEs resulted in death, infected gangrene, amputations in these patients. It was observed that the SAEs were related to disease progression and not related to stem cells. Conclusion: BM-MSCs are safe when injected IM at a dose of 2 million cells/kg body weight. Few efficacy parameters such as ABPI and ankle pressure showed positive trend warranting further studies. Trial registration: NIH website (http://www.clinicaltrials.gov/ct2/show/NCT00883870).
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Cancer chemotherapy can cause significant damage to the bone marrow (BM) microvascular (sinusoidal) system. Investigations must now address whether and how BM sinusoidal endothelial cells (SECs) can be protected during chemotherapy. Herein we examined the potential protective effects of genistein, a soy‐derived flavonoid, against BM sinusoidal damage caused by treatment with methotrexate (MTX). The groups of young adult rats were gavaged daily with genistein (20 mg/kg) or placebo. After 1 week, rats also received daily injections of MTX (0.75 mg/kg) or saline for 5 days and were killed after a further 4 days. Histological analyses showed that BM sinusoids were markedly dilated ( p < 0.001) in the MTX‐alone group but were unaffected or less dilated in the genistein+MTX group. In control rats, genistein significantly enhanced expression of vascular endothelial growth factor (VEGF; p < 0.01), particularly in osteoblasts, and angiogenesis marker CD31 ( p < 0.001) in bone. In MTX‐treated rats, genistein suppressed MTX‐induced apoptosis of BM SECs ( p < 0.001 vs MTX alone group) and tended to increase expression of CD31 and VEGF ( p < 0.05). Our in vitro studies showed that genistein in certain concentrations protected cultured SECs from MTX cytotoxic effects. Genistein enhanced tube formation of cultured SECs, which is associated with its ability to induce expression of endothelial nitric oxide synthase and production of nitric oxide. These data suggest that genistein can protect BM sinusoids during MTX therapy, which is associated, at least partially, with its indirect effect of promoting VEGF expression in osteoblasts and its direct effect of enhancing nitric oxide production in SECs.
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Wound healing is a complex but a fine‐tuned biological process in which human skin has the ability to regenerate itself following damage. However, in particular conditions such as deep burn or diabetes the process of wound healing is compromised. Despite investigations on the potency of a wide variety of stem cells for wound healing, adipose‐derived stem cells (ASCs) seem to possess the least limitations for clinical applications, and literature showed that ASCs can improve the process of wound healing very likely by promoting angiogenesis and/or vascularisation, modulating immune response, and inducing epithelialization in the wound. In the present review, advantages and disadvantages of various stem cells which can be used for promoting wound healing are discussed. In addition, potential mechanisms of action by which ASCs may accelerate wound healing are summarised. Finally, clinical studies applying ASCs for wound healing and the associated limitations are reviewed.
Article
Chemotherapeutic agents are very well evident extrinsic stimuli for causing damage to endothelial cells. Methotrexate is an antimetabolite commonly used to treat solid tumours and paediatric cancers. However, studies on the effect(s) of methotrexate on bone marrow microvascular system are inadequate. In the current study, we observed a significant bone marrow microvascular dilation following methotrexate therapy in rats, accompanied by apoptosis induction in bone marrow sinusoidal endothelial cells, and followed by recovery of bone marrow sinusoids associated with increased proliferation of remaining bone marrow sinusoidal endothelial cells. Our in vitro studies revealed that methotrexate is cytotoxic for cultured sinusoidal endothelial cells and can also induce apoptosis which is associated with upregulation of expression ratio of Bax and Bcl‐2 genes and Bax/Bcl‐2 expression ratio. Furthermore, it was shown that methotrexate can negatively affect proliferation of cultured sinusoidal endothelial cells and also inhibit their abilities of migration and formation of microvessel like tubes. The data from this study indicates that methotrexate can cause significant bone marrow sinusoidal endothelium damage in vivo and induce apoptosis and inhibit proliferation, migration and tube‐forming abilities of sinusoidal endothelial cells in vitro.
