Elimination or neutralization of endogenous high-molecular-weight FGF2 mitigates doxorubicin-induced cardiotoxicity

Cardiac fibroblast growth factor 2 (FGF2) exerts multiple paracrine activities related to cardiac response to injury. Endogenous FGF2 is composed of a mixture of 70% high- and 30% low-molecular-weight isoforms (Hi-FGF2 and Lo-FGF2, respectivley); although exogenously added Lo-FGF2 is cardioprotective, the roles of endogenous Hi-FGF2 or Lo-FGF2 have not been well defined. Therefore, we investigated the effect of elimination of Hi-FGF2 expression on susceptibility to acute cardiac damage in vivo caused by an injection of the genotoxic drug doxorubicin (Dox). Mice genetically depleted of endogenous Hi-FGF2 and expressing only Lo-FGF2 [FGF2(Lo) mice] were protected from the Dox-induced decline in ejection fraction displayed by their wild-type FGF2 [FGF2(WT)] mouse counterparts, regardless of sex, as assessed by echocardiography for up to 10 days post-Dox treatment. Because cardiac FGF2 is produced mainly by nonmyocytes, we next addressed potential contribution of fibroblast-produced FGF2 on myocyte vulnerability to Dox. In cocultures of neonatal rat cardiomyocytes (r-cardiomyocytes) with mouse fibroblasts from FGF2(WT) or FGF2(Lo) mice, only the FGF2(Lo)-fibroblast cocultures protected r-cardiomyocytes from Dox-induced mitochondrial and cellular damage. When r-cardiomyocytes were cocultured with or exposed to conditioned medium from human fibroblasts, neutralizing antibodies for human Hi-FGF-2, but not total FGF2, mitigated Dox-induced injury of cardiomyocytes. We conclude that endogenous Hi-FGF2 reduces cardioprotection by endogenous Lo-FGF2. Antibody-based neutralization of endogenous Hi-FGF2 may offer a prophylactic treatment against agents causing acute cardiac damage. NEW & NOTEWORTHY Cardiomyocytes, in vivo and in vitro, were protected from the deleterious effects of the anticancer drug doxorubicin by the genetic elimination or antibody-based neutralization of endogenous paracrine high-molecular-weight fibroblast growth factor 2 isoforms. These findings have a translational potential for mitigating doxorubicin-induced cardiac damage in patients with cancer by an antibody-based treatment.

Isolation, Culture, and Functional Characterization of Human Embryonic Stem Cells: Current Trends and Challenges

Human embryonic stem cells (hESCs) hold great potential for the treatment of various degenerative diseases. Pluripotent hESCs have a great ability to undergo unlimited self-renewal in culture and to differentiate into all cell types in the body. The journey of hESC research is not that smooth, as it has faced several challenges which are limited to not only tumor formation and immunorejection but also social, ethical, and political aspects. The isolation of hESCs from the human embryo is considered highly objectionable as it requires the destruction of the human embryo. The issue was debated and discussed in both public and government platforms, which led to banning of hESC research in many countries around the world. The banning has negatively affected the progress of hESC research as many federal governments around the world stopped research funding. Afterward, some countries lifted the ban and allowed the funding in hESC research, but the damage has already been done on the progress of research. Under these unfavorable conditions, still some progress was made to isolate, culture, and characterize hESCs using different strategies. In this review, we have summarized various strategies used to successfully isolate, culture, and characterize hESCs. Finally, hESCs hold a great promise for clinical applications with proper strategies to minimize the teratoma formation and immunorejection and better cell transplantation strategies.

The Endogenous GRP78 Interactome in Human Head and Neck Cancers: A Deterministic Role of Cell Surface GRP78 in Cancer Stemness

Cell surface glucose regulated protein 78 (GRP78), an endoplasmic reticulum (ER) chaperone, was suggested to be a cancer stem cell marker, but the influence of this molecule on cancer stemness is poorly characterized. In this study, we developed a mass spectrometry platform to detect the endogenous interactome of GRP78 and investigated its role in cancer stemness. The interactome results showed that cell surface GRP78 associates with multiple molecules. The influence of cell population heterogeneity of head and neck cancer cell lines (OECM1, FaDu, and BM2) according to the cell surface expression levels of GRP78 and the GRP78 interactome protein, Progranulin, was investigated. The four sorted cell groups exhibited distinct cell cycle distributions, asymmetric/symmetric cell divisions, and different relative expression levels of stemness markers. Our results demonstrate that cell surface GRP78 promotes cancer stemness, whereas drives cells toward a non-stemlike phenotype when it chaperones Progranulin. We conclude that cell surface GRP78 is a chaperone exerting a deterministic influence on cancer stemness.

