Stepwise differentiation of human adipose-derived mesenchymal stem cells toward definitive endoderm and pancreatic progenitor cells by mimicking pancreatic development in vivo.

Pancreatic progenitor (PP) cells are tissue-committed cells, which can differentiate into all kinds of pancreatic cells. They are potential candidates for regeneration of pancreatic tissue. However, it is unfeasible to acquire PP cells from pancreatic tissues and expand them in vitro. Generation of PP cells from adipose tissue-derived mesenchymal stem cells (AD-MSCs) would provide an unlimited source of PP cells. Here we developed a 2-step stepwise protocol, which induced AD-MSCs to generate FOXA2- or SOX17-positive definitive endoderm (DE) (5 days) and pancreatic and duodenal homeobox gene 1 (PDX1)-positive PP cells (4-6 days). By mimicking the developmental progress in embryonic development, we optimized the timing and combination of cytokines to activate the key signaling pathways during pancreatic development. We found that activating the Nodal/Activin signal with Activin A could induce differentiation of AD-MSCs toward DE, which could be further promoted by the Wnt signaling pathway activator Wnt3a. Besides, transient T (BRACHYURY)(+) mesendodermal cells were observed during formation of DE from AD-MSCs. Subsequently, the Wnt signaling pathway inhibitor Dkk1 along with retinoic acid/FGF2 (60 ng/mL) further induced AD-MSC-derived DE cells to differentiate into PDX1-positive PP cells. The derived PP cells were capable to form pancreatic endocrine or exocrine cells. In conclusion, we established a stepwise protocol that could derive DE and PP cells from AD-MSCs. It might provide an unlimited source of autologous PP cells for pancreatic diseases.