A Novel Method for Generating Xeno-Free Human Feeder Cells for Human Embryonic Stem Cell Culture

The pluripotency state of human embryonic stem cells derived from single blastomeres of eight-cell embryos

Human embryonic stem cells (hESCs) derived from blastocyst stage embryos present a primed state of pluripotency, whereas mouse ESCs (mESCs) display naïve pluripotency. Their unique characteristics make naïve hESCs more suitable for particular applications in biomedical research. This work aimed to derive hESCs from single blastomeres and determine their pluripotency state, which is currently unclear. We derived hESC lines from single blastomeres of 8-cell embryos and from whole blastocysts, and analysed several naïve pluripotency indicators, their transcriptomic profile and their trilineage differentiation potential. No significant differences were observed between blastomere-derived hESCs (bm-hESCs) and blastocyst-derived hESCs (bc-hESCs) for most naïve pluripotency indicators, including TFE3 localization, mitochondrial activity, and global DNA methylation and hydroxymethylation, nor for their trilineage differentiation potential. Nevertheless, bm-hESCs showed an increased single-cell clonogenicity and a higher expression of naïve pluripotency markers at early passages than bc-hESCs. Furthermore, RNA-seq revealed that bc-hESCs overexpressed a set of genes related to the post-implantational epiblast. Altogether, these results suggest that bm-hESCs, although displaying primed pluripotency, would be slightly closer to the naïve end of the pluripotency continuum than bc-hESCs.

Comparison of Proangiogenic Effects of Adipose-Derived Stem Cells and Foreskin Fibroblast Exosomes on Artificial Dermis Prefabricated Flaps

Large prefabricated flaps often suffer from necrosis or poor healing due to a lack of new blood vessels and related factors that promote angiogenesis. The innovative use of adipose-derived stem cell exosomes (ADSC-Exo) resolves the problem of vascularization of prefabricated flaps. We analyzed the differential microRNA (miRNA) expression in ADSC-Exo using next-generation sequencing (NGS) technology to explore their potential mechanisms in promoting vascularization. We observed that ADSC-Exo could significantly promote the vascularization of artificial dermis prefabricated flaps compared with human foreskin fibroblast exosomes. NGS indicated that there were some differentially expressed miRNAs in both exosomes. Bioinformatics analysis suggested that significantly upregulated hsa-miR-760 and significantly downregulated hsa-miR-423-3p in ADSC-Exo could regulate the expression of the ITGA5 and HDAC5 genes, respectively, to promote the vascularization of skin flaps. In summary, ADSC-Exo can promote skin-flap vascularization, and thereby resolve the problem of insufficient neovascularization of artificial dermis prefabricated flaps, thus expanding the application of prefabricated skin-flap transplantation.

Establishment of a feeder and serum-free culture system for human embryonic stem cells

Stem cells are an immortal cell population capable of self-renewal; they are essential for human development and ageing and are a major focus of research in regenerative medicine. Despite considerable progress in differentiation of stem cells in vitro, culture conditions require further optimization to maximize the potential for multicellular differentiation during expansion. The aim of this study was to develop a feeder-free, serum-free culture method for human embryonic stem cells (hESCs), to establish optimal conditions for hESC proliferation, and to determine the biological characteristics of the resulting hESCs. The H9 hESC line was cultured using a homemade serum-free, feeder-free culture system, and growth was observed. The expression of pluripotency proteins (OCT4, NANOG, SOX2, LIN28, SSEA-3, SSEA-4, TRA-1-60, and TRA-1-81) in hESCs was determined by immunofluorescence and western blotting. The mRNA expression levels of genes encoding nestin, brachyury and α-fetoprotein in differentiated H9 cells were determined by RT-PCR. The newly developed culture system resulted in classical hESC colonies that were round or elliptical in shape, with clear and neat boundaries. The expression of pluripotency proteins was increased, and the genes encoding nestin, brachyury, and α-fetoprotein were expressed in H9 cells, suggesting that the cells maintained in vitro differentiation capacity. Our culture system containing a unique set of components, with animal-derived substances, maintained the self-renewal potential and pluripotency of H9 cells for eight passages. Further optimization of this system may expand the clinical application of hESCs.