Comparative global immune-related gene profiling of somatic cells, human pluripotent stem cells and their derivatives: implication for human lymphocyte proliferation

Human pluripotent stem cells (hPSCs), including embryonic stem cells (ESCs) and induced PSCs (iPSCs), represent potentially unlimited cell sources for clinical applications. Previous studies have suggested that hPSCs may benefit from immune privilege and limited immunogenicity, as reflected by the reduced expression of major histocompatibility complex class-related molecules. Here we investigated the global immune-related gene expression profiles of human ESCs, hiPSCs and somatic cells and identified candidate immune-related genes that may alter their immunogenicity. The expression levels of global immune-related genes were determined by comparing undifferentiated and differentiated stem cells and three types of human somatic cells: dermal papilla cells, ovarian granulosa cells and foreskin fibroblast cells. We identified the differentially expressed genes CD24, GATA3, PROM1, THBS2, LY96, IFIT3, CXCR4, IL1R1, FGFR3, IDO1 and KDR, which overlapped with selected immune-related gene lists. In further analyses, mammalian target of rapamycin complex (mTOR) signaling was investigated in the differentiated stem cells following treatment with rapamycin and lentiviral transduction with specific short-hairpin RNAs. We found that the inhibition of mTOR signal pathways significantly downregulated the immunogenicity of differentiated stem cells. We also tested the immune responses induced in differentiated stem cells by mixed lymphocyte reactions. We found that CD24- and GATA3-deficient differentiated stem cells including neural lineage cells had limited abilities to activate human lymphocytes. By analyzing the transcriptome signature of immune-related genes, we observed a tendency of the hPSCs to differentiate toward an immune cell phenotype. Taken together, these data identify candidate immune-related genes that might constitute valuable targets for clinical applications.

A cancer stem cell model as the point of origin of cancer-associated fibroblasts in tumor microenvironment

Cancer-associated fibroblasts (CAFs) are one of the most prominent cell types in the stromal compartment of the tumor microenvironment. CAFs support multiple aspects of cancer progression, including tumor initiation, invasion, and metastasis. The heterogeneous nature of the stromal microenvironment is attributed to the multiple sources from which the cells in this compartment originate. The present study provides the first evidence that cancer stem cells (CSCs) are one of the key sources of CAFs in the tumor niche. We generated CSC-like cells by treating mouse induced pluripotent stem cells with conditioned medium from breast cancer cell lines. The resulting cell population expressed both CSC and pluripotency markers, and the sphere-forming CSC-like cells formed subcutaneous tumors in nude mice. Intriguingly, these CSC-like cells always formed heterogeneous populations surrounded by myofibroblast-like cells. Based on this observation, we hypothesized that CSCs could be the source of the CAFs that support tumor maintenance and survival. To address this hypothesis, we induced the differentiation of spheres and purified the myofibroblast-like cells. The resulting cells exhibited a CAF-like phenotype, suggesting that they had differentiated into the subpopulations of cells that support CSC self-renewal. These findings provide novel insights into the dynamic interplay between various microenvironmental factors and CAFs in the CSC niche.

Fibroblast-like cells as an effective feeder for the cultivation and derivation of new lines of human induced pluripotent stem cells

Induced pluripotent stem cells (iPSCs) can be a highly informative model of hereditary and sporadic human diseases. In the future, such cells can be used in substitution and regenerative therapy of a wide range of diseases and for the treatment of injuries and burns. The ability of iPSCs derived from patients with Parkinson's disease to differentiate into fibroblast-like cells (derivatives) was studied. It was found that these cells can serve as an effective feeder layer not only to maintain the pluripotency of allogenic and autologous iPSCs but also to derive new iPSC lines.

An Effective and Reliable Xeno-free Cryopreservation Protocol for Single Human Pluripotent Stem Cells

Efficient cryopreservation of human pluripotent stem cells (hPSCs) in chemically defined, xeno-free conditions is highly desirable for medical research and clinical applications such as cell-based therapies. Here we present a simple and effective slow freezing-rapid thawing protocol for the cryopreservation of feeder-free, single hPSCs. This cryopreservation protocol involves the supplementation of 10 % dimethyl sulfoxide (DMSO) and 10 μM Rho-associated kinase inhibitor Y-27632 into two types of xeno-free, defined media supplements (Knockout Serum Replacement and TeSR2). High post-thaw cell recovery (~90 %) and cell expansion (~70 %) can be achieved using this protocol. The cryopreserved single cells retain the morphological characteristics of hPSCs and differentiation capabilities of pluripotent stem cells.

