| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
a Department of Anatomy and Physiology and
b Department of Animal Science, Kansas State University, Manhattan, Kansas, USA;
c Department of Anatomy and Histology, Faculty of Veterinary Medicine, Kafr-El-Sheikh, Tanta University, Tanta, Egypt
Key Words. Stem cell plasticity • Telomerase • c-kit • Myofibroblast • Neural induction
Kathy E. Mitchell, Ph.D., 228 Coles Hall, Department of Anatomy and Physiology, Kansas State University, Manhattan, Kansas 66506-5802, USA. Telephone: 785-532-4825; Fax: 785-532-4557; e-mail: mitchell{at}vet.ksu.edu
 |
ABSTRACT |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsWharton’s Jelly Cells...DiscussionReferences |
|---|
|
INTRODUCTION |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsWharton’s Jelly Cells...DiscussionReferences |
|---|
The ability of stem cells to self-renew is critical to their function as a reservoir of primitive cells. In contrast, most somatic cells have a limited capacity for self-renewal due to telomere shortening [3]. Telomerase is a ribonucleoprotein that replicates telomeres during the S phase of mitosis [4]. Telomerase activity is found in human germ, tumor, and embryonic cell lines and is thought to be responsible for the unlimited capacity for self-renewal of these cell types [5, 6]. Telomerase activity is, thus, one marker for stem cells. Another stem cell marker is the stem cell factor receptor, c-kit (CD117). c-kit is a receptor tyrosine kinase that is expressed in many types of tissue-specific stem cells and is essential for many developmental processes, including hematopoesis, melanogenesis, and fertility [7]. The c-kit receptor ligand, stem cell factor, is a member of the PDGF family of growth factors and is secreted by epithelial cells, leukocytes, fibroblasts, and myofibroblasts [8].
Embryonic stem cells are totipotent and can be maintained in culture in the presence of the cytokine, leukemia inhibitory factor (LIF) [9–11]. When LIF is withdrawn, aggregates, called embryoid bodies, form. A wide variety of cell types migrate away from the embryoid bodies, including some that appear neuronal [12]. Importantly, it has been shown that embryonic stem cells can be induced to differentiate into neurons and glia by treatment with retinoic acid [13–15] or basic fibroblast growth factor (bFGF) [16]. Embryonic-stem cell-derived neurons express neurofilaments, neuron-specific class III ß-tubulin (TuJ1) [13–16], and a number of neuron-specific microtubule-associated proteins, including growth-cone-associated protein (GAP-43), which is localized to axons [17].
Neural stem cells are immature, uncommitted cells that exist in both the developing brain and in the adult nervous system [18–21]. Neural stem cells can undergo expansion and can differentiate into neurons, astrocytes, and oligodendrocytes [22, 23]. However, neural stem cells from the central nervous system are rare, require an invasive procedure to obtain, and may have a more limited potential to proliferate in culture than embryonic stem cells.
Postnatal stem cells from other sources, such as bone marrow stromal cells, may offer an easily attainable source of cells for therapeutic purposes. Recent studies have indicated that adult stem cells derived from bone marrow and skin can be expanded in culture and can give rise to multiple lineages [24–26]. Further evidence of stem cell plasticity comes from a study that showed that bone marrow stromal cells injected into lateral ventricles of neonatal mice differentiated into astrocytes and neurofilament-expressing cells [27]. Bone marrow stromal cells have also been induced to differentiate into neurons in vitro [28, 29]. Woodbury et al. [29] showed that bone marrow stromal cells could be induced to differentiate into neurons, almost exclusively, by using a variation of the bFGF method that induces embryonic stem cells to form neural cell types. When treated in this manner, the induced bone marrow stromal cells developed a highly differentiated, neuron-like morphology, with processes that had primary and secondary branches, and expressed markers for neural precursors, mature neurons, and glial cells.