Xeno-free expansion of adult keratinocytes for clinical application: the use of human-derived feeder cells and serum

Cultured epithelial autograft (CEA) was the birth of skin tissue engineering and encompassed methodologies for the isolation and expansion of autologous basal keratinocytes for burn treatment that are still practiced at some specialised units around the world. One of the limitations of CEA, however, is the reliance on animal-derived material during the manufacturing process and despite all efforts to date, no xeno-free alternative with proven efficacy has been reported. Here, we investigate whether human-derived fibroblast feeder cells and human serum can sufficiently and effectively provide a suitable microenvironment for adult keratinocyte isolation and expansion. Human dermal fibroblasts and epidermal keratinocytes were isolated from discarded skin during abdominoplasty and breast reduction procedures and cultured in xeno-free conditions. We report that these xeno-free adult keratinocytes form similar numbers of colony-forming units as those cultured using the Green's methods; however, xeno-free keratinocytes express lower levels of α6 integrin (CD49f; a progenitor and stem cell marker). We identified IL-8 as a potential growth factor secreted by adult human fibroblasts that may enhance keratinocyte colony formation in human serum. Finally, we propose a step-by-step xeno-free isolation and cultivation methodology for adult keratinocytes that can be tested further in serial cultivation for clinical application.

An Integrated Approach toward the Biomanufacturing of Engineered Cell Therapy Products in a Stirred-Suspension Bioreactor

Recent advances in stem cell biology have accelerated the pre-clinical development of cell-based therapies for degenerative and chronic diseases. The success of this growing area hinges upon the concomitant development of scalable manufacturing platforms that can produce clinically relevant quantities of cells for thousands of patients. Current biomanufacturing practices for cell therapy products are built on a model previously optimized for biologics, wherein stable cell lines are established first, followed by large-scale production in the bioreactor. This “two-step” approach can be costly, labor-intensive, and time-consuming, particularly for cell therapy products that must be individually sourced from patients or compatible donors. In this report, we describe a “one-step” integrated approach toward the biomanufacturing of engineered cell therapy products by direct transfection of primary human fibroblast in a continuous stirred-suspension bioreactor. We optimized the transfection efficiency by testing rate-limiting factors, including cell seeding density, agitation rate, oxygen saturation, microcarrier type, and serum concentration. By combining the genetic modification step with the large-scale expansion step, this not only removes the need for manual handing of cells in planar culture dishes, but also enables the biomanufacturing process to be streamlined and automated in one fully enclosed bioreactor.

Human foreskin fibroblasts: from waste bag to important biomedical applications

Circumcision is one of the most performed surgical procedures worldwide, and it is estimated that one in three men worldwide is circumcised, which makes the preputial skin removed after surgery an abundant material for possible applications. In particular, it is possible efficiently to isolate the cells of the foreskin, with fibroblasts being the most abundant cells of the dermis and the most used in biomedical research. This work aimed to review the knowledge and obtain a broad view of the main applications of human foreskin fibroblast cell culture. A literature search was conducted, including clinical trials, preclinical basic research studies, reviews and experimental studies. Several medical and laboratory applications of human foreskin fibroblast cell culture have been described, especially when it comes to the use of human foreskin fibroblasts as feeder cells for the cultivation of human embryonic stem cells, in addition to co-culture with other cell types. The culture of foreskin fibroblasts has also been used to: obtain induced pluripotent stem cells; the diagnosis of Clostridium difficile; to test the toxicity and effect of substances on normal cells, especially the toxicity of possible antineoplastic drugs; in viral culture, mainly of the human cytomegalovirus, study of the pathogenesis of other microorganisms; varied studies of cellular physiology and cellular interactions. Fibroblasts are important for cell models for varied application cultures, demonstrating how the preputial material can be reused, making possible new applications.

Level of evidence: Not applicable for this multicentre audit.

