Effect of embryonic stem cell culture condition on the cellular identities of human amniotic fluid stem cells

Abstract

Amniotic fluid stem cells (AFSCs) offer therapeutic potential for prenatal and neonatal diseases based on their unique features. From the development of embryos, AFSCs represent a category between embryonic stem cells (ESCs) and mesenchymal stem cells (MSCs), with AFSCs more primitive than MSCs. Our lab has previously established that AFSCs can be reprogrammed to regain functional pluripotency with valproic acid (VPA). However, detailed mechanisms are still unknown. Here, our results showed that Wnt signalling was downregulated in the initial stage and upregulated with VPA treatment; whereas mesenchymal-to-epithelial transition (MET) was not observed in the process. Additionally, our previous results demonstrated that AFSCs maintained in ESC conditions shared 82% transcriptome similarity with ESCs. In the second part of this study, we revealed that features of AFSCs including marker expression and differentiation ability were sustained better in ESC conditions. Regarding osteogenesis, enhanced osteogenic ability was found in AFSCs maintained in ESC conditions due to a TGF-beta/CD73-dependent signalling pathway. Moreover, in addition to possessing the same tri-lineage differentiation capability as MSCs, AFSCs can also be induced to express cardiac markers, but contractile cells have not been obtained yet. As features of AFSCs are better preserved in ESC conditions, a Wnt-dependent cardiomyocyte differentiation protocol for pluripotent stem cells is examined on AFSCs in the last part of this study. Our results showed that, with the Wnt-dependent protocol, cardiac markers were induced but spontaneously contractile cells were not observed. Taken together, our findings show that (1) Wnt signalling may play a role in VPA-induced reprogramming, (2) AFSCs maintained in ESC conditions can better maintain stem cell features, especially osteogenic ability through a TGF-beta/CD73 pathway, (3) With a Wnt-dependent protocol, AFSCs can be induced to express cardiac markers but not to become contractile cells.