Very small embryonic-like stem cells in cardiovascular repair

The bone marrow endothelial progenitor cell response to septic infection

Early increase in the level of endothelial progenitor cells (EPCs) in the systemic circulation occurs in patients with septic infection/sepsis. The significance and underlying mechanisms of this response remain unclear. This study investigated the bone marrow EPC response in adult mice with septic infection induced by intravenous injection (i.v.) of Escherichia coli. For in vitro experiments, sorted marrow stem/progenitor cells (SPCs) including lineage(lin)-stem cell factor receptor (c-kit)+stem cell antigen-1 (Sca-1)-, lin-c-kit+, and lin- cells were cultured with or without lipopolysaccharides (LPSs) and recombinant murine vascular endothelial growth factor (VEGF) in the absence and presence of anti-Sca-1 crosslinking antibodies. In a separate set of experiments, marrow lin-c-kit+ cells from green fluorescence protein (GFP)+ mice, i.v. challenged with heat-inactivated E. coli or saline for 24 h, were subcutaneously implanted in Matrigel plugs for 5 weeks. Marrow lin-c-kit+ cells from Sca-1 knockout (KO) mice challenged with heat-inactivated E. coli for 24 h were cultured in the Matrigel medium for 8 weeks. The marrow pool of EPCs bearing the lin-c-kit+Sca-1+VEGF receptor 2 (VEGFR2)+ (LKS VEGFR2+) and LKS CD133+VEGFR2+ surface markers expanded rapidly following septic infection, which was supported by both proliferative activation and phenotypic conversion of marrow stem/progenitor cells. Increase in marrow EPCs and their reprogramming for enhancing angiogenic activity correlated with cell-marked upregulation of Sca-1 expression. Sca-1 was coupled with Ras-related C3 botulinum toxin substrate 2 (Rac2) in signaling the marrow EPC response. Septic infection caused a substantial increase in plasma levels of IFN-γ, VEGF, G-CSF, and SDF-1. The early increase in circulating EPCs was accompanied by their active homing and incorporation into pulmonary microvasculature. These results demonstrate that the marrow EPC response is a critical component of the host defense system. Sca-1 signaling plays a pivotal role in the regulation of EPC response in mice with septic infection.

The Emerging Biological Functions of Exosomes from Dental Tissue-Derived Mesenchymal Stem Cells

Exosomes are one kind of small-cell extracellular membranous vesicles that can regulate intercellular communication and give rise to mediating the biological behaviors of cells, involving in tissue formation, repair, the modulation of inflammation, and nerve regeneration. The abundant kinds of cells can secret exosomes, among them, mesenchymal stem cells (MSCs) are very perfect cells for mass production of exosomes. Dental tissue-derived mesenchymal stem cells (DT-MSCs), including dental pulp stem cells, stem cells from exfoliated deciduous teeth, stem cells from apical papilla, stem cells from human periodontal ligament (PDLSCs), gingiva-derived mesenchymal stem cells, dental follicle stem cells, tooth germ stem cells, and alveolar bone-derived mesenchymal stem cells, are now known as a potent tool in the area of cell regeneration and therapy, more importantly, DT-MSCs can also release numerous types of exosomes, participating in the biological functions of cells. Hence, we briefly depict the characteristics of exosomes, give a detailed description of the biological functions and clinical application in some respects of exosomes from DT-MSCs through systematically reviewing the latest evidence, and provide a rationale for their use as tools for potential application in tissue engineering.

GFP Tagged VSELs Help Delineate Novel Stem Cells Biology in Multiple Adult Tissues

Various types of stem cells are being researched upon to exploit their potential for regenerative medicine including pluripotent human embryonic stem (hES) cells derived from spare human embryos, induced pluripotent stem (iPS) cells by reprogramming somatic cells to a pluripotent state and multipotent mesenchymal stem/stromal cells (MSCs) obtained in vitro from multiple tissues. More than 50 independent groups have reported another novel population of pluripotent stem cells in adult tissues termed very small embryonic-like stem cells (VSELs). VSELs are developmentally linked to primordial germ cells, which rather than giving rise to the germ cells and later ceasing to exist, survive throughout life in multiple organs along with tissue-specific adult stem cells better described as lineage-restricted, tissue-committed progenitors with limited plasticity. VSELs survive total body irradiation in bone marrow, oncotherapy in the gonads, bilateral ovariectomy in the uterus and partial pancreatectomy in the pancreas of mice and participate in the regeneration of multiple organs under normal physiological conditions. VSELs and tissue-specific progenitor cells work together in a subtle manner, maintain life-long tissue homeostasis and their dysfunction leads to various pathologies including cancer. However, due to their quiescent state, VSELs have invariably eluded lineage-tracing studies reported so far. Present article reviews novel insights into VSELs biology and how VSELs enriched from GFP (green fluorescent protein) mice have enabled to delineate their role in various biological processes in vivo. VSELs biology needs to be understood in-depth as this alone will help evolve the field of regenerative medicine and win the war against cancer.