Article
Background: Peripheral arterial occlusive disease (PAOD) is a common cause of morbidity and mortality due to cardiovascular disease in the general population. Although numerous treatments have been adopted for patients at different disease stages, no option other than amputation is available for patients presenting with critical limb ischaemia (CLI) unsuitable for rescue or reconstructive intervention. In this regard, prostanoids have been proposed as a therapeutic alternative, with the aim of increasing blood supply to the limb with occluded arteries through their vasodilatory, antithrombotic, and anti-inflammatory effects. This is an update of a review first published in 2010. Objectives: To determine the effectiveness and safety of prostanoids in patients with CLI unsuitable for rescue or reconstructive intervention. Search methods: For this update, the Cochrane Vascular Information Specialist searched the Specialised Register (January 2017) and the Cochrane Central Register of Controlled Trials (CENTRAL; 2017, Issue 1). In addition, we searched trials registries (January 2017) and contacted pharmaceutical manufacturers, in our efforts to identify unpublished data and ongoing trials. Selection criteria: Randomised controlled trials describing the efficacy and safety of prostanoids compared with placebo or other pharmacological control treatments for patients presenting with CLI without chance of rescue or reconstructive intervention. Data collection and analysis: Two review authors independently selected trials, assessed trials for eligibility and methodological quality, and extracted data. We resolved disagreements by consensus or by consultation with a third review author. Main results: For this update, 15 additional studies fulfilled selection criteria. We included in this review 33 randomised controlled trials with 4477 participants; 21 compared different prostanoids versus placebo, seven compared prostanoids versus other agents, and five conducted head-to-head comparisons using two different prostanoids.We found low-quality evidence that suggests no clear difference in the incidence of cardiovascular mortality between patients receiving prostanoids and those given placebo (risk ratio (RR) 0.81, 95% confidence interval (CI) 0.41 to 1.58). We found high-quality evidence showing that prostanoids have no effect on the incidence of total amputations when compared with placebo (RR 0.97, 95% CI 0.86 to 1.09). Adverse events were more frequent with prostanoids than with placebo (RR 2.11, 95% CI 1.79 to 2.50; moderate-quality evidence). The most commonly reported adverse events were headache, nausea, vomiting, diarrhoea, flushing, and hypotension. We found moderate-quality evidence showing that prostanoids reduced rest-pain (RR 1.30, 95% CI 1.06 to 1.59) and promoted ulcer healing (RR 1.24, 95% CI 1.04 to 1.48) when compared with placebo, although these small beneficial effects were diluted when we performed a sensitivity analysis that excluded studies at high risk of bias. Additionally, we found evidence of low to very low quality suggesting the effects of prostanoids versus other active agents or versus other prostanoids because studies conducting these comparisons were few and we judged them to be at high risk of bias. None of the included studies assessed quality of life. Authors' conclusions: We found high-quality evidence showing that prostanoids have no effect on the incidence of total amputations when compared against placebo. Moderate-quality evidence showed small beneficial effects of prostanoids for rest-pain relief and ulcer healing when compared with placebo. Additionally, moderate-quality evidence showed a greater incidence of adverse effects with the use of prostanoids, and low-quality evidence suggests that prostanoids have no effect on cardiovascular mortality when compared with placebo. None of the included studies reported quality of life measurements. The balance between benefits and harms associated with use of prostanoids in patients with critical limb ischaemia with no chance of reconstructive intervention is uncertain; therefore careful assessment of therapeutic alternatives should be considered. Main reasons for downgrading the quality of evidence were high risk of attrition bias and imprecision of effect estimates.
Article
Chronic critical limb ischemia (CLI) represents an end-stage manifestation of peripheral arterial disease (PAD). CLI patients are at very high risk of amputation and cardiovascular complications, leading to severe morbidity and mortality. Because many patients with CLI are ineligible for conventional revascularization procedures, it is urgently needed to explore alternative strategies to improve blood supply in the ischemic tissue. Although researchers initially focused on gene/protein therapy using proangiogenic growth factors/cytokines, recent discovery of somatic stem/progenitor cells including bone marrow (BM)-derived endothelial progenitor cells (EPCs) and mesenchymal stem cells (MSCs) has drastically developed the field of therapeutic angiogenesis for CLI. Overall, early phase clinical trials demonstrated that stem/progenitor cell therapies may be safe, feasible and potentially effective. However, only few late-phase clinical trials have been conducted. This review provides an overview of the preclinical and clinical reports to demonstrate the usefulness and the current limitations of the cell-based therapies.