Clean-Up Human Embryonic Stem Cell Lines Using Humanized Culture Condition

Human embryonic stem cell (hESC) culture system has been changing culture conditions from conventional to xeno-free for therapeutic cell applications, and N-glycolylneuraminic acid (Neu5Gc) could be a useful indicator of xenogeneic contaminations in hESCs because human cells can no longer produce it genetically. We set up the humanized culture condition using commercially available humanized materials and two different adaptation methods: sequential or direct. SNUhES4 and H1 hESC lines, previously established in conventional culture conditions, were maintained using the humanized culture condition and were examined for the presence of Neu5Gc. The hESCs showed the same morphology and character as those of the conventional culture condition. Moreover, they were negative for Neu5Gc within two passages without loss of pluripotency. This study suggested that this method can effectively cleanse previously established hESC lines, bringing them one step closer to being clinical-grade hESCs.

Original article. Human dental pulp stem cells as a potential feeder layer for human embryonic stem cell culture

Background: Human embryonic stem (hES) cells are pluripotent, and can differentiate into three germ layers. Traditionally, cultures of hES cells are maintained in a system containing mouse embryonic fibroblasts as a feeder layer for support of undifferentiated growth. However, contamination by animal cells limits the use of hES cells.

Objective: We evaluated the use of human dental pulp stem cells (hDPSCs) as a feeder layer for hES cell culture. It should be possible to obtain a new source of human mesenchymal stem cells for feeder cells to maintain undifferentiated growth of hES cells.

Methods: hDPSCs from removed impacted wisdom teeth (third molars) were extracted, cultured, and characterized for mesenchymal stem cell properties. Furthermore, hDPSCs were used as a feeder layer for culturing Chula2 and Chula5 hES cell lines. Finally, hES cell lines grown on hDPSCs feeders were examined embryonic stem cell properties.

Results: We found that hDPSCs, which have mesenchymal properties, can support undifferentiated growth of hES cell lines. After prolonged culture (passage 17), these hES cell lines still maintain ES cell properties including typical morphology seen in hES cells, the expression of pluripotency markers (Oct4, Sox2, Nanog, Rex1, SSEA-3, SSEA-4, TRA-1-60, and TRA-1-81), embryoid body formation and retention of a normal karyotype.

Conclusion: hDPSCs, derived from the pulp tissue of impacted third molars, are a potential source of human feeder cells for the culture of undifferentiated hES cells.

Comparison of a xeno-free and serum-free culture system for human embryonic stem cells with conventional culture systems

BACKGROUND

Elimination of all animal components during derivation and long-term culture of human embryonic stem cells (hESCs) is necessary for future applications of hESCs in clinical cell therapy.

METHODS

In this study, we established the culture system of xeno-free human foreskin fibroblast feeders (XF-HFF) in combination with chemically defined medium (CDM). XF-HFF/CDM was compared with several conventional culture systems. The hESCs cultured in different media were further characterized through karyotype analysis, pluripotency gene expression, and cell differentiation ability.

RESULTS

The hESCs in the XF-HFF/CDM maintained their characteristics including typical morphology and stable karyotype. In addition, hESCs were characterized by fluorescent immunostaining of pluripotent markers and teratoma formation in vivo. RT-PCR analysis shown that the stem cell markers OCT3/4, hTERT, SOX2, and Nanog were present in the cell line hESC-1 grown on XF-HFF/CDM. Furthermore, the results of cell growth and expression of bFGF, Oct-4, and hTERT indicated that XF-HFF/CDM had better performance than human serum-matrix/CDM and XF-HFF/human serum.

CONCLUSION

The comparison of different xeno-free culture conditions will facilitate clarifying the key features of self-renewal, pluripotency, and derivation and will shed light on clinic applications of hESCs.

Generation of iPSC line iPSC-FH2.1 in hypoxic conditions from human foreskin fibroblasts

Human foreskin fibroblasts were used to generate the iPSC line iPSC-FH2.1 using the EF1a-hSTEMCCA-loxP vector expressing OCT4, SOX2, c-MYC and KLF4, in 5% O2 culture conditions. Stemness was confirmed, as was pluripotency both in vivo and in vitro, in normoxia and hypoxia. Human Embryonic Stem Cell (hESC) line WA-09 and reprogrammed fibroblast primary culture HFF-FM were used as controls.

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.

