Maintenance of hPSCs under Xeno-Free and Chemically Defined Culture Conditions

Previously, the majority of human embryonic stem cells and human induced pluripotent stem cells have been derived on feeder layers and chemically undefined medium. Those media components related to feeder cells, or animal products, often greatly affect the consistency of the cell culture. There are clear advantages of a defined, xeno-free, and feeder-free culture system for human pluripotent stem cells (hPSCs) cultures, since consistency in the formulations prevents lot-to-lot variability. Eliminating all non-human components reduces health risks for downstream applications, and those environments reduce potential immunological reactions from stem cells. Therefore, development of feeder-free hPSCs culture systems has been an important focus of hPSCs research. Recently, researchers have established a variety of culture systems in a defined combination, xeno-free matrix and medium that supports the growth and differentiation of hPSCs. Here we described detailed hPSCs culture methods under feeder-free and chemically defined conditions using vitronetin and TeSR-E8 medium including supplement bioactive lysophospholipid for promoting hPSCs proliferation and maintaining stemness.

Establishment of STO Cell Lines Expressing Green Fluorescent Protein and Mouse Leukemia Inhibitory Factor / 中国实验血液学杂志

OBJECTIVE@#To establish the STO cell lines expressing green fluorescent protein (GFP) and mouse leukemia inhibitory factor (LIF) , and try to culture the mouse embryonic stem cells (mESCs) by using the established STO-GFP-mLIF cells as the feeder layer.@*METHODS@#The lentiviral particles containing GFP and mLIF and puromycin-resistance gene were constructed and transduced into STO cell lines. The cell lines stably expressing GFP and mLIF genes were screened out. The expression level of the inserted exogenous LIF gene was tested by Western blot and ELISA. The STO-GFP-mLIF cells were treated with different concentrations of mitomycin C (5, 10, 15, 20 µg/ml) for different time (1.5, 2.5, 3, 3.5 hours) to prepare feeder layers and the cell proliferation level on feeder layer was observed. Mouse embryonic stem cells were cultured on mitomycin C-treated feeder layer and the growth of cell colonies was observed.@*RESULTS@#The expression level of LIF protein in STO-GFP-mLIF cells was up-regulated, as compared with STO cells (P＜0.05). It was confirmed that the optimal concentration and time for inhibiting the proliferetion of STO-GFP-mLIF cells by mitomycin C were 10 µg/ml and 3 hours respectively. The observation also found that the embryonic stem cells could develop into typic "birdnest" shaped stem cell colony on mitomycin C-treated feeder layer.@*CONCLUSION@#The stable STO cell lines effectively expressing green fluorescent protein and mouse leukemia inhibitory factor have been established successfully, which can maintain the undifferentiated state of mouse embryonic stem cells.

Feeder Cells Free Rabbit Oral Mucosa Epithelial Cell Sheet Engineering

The optimal cell culture method of autologous oral mucosal epithelial cell sheet is not well established for a safe transplantation on to the patients' ocular surface. Animal serum and 3T3 mouse feeder cells are currently being used to stimulate the growth of the epithelial cells. However, the use of animal compounds can have potential side effects for the patient after transplantation of the engineered cell sheet. In the present study, we focused on engineering a rabbit oral mucosal epithelial cell sheet without 3T3 mouse feeder cells using a mix of Dulbecco's Modified Eagle Medium/Bronchial Epithelial Cell Growth Medium culture media (DMEM/BEGM). Autologous oral mucosal epithelial cell sheets, engineered with DMEM/BEGM feeder cell free culture media, were compared to those cultured in presence of serum and feeder cells. Using a DMEM/BEGM mix culture media, feeder cell free culture condition, autologous oral mucosal epithelial cells reached confluence and formed a multilayered sheet. The phenotype of engineered cell sheets cultured with DMEM/BEGM were characterized and compared to those cultured with serum and feeder. Hematoxylin and eosin staining showed the formation of a similar stratified multilayer cell sheets, in both culture conditions. The expression of deltaN-p63, ABCG2, PCNA, E-cadherin, Beta-catenin, CK3, CK4, CK13, Muc5AC, was similar in both culture conditions. We demonstrated that rabbit autologous oral mucosal epithelial cell sheet can be engineered, in feeder cell free conditions. The use of the DMEM/BEGM culture media to engineer culture autologous oral mucosa epithelial cell sheet will help to identify key factors involved in the growth and differentiation of oral mucosal epithelial cells.