Chapter
Peripheral arterial disease (PAD) is caused by atherosclerosis that results in narrowing and frequently complete occlusions of one or more arteries that supply the lower extremities. PAD affects ~8.5 million Americans at or over the age of 40 (Go et al., Circulation 129:e28–e292, 2014). The two major clinical manifestations of PAD are intermittent claudication (IC) and critical limb ischemia (CLI). Intermittent claudication is defined by the presence of leg pain/cramping with walking that relieves with rest. CLI is defined as pain present at rest, with or without ischemic ulcers or gangrene, classified as Rutherford-Becker Class 4–6 or Fontaine Class III and IV. Patients with CLI are quite different than those with IC. The 1-year mortality rate in patients with CLI is approximately 25 %, and the overall amputation rate over 1 year is approximately 30 % (Norgren et al., J Vasc Surg 45:S5–67, 2007). While medical therapies to limit complications from atherosclerosis reduce general cardiovascular mortality in patients with CLI, at present there is no definitive medical therapy for CLI. Newer medications such as Praxilene (a metabolic enhancer and a 5-HT2 receptor antagonist) and Alprostadil (a prostaglandin E1 analogue) have been recently approved for use in Europe in patients with PAD to improve blood flow to the ischemic limb. However, mixed results from the clinic studies indicate that these drugs need further long-term evaluation to establish their role in PAD.
Article
The number of individuals with chronic cutaneous wounds has been increasing worldwide due to an aging population, diabetes, obesity, and cardiovascular disease. In the United States, almost seven million Americans have chronic skin ulcers. Many therapeutic approaches have been used. However, the treatment outcomes are not always ideal because of failure to achieve complete wound closure in around 60% of cases, scarring, and high rate of recurrence. Therefore, there is a need for more effective therapies. Stem cells offer promising possibilities. Pre-clinical studies have shown that bone- or adipose tissue-derived mesenchymal stem cells (MSCs) have a competitive advantage over other types of stem cells due to their better defined multipotent differentiating potential, paracrine effects, immunomodulatory properties, and safety. However, large controlled clinical trials are needed to examine the capabilities of MSCs in humans and to assess their safety profile. In this review, we highlight emerging treatments in tissue regeneration and repair and provide some perspectives on how to translate current knowledge about stem cells-both multipotent and pluripotent-into viable clinical approaches for treating patients with difficult to heal wounds.
Article
In regenerative medicine, adult stem cells are the most promising cell types for cell-based therapies. As a new source for multipotent stem cells, human adipose tissue has been introduced. These so called adipose tissue-derived stem cells (ADSCs) are considered to be ideal for application in regenerative therapies. Their main advantage over mesenchymal stem cells derived from other sources, e.g. from bone marrow, is that they can be easily and repeatable harvested using minimally invasive techniques with low morbidity. ADSCs are multipotent and can differentiate into various cell types of the tri-germ lineages, including e.g. osteocytes, adipocytes, neural cells, vascular endothelial cells, cardiomyocytes, pancreatic β-cells, and hepatocytes. Interestingly, ADSCs are characterized by immunosuppressive properties and low immunogenicity. Their secretion of trophic factors enforces the therapeutic and regenerative outcome in a wide range of applications. Taken together, these particular attributes of ADSCs make them highly relevant for clinical applications. Consequently, the therapeutic potential of ADSCs is enormous. Therefore, this review will provide a brief overview of the possible therapeutic applications of ADSCs with regard to their differentiation potential into the tri-germ lineages. Moreover, the relevant advancements made in the field, regulatory aspects as well as other challenges and obstacles will be highlighted.
