Long-term culture of Japanese human embryonic stem cells in feeder-free conditions

Transcriptome analysis of basic fibroblast growth factor treated stem cells isolated from human exfoliated deciduous teeth

Background

Basic fibroblast growth factor (bFGF) regulates cell proliferation, migration, and differentiation in various cell types. The aim of the present study was to determine the bFGF target genes in stem cells isolated from human exfoliated deciduous teeth (SHEDs).

Methods

Cells were isolated from pulp tissue obtained from exfoliated deciduous teeth. Mesenchymal stem cell surface markers and the differentiation potential toward adipogenic and neurogenic lineages were characterized. The bFGF-treated SHED transcriptome was examined using a high throughput RNA sequencing technique. The mRNA and protein expression of selected genes were evaluated using real-time polymerase chain reaction and immunofluorescence staining, respectively. Cell cycle analysis was performed by flow cytometry. The colony forming unit number was also examined.

Results

The isolated cells expressed CD44, CD90, CD105, but not CD45. The upregulation of adipogenic and neurogenic marker genes was observed after culturing cells in the appropriate induction medium. Transcriptome analysis of the bFGF treated cells revealed that the upregulated genes were in the cell cycle related pathways, while the downregulated genes were in the extracellular matrix related pathways. Correspondingly, bFGF induced MKI67 mRNA expression and Ki67 protein expression. Furthermore, bFGF treatment significantly decreased the G0/G1, but increased the G2/M, population in SHEDs. Colony formation was markedly increased in the bFGF treated group and was attenuated by pretreating the cells with FGFR or PI3K inhibitors.

Conclusion

bFGF controls cell cycle progression in SHEDs. Thus, it can be used to amplify cell number to obtain the amount of cells required for regenerative treatments.

Epithelial cells from oral mucosa: How to cultivate them?

Epithelial cells from oral mucosa (EOM) are responsible for important functions, like the primary protection of oral mucosa against external aggressions building a mechanical barrier against microorganisms, mechanical damage, toxic material, thermal regulation and secretion of different classes of inflammatory mediators. EOM could be an interesting tool for cellular and molecular biology research. Usually, EOM are collected by a painful and invasive process. In this study, we propose an alternative method to cultivate EOM collected by non-invasive scraping method of oral mucosa. Papanicolaou staining showed mainly two kinds of epithelial cell population after EOM scraping. As result of the five culture methods tested here, our results revealed that the EOM were successfully cultured on a murine feeder layer. In addition, EOM could be frozen and thawed, without morphology changes and loss of viability. Our findings suggest that EOM can be considered as a good cell source for many purposes, such as genetic studies, diagnosis and cell therapy.

Substrates for clinical applicability of stem cells

The capability of human pluripotent stem cells (hPSCs) to differentiate into a variety of cells in the human body holds great promise for regenerative medicine. Many substrates exist on which hPSCs can be self-renewed, maintained and expanded to further the goal of clinical application of stem cells. In this review, we highlight numerous extracellular matrix proteins, peptide and polymer based substrates, scaffolds and hydrogels that have been pioneered. We discuss their benefits and shortcomings and offer future directions as well as emphasize commercially available synthetic peptides as a type of substrate that can bring the benefits of regenerative medicine to clinical settings.

Low-molecular-weight inhibitors of cell differentiation enable efficient growth of mouse iPS cells under feeder-free conditions

Embryonic stem cells and induced pluripotent stem (iPS) cells are usually maintained on feeder cells derived from mouse embryonic fibroblasts (MEFs). In recent years, the cell culture of iPS cells under serum- and feeder-free conditions is gaining attention in overcoming the biosafety issues for clinical applications. In this study, we report on the use of multiple small-molecular inhibitors (i.e., CHIR99021, PD0325901, and Thiazovivin) to efficiently cultivate mouse iPS cells without feeder cells in a chemically-defined and serum-free condition. In this condition, we showed that mouse iPS cells are expressing the Nanog, Oct3/4, and SSEA-1 pluripotent markers, indicating that the culture condition is optimized to maintain the pluripotent status of iPS cells. Without these small-molecular inhibitors, mouse iPS cells required the adaptation period to start the stable cell proliferation. The application of these inhibitors enabled us the shortcut culture method for the cellular adaptation. This study will be useful to efficiently establish mouse iPS cell lines without MEF-derived feeder cells.

