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Amniotic Fluid Stem Cells for Wound Healing

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Abstract

Amniotic fluid-derived stem (AFS) cells are an attractive cell source for applications in regenerative medicine due to their proliferation capacity, multipotency, immunomodulatory activity, and lack of significant immunogenicity. In addition, they have the ability to modulate inflammatory responses and secrete therapeutic cytokines. Because of these characteristics, AFS cells have been explored for treatments in wound healing and skin regeneration. Studies show that AFS cells are effective in accelerating wound healing in skin in fetal environments, and more recently in adult wounds. Evidence indicates that delivered cells are often transient, not permanently integrating into the final skin tissue. Instead, they secrete a portfolio of potent growth factors that are integral to skin regeneration and angiogenesis, suggesting a trophic mechanism of augmenting wound healing. These initial works of research suggest that delivery of AFS cells has potential to be an effective cell therapy for facilitating wound healing and should be further considered for clinical use in excessive skin wounds in human patients. © 2014 Springer Science+Business Media New York. All rights reserved.

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... Some interesting in vivo studies have shown promising results for 3D printing for skin regeneration. MSC and AFS cells were directly extruded within a fibrin/collagen bioink over a full thickness skin wound, which demonstrated wound closure and re-epithelization greater than that of non-cellularized bioink control [25,31,139]. ...
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Chapter
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Most burn injuries can be managed on an outpatient basis by primary care physicians. Prevention efforts can significantly lower the incidence of burns, especially in children. Burns should be managed in the same manner as any other trauma, including a primary and secondary survey. Superficial burns can be treated with topical application of lotions, honey, aloe vera, or antibiotic ointment. Partial-thickness burns should be treated with a topical antimicrobial agent or an absorptive occlusive dressing to help reduce pain, promote healing, and prevent wound desiccation. Topical silver sulfadiazine is the standard treatment; however, newer occlusive dressings can provide faster healing and are often more cost-effective. Physicians must reevaluate patients frequently after a burn injury and be aware of the indications for referral to a burn specialist.
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Wound care for partial-thickness burns should alleviate pain, decrease hospital length of stay, and be readily applied to a variety of wounds. The effectiveness of Biobrane (UDL Laboratories, Rockford, IL) is compared with that of Beta Glucan Collagen (BGC; Brennan Medical, St. Paul, MN) in a retrospective cohort study. A retrospective chart review of all children treated at a tertiary care pediatric hospital between 2003 and 2009 identified patients with partial-thickness burns treated with Biobrane. These patients were compared with historical controls treated with BGC. A total of 235 children between the ages of 4 weeks and 18 years with an average of 6.0% body surface area partial-thickness burns were treated with Biobrane. In a multivariate statistical analysis, patients treated with Biobrane healed significantly faster than those treated with BGC (Biobrane vs BGC: median, 9 vs 13 days; P = .019; hazard ratio, 1.68). In addition, patients who required inpatient treatment trended toward having shorter length of hospital stay in the Biobrane group (2.6 vs 4.1 days, P = .079). Partial-thickness burn care consists of early debridement and application of a burn wound dressing. Biobrane dressings result in faster healing compared with BGC and may decrease hospital length of stay for patients requiring inpatient admission.
Article
In the treatment of superficial partial-thickness burns, various skin substitutes and temporary dressings offer potential advantages over traditional treatments. Nonetheless, the search for an ideal temporary skin substitute or biosynthetic wound dressing is still a continuous quest. This research aimed to provide objective data on the long-term outcome of Biobrane(®) and Suprathel(®). Eight months after the initial burn treatment of Biobrane(®) and Suprathel(®), skin elasticity was measured objectively using a Cutometer(®) and the scarring process was quantified using the Vancouver Scar Scale (VSS). The median healing time for patients treated with Biobrane(®) was up to 1.8 days shorter then the Suprathel(®) group. Regarding the Vancouver Scar Scale (VSS), neither the single parameter, nor the total score were significantly different in both groups. In comparison, the Biobrane(®) group demonstrated superior Cutometer(®) parameters in regards to maximal extension, elasticity, retraction and pliability. Despite higher levels of Biobrane(®) group, the differences in the viscoelastic analysis of both substitutes did not vary significantly. Using both substitutes, we observed satisfying results in superficial partial-thickness burn treatment, without any significant differences. Since the treatment of burned patients is associated with high socioeconomic load, the cost factor should be one of the most important criteria in dermal substitute selection.
