605-P: Endothelial-Specific Overexpression of Metallothionein Prevents Diabetes Mellitus–Induced Impairment in Ischemia Angiogenesis via Preservation of HIF-1a/SDF-1/VEGF Signaling in Endothelial Progenitor Cells

Diabetes-induced oxidative stress contributes to endothelial progenitor cells (EPCs) dysfunction and impairs endothelial regeneration. Thus, we tested whether increasing antioxidant protein metallothionein (MT) in EPCs promotes angiogenesis in a hind limb ischemia (HLI) model in endothelial-specific MT transgenic (JTMT) mice with high fat diet and streptozocin (HFD/STZ)-induced diabetes. Compared with littermate wild type (WT) diabetic mice, JTMT mice had improved blood flow recovery and angiogenesis after HLI. Similarly, transplantation of JTMT bone marrow-derived mononuclear cells (BM-MNCs) stimulated greater blood flow recovery in db/db mice with HLI than did WT BM-MNCs. The improved recovery was associated with augmented EPC function: mobilization and infiltration in JTMT mice; and, enhanced capillary EPC incorporation in db/db mice. Further, cultured JTMT-EPCs had enhanced cell survival, migration, and capillary tube formation in hypoxia/hyperglycemic conditions compared with WT-EPCs. Mechanistically, MT overexpression enhanced hypoxia-inducible factor 1α (HIF-1α), stromal cell-derived factor (SDF-1) and vascular endothelial growth factor (VEGF) expression, and reduced oxidative stress in ischemic tissues. MT’s pro-EPC effects were abrogated by siRNA knockdown of HIF-1α without affecting MT’s anti-oxidant action. These results indicate that endothelial-specific MT overexpression is sufficient to protect against diabetes-induced impairment of angiogenesis by promoting EPC functions though upregulation of HIF-1α/SDF-1/VEGF signaling and reducing oxidative stress.