James J Yoo

Kyungpook National University Hospital, Sŏul, Seoul, South Korea

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Publications (112)632.88 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Objective• Cell therapy for the regeneration of the damaged urethral sphincter is a major focus of urinary incontinence research.• To investigate whether a triple combination of early-differentiated cells derived from human amniotic fluid stem cells (hAFSCs) would show synergistic effects in urethral sphincter regeneration.Materials and Methods• hAFSCs were early-differentiated into muscle, neuron, and endothelial progenitor cells.• We injected them into the urethral sphincter region of pudendal neurectomized ICR mice, as single, double, or triple combinations.• Urodynamic study, histological, immunohistochemical and molecular analysis were performed.Results• Urodynamic study showed significantly improved leak point pressure in the triple combination group compared to the single or double combination groups.• These functional results were confirmed by histological and immunohistochemical analyses, as evidenced by the formation of new striated muscle fibers and neuromuscular junctions at the cell injection site.• Molecular analysis revealed higher target marker expression in the retrieved urethral tissue of the triple cell combined group.• The injection of early-differentiated hAFSCs suppressed in vivo host CD8 lymphocyte aggregations and did not form teratoma.• The nanoparticle-labeled early-differentiated hAFSCs could be tracked in vivo with optical imaging for up to 14 days after injection.Conclusions• Our novel concept of triple combined early-differentiated cell therapy for the damaged sphincter may provide a viable option for incontinence treatment.
    BJU International 05/2014; · 3.13 Impact Factor
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    ABSTRACT: A previous study demonstrated that disaccharides, antioxidants, and caspase inhibitors can be used in freezing solutions to reduce the concentration of Me2SO from the current standard of 10% (v/v) to 5% (v/v) or 2.5% and to eliminate fetal bovine serum (FBS) for the cryopreservation of human amniotic fluid-derived stem cells (AFSCs). Hence, this study investigated whether an irreversible inhibitor of caspase enzymes, benzyloxycarbonyl-Val-Ala-DL-Asp-fluoromethylketone (zVAD-fmk), could be used in post-thaw culture media to increase the survival rate of AFSCs. Our results showed that AFSCs cryopreserved in freezing solution containing trehalose, catalase, and 5% (v/v) Me2SO and then supplemented with zVAD-fmk in the post-thaw culture media showed similar post-thawing viability, proliferation, and apoptosis than cells cryopreserved in the control solution (10% (v/v) Me2SO and 20% FBS). The caspase-3 activity in all the cryopreservation solutions tested was similar to that of the control. Caspase-3, caspase-8, caspase-9, and PARP expression was not found in the cryopreserved cells. In addition, no difference was found in the survival rate and apoptosis between short-term (3 weeks) and long-term (1 year) storage of AFSCs cryopreserved in the solutions used in this study. The results of the present study demonstrate that recovery of cryopreserved cells was enhanced by using a caspase inhibitor in the post-thaw culture media.
    Cryobiology 04/2014; · 1.64 Impact Factor
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    ABSTRACT: Human amniotic fluid stem (hAFS) cells have been shown to differentiate into multiple lineages, including myoblasts. However, molecular mechanisms underlying the myogenic differentiation of hAFS cells and their regenerative potential for muscle injury remain to be elucidated. In order to induce myogenic differentiation of hAFS cells, lentiviruses for MYOD were constructed and transduced into hAFS cells. Formation of myotube-like cells was analyzed by immunocytochemistry, and expression of molecular markers for myoblasts was analyzed by reverse transcription polymerase chain reaction and Western blotting. For in vivo muscle regeneration, MYOD transduced human AFS cells were injected into left tibialis anterior (TA) muscles injured with cardiotoxin, and muscle regeneration was analyzed using hematoxilin and eosin, immunocytochemistry, and formation of neuro-muscular junction. MYOD expression in hAFS cells successfully induced differentiation into multinucleated myotube-like cells. Consistently, significant expression of myogenic marker genes, such as MYOG, DES, DMD, and MYH, was induced by MYOD. Analysis of pre-myogenic factors showed that expression of PAX3, MEOX1, and EYA2 was significantly increased by MYOD. MYOD was phosphorylated and localized in the nucleus. These results suggest that in hAFS cells, MYOD is phosphorylated and localized in the nucleus, thus inducing expression of myogenic factors, resulting in myogenic differentiation of hAFS cells. To test regenerative potential of MYOD-transduced hAFS cells, we transplanted them into injured muscles of immunodeficient BALB/cSlc-nu mice. The results showed a substantial increase in the volume of TA muscle injected with MYOD-hAFS cells. In addition, TA muscle tissue injected with MYOD-hAFS cells has more neuro-muscular junction, indicating functional restoration of muscle injury by hAFS cells expressing by MYOD. Collectively, our data suggest that transduction of hAFS cells with MYOD lentiviruses induces skeletal myogenic differentiation in vitro and morphological and functional regeneration of injured muscle in vivo.