Human umbilical cord mesenchymal stem cells support nontumorigenic expansion of human embryonic stem cells

The expansion of pluripotent human embryonic stem cells (hESCs) requires a culture on feeder layers of mouse embryonic fibroblasts (MEFs). The culture model often causes immunogenic contaminations such as xenocarbohydrate, and inevitably forms teratoma in vivo. This study tested human umbilical cord-derived mesenchymal stem cells (HUCMSCs) as the feeder for hESCs. Wharton's jelly-derived HUCMSCs showed characteristics of MSCs and were easily maintained in a culture for over 20 passages. Under the mitomycin-inhibited HUCMSC feeder, hESCs maintained the features of embryonic stem cells (pluripotency and maintenance of normal karyotypes) after a prolonged culture of more than 20 passages. Notably, in extensive trials, no teratoma was formed in xenograft in NOD/SCID mice, but subsequent resumption of teratoma formation was noted upon transient coculturing with MEFs. Interestingly, among the four pluripotency-conferring genes, MYC and OCT4 were found to be downregulated in hESCs cocultured with HUCMSCs. Results of this study supported a nontumorigenic sustained culture of hESCs and did not form teratoma in vivo.

Feeder-free generation and long-term culture of human induced pluripotent stem cells using pericellular matrix of decidua derived mesenchymal cells

Human ES cells (hESCs) and human induced pluripotent stem cells (hiPSCs) are usually generated and maintained on living feeder cells like mouse embryonic fibroblasts or on a cell-free substrate like Matrigel. For clinical applications, a quality-controlled, xenobiotic-free culture system is required to minimize risks from contaminating animal-derived pathogens and immunogens. We previously reported that the pericellular matrix of decidua-derived mesenchymal cells (PCM-DM) is an ideal human-derived substrate on which to maintain hiPSCs/hESCs. In this study, we examined whether PCM-DM could be used for the generation and long-term stable maintenance of hiPSCs. Decidua-derived mesenchymal cells (DMCs) were reprogrammed by the retroviral transduction of four factors (OCT4, SOX2, KLF4, c-MYC) and cultured on PCM-DM. The established hiPSC clones expressed alkaline phosphatase, hESC-specific genes and cell-surface markers, and differentiated into three germ layers in vitro and in vivo. At over 20 passages, the hiPSCs cultured on PCM-DM held the same cellular properties with genome integrity as those at early passages. Global gene expression analysis showed that the GDF3, FGF4, UTF1, and XIST expression levels varied during culture, and GATA6 was highly expressed under our culture conditions; however, these gene expressions did not affect the cells’ pluripotency. PCM-DM can be conveniently prepared from DMCs, which have a high proliferative potential. Our findings indicate that PCM-DM is a versatile and practical human-derived substrate that can be used for the feeder-cell-free generation and long-term stable maintenance of hiPSCs.

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.

Stem cell research in cell transplantation: sources, geopolitical influence, and transplantation

If the rapidly progressing field of stem cell research reaches its full potential, successful treatments and enhanced understanding of many diseases are the likely results. However, the full potential of stem cell science will only be reached if all possible avenues can be explored and on a worldwide scale. Until 2009, the US had a highly restrictive policy on obtaining cells from human embryos and fetal tissue, a policy that pushed research toward the use of adult-derived cells. Currently, US policy is still in flux, and retrospective analysis does show the US lagging behind the rest of the world in the proportional increase in embryonic/fetal stem cell research. The majority of US studies being on either a limited number of cell lines, or on cells derived elsewhere (or funded by other sources than Federal) rather than on freshly isolated embryonic or fetal material. Neural, mesenchymal, and the mixed stem cell mononuclear fraction are the most commonly investigated types, which can generally be classified as adult-derived stem cells, although roughly half of the neural stem cells are fetal derived. Other types, such as embryonic and fat-derived stem cells, are increasing in their prominence, suggesting that new types of stem cells are still being pursued. Sixty percent of the reported stem cell studies involved transplantation, of which over three quarters were allogeneic transplants. A high proportion of the cardiovascular systems articles were on allogeneic transplants in a number of different species, including several autologous studies. A number of pharmaceutical grade stem cell products have also recently been tested and reported on. Stem cell research shows considerable promise for the treatment of a number of disorders, some of which have entered clinical trials; over the next few years it will be interesting to see how these treatments progress in the clinic.