Wharton’s jelly is the gelatinous connective tissue from umbilical cord and is composed of myofibroblast-like stromal cells, collagen fibers, and proteoglycans [30]. Here, we present our findings about proliferative cells that we have isolated from Wharton’s jelly. Our results show that Wharton’s jelly cells are easily attainable and can be expanded in vitro, maintained in culture, and induced to differentiate into neural cells. They are a potential source of multipotent stem cells that may serve many therapeutic and biotechnological roles.
|
MATERIALS AND METHODS |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsWharton’s Jelly Cells...DiscussionReferences |
|---|
Induction of Neural Cells from Wharton’s Jelly Matrix Cells
Wharton’s jelly cells were induced by the method of Woodbury et al. [29] to become neural stem cells and neuronal cells. Briefly, Wharton’s jelly cells were preinduced by overnight treatment with bFGF (10 ng/ml) in DMEM and 20% fetal bovine serum. Neuronal differentiation was induced with 2% dimethylsulfoxide (DMSO) and 200 µM butylated hydroxyanisole (BHA) in DMEM plus 2% fetal bovine serum. After 5 hours, the medium was modified for long-term induction by adding 25 mM KCl, 2 mM valproic acid, 10 µM forskolin, 1 µM hydrocortisone, and 5 µg/ml insulin. Matrix coated plates and tissue culture slides were obtained from BD Biosciences.
Immunocytochemistry
Immunocytochemistry was done by immunoperoxidase using a commercial kit (VectaStain; Vectur Laboratories; Burlingame, CA) or immunofluorescence staining. For immunofluorescence, cells were washed with phosphate buffered saline (PBS) and fixed by treating with methanol at -10°C. This was followed by washing with three changes of PBS and air drying. Slides were blocked with 10% normal blocking serum (derived from same species as the secondary antibody) in PBS for 20 minutes, washed with PBS, and incubated with primary antibody in 1.5% normal blocking serum in PBS for 60 minutes (0.1 to 2.0 µg/ml). The slide was then washed three times with PBS and incubated with fluorescein isothiocyanate (FITC)-conjugated secondary antibody (Santa Cruz Biotechnology) for 15 minutes. Resulting immunoreactive cells were visualized by fluorescence microscopy. For immunoperoxidase, cells were fixed by treating with 10% buffered neutral formalin overnight. Slides were blocked with 5% normal blocking serum (derived from same species as the secondary antibody) in PBS for 30 minutes, followed by incubation with primary antibody for 60 minutes. The slide was incubated with horseradish-peroxidase-linked secondary antibody and developed according to kit instructions.
Preparation of Whole-Cell Lysates
Whole-cell lysates were made from Wharton’s jelly cells by standard techniques using a lysis buffer consisting of PBS with 1% Nonidet P40, 0.5% sodium deoxycholate, 0.1% SDS, and a protease inhibitor cocktail (1:500) (Sigma P8340; St. Louis, MO). Lysis buffer was added to the culture dish with Wharton’s jelly cells after washing with ice-cold PBS three times. The culture dishes were scraped, and the lysate was aspirated into a syringe with a 21-gauge needle to shear DNA. The lysates were rocked at 4°C for 1 hour and centrifuged for 10 minutes at 10,000 g to remove insoluble material. Protein concentrations were determined by the Micro BCA assay (Pierce; Rockford, IL). Typically, a protein concentration of 1 µg/µl was obtained by this protocol.
Immunoblotting
Solubilized proteins were separated by SDS-PAGE on 8%-16% continuous gradient gels under reducing conditions and transferred to nitrocellulose membranes by electrophoretic transfer in a tank system with plate electrodes. The membranes were blocked for 1 hour at room temperature with 5% nonfat milk in Tris-buffered saline (TBS: 100 mM Tris, 0.9% NaCl, pH 7.5) containing 0.1% Tween 20. Membranes were incubated with primary antibody for 1 hour at room temperature followed by three washes with 0.1% Tween/TBS. Membranes were incubated for 1 hour at room temperature with the appropriate horseradish-peroxidase-conjugated secondary antibody (Pierce) diluted in 0.1% Tween/TBS at (1:50,000). After four additional washes with 0.1% Tween/TBS, the blots were visualized by chemiluminescence (Super Signal; Pierce) and recorded on radiographic film.