Psychopathology and Stem Cell Mobilization in Ultra-High Risk of Psychosis and First-Episode Psychosis Patients

Although regenerative and inflammatory processes are involved in the etiopathogenesis of many psychiatric disorders, their roles are poorly understood. We investigate the potential role of stem cells (SC) and factors influencing the trafficking thereof, such as complement cascade (CC) components, phospholipid substrates, and chemokines, in the etiology of schizophrenia. We measured sphingosine-1-phosphate (S1P), stromal-derived factor 1 (SDF-1), and CC cleavage fragments (C3a, C5a, and C5b-C9; also known as the membrane attack complex) in the peripheral blood of 49 unrelated patients: 9 patients with ultra-high risk of psychosis (UHR), 22 patients with first-episode psychosis (FEP), and 18 healthy controls (HC). When compared with the HC group, the UHR and FEP groups had higher levels of C3a. We found no significant differences in hematopoietic SC, very small embryonic-like stem cell (VSEL), C5a, S1P, or SDF-1 levels in the UHR and FEP groups. However, among FEP patients, there was a significant positive correlation between VSELs (CD133+) and negative symptoms. These preliminary findings support the role of the immune system and regenerative processes in the etiology of schizophrenia. To establish the relevance of SC and other factors affecting the trafficking thereof as potential biomarkers of schizophrenia, more studies on larger groups of individuals from across the disease spectrum are needed.

Cancer Stem Cell Markers for Urinary Carcinoma

Cancer stem cell (CSC) refers to cancer cells with stem cell properties, that is, they have the ability of “self-renewal” and “differentiation.” Cancer stem cells exist in cancer cells and are the “culprit” of cancer recurrence and metastasis. It is difficult to be found because of its small amount, and it is difficult for anticancer drugs to produce effects on it. At present, the isolation and identification of cancer stem cells from many solid tumors are still quite difficult, mainly due to the lack of specific molecular markers of cancer stem cells. In this review, cancer stem cell surface markers and functional markers in urinary system were summarized. These markers can provide molecular targets for cancer therapy.

Metformin enhances the osteogenesis and angiogenesis of human umbilical cord mesenchymal stem cells for tissue regeneration engineering

Human umbilical cord mesenchymal stem cells (hUC-MSCs) are a potential clinical material in regenerative medicine applications. Metformin has shown safety and effectiveness as a clinical drug. However, the effect of metformin as a treatment on hUC-MSCs is unclear. Our research aimed to explore the effects of metformin on the osteogenesis, adipogenesis and angiogenesis of hUC-MSCs, and attempted to explain the molecular fluctuations of metformin through the mapping of protein profiles. Proliferation assay, osteogenic and adipogenic differentiation induction, cell cycle, flow cytometry, quantitative proteomics techniques and bioinformatics analysis were used to detect the influences of metformin treatment on hUC-MSCs. Our results demonstrated that low concentrations of metformin promoted the proliferation of hUC-MSCs, but high concentrations of metformin inhibited it. Metformin exhibited promotion of osteogenesis but inhibition of adipogenesis. Metformin treated hUC-MSCs up-regulated the expression of osteogenic marker ALP, OCN and RUNX2, but down-regulated the expression of adipogenic markers PPARγ and LPL. Proteomics analysis found that up-regulation of differentially expressed proteins in metformin treatment group involved the biological process of cell migration in Gene Ontology analysis. Metformin enhanced cell migration of HUVEC in a co-culture system, and hUC-MSCs treated with metformin exhibited stronger angiogenesis in vitro and in vivo compared to the hUC-MSCs group. The results of RT-qPCR revealed that the SCF and VEGFR2 were raised in metformin treatment. This study can promote the application of hUC-MSCs treated with metformin to tissue engineering for vascular reconstruction and angiogenesis.