    Stem Cell Research & Therapy 12/2013; 4(6):147. · 4.63 Impact Factor
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    ABSTRACT: Cellular therapy induced transient urodynamic improvement in a rat model of Parkinson's disease where bladder dysfunction was demonstrated after unilateral injection of 6-hydroxydopamine (6-OHDA) into the medial forebrain bundle (MFB). We attempted to prolong the effect by injecting allogeneic rat bone marrow mesenchymal stromal cells before (rBMSC) and after microencapsulation (ErBMSC) into the substantia nigra pars compacta (SNpc). Female rats underwent a unilateral stereotactic injection of 6-OHDA in the MFB. Treatment injection was performed in the ipsilateral SNpc of vehicle alone, or with either rBMSC or ErBMSC. Animals were evaluated by cystometry at four different time points after treatment: 7, 14, 28, and 42 days. Brains were extracted for immunostaining. At 42 days, the rBMSC group had lower threshold pressure (TP), intermicturition pressure, spontaneous activity (SA) and area under the curve than vehicle treated animals. The ErBMSC animals had lower TP at 28 days and lower SA at 42 days compared to vehicle treated animals. ErBMSC and rBMSC were demonstrated in the SNpc up to 42 days following transplantation. At 42 days, tyrosine hydroxylase (TH) positive neurons were more numerous in the SNpc of rBMSC, followed by ErBMSC, and vehicle treated animals. Urodynamic effects of the 6-OHDA lesion persisted up to 42 days after vehicle injection. Transplantation of rBMSC improved urodynamic pressures at 42 days after treatment more markedly than ErBMSC. This was associated with a higher number of TH-positive neurons in the treated SNpc of rBMSC animals, suggesting that functional improvements require a juxtacrine effect.
    The Journal of urology 08/2013; · 3.75 Impact Factor
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    ABSTRACT: Tissue-engineered muscle has been proposed as a means of repairing volumetric muscle defects to restore anatomical and functional recovery. We have previously demonstrated that denervated muscle, which is analogous to engineered muscle construct, can be reinnervated by direct transplantation of host nerve (neurotization) in a rat model. However, the use of this approach is not possible if the length of host nerve is inadequate and cannot be mobilized to the insertion site of the engineered muscle. In this study we investigated whether neurotization coupled with nerve guidance channels would increase the regeneration of neuromuscular junctions (NMJs) in completely denervated muscle and encourage neurofunctional recovery. Seventy-two Lewis rats were evaluated in three groups, a normal control group (n = 8), a denervated group (n = 32) and a neurotization coupled with nerve guidance group (n = 32). Neurofunctional behaviour and histological evaluations were performed at 4, 8, 12 and 20 weeks postoperatively. Extensor postural thrust (EPT) and compound muscle action potential (CMAP) amplitude were significantly improved in the nerve guidance group when compared with the denervated group, even though these values were different from those of the normal control group at 20 weeks postoperation. Regeneration of axons and NMJs was demonstrated histologically in the nerve guidance group. Neurotization coupled with nerve guidance channels leads to regeneration of axons and NMJs in completely denervated muscle. To our knowledge, this is the first report to show that nerve guidance can allow re-innervation in denervated muscle containing long-gap nerve injuries. Copyright © 2013 John Wiley & Sons, Ltd.