Antibodies
Antibodies were used at the following dilutions for immunoblotting and immunocytochemistry, respectively: neuron-specific enolase (NSE) (1:2,000, 1:500; Chemicon; Temecula, CA; http://www.chemicon.com); neurofilament M (NFM) (immunocytochemistry only 1:500; Chemicon); TuJ1 (1:2,000, 1:1,000; Covance; Princeton, NJ); glial fibrillary acidic protein (GFAP) (1:2,000, 1:500; Chemicon); 2',3'-cyclic nucleotide-3'-phospodiesterase (CNPase) (1:2,000, immunoblot only; Chemicon); smooth muscle actin (1:2,000, immunoblot only; Research Diagnostics; Flanders, NJ); c-kit (1:2,000, 1:200; Research Diagnostics); tyrosine hydroxylase (TH) (1:1,000, immunoblot only; East Acres Biologicals; Southbridge, MA); and GAP-43 (1:2,000, 1:200; Santa Cruz Biotechnology; Santa Cruz, CA).
Telomerase Assay
The TRAPeze® XL Telomerase Detection Kit (Intergen; Norcross, GA) was used according to the manufacturer’s instructions to measure the telomerase enzyme activity of porcine Wharton’s jelly cells. The TRAPeze® XL Telomerase Detection Kit uses a modified TRAP (telomerase repeat amplification protocol) assay to detect telomerase activity through the amplification of telomeric repeats using fluorescence energy transfer primers (AmplifluorTM) that produce measurable fluorescence only when incorporated into TRAP products.
Porcine Wharton’s jelly cells that were grown in culture for 45 passages were washed twice with PBS and then frozen at -80°C for 30 minutes. The cells were resuspended in 100 µl of CHAPS XL Lysis Buffer (included in the telomerase detection kit) with 20 U ribonuclease inhibitor (Promega; Madison, WI; http://www.promega.com). This suspension was incubated on ice for 30 minutes. The extract was pelleted (12,000 g at 4°C), and the supernatant was frozen at -80°C until assayed for telomerase. Human carcinoma cells (included in the telomerase detection kit) were used as a positive control. For telomerase quantification, 50-µl reactions were prepared containing 10 µl of the 5X TRAPeze XL® Reaction Mix, 2 U of Taq Polymerase (Promega), 38 µl of sterile polymerase chain reaction (PCR) water, and 2 µl of the sample cell extract. This mixture was then incubated at 30°C for 30 minutes to allow for the telomerase enzyme to synthesize telomeric repeats. PCR amplification of the telomeric repeats was performed on a Touchgene gradient thermocycler (Techne; Princeton, NJ) using a three-step PCR at 94°C for 30 seconds, 59°C for 30 seconds, and 72°C for 1 minute for 35 cycles, followed by a 55°C/25-minute extension step. Following a 5-minute incubation at 5°C, the fluorescence of each reaction was measured with a Fluoroskan Ascent FL fluorescent plate reader (Labsystems; Farnborough, UK). The telomerase activity of each sample was determined by calculating the ratio of the increase in fluorescein absorbance (produced by the amplification of telomeric repeats) divided by the increase in sulforhodamine absorbance.
|
RESULTS |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsWharton’s Jelly Cells...DiscussionReferences |
|---|
). As Wharton’s jelly cells reached confluency, colonies of round cells began to form, reminiscent of neurospheres.
|
|
WHARTON’S JELLY CELLS DIFFERENTIATE INTO NEURAL CELLS |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsWharton’s Jelly Cells...DiscussionReferences |
|---|
), with some cells developing multiple neurites extending from the cell body. Single long axon-like processes developed (Fig.1B), and granular structures reminiscent of Nisil substance were also observed in many of the Wharton’s jelly cells (Fig.1C).