Development of NK cell expansion methods using feeder cells from human myelogenous leukemia cell line

BACKGROUND: Natural killer (NK) cells constantly survey surrounding tissues and remove newly generated cancer cells, independent of cancer antigen recognition. Although there have been a number of attempts to apply NK cells for cancer therapy, clinical application has been somewhat limited because of the difficulty in preparing a sufficient number of NK cells. Therefore, ex vivo NK cell expansion is one of the important steps for developing NK cell therapeutics. METHODS: CD3+ depleted lymphocytes were cocultured with IL-2 and with feeder cells (peripheral blood mononuclear cells [PBMCs], K562, and Jurkat) for 15 days. Expanded NK cells were tested for cytotoxicity against cancer cell lines. RESULTS: We compared feeder activities of three different cells-PBMC, K562, and Jurkat. K562 expanded NK cells by almost 20 fold and also showed powerful cytotoxic activity against cancer cells. K562-NK cells remarkably expressed the NK cell activation receptors, NKG2D, and DNAM-1. K562-NK cells exhibited more than two-fold production of cytotoxic granules compared with Jurkat-NK cells, producing more perforin and granzyme B than naive NK cells. CONCLUSION: Our findings suggest that K562 are more efficient feeder cells than Jurkat or PBMCs. K562 feeder cells expanded NK cells by almost 20 fold and showed powerful cytotoxic activity against cancer cells. We herein propose an intriguing approach for a design of NK cell expansion.

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.

Overexpression of bone morphogenetic protein 4 in STO fibroblast feeder cells represses the proliferation of mouse embryonic stem cells in vitro

Embryonic stem cells (ESCs) can be propagated in vitro on feeder layers of mouse STO fibroblast cells. The STO cells secrete several cytokines that are essential for ESCs to maintain their undifferentiated state. In this study, we found significant growth inhibition of mouse ESCs (mESCs) cultured on STO cells infected with adenovirus containing a dominant-negative mutant form of IkappaB (rAd-dnIkappaB). This blockage of the NF-kappaB signal pathway in STO cells led to a significant decrease in [3H]thymidine incorporation and colony formation of mESCs. Expression profile of cytokines secreted from the STO cells revealed an increase in the bone morphogenetic protein4 (BMP4) transcript level in the STO cells infected with adenoviral vector encoding dominant negative IkappaB (rAd-dnIkappaB). These results suggested that the NF-kappaB signaling pathway represses expression of BMP4 in STO feeder cells. Conditioned medium from the rAd-dnIkappaB-infected STO cells also significantly reduced the colony size of mESCs. Addition of BMP4 prevented colony formation of mESCs cultured in the conditioned medium. Our finding suggested that an excess of BMP4 in the conditioned medium also inhibits proliferation of mESCs.

