Endothelial SHP-1 regulates diabetes-induced abnormal collateral vessel formation and endothelial cell senescence.

Background: Critical limb ischemia is a major cause of peripheral arterial disease and morbidity affecting patients with diabetes. Diabetes-induced premature senescence of endothelial cells (EC) has been proposed as a mechanism leading to impaired ischemia-driven angiogenesis. We showed that hyperglycemia induced expression of the protein tyrosine phosphatase SHP-1, which reduced angiogenic factor activity in ischemic muscle of diabetic mice. Here, we evaluate the impact of SHP-1 deletion on EC function and senescence.

Methods: Ligation of the femoral artery was performed in nondiabetic (NDM) and 3 months diabetic (DM) mice with EC-specific deletion of SHP-1. Cell migration, proliferation and protein expression were evaluated in EC exposed to normal (NG) or high glucose (HG) concentrations. Gastrocnemius and tibial artery of patients with diabetes were collected and analyzed.

Results: Blood flow reperfusion and limb function were reduced by 43 % and 82 %, respectively in DM mice as compared to NDM mice. EC-specific deletion of SHP-1 in DM mice restored blood flow reperfusion by 60 %, and limb function by 86 %, while capillary density was similar to NDM mice. Moreover, ablation of SHP-1 in EC prevented diabetes-induced expression of the senescence markers p53 and p21 and counteracted Nrf2 downregulation. In EC, elevated expression of beta-galactosidase, p21 and p53, and suppression of Nrf2 and VEGF actions were observed in EC exposed to HG levels and human muscle and artery of patients with diabetes, effects that were reversed by overexpression of dominant negative SHP-1.

Conclusion: SHP-1 in EC is a central effector of diabetes-induced senescence and induces aberrant collateral vessel formation and blood flow reperfusion. Reduced SHP-1 expression counteracts these pathologic features.