Expansion of Human Induced Pluripotent Stem Cells in Stirred Suspension Bioreactors

Human induced pluripotent stem cells (hiPSCs) hold great promise as a cell source for therapeutic applications and regenerative medicine. Traditionally, hiPSCs are expanded in two-dimensional static culture as colonies in the presence or absence of feeder cells. However, this expansion procedure is associated with lack of reproducibility and low cell yields. To fulfill the large cell number demand for clinical use, robust large-scale production of these cells under defined conditions is needed. Herein, we describe a scalable, low-cost protocol for expanding hiPSCs as aggregates in a lab-scale bioreactor.

Human Menstrual Blood-Derived Mesenchymal Cells as New Human Feeder Layer System for Human Embryonic Stem Cells

Human embryonic stem cells (hESCs) in general require coculture with feeder layers in order to remain undifferentiated. However, the use of animal-derived feeder layers is incompatible with the clinical setting. The objective of this work was to investigate whether human menstrual blood-derived mesenchymal cells (MBMCs) can substitute mouse embryonic fibroblasts (MEFs) as a feeder layer for H9-hESCs. Both feeder cell types were isolated and cultured in DMEM F-12 and high glucose DMEM, respectively. After three passages, they were inactivated with mitomycin C. To test MBMC feeder layer capacity, hESCs were grown over MBMCs and MEFs under standard conditions. hESC growth, proliferation, survival, and maintenance of the undifferentiated state were evaluated. hESCs grown over MBMCs preserved their undifferentiated state presenting standard morphology, expressing alkaline phosphatase, transcription factors OCT3/4, SOX2, and NANOG by RT-PCR and SSEA-4 and OCT3/4 by immunofluorescence assays. It is noteworthy that none of the feeder cells expressed these proteins. The average colony size of the hESCs on MBMCs was higher when compared to MEFs (p < 0.05; mean ± SD, n = 3). Growth factor analysis revealed amplification of the transcripts for FGF-2, BMP4, TGF-β, VEGF, and PEDF by RT-PCR in MBMCs and MEFs before and after inactivation. Furthermore, similar embryoid body formation, size, and morphology were observed in both feeder layers. In addition, EBs expressed marker genes for the three germ layers cultured on both feeder cells. In conclusion, MBMCs are able to maintain hESCs in an undifferentiated state with comparable efficiency to MEFs. Therefore, MBMCs are a suitable alternative to animal-derived feeder layers for growing hESCs.

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.

Challenges to the clinical application of pluripotent stem cells: towards genomic and functional stability

Human embryonic stem cells (hESCs) can undergo unlimited self-renewal and are pluripotent, retaining the ability to differentiate into all cell types in the body. As a renewable source of various types of human cells, hESCs hold great therapeutic potential. Although significant advances have been achieved in defining the conditions needed to differentiate hESCs into various types of biologically active cells, many challenges remain in the clinical development of hESC-based cell therapy, such as the immune rejection of allogeneic hESC-derived cells by recipients. Breakthroughs in the generation of induced pluripotent stem cells (iPSCs), which are reprogrammed from somatic cells with defined factors, raise the hope that autologous cells derived from patient-specific iPSCs can be transplanted without immune rejection. However, recent genomic studies have revealed epigenetic and genetic abnormalities associated with induced pluripotency, a risk of teratomas, and immunogenicity of some iPSC derivatives. These findings have raised safety concerns for iPSC-based therapy. Here, we review recent advances in understanding the genomic and functional stability of human pluripotent stem cells, current challenges to their clinical application and the progress that has been made to overcome these challenges.

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.

Derivation and maintenance of undifferentiated human embryonic stem cells

Human embryonic stem cells (hESCs) are self-renewing, pluripotent cells derived from the inner cell mass of blastocysts, early-stage embryos, or blastomeres. hESCs can be propagated indefinitely in an undifferentiated state in vitro and have the ability to differentiate into all cell types of the body. Therefore, these cells can potentially provide an unlimited source of cells and hold promise for transplantation therapy, regenerative medicine, drug screening and discovery, and basic scientific research. Surplus human embryos donated for hESC derivation are extremely valuable, and inefficient derivation of hESCs would be a terrible waste of human embryos. Here, we describe a method for isolating hESC lines from human blastocysts with high efficiency. We also describe the methods for excising differentiated areas from partially differentiated hESC colonies and re-isolating undifferentiated hESCs from extremely differentiated hESC colonies.