Article
Globally in 2004, the incidence of burns severe enough to require medical attention was nearly 11 million people and ranked fourth in all injuries, higher than the combined incidence of tuberculosis and HIV infections. Fortunately, although burns and fires account for over 300,000 deaths each year throughout the world, the vast majority of burns are not fatal. Nonetheless, fire-related burns are also among the leading causes of disability-adjusted life years (DALYs) lost in low- and middle-income countries (LMIC). Morbidity and mortality due to fire and flames has declined worldwide in the past decades. However, 90% of burn deaths occur in LMIC, where prevention programs are uncommon and the quality of acute care is inconsistent. Even in high-income countries, burns occur disproportionately to racial and ethnic minorities such that socioeconomic status--more than cultural or educational factors--account for most of the increased burn susceptibility. Risk factors for burns include those related to socioeconomic status, race and ethnicity, age, and gender, as well as those factors pertaining to region of residence, intent of injury, and comorbidity. Both the epidemiology and risk factors of burns injuries worldwide are reviewed in this paper.
Article
Most urgent health problems are related to a blood vessel formation failure. The use of stem cells from different sources or species for both in vitro and in vivo engineering of endothelium does not necessarily imply their direct commitment towards a vascular phenotype. In the present study, we used human amniotic fluid stem cells (AFSC) to evoke a strong angiogenic response in murine recipients, in terms of host guided-regeneration of new vessels, and we demonstrated that the AFSC secretome is responsible for the vascularising properties of these cells. We indentified in AFSC conditioned media (ACM) pro-angiogenic soluble factors, such as MCP-1, IL-8, SDF-1, VEGF. Our in vitro results suggest that ACM are cytoprotective, pro-differentiative and chemoattractive for endothelial cells. We also tested ACM on a pre-clinical model of hind-limb ischemic mouse, concluding that ACM contain mediators that promote the neo-arteriogenesis, as remodelling of pre-existing collateral arteries to conductance vessels, thus preventing the capillary loss and the tissue necrosis of distal muscles. In line with the current regenerative medicine trend, in the present study we assert the concept that stem cell-secreted mediators can guide the tissue repair by stimulating or recruiting host reparative cells.
Article
Fetuses and adults follow different repair strategies for the healing of skin wounds. Experimental evidence indicates that this most probably reflects the intrinsic characteristics of fetal tissue, although environmental factors may also contribute to this phenomenon. Accordingly, the aim of the present study was to investigate the effect of the in utero environment, i.e., amniotic fluid, on one of the major parameters of wound healing, namely cell proliferation, and especially its effect on cultures of both human fetal and adult skin fibroblasts. We found that second trimester human amniotic fluid is a potent stimulant of DNA synthesis and proliferation of cells from both developmental stages. This effect is due to the presence of growth factors, especially basic fibroblast growth factor and platelet-derived growth factor, because inhibitors of their respective receptor kinases and specific neutralizing antibodies can significantly inhibit cell proliferation. Furthermore, we found that this mitogenic effect is mediated through the activation of the MEK/ERK and the PI3K/Akt signaling pathways. Interestingly, we have not observed any significant differences between fetal and adult fibroblasts in their response to amniotic fluid, indicating that cells from both developmental stages respond equally to this complex mixture of regulatory molecules.
Article
Bioprinting consists of automated deposition of cells and biomaterials to mimic the architecture of a tissue. Gold nanoparticles act as dynamic, multivalent crosslinkers for thiol-modified hyaluronic acid and gelatin. The resulting synthetic extracellular matrix can be bioprinted into tubular constructs that support cell proliferation and matrix remodeling. The figure shows a view of a tissue construct (containing a fluorescent dye) in the x-y plane, and the inset shows the print head used.