Characteristic Expression of Major Histocompatibility Complex and Immune Privilege Genes in Human Pluripotent Stem Cells and Their Derivatives

Pluripotent stem cells, including human embryonic stem cells (hESCs) and induced pluripotent stem cells (hiPSCs), have been regarded as useful sources for cell-based transplantation therapy. However, immunogenicity of the cells remains the major determinant for successful clinical application. We report the examination of several hESC lines (NTU1 and H9), hiPSC lines, and their derivatives (including stem cell-derived hepatocytes) for the expression of major histocompatibility complex (MHC), natural killer (NK) cell receptor (NKp30, NKp44, NKp46) ligand, immune-related genes, human leukocyte antigen (HLA) haplotyping, and the effects in functional mixed lymphocyte reaction (MLR). Flow cytometry showed lower levels (percentages and fluorescence intensities) of MHC class I (MHC-I) molecules, β2-microglobulin, and HLA-E in undifferentiated stem cells. The levels were increased after cotreatment with interferon-γ and/or in vitro differentiation. Antigen-presenting cell markers (CD11c, CD80, and CD86) and MHC-II (HLA-DP, -DQ, and -DR) remained low throughout the treatments. Recognition of stem cells/derivatives by NK lysis receptors were lower or absent. Activation of responder lymphocytes was significantly lower by undifferentiated stem cells than by allogeneic lymphocytes in MLR, but differentiated NTU1 hESCs induced a cell number-dependent lymphocyte proliferation comparable with that by allogeneic lymphocytes. Interestingly, activation of lymphocytes by differentiated hiPSCs or H9 cells became blunted at higher cell numbers. Real-time reverse transcriptase PCR (RT-PCR) showed significant differential expression of immune privilege genes ( TGF-β2, Arginase 2, Indole 1, GATA3, POMC, VIP, CALCA, CALCB, IL-1RN, CD95L, CR1L, Serpine 1, HMOX1, IL6, LGALS3, HEBP1, THBS1, CD59, and LGALS1) in pluripotent stem cells/derivatives when compared to somatic cells. It was concluded that pluripotent stem cells/derivatives are predicted to be immunogenic, though evidence suggests some level of potential immune privilege. In addition, differential immunogenicity may exist between different pluripotent stem cell lines and their derivatives.

Human embryonic stem cell cultivation: historical perspective and evolution of xeno-free culture systems

Human embryonic stem cells (hESC) have emerged as attractive candidates for cell-based therapies that are capable of restoring lost cell and tissue function. These unique cells are able to self-renew indefinitely and have the capacity to differentiate in to all three germ layers (ectoderm, endoderm and mesoderm). Harnessing the power of these pluripotent stem cells could potentially offer new therapeutic treatment options for a variety of medical conditions. Since the initial derivation of hESC lines in 1998, tremendous headway has been made in better understanding stem cell biology and culture requirements for maintenance of pluripotency. The approval of the first clinical trials of hESC cells for treatment of spinal cord injury and macular degeneration in 2010 marked the beginning of a new era in regenerative medicine. Yet it was clearly recognized that the clinical utility of hESC transplantation was still limited by several challenges. One of the most immediate issues has been the exposure of stem cells to animal pathogens, during hESC derivation and during in vitro propagation. Initial culture protocols used co-culture with inactivated mouse fibroblast feeder (MEF) or human feeder layers with fetal bovine serum or alternatively serum replacement proteins to support stem cell proliferation. Most hESC lines currently in use have been exposed to animal products, thus carrying the risk of xeno-transmitted infections and immune reaction. This mini review provides a historic perspective on human embryonic stem cell culture and the evolution of new culture models. We highlight the challenges and advances being made towards the development of xeno-free culture systems suitable for therapeutic applications.

A reliable and economical method for gaining mouse embryonic fibroblasts capable of preparing feeder layers

Mouse embryonic fibroblasts (MEFs) are widely used to prepare feeder layers for culturing embryonic stem cells (ESCs) or induced pluripotent stem cells (iPSCs) in vitro. Transportation lesions and exorbitant prices make the commercially obtained MEFs unsuitable for long term research. The aim of present study is to establish a method, which enables researchers to gain MEFs from mice and establish feeder layers by themselves in ordinary laboratories. MEFs were isolated from ICR mouse embryos at 12.5-17.5 day post-coitum (DPC) and cultured in vitro. At P2-P7, the cells were inactivated with mitomycin C or by X-ray irradiation. Then they were used to prepare feeder layers. The key factors of the whole protocol were analyzed to determine the optimal conditions for the method. The results revealed MEFs isolated at 12.5-13.5 DPC, and cultured to P3 were the best choice for feeder preparation, those P2 and P4-P5 MEFs were also suitable for the purpose. The P3-P5 MEFs treated with 10 μg/ml of mitomycin C for 3 h, or irradiated with X-ray at 1.5 Gy/min for 25 Gy were the most suitable feeder cells. Treating MEFs with 10 μg/ml of mitomycin C for 2.5 h, 15 μg/ml for 2.0 h, or irradiating the cells with 20 Gy of X-ray at 2.0 Gy/min could all serve as alternative methods for P3-P4 cells. Our study provides a reliable and economical way to obtain large amount of qualified MEFs for long term research of ESCs or iPSCs.