Characteristics of Undifferentiated Wharton’s Jelly Cells
Wharton’s jelly cells were examined for expression of cell markers that have been identified in other postnatal mesenchymal stem cells. We tested for expression of c-kit, the stem cell factor receptor, which is expressed in bone marrow stromal cells and hematopoetic stem cells. c-kit expression was very high in Wharton’s jelly colony-forming cells (Fig.2) and in individual round undifferentiated cells that were plated on matrix-coated plates with a combination of poly-D-lysine (PDL) and laminin or laminin alone, even after neural induction (Fig.3). The expression of c-kit by Wharton’s jelly cells was greatly diminished after induction into neural cells, and expression was detected only in cells plated on laminin (Fig.3C).
|
|
). The telomerase activity was inactivated by heating, as expected. Minimal, if any, PCR inhibition was detected, as indicated by the greater telomerase activity measured in the sample that included Wharton’s jelly cells and positive-control cells. The sum of the telomerase activities measured for the two separately was approximately the same as the combined sample.
|
). Smooth muscle actin was expressed at similar levels in Wharton’s jelly cells grown on PDL/laminin matrix and in Wharton’s jelly cells grown on plastic. Thus, Wharton’s jelly cells that were maintained in culture for extensive doublings continued to express this myofibroblast marker. Growth on matrix did not appear to select for a different population of cells. However, smooth muscle actin expression was much lower by 10 days after neural induction, suggesting that the phenotype of the majority of the induced Wharton’s jelly cells changed to neural from myofibroblast.
|
). Immunoblots of whole-cell lysates were done to assess whether NSE was expressed in untreated Wharton’s jelly cells or in the neurosphere-like colonies. NSE was expressed in both untreated Wharton’s jelly cells and in colonies (Fig.6B). However, there was slightly less NSE expression in Wharton’s jelly cells 5 hours postinduction (Fig.6B).
|
) and 3 (Fig.7B) days postinduction. Note the long processes that were revealed by NFM immunostaining, and the formation of networks that increased in complexity from day 1 to day 3 postinduction. TuJ1, a class III neuron-specific ß-tubulin, is another marker for neuronal differentiation. The immunoblot in Figure 8A shows that increasing levels of TuJ1 were expressed during the course of differentiation from day 1 to day 10 postinduction. Interestingly, a low level of TuJ1 was expressed in Wharton’s jelly cells treated only with bFGF overnight. Fully induced Wharton’s jelly cells showed positive immunostaining for TuJ1 primarily in the soma and proximal part of the axon-like structure (Fig.8B).
|
|
). Immunoblot analysis showed that TH was expressed in neurosphere-like colonies and in fully induced Wharton’s jelly cells, but not in untreated cells. GAP-43, a neuron-specific microtubule-associated protein that localizes to axons, was also expressed in Wharton’s jelly cells after they differentiated (Fig.9). The long processes of the induced Wharton’s jelly cells showed positive staining for GAP-43. Immunoblot analysis confirmed expression of GAP-43 10 days postinduction in cells grown on either plastic or PDL/laminin but not in untreated Wharton’s jelly cells (Fig.9C) although the level of expression was higher in the cells grown on PDL/laminin.
|
). GFAP-positive cells were identified in Wharton’s jelly cultures after full induction. The morphology of the GFAP-positive cells was stellate and lacked the long processes of the cells that were positive for neuronal markers (Fig.10A). GFAP expression was observed in untreated Wharton’s jelly cells but was expressed at slightly higher levels after induction (Fig.10B). In contrast, expression of CNPase, a marker for oligodendrocytes, was nearly identical in untreated, bFGF-treated, and fully induced Wharton’s jelly cells (Fig.10C).
