Heterogeneous Population Of Stem Cells Research Articles

Stromal Vascular Fraction Derived Vasculogenesis Is Associated with the Formation of Malformed Lymphatic Vessel Structure

Tissue engineering and the development of therapies aimed at manipulating microvascular function require the ability to generate both blood and lymphatic vessels. Adipose-derived stromal vascular fraction (SVF), consisting of endothelial cells, stem cells, pericytes, smooth muscle cells, fibroblasts and immune cells, has emerged as a potential heterogeneous stem cell population for de novo vessel growth. SVF derived vasculogenesis has been reported to result in the dramatic formation of blood vessel segments that can connect with host vasculatures. Understanding how SVF can be used to therapeutically form vessels requires 1) exploration of the cell dynamics involved in the vasculogenesis process and 2) cauterization of the vessel structures. The objective of this study was to characterize SVF de novo vessel formation in an intact adult murine tissue environments. SVF was isolated from subcutaneous adipose in the inguinal region from adult C57BL/6 mice, labeled with DiI and seeded onto avascular mesentery tissues and then cultured in MEM + 10% fetal bovine serum (FBS) for up to 5 days (35 μl SVF cells/tissue; isolated from 1.8 g inguinal fats and resuspended in 200 μl MEM+FBS). Tissues were then labeled for PECAM (endothelial marker) + Lyve-1 (lymphatic marker) or NG2 (pericyte marker). By day 1, individual SVF cells started to form multi-cellular PECAM positive chord structures. Day 3 tissues displayed apparent vessel structures characterized by asterisk shaped clusters displaying a central PECAM positive “hub” and radial “spoke-like” extensions. At later time points and in regions of increased vascular coverage, the vessel structures were connected in a network pattern. In additional studies for which angiogenesis was pre-stimulated in the normally avascular mouse mesenteries, the SVF derived vessels connected to the host networks. A subset of structures during the vasculogenesis process displayed blunt ended lymphatic-like vessel structures termed “blebs.” The endothelial cell “blebs” were characterized by large, irregular diameters and a mosaic of Lyve-1 positive and negative cells. The “blebs” were also observed to connect with nearby SVF derived PECAM positive vessel segments. Our evidence of PECAM positive hub and lymphatic-like blebs provoke questions about SVF derived vessel function and suggest a previously undiscovered potential for SVF to form lymphatic vessel structures. NIH grant R21HL159501. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

FGF signaling in cranial suture development and related diseases.

Suture mesenchymal stem cells (SMSCs) are a heterogeneous stem cell population with the ability to self-renew and differentiate into multiple cell lineages. The cranial suture provides a niche for SMSCs to maintain suture patency, allowing for cranial bone repair and regeneration. In addition, the cranial suture functions as an intramembranous bone growth site during craniofacial bone development. Defects in suture development have been implicated in various congenital diseases, such as sutural agenesis and craniosynostosis. However, it remains largely unknown how intricate signaling pathways orchestrate suture and SMSC function in craniofacial bone development, homeostasis, repair and diseases. Studies in patients with syndromic craniosynostosis identified fibroblast growth factor (FGF) signaling as an important signaling pathway that regulates cranial vault development. A series of in vitro and in vivo studies have since revealed the critical roles of FGF signaling in SMSCs, cranial suture and cranial skeleton development, and the pathogenesis of related diseases. Here, we summarize the characteristics of cranial sutures and SMSCs, and the important functions of the FGF signaling pathway in SMSC and cranial suture development as well as diseases caused by suture dysfunction. We also discuss emerging current and future studies of signaling regulation in SMSCs.