Engineering Biomaterials for Feeder-Free Maintenance of Human Pluripotent Stem Cells

Human pluripotent stem cells (hPSCs) are capable of differentiating into any type of somatic cell, a characteristic that imparts significant therapeutic potential. Human embryonic stem cells and induced pluripotent stem cells are types of hPSCs. Although hPSCs have high therapeutic potential, their clinical relevance is limited by the requirement for animal feeder layers, which maintain their pluripotency and self-renewal. hPSCs grown on animal feeder cells are at high risk for pathogen contamination and can be affected by the immunogenicity of the feeder layer. The presence of animal feeder cells also limits the scalability of hPSCs in culture because of the high cost of culturing and batch-to-batch variations. Therefore, development of feeder-free systems is imperative for robust, lower-cost, xeno-free, scalable culture of hPSCs. Biomaterials engineered with bioactive molecules such as adhesion proteins and extracellular matrix proteins, or synthetic materials such as peptides and polymers, may provide alternative substrates to animal feeder cells. This article reviews biomaterial-based, feeder-free systems for hPSC growth and maintenance, which provide clinically relevant alternatives to feeder cell systems.

Role of microenvironment in the process of expansion of late endothelial progenitor cell in vitro / 中国医学科学院学报

<p><b>OBJECTIVE</b>To study the role of the feeder layer cells as niche in the process of expansion of late endothelial progenitor cell in vitro.</p><p><b>METHODS</b>We cultured mononuclear cells (MNC)from human peripheral blood (PB)on the plate with the feeder layer cells which were irradiated late endothelial progenitor cells(EPC)or human umbilical vein endothelial cells (HUVEC) by EGM-2. After 21 days, the numbers of obtained late EPC colonies were counted separately, and their surface antigen of the late EPC was verified by fluorescence-activated cell sorter (FACS) analysis, and their ability of forming vessel structure with Matrigel in vitro. The differentiation of single stem cell on the feeder layer cell was traced by video-microscopy.</p><p><b>RESULTS</b>After 21 days of culture,(40.0±3.9)and(39.3±3.1)late EPC colonies that MNC of a hundred milliliter PB were cultured, respectively, on the feeder layer cells of EPC and HUVEC were much more than (2.0±1.3) colonies cultured on without the feeder layer cells (all P <0.05). These cells also expressed CD31,CD34,eNOS,FLt-1,P1H12,Sendo,VE cadherin,and CD117, as shown by FACS analysis. Furthermore, they formed vessel structure with Matrigel in vitro. The video-microscopy showed the asymmetric cell division was participated by the feeder layer cell during the expansion of single stem cell.</p><p><b>CONCLUSION</b>The massive expansion of late EPC can be achieved by the provision of the feeder layer cells, which may be involved in the stem cell asymmetric cell division.</p>

Inducing maturation of monocyte-derived dendritic cells on human epithelial cell feeder layer

Nowadays, dendritic cells [DCs] have a special place in cancer treatment strategies and they have been used for tumor immunotherapy as they can induce immune response against tumor cells. Researchers have been trying to generate efficient dendritic cells in vitro; therefore, this research was done to generate them for use in research and tumor immunotherapy. This study took place at Urmia University in 2010-2011 years. In this study plastic adherent monocytes were incubated with granulocyte-macrophage colony stimulating factor [GM-CSF] and interleukin-4 [IL-4] for five days. Finally, fully matured and stable DCs were generated by 48 hours of incubation in a monocyte conditioned medium [MCM] containing tumor necrosis factor-alpha [TNF-alpha] and epithelial cells. Phenotypic and functional analysis were carried out by using anti-CD 14, anti-CD80, anti-CD86, and anti-CD83 monoclonal antibodies, and by determining their phagocytic activity, mixed lymphocyte reaction [MLR] and cytokine production, respectively. Dendritic cells were produced with high levels of surface molecule, i.e. of CD80, CD83, CD86, HLA-DR, expression and low levels of CD14 expression. Dendritic cells showed efficient phagocytosis and ability to stimulate T-lymphocytes. Moreover, dendritic cells could secrete high levels of interleukin-12 [IL-12] cytokine which was depictive of their full maturation. Measurement of the produced cytokines showed the generation of type-1 dendritic cells [DC1]. Our study showed that skin epithelial cells could induce maturation of monocyte-derived dendritic cells [DCs]. This feeder layer led to the production of efficient dendritic cells with the ability to be used for tumor immunotherapy

