Notch signaling partly regulates the osteogenic differentiation of retinoic acid-treated murine induced pluripotent stem cells

Notch signaling is involved in osteogenic differentiation; however, its role differs depending on cell type and differentiation stage. Here, we investigated the involvement of Notch signaling in the osteogenic differentiation of retinoic acid-treated embryoid bodies derived from mouse gingival fibroblast-derived induced pluripotent stem cells (mGF-iPSCs). When cultured in osteogenic media, mGF-iPSCs showed an increase in their expression of osteogenic marker genes and deposited a mineralized matrix. Furthermore, increased levels of mRNA for Notch1, Notch2, and Hey1 were observed. In the presence of DAPT, a Notch signaling inhibitor, during osteogenic induction, mRNA levels for osteogenic marker genes were significantly decreased; however, no difference was noted in mineral deposition. Moreover, activation of Notch signaling using Jagged1-immobilized surfaces resulted in a slight increase of in vitro mineralization on days 3 and 7 of osteogenic induction. Significant upregulation of Dlx5, Bsp, and Col I mRNA expression was observed in mGF-iPSCs cultured on Jagged1 surfaces. In conclusion, inhibition and activation of Notch signaling was shown to decrease and increase mGF-iPSC osteogenic differentiation, respectively. However, the responses were not robust, suggesting the involvement of additional signaling pathways.