Сүйек тінінің ақауы кезіндегі травматологияда қолданылатын заманауи өсу факторларының қолданылуы

An urgent problem in traumatology and orthopedics remains the closure of bone tissue defects caused by cystic formations, revision operations of open fractures, false joints of long tubular bones and chronic osteomyelitis. Platelet-rich blood plasma is extracted from the patient's own blood and used in all areas of medicine. Cellular processes after tissue damage are controlled, among other things, by platelets and dividing growth factors. Platelets produce a wide range of growth factors and cytokines after attachment, fusion, and fibrin mesh formation. Key cytokines that determine platelets play an important role in cell proliferation, chemotaxis, cell differentiation, and angiogenesis.Morphological bone proteins are a large group of structurally related proteins. BMP is closely related to the processes of bone formation and regeneration. Their mechanism of action includes the transmission of signals about chemotaxis, proliferation and differentiation of osteoporosis progenitor cells and the induction of bone formation by these cells. Extensive preclinical studies have shown that BMP is able to cause bone formation at ectopic sites and treat fractures. Mesenchymal stem cells are heterogeneous populations of stem cells that have similar characteristics and are distributed across several tissues. MSC are multipotent cells capable of repairing damaged mesenchymal tissue and bone marrow. They have the ability to differentiate into a wide range of cell types, such as chondroblasts, fibroblasts and osteoblasts, and can also produce mature cells that usually originate from the endoderm and ectoderm. Thus, mesenchymal cells are good candidates for their use in regenerative medicine and cell therapy. These stem cells can be obtained from the bone marrow in the amount of 1/1000 to 1/100 cells, which is ten times less than that of hematopoietic stem cells. Mesenchymal stem cells can also be obtained from umbilical cord blood and other tissues such as adipose tissue. The analysis of the literature shows that there remains an unsolved problem in modern medicine. With the development of modern technologies, new types of growth factors and replacement of bone defects have been invented, which, in turn, opens up new possibilities in treatment

Viral targeting of glioblastoma stem cells with patient-specific genetic and post-translational p53 deregulations.

Cancer therapy urges targeting of malignant subsets within self-renewing heterogeneous stem cell populations. We dissect the genetic and functional heterogeneity of human glioblastoma stem cells (GSCs) within patients by their innate responses to non-pathogenic mouse parvoviruses that are tightly restrained by cellular physiology. GSC neurospheres accumulate assembled capsids but restrict viral NS1 cytotoxic protein expression by an innate PKR/eIF2α-P response counteractable by electric pulses. NS1 triggers a comprehensive DNA damage response involving cell-cycle arrest, neurosphere disorganization, and bystander disruption of GSC-derived brain tumor architecture in rodent models. GSCs and cancer cell lines permissive to parvovirus genome replication require p53-Ser15 phosphorylation (Pp53S15). NS1 expression is enhanced by exogeneous Pp53S15 induction but repressed by wtp53. Consistently, patient-specific GSC subpopulations harboring p53 gain-of-function mutants and/or Pp53S15 are selective viral targets. This study provides a molecular foundation for personalized biosafe viral therapies against devastating glioblastoma and other cancers with deregulated p53 signaling.

Proteomic profiling of various human dental stem cells - a systematic review.

BACKGROUNDThe proteomic signature or profile best describes the functional component of a cell during its routine metabolic and survival activities. Additional complexity in differentiation and maturation is observed in stem/progenitor cells. The role of functional proteins at the cellular level has long been attributed to anatomical niches, and stem cells do not deflect from this attribution. Human dental stem cells (hDSCs), on the whole, are a combination of mesenchymal and epithelial coordinates observed throughout craniofacial bones to pulp.AIMTo specify the proteomic profile and compare each type of hDSC with other mesenchymal stem cells (MSCs) of various niches. Furthermore, we analyzed the characteristics of the microenvironment and preconditioning changes associated with the proteomic profile of hDSCs and their influence on committed lineage differentiation.METHODSLiterature searches were performed in PubMed, EMBASE, Scopus, and Web of Science databases, from January 1990 to December 2018. An extra inquiry of the grey literature was completed on Google Scholar, ProQuest, and OpenGrey. Relevant MeSH terms (PubMed) and keywords related to dental stem cells were used independently and in combination.RESULTSThe initial search resulted in 134 articles. Of the 134 full-texts assessed, 96 articles were excluded and 38 articles that met the eligibility criteria were reviewed. The overall assessment of hDSCs and other MSCs suggests that differences in the proteomic profile can be due to stem cellular complexity acquired from varied tissue sources during embryonic development. However, our comparison of the proteomic profile suffered inconsistencies due to the heterogeneity of various hDSCs. We believe that the existence of a heterogeneous population of stem cells at a given niche determines the modalities of regeneration or tissue repair. Added prominences to the differences present between various hDSCs have been reasoned out.CONCLUSIONSystematic review on proteomic studies of various hDSCs are promising as an eye-opener for revisiting the proteomic profile and in-depth analysis to elucidate more refined mechanisms of hDSC functionalities.