Article
Aims: Wound healing is deeply dependent on neovascularization to restore blood flow. The neovascularization of endothelial progenitor cells (EPCs) through paracrine secretion has been reported in various tissue repair models. Exosomes, key components of cell paracrine mechanism, have been rarely reported in wound healing. Methods: Exosomes were isolated from the media of EPCs obtained from human umbilical cord blood. Diabetic rats wound model was established and treated with exosomes. The in vitro effects of exosomes on the proliferation, migration and angiogenic tubule formation of endothelial cells were investigated. Results: We revealed that human umbilical cord blood EPCs derived exosomes transplantation could accelerate cutaneous wound healing in diabetic rats. We also showed that exosomes enhanced the proliferation, migration and tube formation of vascular endothelial cells in vitro. Furthermore, we found that endothelial cells stimulated with these exosomes would increase expression of angiogenesis-related molecules, including FGF-1, VEGFA, VEGFR-2, ANG-1, E-selectin, CXCL-16, eNOS and IL-8. Conclusion: Taken together, our findings indicated that EPCs-derived exosomes facilitate wound healing by positively modulating vascular endothelial cells function.
Article
Cell therapy represents a promising option for revascularization of ischemic tissues. However, injection of dispersed cells is not optimal to ensure precise homing into the recipient's vasculature. Implantation of cell-engineered scaffolds around the occluded artery may obviate these limitations. Here, we employed the synthetic polymer polycaprolactone for fabrication of 3D woodpile- or channel-shaped scaffolds by a computer-assisted writing system (pressure assisted micro-syringe square), followed by deposition of gelatin (GL) nanofibers by electro-spinning. Scaffolds were then cross-linked with natural (genipin, GP) or synthetic (3-glycidyloxy-propyl-trimethoxy-silane, GPTMS) agents to improve mechanical properties and durability in vivo. The composite scaffolds were next fixed by crown inserts in each well of a multi-well plate and seeded with adventitial progenitor cells (APCs, 3 cell lines in duplicate), which were isolated/expanded from human saphenous vein surgical leftovers. Cell density, alignment, proliferation and viability were assessed 1 week later. Data from in vitro assays showed channel-shaped/GPTMS-crosslinked scaffolds confer APCs with best alignment and survival/growth characteristics. Based on these results, channel-shaped/GPTMS-crosslinked scaffolds with or without APCs were implanted around the femoral artery of mice with unilateral limb ischemia. Perivascular implantation of scaffolds accelerated limb blood flow recovery, as assessed by laser Doppler or fluorescent microspheres, and increased arterial collaterals around the femoral artery and in limb muscles compared with non-implanted controls. Blood flow recovery and perivascular arteriogenesis were additionally incremented by APC-engineered scaffolds. In conclusion, perivascular application of human APC-engineered scaffolds may represent a novel option for targeted delivery of therapeutic cells in patients with critical limb ischemia.
Article
Critical limb ischemia (CLI) is a clinical syndrome of ischemic pain at rest or tissue loss, such as nonhealing ulcers or gangrene, related to peripheral artery disease. CLI has a high short-term risk of limb loss and cardiovascular events. Noninvasive or invasive angiography help determine the feasibility and approach to arterial revascularization. An endovascular-first approach is often advocated based on a lower procedural risk; however, specific patterns of disease may be best treated by open surgical revascularization. Balloon angioplasty and stenting form the backbone of endovascular techniques, with drug-eluting stents and drug-coated balloons offering low rates of repeat revascularization. Combined antegrade and retrograde approaches can increase success in long total occlusions. Below the knee, angiosome-directed angioplasty may lead to greater wound healing, but failing this, any straight-line flow into the foot is pursued. Hybrid surgical techniques such as iliac stenting and common femoral endarterectomy are commonly used to reduce operative risk. Lower extremity bypass grafting is most successful with a good quality, long, single-segment autogenous vein of at least 3.5-mm diameter. Minor amputations are often required for tissue loss as a part of the treatment strategy. Major amputations (at or above the ankle) limit functional independence, and their prevention is a key goal of CLI therapy. Medical therapy after revascularization targets risk factors for atherosclerosis and assesses wound healing and new or recurrent flow-limiting disease. The ongoing National Institutes of Health-sponsored Best Endovascular Versus Best Surgical Therapy in Patients With Critical Limb Ischemia (BEST-CLI) study is a randomized trial of the contemporary endovascular versus open surgical techniques in patients with CLI.
