Stromal cell-derived factor 1 (SDF-1)-chemokine receptors CXCR4/7 axis plays a vital role in diabetic limb ischemia. Our previous studies demonstrated that elevated CXCR7 improves therapeutic efficacy of endothelial progenitor cells (EPCs) in diabetic limb ischemia. The effects of a specific CXCR7 agonist TC14012 on diabetic hind limb ischemia remains untested. We hypothesize that CXCR7 expression is reduced in diabetic EPCs and TC14012 improve angiogenic function of EPCs in diabetic limb ischemia. Early WT-EPCs were transfected with siRNA against CXCR7, and early db/db-EPCs were infected with CXCR7 lentivirus. Tube formation and capillary density of ischemic gastrocnemius muscle (GS) and soleus muscle (SS) at 4 weeks post-ischemic surgery were adopt for indication of angiogenesis. Diabetic hind limb ischemia (HLI) models were established by femoral artery ligation, followed by administration of TC14012 subcutaneously. Total and cell surface expression of CXCR7 were significantly decreased in EPCs from db/db mice compared with those from WT mice, whereas no significant differences of CXCR4 expression were observed. Tube formation by EPCs from db/db mice was also impaired compared with WT-EPCs. siRNA knockdown of CXCR7 was accompanied by impaired tube formation. Conversely, increasing CXCR7 levels in db/db EPCs completely reversed impaired tube formation function. High glucose (HG) dose dependently decreased the expression of CXCR7 in vitro but not that of CXCR4. HG also impaired tube formation of EPC from WT mice. Tube formation function of HUVEC was impaired after treated with HG (25mM) for 24 hours, which could be prevented by TC14012. Most importantly, TC14012 significantly improved blood flow restoration of ischemic hind limb starting from 2 weeks after ligation and promoted angiogenesis of ischemic GS and SS. Diabetes attenuates CXCR7 expression and impairs angiogenesis of EPCs. TC14012 improves blood reperfusion of diabetic hind limb ischemia.
K. Wang: None. X. Dai: None. J. Chen: None. P.N. Epstein: None. L. Cai: None. K.A. Wintergerst: None. Y. Qian: None. Y. Tan: None.