Suspension bioreactor expansion of undifferentiated human embryonic stem cells

Embryonic stem cells (ESCs) are unique cells, which have the ability to differentiate into all cell types that comprise the adult organism. Furthermore, ESCs can infinitely self-renew under optimized conditions. These features place human ESCs (hESCs) in a position where these cells can be exploited for tissue engineering and regenerative medicine approaches in treating human degenerative disorders. However, cell therapy approaches will require large amounts of clinically useable cells, not typically achievable using standard static cell culture methods. Here, we describe a method wherein clinically relevant numbers of hESCs can be generated in a cost and time effective manner.

New culture system for human embryonic stem cells: autologous mesenchymal stem cell feeder without exogenous fibroblast growth factor 2

Human embryonic stem (hES) cells have been successfully maintained using human-cell feeder systems or feeder-free systems. However, despite advances in culture techniques, hES cells require supplementation with fibroblast growth factor 2 (FGF-2), an exogenous stemness factor, which is needed to sustain the authentic undifferentiated status. We developed a new culture system for hES cells; this system does not require supplementation with FGF-2 to obtain hES cells that are suitable for tissue engineering and regenerative medicine. This culture system employed mesenchymal stem cells derived from hES cells (hESC-MSCs) as autologous human feeder cells in the absence of FGF-2. The hES cell line SNUhES3 cultured in this new autologous feeder culture system maintained the typical morphology of hES cells and expression of pluripotency-related proteins, SSEA-4, TRA-1-60, OCT4, and alkaline phosphatase, without development of abnormal karyotypes after more than 30 passages. RNA expression of the pluripotency-related genes OCT4 and NANOG was similar to the expression in SNUhES3 cells maintained on xenofeeder STO cells. To identify the mechanism that enables the cells to be maintained without exogenous FGF-2, we checked the secretion of FGF-2 from the mitomycin-C treated autofeeder hESC-MSCs versus xenofeeder STO cells, and confirmed that hESC-MSCs secreted FGF-2 whereas STO cells did not. The level of FGF-2 in the media from the autofeeder system without exogenous FGF-2 was comparable to that from the xenofeeder system with addition of FGF-2. In conclusion, our new culture system for hES cells, which employs a feeder layer of autologous hESC-MSCs, supplies sufficient amounts of secreted FGF-2 to eliminate the requirement for exogenous FGF-2.

Laminin-511 expression is associated with the functionality of feeder cells in human embryonic stem cell culture

Fibroblast feeder cells play an important role in supporting the derivation and long term culture of undifferentiated, pluripotent human embryonic stem cells (hESCs). The feeder cells secrete various growth factors and extracellular matrix (ECM) proteins into extracellular milieu. However, the roles of the feeder cell-secreted factors are largely unclear. Animal feeder cells and use of animal serum also make current feeder cell culture conditions unsuitable for derivation of clinical grade hESCs. We established xeno-free feeder cell lines using human serum (HS) and studied their function in hESC culture. While human foreskin fibroblast (hFF) feeder cells were clearly hESC supportive, none of the established xeno-free human dermal fibroblast (hDF) feeder cells were able to maintain undifferentiated hESC growth. The two fibroblast types were compared for their ECM protein synthesis, integrin receptor expression profiles and key growth factor secretion. We show that hESC supportive feeder cells produce laminin-511 and express laminin-binding integrins α3ß1, α6ß1 and α7ß1. These results indicate specific laminin isoforms and integrins in maintenance of hESC pluripotency in feeder-dependent cultures. In addition, several genes with a known or possible role for hESC pluripotency were differentially expressed in distinct feeder cells.

Defined and serum-free media support undifferentiated human embryonic stem cell growth

