Increased expression of Sonic hedgehog restores diabetic endothelial progenitor cells and improves cardiac repair after acute myocardial infarction in diabetic mice

Damaged endothelial progenitor cells (EPCs) are associated with poor prognosis in diabetic myocardial infarction (DMI). Our previous studies revealed that an impaired Sonic hedgehog (Shh) pathway contributes to insufficient function in diabetic EPCs; however, the roles of the Shh pathway in diabetic EPC apoptosis under basal and hypoxic/ischemic conditions remain unknown. Therefore, the present study investigated whether Shh revitalized diabetic EPCs and consequently improved the deteriorative status of DMI. For this purpose, streptozotocin injection was used in male C57/BL6 mice to induce type-1 diabetes, and diabetic EPCs were isolated from the bone marrow. Apoptosis, cell function, and protein expression were investigated in EPCs in vitro. Mouse hearts were injected with adenovirus Shh-modified diabetic EPCs (DM-EPC(Shh)) or control DM-EPC(Null) immediately after coronary artery ligation in vivo. Cardiac function, capillary numbers, fibrosis, and cell apoptosis were then detected. First, the in vitro results demonstrated that the apoptosis of diabetic EPCs was reduced following treatment with Shh protein for 24 h, under normal or hypoxic conditions. BMI1 proto-oncogene (Bmi1), an antiapoptotic protein found in several cells, was reduced in diabetic EPCs under normal or hypoxic conditions, but was upregulated after Shh protein stimulation. When Bmi1-siRNA was administered, the antiapoptotic effect of Shh protein was significantly reversed. In addition, p53, a Bmi1-targeted gene, was demonstrated to mediate the antiapoptotic effect of the Shh/Bmi1 pathway in diabetic EPCs. The Shh/Bmi1/p53 axis also enhanced the diabetic EPC function. In vivo, Shh-modified diabetic EPCs exhibited increased EPC retention and decreased apoptosis at 3 days post-DMI. At 14 days post-DMI, these cells presented enhanced capillary density, reduced myocardial fibrosis and improved cardiac function. In conclusion, the present results demonstrated that the Shh pathway restored diabetic EPCs through the Shh/Bmi1/p53 axis, suppressed myocardial apoptosis and improved myocardial angiogenesis, thus reducing cardiac fibrosis and finally restoring myocardial repair and cardiac function in DMI. Thus, the Shh pathway may serve as a potential target for autologous cell therapy in diabetic myocardial ischemia.