Bimodal Imaging-Visible Nanomedicine Integrating CXCR4 and VEGFa Genes Directs Synergistic Reendothelialization of Endothelial Progenitor Cells

A major challenge to treat vascular endothelial injury is the restoration of endothelium integrity in which endothelial progenitor cells (EPCs) plays a central role. Transplantation of EPCs as a promising therapeutic means is subject to two interrelated processes, homing and differentiation of EPCs in vivo, and thus a lack of either one may greatly affect the outcome of EPC-based therapy. Herein, a polymeric nanocarrier is applied for the codelivery of CXCR4 and VEGFa genes to simultaneously promote the migration and differentiation of EPCs. Moreover, MRI T2 contrast agent SPION and NIR dye Cy7.5 are also loaded into the nanocarrier in order to track EPCs in vivo. Based on the synergistic effect of the two codelivered genes, an improved reendothelialization of EPCs is achieved in a rat carotid denuded model. The results show the potential of this bimodal imaging-visible nanomedicine to improve the performance of EPCs in repairing arterial injury, which may push forward the stem cell-based therapy of cardiovascular disease.

Identification of Human Very Small Embryonic like Stem Cells (VSELS) in Human Heart Tissue Among Young and Old Individuals

Very Small Embryonic-Like (VSEL) stem cells are a proposed pluripotent population, residing in adult tissues. VSELs have been described in multiple tissues including bone marrow, cord blood, and gonads. They exhibit multiple characteristics of embryonic stem cells including the ability to differentiate into cellular lineages of all three germ layers, including cardiomyocytes and vascular endothelial cells. However, their presence in adult solid organs such as heart in humans has not been established. VSELs are valuable source of stem cells for tissue regeneration and replacement of cells for turnover and usual wear-and-tear. The purpose of our study was to explore the existence of human VSELs (huVSELs) in human heart tissue and examine the changes in their prevalence with aging and cardiac disease. Human heart tissue, collected from healthy and ischemic heart disease subjects was examined for the prevalence of VSELS, defined as CD45-/CD133+/SSEA4+. Both epicardial and endocardial tissues were examined comparing VSEL numbers across different age groups. Our data confirm the existence of huVSELs in adult hearts with decreasing prevalence during aging. This is the first evidence of huVSELs in adult cardiac tissue. Cardiac huVSELs could be further explored in future studies to characterize their primitive potential and therapeutic potential in regenerative studies.

Gelatin Based Polymer Cell Coating Improves Bone Marrow-Derived Cell Retention in the Heart after Myocardial Infarction

BACKGROUND

Acute myocardial infarction (AMI) and the ensuing ischemic heart disease are approaching an epidemic state. Limited stem cell retention following intracoronary administration has reduced the clinical efficacy of this novel therapy. Polymer based cell coating is biocompatible and has been shown to be safe. Here, we assessed the therapeutic utility of gelatin-based biodegradable cell coatings on bone marrow derived cell retention in ischemic heart.

METHODS

Gelatin based cell coatings were formed from the surface-mediated photopolymerization of 3% gelatin methacrylamide and 1% PEG diacrylate. Cell coating was confirmed using a multimodality approach including flow cytometry, imaging flow cytometry (ImageStream System) and immunohistochemistry. Biocompatibility of cell coating, metabolic activity of coated cells, and the effect of cell coating on the susceptibility of cells for engulfment were assessed using in vitro models. Following myocardial infarction and GFP+ BM-derived mesenchymal stem cell transplantation, flow cytometric and immunohistochemical assessment of retained cells was performed.

RESULTS

Coated cells are viable and metabolically active with coating degrading within 72 h in vitro. Importantly, cell coating does not predispose bone marrow cells to aggregation or increase their susceptibility to phagocytosis. In vitro and in vivo studies demonstrated no evidence of heightened immune response or increased phagocytosis of coated cells. Cell transplantation studies following myocardial infarction proved the improved retention of coated bone marrow cells compared to uncoated cells.

CONCLUSION

Gelation based polymer cell coating is biologically safe and biodegradable. Therapies employing these strategies may represent an attractive target for improving outcomes of cardiac regenerative therapies in human studies.