Wild-type and SAMP8 mice show age-dependent changes in distinct stem cell compartments of the interfollicular epidermis.

Delayed wound healing and reduced barrier function with an increased risk of cancer are characteristics of aged skin and one possible mechanism is misregulation or dysfunction of epidermal stem cells during aging. Recent studies have identified heterogeneous stem cell populations within the mouse interfollicular epidermis that are defined by territorial distribution and cell division frequency; however, it is unknown whether the individual stem cell populations undergo distinct aging processes. Here we provide comprehensive characterization of age-related changes in the mouse epidermis within the specific territories of slow-cycling and fast-dividing stem cells using old wild-type, senescence-accelerated mouse prone 1 (SAMP1) and SAMP8 mice. During aging, the epidermis exhibits structural changes such as irregular micro-undulations and overall thinning of the tissue. We also find that, in the old epidermis, proliferation is preferentially decreased in the region where fast-dividing stem cells reside whereas the lineage differentiation marker appears to be more affected in the slow-cycling stem cell region. Furthermore, SAMP8, but not SAMP1, exhibits precocious aging similar to that of aged wild-type mice, suggesting a potential use of this model for aging study of the epidermis and its stem cells. Taken together, our study reveals distinct aging processes governing the two epidermal stem cell populations and suggests a potential mechanism in differential responses of compartmentalized stem cells and their niches to aging.

Planarian Stem Cell Heterogeneity.

Planarian (Platyhelminthes, Triclads) are free-living flatworms endowed with extraordinary regenerative capabilities, i.e., the ability to rebuild any missing body parts also from small fragments. Planarian regenerative capabilities fascinated scientific community since early 1800, including high-standing scientists such as J.T. Morgan and C. M. Child. Today, it is known that planarian regeneration is due to the presence of a wide population of stem cells, the so-called neoblasts. However, the understanding of the nature of cells orchestrating planarian regeneration was a long journey, and several questions still remain unanswered. In this chapter, beginning from the definition of the classical concept of neoblast, we review progressive discoveries that have brought to the modern view of these cells as a highly heterogeneous population of stem cells including pluripotent stem cells and undifferentiated populations of committed progenies.

Phenotypic heterogeneity in modeling cancer evolution.

The unwelcome evolution of malignancy during cancer progression emerges through a selection process in a complex heterogeneous population structure. In the present work, we investigate evolutionary dynamics in a phenotypically heterogeneous population of stem cells (SCs) and their associated progenitors. The fate of a malignant mutation is determined not only by overall stem cell and non-stem cell growth rates but also differentiation and dedifferentiation rates. We investigate the effect of such a complex population structure on the evolution of malignant mutations. We derive exactly calculated results for the fixation probability of a mutant arising in each of the subpopulations. The exactly calculated results are in almost perfect agreement with the numerical simulations. Moreover, a condition for evolutionary advantage of a mutant cell versus the wild type population is given in the present study. We also show that microenvironment-induced plasticity in invading mutants leads to more aggressive mutants with higher fixation probability. Our model predicts that decreasing polarity between stem and non-stem cells’ turnover would raise the survivability of non-plastic mutants; while it would suppress the development of malignancy for plastic mutants. The derived results are novel and general with potential applications in nature; we discuss our model in the context of colorectal/intestinal cancer (at the epithelium). However, the model clearly needs to be validated through appropriate experimental data. This novel mathematical framework can be applied more generally to a variety of problems concerning selection in heterogeneous populations, in other contexts such as population genetics, and ecology.

