Functional similarities among genes regulated by OCT4 in human mesenchymal and embryonic stem cells

Comprehensive transcriptome and immunophenotype analysis of renal and cardiac MSC-like populations supports strong congruence with bone marrow MSC despite maintenance of distinct identities

Cells resembling bone marrow mesenchymal stem cells (MSC) have been isolated from many organs but their functional relationships have not been thoroughly examined. Here we compared the immunophenotype, gene expression, multipotency and immunosuppressive potential of MSC-like colony-forming cells from adult murine bone marrow (bmMSC), kidney (kCFU-F) and heart (cCFU-F), cultured under uniform conditions. All populations showed classic MSC morphology and in vitro mesodermal multipotency. Of the two solid organ-specific CFU-F, only kCFU-F displayed suppression of T-cell alloreactivity in vitro, albeit to a lesser extent than bmMSC. Quantitative immunophenotyping using 81 phycoerythrin-conjugated CD antibodies demonstrated that all populations contained high percentages of cells expressing diagnostic MSC surface markers (Sca1, CD90.2, CD29, CD44), as well as others noted previously on murine MSC (CD24, CD49e, CD51, CD80, CD81, CD105). Illumina microarray expression profiling and bioinformatic analysis indicated a correlation of gene expression of 0.88-0.92 between pairwise comparisons. All populations expressed approximately 66% of genes in the pluripotency network (Plurinet), presumably reflecting their stem-like character. Furthermore, all populations expressed genes involved in immunomodulation, homing and tissue repair, suggesting these as conserved functions for MSC-like cells in solid organs. Despite this molecular congruence, strong biases in gene and protein expression and pathway activity were seen, suggesting organ-specific functions. Hence, tissue-derived MSC may also retain unique properties potentially rendering them more appropriate as cellular therapeutic agents for their organ of origin.

Three-dimensional spheroid culture of human gingiva-derived mesenchymal stem cells enhances mitigation of chemotherapy-induced oral mucositis

Mesenchymal stem cells (MSCs) are capable of regenerative and immunomodulatory functions in cell-based therapies in a variety of human diseases and injuries; however, their therapeutic efficacy and potential side effects remain major obstacles in clinical applications. We report here a 3D spheroid culture approach to optimize stem cell properties and therapeutic effects of human gingiva-derived mesenchymal stem cells (GMSCs) in mitigation of experimental oral mucositis. Under growth condition of ultra-low attachment, GMSCs spontaneously aggregated into 3D spheroids and exhibited distinct early stem cell phenotype characterized by elevated expression Stro-1 and CXC chemokine receptor 4 (CXCR-4) as well as OCT-4 and Nanog, 2 important transcriptional factors relevant to stem cell properties, and decreased expression of MSC-associated markers, including CD29, CD90, and CD105. Functionally, spheroid GMSCs are capable of enhanced multipotency and augmented secretion of several chemokines and cytokines relevant to cell migration, survival, and angiogenesis. More importantly, spheroid GMSCs expressed increased levels of reactive oxygen species, hypoxia-inducible factor (HIF)-1 and -2α, and manganese superoxide dismutase, which correlated with improved resistance to oxidative stress-induced apoptosis. Using an in vivo murine model of chemotherapy-induced oral mucositis, we demonstrated that spheroid-derived GMSCs possessed better therapeutic efficacy than their adherent cells in reversing body weight loss and promoting the regeneration of disrupted epithelial lining of the mucositic tongues. These findings suggest that 3D spheroid culture allows early stemness preservation and potentially precondition GMSCs for enhanced mitigation of oral mucositis.

Microenvironmental considerations in the application of human mesenchymal stem cells in regenerative therapies

The therapeutic utilization of stem cells has been ongoing for several decades, principally in the form of bone marrow (BM) transplants to treat various hematological disorders and other immune-related diseases. More recently, stem cells have been examined as a potential therapy for a multitude of other diseases and disorders, many of which are currently untreatable. One consideration that poses a formidable task for the successful clinical application of stem cells in new disease models is the impact of the host tissue microenvironment on the desired therapeutic outcome. In vitro, stem cells exist in surroundings directly controllable by the researcher to produce the desired cellular behavior. In vivo, the transplanted cells are exposed to a dynamic host microenvironment laden with soluble mediators and immunoreactive cells. In this review, we focus on the possible contribution by microenvironmental factors, and how these influences can be overcome in therapies utilizing mesenchymal stem cells (MSCs), such as for graft versus host disease, multiple sclerosis and ischemia among others. Specifically, we examine three ubiquitous microenvironmental factors, IL-1alpha/beta(,) TNFalpha, and SDF-1alpha, and consider how inhibitors and receptor antagonists to these molecules could be applied to increase the efficacy of MSC therapies while minimizing unforeseen harm to the patient.

Recent highlights on bone stem cells: a report from Bone Stem Cells 2009, and not only…

The use of stem cells has opened new prospects for the treatment of orthopaedic conditions characterized by large bone defects. However, many issues still exist to which answers are needed before routine, large-scale application becomes possible. Bone marrow stromal cells (MSC), which are clonogenic, multipotential precursors present in the bone marrow stroma, are generally employed for bone regeneration. Stem cells with multilineage differentiation similar to MSC have also been demonstrated in adipose tissue, peripheral blood, umbilical cord and amniotic fluid. Each source presents its own advantages and drawbacks. Unfortunately, no unique surface antigen is expressed by MSC, and this hampers simple MSC enrichment from heterogeneous populations. MSC are identified through a combination of physical, morphological and functional assays. Different in vitro and in vivo models have been described for the research on bone stem cells. These models should predict the in vivo bone healing capacity of MSC and if the induced osteogenesis is similar to the physiological one. Although stem cells offer an exciting possibility of a renewable source of cells and tissues for replacement, orthopaedic applications often represent case reports whereas controlled randomized trials are still lacking. Further biological aspects of bone stem cells should be elucidated and a general consensus on the best models, protocols and proper use of scaffolds and growth factors should be achieved.

Human Wharton's jelly stem cells have unique transcriptome profiles compared to human embryonic stem cells and other mesenchymal stem cells

The human umbilical cord that originates from the embryo is an extra-embryonic membrane and the Wharton's jelly within it is a rich source of stem cells (hWJSCs). It is not definitely known whether these cells behave as human embryonic stem cells (hESCs), human mesenchymal stem cells (hMSC) or both. They have the unique properties of high proliferation rates, wide multipotency, hypoimmunogenicity, do not induce teratomas and have anticancer properties. These advantages are important considerations for their use in cell based therapies and treatment of cancers. In a search for properties that confer these advantages we compared a detailed transcriptome profiling of hWJSCs using DNA microarrays with that of a panel of known hESCs, hMSCs and stromal cells. hWJSCs expressed low levels of the pluripotent embryonic stem cell markers including POUF1, NANOG, SOX2 and LIN28, thus explaining why they do not produce teratomas. Several cytokines were significantly upregulated in hWJSCs including IL12A which is associated with the induction of apoptosis, thus explaining their anticancer properties. When GO Biological Process analysis was compared between the various stem cell types, hWJSCs showed an increased expression of genes associated with the immune system, chemotaxis and cell death. The ability to modulate immune responses makes hWJSCs an important compatible stem cell source for transplantation therapy in allogeneic settings without immunorejection. The data in the present study which is the first detailed report on hWJSC transcriptomes provide a foundation for future functional studies where the exact mechanisms of these unique properties of hWJSCs can be confirmed.