Article
Stem cell therapy for damaged cardiac tissue is currently limited by a number of factors, including inability to obtain sufficient cell numbers, the potential tumorigenicity of certain types of stem cells and the possible link between stem cell therapy and the development of malignant arrhythmias. In this study, we investigated whether human amniotic fluid-derived stem (hAFS) cells could be a potential source of cells for cardiac cell therapy, by testing the in vitro differentiation capabilities. Undifferentiated hAFS cells express several cardiac genes, including the transcription factor mef2, the gap junction connexin43, and H- and N-cadherin. A 24 h incubation with 5-aza-2'-deoxycytidine (5-AZA-dC) induced hAFS cell differentiation along the cardiac lineage. Evidence for this differentiation included morphological changes, upregulation of cardiac-specific genes (cardiac troponin I and cardiac troponin T) and redistribution of connexin43, as well as downregulation of the stem cell marker SRY-box 2 (sox2). When co-cultured with neonatal rat cardiomyocytes (NRCs), hAFS cells formed both mechanical and electrical connections with the NRCs. Dye transfer experiments showed that calcein dye could be transferred from NRCs to hAFS cells through cellular connections. The gap junction connexin43 likely involved in the communication between the two cell types, because 12-O-tetradecanoylphorbol 13-acetate (TPA) could partially block cellular crosstalk. We conclude that hAFS cells can be differentiated into a cardiomyocyte-like phenotype and can establish functional communication with NRCs. Thus, hAFS cells may potentially be used for cardiac cell therapy.
Article
Bioprinting enables deposition of cells and biomaterials into spatial orientations and complexities that mirror physiologically relevant geometries. To facilitate the development of bioartificial vessel-like grafts, two four-armed polyethylene glycol (PEG) derivatives with different PEG chain lengths, TetraPEG8 and TetraPEG13, were synthesized from tetrahedral pentaerythritol derivatives. The TetraPEGs are unique multi-armed PEGs with a compact and symmetrical core. The TetraPEGs were converted to tetra-acrylate derivatives (TetraPAcs) which were used in turn to co-crosslink thiolated hyaluronic acid and gelatin derivatives into extrudable hydrogels for printing tissue constructs. First, the hydrogels produced by TetraPAc crosslinking showed significantly higher shear storage moduli when compared to PEG diacrylate (PEGDA)-crosslinked synthetic extracellular matrices (sECMs) of similar composition. These stiffer hydrogels have rheological properties more suited to bioprinting high-density cell suspensions. Second, TetraPAc-crosslinked sECMs were equivalent or superior to PEGDA-crosslinked gels in supporting cell growth and proliferation. Third, the TetraPac sECMs were employed in a proof-of-concept experiment by encapsulation of NIH 3T3 cells in sausage-like hydrogel macrofilaments. These macrofilaments were then printed into tubular tissue constructs by layer-by-layer deposition using the Fab@Home printing system. LIVE/DEAD viability/cytotoxicity-stained cross-sectional images showed the bioprinted cell structures to be viable in culture for up to 4 weeks with little evidence of cell death. Thus, biofabrication of cell suspensions in TetraPAc sECMs demonstrates the feasibility of building bioartificial blood vessel-like constructs for research and potentially clinical uses.
Article
The objective of this study was to evaluate persons who have survived severe burns and to describe the long-term residual problems relating to the skin. This is a cross-sectional descriptive study that included a one-time evaluation of 98 burn survivors (18 years old or older) who survived >or=30% TBSA burns, were >or=3 years postinjury, and consented to participate. Study participants were required to undergo a physical examination conducted by the Physical Medicine and Rehabilitation physicians in addition to completing study questionnaires. Participants were predominantly male (63%) and Caucasian (69%). The average time from injury was 17 years (range 3-53 years), and the average TBSA burn was 57% (range 30-97%). Problems with hot and cold temperature, sensory loss, raised scars, and itching continued to pose problems many years after burn injury. Reports of open wounds, skin rash, painful scars, and shooting pain in scars tended to decrease over time, whereas reports of fragile burns, including cuts and tears, tended to increase over time. Findings from the physical examination of the participants include hypertrophic scars in grafted areas (92%) and in nongrafted areas (38%), decreased sensation to pin in grafted areas (71%), hyperpigmentation in grafted areas (53%), fingernail deformities (35%), and skin breakdown (32%). Individuals with large burns deserve more long-term attention. As survivors of large burns continue to face significant burn-related issues, there is a critical need for long-term follow-up both in the clinic and in research.