Comparison of neonatal and adult mice-derived sertoli cells in support of expansion of mouse spermatogonial stem cells in vitro

Background: This study compared neonatal and adult mice-derived Sertoli cells [NSCs and ASCs] to examine the influence of feeder cells derived from donors of different ages on the maintenance of mouse spermatogonial stem cells [SSCs] in vitro

Materials and Methods: SSCs were derived from the testes of six-day-old mice. They were subsequently transferred to Sertoli cells which were isolated by datura stramonium agglutinin [DSA] lectin from neonatal and adult mice for five days

Results: The numbers of spermatogonial colonies, the numbers of cells per colony, and cloning efficiency were assessed in presence of NSCs and ASCs. The expression of alpha 6-and beta 1-integrin-positive cells was evaluated. Moreover, the functionality of the cells was assessed by their transplantation into the testes of busulfan-induced infertile mice. Colony efficiency assay showed that the number of colonies derived from single spermatogonial cells were significantly higher on NSCs. Additionally, the transplantation of dissociated colonies into the testes of busulfan-induced infertile mice showed their migration to the seminiferous basal membrane

Conclusion: These results show that NSCs may provide a more favorable microenvironment in comparison with ASCs for in vitro culture of spermatogonial colonies

Different types of feeder cells for maintenance of human embryonic stem cells / 中国医学科学院学报

<p><b>OBJECTIVE</b>To compare the effects of different types of feeder cells on supporting undifferentiation and high proliferation of human embryonic stem cells (hESC).</p><p><b>METHODS</b>hESC were seeded on mouse embryonic fibroblasts (MEF), human marrow stromal cells (hMSC), and human foreskin fibroblasts (hFF), respectively. Colony number, cell quantity after digestion, and survival rate were observed by alkaline phosphatase (AP) staining and Trypan blue, and the biological properties of hESC after 5 passages were observed by immunofluorescence staining.</p><p><b>RESULTS</b>Although all the three feeder layers could support the formation of hESC colonies and maintain pluripotency, the morphology of colonies on different feeder layers remarkably varied. The stage-specific embryonic antigen-3 and AP staining were positive on three types of feeders. The number of colonies, number of cells produced, and cell survival rates were significantly higher on MEF than on human feeder cells (P < 0.01). Furthermore, the number of AP-positive colonies and cell quantity were also significantly higher on hMSC than on hFF (P < 0.01).</p><p><b>CONCLUSIONS</b>All three types of feeder cells are able to support the growth of hMSC, although MEF are more favourable for the proliferation. Two types of human feeder cells lay the foundation for the removal of animal-derived hESC culture system. hMSC is superior to hFF in supporting the proliferation of hESC.</p>

Establishment and Characterization of an In Vitro Model for Cholesteatoma

OBJECTIVES: Experimental models are of importance to study the pathogenesis of middle ear cholesteatoma, however, they were not established until now. We aimed to develop in vitro model of middle ear cholesteatoma using primary keratinocytes and fibroblasts isolated from cholesteatoma tissue. HaCaT cell line was used as a "skin equivalent" and to compare the grade of homogeneity between cholesteatoma keratinocytes and HaCaT cells. METHODS: Primary keratinocytes were isolated from cholesteatoma tissue, co-cultured with preliminary prepared feeder layer from cholesteatoma fibroblasts and subsequently air-exposed. The protein profile of cholesteatoma keratinocytes and HaCaT cells was evaluated by means of immunoblot using monoclonal antibody against cytokeratin (CK) 13 and 16. Tissue localization of CK 13 and 16 was accomplished with immunohistochemistry. RESULTS: Different protein profile and stronger expression of CK 13 and 16 were demonstrated in cholesteatoma keratinocytes in comparison with HaCaT cells. Bigger stratification was observed in the 3D-in vitro systems when both cholesteatoma keratinocytes and HaCaT cells were respectively co-cultured with fibroblasts in comparison with the corresponding control groups without fibroblasts. CONCLUSION: 3D-model demonstrates the significance of intercellular interaction between components of cholesteatoma tissue.

