Investigation of the optimal suspension culture time for the osteoblastic differentiation of human induced pluripotent stem cells using the embryoid body method

The differentiation of human induced pluripotent stem cells (hiPSCs) into osteoblasts provides a new paradigm in the field of bone tissue regeneration. The embryoid body (EB) differentiation method is commonly used for the osteogenic differentiation of hiPSCs. However, the spontaneous differentiation process of EBs is poorly understood, as evidenced by the inconsistency of the suspension time among previously reported studies as well as the low osteoblastic differentiation efficiency of hiPSCs. In the present study, we investigated the effects of the suspension culture time of EBs on the osteogenic differentiation of hiPSCs. Under chemically defined conditions, the expression of key genes related to presomitic mesoderm, neural crest, mesenchymal and pre-osteoblast cells in EBs derived from hiPSCs was examined daily by quantitative RT-PCR. Then, EBs with varying times in suspension (3, 5, 7 or 10 days) were attached onto gelatine surfaces, and their osteoblastic differentiation efficiencies after 14 days of culture in osteogenic induction medium were determined. Our results showed that EBs derived from hiPSCs subjected to 4 days of suspension culture produced the most mesenchymal stem cells, and exhibited the best osteogenic differentiation efficiency. Our research is valuable to standardizing, the time in suspension for the osteogenic differentiation of hiPSCs through the EB method, and facilitated the development of a high-efficiency in vitro osteogenic differentiation system for hiPSCs.