Exosomes secreted from mutant‐HIF‐1α‐modified bone‐marrow‐derived mesenchymal stem cells attenuate early steroid‐induced avascular necrosis of femoral head in rabbit

Mesenchymal stem cells (MSCs)-derived exosomes exhibit protective effects on damaged or diseased tissues. Hypoxia-inducible factor 1α (HIF-1α) plays a critical role in bone development. However, HIF-1α is easily biodegradable under normoxic conditions. The bone-marrow-derived mesenchymal stem cells (BMSCs) were transfected with adenovirus carrying triple point-mutations (amino acids 402, 564, and 803) in the HIF-1α coding sequence (CDS). The mutant HIF-1α can efficiently express functional proteins under normoxic conditions. To date, no study has reported the role of exosomes secreted by mutant HIF-1α modified BMSCs in the recovery of the early steroid-induced avascular necrosis of femoral head (SANFH). In this study, we firstly analyzed exosomes derived from BMSCs modified by mutant (BMSC-ExosMU) or wild-type HIF-1α (BMSC-ExosWT). In vitro, we investigated the osteogenic differentiation capacity of BMSCs modified by BMSC-ExosMU or BMSC-ExosWT, and the angiogenesis effects of BMSC-ExosMU and BMSC-ExosWT on human umbilical vein endothelial cells (HUVECs). Besides, the healing of the femoral head was also assessed in vivo. We found that the potential of osteogenic differentiation of BMSCs treated with BMSC-ExosMU was higher than the wild-type group in vitro. In addition, BMSC-ExosMU stimulated the proliferation, migration, and tube formation of HUVECs in a dose-dependent manner. Compared with the BMSC-ExosWT or PBS control group, the injection of BMSC-ExosMU into the necrosis region markedly accelerated the bone regeneration and angiogenesis, which were indicated by the increased trabecular reconstruction and microvascular density. Taken together, our data suggest that BMSC-ExosMU facilitates the repair of SANFH by enhancing osteogenesis and angiogenesis.