Establishment of Embryonic Stem Cell Line from Isolated Blastomeres from Mouse Preimplantation Embryos / 대한불임학회지

OBJECTIVE: The aim of this study was to investigate whether embryonic stem (ES) cells can be established from isolated blastomeres of mouse embryos. METHODS: Blastomeres were separated from mouse (C57Bl/6J) 2- or 4-cell embryos. Isolated blastomeres or whole 4-cell embryos were co-cultured with mitosis-arrested STO feeder cells in DMEM supplemented with recombinant murine leukemia inhibitory factor and ES-qualified fetal bovine serum. After the tentative ES cell lines were maintained from isolated blastomeres or whole embryos, some of them were frozen and the others were sub-cultured continually. Characteristics of tentative ES cell lines as were evaluated for specific gene expressions with immunocytochemistry and RT-PCR. RESULTS: One ES cell line (3.0%) was established from isolated blastomere of 2-cell embryo and one cell line (4.0%) from isolated two blastomeres of 4-cell embryo. And five cell lines (16.7%) were established from whole 4-cell embryos. Both cell lines from isolated blastomere and whole embryo expressed mouse ES cells specific markers such as SSEA-1, Oct-4 and alkaline phosphatase. Marker genes of three germ layers were expressed from embryoid bodies of both cell lines. CONCLUSION: This study suggests that mouse ES cells could be established from isolated blastomeres, although the efficiency is lower than whole embryos. This animal model could be applied to establishment of autologous human ES cells from biopsied blastomeres of preimplantation embryos in human IVF-ET program.

Effect of the Isolation Method of Mouse Inner Cell Mass, Types of Feeder Cells and Treatment Time of Mitomycin C on the Formation Rate of ICM Colony / 대한불임학회지

OBJECTIVE: This study was carried out to evaluate the effect of the isolation methods of inner cell mass from mouse blastocyst, types of feeder cells and treatment time of mitomycin C on the formation rate of ICM colony. METHODS: The inner cells were isolated by conventional immunosurgery, partial trophoblast dissection with syringe needles and whole blastocyst co-culture method. Commercially available STO and primary cultured mouse embryonic fibroblast (pMEF) feeder cells were used, and mitomycin C was treated for 1, 2 or 3 hours, respectively. The formation rate of ICM colony was observed after isolation of ICM and culture of ICM on the feeder cells for 7 days. RESULT: The ICM colony formation rate on STO were significantly higher in partial trophoblast dissection group (58%) than that in immunosurgery (12%) or whole blastocyst culture (16%) group (p<0.05). The formation rate on pMEF feeder layer was higher in partial trophoblast dissection (88%) and whole blastocyst culture (82%) group than that in immunosurgery (16%) group (p<0.05). When mitomycin C treated to pMEF for 2 hours, the formation rate of 88% was significantly higher than those of other conditions. CONCLUSIONS: Above results showed that the efficient isolation method of ICM from blastocyst was the partial trophoblast dissection and the appropriate treatment time of mitomycin C was 2 hours. However, the subculture of ICM colony and characterization of stem cells should be carried out to confirm the efficacy of the partial trophoblast dissection method.

