Canine induced pluripotent stem cells efficiently differentiate into definitive endoderm in 3D cell culture conditions using high-dose activin A

INTRODUCTION: Endoderm-derived organs support indispensable functions in the body. Pluripotent stem cells can generate endoderm-derived cells or tissues and have excellent therapeutic potential to replace the functions of endodermal tissues. However, there is no viable method to induce endodermal precursor cells, definitive endoderm (DE), from canine induced pluripotent stem cells (ciPSCs). METHODS: A ciPSC line was used in this study. In order to induce DE, ciPSCs were cultured with high dose activin A and fetal bovine serum. We considered the optimal differentiation period and starting cell density. Next, to reduce the remaining undifferentiated cells and improve the DE induction efficiency, DE was induced from 3D cell aggregates with knockout serum replacement instead of fetal bovine serum. Finally, hepatic and pancreatic induction were performed to investigate whether DE could differentiate into downstream lineages. RESULTS: After differentiation, some cells expressed the DE markers FOXA2 and SOX17. DE induction period and starting cell density were found to be important for efficient DE induction. However, some cells remained undifferentiated even after optimization of cell density and culture period. Cell differentiation under 3D culture conditions reduced undifferentiated cells and the replacement of fetal bovine serum with knockout serum replacement improved the DE induction efficiency. After hepatic and pancreatic induction, cells expressed some early hepatic and pancreatic markers. CONCLUSIONS: A ciPSC line was successfully differentiated to DE efficiently using a high dose of activin A with knockout serum replacement under 3D cell culture conditions. We believe that this study will be fundamental to achieving the generation of canine endodermal tissues from ciPSCs.