Four commercially available serum-free and defined culture media tested on 2 human embryonic stem cell (hESC) lines were all found to support undifferentiated growth for >10 continuous passages. For hESC cultured with defined StemPro and mTeSR1 media, the cells were maintained feeder-free on culture dishes coated with extracellular matrices (ECMs) with no requirement of feeder-conditioned media (CM). For xeno-free serum replacer (XSR), HEScGRO, and KnockOut media, mitotically inactivated human foreskin feeders (hFFs) were required for hESC growth. Under the different media conditions, cells continued to exhibit alkaline phosphatase activity and expressed undifferentiated hESC markers Oct-4, stage-specific embryonic antigens 4 (SSEA-4), and Tra-1-60. In addition, hESC maintained the expression of podocalyxin-like protein-1 (PODXL), an antigen recently reported in another study to be present in undifferentiated hESC. The cytotoxic antibody mAb 84 binds via PODXL expressed on hESC surface and kills >90% of hESC within 45 min of incubation. When these cells were spontaneously differentiated to form embryoid bodies, derivatives representing the 3 germ layers were obtained. Injection of hESC into animal models resulted in teratomas and the formation of tissue types indicative of ectodermal, endodermal, and mesodermal lineages were observed. Our data also suggested that StemPro and mTeSR1 media were more optimal for hESC proliferation compared to cells grown on CM because the growth rate of hESC increased by 30%-40%, higher split ratio was thus required for weekly passaging. This is advantageous for the large-scale cultivation of hESC required in clinical applications.

Derivation of human embryonic stem cell lines after blastocyst microsurgery

Embryonic stem cells (ESCs) are derived from the inner cell mass (ICM) of the blastocyst. Because of their ability to differentiate into a variety of cell types, human embryonic stem cells (hESCs) provide an unlimited source of cells for clinical medicine and have begun to be used in clinical trials. Presently, although several hundred hESC lines are available in the word, only few have been widely used in basic and applied research. More and more hESC lines with differing genetic backgrounds are required for establishing a bank of hESCs. Here, we report the first Canadian hESC lines to be generated from cryopreserved embryos and we discuss how we navigated through the Canadian regulatory process. The cryopreserved human zygotes used in this study were cultured to the blastocyst stage, and used to isolate ICM via microsurgery. Unlike previous microsurgery methods, which use specialized glass or steel needles, our method conveniently uses syringe needles for the isolation of ICM and subsequent hESC lines. ICM were cultured on MEF feeders in medium containing FBS or serum replacer (SR). Resulting outgrowths were isolated, cut into several cell clumps, and transferred onto fresh feeders. After more than 30 passages, the two hESC lines established using this method exhibited normal morphology, karyotype, and growth rate. Moreover, they stained positively for a variety of pluripotency markers and could be differentiated both in vitro and in vivo. Both cell lines could be maintained under a variety of culture conditions, including xeno-free conditions we have previously described. We suggest that this microsurgical approach may be conducive to deriving xeno-free hESC lines when outgrown on xeno-free human foreskin fibroblast feeders.

Human embryonic fibroblasts support single cell enzymatic expansion of human embryonic stem cells in xeno-free cultures

The future application of human embryonic stem cells (hESC) for therapeutic approaches requires the development of xeno-free culture conditions to prevent the potential transmission of animal pathogens or xenobiotic substances to hESC. An important component of the majority of hESC culture systems developed is the requirement for fibroblasts to serve as feeders. For this purpose, several studies have used human foreskin fibroblasts established under xeno-free conditions. In this study we report xeno-free establishment and maintenance of human embryonic fibroblasts (XHEF) and demonstrate their ability to support long-term self-renewal of hESC under xeno-free culture conditions, using a commercially available complete medium. Importantly, our culture conditions allow enzymatic passaging of hESC. In contrast, hESC cultured on human foreskin fibroblasts (XHFF) under the same conditions were poorly maintained and rapidly subject to differentiation. Our study clearly shows that the source of human fibroblasts is essential for long-term xeno-free hESC maintenance.

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.

Reprogramming of human fibroblasts to induced pluripotent stem cells under xeno-free conditions