    Journal of Tissue Engineering and Regenerative Medicine 02/2013; · 4.43 Impact Factor
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    ABSTRACT: Timely innervation of muscle tissue is critical in the recovery of function, and this time-sensitive process relies heavily on the host tissue microenvironment after implantation. However, restoration of muscle tissue mass and function has been a challenge. We investigated whether pre-forming acetylcholine receptor (AChR) clusters on engineered muscle fibers using an AChR cluster-inducing factor (agrin) prior to implantation would facilitate established contacts between implanted muscle tissues and nerves and result in rapid innervation of engineered muscle in vivo. We showed that agrin treatment significantly increased the formation of AChR clusters on culture differentiated myotubes (C2C12), enhanced contacts with nerves in vitro and in vivo, and increased angiogenesis. Pre-fabrication of AChR clusters on engineered skeletal muscle using a released neurotrophic factor can accelerate innervations following implantation in vivo. This technique has considerable potential for enhancing muscle tissue function.
    Biomaterials 02/2013; · 8.31 Impact Factor
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    ABSTRACT: Tissue engineered scaffolds should actively participate not only in structural support but also in functional tissue regeneration. Thus, novel smart biomaterial scaffolds have been developed, which incorporate a variety of bioactive molecules to accelerate neo-tissue formation. The effective delivery of multiple bioactive molecules with distinct kinetics to target sites at an appropriate concentration and in a timely manner is desired to drive tissue development to completion. To achieve effective, controllable delivery of multiple factors, a dual protein delivery system has been developed by electrospinning poly(lactide-co-glycolide) (PLGA) with different hydrophilicities. Bovine serum albumin or myoglobin was incorporated into and released gradually from these electrospun fibrous PLGA scaffolds. All the scaffolds exhibited similar loading efficiencies of approximately 80% of the target proteins. The introduction of Pluronic F-127 (PF127) dramatically increased scaffold hydrophilicity, which affected the release kinetics of these proteins from the scaffolds. Furthermore, distinct protein release patterns were achieved when using dual protein-loaded scaffolds with different hydrophilicities when these scaffolds were fabricated by co-electrospinning. This system may be useful as a method for delivering multiple bioactive vehicles for tissue engineering applications.
    Biomedical Materials 02/2013; 8(1):014104. · 2.92 Impact Factor
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    ABSTRACT: Stem cells have become an important component of tissue regeneration, as they are able to differentiate into various cell types if guided appropriately. It is well known that cellular differentiation is greatly influenced by the surrounding microenvironment. We have developed a composite scaffold system using a collagen matrix derived from porcine bladder submucosa matrix (BSM) and poly(lactide-co-glycolide) (PLGA). In this study, we investigated whether a composite scaffold composed of naturally derived matrix combined with synthetic polymers would provide a microenvironment to facilitate the induction of osteogenic differentiation. We first showed that human amniotic fluid-derived stem cells (hAFSCs) adhered to the composite scaffolds and proliferated over time. We also showed that the composite scaffolds facilitated the differentiation of hAFSCs into an osteogenic lineage. The expression of osteogenic genes, including RUNX2, osteopontin (OPN) and osteocalcin (OCN) was upregulated in cells cultured on the composite scaffolds incubated in the osteogenic medium compared with ones without. Increased alkaline phosphatase (ALP) activity and calcium content indicates that hAFSCs seeded on 3D porous BSM-PLGA composite scaffolds resulted in higher mineralization rates as the duration of induction increased. This was also evidenced by the mineralized matrix within the scaffolds. The composite scaffold system provides a proper microenvironment that can facilitate osteogenic differentiation of AFSCs. This scaffold system may be a good candidate material for bone tissue engineering.