VSELs Maintain their Pluripotency and Competence to Differentiate after Enhanced Ex Vivo Expansion

The very small embryonic-like stem cells (VSELs) are known as a subset of adult pluripotent stem cells able to differentiate to all three germ layers. However, their small number and quiescence restrict the possibility of their use in cell therapy. In the present study, we first delineate different subpopulation of VSELs from human cord blood CD34+ cells to define their purity. We next determine genes expression levels in the whole transcriptome of VSELs expressing the pluripotent marker NANOG and control cells under the steady state condition. We found that more than a thousand of genes are downregulated in VSELs, as well as many membrane receptors, cells signaling molecules and CDKs mRNAs. In addition, we observed discordance in some pluripotent genes expression levels with embryonic stem cells (ESCs), which could explain VSELs quiescence. We then evaluate VSELs capacity to expand and differentiate in vitro in specific and appropriate media. After 12 days culture in specific medium containing a pyrimidoindole derivative (UM171), VSELs were significantly expanded for the first time without feeder cells and importantly preserve their capacities to differentiate into hematopoietic and endothelial cells. Interestingly, this stimulation of VSELs self-renewal restores the expression of some downregulated genes known as key regulators of cell proliferation and differentiation. The properties of such pluripotent expanded cells make them a potential candidate in regenerative medicine.

Incorporating placental tissue in cord blood banking for stem cell transplantation

INTRODUCTION

Human term placenta is comprised of various tissues from which different cells can be obtained, including hematopoietic stem cells and mesenchymal stem/stromal cells (MSCs). Areas covered: This review will discuss the possibility to incorporate placental tissue cells in cord blood banking. It will discuss general features of human placenta, with a brief review of the immune cells at the fetal-maternal interface and the different cell populations isolated from placenta, with a particular focus on MSCs. It will address the question as to why placenta-derived MSCs should be banked with their hematopoietic counterparts. It will discuss clinical trials which are studying safety and efficacy of placenta tissue-derived MSCs in selected diseases, and preclinical studies which have proven their therapeutic properties in other diseases. It will discuss banking of umbilical cord blood and raise several issues for improvement, and the applications of cord blood cells in non-malignant disorders. Expert commentary: Umbilical cord blood banking saves lives worldwide. The concomitant banking of non-hematopoietic cells from placenta, which could be applied therapeutically in the future, alone or in combination to their hematopoietic counterparts, could exploit current banking processes while laying the foundation for clinical trials exploring placenta-derived cell therapies in regenerative medicine.

Improved Isolation, Proliferation, and Differentiation Capacity of Mouse Ovarian Putative Stem Cells

The recent discovery of ovarian stem cells in postnatal mammalian ovaries, also referred to as putative stem cells (PSCs), and their roles in mammalian fertility has challenged the long-existing theory that women are endowed with a certain number of germ cells. The rare amount of PSCs is the major limitation for utilizing them through different applications. Therefore, this study was conducted in six phases to find a way to increase the number of Fragilis- and mouse vasa homolog (MVH)-positive sorted cells from 14-day-old NMRI strain mice. Results showed that there is a population of Fragilis- and MVH-positive cells with pluripotent stem cell characteristics, which can be isolated and expanded for months in vitro. PSCs increase their proliferation capacity under the influence of some mitogenic agents, and our results showed that different doses of stem cell factor (SCF) induce PSC proliferation with the maximum increase observed at 50 ng/mL. SCF was also able to increase the number of Fragilis- and MVH-positive cells after sorting by magnetic-activated cell sorting and enhance colony formation efficiency in sorted cells. Differentiation capacity assay indicated that there is a basic level of spontaneous differentiation toward oocyte-like cells during 3 days of culture. However, relative gene expression was significantly higher in the follicle-stimulating hormone-treated groups, especially in the Fragilis- sorted PSCs. We suggest that higher number of PSCs provides us either a greater source of energy that can be injected into energy-impaired oocytes in women with a history of repeat IVF failure or a good source for research.

Mesenchymal stem cells in post-surgical cavities of large maxillary bone lesions

BACKGROUND

Recent studies have highlighted that MSCs are capable of regenerating large bone defects when used in combination with bone substitutes and increasing allo-graft osteointegration. We investigated the hypothesis that autologous MSCs may lead to increased bone regeneration and reduced healing time in post-surgical cavities of large maxillary bone lesions.

METHODS

This study involved 10 patients (TEST GROUP) (6 males and 4 females). All patients had expansive mandibular lesions larger than 3 cm. From the surgical point of view, the 10 patients were treated with MSCs (withdrawal of the iliac crest bone marrow BMMSs) directly into the post-surgical cavity, without the addition of filler.

