Folic acid promotes proliferation and differentiation of porcine pancreatic stem cells into insulin-secreting cells through canonical Wnt and ERK signaling pathway.

Porcine pancreatic stem cells (pPSCs) can be induced to differentiate into insulin-producing cells in vitro and thus serve as a major cells source for β-cell regeneration. However, this application is limited by the weak cell proliferation ability and low insulin induction efficiency. In this study, we explored the role of folic acid in the proliferation of pPSCs and the formation of insulin-secreting cells. We found that FA-treated pPSCs cells had a high EDU positive rate, and the proliferation marker molecules PCNA, CyclinD1 and c-Myc were up-regulated, while the expression of folate receptor α (FOLRα) was up-regulated. In further research, interference FOLRα or adding canonical Wnt signaling pathway or ERK signaling pathway inhibitors could significantly inhibit the effect of FA on pPSCs proliferation. Meanwhile, during the differentiation of pPSCs into insulin-secreting cells, we found that the maturation marker genes Insulin, NKX6.1, MafA, and NeuroD1 was upregulated in insulin-secreting cell masses differentiationed from pPSCs after FA treatment, and the functional molecules Insulin and C-peptide were increased, the ability to secrete insulin in response to high glucose was also increased. With the addition of Wnt and ERK signaling pathway inhibitors, the pro-differentiation effect of FA was weakened. In conclusion, FA promotes the proliferation of pPSCs by binding to folate receptor α (FOLRα) and increase the efficiency of directed differentiation of pPSCs into insulin-producing cells by regulating canonical Wnt and ERK signaling pathway. This study lays theoretical foundation for solving the bottleneck in the treatment of diabetes with stem cell transplantation in future.