Natural killer (NK) cells are innate lymphocytes that aid in the protection of the host from infectious diseases and cancer. Regulation of cytotoxicity in NK cells is mediated by inhibitory receptors that bind major histocompatibility complex class I (MHC-I) molecules on target cells. Human myelogenous leukemia K562 cells are readily attacked by NK cells, because K562 cells expressed very low levels of MHC-I molecules for inhibitory NK cell receptors. In this study, we compared the ability of γ-irradiated- or mitomycin C (MMC)-treated K562 feeder cells to support expansion and activation of canine NK cells. We isolated CD5 negative cells from canine peripheral blood mononuclear cells by immunomagnetic separation and co-cultured with γ-irradiated (100 Gy)- or MMC (20 μg/mL)-treated K562 cells in the presence of interleukin (IL)-2, IL-15 and IL-21 for 21 days. As a result, number of CD5 negative cells, co-cultured with γ-irradiated- or MMC-treated K562 cells (56.72 ± 13.77 fold or 32.99 ± 10.83 fold), was increased than those of CD5 negetive cells (2.99 ± 1.42 fold). Also, we found that gene expression markers of activated NK cells such as NKp30, NKp44, NKp46, Ly49, NKG2D, CD244, perforin, and granzyme B and production of interferon gamma were similarly upregulated in NK cells co-cultured with γ-irradiated- or MMC-treated K562 cells, respectively. Next, we observed that cytotoxicity of NK cells co-cultured with γ-irradiated K562 cells was more sensitively reacted to canine mammary carcinoma cells than those of MMC-treated K562 cells. These results revealed that γ-irradiated K562 cells are more efficient feeder cells than MMC-treated K562 cells for enhancing NK cells expansion and activation.

The establishment of porcine embryonic stem cells (ESCs) from porcine somatic cell nuclear transfer (SCNT) blastocysts is influenced by in vitro culture day of porcine reconstructed embryo and feeder cell type. Therefore, the objective of the present study was to determine the optimal in vitro culture period for reconstructed porcine SCNT embryos and mouse embryonic fibroblast (MEF) feeder cell type for enhancing colony formation efficiency from the inner cell mass (ICM) of porcine SCNT blastocysts and their outgrowth. As the results, porcine SCNT blastocysts produced through in vitro culture of the reconstructed embryos for 8 days showed significantly increased efficiency in the formation of colonies, compared to those for 7 days. Moreover, MEF feeder cells derived from outbred ICR mice showed numerically the highest efficiency of colony formation in blastocysts produced through in vitro culture of porcine SCNT embryos for 8 days and porcine ESCs with typical ESC morphology were maintained more successfully over Passage 2 on outbred ICR mice-derived MEF feeder cells than on MEF feeder cells derived from inbred C57BL/6 and hybrid B6CBAF1 mice. Overall, the harmonization of porcine SCNT blastocysts produced through in vitro culture of the reconstructed embryos for 8 days and MEF feeder cells derived from outbred ICR mice will greatly contribute to the successful establishment of ESCs derived from porcine SCNT blastocysts.

Fish ovarian germline stem cells (OGSCs) that have the abilities to self-renew and differentiate into functional gametes can be used in various researches and applications. A main issue to be solved for effective utilization of fish OGSCs is the development of their stable in vitro culture condition, but only few researches about fish OGSC culture have been reported so far. In this study, in order to find the clues to develop the culture condition for OGSCs from Japanese medaka (Oryzias latipes), we tried to establish somatic cell lines as a candidate for the feeder cells and evaluated its supporting effects on the culture of ovarian cell populations from O. latipes. As the results, the somatic cell lines could be established only from the embryonic tissues among three tissues derived from embryos, fins and ovaries. Three embryonic cell lines were tested as a feeder cell for the culture of ovarian cell population and all three cell lines induced cell aggregation formation of the cultured ovarian cells whereas the feeder-free condition did not. Furthermore, a significant cellular proliferation was observed in the ovarian cells cultured on two of three cell lines. As a trial to increase the capacity of the cell lines as a feeder cell that supports the proliferation of the cultured ovarian cells, we subsequently established a stable line that expresses the foreign O. latipes fibroblast growth factor 2 (FGF2) from an embryonic cell line and evaluated its effectiveness as a feeder cell. The ovarian cells cultured on FGF2 expressing feeder cells still formed cell aggregates but did not show a significant increase in cellular proliferation compared to those cultured on non-transformed feeder cells. The results from this study will provide the fundamental information for in vitro culture of medaka OGSCs.