Article
We have used in vitro scratch assays to examine the relative contribution of dermal fibroblasts and keratinocytes in the wound repair process and to test the influence of mesenchymal stem cell (MSC) secreted factors on both skin cell types. Scratch assays were established using single cell and co-cultures of L929 fibroblasts and HaCaT keratinocytes, with wound closure monitored via time-lapse microscopy. Both in serum supplemented and serum free conditions, wound closure was faster in L929 fibroblast than HaCaT keratinocyte scratch assays, and in co-culture the L929 fibroblasts lead the way in closing the scratches. MSC-CM generated under serum free conditions significantly enhanced the wound closure rate of both skin cell types separately and in co-culture, whereas conditioned medium from L929 or HaCaT cultures had no significant effect. This enhancement of wound closure in the presence of MSC-CM was due to accelerated cell migration rather than increased cell proliferation. A number of wound healing mediators were identified in MSC-CM, including TGF-beta1, the chemokines IL-6, IL-8, MCP-1 and RANTES, and collagen type I, fibronectin, SPARC and IGFBP-7. This study suggests that the trophic activity of MSC may play a role in skin wound closure by affecting both dermal fibroblast and keratinocyte migration, along with a contribution to the formation of extracellular matrix.
Article
ABSTRACT In the United States, chronic wounds affect 6.5 million patients. An estimated excess of US$25 billion is spent annually on treatment of chronic wounds and the burden is rapidly growing due to increasing health care costs, an aging population and a sharp rise in the incidence of diabetes and obesity worldwide. The annual wound care products market is projected to reach $15.3 billion by 2010. Chronic wounds are rarely seen in individuals who are otherwise healthy. In fact, chronic wound patients frequently suffer from "highly branded" diseases such as diabetes and obesity. This seems to have overshadowed the significance of wounds per se as a major health problem. For example, NIH's Research Portfolio Online Reporting Tool (RePORT; http://report.nih.gov/), directed at providing access to estimates of funding for various disease conditions does list several rare diseases but does not list wounds. Forty million inpatient surgical procedures were performed in the United States in 2000, followed closely by 31.5 million outpatient surgeries. The need for post-surgical wound care is sharply on the rise. Emergency wound care in an acute setting has major significance not only in a war setting but also in homeland preparedness against natural disasters as well as against terrorism attacks. An additional burden of wound healing is the problem of skin scarring, a $12 billion annual market. The immense economic and social impact of wounds in our society calls for allocation of a higher level of attention and resources to understand biological mechanisms underlying cutaneous wound complications.
Article
The goal of this concise review is to provide an overview of some of the most important resuscitation and monitoring issues and approaches that are unique to burn patients compared with the general intensive care unit population. Consensus conference findings, clinical trials, and expert medical opinion regarding care of the critically burned patient were gathered and reviewed. Studies focusing on burn shock, resuscitation goals, monitoring tools, and current recommendations for initial burn care were examined. The critically burned patient differs from other critically ill patients in many ways, the most important being the necessity of a team approach to patient care. The burn patient is best cared for in a dedicated burn center where resuscitation and monitoring concentrate on the pathophysiology of burns, inhalation injury, and edema formation. Early operative intervention and wound closure, metabolic interventions, early enteral nutrition, and intensive glucose control have led to continued improvements in outcome. Prevention of complications such as hypothermia and compartment syndromes is part of burn critical care. The myriad areas where standards and guidelines are currently determined only by expert opinion will become driven by level 1 data only by continued research into the critical care of the burn patient.