RESULTS

and radiological data, in the postoperative, were compared to those of patients who did not receive any grafting of MSCs. The 7 patients with mandibular lesions showed a rapid and very good healing with an 85-90% ossification of the major defect at 12 months.

CONCLUSIONS

Through the use of stem cells a greater ossification of the residual cavity (85-90%) was observed at 12 months after surgical enucleation in contenitive defects.

Very Small Embryonic-Like Stem Cells: A Potential Developmental Link Between Germinal Lineage and Hematopoiesis in Humans

It has been suggested that hematopoietic stem/progenitor cells (HSPCs) could become specified from a population of migrating primordial germ cells (PGCs), precursors of gametes, during embryogenesis. Some recent experimental data demonstrated that the cell population that is usually considered to be PGCs, moving toward the gonadal ridges of an embryo, contains a subset of cells coexpressing several germ cell and hematopoietic markers and possessing hematopoietic activity. Experimental data showed that bone morphogenetic protein 4 (BMP4) generates PGCs from mouse bone marrow-derived pluripotent stem cells. Interestingly, functional reproductive hormone receptors have been identified in HSPCs, thus indicating their potential role in reproductive function. Several reports have demonstrated fertility restoration and germ cell generation after bone marrow transplantation in both animal models and humans. A potential link between HSPCs and germinal lineage might be represented by very small embryonic-like stem cells (VSELs), which have been found in adult human bone marrow, peripheral blood, and umbilical cord blood, express a specific pattern of pluripotency, germinal lineage, and hematopoiesis, and are proposed to persist in adult tissues and organs from the embryonic period of life. Stem cell populations, similar to VSELs, expressing several genes related to pluripotency and germinal lineage, especially to PGCs, have been discovered in adult human reproductive organs, ovaries and testicles, and were related to primitive germ cell-like cell development in vitro, thus supporting the idea of VSELs as a potential link between germinal lineage and hematopoiesis.

Identification of New Rat Bone Marrow-Derived Population of Very Small Stem Cell with Oct-4A and Nanog Expression by Flow Cytometric Platforms

Very small embryonic-like stem cells (VSELs) represent a unique rare population of adult stem cells (SCs) sharing several structural, genetic, biochemical, and functional properties with embryonic SCs and have been identified in several adult murine and human tissues. However, rat bone marrow- (BM-) derived SCs closely resembling murine or human VSELs have not been described. Thus, we employed multi-instrumental flow cytometric approach including classical and imaging cytometry and we established that newly identified population of nonhematopoietic cells expressing CD106 (VCAM-I) antigen contains SCs with very small size, expressing markers of pluripotency (Oct-4A and Nanog) on both mRNA and protein levels that indicate VSEL population. Based on our experience in both murine and human VSEL isolation procedures by fluorescence-activated cell sorting (FACS), we also optimized sorting protocol for separation of CD45⁻/Lin⁻/CD106⁺ rat BM-derived VSELs from wild type and eGFP-expressing rats, which are often used as donor animals for cell transplantations in regenerative studies in vivo. Thus, this is a first study identifying multiantigenic phenotype and providing sorting protocols for isolation VSELs from rat BM tissue for further examining of their functional properties in vitro as well as regenerative capacity in distinct in vivo rat models of tissue injury.

Mesenchymal stem cells and their subpopulation, pluripotent muse cells, in basic research and regenerative medicine

Mesenchymal stem cells (MSCs) have gained a great deal of attention for regenerative medicine because they can be obtained from easy accessible mesenchymal tissues, such as bone marrow, adipose tissue, and the umbilical cord, and have trophic and immunosuppressive effects to protect tissues. The most outstanding property of MSCs is their potential for differentiation into cells of all three germ layers. MSCs belong to the mesodermal lineage, but they are known to cross boundaries from mesodermal to ectodermal and endodermal lineages, and differentiate into a variety of cell types both in vitro and in vivo. Such behavior is exceptional for tissue stem cells. As observed with hematopoietic and neural stem cells, tissue stem cells usually generate cells that belong to the tissue in which they reside, and do not show triploblastic differentiation. However, the scientific basis for the broad multipotent differentiation of MSCs still remains an enigma. This review summarizes the properties of MSCs from representative mesenchymal tissues, including bone marrow, adipose tissue, and the umbilical cord, to demonstrate their similarities and differences. Finally, we introduce a novel type of pluripotent stem cell, multilineage-differentiating stress-enduring (Muse) cells, a small subpopulation of MSCs, which can explain the broad spectrum of differentiation ability in MSCs.