RNA Sendai virus (SeV) vector system has no risk of being integrated into the host genome. Sendai virus (SeV) vectors expressing pluripotent factors have been used to produce integration-free induced pluripotent stem cells (iPSCs) with high efficiency from various cell types in human and mouse. In this study, we generated iPSCs from pig ear fibroblast cells using the SeV vector expressing 4 human factors (POU5F1, SOX2, C-MYC, and KLF4). Colonies were emerged at Day 14 of transduction and expressed the classical pluripotency markers (POU5F1, NANOG, and SOX2) and surface marker (SSEA1). Furthermore, they showed a domed shape and could passage over 40 times under 2i (CHIR99021 and PD0325901)-LIF and MEF feeder culture condition having in vitro differentiation ability into 3 germ layers. Next, we examined the ability of six feeder free culture conditions to maintain piPSCs in a pluripotent state. piPSCs were plated on Matrigel coated dishes in different media: 1. CM: control media (LIF culture media); 2. CM-F: CM+100 ng Fetuin-A; 3. CM-N: CM+100 ng Nanog-TAT; 4. CM-2i: CM+3 uM CHIR99021+1 uM PD0325901; 5. CM-2iN: CM-2i+100 ng Nanog-TAT; 6. CM-2iN+100 ng Fetuin-A. However, piPSC could not maintain the typical self-renewal morphology on feeder free conditions regardless of culture media tested here. Further, expression of pluripotency-related genes (Oct4, Nanog and Klf4) of piPSCs cultured on feeder free conditions could not be compared with that of iPSCs cultured on MEF feeder plate. Our results suggest that integration free pluripotent stem cell from pigs could be generated by SeV vector system and maintained their pluripotency under 2i-LIF and MEF feeder culture condition, but further optimization of culture conditions may be required.

Embryonic stem cell classically cultured on feeder layer with FBS contained ES medium. Feeder-free mouse ES cell culture systems are essential to avoid the possible contamination of nonES cells. First we determined the difference between ES cell and MEF by Oct4 population. We demonstrate to culture and to induce differentiation on feeder free condition using a commercially available mouse ES cell lines.

Human embryonic stem cells (hESCs) have been routinely cultured on mouse embryonic fibroblast feeder layers with a medium containing animal materials. For clinical application of hESCs, animal-derived products from the animal feeder cells, animal substrates such as gelatin or Matrigel and animal serum are strictly to be eliminated in the culture system. In this study, we performed that SNUhES32 and H1 were cultured on human amniotic fluid cells (hAFCs) with KOSR XenoFree and a humanized substrate. All of hESCs were relatively well propagated on hAFCs feeders with xeno-free conditions and they expressed pluripotent stem cell markers, alkaline phosphatase, SSEA-4, TRA1-60, TRA1-81, Oct-4, and Nanog like hESCs cultured on STO or human foreskin fibroblast feeders. In addition, we observed the expression of nonhuman N-glycolylneuraminic acid (Neu5GC) molecules by flow cytometry, which was xenotransplantation components of contamination in hESCs cultured on animal feeder conditions, was not detected in this xeno-free condition. In conclusion, SNUhES32 and H1 could be maintained on hAFCs for humanized culture conditions, therefore, we suggested that new xenofree conditions for clinical grade hESCs culture will be useful data in future clinical studies.

Human embryonic stem (ES) cells are a potential source of cells for developmental studies and for a variety of applications in transplantation therapies and drug discovery. However, human ES cells are difficult to culture and maintain at a large scale, which is one of the most serious obstacles in human ES cell research. Culture of human ES cells on MEF cells after disassociation with accutase has previously been demonstrated by other research groups. Here, we confirmed that human ES cells (H9) can maintain stem cell properties when the cells are passaged as single cells under a feeder-free culture condition. Accutase-dissociated human ES cells showed normal karyotype, stem cell marker expression, and morphology. We prepared frozen stocks during the culture period, thawed two of the human ES cell stocks, and analyzed the cells after culture with the same method. Although the cells revealed normal expression of stem cell marker genes, they had abnormal karyotypes. Therefore, we suggest that accutase-dissociated single cells can be usefully expanded in a feeder-free condition but chromosomal modification should be considered in the culture after freeze-thawing.

This study was conducted to develop an efficient cryopreservation method of human embryonic stem (ES) cells using vitrification. In an initial experiment, sub-clumps of human ES cells (CHA-hES3 and CHA-hES4) were vitrified using grids after incubation with STO feeder cells for 1 or 16 h (Groups 1-1 and 1-2, respectively). After storage for months, thawed clumps were re-plated on a fresh feeder layer. The survival rates of warmed CHA-hES3 and CHA-hES4 cells of Group 1-2 were significantly higher than those of the corresponding Group 1-1 cells. In the second experiment, human ES cells were vitrified after incubation with feeder or feeder-conditioned medium (Groups 2-1 to -7). Relative mRNA expression of BM proteins and survival rates were increased following incubation of ES cells with fresh feeder cells for 16 h. In conclusion, increasing of tight adhesion between ES cells by extended incubation with feeder could reduce cryoinjury after vitrifying/warming.