|
). Initial studies to determine whether there were different populations of cells that arose from different regions of the umbilical cord indicated that the placental end may be a richer source of cells. Whether there are differences in the characteristics of the cells from the placental versus fetal end is currently under investigation. Like porcine Wharton’s jelly cells, at least some human cells were positive for smooth muscle actin (data not shown).
|
shows the changes observed in morphology of human Wharton’s jelly cells after treatment with bFGF, BHA, and DMSO and after long-term induction media treatment for 1.5 days. Nearly 100% of the fully induced cells were positive for TuJ1 and NFM by immunocytochemistry. These studies are currently being extended to examine characteristics of longer-term cultures of induced human Wharton’s jelly cells. |
DISCUSSION |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsWharton’s Jelly Cells...DiscussionReferences |
|---|
Wharton’s jelly cells share characteristics with other types of stem cells as well. Importantly, Wharton’s jelly cells have telomerase activity, which is found in human embryonic stem cells [11]. In addition, at least a subpopulation of Wharton’s jelly cells cultured from umbilical cord explants expressed the c-kit receptor. In this study, we showed that Wharton’s jelly cells underwent changes in morphology and expressed neural-specific proteins when induced by an adaptation of the method of Woodbury et al. [29]. Therefore, cells from the gelatinous connective tissue of umbilical cord matrix may be an easily attainable source of multipotent stem cells that can be expanded in vitro, maintained in culture, and induced to differentiate into neural cells.
We found that NSE, a marker for neural stem cells, was expressed at nearly equal levels in treated and untreated Wharton’s jelly cells. While this result was somewhat surprising, it is consistent with results from bone marrow stromal cells, a source of adult mesenchymal stem cells [28, 29]. Woodbury et al. [29] also found that NSE was expressed in untreated bone marrow stromal cells, and that expression of NSE in those cells was increased by the induction protocol we used in the present study. In other work with bone marrow stromal cells, Sanchez-Ramos et al. [28] found that NeuN and GFAP, markers for early mature neurons and astrocytes, respectively, were expressed at similar levels in uninduced and bone marrow stromal cells induced to form neural cells by retinoic acid. Likewise, we found that the glial cell markers, GFAP and CNPase, were expressed at equivalent levels in treated and untreated Wharton’s jelly cells. Our results, along with the bone marrow stromal studies, suggest that mesenchymal stem cells express a number of neural proteins spontaneously and, perhaps, are primed to differentiate along a neural program.
Colonies of Wharton’s jelly cells also expressed NSE, c-kit, and even more intriguing, TH, a marker for catecholaminergic neurons. Therefore, we suggest that the colonies that arose spontaneously after Wharton’s jelly cells grew past confluency were neurosphere-like masses of cells. Further work is being done to characterize the types of cells that exist in these colonies and to explore whether they are neurospheres with a variety of different neural cell types present. c-kit is expressed in melanocyte precursors from neural crest [31], so expression of c-kit by colonies does not preclude their being neurospheres. Whether there is expression by the colonies of markers for non-neuronal cell lineages has yet to be determined.
Recently, other sources of postnatal stem cells have been identified that are capable of multipotential differentiation. Multipotent stem cells isolated from the dermis of mammalian skin can be expanded in culture, and differentiated into neurons and glia [26]. Astrocytes have also been isolated, expanded in culture and shown to form neurospheres composed of neurons, oligodendrocytes, and astrocytes [32]. Are these postnatal stem cells related? Wharton’s jelly was previously shown to be composed of myofibroblast-like stromal cells [30]. Our findings confirm this based on smooth muscle actin expression by the Wharton’s jelly cells. Myofibroblasts are important cells in growth, development, and repair found throughout the body and include bone marrow stromal cells, astrocytes, and pericytes [8]. This suggests that myofibroblasts may be a source of postnatal stem cells and/or they may be involved in secretion of cytokines and growth factors involved in proliferation and differentiation of closely associated stem cells. Importantly, the mixed population of cells in Wharton’s jelly may provide both stem cells and feeder cells, thus explaining why LIF is not required, as is the case for maintaining mouse embryonic stem cells in an undifferentiated state [9–11].