Direct reprogramming of fibroblasts into skeletal muscle progenitor cells by transcription factors enriched in undifferentiated subpopulation of satellite cells

Satellite cells comprise a functionally heterogeneous population of stem cells in skeletal muscle. Separation of an undifferentiated subpopulation and elucidation of its molecular background are necessary to identify the reprogramming factors to induce skeletal muscle progenitor cells. In this study, we found that intracellular esterase activity distinguishes a subpopulation of cultured satellite cells with high stemness using esterase-sensitive cell staining reagent, calcein-AM. Gene expression analysis of this subpopulation revealed that defined combinations of transcription factors (Pax3, Mef2b, and Pitx1 or Pax7, Mef2b, and Pitx1 in embryonic fibroblasts, and Pax7, Mef2b and MyoD in adult fibroblasts) reprogrammed fibroblasts into skeletal muscle progenitor cells. These reprogrammed cells formed Dystrophin-positive mature muscle fibers when transplanted into a mouse model of Duchenne muscular dystrophy. These results highlight the new marker for heterogenous population of cultured satellite cells, potential therapeutic approaches and cell sources for degenerative muscle diseases.

Dental Pulp Stem Cells: Their Potential in Reinnervation and Angiogenesis by Using Scaffolds

Dental pulp is a highly vascularized and innervated tissue containing a heterogeneous stem cell population with multilineage differentiation potential. Current endodontic treatments focus on the preservation of the pulp tissue and the regeneration of dental pulp after pathological insults. Human dental pulp stem cells (hDPSCs) are currently investigated as stem cell–based therapy for pulp regeneration and for peripheral nerve injury in which neurons and Schwann cells display limited regenerative capacity.We have developed a neuronal differentiation protocol for hDPSCs that requires neurosphere formation before neuronal maturation. Moreover, Schwann cell differentiation of hDPSCs in our group revealed that differentiated hDPSCs have acquired the ability to myelinate and guide neurites from dorsal root ganglia.Besides their dynamic differentiation capacity, hDPSCs were shown to exert a paracrine effect on neural and endothelial cells. Analysis of hDPSC conditioned medium revealed the secretion of a broad spectrum of growth factors including brain-derived neurotrophic factor, nerve growth factor, vascular endothelial growth factor, and glial-derived neurotrophic factor. Application of the conditioned medium to endothelial cells promoted cell migration and tubulogenesis, indicating a paracrine proangiogenic effect. This hypothesis was enforced by the enhanced formation of blood vessels in the chorioallantoic membrane assay in the presence of hDPSCs. In addition, transplantation of 3-dimensional–printed hydroxyapatite scaffolds containing peptide hydrogels and hDPSCs into immunocompromised mice revealed blood vessel ingrowth, pulplike tissue formation, and osteodentin deposition suggesting osteogenic/odontogenic differentiation of hDPSCs.Future studies in our research group will focus on the pulp regeneration capacity of hDPSCs and the role of fibroblasts within the pulp extracellular matrix.

Cardiosphere-Derived Cells Require Endoglin for Paracrine-Mediated Angiogenesis.

SummaryClinical trials of stem cell therapy to treat ischemic heart disease primarily use heterogeneous stem cell populations. Small benefits occur via paracrine mechanisms that include stimulating angiogenesis, and increased understanding of these mechanisms would help to improve patient outcomes. Cardiosphere-derived-cells (CDCs) are an example of these heterogeneous stem cell populations, cultured from cardiac tissue. CDCs express endoglin, a co-receptor that binds specific transforming growth factor β (TGFβ) family ligands, including bone morphogenetic protein 9 (BMP9). In endothelial cells endoglin regulates angiogenic responses, and we therefore hypothesized that endoglin is required to promote the paracrine pro-angiogenic properties of CDCs. Cre/LoxP technology was used to genetically manipulate endoglin expression in CDCs, and we found that the pro-angiogenic properties of the CDC secretome are endoglin dependent both in vitro and in vivo. Importantly, BMP9 pre-treatment of endoglin-depleted CDCs restores their pro-angiogenic paracrine properties. As BMP9 signaling is normally required to maintain endoglin expression, we propose that media containing BMP9 could be critical for therapeutic CDC preparation.

Single-cell gene expression analysis reveals diversity among human spermatogonia.