A comprehensive characterization study of human bone marrow mscs with an emphasis on molecular and ultrastructural properties

Human bone marrow-derived mesenchymal stem cells (hBM-MSCs) continue to draw attention of researchers in the fields of basic science and medicine due to their indispensible regenerative, reparative, angiogenic, anti-apoptotic, and immunosuppressive properties, all of which collectively point out their enormous therapeutic potential. There is still, however, a need for further investigation of their characteristics to broaden their field of use and learn much more about how to control their fate and improve their therapeutic effectiveness. hBM-MSCs were extensively characterized in terms of their growth characteristics, genetic stability, and differentiation capability to the mesodermal and ectodermal cell lineages; a special emphasis was given to their phenotypic and ultrastructural properties. Expression of embryonic stem cell markers Oct4, Rex-1, FoxD-3, Sox2, and Nanog was shown with real-time PCR. Transmission electron microscopy revealed the ultrastructural characteristics of hBM-MSCs; they had pale, irregularly shaped and large euchromatic nuclei, and two distinct areas in their cytoplasm: an intensely stained inner zone rich in mitochondria and rough endoplasmic reticulum (rER) with dilated cisternae and a relatively peripheral zone poor in organelles. hBM-MSCs expressed adipogenic (adipophilin and PPARγ), myogenic (desmin, myogenin, α-SMA), neurogenic (γ-enolase, MAP2a,b, c-fos, nestin, NF-H, NF-L, GFAP, β3-tubulin), osteogenic (osteonectin, osteocalcin, osteopontin, Runx-2, type I collagen), and chondrogenic (type II collagen, SOX9) markers either at RNA or protein level even under basal conditions, without any stimulation towards differentiation. The differentiation potential of hBM-MSCs to adipogenic, osteogenic, and neurogenic lineages was shown by using the relevant differentiation factors.

NANOG has a role in mesenchymal stem cells' immunomodulatory effect

It is well known that terminally differentiated cells derived from mesenchymal stem cells (MSCs) will lose the immunomodulation capacity. NANOG is known to be a core transcription factor in the maintenance of stem cell specific features or stemness. To evaluate whether NANOG was involved in the immunomodulation effects of MSCs, MSCs' immunomodulation capacity on lymphocyte activation and proliferation before or after endogenous NANOG interference was investigated. We found that MSCs' inhibitory effects on lymphocyte activation and proliferation was significantly weakened after NANOG knockdown. In addition, NANOG RNAi and chromatin immunoprecipitation experiments showed that NANOG suppressed the expression and secretion of DKK-1, transforming growth factor-beta1 (TGF-β1), TGF-β2, and TGF-β3, which are all important factors mediating MSCs' immunomodulation capacity. Based on these data, we propose that NANOG plays an important role in maintaining the immunomodulation functions of MSCs by regulating the expression and secretion of TGF-β1, TGF-β2, TGF-β3, and DKK-1.

Effects of donor age, gender, and in vitro cellular aging on the phenotypic, functional, and molecular characteristics of mouse bone marrow-derived mesenchymal stem cells

Mesenchymal stem cells (MSCs) are a very important adult stem cell population with a multitude of potential applications in regenerative medicine. The thorough characterization of the bone marrow MSC (BM-MSC) population derived from the BALB/c species was essential, considering the significance of the murine model amongst animal models. In the present study, we examined the effect of gender, age, and in vitro culture on the basic properties (proliferation, differentiation, and immunosuppressive potential) of BM-MSCs. We found a decline in the progenitor frequencies from the BM of adult mice, lower MSC frequencies in all female donors, and an increase in the BM-MSC proliferation rate upon in vitro propagation. We also examined BM-MSCs for the expression of the 3 major embryonic stem cell transcription factors, Oct3/4, Sox-2, and Nanog, as well as 2 mRNA binding proteins, coding region determinant binding protein/insulin-like growth factor 2 mRNA binding protein 1 (Crd-bp/Imp1) and Deleted in azoospermia-like (Dazl), which are expressed in primitive stem cells, umbilical cord blood-hematopoietic stem cells and amniotic fluid stem cells, respectively. Further, it has been reported that these 2 genes are critical for embryonic development. In this study, therefore, we report, for the first time, the expression of Crd-bp/Imp1 and Dazl in BM-MSCs. Dazl, Oct3/4, and Sox2 were detected in relatively low levels in contrast to Crd-bp/Imp1, its major target c-Myc, as well as Nanog, which were expressed redundantly, irrespective of sex, donor age, or in vitro passaging. These findings could further support the extrinsic theory of aging of the MSC population and the potential implication of embryonic genes in adult stem cell physiology.

Mesenchymal stem cells from bone marrow show a stronger stimulating effect on megakaryocyte progenitor expansion than those from non-hematopoietic tissues

In order to evaluate whether mesenchymal stem cells (MSCs) from non-hematopoietic tissues are able to regulate megakaryocytopoiesis, we identified human MSCs from adult bone marrow (ABM), fetal pancreas (FPan) and umbilical cord (UC), and their abilities to support megakaryocyte (MK) differentiation from CD34(+) hematopoietic progenitor cells (HPCs) were comparatively studied. First, MSCs were isolated from ABM, FPan and UC then their growth kinetics, molecular characterization and mesodermal differentiation capacity were determined. ABM-MSCs, FPan-MSCs and UC-MSCs were irradiated and cocultured with human umbilical cord blood (UCB) CD34(+) cells, and the expansion efficiency of MK progenitor cells and MK formation were analysed and compared. Finally, SCF, IL-6 and GM-CSF expression by the three types of MSCs were also examined. Our results showed that FPan-MSCs and UC-MSCs shared most of the characteristic of ABM-MSCs, including morphology, immunophenotype, adipogenic and osteogenic differentiation potentials. Compared with ABM-MSCs, fetal MSCs had higher proliferative capacity. After 7 days' coculture, the maximal production of CD34(+)/CD41a(+) cells was obtained in a group of CD34(+) HPCs + ABM-MSCs. Furthermore, this group produced more MK colonies than other groups (p < 0.05). Surface antigen and ploidy analysis morphological observation demonstrated that a proportion of expanded cells in each group differentiated into mature MKs. ABM-MSCs, FPan-MSCs and UC-MSCs were revealed to express SCF, IL-6 and GM-CSF at mRNA level. We conclude that FPan-MSCs and UC-MSCs have the ability to promote megakaryocytopoiesis, while ABM-MSCs expand more MK progenitor cells from CD34(+) HPCs than MSCs from non-hematopoietic tissues and CD34(+) cells alone.