Article
Recent evidence shows that amniotic fluid (AF) contains multiple cell types derived from the developing fetus, and may represent a novel source of stem cells for cell therapy. In this study, we examined the paracrine factors released by human amniotic fluid-derived mesenchymal stem cells (AF-MSCs) and their ability to accelerate the wound-healing process by stimulating proliferation and migration of dermal fibroblasts. AF-MSCs expressed the typical MSC marker proteins CD13, CD29, and CD44 and differentiated into adipocytes, osteoblasts, and chondrocytes when exposed to the appropriate differentiation media. In addition, AF-MSC-conditioned media (AF-MSC-CM) significantly enhanced proliferation of dermal fibroblasts. Antibody-based protein array and enzyme-linked immunosorbent assay (ELISA) indicated that AF-MSC-CM contains various cytokines and chemokines that are known to be important in normal wound healing, including IL-8, IL-6, TGF-beta, TNFRI, VEGF, and EGF. Application of AF-MSC-CM significantly enhanced wound healing by dermal fibroblasts via the TGF-beta/SMAD2 pathway. Levels of p-SMAD2 were increased by AF-MSC-CM, and both the increase in p-SMAD2 and migration of dermal fibroblasts were blocked by inhibiting the TGF-beta/SMAD2 pathway. Moreover, in a mouse excisional wound model, AF-MSC-CM accelerated wound healing. These data provide the first evidence of the potential for AF-MSC-CM in the treatment of skin wounds.
Article
This is a randomized factorial design clinical trial that investigates the efficacy and feasibility of providing prognostic information on wound healing. Prognostic information was provided based on baseline or 4-week wound characteristics. Healing rates were then determined at 24 weeks for venous leg ulcers and 20 weeks for diabetic neuropathic foot ulcers. Centers that had access to baseline information for venous leg ulcer prognosis had an odds ratio (OR) of healing of 1.42 (95% confidence interval [CI]: 1.03, 1.95) while centers that had access to information at 4 weeks had an OR of healing of 1.43 (95% CI: 1.05, 1.95) compared with controls. Diabetic neuropathic foot ulcer patients treated in centers that had been randomized to receive only 4-week prognostic information were more likely to heal than individuals seen in centers randomized to receive no intervention (OR 1.50, 95% CI: 1.05, 2.14). Our study found that it is feasible and efficacious to provide prognostic information on venous leg ulcers and diabetic neuropathic foot ulcers in a wound care setting using an existing administrative database. This intervention was easy to administer and likely had low associated costs. This method of dispersing prognostic information to healthcare providers should be expanded to include recently published treatment algorithms.
Article
This report describes ambulatory care visits made to physician offices in the United States. Statistics are presented on selected characteristics of the physician's practice, the patient, and the visit. The data presented in this report were collected in the 2006 National Ambulatory Medical Care Survey (NAMCS), a national probability sample survey of visits to nonfederal office-based physicians in the United States. Sample data are weighted to produce annual national estimates of physician visits. During 2006, an estimated 902 million visits were made to physician offices in the United States, an overall rate of 306.6 visits per 100 persons. In over one-quarter of office visits, electronic medical records were utilized by physicians, while at 85.5 percent of visits, claims were submitted electronically. Since 1996, the percentage of visits by adults 18 years and over with chronic diabetes increased 40%, and during the same time period, visits increased for chronic hypertension (28%), and depression (27%). Among visits by females, a Pap test was ordered or provided more frequently than a human papilloma virus DNA test (5.6 versus 0.6 percent). Private insurance visits were more likely to include liquid-based Pap tests (6.3 percent) compared with visits using conventional or unspecified tests (3.7 percent), whereas visits utilizing Medicaid and other sources of payment were equally likely to provide conventional or unspecified, and liquid-based Pap tests. Medication therapy was reported at 636.7 million office visits, accounting for 70.6 percent of all office visits. In 2006, there were about 1.9 billion drugs mentioned, resulting in an overall 210.3 drug mentions per 100 visits. Visits to primary care physicians at community health centers were more likely to document health education compared with office-based practices, whereas diagnostic or screening services, drug mentions, and any nonmedication treatment occurred at approximately the same proportion of visits for primary care providers in both type of settings.