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BACKGROUND: In an animal model of hindlimb ischemia, the outcome of transplantation of bone marrow mesenchymal stem cells was better than that of bone marrow mononuclear cells. OBJECTIVE: To evaluate the efficacy and safety of transplantation of autologous bone marrow mesenchymal stem cell (BMSC) following amplification in vitro for treating diabetic foot. DESIGN: Randomized controlled clinical study. PARTICIPANTS: A total of 40 diabetic foot patients were enrolled at the Southwest Hospital of Third Military Medical University of Chinese PLA from October 2006 to October 2008, comprising 22 males and 18 females, aged (64.3±12.7) years. There were 8 cases of grade 2, 18 cases of grade 3, 14 cases of grade 4 according to Wagner classify. In accordance with lookup table, they were randomized to cell transplantation group (n=22) and conventional treatment group (n=18). The protocols were approved by Hospital's Ethics Committee. METHODS: In the conventional treatment group, patients were subjected to treatment of conventional glucose- control, blood pressure- control, anti-infection, anti-coagulation, nerves-nourishing, and blood vessel distension; drugs were conventionally changed in local sites; patients with gangrene received toe amputation. In the cell transplantation group, patients underwent BMSC transplantation in addition to conventional treatment. BMSC suspension was prepared by the density gradient centrifugation and adherent culture. After flow cytometry, chromosome analysis, etiology detection and cell suspension skin test, BMSC were infused into the affected leg and foot by multiple-point intramuscular injection. MAIN OUTCOME MEASURES: Therapeutic efficacy was compared between these two groups 1 month after transplantation. Adverse event and side reaction were measured. RESULTS: One month after BMSC transplantation, the symptoms of cell transplantation group were improved markedly, including severe pain, intermittent claudication, and local cool. Ankle-brachial index increased obviously. Magnetic resonance imaging of lower limb blood vessel displayed that the blood stream of lower limbs had increased, which showed significant differences compared with the conventional treatment group (P < 0.01). During three months of follow-up, no abnormal symptoms were found, and conventional determination of blood, urine and excrement showed normal results. No special changes were detected in electrocardiogram and liver and kidney function. Clotting time was normal. CONCLUSION: Transplantation of autologous BMSCs following amplification in vitro might be a simple, safe and effective method for the treatment of diabetic foot.
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Objective: Critical limb ischemia (CLI) is associated with high morbidity and mortality. Because most patients with CLI will eventually undergo some type of revascularization, the natural history of CLI is not well defined, although it is important to know when patients decide to pursue treatment. Methods: We systematically searched multiple databases for controlled and uncontrolled studies of patients with CLI who did not receive revascularization with a minimum follow-up of ≥1 year. Predefined outcomes of interest were mortality, major amputation, and wound healing. Random-effects meta-analysis was used to pool cumulative incidence across studies. Results: We identified 13 studies enrolling 1527 patients. During a median follow-up of 12 months, all-cause mortality rate was 22% (confidence interval [CI], 12%-33%) and major amputation rate was 22% (CI, 2%-42%). Worsened wound or ulcer was found at 35% (CI, 10%-62%). There was a trend toward improvement in mortality and amputation rate in studies done after 1997. The quality of evidence was low because of increased risk of bias and inconsistency. Conclusions: Mortality and major amputations are common in patients who have untreated CLI during a median follow-up of 1 year, although these outcomes have improved in recent times.
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Background Low-dose aspirin is of definite and substantial net benefit for many people who already have occlusive vascular disease. We have assessed the benefits and risks in primary prevention. Methods We undertook meta-analyses of serious vascular events (myocardial infarction, stroke, or vascular death) and major bleeds in six primary prevention trials (95000 individuals at low average risk, 660000 person-years, 3554 serious vascular events) and 16 secondary prevention trials (17000 individuals at high average risk, 43 000 person-years, 3306 serious vascular events) that compared long-term aspirin versus control. We report intention-to-treat analyses of first events during the scheduled treatment period. Findings in the primary prevention trials, aspirin allocation yielded a 12% proportional reduction in serious vascular events (0.51% aspirin vs 0.57% control per year, p=0.0001), due mainly to a reduction of about a fifth in non-fatal myocardial infarction (0.18% vs 0.23% per year, p<0.0001). The net effect on stroke was not significant (0.20% vs 0.21% per year, p=0.4: haernorrhagic stroke 0.04% vs 0.03%, p=0.05; other stroke 0.16% vs 0.18% per year, p=0.08). Vascular mortality did not differ significantly (0.19% vs 0.19% per year, p=0.7). Aspirin allocation increased major gastrointestinal and extracranial bleeds (0.10% vs 0.07% per year, p<0.0001), and the main risk factors for coronary disease were also risk factors for bleeding. In the secondary prevention trials, aspirin allocation yielded a greater absolute reduction in serious vascular events (6.7% vs 8.2% per year, p<0.0001), with a non-significant increase in haernorrhagic stroke but reductions of about a fifth in total stroke (2.08% vs 2.54% per year, p=0.002) and in coronary events (4.3% vs 5.3% per year, p<0.0001). In both primary and secondary prevention trials, the proportional reductions in the aggregate of all serious vascular events seemed similar for men and women. Interpretation In primary prevention without previous disease, aspirin is of uncertain net value as the reduction in occlusive events needs to be weighed against any increase in major bleeds. Further trials are in progress. Funding UK Medical Research Council, British Heart Foundation, Cancer Research UK, and the European Community Biomed Programme.