    Biomedical Materials 02/2013; 8(1):014107. · 2.92 Impact Factor
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    ABSTRACT: Although hormone replacement therapy is an option for the loss of ovarian function, hormone delivery through pharmacological means results in various clinical complications. The present study was designed to deliver sex steroids by a functional construct fabricated using encapsulation techniques. Theca and granulosa cells isolated from ovaries of 21-day old rats were encapsulated in multilayer alginate microcapsules to recapitulate the native follicular structure. Cells encapsulated in two other schemes were used as controls to assess the importance of the multilayer structure. The endocrine functions of the encapsulated cells were assessed in vitro for a period of 30 days. Encapsulated cells showed sustained viability during long-term in vitro culture with those encapsulated in multilayer capsules secreting significantly higher and sustained concentrations of 17 β-estradiol (E(2)) than the two other encapsulation schemes (p < 0.05, n = 6) in response to follicle-stimulating hormone (FSH) and luteinizing hormone (LH). In addition, cells in the multilayer microcapsules also secreted activin and inhibin in vitro. In contrast, when granulosa and theca cells were cultured in 2D culture, progesterone (P(4)) secretion increased while E(2) secretion decreased over a 30-day period. In summary, we have designed a multilayer engineered ovarian tissue that secretes sex steroids and peptide hormones and responds to gonadotropins, thus demonstrating the ability to recapitulate native ovarian structure ex vivo.
    Biomaterials 12/2012; · 8.31 Impact Factor
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    ABSTRACT: Oxygen and nutrients cannot be delivered to cells residing in the interior of large-volume scaffolds via diffusion alone. Several efforts have been made to meet the metabolic needs of cells in a scaffold by constructing mass transport channels, particularly in the form of bifurcating networks. In contrast with progress in fabrication technologies, however, an approach to designing an optimal network based on experimental evaluation has not been actively reported. The main objective of this study was to establish a procedure for designing an effective microfluidic network system for a cell-seeded scaffold and to develop an experimental model to evaluate the design. We proposed a process to design a microfluidic network by combining an oxygen transport simulation with biomimetic principles governing biological vascular trees. The simulation was performed with the effective diffusion coefficient (De,s ), which was experimentally measured in our previous study. Porous scaffolds containing an embedded microfluidic network were fabricated using the lost mold shape-forming process and salt leaching method. The reliability of the procedure was demonstrated by experiments using the scaffolds. This approach established a practical basis for designing an effective microfluidic network in a cell-seeded scaffold.
    Langmuir 12/2012; · 4.38 Impact Factor
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    ABSTRACT: Bioprinting is an emerging technique used to fabricate viable, 3D tissue constructs through the precise deposition of cells and hydrogels in a layer-by-layer fashion. Despite the ability to mimic the native properties of tissue, printed 3D constructs that are composed of naturally-derived biomaterials still lack structural integrity and adequate mechanical properties for use in vivo, thus limiting their development for use in load-bearing tissue engineering applications, such as cartilage. Fabrication of viable constructs using a novel multi-head deposition system provides the ability to combine synthetic polymers, which have higher mechanical strength than natural materials, with the favorable environment for cell growth provided by traditional naturally-derived hydrogels. However, the complexity and high cost associated with constructing the required robotic system hamper the widespread application of this approach. Moreover, the scaffolds fabricated by these robotic systems often lack flexibility, which further restrict their applications. To address these limitations, advanced fabrication techniques are necessary to generate complex constructs with controlled architectures and adequate mechanical properties. In this study, we describe the construction of a hybrid inkjet printing/electrospinning system that can be used to fabricate viable tissues for cartilage tissue engineering applications. Electrospinning of polycaprolactone fibers was alternated with inkjet printing of rabbit elastic chondrocytes suspended in a fibrin-collagen hydrogel in order to fabricate a five-layer tissue construct of 1 mm thickness. The chondrocytes survived within the printed hybrid construct with more than 80% viability one week after printing. In addition, the cells proliferated and maintained their basic biological properties within the printed layered constructs. Furthermore, the fabricated constructs formed cartilage-like tissues both in vitro and in vivo as evidenced by the deposition of type II collagen and glycosaminoglycans. Moreover, the printed hybrid scaffolds demonstrated enhanced mechanical properties compared to printed alginate or fibrin-collagen gels alone. This study demonstrates the feasibility of constructing a hybrid inkjet printing system using off-the-shelf components to produce cartilage constructs with improved biological and mechanical properties.