Establishment of Human Embryonic Stem Cells using Mouse Embryonic Fibroblasts and Human Fetal Fibroblasts as Feeder Cells / 대한불임학회지

OBJECTIVES: This study was carried out to establish human embryonic stem cells derived from frozen-thawed embryos using mouse embryonic fibroblasts (mEFs), human fetal skin and muscle fibroblasts as feeder cells, and to identify the characteristic of embryonic stem cells. METHODS: When primary mEFs, human fetal skin and muscle fibroblasts were prepared, passaging on 4 days from replating could have effective trypsinization and clear feeder layers. Eight of 23 frozenthawed 4~8 cell stage embryos donated from consenting couples developed to blastocysts. Inner cell mass (ICM) was isolated by immunosurgery. ICM was co-cultured on mEFs, human fetal skin or muscle fibroblasts. The ICM colonies grown on mEFs, human fetal skin or muscle fibroblasts were tested the expression of stage specific embryonic antigen-3, -4 (SSEA-3, -4), octamer binding transcription factor-4 mRNA (Oct-4) and alkaline phosphatase surface marker. RESULTS: We obtained 1 ICM colony from 2 ICM co-cultured on mEFs as feeder cells and did not obtain any ICM colony from 6 ICM clumps co-cultured on human fetal skin or muscle fibroblasts. The colony formed on mEFs could be passaged 30 times every 5 days with sustaining undifferentiated colony appearance. When the colonies cultured on mEFs were grown on human fetal skin or muscle fibroblasts, the colonies could be passaged 15 times every 9 days with sustaining undifferentiated colony appearance. The colonies grown on mEFs and human fetal fibroblasts expressed SSEA-4 and alkaline phosphatase surface markers and positive for the expression of Oct-4 by reverse transcription-polymerase chain reaction (RT-PCR). The produced embryoid body differentiated spontaneously to neural progenitorlike cells, neuron-like cells and beating cardiomyocyte-like cells, and frozen-thawed embryonic stem cells displayed normal 46, XX karyotype. CONCLUSIONS: The human embryonic stem cells can be established by using mEFs and human fetal fibroblasts produced in laboratory as feeder cells.

Effects of Keratinocyte Growth Factor (KGF), Epidermal Growth Factor (EGF), and Extracellular Calcium on the Growth of Cultured Psoriatic Keratinocytes / 대한피부과학회지

We investigated the effects of KGF and EGF, together with extracellular calcium, on the growth of cultured psoriatic keratinocytes, in order to establish a new chemically defined medium for culturing psoriatic keratinocytes using a modified form of MCDB 153 media. We compared the cell growth pattern under various culture conditions, including growth factors (KGF or EGF), and extracellular calcium concentrations, attachment and/or matrix factors (type I collagen coating or 3T3 fibroblast layering), culture durations, and types of cultured cells such as normal human epidermal keratinocytes (NHEK) and psoriatic keratinocytes. In order to achieve the above objective, semiquantitative RT-PCR for K16 mRNA, direct immunofluorescence with K8.12 as the markers of regenerating keratinocytes, and microscopic observation for cell colony formation were performed. The results are summarized as follows: 1. Psoriatic keratinocytes were grown optimally at 0.15 mM calcium, irrespective of growth factors or even in free control. They also grew well at 20 nM KGF. 2. KGF and/or EGF played an active role in cell growth, especially in the 5 days' culture. The growth stimulatory effect of EGF was suppressed by 0.5 mM calcium, but the effect of KGF was sustained at this calcium concentration. Furthermore, KGF exhibited a cell Survival effect of 18 days on type I collagen coating, and also in 12 days' culture on 3T3 fibroblast layering. 3. Cultured psoriatic keratinocytes were more vulnerable to extracellular calcium than NHEK with regard to optimal calcium concentration; they grew best at 0.15 mM, which was much lower than 1.5 mM in NHEK. 4. 3T3 fibroblasts exerted a favorable effect on cell growth and survival, especially in 12 days' culture, which may have been due to the paracrine effect of endogenous KGF from the 3T3 feeder cells, and cell reattachment/pile-up properties. To improve the culture method for psoriatic keratinocytes, the study suggests we should consider the optimal extracellular calcium concentration, introduce feeder cell layering to increase cell reattachment/pile-up, and supplement the mesenchymal paracrine growth factors such as KGF to exert a favorable effect on cell growth and survival.