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Background: Many clinical trials have evaluated the benefit of long-term use of antiplatelet drugs in reducing the risk of clinical thrombotic events. Aspirin and ticlopidine have been shown to be effective, but both have potentially serious adverse effects. Clopidogrel, a new thienopyridine derivative similar to ticlopidine, is an inhibitor of platelet aggregation induced by adenosine diphosphate. Methods: CAPRIE was a randomised, blinded, international trial designed to assess the relative efficacy of clopidogrel (75 mg once daily) and aspirin (325 mg once daily) in reducing the risk of a composite outcome cluster of ischaemic stroke, myocardial infarction, or vascular death; their relative safety was also assessed. The population studied comprised subgroups of patients with atherosclerotic vascular disease manifested as either recent ischaemic stroke, recent myocardial infarction, or symptomatic peripheral arterial disease. Patients were followed for 1 to 3 years. Findings: 19,185 patients, with more than 6300 in each of the clinical subgroups, were recruited over 3 years, with a mean follow-up of 1.91 years. There were 1960 first events included in the outcome cluster on which an intention-to-treat analysis showed that patients treated with clopidogrel had an annual 5.32% risk of ischaemic stroke, myocardial infarction, or vascular death compared with 5.83% with aspirin. These rates reflect a statistically significant (p = 0.043) relative-risk reduction of 8.7% in favour of clopidogrel (95% Cl 0.3-16.5). Corresponding on-treatment analysis yielded a relative-risk reduction of 9.4%. There were no major differences in terms of safety. Reported adverse experiences in the clopidogrel and aspirin groups judged to be severe included rash (0.26% vs 0.10%), diarrhoea (0.23% vs 0.11%), upper gastrointestinal discomfort (0.97% vs 1.22%), intracranial haemorrhage (0.33% vs 0.47%), and gastrointestinal haemorrhage (0.52% vs 0.72%), respectively. There were ten (0.10%) patients in the clopidogrel group with significant reductions in neutrophils (< 1.2 x 10(9)/L) and 16 (0.17%) in the aspirin group. Interpretation: Long-term administration of clopidogrel to patients with atherosclerotic vascular disease is more effective than aspirin in reducing the combined risk of ischaemic stroke, myocardial infarction, or vascular death. The overall safety profile of clopidogrel is at least as good as that of medium-dose aspirin.
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Introduction: The use of undifferentiated cells for cell-based tissue repair and regeneration strategies represents a promising approach for chronic wound healing. Multipotent adult stem cells isolated from adipose tissue, termed adipose-derived stem cells (ASCs), appear to be an ideal population of stem cells because they are autologous, non-immunogenic, plentiful, and easily obtained. Both preclinical and clinical studies have revealed that ASCs have potential for wound healing due to the mechanisms described below. Areas covered: Both in vitro and in vivo studies demonstrated that ASCs not only differentiate into keratinocytes, fibroblasts, and endothelial cells, as evidenced by their morphology, expression of cell surface markers, and gene expression, but also secrete several soluble factors, which positively contribute to wound healing in a paracrine manner. Clinical trials have been conducted using autologous ASCs with great success. Expert opinion: There remain many concerns regarding the use of ASCs, including how these cells act as precursors of keratinocytes, fibroblasts, and endothelial cells, or as a secretion vehicle of soluble factors. Further studies are necessary to establish the optimal strategy for the treatment of chronic wounds in patients with different disease backgrounds.