The role of microRNAs in self-renewal and differentiation of mesenchymal stem cells

MicroRNAs (miRNAs) are short non-coding RNAs involved in post-trascriptional regulation of gene expression and diverse biological activities. They are crucial for self-renewal and behavior of embryonic stem cells, but their role in mesenchymal stem cells has been poorly understood. Recently emerging evidence suggests that miRNAs are closely involved in controlling key steps of mesenchymal stem cell differentiation into certain cell lineages. This review focuses on miRNAs identified recently that regulate mesenchymal stem cell differentiation and other activities.

Dental pulp and dentin tissue engineering and regeneration: advancement and challenge

Hard tissue is difficult to repair especially dental structures. Tooth enamel is incapable of self-repairing whereas dentin and cementum can regenerate with limited capacity. Enamel and dentin are commonly under the attack by caries. Extensive forms of caries destroy enamel and dentin and can lead to dental pulp infection. Entire pulp amputation followed by the pulp space disinfection and filling with an artificial rubber-like material is employed to treat the infection -- commonly known as root canal or endodontic therapy. Regeneration of dentin relies on having vital pulps; however, regeneration of pulp tissue has been difficult as the tissue is encased in dentin without collateral blood supply except from the root apical end. With the advent of modern tissue engineering concept and the discovery of dental stem cells, regeneration of pulp and dentin has been tested. This article will review the recent endeavor on pulp and dentin tissue engineering and regeneration. The prospective outcomes of current advancements and challenges in this line of research are discussed.

Bone marrow mesenchymal stem cells: historical overview and concepts

This review describes the historical emergence of the concept of bone marrow mesenchymal stem cells (MSCs), summarizing data on Wolf and Trentin's hematopoietic inductive microenvironment; Dexter's hematopoiesis-supportive stromal cells; Friedenstein's osteogenic cells; and Pittenger's trilineal osteoblastic, chondrocytic, and adipocytic precursors; to finally introduce the specific bone marrow mesenchymal stem cells with differentiation potential to four lineages (mesenchymal and vascular smooth muscle lineages), and stromal and immunomodulatory capacities. Two points are the object of detailed discussion. The first point envisions the stem cell attributes (multipotentiality, self-renewal, tissue regeneration, population heterogeneity, plasticity, and lineage priming) compared with that of the paradigmatic hematopoietic stem cell. In the second point, we discuss the possible existence of bone marrow cells with greater differentiation potential, eventually pluripotential cells. The latter point raises the issues of cell fusion, reprogramming, or selection under nonstandardized conditions of rare populations of neuroectodermal origin, or of cells that had undergone mesenchymal-to-epithelial transition. In the last section, we review data on MSC senescence and possible malignant transformation secondary to extensive culture, gene transfer of telomerase, or mutations such as leading to Ewing's sarcoma. The set of data leads to the conclusion that bone marrow MSCs constitute a specific adult tissue stem cell population. The multiple characteristics of this stem cell type account for the versatility of the mechanisms of injured tissue repair. Although MSC administration may be extremely useful in a number of clinical applications, their transplantation is not without risks that must not be overlooked when developing cell therapy protocols.

Microscale versus nanoscale scaffold architecture for mesenchymal stem cell chondrogenesis

Nanofiber scaffolds, produced by the electrospinning technique, have gained widespread attention in tissue engineering due to their morphological similarities to the native extracellular matrix. For cartilage repair, studies have examined their feasibility; however these studies have been limited, excluding the influence of other scaffold design features. This study evaluated the effect of scaffold design, specifically examining a range of nano to micron-sized fibers and resulting pore size and mechanical properties, on human mesenchymal stem cells (MSCs) derived from the adult bone marrow during chondrogenesis. MSC differentiation was examined on these scaffolds with an emphasis on temporal gene expression of chondrogenic markers and the pluripotent gene, Sox2, which has yet to be explored for MSCs during chondrogenesis and in combination with tissue engineering scaffolds. Chondrogenic markers of aggrecan, chondroadherin, sox9, and collagen type II were highest for cells on micron-sized fibers (5 and 9 μm) with pore sizes of 27 and 29 μm, respectively, in comparison to cells on nano-sized fibers (300 nm and 600 to 1400 nm) having pore sizes of 2 and 3 μm, respectively. Undifferentiated MSCs expressed high levels of the Sox2 gene but displayed negligible levels on all scaffolds with or without the presence of inductive factors, suggesting that the physical features of the scaffold play an important role in differentiation. Micron-sized fibers with large pore structures and mechanical properties comparable to the cartilage ECM enhanced chondrogenesis, demonstrating architectural features as well as mechanical properties of electrospun fibrous scaffolds enhance differentiation.

Bone marrow stem cell derived paracrine factors for regenerative medicine: current perspectives and therapeutic potential

During the past several years, there has been intense research in the field of bone marrow-derived stem cell (BMSC) therapy to facilitate its translation into clinical setting. Although a lot has been accomplished, plenty of challenges lie ahead. Furthermore, there is a growing body of evidence showing that administration of BMSC-derived conditioned media (BMSC-CM) can recapitulate the beneficial effects observed after stem cell therapy. BMSCs produce a wide range of cytokines and chemokines that have, until now, shown extensive therapeutic potential. These paracrine mechanisms could be as diverse as stimulating receptor-mediated survival pathways, inducing stem cell homing and differentiation or regulating the anti-inflammatory effects in wounded areas. The current review reflects the rapid shift of interest from BMSC to BMSC-CM to alleviate many logistical and technical issues regarding cell therapy and evaluates its future potential as an effective regenerative therapy.

Concise review: isoforms of OCT4 contribute to the confusing diversity in stem cell biology

The human OCT4 gene can generate at least three transcripts (OCT4A, OCT4B, and OCT4B1) and four protein isoforms (OCT4A, OCT4B-190, OCT4B-265, and OCT4B-164) by alternative splicing and alternative translation initiation. OCT4A is a transcription factor responsible for the pluripotency properties of embryonic stem (ES) cells. While OCT4B cannot sustain ES cell self-renewal, it may respond to cell stresses. Yet, the function of OCT4B1 is still unclear. Lack of distinction of OCT4 isoforms could lead to confusions and controversies on OCT4 in various tissues and cells. One important issue we emphasize in this review article is that alternatively spliced transcripts and alternative translation products of OCT4 exhibit diverse expression patterns and functions. Furthermore, simple approaches and methods to detect and distinguish OCT4 isoforms are discussed. This article underscores the importance of identifying and discriminating the expression and functions of OCT4 isoforms in stem cell research.