Developmental Competence of Buffalo (Bubalus bubalis) Pluripotent Embryonic Stem Cells Over Different Homologous Feeder Layers and the Comparative Evaluation with Various Extracellular Matrices

BACKGROUND AND OBJECTIVES

Use of somatic cells as a feeder layer to maintain the embryonic stem cells (ESCs) in undifferentiated state limits the stem cell research design, since experimental data may result from a combined ESCs and feeder cell response to various stimuli. Therefore, present study was designed to evaluate the developmental competence of the buffalo ESCs over different homogenous feeders and compare with various extracellular matrices using different concentrations of LIF.

METHODS AND RESULTS

Inner cell masses (ICMs) of in vitro hatched blastocysts were cultured onto homologous feeders viz. fetal fibroblast, granulosa and oviductal cell feeder layers and synthetic matrices viz. fibronectin, collagen type I and matrigel in culture medium. Developmental efficiency was found higher for ESCs cultured on fetal fibroblast and granulosa layers (83.33%) followed by fibronectin (77.78%) at 30 ng LIF. Oviductal feeder was found to be the least efficient feeder showing only 11.11% undifferentiated primary ESC colonies at 30 ng LIF. However, neither feeder layer nor synthetic matrix could support the development of primary colonies at 10 ng LIF. Expression of SSEA- 4, TRA-1-60 and Oct-4 were found positive in ESC colonies from all the feeders and synthetic matrices with 20 ng and 30 ng LIF.

CONCLUSIONS

Fetal fibroblast and granulosa cell while, amongst synthetic matrices, fibronectin were found to be equally efficient to support the growth and maintenance of ESCs pluripotency with 30 ng LIF. This well-defined culture conditions may provide an animal model for culturing human embryonic stem cells in the xeno-free or feeder-free conditions for future clinical applications.

Generation of 3D skin equivalents fully reconstituted from human induced pluripotent stem cells (iPSCs)

Recent generation of patient-specific induced pluripotent stem cells (PS-iPSCs) provides significant advantages for cell- and gene-based therapy. Establishment of iPSC-based therapy for skin diseases requires efficient methodology for differentiating iPSCs into both keratinocytes and fibroblasts, the major cellular components of the skin, as well as the reconstruction of skin structures using these iPSC-derived skin components. We previously reported generation of keratinocytes from human iPSCs for use in the treatment of recessive dystrophic epidermolysis bullosa (RDEB) caused by mutations in the COL7A1 gene. Here, we developed a protocol for differentiating iPSCs into dermal fibroblasts, which also produce type VII collagen and therefore also have the potential to treat RDEB. Moreover, we generated in vitro 3D skin equivalents composed exclusively human iPSC-derived keratinocytes and fibroblasts for disease models and regenerative therapies for skin diseases, first demonstrating that iPSCs can provide the basis for modeling a human organ derived entirely from two different types of iPSC-derived cells.

Autogenic feeder free system from differentiated mesenchymal progenitor cells, maintains pluripotency of the MEL-1 human embryonic stem cells

Human embryonic stem cells (hESc) are known for its pluripotency and self renewal capability, thus possess great potential in regenerative medicine. However, the lack of suitable xenofree extracellular matrix substrate inhibits further applications or the use of hESc in cell-based therapy. In this study, we described a new differentiation method, which generates a homogeneous population of mesenchymal progenitor cells (hESc-MPC) from hESc via epithelial-mesenchymal transition. The extracellular matrix (ECM) proteins from hESc-MPC had in turn supported the undifferentiated expansion of hESc. Immunocytochemistry and flow cytometry characterization of hESc-MPC revealed the presence of early mesenchymal markers. Tandem mass spectometry analysis of ECM produced by hESc-MPC revealed the presence of a mixture of extracellular proteins which includes tenascin C, fibronectin, and vitronectin. The pluripotency of hESc (MEL-1) cultured on the ECM was maintained as shown by the expression of pluripotent genes (FoxD3, Oct-4, Tdgf1, Sox-2, Nanog, hTERT, Rex1), protein markers (SSEA-3, SSEA-4, TRA-1-81, TRA-1-60, Oct-4) and the ability to differentiate into cells representative of ectoderm, endoderm and mesoderm. In summary, we have established a xeno-free autogenic feeder free system to support undifferentiated expansion of hESc, which could be of clinical relevance.