The availability of induced pluripotent stem cells (iPSCs) has created extraordinary opportunities for modeling and perhaps treating human disease. However, all reprogramming protocols used to date involve the use of products of animal origin. Here, we set out to develop a protocol to generate and maintain human iPSC that would be entirely devoid of xenobiotics. We first developed a xeno-free cell culture media that supported the long-term propagation of human embryonic stem cells (hESCs) to a similar extent as conventional media containing animal origin products or commercially available xeno-free medium. We also derived primary cultures of human dermal fibroblasts under strict xeno-free conditions (XF-HFF), and we show that they can be used as both the cell source for iPSC generation as well as autologous feeder cells to support their growth. We also replaced other reagents of animal origin (trypsin, gelatin, matrigel) with their recombinant equivalents. Finally, we used vesicular stomatitis virus G-pseudotyped retroviral particles expressing a polycistronic construct encoding Oct4, Sox2, Klf4, and GFP to reprogram XF-HFF cells under xeno-free conditions. A total of 10 xeno-free human iPSC lines were generated, which could be continuously passaged in xeno-free conditions and maintained characteristics indistinguishable from hESCs, including colony morphology and growth behavior, expression of pluripotency-associated markers, and pluripotent differentiation ability in vitro and in teratoma assays. Overall, the results presented here demonstrate that human iPSCs can be generated and maintained under strict xeno-free conditions and provide a path to good manufacturing practice (GMP) applicability that should facilitate the clinical translation of iPSC-based therapies.

Naturally immortalised mouse embryonic fibroblast lines support human embryonic stem cell growth

Human embryonic stem cell (hESC) growth is dependent on various factors released by feeder cells. Some of them have already been elucidated, although much research is still needed to understand the biology of stem cell maintenance in culture. Traditionally, primary mouse embryonic fibroblasts (PMEFs) have been used as feeder layers, and both murine and human fibroblast cell lines have been shown to support pluripotency and self-renewal of hESC. Here we report the derivation of three new mouse embryonic fibroblast cell lines, MEFLU-M, MEFLU-T, and MEFLU-TB, with different properties regarding growth and support for undifferentiated hESCs. MEFLU-TB is able to support continuous growth of the newly derived Man-1, as well as H1, HUES-1, HUES-7, HUES-8, and HUES-9 human embryonic stem cell lines. After more than 50 passages and doublings, MEFLU-TB feeders compare to early passage primary mouse embryonic fibroblasts in their ability to support undifferentiated hESC growth. Our results contradict a previous paradigm that PMEFs tend to lose their capacity to support proliferation of hESCs with increasing passages, and show that the MEFLU-TB mouse embryonic fibroblast cell line and its conditioned medium have the potential to support the maintenance of hESC lines. Also, our results clearly show that spontaneous immortalization of primary fibroblasts can be achieved in culture without any chemical addition or genetic modification.

Progress and future challenges in stem cell-derived liver technologies

The emergence of regenerative medicine has led to significant advances in the identification and understanding of human stem cells and adult progenitor cells. Both cell populations exhibit plasticity and theoretically offer a potential source of somatic cells in large numbers. Such a resource has an important role to play in the understanding of human development, in modeling human disease and drug toxicity, and in the generation of somatic cells in large numbers for cell-based therapies. Presently, liver transplantation is the only effective treatment for end-stage liver disease. Although this procedure can be carried out with high levels of success, the routine transplant of livers is severely limited by organ donor availability. As a result, attention has focused on the ability to restore liver mass and function by alternative approaches ranging from the bioartificial device to transplantation of human hepatocytes. In this review we will focus on the generation of human hepatic endoderm from different stem/progenitor cell populations with a view to its utility in regenerative medicine.

Strategies for future histocompatible stem cell therapy

Stem cell therapy based on the safe and unlimited self-renewal of human pluripotent stem cells is envisioned for future use in tissue or organ replacement after injury or disease. A gradual decline of regenerative capacity has been documented among the adult stem cell population in some body organs during the aging process. Recent progress in human somatic cell nuclear transfer and inducible pluripotent stem cell technologies has shown that patient-derived nuclei or somatic cells can be reprogrammed in vitro to become pluripotent stem cells, from which the three germ layer lineages can be generated, genetically identical to the recipient. Once differentiation protocols and culture conditions can be defined and optimized, patient-histocompatible pluripotent stem cells could be directed towards virtually every cell type in the human body. Harnessing this capability to enrich for given cells within a developmental lineage, would facilitate the transplantation of organ/tissue-specific adult stem cells or terminally differentiated somatic cells to improve the function of diseased organs or tissues in an individual. Here, we present an overview of various experimental cell therapy technologies based on the use of patient-histocompatible stem cells, the pending issues needed to be dealt with before clinical trials can be initiated, evidence for the loss and/or aging of the stem cell pool and some of the possible uses of human pluripotent stem cell-derivatives aimed at curing disease and improving health.