Mesenchymal stem cells in the pathogenesis and therapy of breast cancer

Mesenchymal stem cells (MSCs) are a heterogeneous mix of stromal stem cells that can give rise to cells of mesodermal lineages, namely adipocytes, osteocytes and chondrocytes. They can home to sites of injury where they promote the repair and regeneration of damaged tissues. MSCs also home to sites of tumorigenesis, and as such, are utilized as efficient cellular vehicles for the delivery of anti-neoplastic therapeutics. Recently, MSCs within the tumor microenvironment have been shown to contribute to the desmoplastic reaction and to facilitate tumor formation and progression, sparking renewed interest in their pro-tumorigenic attributes and their roles as tumor stromal cells. Here, we describe the evidence linking MSCs to inflammatory processes and breast cancer development, and discuss their newly discovered physiological roles in the context of the tumor microenvironment.

The generation of programmable cells of monocytic origin involves partial repression of monocyte/macrophage markers and reactivation of pluripotency genes

We have recently demonstrated that peripheral blood monocytes can be differentiated in vitro into hepatocyte-like cells using appropriate differentiation media. Phenotype conversion required prior in vitro culture in the presence of M-CSF, IL-3, and human serum, during which the cells acquired a state of plasticity, so were termed "programmable cells of monocytic origin" (PCMO). Here, we have further characterized the process of PCMO generation with respect to markers of monocyte-to-macrophage transition and pluripotency. During a 6-day culture period, various monocyte/macrophage differentiation markers were down-regulated being indicative of a process of partial dedifferentiation. Dedifferentiation and hepatic redifferentiation also proceeded in highly purified monocyte preparations, albeit with different kinetics, suggesting that the presence of nonmonocytes, or soluble factors derived from them, is not essential in order for monocytes to acquire a multipotent state. PCMOs expressed various markers of human embryonic stem cells with early induction of NANOG and OCT4. Expression of the pluripotency-associated OCT4A isoform was paralleled by a global rise in histone H3 methylation on Lys-4, a marker of active chromatin, and coincided with peak sensitivity to tissue-specific differentiation. These results show that peripheral blood monocytes can be induced in vitro to transiently acquire stem cell-like properties and concomitantly a state of increased differentiation potential toward the hepatocytic phenotype.

Pluripotency regulators in human mesenchymal stem cells: expression of NANOG but not of OCT-4 and SOX-2

Mesenchymal stem cells (MSCs) are adult multipotent cells able to differentiate toward mature mesodermal lineages. In spite of more than a decade of investigation, little is known about the molecular mechanisms regulating the undifferentiated state and the identity of distinct functional subpopulations in these cells. Transcription factors that regulate the maintenance of the pluripotent state in embryonic stem cells, including NANOG, SOX2, and OCT4, have been proposed to play a similar role also in adult stem cells, although with conflicting results. We performed a critical evaluation of expression of these 3 transcription factors and found that NANOG, but not OCT-4 and SOX-2, is expressed in cultured human adult MSCs. Actually, NANOG was not expressed in freshly isolated MSCs, but was detected only after in vitro culture. NANOG was detected only in proliferating cells, but not in MSCs induced to differentiate. The percentage of cells expressing NANOG was maintained throughout early passages of MSCs, but then started to decrease in late passages in MSCs from adipose tissue and heart but not from bone marrow. However, the number of NANOG-expressing cells did not associate with the proliferative and differentiative capabilities of MSC populations, neither its expression appeared to identify cells having stem or progenitor cell properties. Accordingly, we propose that activation of NANOG expression in MSCs is associated with, although cannot directly regulate, the transition from in vivo quiescence to adaptation to in vitro growth conditions.

Expression profile of the embryonic markers nanog, OCT-4, SSEA-1, SSEA-4, and frizzled-9 receptor in human periodontal ligament mesenchymal stem cells

Mesenchymal stem cells (MSCs) are self-renewing cells with the ability to differentiate into various mesodermal-derived tissues. Recently, we have identified in adult human periodontal ligament (PDL) a population of stem cells (PDL-MSCs) with the ability to differentiate into osteoblasts and adipocytes. The aim of the present work was to further characterize this population and the expression profile of its cells. To achieve our objective we have used flow cytometry, magnetic cell sorting, cytokine antibody array, and light and electron microscope immunostaining. Our results show that the PDL-MSCs contain a subpopulation of frizzled-9 (CD349) positive cells expressing a panel of key mesenchymal and embryonic markers including CD10, CD26, CD29, CD44, CD73, CD90, CD105, CD166, SSEA-1, and SSEA-4. They are additionally positive for nanog and Oct-4; two critical transcription factors directing self-renewal and pluripotency of embryonic stem cells, and they also express the cytokines EGF and IP-10. The presence of nanog, Oct-4, SSEA-1, and SSEA-4 suggests that PDL-MSCs are less differentiated than bone marrow-derived MSCs. Taken together, these data indicate the presence of immature MSCs in PDL and suggest that the frizzled-9/Wnt pathway plays an important role in regulating proliferation and differentiation of these cells.

Human mesenchymal stem cells: Influence of oxygen pressure on proliferation and chondrogenic differentiation in fibrin glue in vitro

Tissue engineering using biomaterials is a promising solution for cartilage replacement. The purpose of this study was to investigate whether the fibrin sealant Tissucol(R) provides a suitable scaffold for re-implanting stem cells during chondrogenic replacement therapy. Pluripotent stem cells were isolated from adult human bone marrow (hMSCs), cultured and characterized by FACS (CD105+/CD106+, CD45-/CD14-/CD34-). A large-holed porous hMSC-containing fibrin matrix was built that allowed hMSCs to survive throughout the period of culture (42 days) in either proliferation or chondrogenic differentiation medium under normoxic (21% O2) or hypoxic (3% O2) conditions. Morphology (as determined by electron microscopy) and proliferation (Ki67 staining) of the embedded hMSCs did not markedly vary under normoxic and hypoxic culture even after 42 days in culture. The stem cell marker Oct-4 was expressed during the whole culture period. Under chondrogenic differentiation conditions, especially under hypoxic conditions, we observed rounded chondrocyte-like cell types and a chondral phenotype assessed by mRNA expression of collagen II and Alcian blue staining. hMSCs seeded into large-holed porous preparations of Tissucol survive, proliferate and keep their stem cell character. Furthermore, culturing the cells in a corresponding medium induces chondrogenic differentiation, which could be remarkably and significantly enhanced under hypoxic conditions.

