Undifferentiated Propagation of the Human Embryonic Stem Cell Lines, H1 and HSF6, on Human Placenta-derived Feeder Cells Without Basic Fibroblast Growth Factor Supplementation

In order for human embryonic stem cells (hESCs) to be cultured on mouse embryonic fibroblast (MEFs) feeder cells, continuous basic fibroblast growth factor (bFGF) supplementation is required. However, the role of bFGF in a culture system using human-derived feeder cells has not been evaluated until now. In this study, we propagated the widely used hESC lines, H1 and HSF6, on human placenta-derived feeder cells (HPCs) without exogenous bFGF supplementation, and were able to propagate hESCs on HPC feeders up to 50 passages. The absence of bFGF in culture media did not interrupt the undifferentiated propagation and the expression of pluripotent stem cell markers ALP, SSEA-4, TRA-60, Oct-4, Nanog, and Rex-1, as well as the formation of embryoid bodies (EBs) and their differentiation potential. In contrast, hESCs cocultured with MEF feeders could not propagate and form EBs without exogenous bFGF supplementation. Expression of bFGF and the activation of the ERK1/2-c-Fos/c-Jun pathway, which is known as the signaling pathway of bFGF, were identifiable not only in hESCs cultured in bFGF-containing media regardless of feeder cell type, but also in hESCs cocultured with HPC feeder cells in media without bFGF. These findings may support the hypothesis that HPC feeder cells enhance endogenous bFGF production and activation of the ERK1/2-c-Fos/c-Jun pathway, which suggests that HPCs have an additional advantage in their hESC propagation compared with MEF.