Formation of basement membrane and stratification of Rabbit oral keratinocytes cultured on human acellular dermal matrix

Induced Differentiation of Embryonic Stem Cells to Insulin Secreting Cells / 대한불임학회지

OBJECTIVE: Embryonic stem (ES) cells could be differentiated into the specific cell types by alternation of culture condition and modification of gene expression. This study was performed to evaluate the differentiation protocol for mouse and human ES cells to insulin secreting cells. METHODS: Undifferentiated mouse (JH-1) and human (Miz-hES1) ES cells were cultured on STO feeder layer, and embryoid bodies (EBs) were formed by suspension culture. For the differentiation, EBs were cultured by sequential system with three stage protocol. The differentiating ES cells were collected and marker gene expressions were analyzed by semi-quantitative RT-PCR in each stage. Amount of secreted insulin levels in culture media of human ES cells were measured by human insulin specific RIA kit. RESULTS: During the differentiation process of human ES cells, GATA-4, alpha-fetoprotein, glucose transporter-2 and Ngn-3 expression were increased whereas Oct-4 was decreased progressively. Insulin and albumin mRNAs were expressed from stage II in mouse ES cells and from stage III in human ES cells. We detected 3.0~7.9 microU/ml secretion of insulin from differentiated human ES cells by in vitro culture for 36 days. CONCLUSION: The sequential culture system could induce the differentiation of mouse and human ES cells into insulin secreting cells. This is the first report of differentiation of human ES cells into insulin secreting cells by in vitro culture with serum and insulin free medium.

Human Amniotic Fluid Cells Support Expansion Culture of Human Embryonic Stem Cells / 대한불임학회지

OBJECTIVE: This study was performed to evaluate the possibility of prolonged culture of human embryonic stem cells (hESC; SNUhES2) on human amniotic fluid cells (hAFC), which had been storaged after karyotyping. METHOD: The hAFC was prepared for feeder layer in the presence of Chang's medium and STO medium (90% DMEM, 10% FBS) at 37degrees C in a 5% CO2 in air atmosphere. Prior to use as a feeder layer, hAFC was mitotically inactivated by mitomycin C. The hESCs on hAFC were passaged mechanically every seven days with ES culture medium (80% DMEM/F12, 20% SR, bFGF). RESULTS: The hAFC feeder layer support the growth of undifferentiated state of SNUhES2 for at least 59 passages thus far. SNUhES2 colonies on hAFC feeder appeared slightly angular and flatter shape as compared with circular and thicker colonies observed with STO feeder layer and showed higher level with complete undifferentiation in seven days. Like hESC cultured on STO feeders, SNUhES2 grown on hAFC expressed normal karyotype, positive for alkaline phosphatase activity, high telomerase activity, Oct-4, SSEA-3, SSEA-4, Tra-1-60 and Tra-1-81 and formed embryoid bodies (EBs). CONCLUSION: The hAFC supports undifferentiated growth of hESC. Therefore, these results may help to provide a clinically practicable method for expansion of hESC for cell therapies.

Telomerase: Key to Mortal or Immortal Road

Gradual attrition of telomere to a critical short length elicits successive cellular response of cellular senescence and crisis. Cancer cells evade this process by maintaining functional telomeres via one of two known mechanisms of telomere maintenance. The first and most frequent mechanism involves reactivation of enzyme activity of telomerase, a ribonucleoprotein complex mainly via transcriptional up-regulation of TERT, a catalytic subunit of telomerase complex. The second mechanism utilizes telomerase-independent way termed ALT (for Alternative Lengthening of Telomere), which possibly involves recombination pathways. Thus master key for cellular immortalization is supposed to possess adequate telomere reserves. Indeed, telomerase can alone induce the immortalization under culture on feeder cell layers without generally known inactivation mechanism of tumor suppressor genes. Including this phenomena, this review will focus on telomerase and telomere-associated proteins, thereby implication of these proteins for cellular immortalization processes.