Injection of Sca-1+/CD45+/CD31+ mouse bone mesenchymal stromal-like cells improves cardiac function in a mouse myocardial infarct model

The objective of this study was to screen mouse bone marrow mesenchymal stromal cells (BMSCs) according to expression of cardiac stem cell (CSC) surface antigens and to assess the effects of resulting BMSC-like subsets on cardiac function after injection in a mouse myocardial infarct model. BMSCs were sorted by magnetic beads according to the expression of differentiation antigens on the surface of mouse CSCs, and four subsets were identified on the basis of CD45 and CD31 expression: stem cell antigen-1+ (Sca-1+)/CD45-/CD31-, Sca-1+/CD45-/CD31+, Sca-1+/CD45+/CD31-, and Sca-1+/CD45+/CD31+. When co-cultured with myocardial stem cells and 5-aza-2'-deoxycytidine for 14 days, each subset showed expression of cardiac markers α-actin, connexin 43, desmin, and cardiac troponin I; however, expression was greatest in Sca-1+/CD45+/CD31+ cells. To assess the ability of these cells to improve cardiac function, each subset was injected separately into mice with myocardial infarct induced by ligation of the left anterior descending coronary artery, and in vivo cardiac dual inversion recovery (DIR) imaging and Doppler echocardiography were performed 48 h, 96 h, and 7 days after injection. Results indicated that Sca-1+/CD45+/CD31+ cells were superior in improving cardiac function compared with the other subsets and with unsorted BMSCs. These results suggest that mouse BMSC cells are polyclonal and that the BMSC-like Sca-1+/CD45+/CD31+ subset was effective in directing cardiac differentiation and improving cardiac function in mice with myocardial infarcts.

Very small embryonic-like stem cells: implications in reproductive biology

The most primitive germ cells in adult mammalian testis are the spermatogonial stem cells (SSCs) whereas primordial follicles (PFs) are considered the fundamental functional unit in ovary. However, this central dogma has recently been modified with the identification of a novel population of very small embryonic-like stem cells (VSELs) in the adult mammalian gonads. These stem cells are more primitive to SSCs and are also implicated during postnatal ovarian neo-oogenesis and primordial follicle assembly. VSELs are pluripotent in nature and characterized by nuclear Oct-4A, cell surface SSEA-4, and other pluripotent markers like Nanog, Sox2, and TERT. VSELs are considered to be the descendants of epiblast stem cells and possibly the primordial germ cells that persist into adulthood and undergo asymmetric cell division to replenish the gonadal germ cells throughout life. Elucidation of their role during infertility, endometrial repair, superovulation, and pathogenesis of various reproductive diseases like PCOS, endometriosis, cancer, and so on needs to be addressed. Hence, a detailed review of current understanding of VSEL biology is pertinent, which will hopefully open up new avenues for research to better understand various reproductive processes and cancers. It will also be relevant for future regenerative medicine, translational research, and clinical applications in human reproduction.

Peripheral blood stem cells: phenotypic diversity and potential clinical applications

A small proportion of cells in peripheral blood are actually pluripotent stem cells. These peripheral blood stem cells (PBSCs) are thought to be heterogeneous and could be exploited for a variety of clinical applications. The exact number of distinct populations is unknown. It is likely that individual PBSC populations detected by different experimental strategies are similar or overlapping but have been assigned different names. In this mini review, we divide PBSCs into seven groups: hematopoietic stem cells (HSCs), CD34- stem cells, CD14+ stem cells, mesenchymal stem cells (MSCs), very small embryonic-like (VSEL) stem cells, endothelial progenitor cells (EPCs), and other pluripotent stem cells. We review the major characteristics of these stem/progenitor cell populations and their potential applications in ophthalmology.

