Hypoxia pretreatment improves the therapeutic potential of bone marrow mesenchymal stem cells in hindlimb ischemia via upregulation of NRG-1

Mesenchymal stem cells (MSCs) are considered a promising treatment for ischemic diseases, but their use is limited due to poor survival after injection. Hypoxia can significantly enhance the survival of MSCs. This study aimed to investigate hypoxia pretreatment of bone marrow mesenchymal stem cells (BM-MSCs) in hindlimb ischemia (HI) and the underlying mechanism. The HI mouse model was established and human BM-MSCs were injected into ischemic skeletal muscles. The blood flow reperfusion and capillary density were measured. In vitro, human BM-MSC cells were treated with hypoxia. The expression of NRG-1 and associated angiogenic factors were measured after knockdown or overexpression of NRG-1. The conditioned medium (CdM) of BM-MSCs was prepared and co-cultured with human umbilical vein endothelial cells (HUVECs), and then, the proliferation, migration, and angiogenesis of HUVECs were detected. After hypoxia pretreatment, NRG-1 expression, clone formation, proliferation, and angiogenic factor secretion from BM-MSCs were increased, while knockdown of NRG-1 reversed these results. In normoxia condition, overexpression of NRG-1 enhanced above factors. Additionally, hypoxia pretreatment of BM-MSCs induced the proliferation and migration of HUVECs and angiogenesis. Moreover, the injection of hypoxia pretreatment of BM-MSCs improved blood reperfusion and capillary density in HI mice, while knockdown of NRG-1 reversed the effect. Furthermore, the PI3K inhibitor and activator reversed the effect of NRG-1 overexpression and knockdown on angiogenesis. We concludes that hypoxia pretreatment of BM-MSCs facilitates angiogenesis and alleviates HI injury via NRG-1/PI3K/AKT pathway.