    Biofabrication 11/2012; 5(1):015001. · 3.71 Impact Factor
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    ABSTRACT: Acellular collagen matrices have been used as an onlay material for urethral reconstruction. However, cell-seeded matrices have been recommended for tubularized urethral repairs. In this study we investigated whether long segmental penile urethral replacement using autologous cell-seeded tubularized collagen-based matrix is feasible. Autologous bladder epithelial and smooth muscle cells from nine male rabbits were grown and seeded onto preconfigured tubular matrices constructed from decellularized bladder matrices obtained from lamina propria. The entire anterior penile urethra was resected in 15 rabbits. Urethroplasties were performed with tubularized matrices seeded with cells in nine animals, and with matrices without cells in six. Serial urethrograms were performed at 1, 3 and 6 months. Retrieved urethral tissues were analysed using histo- and immunohistochemistry, western blot analyses and organ bath studies. The urethrograms showed that animals implanted with cell-seeded matrices maintained a wide urethral calibre without strictures. In contrast, the urethras with unseeded scaffolds collapsed and developed strictures. Histologically, a transitional cell layer surrounded by muscle was observed in the cell-seeded constructs. The epithelial and smooth muscle phenotypes were confirmed with AE1/AE3 and α-actin antibodies. Organ bath studies of the neourethras confirmed both physiological contractility and the presence of neurotransmitters. Tubularized collagen matrices seeded with autologous cells can be used successfully for long segmental penile urethra replacement, while implantation of tubularized collagen matrices without cells leads to poor tissue development and stricture formation. The cell-seeded collagen matrices are able to form new tissue, which is histologically similar to native urethra. Copyright © 2012 John Wiley & Sons, Ltd.
    Journal of Tissue Engineering and Regenerative Medicine 11/2012; · 4.43 Impact Factor
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    ABSTRACT: This study investigated the differentiation of human amniotic fluid-derived stem cells (hAFSCs) into insulin-producing clusters in vitro. Adenovirally-delivered mouse Pdx1 (Ad-Pdx1) induced human Pdx1 expression in hAFSCs and enhanced the coordinated expression of downstream β-cell markers. When Ad-Pdx1-transduced hAFSCs were sequentially treated with activin A, bFGF and nicotinamide and the culture plate surface coated with poly-l-ornithine, the expression of islet-associated human mRNAs for Pdx1, Pax6, Ngn3 and insulin was increased. C-peptide ELISA confirmed that Ad-Pdx1-transduced hAFSCs processed and secreted insulin in a manner consistent with that pathway in pancreatic β-cells. To sustain the β-cell-like phenotype and investigate the effect of three-dimensional (3D) conformation on the differentiation of hAFSCs, Pdx1-transduced cells were encapsulated in alginate and cultured long-term under serum-free conditions. Over 2 weeks, partially differentiated hAFSC clusters increased in size and increased insulin secretion. Taken together, these data demonstrate that ectopic Pdx1 expression initiates pancreatic differentiation in hAFSCs and that a β-cell-like phenotype can be augmented by culture conditions that mimic the stromal components and 3D geometry associated with pancreatic islets. Copyright © 2012 John Wiley & Sons, Ltd.
    Journal of Tissue Engineering and Regenerative Medicine 11/2012; · 4.43 Impact Factor
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    ABSTRACT: The most promising treatment for stress urinary incontinence can be a cell therapy. We suggest human amniotic fluid stem cells (hAFSCs) as an alternative cell source. We established the optimum in vitro protocol for the differentiation from hAFSCs into muscle progenitors. These progenitors were transplanted into the injured urethral sphincter and their therapeutic effect was analyzed. For the development of an efficient differentiation system in vitro, we examined a commercial medium, co-culture and conditioned medium (CM) systems. After being treated with CM, hAFSCs were effectively developed into a muscle lineage. The progenitors were integrated into the host urethral sphincter and the host cell differentiation was stimulated in vivo. Urodynamic analysis showed significant increase of leak point pressure and closing pressure. Immunohistochemistry revealed the regeneration of circular muscle mass with normal appearance. Molecular analysis observed the expression of a larger number of target markers. In the immunogenicity analysis, the progenitor group had a scant CD8 lymphocyte. In tumorigenicity, the progenitors showed no teratoma formation. These results suggest that hAFSCs can effectively be differentiated into muscle progenitors in CM and that the hAFSC-derived muscle progenitors are an accessible cell source for the regeneration of injured urethral sphincter.