Evaluation of 28 Human Embryonic Stem Cell Lines for Use as Unrelated Donors in Stem Cell Therapy: Implications of HLA and ABO Genotypes

For human embryonic stem cells (hESCs) to be used clinically, it is imperative that immune responses evoked by hESCs and their derivates after transplantation should be prevented. Human leukocyte antigens (HLA) and ABO blood group antigens are important histocompatibility factors in graft rejection. HLA matching between recipient and unrelated donors, in particular, is important in improving outcomes in hematopoietic cell transplantation (HCT). We have established and successfully maintained 29 hESC lines and analyzed the HLA and ABO genotypes of these lines. HLA-A, -B, -C and -DR (DRB1) genotyping was performed by polymerase chain reaction (PCR) sequence-based typing and ABO genotyping was carried out by PCR restriction fragment length polymorphism methods. To determine what proportion of the Korean population would be covered by these cell lines in organ transplantation, 27 cell lines with HLA-A, -B, and -DR data were evaluated for HCT (cord blood) donors and 28 cell lines with HLA-DR and ABO data were evaluated for solid organ (kidney) transplantation donors, and then compared the data with those from 6,740 donated cord bloods. When 2 HLA mismatches are allowed for HCT, as currently accepted for cord blood transplantation, it was estimated that about 16% and 25% of the possible recipients can find one or more donor cell lines with ≤2 mismatches at A, B, DRB1 allele level and at A, B antigen/DRB1 allele level, respectively. When HLA-DR antigen level matching and ABO compatibility was considered for solid organ (kidney) transplantation, it was estimated that about 29% and 96% of the possible recipients can find one or more ABO-compatible donor cell lines with 0 and 1 DR mismatches, respectively. We provided the first report on the HLA and ABO genotypes of hESC lines, and estimated the degree of HLA and ABO matching in organ transplantation for the Korean population.

Isolation and propagation of a human CD133(-) colon tumor-derived cell line with tumorigenic and angiogenic properties

It has been proposed in human colorectal cancers (CRC) a minority subset of cancer cells within tumors able to initiate tumor growth, defined as cancer stem cells (CSC). Solid human primary colonic and its ovarian metastatic cancer tissues were collected from fresh surgical samples and subsequent xenografts were established in nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice. The resulting tumors were disaggregated into single-cell suspensions and a CD133(-) cell line (NANK) was newly established and analyzed by flow cytometry. Surface markers of progenitor cells were immunophenotypically analyzed, and expression of stem cell and cancer-related genes was characterized. Secreted angiogenesis-associated molecules were investigated by proteomic array technology. Finally, different numbers of NANK were implanted and their tumor-initiating properties were investigated in NOD/SCID mice. Intraperitoneal injection of NANK in NOD/SCID mice induced tumors with developing progressive peritoneal dissemination and ascites. NANK cells maintained a differentiated phenotype and reproduced the full morphologic and phenotypic heterogeneity of their parental lesions. Noticeably, NANK lacked the expression of conventional CSC markers CD133 and CD44, self-renewal genes Oct-4 and Nanog, but showed the expression of an important gastrointestinal development marker CDX-2 and BMI-1 that is essential in regulating the proliferative activity of normal and leukemic stem cells. In addition, NANK secreted high amounts of important angiogenic cytokines. These results provide a novel and extensive model in human CSC for studying the generation and maintenance of phenotypic heterogeneity in CRC.

Worldwide Survey of Published Procedures to Culture Human Embryonic Stem Cells

Since their derivation 11 years ago, human embryonic stem (hES) cells have become a powerful tool in both basic biomedical research and developmental biology. Their capacity for self-renewal and differentiation into any tissue type has also brought interest from fields such as cell therapy and drug screening. We conducted an extensive analysis of 750 papers (51% of the total published about hES cells between 1998 and 2008) to present a spectrum of hES cell research including culture protocols developed worldwide. This review may stimulate discussions about the importance of having unvarying methods to culture hES cells, in order to facilitate comparisons among data obtained by research groups elsewhere, especially concerning preclinical studies. Moreover, the description of the most widely used cell lines, reagents, and procedures adopted internationally will help newcomers on deciding the best strategies for starting their own studies. Finally, the results will contribute with the efforts of stem cell researchers on comparing the performance of different aspects related to hES cell culture methods.