Activin A expression regulates multipotency of mesenchymal progenitor cells

INTRODUCTION

Bone marrow (BM) stroma currently represents the most common and investigated source of mesenchymal progenitor cells (MPCs); however, comparable adult progenitor or stem cells have also been isolated from a wide variety of tissues. This study aims to assess the functional similarities of MPCs from different tissues and to identify specific factor(s) related to their multipotency.

METHODS

For this purpose, we directly compared MPCs isolated from different adult tissues, including bone marrow, tonsil, muscle, and dental pulp. We first examined and compared proliferation rates, immunomodulatory properties, and multidifferentiation potential of these MPCs in vitro. Next, we specifically evaluated activin A expression profile and activin A:follistatin ratio in MPCs from the four sources.

RESULTS

The multidifferentiation potential of the MPCs is correlated with activin A level and/or the activin A:follistatin ratio. Interestingly, by siRNA-mediated activin A knockdown, activin A was shown to be required for the chondrogenic and osteogenic differentiation of MPCs. These findings strongly suggest that activin A has a pivotal differentiation-related role in the early stages of chondrogenesis and osteogenesis while inhibiting adipogenesis of MPCs.

CONCLUSIONS

This comparative analysis of MPCs from different tissue sources also identifies bone marrow-derived MPCs as the most potent MPCs in terms of multilineage differentiation and immunosuppression, two key requirements in cell-based regenerative medicine. In addition, this study implicates the significance of activin A as a functional marker of MPC identity.

Do stem-like cells play a role in drug resistance of sarcomas?

Stem cells are defined by their unique characteristics, which include their abilities to self-renew and differentiate. Normal somatic stem cells have been isolated from various tissues such as bone marrow, adipose tissue, mammary glands and the nervous system. They are considered naturally resistant to chemotherapeutic agents because they express high levels of membrane transporter molecules, detoxifying enzymes and DNA repair proteins. Several recent studies have identified the presence of side populations in various cancer tissues, the so-called 'cancer stem cells', which are defined as the counterparts of stem cells in tumor tissues. These cancer stem cells possess stem-like properties, such as self-renewal and differentiation abilities, as well as playing a role in tumor initiation. Most sarcomas, which are thought to originate from mesenchymal stem cells, are highly malignant and approximately 30-40% of them show local and/or distant relapse (metastasis), even in the case of relatively chemosensitive tumors such as osteosarcomas and Ewing sarcomas. Several studies have suggested the presence of stem-like cell populations in sarcomas, based on their tumorigenicity and drug resistance. This review explores the issues of drug resistance of cancer stem cells in sarcomas and the possibilities of targeting cancer stem cells for the future treatment of sarcomas.

Non cell-autonomous reprogramming of adult ocular progenitors: generation of pluripotent stem cells without exogenous transcription factors

Direct reprogramming of differentiated cells to induced pluripotent stem (iPS) cells by ectopic expression of defined transcription factors (TFs) represents a significant breakthrough towards the use of stem cells in regenerative medicine (Takahashi and Yamanaka Cell 2006;126:663-676). However, the virus-mediated expression of exogenous transcription factors could be potentially harmful and, therefore, represents a barrier to the clinical use of iPS cells. Several approaches, ranging from plasmid-mediated TF expression to introduction of recombinant TFs (Yamanaka Cell 2009;137:13-17; Zhou, Wu, Joo et al. Cell Stem Cell 2009;4:381-384), have been reported to address the risk associated with viral integration. We describe an alternative strategy of reprogramming somatic progenitors entirely through the recruitment of endogenous genes without the introduction of genetic materials or exogenous factors. To this end, we reprogrammed accessible and renewable progenitors from the limbal epithelium of adult rat eye by microenvironment-based induction of endogenous iPS cell genes. Non cell-autonomous reprogramming generates cells that are pluripotent and capable of differentiating into functional neurons, cardiomyocytes, and hepatocytes, which may facilitate autologous cell therapy to treat degenerative diseases.

Embryonic stem cell marker expression pattern in human mesenchymal stem cells derived from bone marrow, adipose tissue, heart and dermis

Mesenchymal stem cells (MSCs) have been isolated from a variety of human tissues, e.g., bone marrow, adipose tissue, dermis, hair follicles, heart, liver, spleen, dental pulp. Due to their immunomodulatory and regenerative potential MSCs have shown promising results in preclinical and clinical studies for a variety of conditions, such as graft versus host disease (GvHD), Crohn's disease, osteogenesis imperfecta, cartilage damage and myocardial infarction. MSC cultures are composed of heterogeneous cell populations. Complications in defining MSC arise from the fact that different laboratories have employed different tissue sources, extraction, and cultivation methods. Although cell-surface antigens of MSCs have been extensively explored, there is no conclusive evidence that unique stem cells markers are associated with these adult cells. Therefore the aim of this study was to examine expression of embryonic stem cell markers Oct4, Nanog, SOX2, alkaline phosphatase and SSEA-4 in adult mesenchymal stem cell populations derived from bone marrow, adipose tissue, dermis and heart. Furthermore, we tested whether human mesenchymal stem cells preserve tissue-specific differences under in vitro culture conditions. We found that bone marrow MSCs express embryonic stem cell markers Oct4, Nanog, alkaline phosphatase and SSEA-4, adipose tissue and dermis MSCs express Oct4, Nanog, SOX2, alkaline phosphatase and SSEA-4, whereas heart MSCs express Oct4, Nanog, SOX2 and SSEA-4. Our results also indicate that human adult mesenchymal stem cells preserve tissue-specific differences under in vitro culture conditions during early passages, as shown by distinct germ layer and embryonic stem cell marker expression patterns. Studies are now needed to determine the functional role of embryonic stem cell markers Oct4, Nanog and SOX2 in adult human MSCs.

Isolation and differentiation of chicken mesenchymal stem cells from bone marrow

Mesenchymal stem cells (MSCs) are multipotent progenitor cells found in bone marrow that have the capacity of differentiating into bone, cartilage, fat, muscle, and other tissues. Chicken MSCs were isolated from 1- to 14-day-old chickens. Microscopically, the cultured cells showed morphology resembling fibroblasts and divided actively. Chicken MSCs expressed the transcription factors PouV, Sox2, and Nanog, which have been shown to be critical for stem cell self-renewal and pluripotency. The multilineage differentiation potential of chicken MSCs was revealed by their ability to undergo adipogenic, osteogenic, and chondrogenic differentiation. Like mammalian MSCs, chicken MSCs also had immunoregulatory activity and inhibited in vitro mitogenic response of T cells. The inhibition of mitogenic response of T cells correlated with the production of nitric oxide (NO) in cultures containing MSCs and T cells. Our data show for the first time that MSCs can be isolated from postnatal chicken bone marrow and these cells are capable of in vitro multiplication and multilineage differentiation, thus making them a suitable model in the field of stem cell research.

