Diabetes mellitus associated dysfunction of endothelial progenitor cells (EPCs) may contribute to dysregulation of endothelial regeneration. Metallothionein (MT) acts as an antioxidant in various pathophysiological processes. Whether MT in EPCs has positive angiogenic effects and the mechanisms involved remain unclear. Endothelial MT overexpression (JTMT) mice were made diabetic by high fat diet followed by STZ administration (HFD/STZ). Diabetic hind limb ischemia model was established by femoral artery ligation. Bone marrow derived mononuclear leucocytes (MNCs) collected from JTMT mice were transplanted into db/db mice with hind limb ischemia. Blood reperfusion was monitored and oxidative stress was measured. High glucose and hypoxia conditions in culture were adopted to mimic diabetic ischemia in vitro. MT improved blood perfusion of ischemic hind limb and promoted angiogenesis in HFD/STZ diabetes. Oxidative stress of ischemic muscles was aggravated under diabetic condition, which was reduced in JTMT mice. Compared with WT mice, the expression of HIF-1α, SDF-1, VEGF and p-Akt were all increased in JTMT mice, along with elevation of plasma SDF-1α and VEGF. Moreover, transplantation of MT overexpressed MNCs showed better therapeutic effect on db/db diabetic mice with hind limb ischemia than control or transplantation of normal MNCs. Transplantation was accompanied by elevated HIF-1α, SDF-1 and Akt signaling. Vitro studies demonstrated that MT overexpression reduced high glucose and hypoxia induced EPC dysfunction and preserved high glucose and hypoxia impaired HIF-1α, SDF-1, VEGF and Akt signaling, all of which were abolished by siRNA knockdown of HIF-1α.
In conclusion, elevated MT enhances angiogenic function and therapeutic efficacy of EPCs in diabetic limb ischemia. The benefits of MT are predominantly mediated by a HIF-1α/SDF-1/Akt pathway under diabetic ischemia conditions.
K. Wang: None. X. Dai: None. J. He: None. C. Yang: None. J. Chen: None. K.A. Wintergerst: None. P.N. Epstein: None. L. Cai: None. Y. Tan: None.
American Diabetes Association (1-15-BS-018, 1-18-IBS-082 to L.C.); 1-13-JF-53 (to Y.T.)