Article
The practice of in vitro three-dimensional (3-D) cell culture has lagged behind the realization that classical two-dimensional (2-D) culture on plastic surfaces fails to mirror normal cell biology. Biologically, a complex network of proteins and proteoglycans that constitute the extracellular matrix (ECM) surrounds every cell. To recapitulate the normal cellular behavior, scaffolds (ECM analogs) that reconstitute the essential biological cues are required. This unit describes the 3-D cell culture and tumor engineering applications of Extracel, a novel semisynthetic ECM (sECM), based on cross-linked derivatives of hyaluronan and gelatin. A simplified cell encapsulation and pseudo-3-D culturing (on top of hydrogels) protocol is provided. In addition, the use of this sECM as a vehicle to obtain tumor xenografts with improved take rates and tumor growth is presented. These engineered tumors can be used to evaluate anticancer therapies under physiologically relevant conditions.
Article
An unmet need for expansion of primary cells and progenitor cells in three dimensions (3-D) is a synthetic mimic of the extracellular matrix (ECM) with user-controllable composition that would permit rapid recovery of viable cells under mild, non-enzymatic conditions. Three block copolymers based on disulfide-containing polyethylene glycol diacrylate crosslinkers were synthesized, and were used to crosslink thiol-modified hyaluronan and gelatin macromonomers in the presence of cells. The triblock PEGSSDA contained a single disulfide-containing block, the pentablock PEG(SS)(2)DA contained two disulfide blocks, and the heptablock PEG(SS)(3)DA contained three disulfide blocks. For each hydrogel composition, four cell types were encapsulated in 3-D, and growth and proliferation were evaluated. Murine NIH 3T3 fibroblasts, human HepG2 C3A hepatocytes, human bone marrow-derived mesenchymal stem cells (MSCs), and human umbilical vein endothelial cells (HUVECs) all showed excellent viability and growth during expansion in 3-D in the three disulfide block copolymer crosslinkers. After cell expansion, the hydrogels were dissociated using the thiol-disulfide exchange reaction in the presence of N-acetyl-cysteine or glutathione, which dissolved the hydrogel network. After dissolution, cells were recovered in high yield and with high viability by gentle centrifugation.
Article
Hyaluronan (HA) is a very useful polymer, but its properties sometimes need to be altered or enhanced by chemical modification for biomedical applications. A wide variety of HA derivatives are currently used for eye surgery, joint viscoelastic supplementation, and anti-adhesion films. The future promises to deliver new classes of HA-based reagents as well as new polymers that can be used in situ with living cells or within the body.
Article
Fetuses are surrounded by amniotic fluid rich in nutrients and other factors essential to fetal development and possibly to its scarless wound healing. The purpose of this study was to determine whether amniotic fluid contains factors that regulate activities of major proteases involved in the process of wound healing (e.g., collagenase, hyaluronidase, elastase, and cathepsin B). Human amniotic fluid was assayed in vitro for inhibition or stimulation of the activity of these enzymes. Our results showed that amniotic fluid enhanced collagenase activity at a concentration of 66 micrograms protein (p < 0.01), but inhibited activities of hyaluronidase (132 micrograms protein; p < 0.05), elastase (170 micrograms protein; p < 0.05), and cathepsin B (19 micrograms protein; p < 0.01). This finding suggests that amniotic fluid could have an important role in flawless fetal wound healing by regulating these matrix-degrading enzymes.
Article
The lack of scarring and fibrosis in healing fetal skin wounds may relate to a prolonged presence of hyaluronan (HA). It has been suggested that fetal wounds may lack hyaluronidase, but the hyaluronidase levels in fetal wounds remain unknown. The size of HA influences its biological action, especially in relation to angiogenesis, which is also reduced in fetal wound healing. The present study determined the levels and size of HA, as well as hyaluronidase levels, in fetal and adult lamb wounds. Wire mesh cylinders, or polyvinyl acetate sponges, were placed subcutaneously in fetal lambs at 75, 100 or 120 days gestation. Wound fluid and wound tissue were harvested 3, 7 or 14 days later. Samples were digested with papain and both HA and hyaluronidase activity were determined in a competitive ELISA assay. Size distribution of HA was estimated using a Sephacryl S1000 column and fractions were collected for HA determination. Adult wound fluid HA remained low (4-5 micrograms/ml) over the 14 days. Fetal fluids were similar on day 3, but increased to 15-25 micrograms/ml by day 7. In 75/100-day wounds, HA remained elevated at 14 days, but in 120-day fluids decreased to levels similar to adult fluid. The HA in all fluids was polydisperse with a main peak at 200 kDa. Hyaluronidase levels were detected in all samples, reaching a peak 7 days post-wounding. In adult wound fluids hyaluronidase was much higher than the fetal wound fluids. These data suggest that lower hyaluronidase levels in fetal wounds may underlie the different pattern of HA deposition seen in fetal wounds.