Substrates and supplements for hESCs: a critical review

BACKGROUND

Different laboratories around the world have succeeded in establishing human embryonic stem cell (hESC) lines. However, culture conditions vary considerably among the protocols used and the vast majority of the lines at some stage of their creation have been in contact with an animal derived component. One of the main problems to be overcome for the generation of a clinical-grade hESC line is the choice of a substrate and medium that allows derivation and culture, where animal derived components are kept to a minimum or completely excluded.

MATERIALS AND METHODS

The following review describes past and more recent achievements in the creation and culturing of hESC. It describes protocols, giving special attention to the matrices and supplements used for derivation, maintainance and cryostorage, considering whether they included defined, undefined and/or animal-derived components in their formulations.

CONCLUSION

This information shall be useful for the creation and choice of new substrates and supplements for future research in the field of hESC for therapeutic purposes.

Transcriptional expression profile of cultured human embryonic stem cells in vitro and in vivo

The aims of this study were to analyze the spontaneous differentiation of human embryonic stem cells in vitro and in vivo and to investigate the influence of in vitro partial differentiation on in vivo teratoma formation in immunodeficient mice. Standardized methods are needed for long-term cultivation of undifferentiated stem cells and the multilineage cells that spontaneously differentiate from them. Accordingly, SA002 human embryonic stem cells were cultured on irradiated mouse embryonic fibroblasts cells, on irradiated human foreskin fibroblasts, or were cultured feeder-free using matrigel. Expression of marker protein transcripts was analyzed in undifferentiated and differentiated stem cells using real-time PCR, and both types of stem cells were transplanted subcutaneously into immunodeficient NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ mice to test for teratoma formation. Teratoma histology and expression profiles were subsequently characterized. Cells cultured using different conditions and morphologically undifferentiated cells had comparable marker expression profiles, showing high expression levels of markers for pluripotency and low-to-moderate expression levels of germ layer markers. Cells showing spontaneous differentiation that were cultured in feeder-free conditions in the absence of basic fibroblast growth factor demonstrated slight upregulation of sex determining region Y-box 17, connexin 32, and albumin expression at early time points, as well as expression of octamer-binding transcription factor 4, proteoglycan epitopes on podocalyxin (Trafalgar), and alkaline phosphatase. At later time points, expression of hepatocyte nuclear factor-3-beta, and hepatocyte nuclear factor-4-alpha and alpha fetoprotein was upregulated, whereas beta-3-tubulin, chemokine receptor, nestin, sex-determining region Y-box 17, and connexin 32 were downregulated. Expression of pluripotency markers remained high, and hematopoetic markers were not expressed. SA002 cells that showed spontaneous partial differentiation in vitro had a low teratoma formation capacity in vivo. Cells that were partially differentiated led to slower growing teratomas with more uniform histology.

Synergistic effect of medium, matrix, and exogenous factors on the adhesion and growth of human pluripotent stem cells under defined, xeno-free conditions

Human pluripotent stem cells (hPSCs), including human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs), share the properties of unlimited self-renewal and the capacity to become any cell type in the body, making them well suited for regenerative medicine and cell therapy. So far, almost all hPSC lines have been directly or indirectly exposed to animal-derived products, which would hinder their use for clinical purposes. One of the biggest challenges in this area is to remove animal components from the derivation, propagation, and cryopreservation of hPSCs. Moreover, the presence of undefined components of animal or human origin in culture system may interfere with the interpretation of the effect of exogenous agents on the growth and differentiation of hPSCs and are prone to significant variability. To explore hPSC expansion in defined, xeno-free conditions, 2 different groups of culture systems were used to culture different hESC and hiPSC lines. Our results suggested that (1) medium, matrix, and exogenous factors have synergistic effects on the adhesion and growth of hPSCs; (2) cooperation of exogenous factors including basic fibroblast growth factor, Rho-associated kinase inhibitor (ROCK), and other growth factors is critical for hPSC adhesion and proliferation; (3) basal media have different effects on hPSC attachment to the culture surface; and (4) a medium or matrix component can work synergistically in one culture system, and not at all in another. In this study, we found that Vitronectin/TeSR2 and PDL/HEScGRO (Y-27632) systems were optimal for maintaining the long-term culture of 3 hESC lines and 2 hiPSC lines under defined, xeno-free conditions.