Mesenchymal stem cells derived from human gingiva are capable of immunomodulatory functions and ameliorate inflammation-related tissue destruction in experimental colitis

Aside from the well-established self-renewal and multipotent differentiation properties, mesenchymal stem cells exhibit both immunomodulatory and anti-inflammatory roles in several experimental autoimmune and inflammatory diseases. In this study, we isolated a new population of stem cells from human gingiva, a tissue source easily accessible from the oral cavity, namely, gingiva-derived mesenchymal stem cells (GMSCs), which exhibited clonogenicity, self-renewal, and multipotent differentiation capacities. Most importantly, GMSCs were capable of immunomodulatory functions, specifically suppressed peripheral blood lymphocyte proliferation, induced expression of a wide panel of immunosuppressive factors including IL-10, IDO, inducible NO synthase (iNOS), and cyclooxygenase 2 (COX-2) in response to the inflammatory cytokine, IFN-gamma. Cell-based therapy using systemic infusion of GMSCs in experimental colitis significantly ameliorated both clinical and histopathological severity of the colonic inflammation, restored the injured gastrointestinal mucosal tissues, reversed diarrhea and weight loss, and suppressed the overall disease activity in mice. The therapeutic effect of GMSCs was mediated, in part, by the suppression of inflammatory infiltrates and inflammatory cytokines/mediators and the increased infiltration of regulatory T cells and the expression of anti-inflammatory cytokine IL-10 at the colonic sites. Taken together, GMSCs can function as an immunomodulatory and anti-inflammatory component of the immune system in vivo and is a promising cell source for cell-based treatment in experimental inflammatory diseases.

Upregulation of Oct-4 isoforms in pulmonary artery smooth muscle cells from patients with pulmonary arterial hypertension

Oct-4 is a transcription factor considered to be one of the defining pluripotency markers in embryonic stem cells. Its expression has also been demonstrated in adult stem cells, tumorigenic cells, and, most recently and controversially, in somatic cells. Oct-4 pseudogenes also contribute to carcinogenesis. Oct-4 may be involved in the excessive proliferation of pulmonary arterial smooth muscle cells (PASMC) in patients with idiopathic pulmonary arterial hypertension (IPAH), contributing to the pathogenesis of IPAH. In this study, we show that Oct-4 isoforms are upregulated in IPAH-PASMC. Human embryonic stem cells (H9 line) and human PASMC from normotensive subjects were used throughout the investigation as positive and negative controls. In addition to significant upregulation of Oct-4 in a population of IPAH-PASMC, HIF-2alpha, a hypoxia-inducible transcription factor that has been shown to bind to the Oct-4 promoter and induces its expression and transcriptional activity, was also increased. Interestingly, a substantial upregulation of Oct-4 isoforms and HIF-2alpha was also observed in normal PASMC exposed to chronic hypoxia. In conclusion, the data suggest that both Oct-4 isoforms are upregulated and potentially have a significant role in the development of vascular abnormalities associated with the pathogenesis of IPAH and in pulmonary hypertension triggered by chronic hypoxia.

Anthracycline cardiomyopathy is mediated by depletion of the cardiac stem cell pool and is rescued by restoration of progenitor cell function

BACKGROUND

Anthracyclines are the most effective drugs available in the treatment of neoplastic diseases; however, they have profound consequences on the structure and function of the heart, which over time cause a cardiomyopathy that leads to congestive heart failure.

METHODS AND RESULTS

Administration of doxorubicin in rats led to a dilated myopathy, heart failure, and death. To test whether the effects of doxorubicin on cardiac anatomy and function were mediated by alterations in cardiac progenitor cells (CPCs), these cells were exposed to the anthracycline, which increased the formation of reactive oxygen species and caused increases in DNA damage, expression of p53, telomere attrition, and apoptosis. Additionally, doxorubicin resulted in cell-cycle arrest at the G2/M transition, which led to a significant decrease in CPC growth. Doxorubicin elicited multiple molecular adaptations; the massive apoptotic death that occurred in CPCs in the presence of anthracycline imposed on the surviving CPC pool the activation of several pathways aimed at preservation of the primitive state, cell division, lineage differentiation, and repair of damaged DNA. To establish whether delivery of syngeneic progenitor cells opposed the progression of doxorubicin cardiotoxicity, enhanced green fluorescent protein-labeled CPCs were injected in the failing myocardium; this treatment promoted regeneration of cardiomyocytes and vascular structures, which improved ventricular performance and rate of animal survival.

CONCLUSIONS

Our results raise the possibility that autologous CPCs can be obtained before antineoplastic drugs are given to cancer patients and subsequently administered to individuals who are particularly sensitive to the cardiotoxicity of these agents for prevention or management of heart failure.

Pulp and dentin tissue engineering and regeneration: current progress

Dental pulp tissue is vulnerable to infection. Entire pulp amputation followed by pulp-space disinfection and filling with an artificial rubber-like material is employed to treat the infection - commonly known as root-canal therapy. Regeneration of pulp tissue has been difficult as the tissue is encased in dentin without collateral blood supply except from the root apical end. However, with the advent of the concept of modern tissue engineering and the discovery of dental stem cells, regeneration of pulp and dentin has been tested. This article will review the early attempts to regenerate pulp tissue and the current endeavor of pulp and dentin tissue engineering, and regeneration. The prospective outcome of the current advancement in this line of research will be discussed.

Mesenchymal stem cells derived from dental tissues vs. those from other sources: their biology and role in regenerative medicine

To date, 5 different human dental stem/progenitor cells have been isolated and characterized: dental pulp stem cells (DPSCs), stem cells from exfoliated deciduous teeth (SHED), periodontal ligament stem cells (PDLSCs), stem cells from apical papilla (SCAP), and dental follicle progenitor cells (DFPCs). These postnatal populations have mesenchymal-stem-cell-like (MSC) qualities, including the capacity for self-renewal and multilineage differentiation potential. MSCs derived from bone marrow (BMMSCs) are capable of giving rise to various lineages of cells, such as osteogenic, chondrogenic, adipogenic, myogenic, and neurogenic cells. The dental-tissue-derived stem cells are isolated from specialized tissue with potent capacities to differentiate into odontogenic cells. However, they also have the ability to give rise to other cell lineages similar to, but different in potency from, that of BMMSCs. This article will review the isolation and characterization of the properties of different dental MSC-like populations in comparison with those of other MSCs, such as BMMSCs. Important issues in stem cell biology, such as stem cell niche, homing, and immunoregulation, will also be discussed.