Work is under way to characterize the cell types present in Wharton’s jelly and to determine whether clonal lines of Wharton’s jelly cells can be established that maintain their capacity to proliferate and to differentiate into neural cells as well as other tissue types. Importantly, this will also establish whether neurons and glial cells can arise from a single clonal cell or whether they arise from different progenitor cells potentially found in the mixed population of cells derived from Wharton’s jelly. Also yet to be addressed is whether the telomerase activity of Wharton’s jelly cells results in tumorgenicity, as is the case for embryonic stem cells. Preliminary studies are under way to assess this potential by injecting Wharton’s jelly cells into nude mice. Thus far, there is no evidence of tumor formation by Wharton’s jelly cells injected into brain after 6 weeks (Weiss, submitted).
The potential for exploiting the capacity of stem cells to differentiate into mature neural cells holds much promise for treating a number of devastating neurological diseases. This premise is based upon a number of preliminary studies that use either neural cells derived from embryonic stem cells or neural stem cells. Embryonic-stem-cell-derived neurons that were transplanted into the injured adult striatum were found to differentiate into both dopaminergic and serotonergic neurons [33]. Studer et al. [34] reported similar results with neural stem cells after they were expanded in vitro. The neural stem cells were transplanted into the brain of a Parkinsonian rat, and they subsequently differentiated into dopaminergic neurons, resulting in alleviation of behavioral deficits. Indeed, neural stem cells appear to show tropism for pathology. In a study by Aboody et al. [35], neural stem cells targeted intracranial gliomas of adult brains when either implanted at areas distant from the tumor or applied intravascularly. Neural stem cells have also been shown to supply myelin basic protein to the shiverer mouse, which lacks this protein, when intracerebroventricular implantations of neural stem cells were done [36].
Although these initial studies are promising, there are drawbacks with the use of both embryonic stem cells and neural stem cells. The use of human embryonic stem cells is controversial and will likely remain so. Human neural stem cells are not readily accessible and grow slowly in culture [37]. These limitations emphasize the importance of identifying alternative sources of stem cells for treatment of neurological disorders. Based on the ability of Wharton’s jelly cells to differentiate into neural cells in vitro, as described here, and the ability of Wharton’s jelly cells to differentiate into neurons in vivo (Weiss et al., submitted), Wharton’s jelly cells may be an easily attainable and noncontroversial source of stem cells for the treatment of neurological diseases.
In summary, we show here that cells from Wharton’s jelly are a rich source of primitive cells that are readily expanded in culture and that can be induced to form neurons and glia. Clonal populations of human umbilical cord matrix cells are being established. The clonal cells will be characterized in terms of proliferative capacity, karyotype analysis, and expression of HLA antigens as well as their ability to differentiate into ectodermal, mesodermal, and endodermal lineages.
|
ACKNOWLEDGMENT |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsWharton’s Jelly Cells...DiscussionReferences |
|---|
This work was supported by the National Institutes of Health COBRE award 1 P20 RR15563, matching support from the State of Kansas, and the University of Kansas or Kansas State University (K.E.M.), NIH NS-34160 (M.L.W.), 02-451-j (D.D.), and 481326 (D.T.) from the Kansas Agricultural Experiment Station.
