Methanol fixed feeder layers altered the pluripotency and metabolism of bovine pluripotent stem cells

Abstract: The pluripotency maintenance of pluripotent stem cells (PSCs) cultured in vitro requires the suitable microenvironment, which is commonly provided by the feeder layer. However, the preparation of feeder layer is time consuming and labor exhaustive. More importantly, the feeder cells treated with mitomycin or gamma-ray irradiation brings heterologous contamination to stem cells. The feeder-free PSC cultures are associated with high costs because of the requirement for additional supplements and special media. In this study, we characterize the pluripotency and metabolic status of bovine ESCs-F7 (classic bESCs lines, abbreviated as F7), which were cultured on methanol fixed mouse embryonic fibroblasts (MT-MEFs) or mitomycin C treated MEFs (MC-MEFs). MT-MEFs could be reused several times and were highly resistant to digestive enzymes. The relative expression levels of pluripotenct markers were different between F7 cultured on MT-MEFs (marked as MT-F7) and those cultured on the MC-MEFs (MC-F7). The long-term cultured MT-F7 cells formed embryoid bodies in vitro, showing the ability to differentiate into endodermal, ectodermal, and mesodermal germ layers like MC-F7. RNA-sequencing analysis showed that the replacement of the feeder layer from MC-MEFs to MT-MEFs lead to a novel steady transition of the F7, which included alteration of the expression patterns of genes that regulate pluripotency and metabolism. Further, the long-term cultured bovine expanded pluripotent stem cells (bEPSCs) on MT-MEFs (MT-bEPSCs) formed classical colonies, maintained pluripotency, and demonstrated elevated level of metabolic activity. In conclusion, this study demonstrated that methanol-fixed MEFs were efficient feeder layer that maintain the unique pluripotency and distinctive metabolic characteristics of the bPSCs cultured in vitro.