Effects of ectopic Nanog and Oct4 overexpression on mesenchymal stem cells

Mesenchymal stem cells (MSCs) represent a source of pluripotent cells that are already in various phases of clinical application. However, the use of MSCs in tissue engineering has been hampered largely due to their limitations, including low proliferation, finite life span, and gradual loss of their stem cell properties during ex vivo expansion. Nanog and Oct4 are key transcription factors essential to the pluripotent and self-renewing phenotypes of undifferentiated embryonic stem cells (ESCs). To determine whether Nanog and Oct4 improve human bone marrow-MSC quality, we therefore established stable Nanog and Oct4 overexpressing MSCs using a lentiviral system and showed that this promoted cell proliferation and enhanced colony formation of MSCs. In differentiating MSCs, Nanog, and Oct4, overexpression had converse effects on adipogenesis of MSCs and Nanog overexpression slowed down adipogenesis, whereas Oct4 overexpression improved adipogenesis. Nanog and Oct4 overexpression both improved chondrogenesis. Microarray data showed many differences in transcriptional targets in undifferentiated MSCs overexpressing Nanog and Oct4. These results provide insight into the improvement of the stemness of MSCs by genetic modification with stemness-related genes.

Novel sources of fetal stem cells: where do they fit on the developmental continuum?

The recent isolation of fetal stem cells from several sources either at the early stages of development or during the later trimesters of gestation, sharing similar growth kinetics and expressing pluripotency markers, provides strong support to the notion that these cells may be biologically closer to embryonic stem cells, actually representing intermediates between embryonic stem cells and adult mesenchymal stem cells, regarding proliferation rates and plasticity features, and thus able to confer an advantage over postnatal mesenchymal stem cells derived from conventional adult sources such as bone marrow. This conclusion has been strengthened by the different pattern of growth potential between the two stage-specific types of sources, as assessed by transcriptomic and proteomic analysis. A series of recent studies regarding the numerous novel features of fetal stem cells has reignited our interest in the field of stem-cell biology and in the possibilities for the eventual repair of damaged organs and the generation of in vitro tissues on biomimetic scaffolds for transplantation. These studies, employing elegant approaches and novel technologies, have provided new insights regarding the nature and the potential of fetal stem cells derived from placenta, amniotic fluid, amnion or umbilical cord. In this update, we highlight the major progression that has occurred in fetal stem-cell biology and discuss the most important areas for future investigation in the field of regenerative medicine.

Preparation and in vitro evaluation of plasma-sprayed Mg(2)SiO(4) coating on titanium alloy

In this paper, chemically synthesized Mg(2)SiO(4) (MS) powder was plasma-sprayed onto a titanium alloy substrate to evaluate its application potentials in biomedicine. The phase composition and surface morphology of the MS coating were analyzed. Results showed that the MS coating was composed mainly of Mg(2)SiO(4) phase, with a small amount of MgO and glass phases. Mechanical testing showed that the coating exhibited good adhesion strength to the substrate due to the close thermal expansion coefficient between the MS ceramic and the titanium alloy substrate. The measured bonding strength was as high as 41.5+/-5.3MPa, which is much higher than the traditional HA coating. In vitro cytocompatibility evaluation of the MS coating was performed using canine bone marrow stem cells (MSCs). The MSCs exhibited good adhesion, proliferation and differentiation behavior on the MS coating surface, which can be explained by the high protein adsorption capability of the MS coating, as well as the stimulatory effects of Mg and Si ions released from the coating. The proliferation rate of the MSCs on MS coating was very close to that on the hydroxylapatite (HA) coating. Alkaline phosphatase (ALP) activity analysis demonstrated that the ALP level of the MSCs on the MS coating remained high even after 21days, implying that the surface characteristics of the coating are beneficial for the differentiation of MSCs. In summary, our results suggest that MS coating might be a new approach to prepare bone implants.

Tracing the stemness of porcine skin-derived progenitors (pSKP) back to specific marker gene expression

Multipotent skin-derived progenitors (SKP) can produce both neural and mesodermal progeny in vitro, sharing the characteristics of embryonic neural crest stem cells. However, the molecular basis for the property of multiple lineage potential and neural crest origin of SKPs is still elusive. Here we report the cooperative expression of pluripotency related genes (POU5F1, SOX2, NANOG, STAT3) and neural crest marker genes (p75NTR, TWIST1, PAX3, SNAI2, SOX9, SOX10) in GFP-transgenic porcine skin-derived progenitors (pSKP). The proportion of cells positive for POU5F1, nestin, fibronectin, and vimentin were 12.3%, 15.1%, 67.9% and 53.7%, showing the heterogeneity of pSKP spheres. Moreover, pSKP cells can generate both neural (neurons and glia) and mesodermal cell types (smooth muscle cells and adipocytes) in vitro, indicating the multiple lineage potency. Four transcription factors (POU5F1, SNAI2, SOX9, and PAX3) were identified that were sensitive to mitogen (FBS) and/or growth factors (EGF and bFGF). We infer that POU5F1, SNAI2, SOX9, and PAX3 may be the key players for maintaining the neural crest derived multipotency of SKP cells in vitro. This study has provided new insight into the molecular mechanism of stemness for somatic-derived stem cells at the level of transcriptional regulation.

Isolation of human bone marrow mesenchymal stem cells using different membrane markers: comparison of colony/cloning efficiency, differentiation potential, and molecular profile

Bone marrow (BM) mesenchymal stem cells (MSCs) represent an interesting field of research for their in vitro properties and the in vivo therapeutic applications. In the present study, we compared the clonogenic and differentiation capacity of MSCs present in three BM-derived populations-namely, the CD105(+)/CD45(-) cells, the glycophorin A (GlycoA)(-)/CD45(-) cells, and the BM mononuclear cells (BMMCs)-by growing/expanding clones from single colony-forming unit fibroblasts (CFU-F). We also quantified the Oct-4 and Nanog mRNA in the CD105(+)/CD45(-) and GlycoA(-)/CD45(-) cells to define the fraction containing more immature MSCs. We found that basic-fibroblast growth factor (bFGF) favors the long-term survival and growth of the more immature MSCs but has no significant effect on MSC clonogenic potential. CFU-F number and clone recovery were higher in CD105(+)/CD45(-) compared to GlycoA(-)/CD45(-) (p < 0.0001 and p = 0.0364, respectively) cells or BMMCs (p < 0.0001 and p = 0.0007, respectively). The relative mRNA expression of Oct-4 and Nanog was significantly increased in CD105(+)/CD45(-) compared to GlycoA(-)/CD45(-) cells (p < 0.0001 and p < 0.0001, respectively). No significant difference was found in the immunophenotypic characteristics and differentiation potential of clones derived from all three cellular sources. These data suggest that the CD105(+)/CD45(-) BM cell fraction is enriched in immature MSCs and, accordingly, represents an appropriate source for MSC culture initiation.