|
REFERENCES |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsWharton’s Jelly Cells...DiscussionReferences |
|---|
This article has been cited by other articles:
|
|
 |
|
  T.-S. Huang, J.-Y. Hsieh, Y.-H. Wu, C.-H. Jen, Y.-H. Tsuang, S.-H. Chiou, J. Partanen, H. Anderson, T. Jaatinen, Y.-H. Yu, et al. Functional Network Reconstruction Reveals Somatic Stemness Genetic Maps and Dedifferentiation-Like Transcriptome Reprogramming Induced by GATA2 Stem Cells, May 1, 2008; 26(5): 1186 - 1201. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. L. Troyer and M. L. Weiss Concise Review: Wharton's Jelly-Derived Cells Are a Primitive Stromal Cell Population Stem Cells, March 1, 2008; 26(3): 591 - 599. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Karahuseyinoglu, C. Kocaefe, D. Balci, E. Erdemli, and A. Can Functional Structure of Adipocytes Differentiated from Human Umbilical Cord Stroma-Derived Stem Cells Stem Cells, March 1, 2008; 26(3): 682 - 691. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Secco, E. Zucconi, N. M. Vieira, L. L.Q. Fogaca, A. Cerqueira, M. D. F. Carvalho, T. Jazedje, O. K. Okamoto, A. R. Muotri, and M. Zatz Multipotent Stem Cells from Umbilical Cord: Cord Is Richer than Blood! Stem Cells, January 1, 2008; 26(1): 146 - 150. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Can and S. Karahuseyinoglu Concise Review: Human Umbilical Cord Stroma with Regard to the Source of Fetus-Derived Stem Cells Stem Cells, November 1, 2007; 25(11): 2886 - 2895. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. S. Park, K. H. Jung, S. H. Kim, K. S. Kim, M. R. Choi, Y. Kim, and Y. G. Chai Functional Expression of Ion Channels in Mesenchymal Stem Cells Derived from Umbilical Cord Vein Stem Cells, August 1, 2007; 25(8): 2044 - 2052. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Baksh, R. Yao, and R. S. Tuan Comparison of Proliferative and Multilineage Differentiation Potential of Human Mesenchymal Stem Cells Derived from Umbilical Cord and Bone Marrow Stem Cells, June 1, 2007; 25(6): 1384 - 1392. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Karahuseyinoglu, O. Cinar, E. Kilic, F. Kara, G. G. Akay, D. O. Demiralp, A. Tukun, D. Uckan, and A. Can Biology of Stem Cells in Human Umbilical Cord Stroma: In Situ and In Vitro Surveys Stem Cells, February 1, 2007; 25(2): 319 - 331. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Jomura, M. Uy, K. Mitchell, R. Dallasen, C. J. Bode, and Y. Xu Potential Treatment of Cerebral Global Ischemia with Oct-4+ Umbilical Cord Matrix Cells Stem Cells, January 1, 2007; 25(1): 98 - 106. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. L. Weiss, S. Medicetty, A. R. Bledsoe, R. S. Rachakatla, M. Choi, S. Merchav, Y. Luo, M. S. Rao, G. Velagaleti, and D. Troyer Human Umbilical Cord Matrix Stem Cells: Preliminary Characterization and Effect of Transplantation in a Rodent Model of Parkinson's Disease Stem Cells, March 1, 2006; 24(3): 781 - 792. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M.-S. Tsai, S.-M. Hwang, Y.-L. Tsai, F.-C. Cheng, J.-L. Lee, and Y.-J. Chang Clonal Amniotic Fluid-Derived Stem Cells Express Characteristics of Both Mesenchymal and Neural Stem Cells Biol Reprod, March 1, 2006; 74(3): 545 - 551. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y.-S. Fu, Y.-C. Cheng, M.-Y. A. Lin, H. Cheng, P.-M. Chu, S.-C. Chou, Y.-H. Shih, M.-H. Ko, and M.-S. Sung Conversion of Human Umbilical Cord Mesenchymal Stem Cells in Wharton's Jelly to Dopaminergic Neurons In Vitro: Potential Therapeutic Application for Parkinsonism Stem Cells, January 1, 2006; 24(1): 115 - 124. [Abstract] [Full Text] [PDF]
|
|
|
|
fluorescein/