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Bioengineered corneas have been designed to replace partial or the full-thickness of defective corneas, as an alternative to using donor tissues. They range from prosthetic devices that solely addr ...
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Editorial by Brindle et al Therapeutic angiogenesis is the clinical use of growth factors to enhance or promote the development of collateral blood vessels in ischaemic tissue. Progress in understanding the process of angiogenesis, the isolation of angiogenic growth factors, successful preclinical studies, and promising early results in clinical trials have created great excitement about the potential of therapeutic angiogenesis.1 Although many questions remain, therapeutic angiogenesis may be the next major advance in the treatment of ischaemic heart disease. The clinical problem Ischaemic heart disease caused 6.3 million deaths worldwide in 1990, and it remains the leading cause of morbidity and mortality in the world.2 Advances in secondary prevention, reperfusion treatment for acute myocardial infarction, and revascularisation via coronary artery bypass graft surgery and percutaneous coronary interventions have improved long term survival of patients with established coronary heart disease. With these improvements in survival, and the ageing of populations, increasing numbers of patients are left with substantial myocardial ischaemia that is not amenable to revascularisation. Despite major advances in revascularisation techniques, these patients may constitute 5-15% of patients undergoing coronary angiography.
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Recently, injectable biomaterial-based therapies for cardiovascular disease have been gaining attention, because they have shown therapeutic potential in preclinical models for myocardial infarction (MI) and peripheral artery disease (PAD). Naturally derived (e.g., alginate, hyaluronic acid, collagen, or extracellular matrix-based) or synthetic (e.g., peptide or polymer-based) materials can enhance stem cell survival and retention in vivo, prolong growth factor release from bulk hydrogel or particle constructs, and even stimulate endogenous tissue regeneration as a standalone therapy. Although there are many promising preclinical examples, the therapeutic potential of biomaterial-based products for cardiovascular disease has yet to be proved on a clinical and commercial scale. This review aims to briefly summarize the latest preclinical and clinical studies on injectable biomaterial therapies for MI and PAD. Furthermore, our overall goal is to highlight the major challenges facing translation of these therapies to the clinic (e.g., regulatory, manufacturing, and delivery), with the purpose of increasing awareness of the barriers for translating novel biomaterial therapies for MI and PAD and facilitating more rapid translation of new biomaterial technologies.
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Impaired wound healing remains a challenge to date and causes debilitating effects with tremendous suffering. Recent advances in tissue engineering approaches in the area of cell therapy have provided promising treatment options to meet the challenges of impaired skin wound healing such as diabetic foot ulcers. Over the last few years, stem cell therapy has emerged as a novel therapeutic approach for various diseases including wound repair and tissue regeneration. Several different types of stem cells have been studied in both preclinical and clinical settings such as bone marrow-derived stem cells, adipose-derived stem cells (ASCs), circulating angiogenic cells (e.g., endothelial progenitor cells), human dermal fibroblasts, and keratinocytes for wound healing. Adipose tissue is an abundant source of mesenchymal stem cells, which have shown an improved outcome in wound healing studies. ASCs are pluripotent stem cells with the ability to differentiate into different lineages and to secrete paracrine factors initiating tissue regeneration process. The abundant supply of fat tissue, ease of isolation, extensive proliferative capacities ex vivo, and their ability to secrete pro-angiogenic growth factors make them an ideal cell type to use in therapies for the treatment of nonhealing wounds. In this review, we look at the pathogenesis of chronic wounds, role of stem cells in wound healing, and more specifically look at the role of ASCs, their mechanism of action and their safety profile in wound repair and tissue regeneration.