    Journal of Korean medical science 11/2012; 27(11):1300-7. · 0.84 Impact Factor
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    ABSTRACT: The inner ears of adult humans and other mammals possess a limited capacity for regenerating sensory hair cells, which can lead to permanent auditory and vestibular deficits. During development and regeneration, undifferentiated supporting cells within inner ear sensory epithelia can self-renew and give rise to new hair cells; however, these otic progenitors become depleted postnatally. Therefore, reprogramming differentiated supporting cells into otic progenitors is a potential strategy for restoring regenerative potential to the ear. Transient expression of the induced pluripotency transcription factors, Oct3/4, Klf4, Sox2, and c-Myc reprograms fibroblasts into neural progenitors under neural-promoting culture conditions, so as a first step, we explored whether ectopic expression of these factors can reverse supporting cell quiescence in whole organ cultures of adult mouse utricles. Co-infection of utricles with adenoviral vectors separately encoding Oct3/4, Klf4, Sox2, and the degradation-resistant T58A mutant of c-Myc (c-MycT58A) triggered significant levels of supporting cell S-phase entry as assessed by continuous BrdU labeling. Of the four factors, c-MycT58A alone was both necessary and sufficient for the proliferative response. The number of BrdU-labeled cells plateaued between 5-7 days after infection, and then decreased ∼60% by 3 weeks, as many cycling cells appeared to enter apoptosis. Switching to differentiation-promoting culture medium at 5 days after ectopic expression of c-MycT58A temporarily attenuated the loss of BrdU-labeled cells and accompanied a very modest but significant expansion of the sensory epithelium. A small number of the proliferating cells in these cultures labeled for the hair cell marker, myosin VIIA, suggesting they had begun differentiating towards a hair cell fate. The results indicate that ectopic expression of c-MycT58A in combination with methods for promoting cell survival and differentiation may restore regenerative potential to supporting cells within the adult mammalian inner ear.
    PLoS ONE 10/2012; 7(10):e48704. · 3.53 Impact Factor
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    ABSTRACT: This study was designed to develop a versatile method for fabricating complex and heterogeneous three-dimensional (3D) tissue constructs using simultaneous ink-jetting of multiple cell types. Human amniotic fluid-derived stem cells (hAFSCs), canine smooth muscle cells (dSMCs), and bovine aortic endothelial cells (bECs), were separately mixed with ionic cross-linker calcium chloride (CaCl(2)), loaded into separate ink cartridges and printed using a modified thermal inkjet printer. The three cell types were delivered layer-by-layer to pre-determined locations in a sodium alginate-collagen composite located in a chamber under the printer. The reaction between CaCl(2) and sodium alginate resulted in a rapid formation of a solid composite gel and the printed cells were anchored in designated areas within the gel. The printing process was repeated for several cycles leading to a complex 3D multi-cell hybrid construct. The biological functions of the 3D printed constructs were evaluated in vitro and in vivo. Each of the printed cell types maintained their viability and normal proliferation rates, phenotypic expression, and physiological functions within the heterogeneous constructs. The bioprinted constructs were able to survive and mature into functional tissues with adequate vascularization in vivo. These findings demonstrate the feasibility of fabricating complex heterogeneous tissue constructs containing multiple cell types using inkjet printing technology.