Is the molecular profile of human spermatogonia homogeneous or heterogeneous when analysed at the single-cell level? Heterogeneous expression profiles may be a key characteristic of human spermatogonia, supporting the existence of a heterogeneous stem cell population. Despite the fact that many studies have sought to identify specific markers for human spermatogonia, the molecular fingerprint of these cells remains hitherto unknown. Testicular tissues from patients with spermatogonial arrest (arrest, n = 1) and with qualitatively normal spermatogenesis (normal, n = 7) were selected from a pool of 179 consecutively obtained biopsies. Gene expression analyses of cell populations and single-cells (n = 105) were performed. Two OCT4-positive individual cells were selected for global transcriptional capture using shallow RNA-seq. Finally, expression of four candidate markers was assessed by immunohistochemistry. Histological analysis and blood hormone measurements for LH, FSH and testosterone were performed prior to testicular sample selection. Following enzymatic digestion of testicular tissues, differential plating and subsequent micromanipulation of individual cells was employed to enrich and isolate human spermatogonia, respectively. Endpoint analyses were qPCR analysis of cell populations and individual cells, shallow RNA-seq and immunohistochemical analyses. Unexpectedly, single-cell expression data from the arrest patient (20 cells) showed heterogeneous expression profiles. Also, from patients with normal spermatogenesis, heterogeneous expression patterns of undifferentiated (OCT4, UTF1 and MAGE A4) and differentiated marker genes (BOLL and PRM2) were obtained within each spermatogonia cluster (13 clusters with 85 cells). Shallow RNA-seq analysis of individual human spermatogonia was validated, and a spermatogonia-specific heterogeneous protein expression of selected candidate markers (DDX5, TSPY1, EEF1A1 and NGN3) was demonstrated. The heterogeneity of human spermatogonia at the RNA and protein levels is a snapshot. To further assess the functional meaning of this heterogeneity and the dynamics of stem cell populations, approaches need to be developed to facilitate the repeated analysis of individual cells. Our data suggest that heterogeneous expression profiles may be a key characteristic of human spermatogonia, supporting the model of a heterogeneous stem cell population. Future studies will assess the dynamics of spermatogonial populations in fertile and infertile patients. RNA-seq data is published in the GEO database: GSE91063. This work was supported by the Max Planck Society and the Deutsche Forschungsgemeinschaft DFG-Research Unit FOR 1041 Germ Cell Potential (grant numbers SCHO 340/7-1, SCHL394/11-2). The authors declare that there is no conflict of interest.

Single cell transplantation—Golden standard of hematopoietic stem cell heterogeneity study

Hematopoietic stem cells (HSC) are one of the earliest, and most extensively studied stem cells that have been used in clinical medicine and serve as an excellent model in stem cell study. HSC are a heterogeneous population consisting of functionally different subsets. HSC transplantation is a golden standard for detection of self-renewal and multi-potential differentiation ability. Nowadays, population-based research cannot meet the need for deep understanding of biological functions and it is necessary to study at the single cell level. In this article, we introduce experimental procedures and data analysis of single cell transplantation. Researchers in related fields may find these technologies useful in their studies. As such, single cell biology is expected to increasingly expand for understanding of fundamental basis in medical science, understand applicability of single cell transplantation, acquire specific experimental operation, and promote wide applications, thus acting as a paradigm and reference for the study of other heterogeneous stem cell population.

Testicular Stem Cells Express Follicle-Stimulating Hormone Receptors and Are Directly Modulated by FSH.

Testicular spermatogonial stem cells (SSCs) are a heterogeneous population of stem cells, and definitive marker for the most primitive subset that undergoes asymmetric cell division remains to be identified. A novel subpopulation of pluripotent, very small embryonic-like stem cells (VSELs) has been reported in both human and mouse testes. Follicle-stimulating hormone (FSH) receptors (FSHRs) are expressed on Sertoli cells in testis and on granulosa cells in ovary, but recently FSHRs are reported on VSELs in ovaries, bone marrow, and cord blood. The present study was aimed to investigate whether FSHRs are also expressed on testicular stem cells (VSELs and SSCs) and their possible modulation by FSH using intact and chemoablated (25 mg/kg busulfan) mice. Chemoablated testis was a better model to study stem cell biology since quiescent stem cells survive along with the Sertoli cells in the tubules. Proliferating cell nuclear antigen-positive, small-sized cells presumed to be VSELs were clearly visualized, and flow cytometry analysis revealed an increase in LIN-/CD45-/SCA-1+ VSELs from 0.045±0.008% to 0.1±0.03% of total cells in chemoablated testis after FSH treatment. Very small embryonic-like stem cells expressing nuclear octamer-binding transcription factor 4 (OCT-4) and SSCs with cytoplasmic OCT-4 were detected. Very small embryonic-like stem cells (Oct-4A, Sca-1, Nanog), SSCs (Oct-4), and proliferation (Pcna) specific transcripts were upregulated on FSH treatment. Stem cells expressed FSHR and were stimulated by FSH, and Fshr3 was the predominant transcript maximally modulated by FSH. Nuclear OCT-4 and SCA-1 (stem cell antigen 1) positive VSELs are the most primitive stem cells in testis, and FSH stimulates them to undergo asymmetric cell division including self-renewal and give rise to SSCs, which in turn proliferate rapidly and undergo clonal expansion and further differentiation.

