Semaphorin 3A-hypoxia inducible factor 1 subunit alpha co-overexpression enhances the osteogenic differentiation of induced pluripotent stem cells-derived mesenchymal stem cells in vitro

Background: Mesenchymal stem or stromal cells (MSCs) derived from the induced pluripotent stem cells (iPSCs) have uniform biological activity, which makes the clinical application of MSCs in bone repair possible. Culturing the iPSC-MSCs onto osteoconductive materials is a promising tissue engineering-based strategy in bone regeneration. The aim of this work was to evaluate the effects of semaphorin 3A (Sema3A) and hypoxia inducible factor 1 subunit alpha (HIF1 alpha) co-overexpression on the survival and osteogenic differentiation of iPSC-MSCs. Methods: Sema3A and HIF1 alpha were linked together with the three (GGGGS; G, glycine; S, serine) peptide fragment, and their co-expression in iPSC-MSCs was mediated by a lentiviral vector. The fusion protein retained the immune reactivity for both Sema3A and HIF1 alpha as determined with Western blotting. iPSC-MSCs were infected with overexpression lentivirus (oeLenti) as negative control, oeLenti-Sema3A, oeLenti-HIF1 alpha or oeLenti-Sema3A-HIF1 alpha lentiviruses. Results: Sema3A overexpression alone promoted the osteogenic differentiation of iPSC-MSCs (the activity and/or expression of osteoblast markers, such as alkaline phosphatase, osteopontin, and osteocalcin, were upregulated), and suppressed cell survival. The Sema3A-HIF1 alpha fusion protein showed a comparable osteoconductive effect to that of Sema3A without reducing cell survival. We further seeded iPSC-MSCs modified by SemaA-HIF1 alpha overexpression onto hydroxyapatite (HA) scaffolds, and evaluated their growth and differentiation on this three-dimensional material. Additional data indicated that, as compared to iPSC-MSCs cultured in ordinary two-dimensional dishes, cells cultured in HA scaffolds grew (blank vs. HA scaffolds: 0.83 vs. 1.39 for survival) and differentiated better (blank vs. HA scaffolds: 11.29 vs. 16.62 for alkaline phosphatase activity). Conclusion: Modifying iPSC-MSCs with pro-osteogenic (Sema3A) and pro-survival (HIF1 alpha) factors may represent a promising strategy to optimize tissue engineering-based strategy in bone repair.