Long-Term Culture of Porcine Induced Pluripotent Stem-Like Cells Under Feeder-Free Conditions in the Presence of Histone Deacetylase Inhibitors

The reprogramming of somatic cells to induced pluripotent stem cells (iPSCs) is a complex process that involves significant epigenetic alterations in the reprogrammed cells. Epigenetic modifiers such as histone deacetylase (HDAC) inhibitors have been shown to increase the efficiency of derivation of iPSCs in humans and mice. In this study, we used three HDAC inhibitors, valproic acid, sodium butyrate, and suberoylanilide hydroxamic acid, together with ascorbic acid, for derivation and long-term feeder-free culture of porcine iPS-like cells. In the absence of exogenous growth factors and/or small molecules, these inhibitors were able to maintain the expression of key pluripotency markers, including genes known to be specific for naive pluripotent state in mouse stem cells, for over 60 passages under feeder-free conditions. Surprisingly, the cells became dependent on HDAC inhibitors for the maintenance of proliferation. Moreover, despite showing successful integration into blastocysts upon injection, the cells were unable to undergo normal differentiation in vitro and in vivo in the form of teratomas. Our results suggest that HDAC inhibitors maintain pluripotency gene expression of porcine iPSC-like cells in long-term culture, but prevent lineage specification, requiring further optimization of culture conditions for porcine iPSC derivation.