Skin-derived stem cells as a source of primordial germ cell- and oocyte-like cells.

The skin is a unique organ that contains a variety of stem cells for the maintenance of skin homeostasis and the repair of skin tissues following injury and disease. Skin-derived stem cells (SDSCs) constitute a heterogeneous population of stem cells generated in vitro from dermis, which can be cultured as spherical aggregates of cells in suspension culture. Under certain in vitro or in vivo conditions, SDSCs show multipotency and can generate a variety of neural, mesodermal, and endodermal cell types such as neurons, glia, fibroblasts, adipocytes, muscle cells, chondroblasts, osteoblats, and islet β-cell-like cells. SDSCs are likely derived from multipotent stem cells located in the hair follicles that are, in turn, derived from embryonic migratory neural crest or mesoderm cells. During the past decade, a wave of reports have shown that germ cells can be generated from various types of stem cells. It has been shown that SDSCs are able to produce primordial germ cell-like cells in vitro, and even oocyte-like cells (OLCs). Whether these germ cell-like cells (GCLCs) can give rise to viable progeny remains, however, unknown. In this review, we will discuss the origin and characteristics of SDSCs from which the GCLC are derived, the possible mechanisms of this differentiation process, and finally the prospective biomedical applications of the SDSC-derived GCLCs.

Human dental follicle cells express embryonic, mesenchymal and neural stem cells markers

ObjectiveThis study was conducted to identify and characterize dental follicle stem cells (DFSCs) by analyzing expression of embryonic, mesenchymal and neural stem cells surface markers. Design Dental follicle cells (DFCs) were evaluated by immunocytochemistry using embryonic stem cells markers (OCT4 and SOX2), mesenchmal stem cells (MSCs) markers (Notch1, active Notch1, STRO, CD44, HLA-ABC, CD90), neural stem cells markers (Nestin and β-III-tubulin), neural crest stem cells (NCSCs) markers (p75 and HNK1) and a glial cells marker (GFAP). RT-PCR was performed to identify the expression of OCT4 and NANOG in DFCs and dental follicle tissue. ResultsImmunocytochemistry and RT-PCR analysis revealed that a significant proportion of the DFCs evaluated expressed human embryonic stem cells marker OCT4 (75%) whereas NANOG was weakly expressed. A considerable amount of MSCs (90%) expressed Notch1, STRO, CD44 and HLA-ABC. However, they were weakly positive for CD90. Moreover, it was possible to demonstrate that dental follicle contains a significant proportion of neural stem/progenitors cells, expressing β-III-tubulin (90%) and nestin (70%). Interestingly, immunocytochemistry showed DFCs positive for p75 (50%), HNK1 (<10%) and a small proportion (<20%) of GFAP-positive cells. This is the first study reporting the presence of NCSCs and glial-like cells in the dental follicle. ConclusionsThe results of the present study suggest the occurrence of heterogeneous populations of stem cells, particularly neural stem/progenitor cells, in the dental follicle, Therefore, the human dental follicle might be a promising source of adult stem cells for regenerative purposes.

Controlling Stochasticity in Epithelial-Mesenchymal Transition Through Multiple Intermediate Cellular States.