Attributes of Oct4 in stem cell biology: perspectives on cancer stem cells of the ovary

Epithelial ovarian cancer (EOC) remains the most lethal of all the gynaecological malignancies with drug resistance and recurrence remaining the major therapeutic barrier in the management of the disease. Although several studies have been undertaken to understand the mechanisms responsible for chemoresistance and subsequent recurrence in EOC, the exact mechanisms associated with chemoresistance/recurrence continue to remain elusive. Recent studies have shown that the parallel characteristics commonly seen between embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSC) are also shared by a relatively rare population of cells within tumors that display stem cell-like features. These cells, termed 'cancer initiating cells' or 'cancer stem cells (CSCs)' have been shown not only to display increased self renewal and pluripotent abilities as seen in ESCs and iPSCs, but are also highly tumorigenic in in vivo mouse models. Additionally, these CSCs have been implicated in tumor recurrence and chemoresistance, and when isolated have consistently shown to express the master pluripotency and embryonic stem cell regulating gene Oct4. This article reviews the involvement of Oct4 in cancer progression and chemoresistance, with emphasis on ovarian cancer. Overall, we highlight why ovarian cancer patients, who initially respond to conventional chemotherapy subsequently relapse with recurrent chemoresistant disease that is essentially incurable.

GSK3 inhibitor-BIO regulates proliferation of female germline stem cells from the postnatal mouse ovary

OBJECTIVE

It is widely believed that in most female mammalian neonates, all germ cells enter meiosis to form the primary oocyte at the end of foetal development, and as a result, the postnatal mammalian ovary harbours only a limited supply of oocytes that cannot be regenerated. However, this idea has been challenged by the discovery of the existence of female germline stem cells (FGSCs) in postnatal mammalian ovaries.

MATERIALS AND METHODS

We have isolated ovarian GSCs from neonatal and adult mouse ovaries and expanded them in the same culture conditions as embryonic stem cells (ESCs).

RESULTS

LIF and BIO were beneficial for formation of FGSC colonies. BIO promoted proliferation of FGSCs through activation of β-catenin and up-regulation of E-cadherin. The FGSCs formed compact round colonies with unclear borders, maintained ESC characteristics and alkaline phosphatase (AP) activity, expressing germ-cell markers-Vasa, and stem-cell markers: Oct4, Klf4, C-myc, Nanog, CD49f, Sox2, CD133, SSEA1 and SSEA4. These cells had the ability to form embryoid bodies (EBs), which expressed specific markers for all three germ layers. Then we induced EBs to differentiate into neurons, cardiomyocytes, pancreatic cells and germ cells, which showed the expression of specific markers, β-III-tubulin, cardiac a-actin, Pdx1 and Zps respectively.

DISCUSSION AND CONCLUSION

This study reveals the existence of FGSCs in postnatal mouse ovary with multipotent characteristics. BIO played an important role in regulation of proliferation and maintenance of the FGSCs. This could help provide a better understanding of causes of ovarian infertility, prevention and potential treatment of infertility.

Mesenchymal cell populations: development of the induction systems for Schwann cells and neuronal cells and finding the unique stem cell population

Mesenchymal cell populations, referred to as mesenchymal stem cells or multipotent stromal cells (MSCs), which include bone marrow stromal cells (BMSCs), umbilical cord stromal cells and adipose stromal cells (ASCs), participate in tissue repair when transplanted into damaged or degenerating tissues. The trophic support and immunomodulation provided by MSCs can protect against tissue damage, and the differentiation potential of these cells may help to replace lost cells. MSCs are easily accessible and can be expanded on a large scale. In addition, BMSCs and ASCs can be harvested from the patient himself. Thus, MSCs are considered promising candidates for cell therapy. In this review, I will discuss recently discovered high-efficiency induction systems for deriving Schwann cells and neurons from MSCs. Other features of MSCs that are important for tissue repair include the self-renewing property of stem cells and their potential for differentiation. Thus, I will also discuss the stemness of MSCs and describe the discovery of a certain stem cell type among adult MSCs that can self-renew and differentiate into cells of all three germ layers. Furthermore, I will explore the prospects of using this cell population for cell therapy.