Proteomic analysis of extracellular matrices used in stem cell culture

Numerous matrices for the growth of human embryonic stem cells (hESC) in vitro have been described. However, their exact composition is typically unknown. Information on the components of these matrices will aid in the development of a fully defined growth surface for hESCs. These matrices typically consist of mixture of proteins present in a wide range of abundance making their characterization challenging. In this study, we performed the proteomic analysis of five previously uncharacterized matrices: CellStart, Human Basement Membrane Extract (Human BME), StemXVivo, Bridge Human Extracellular Matrix (BridgeECM), and mouse embryonic fibroblast conditioned matrix (MEF-CMTX). Based on a proteomics protocol optimized using lysates from HeLa cells, we undertook the analysis of the five complex extracellular matrix (ECM) samples using a combination of strong anion and cation exchange chromatography and SDS-PAGE. For each of these matrices, we identify numerous proteins, indicating their complex nature. We also compared these results with a similar proteomics analysis of the growth matrix, Matrigel™. From these analyses, we observed that fibronectin is a primary component of nearly all hESC supportive matrices. This observation led to the investigation of the suitability of fibronectin as a defined ECM for the growth of hESCs. We found that fibronectin promotes the maintenance of pluripotent H9 and CA1 hESCs in an undifferentiated state using mTeSR1 medium. This finding validates the utility of characterizing matrices used for hESC growth in revealing ECM components required for culturing hESCs in a universally applicable defined system.

Epithelial cell adhesion molecule (EpCAM) complex proteins promote transcription factor-mediated pluripotency reprogramming

Epithelial cell adhesion molecule (EpCAM) is a transmembrane glycoprotein that is highly expressed in embryonic stem cells (ESCs) and its role in maintenance of pluripotency has been suggested previously. In epithelial cancer cells, activation of the EpCAM surface-to-nucleus signaling transduction pathway involves a number of membrane proteins. However, their role in somatic cell reprogramming is still unknown. Here we demonstrate that EpCAM and its associated protein, Cldn7, play a critical role in reprogramming. Quantitative RT-PCR analysis of Oct4, Sox2, Klf4, and c-Myc (OSKM) infected mouse embryonic fibroblasts (MEFs) indicated that EpCAM and Cldn7 were up-regulated during reprogramming. Analysis of numbers of alkaline phosphatase- and Nanog-positive clones, and the expression level of pluripotency-related genes demonstrated that inhibition of either EpCAM or Cldn7 expression resulted in impairment in reprogramming efficiency, whereas overexpression of EpCAM, EpCAM plus Cldn7, or EpCAM intercellular domain (EpICD) significantly enhanced reprogramming efficiency in MEFs. Furthermore, overexpression of EpCAM or EpICD significantly repressed the expression of p53 and p21 in the reprogramming MEFs, and both EpCAM and EpICD activated the promoter activity of Oct4. These observations suggest that EpCAM signaling may enhance reprogramming through up-regulation of Oct4 and possible suppression of the p53-p21 pathway. In vitro and in vivo characterization indicated that the EpCAM-reprogrammed iPSCs exhibited similar molecular and functional features to the mouse ESCs. In summary, our studies provide additional insight into the molecular mechanisms of reprogramming and suggest a more effective means of induced pluripotent stem cell generation.

Fibroblasts derived from human embryonic stem cells direct development and repair of 3D human skin equivalents

Introduction

Pluripotent, human stem cells hold tremendous promise as a source of progenitor and terminally differentiated cells for application in future regenerative therapies. However, such therapies will be dependent upon the development of novel approaches that can best assess tissue outcomes of pluripotent stem cell-derived cells and will be essential to better predict their safety and stability following in vivo transplantation.

Methods

In this study we used engineered, human skin equivalents (HSEs) as a platform to characterize fibroblasts that have been derived from human embryonic stem (hES) cell. We characterized the phenotype and the secretion profile of two distinct hES-derived cell lines with properties of mesenchymal cells (EDK and H9-MSC) and compared their biological potential upon induction of differentiation to bone and fat and following their incorporation into the stromal compartment of engineered, HSEs.

Results

While both EDK and H9-MSC cell lines exhibited similar morphology and mesenchymal cell marker expression, they demonstrated distinct functional properties when incorporated into the stromal compartment of HSEs. EDK cells displayed characteristics of dermal fibroblasts that could support epithelial tissue development and enable re-epithelialization of wounds generated using a 3D tissue model of cutaneous wound healing, which was linked to elevated production of hepatocyte growth factor (HGF). Lentiviral shRNA-mediated knockdown of HGF resulted in a dramatic decrease of HGF secretion from EDK cells that led to a marked reduction in their ability to promote keratinocyte proliferation and re-epithelialization of cutaneous wounds. In contrast, H9-MSCs demonstrated features of mesenchymal stem cells (MSC) but not those of dermal fibroblasts, as they underwent multilineage differentiation in monolayer culture, but were unable to support epithelial tissue development and repair and produced significantly lower levels of HGF.