Article
This report describes ambulatory care visits made to physician offices in the United States. Statistics are presented on selected characteristics of the physician's practice, the patient, and the visit. This report also highlights visits to primary care specialties. The data presented in this report were collected from the 2002 National Ambulatory Medical Care Survey (NAMCS). NAMCS is a part of the ambulatory care component of the National Health Care Survey that measures health care utilization across various types of providers. NAMCS is a national probability sample survey of visits to office-based physicians in the United States. Sample data are weighted to produce annual national estimates. Selected trends from 1992, 1993, 1995, and 1997 are also presented. During 2002, an estimated 890 million visits were made to physician offices in the United States, an overall rate of 314.4 visits per 100 persons. From 1992 through 2002, the visit rate for persons 45 years of age and over increased by 14%, from 407.3 to 465.8 visits per 100 persons. The visit rate to physician offices in metropolitan statistical areas (MSAs) (337.3 visits per 100 persons) was significantly larger than the rate in non-MSAs (221.9 visits per 100 persons). For one-half of all office visits, regardless of specialty, physicians indicated they were the patient's primary care physician (PCP). Of the visits to physicians other than the patient's PCP, about one-third (31.1 percent) were referrals. New patients, representing 12.1 percent of the visits in 2002, are down 18% since 1992. Primary care specialists provided 90 percent of all preventive care visits. Essential hypertension, acute upper respiratory infection, diabetes mellitus, and arthropathies were the leading illness-related primary diagnoses. There were an estimated 104.0 million injury-related visits in 2002, or 36.7 visits per 100 persons. On average, 2.3 medications were ordered or provided at each office visit with any mention of a medication. The leading therapeutic class for drugs mentioned at office visits included nonsteroidal anti-inflammatory drugs (NSAIDs) (4.9 mentions per 100 visits) and antidepressants (4.5 mentions per 100 visits). Of primary care specialists, 25.8 percent reported not accepting new patients who are Medicaid enrollees.
Article
The usefulness of bone marrow cells in accelerating wound healing has not been evaluated despite increasing evidence that bone marrow contains mesenchymal stem cells that have multipotentiality to differentiate into various types of cells after they enter the microenvironment of a specific tissue (niche). To determine the effects of bone marrow cells and occlusive dressings in promoting wound healing in rats. We investigated by grafting, biopsy and immunohistochemistry whether various types of cells derived from green fluorescent protein (GFP)-transgenic rats would differentiate into wound component cells when administered topically on the wounds of rats. We also investigated whether topical application of bone marrow cells with an occlusive dressing would accelerate the healing of wounds with exposed bones, as measured by planimetry. GFP-labelled bone marrow cells contained multipotent stem cells that sufficiently differentiated into wound myofibroblasts presenting with alpha-smooth muscle actin in granulation tissue. Other types of cells, including myocytes, adipocytes, peripheral blood cells from buffy coat and dermal fibroblasts, did not express myofibroblast characteristics morphologically or immunohistochemically. Application of bone marrow cells and an occlusive dressing accelerated the repair of wounds with exposed bones, compared with an occlusive dressing only or with the topical administration of bone marrow cells plus a semidry to dry dressing. Our study indicates that bone marrow cells accelerate the healing of wounds at least in part through their differentiation into wound myofibroblasts. Thus, treatment of wounds with bone marrow cells and a supportive occlusive dressing is effective in promoting the formation of healthy granulation tissue and also for the preparation of an ideal wound bed.