Characterization of rat very small embryonic-like stem cells and cardiac repair after cell transplantation for myocardial infarction

Stem cell therapy is a promising therapeutic strategy for treating myocardial infarction (MI). However, it is necessary to identify ideal adult stem cells for transplantation and explore mechanisms of the transplanted cells in improving cardiac functions after MI. In this study, a population of embryonic-like stem cells (ELSCs) was isolated from rat bone marrow. The cells express pluripotent stem cell transcriptional factors and present high proliferative activity on mouse embryonic fibroblast feeder. ELSCs retain clonal expansion and may form embryoid-like bodies in soft agarose containing leukemia inhibitory factor and basic fibroblast growth factor. The cells of the embryoid-like bodies can differentiate into the cells from 3 germ layers. Under induction, the cells can differentiate into cardiomyocytes and endothelial cells. In MI models of female rats, the transplantation of preinduced ELSCs of male rats reduce scar area and improve cardiac function significantly. Comparing with marrow-derived mesenchymal stem cells and ELSCs without induction, effects of the preinduced ELSCs on myocardial repair and improvement of cardiac function are greater. Survival of the transplanted cells in the peri-infarcted and infarcted regions was examined by fluorescence in situ hybridization. Y chromosome-positive cells may differentiate toward cardiomyocytes and express cTnT and Cx43. Cx43 expression was observed at conjunction of Y chromosome-positive cells and recipient cardiomyocytes. Some Y chromosome-positive cells express CD31 and incorporate into the microvessels in the infarcted tissue. These results suggest that a population of ELSCs resides in rat bone marrow and display similar biological characteristics of ESCs. ELSCs can differentiate into cardiomyocytes and endothelial cells and contribute to cardiomyogenesis and angiogenesis in vivo. Cardiac function after MI may be significantly improved with transplantation of the preinduced ELSCs. Therefore, ELSCs are novel seed cells for stem cell transplantation in regenerative medicine.

Bone marrow mesenchymal cells: how do they contribute to tissue repair and are they really stem cells?

Adult stem cells typically generate the cell types of the tissue in which they reside, and thus the range of their differentiation is considered limited. Bone marrow mesenchymal stem cells (MSCs) are different from other somatic stem cells in that they differentiate not only into the same mesodermal-lineage such as bone, cartilage, and adipocytes but also into other lineages of ectodermal and endodermal cells. Thus, MSCs are a unique type of adult stem cells. In addition, MSCs home to damaged sites, differentiate into cells specific to the tissue and contribute to tissue repair. Therefore, application of MSCs in the treatment of various diseases, including liver dysfunction, myocardial infarction, and central nervous system repair, has been initiated. Because MSCs are generally harvested as adherent cells from bone marrow aspirates, however, they comprise heterogeneous cell populations and their wide-ranging differentiation ability and repair functions are not yet clear. Recent evidence suggests that a very small subpopulation of cells that assume a repair function with the ability to differentiate into trilineage cells resides among human MSCs and effective utilization of such cells is expected to improve the repair effect of MSCs. This review summarizes recent advances in the clarification of MSC properties and discusses future perspectives.

Cardiac regeneration: different cells same goal

Cardiovascular diseases are the leading cause of mortality, morbidity, hospitalization and impaired quality of life. In most, if not all, pathologic cardiac ischemia ensues triggering a succession of events leading to massive death of cardiomyocytes, fibroblast and extracellular matrix accumulation, cardiomyocyte hypertrophy which culminates in heart failure and eventually death. Though current pharmacological treatment is able to delay the succession of events and as a consequence the development of heart failure, the only currently available and effective treatment of end-stage heart failure is heart transplantation. However, donor heart availability and immunorejection upon transplantation seriously limit the applicability. Cardiac regeneration could provide a solution, making real a dream of both scientist and clinician in the previous century and ending an ongoing challenge for this century. In this review, we present a basic overview of the various cell types that have been used in both the clinical and research setting with respect to myocardial differentiation.

Potential applications of germline cell-derived pluripotent stem cells in organ regeneration

Impressive progress has been made since the turn of the century in the field of stem cells. Different types of stem cells have now been isolated from different types of tissues. Pluripotent stem cells are the most promising cell source for organ regeneration. One such cell type is the germline cell-derived pluripotent cell, which is derived from adult spermatogonial stem cells. The germline cell-derived pluripotent stem cells have been obtained from both human and mouse and, importantly, are adult stem cells with embryonic stem cell-like properties that do not require specific manipulations for pluripotency acquisition, hence bypassing problems related to induced pluripotent stem cells and embryonic stem cells. The germline cell-derived pluripotent stem cells have been induced to differentiate into cells deriving from the three germ layers and shown to be functional in vitro. This review will discuss the plasticity of the germline cell-derived pluripotent stem cells and their potential applications in human organ regeneration, with special emphasis on liver regeneration. Potential problems related to their use are also highlighted.