Conclusions

Our findings demonstrate that hES-derived cells could be directed to specified and alternative mesenchymal cell fates whose function could be distinguished in engineered HSEs. Characterization of hES-derived mesenchymal cells in 3D, engineered HSEs demonstrates the utility of this tissue platform to predict the functional properties of hES-derived fibroblasts before their therapeutic transplantation.

Human fetal liver stromal cells that overexpress bFGF support growth and maintenance of human embryonic stem cells

In guiding hES cell technology toward the clinic, one key issue to be addressed is to culture and maintain hES cells much more safely and economically in large scale. In order to avoid using mouse embryonic fibroblasts (MEFs) we isolated human fetal liver stromal cells (hFLSCs) from 14 weeks human fetal liver as new human feeder cells. hFLSCs feeders could maintain hES cells for 15 passages (about 100 days). Basic fibroblast growth factor (bFGF) is known to play an important role in promoting self-renewal of human embryonic stem (hES) cells. So, we established transgenic hFLSCs that stably express bFGF by lentiviral vectors. These transgenic human feeder cells — bFGF-hFLSCs maintained the properties of H9 hES cells without supplementing with any exogenous growth factors. H9 hES cells culturing under these conditions maintained all hES cell features after prolonged culture, including the developmental potential to differentiate into representative tissues of all three embryonic germ layers, unlimited and undifferentiated proliferative ability, and maintenance of normal karyotype. Our results demonstrated that bFGF-hFLSCs feeder cells were central to establishing the signaling network among bFGF, insulin-like growth factor 2 (IGF-2), and transforming growth factor β (TGF-β), thereby providing the framework in which hES cells were instructed to self-renew or to differentiate. We also found that the conditioned medium of bFGF-hFLSCs could maintain the H9 hES cells under feeder-free conditions without supplementing with bFGF. Taken together, bFGF-hFLSCs had great potential as feeders for maintaining pluripotent hES cell lines more safely and economically.

Hypoxic culture maintains self-renewal and enhances embryoid body formation of human embryonic stem cells

Hypoxic environment is theoretically more physiological for the growth of human embryonic stem (hES) cells. It has been reported that hypoxic culture maintained better undifferentiation of hES cells, but the effects on differentiation are less well established. The hES cells were thus cultured and compared in hypoxia (2% oxygen [O2]) and normoxia (21% O2). The data showed that the undifferentiated state of hES cells was maintained more favorably in hypoxia during prolonged culture. Most tested genes belonging to FGF, TGF-beta/GMP, and Wnt signaling pathways were enriched in undifferentiated hES cells and downregulated upon differentiation, accompanied with differential expression of FGFR1, FGFR2, and FRAT2 between hypoxia and normoxia. Higher P-Smad2/3 level was identified in hypoxia, favoring the maintenance of hES cells in undifferentiation. Bisulfite sequencing showed similar imprinting status between different O2 tensions at H19 differentially methylated region (DMR) and KvDMR loci. Embryoid body formation was enhanced in hypoxia accompanied with suppressed Sox17, Desmin, Gata4, Brachyury, and Cdx2 expression. We concluded that hypoxia improved self-renewal of hES cells through modulation of major signaling pathways and was also more efficient for differentiation to embryoid bodies, though they might present with suppressed expression of some lineage-specific genes across all the three embryonic germ layers and trophectoderm.

Differentiation of embryonic stem cells into fibroblast-like cells in three-dimensional type I collagen gel cultures

Fibroblasts are heterogeneous mesenchymal cells that play important roles in the production and maintenance of extracellular matrix. Although their heterogeneity is recognized, progenitor progeny relationships among fibroblasts and the factors that control fibroblast differentiation are poorly defined. The current study was designed to develop a reliable method that would permit in vitro differentiation of fibroblast-like cells from human and murine embryonic stem cells (ESCs). Undifferentiated ESCs were differentiated into embryoid bodies (EBs) with differentiation media. EBs were then cast into type I collagen gels and cultured for 21 d with basal media. The spindle-shaped cells that subsequently grew from the EBs were released from the gels and subsequently cultured as monolayers in basal media supplemented with serum. Differentiated cells showed a characteristic spindle-shaped morphology and had ultrastructural features consistent with fibroblasts. Immunocytochemistry showed positive staining for vimentin and alpha-smooth muscle actin but was negative for stage-specific embryonic antigens and cytokeratins. Assays of fibroblast function, including proliferation, chemotaxis, and contraction of collagen gels demonstrated that the differentiated cells, derived from both human and murine ESCs, responded to transforming growth factor-β1 and prostaglandin E(2) as would be expected of fibroblasts, functions not expected of endothelial or epithelial cells. The current study demonstrates that cells with the morphologic and functional features of fibroblasts can be reliably derived from human and murine ESCs. This methodology provides a means to investigate and define the mechanisms that regulate fibroblast differentiation.