    Biomaterials 10/2012; · 8.31 Impact Factor
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    ABSTRACT: Chronic renal failure is a devastating disease that leads to a multitude of complications. Cell therapy has emerged as a potential treatment modality for renal failure. However, efficacy testing on systemic renal function has been challenging due to the limited availability of reliable models that are fully characterized. In this study, we investigated the possibility of using renal ischemia/reperfusion (I/R) injury as a viable model for testing cell therapies. We examined functional and pathological changes in rat kidneys that were exposed to different ischemia times. Male Lewis rats were divided into five groups. Renal failure was induced by clamping both renal pedicles for combinations of 60, 75, and 90 min, followed by reperfusion. Age-matched healthy rats served as controls. Blood was collected at regular intervals for serum chemistry, and kidneys were harvested at the same intervals for histomorphological assessment. Serum creatinine levels of the animals with I/R injury increased significantly after 3 days and returned to normal levels at 4 weeks. Histologically, kidney tissue showed progressive glomerular and tubular deterioration with varying degrees of fibrosis. Animals exposed to 75- and 90-min ischemia combination times consistently generated more severe injury than the 60-min ischemia period. However, these groups resulted in a high mortality rate. A model in which one kidney is exposed to a shorter ischemia time (60 or 90 min) resulted in sustained renal damage with a lower mortality rate. This study shows that kidneys exposed to I/R result in renal tissue damage as well as decreased renal function. This model can be used to study both the short-term and longer-term effects of kidney disease by varying the length of the ischemic time. In particular, the use of longer ischemic times (75 and 90 min) could be used to study new therapies for acute renal disease, whereas shorter ischemic times (60 min) could be used to study therapies for chronic renal insufficiency.
    Renal Failure 10/2012; 34(10):1324-32. · 0.94 Impact Factor
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    ABSTRACT: Tissue-engineered blood vessels (TEBV) have been proposed as an alternative to prosthetic grafts for dialysis access. However, arteriovenous (AV) grafts must withstand extreme flow rates and frequent needle trauma. In a proof-of-concept study, we sought to determine whether scaffold-based TEBV could withstand the hemodynamic and mechanical challenges of chronic dialysis access. TEBV were constructed using decellularized arterial scaffolds seeded with autologous ovine endothelial cells (EC) derived from circulating endothelial progenitor cells (EPC) using a novel high-affinity capture approach. Seeded scaffolds were preconditioned to arterial pressure and flow in a bioreactor for 2 weeks prior to implantation to create carotid artery to jugular vein AV grafts in each animal. TEBV were healed for 1 month before initiating percutaneous needle puncture 3 days/week. TEBV wall geometry and patency were monitored using duplex imaging and were either explanted for histologic analysis at 2 months (n = 5) or followed for up to 6 months until venous outflow stenosis threatened AV graft patency (n = 6). Despite high flow, TEBV maintained stable geometry with only modest wall dilation (under 6%) by 4 months after implantation. Needle access was well tolerated with a single puncture site complication, a small pseudoaneurysm, occurring in the late group. Time-to-hemostasis at puncture sites averaged 4 ± 2 minutes. Histologic analysis at 2 months demonstrated repopulation of the outer TEBV wall by host cells and healing of needle punctures by cellular ingrowth and new matrix deposition along the tract. TEBV followed beyond 2 months showed stable wall geometry but, consistent with the primary mode of clinical AV graft failure, all TEBV eventually developed venous anastomotic stenosis (mean, 4.4 ± 0.9 months; range, 3.3-5.6 months postimplantation; n = 6). This pilot study supports the concept of creating dialysis access from scaffold-based autologous TEBV. Engineered AV grafts were created within a clinically relevant time frame and demonstrated stable wall geometry despite high flow and repeated puncture. Cellular ingrowth and puncture site healing may improve wall durability, but venous outflow stenosis remains the primary mode of TEBV graft failure in the ovine model.