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Non-revascularizable critical limb ischemia (CLI) is the most severe stage of peripheral arterial disease, with no therapeutic option. Extensive preclinical studies have demonstrated that adipose-derived stroma cell (ASC) transplantation strongly improves revascularization and tissue perfusion in ischemic limbs. This study, named ACellDREAM, is the first phase I trial to evaluate the feasibility and safety of intramuscular injections of autologous ASC in non-revascularizable CLI patients. Seven patients were consecutively enrolled, on the basis of the following criteria: (i) lower-limb rest pain or ulcer; (ii) ankle systolic oxygen pressure <50 or 70 mm Hg for non-diabetic and diabetic patients, respectively, or first-toe systolic oxygen pressure <30 mm Hg or 50 mm Hg for non-diabetic and diabetic patients, respectively; (iii) not suitable for revascularization. ASCs from abdominal fat were grown for 2 weeks and were then characterized. More than 200 million cells were obtained, with almost total homogeneity and no karyotype abnormality. The expressions of stemness markers Oct4 and Nanog were very low, whereas expression of telomerase was undetectable in human ASCs compared with human embryonic stem cells. ASCs (10(8)) were then intramuscularly injected into the ischemic leg of patients, with no complication, as judged by an independent committee. Trans-cutaneous oxygen pressure tended to increase in most patients. Ulcer evolution and wound healing showed improvement. These data demonstrate the feasibility and safety of autologous ASC transplantation in patients with objectively proven CLI not suitable for revascularization. The improved wound healing also supports a putative functional efficiency.
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There is a clear clinical need for cell therapies to repair or regenerate tissue lost to disease or trauma. Adipose tissue is a renewable source of stem cells, called adipose-derived stem cells (ASCs), that release important growth factors for wound healing, modulate the immune system, decrease inflammation, and home in on injured tissues. Therefore, ASCs may offer great clinical utility in regenerative therapies for afflictions such as Parkinson's disease and Alzheimer's disease, spinal cord injury, heart disease, and rheumatoid arthritis, or for replacing lost tissue from trauma or tumor removal. This article discusses the regenerative properties of ASCs that can be harnessed for clinical applications, and explores current and future challenges for ASC clinical use. Such challenges include knowledge-based deficiencies, hurdles for translating research to the clinic, and barriers to establishing a new paradigm of medical care. Clinical experience with ASCs, ASCs as a portion of the heterogeneous stromal cell population extracted enzymatically from adipose tissue, and stromal vascular fraction are also described.
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CLINICAL TRIALSFor the past 3 months, faculty and staff members at the University of Pennsylvania's Institute for Human Gene Therapy have been trying to understand why a relatively fit 18-year-old with an inherited enzyme deficiency died on 17 September, 4 days after doctors at Penn injected a genetically altered virus into his liver. Last week, they presented their data to a government advisory committee. The patient was the first in a gene therapy trial to die of the therapy itself; his death is the latest blow to a field that has been struggling to live up to the promise and hype surrounding the first gene therapy trials a decade ago.
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Critical limb ischaemia (CLI) is a severe form of peripheral arterial disease (PAD). CLI often causes disabling symptoms of pain and can lead to loss of the affected limb. It is also associated with increased risk of myocardial infarction, stroke and death from cardiovascular disease. The aims of management in patients with CLI are to relieve ischaemic pain, heal ulcers, prevent limb loss, improve function and quality of life and prolong survival. Here, current evidence regarding the medical management of CLI is reviewed. Cardiovascular risk factors should be assessed in all patients with CLI; smoking cessation and treatment of hypertension, hyperlipidaemia and diabetes all reduce the mortality rate in those with PAD. Antiplatelet agents (either aspirin or clopidogrel) are recommended to reduce both the incidence of cardiovascular events and risk of arterial occlusion. By contrast, routine use of anticoagulation (either warfarin or heparin) is not recommended. Treatment of the limbs themselves is often more challenging. Prostanoids may have some efficacy for treating rest pain and for ulcer healing, and iloprost shows favourable results in reducing the risk of major amputations, but long-term follow-up data regarding disease progression are lacking. There is insufficient evidence to support the use of naftidrofuryl or cilostazol, and pentoxifylline is not beneficial. Furthermore, there is no evidence of proven benefit of hyperbaric oxygen. A number of angiogenic growth factors have been studied in Phase I studies and randomized controlled trials (RCTs). They appear to be safe, but efficacy results have been mixed. Treatment with stem cells also shows some potential from early trials, but further larger RCTs are needed to demonstrate clear benefit. Thrombolysis may be an alternative for patients who develop acute limb ischaemia and are unsuitable for surgical intervention. However, newer endovascular techniques are likely to have a greater role in the future.