A feeder-free culture using autogeneic conditioned medium for undifferentiated growth of human embryonic stem cells: comparative expression profiles of mRNAs, microRNAs and proteins among different feeders and conditioned media

BACKGROUND

Human embryonic stem (hES) cell lines were derived from the inner cell mass of human blastocysts, and were cultured on mouse embryonic fibroblast (MEF) feeder to maintain undifferentiated growth, extensive renewal capacity, and pluripotency. The hES-T3 cell line with normal female karyotype was previously used to differentiate into autogeneic fibroblast-like cells (T3HDF) as feeder to support the undifferentiated growth of hES-T3 cells (T3/HDF) for 14 passages.

RESULTS

A feeder-free culture on Matrigel in hES medium conditioned by the autogeneic feeder cells (T3HDF) was established to maintain the undifferentiated growth of hES-T3 cells (T3/CMHDF) for 8 passages in this investigation. The gene expression profiles of mRNAs, microRNAs and proteins between the undifferentiated T3/HDF and T3/CMHDF cells were shown to be very similar, and their expression profiles were also found to be similar to those of T3/MEF and T3/CMMEF cells grown on MEF feeder and feeder-free Matrigel in MEF-conditioned medium, respectively. The undifferentiated state of T3/HDF and T3/CMHDF as well as T3/MEF and T3/CMMEF cells was evidenced by the very high expression levels of "stemness" genes and low expression levels of differentiation markers of ectoderm, mesoderm and endoderm in addition to the strong staining of OCT4 and NANOG.

CONCLUSION

The T3HDF feeder and T3HDF-conditioned medium were able to support the undifferentiated growth of hES cells, and they would be useful for drug development and toxicity testing in addition to the reduced risks of xenogeneic pathogens when used for medical applications such as cell therapies.

Factors from human embryonic stem cell-derived fibroblast-like cells promote topology-dependent hepatic differentiation in primate embryonic and induced pluripotent stem cells

The future clinical use of embryonic stem cell (ESC)-based hepatocyte replacement therapy depends on the development of an efficient procedure for differentiation of hepatocytes from ESCs. Here we report that a high density of human ESC-derived fibroblast-like cells (hESdFs) supported the efficient generation of hepatocyte-like cells with functional and mature hepatic phenotypes from primate ESCs and human induced pluripotent stem cells. Molecular and immunocytochemistry analyses revealed that hESdFs caused a rapid loss of pluripotency and induced a sequential endoderm-to-hepatocyte differentiation in the central area of ESC colonies. Knockdown experiments demonstrated that pluripotent stem cells were directed toward endodermal and hepatic lineages by FGF2 and activin A secreted from hESdFs. Furthermore, we found that the central region of ESC colonies was essential for the hepatic endoderm-specific differentiation, because its removal caused a complete disruption of endodermal differentiation. In conclusion, we describe a novel in vitro differentiation model and show that hESdF-secreted factors act in concert with regional features of ESC colonies to induce robust hepatic endoderm differentiation in primate pluripotent stem cells.

Extracellular matrix isolated from foreskin fibroblasts supports long-term xeno-free human embryonic stem cell culture

Human embryonic stem (hES) cells hold great promise for application of human cell and tissue replacement therapy. However, the overwhelming majority of currently available hES cell lines have been directly or indirectly exposed to materials containing animal-derived components during their derivation, propagation, and cryopreservation. Unlike feeder-based cultures, which require the simultaneous growth of feeder and stem cells, resulting in mixed cell populations, stem cells grown on feeder-free systems are easily separated from the surface, presenting a pure population of cells for downstream applications. In this study, we have developed a novel method to expand hES cells in xeno-free, feeder-free conditions using 2 different matrices derived from xeno-free human foreskin fibroblasts (XF-HFFs). Using XF-HFF-derived extracellular matrix, together with 100 ng/mL recombinant bFGF-supplemented HEScGRO Basal Medium, long-term xeno-free expansion of hES cells is possible. Resulting hES cells were subjected to stringent tests and were found to maintain ES cell features, including morphology, pluripotency, stable karyotype, and expression of cell surface markers, for at least 20 passages. Xeno-free culturing practices are essential for the translation of basic hES cell research into the clinic. Therefore, the method presented in this study demonstrates that hES cells can be cultured in complete xeno-free conditions without the loss of pluripotency and furthermore, without the possibility of contamination from exogenous sources.