    Journal of vascular surgery: official publication, the Society for Vascular Surgery [and] International Society for Cardiovascular Surgery, North American Chapter 09/2012; 56(3):783-93. · 2.98 Impact Factor
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    ABSTRACT: BACKGROUND: Stem cell injection therapies have been proposed to overcome the limited efficacy and adverse reactions of bulking agents. However, most have significant limitations, including painful procurement, requirement for anesthesia, donor site infection and a frequently low cell yield. Recently, human amniotic fluid stem cells (hAFSCs) have been proposed as an ideal cell therapy source. In this study, we investigated whether periurethral injection of hAFSCs can restore urethral sphincter competency in a mouse model. METHODS: Amniotic fluids were collected and harvested cells were analyzed for stem cell characteristics and in vitro myogenic differentiation potency. Mice underwent bilateral pudendal nerve transection to generate a stress urinary incontinence (SUI) model and received either periurethral injection of hAFSCs, periurethral injection of Plasma-Lyte (control group), or underwent a sham (normal control group). For in vivo cell tracking, cells were labeled with silica-coated magnetic nanoparticles containing rhodamine B isothiocyanate (MNPs@SiO2 (RITC)) and were injected into the urethral sphincter region (n = 9). Signals were detected by optical imaging. Leak point pressure and closing pressure were recorded serially after injection. Tumorigenicity of hAFSCs was evaluated by implanting hAFSCs into the subcapsular space of the kidney, followed two weeks later by retrieval and histologic analysis. RESULTS: Flow activated cell sorting showed that hAFSCs expressed mesenchymal stem cell (MSC) markers, but no hematopoietic stem cell markers. Induction of myogenic differentiation in the hAFSCs resulted in expression of PAX7 and MYOD at Day 3, and DYSTROPHIN at Day 7. The nanoparticle-labeled hAFSCs could be tracked in vivo with optical imaging for up to 10 days after injection. Four weeks after injection, the mean LPP and CP were significantly increased in the hAFSC-injected group compared with the control group. Nerve regeneration and neuromuscular junction formation of injected hAFSCs in vivo was confirmed with expression of neuronal markers and acetylcholine receptor. Injection of hAFSCs caused no in vivo host CD8 lymphocyte aggregation or tumor formation. CONCLUSIONS: hAFSCs displayed MSC characteristics and could differentiate into cells of myogenic lineage. Periurethral injection of hAFSCs into an SUI animal model restored the urethral sphincter to apparently normal histology and function, in absence of immunogenicity and tumorigenicity.
    BMC Medicine 08/2012; 10(1):94. · 7.28 Impact Factor
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    ABSTRACT: In tissue engineering, stem cells have become an ideal cell source that can differentiate into most human cell types. Among the stem cells, bone marrow-derived stem cells (BMSCs) have been widely studied, and there is strong evidence that these cells can be differentiated into cells of the osteogenic lineage. Thus, BMSCs have become the gold standard for studies of tissue engineering in orthopedics. However, novel stem cell sources, such as amniotic fluid-derived stem cells (AFSCs) have been identified, and these have important and unique features that may lead to novel and successful applications toward the regeneration of bone tissue. This study was designed to originally compare the osteogenic potential of both BMSCs and AFSCs under distinct culture environments to determine whether the osteogenic differentiation process of both types of stem cells is related to the origin of the cells. Osteogenic differentiation was carried out in both two and three dimensions using a tissue culture plate and by means of seeding the cells onto microfibrous starch and poly(ɛ-caprolactone) scaffolds (a blend of starch and polycaprolactone), respectively. BMSCs and AFSCs were successfully differentiated into the osteogenic cell type, as cells derived from them produced a mineralized extracellular matrix. Nevertheless, the two types of cells presented different expression patterns of bone-related markers as well as different timing of differentiation, indicating that both cell origin and the culture environment have a significant impact on the differentiation into the osteogenic phenotype in AFSCs and BMSCs.
    Tissue Engineering Part A 08/2012; · 4.64 Impact Factor

Publication Stats

4k Citations
632.88 Total Impact Points

Institutions

  • 2011–2014
    • Kyungpook National University Hospital
      Sŏul, Seoul, South Korea
  • 2013
    • Seoul National University Bundang Hospital
      Sŏul, Seoul, South Korea
  • 2005–2013
    • Wake Forest School of Medicine
      • Department of Urology
      Winston-Salem, North Carolina, United States
  • 2012
    • Kyungpook National University
      • Department of Urology
      Daikyū, Daegu, South Korea
    • Assiut University
      Lycopolis, Asyūţ, Egypt
  • 2006–2011
    • Wake Forest University
      • Wake Forest Institute for Regenerative Medicine (WFIRM)
      Winston-Salem, North Carolina, United States
  • 2008
    • University of Southern California
      • Department of Urology
      Los Angeles, CA, United States
  • 1998–2004
    • Harvard Medical School
      • Department of Surgery
      Boston, Massachusetts, United States
  • 1997–2003
    • Boston Children's Hospital
      • Department of Urology
      Boston, Massachusetts, United States
  • 2002
    • Advanced Cell Technology
      Marlboro Meadows, Maryland, United States