Epithelial-mesenchymal transition (EMT) is an instance of cellular plasticity that plays critical roles in development, regeneration and cancer progression. Recent studies indicate that the transition between epithelial and mesenchymal states is a multi-step and reversible process in which several intermediate phenotypes might coexist. These intermediate states correspond to various forms of stem-like cells in the EMT system, but the function of the multi-step transition or the multiple stem cell phenotypes is unclear. Here, we use mathematical models to show that multiple intermediate phenotypes in the EMT system help to attenuate the overall fluctuations of the cell population in terms of phenotypic compositions, thereby stabilizing a heterogeneous cell population in the EMT spectrum. We found that the ability of the system to attenuate noise on the intermediate states depends on the number of intermediate states, indicating the stem-cell population is more stable when it has more sub-states. Our study reveals a novel advantage of multiple intermediate EMT phenotypes in terms of systems design, and it sheds light on the general design principle of heterogeneous stem cell population.

Characterization of p75 neurotrophin receptor expression in human dental pulp stem cells

Human adult dental pulp stem cells (DPSC) are a heterogeneous stem cell population, which are able to differentiate down neural, chondrocyte, osteocyte and adipocyte lineages. We studied the expression pattern of p75 neurotrophin receptors (p75NTR), a marker of neural stem cells, within human DPSC populations from eight donors. p75NTR are expressed at low levels (<10%) in DPSC. Importantly, p75+ DPSC represent higher expression levels of SOX1 (neural precursor cell marker), SOX2 (cell pluripotency marker) and nestin (neural stem cell marker) in comparison to p75− DPSC. Our results suggest that p75+ hDPSC may denote a subpopulation with greater neurogenic potential.

Dynamic heterogeneity as a strategy of stem cell self-renewal

To maintain cycling adult tissue in homeostasis the balance between proliferation and differentiation of stem cells needs to be precisely regulated. To investigate how stem cells achieve perfect self-renewal, emphasis has been placed on models in which stem cells progress sequentially through a one-way proliferative hierarchy. However, investigations of tissue regeneration have revealed a surprising degree of flexibility, with cells normally committed to differentiation able to recover stem cell competence following injury. Here, we investigate whether the reversible transfer of cells between states poised for proliferation or differentiation may provide a viable mechanism for a heterogeneous stem cell population to maintain homeostasis even under normal physiological conditions. By addressing the clonal dynamics, we show that such models of "dynamic heterogeneity" may be equally capable of describing the results of recent lineage tracing assays involving epithelial tissues. Moreover, together with competition for limited niche access, such models may provide a mechanism to render tissue homeostasis robust. In particular, in 2D epithelial layers, we show that the mechanism of dynamic heterogeneity avoids some pathological dependencies that undermine models based on a hierarchical stem/progenitor organization.

Migration of Bone Marrow-Derived Very Small Embryonic-Like Stem Cells toward An Injured Spinal Cord.

Bone marrow (BM) is one of the major hematopoietic organs in postnatal life that consists of a heterogeneous population of stem cells which have been previously described. Recently, a rare population of stem cells that are called very small embryonic-like (VSEL) stem cells has been found in the BM. These cells express several developmental markers of pluri- potent stem cells and can be mobilized into peripheral blood (PB) in response to tissue injury. In this study we have attempted to investigate the ability of these cells to migrate toward an injured spinal cord after transplantation through the tail vein in a rat model. In this experimental study, VSELs were isolated from total BM cells using a fluorescent activated cell sorting (FACS) system and sca1 and stage specific embryonic antigen (SSEA-1) antibodies. After isolation, VSELs were cultured for 7 days on C2C12 as the feeder layer. Then, VSELs were labeled with 1,1´-dioctadecyl-3,3,3´,3´- tetramethylindocarbocyanine perchlorate (DiI) and transplanted into the rat spinal cord injury (SCI) model via the tail vein. Finally, we sought to determine the presence of VSELs in the lesion site. We isolated a high number of VSELs from the BM. After cultivation, the VSELs colonies were positive for SSEA-1, Oct4 and Sca1. At one month after transplantation, real-time polymerase chain reaction analysis confirmed a significantly increased expres- sion level of Oct4 and SSEA-1 positive cells at the injury site. VSELs have the capability to migrate and localize in an injured spinal cord after transplantation.