Multipotent progenitor cells are present in human peripheral blood

To determine whether the peripheral blood in humans contains a population of multipotent progenitor cells (MPCs), products of leukapheresis were obtained from healthy donor volunteers following the administration of granulocyte colony-stimulating factor. Small clusters of adherent proliferating cells were collected, and these cells continued to divide up to 40 population doublings without reaching replicative senescence and growth arrest. MPCs were positive for the transcription factors Nanog, Oct3/4, Sox2, c-Myc, and Klf4 and expressed several antigens characteristic of mesenchymal stem cells. However, they were negative for markers of hematopoietic stem/progenitor cells and bone marrow cell lineages. MPCs had a cloning efficiency of approximately 3%, and following their expansion, retained a highly immature phenotype. Under permissive culture conditions, MPCs differentiated into neurons, glial cells, hepatocytes, cardiomyocytes, endothelial cells, and osteoblasts. Moreover, the gene expression profile of MPCs partially overlapped with that of neural and embryonic stem cells, further demonstrating their primitive, uncommitted phenotype. Following subcutaneous transplantation in nonimmunosuppressed mice, MPCs migrated to distant organs and integrated structurally and functionally within the new tissue, acquiring the identity of resident parenchymal cells. In conclusion, undifferentiated cells with properties of embryonic stem cells can be isolated and expanded from human peripheral blood after granulocyte colony-stimulating factor administration. This cell pool may constitute a unique source of autologous cells with critical clinical import.

[Therapeutic application of mesenchymal stromal cells in autoimmune disease: rationale and initial clinical experience]

Mesenchymal stromal cells (MSC) are characterized by their proliferative capacity, their phenotype and their ability to multipotent differentiation. However, little is known about their function and characteristics in vivo. MSC posses a tropism for injured tissues. Numerous investigations of MSC in different model systems suggest an immunosuppressive potential, although the results are in part contradictory. Apparently, MSC exert these effects on nearly all cells in the immune system. However, the relevance and mechanisms of these phenomena in vivo are not clear. The clinical effectiveness of allogeneic MSC in the treatment of refractory graft-versus-host disease has raised hopes that MSC could offer a new concept for the therapy of other immune-mediated disorders. However, before MSC are introduced in clinical practise, several important questions as to their side effects have to be addressed. This includes the possibility that MSC may contribute to the induction of malignant diseases.

A role for NANOG in G1 to S transition in human embryonic stem cells through direct binding of CDK6 and CDC25A

In this study, we show that NANOG, a master transcription factor, regulates S-phase entry in human embryonic stem cells (hESCs) via transcriptional regulation of cell cycle regulatory components. Chromatin immunoprecipitation combined with reporter-based transfection assays show that the C-terminal region of NANOG binds to the regulatory regions of CDK6 and CDC25A genes under normal physiological conditions. Decreased CDK6 and CDC25A expression in hESCs suggest that both CDK6 and CDC25A are involved in S-phase regulation. The effects of NANOG overexpression on S-phase regulation are mitigated by the down-regulation of CDK6 or CDC25A alone. Overexpression of CDK6 or CDC25A alone can rescue the impact of NANOG down-regulation on S-phase entry, suggesting that CDK6 and CDC25A are downstream cell cycle effectors of NANOG during the G1 to S transition.

A method to generate human mesenchymal stem cell-derived neurons which express and are excited by multiple neurotransmitters

The present study describes a protocol to generate heterogenous populations of neurotransmitter-producing neurons from human mesenchymal stem cells (MSCs). MSCs are bone marrow (BM)-derived cells which undergo lineage- specific differentiation to generate bone, fat, cartilage and muscle, but are also capable of transdifferentiating into defined ectodermal and endodermal tissues. The purpose of this study is to evaluate the potential of MSCs as an alternative source of customized neurons for experimental neurobiology or other regenerative approaches. Our neuronal protocol utilizes freshly harvested human MSCs cultured on specific surfaces and exposed to an induction cocktail consisting of low serum concentration, retinoic acid (RA), growth factors and supplements. Here we report on the types of neurotransmitters produced by the neurons, and demonstrate that the cells are electrically responsive to exogenous neurotransmitter administration.

Maternal Oct-4 is a potential key regulator of the developmental competence of mouse oocytes

Background

The maternal contribution of transcripts and proteins supplied to the zygote is crucial for the progression from a gametic to an embryonic control of preimplantation development. Here we compared the transcriptional profiles of two types of mouse MII oocytes, one which is developmentally competent (MII^SN oocyte), the other that ceases development at the 2-cell stage (MII^NSN oocyte), with the aim of identifying genes and gene expression networks whose misregulated expression would contribute to a reduced developmental competence.

Results

We report that: 1) the transcription factor Oct-4 is absent in MII^NSN oocytes, accounting for 2) the down-regulation of Stella, a maternal-effect factor required for the oocyte-to-embryo transition and of which Oct-4 is a positive regulator; 3) eighteen Oct-4-regulated genes are up-regulated in MII^NSN oocytes and are part of gene expression networks implicated in the activation of adverse biochemical pathways such as oxidative phosphorylation, mitochondrial dysfunction and apoptosis.

Conclusion

The down-regulation of Oct-4 plays a crucial function in a sequence of molecular processes that leads to the developmental arrest of MII^NSN oocytes. The use of a model study in which the MII oocyte ceases development consistently at the 2-cell stage has allowed to attribute a role to the maternal Oct-4 that has never been described before. Oct-4 emerges as a key regulator of the molecular events that govern the establishment of the developmental competence of mouse oocytes.

G1 to S phase cell cycle transition in somatic and embryonic stem cells

It is well known that G1 to S phase transition is tightly regulated by the expression and phosphorylation of a number of well-characterized cyclins, cyclin-dependent kinases and members of the retinoblastoma gene family. In this review we discuss the role of these components in regulation of G1 to S phase transition in somatic cells and human embryonic stem cells. Most importantly, we discuss some new tenable links between maintenance of pluripotency and cell cycle regulation in embryonic stem cells by describing the role that master transcription factors play in this process. Finally, the differences in cell cycle regulation between murine and human embryonic stem cells are highlighted, raising interesting questions regarding their biology and stages of embryonic development from which they have been derived.

Multipotent Menstrual Blood Stromal Stem Cells: Isolation, Characterization, and Differentiation

The stromal stem cell fraction of many tissues and organs has demonstrated to exhibit stem cell properties such as the capability of self-renewal and multipotency, allowing for multilineage differentiation. In this study, we characterize a population of stromal stem cells derived from menstrual blood (MenSCs). We demonstrate that MenSCs are easily expandable to clinical relevance and express multipotent markers such as Oct-4, SSEA-4, and c-kit at the molecular and cellular level. Moreover, we demonstrate the multipotency of MenSCs by directionally differentiating MenSCs into chondrogenic, adipogenic, osteogenic, neurogenic, and cardiogenic cell lineages. These studies demonstrate the plasticity of MenSCs for potential research in regenerative medicine.