Abstract 1300: MnSOD Deficiency and Oxidative Stress of Endothelial Progenitor Cells Contribute to Impaired Angiogenesis and Wound Healing in Type 2 Diabetes
Introduction: Circulating endothelial progenitor cells (EPCs) are both reduced and dysfunctional in diabetes, but the mechanisms are incompletely understood. Normal EPCs express intrinsically high MnSOD levels and are thus resistant to oxidative stress. We hypothesized that hyperglycemia-induced oxidative stress reduces EPCs and their angiogenesis function, resulting in refractory wound healing in type 2 diabetic mice.
Methods and Results: Adult male (C57BLKS/J, 10–14 weeks) type 2 diabetic db/db and their normal littermates db/+ mice (glucose 270.4±38.3 vs. 153.6±4.8 mg/dL, n=5, p<0.01) were used. Circulating EPC number measured by flow cytometry was significantly lower in db/db vs. db/+ mice (1.45±0.5 vs. 3.6±0.4% sca-1/flk-1 double-positive cells, n=4–5, p<0.05). MnSOD mRNA and protein expressions in EPCs were decreased by >50% (real-time RT-PCR, p<0.05) and >60% (Western Blot, p<0.01) in db/db vs. db/+ mice, respectively. The levels of superoxide anion (O27minus;) were markedly elevated in db/db vs. db/+ mice (50.89±1.77 vs. 31.05±3.86% DHE-positive cells, n=4, p<0.005). The angiogenesis capacity of EPCs from db/db type 2 diabetic mice, determined by Matrigel tube formation assay, was significantly decreased (tubes/high powered field, n=4, p<0.05 vs. db/+). The impaired angiogenesis in diabetic EPCs was significantly improved following adenoviral vector-mediated MnSOD gene transfer (transduced db/db EPCs vs. non-transduced db/db EPCs, n=4, p<0.05). In db/db mice, the course of excisional wound closure (6-mm punch biopsy, n=4–5, p<0.01 vs. db/+) was markedly delayed, paralleled with impaired wound angiogenesis (CD31+ capillary number, n=4, p<0.05 vs. db/+). Cell therapy of normal EPCs (106 cells, db/+ mice) onto the wounds of db/db diabetic mice augmented in vivo wound angiogenesis by 1.6 folds (n=4, p<0.05 vs. db/db group), paralleled with a marked acceleration of wound closure rate (n=4–5, p<0.01 vs. db/db group).
Conclusion: MnSOD deficiency in EPCs and oxidative stress contribute to impaired angiogenesis and wound healing in type 2 diabetic mice. Gene transfer of MnSOD augments diabetic EPC angiogenesis function, and cell therapy of normal EPCs accelerates wound angiogenesis and excisional wound healing in type 2 diabetic mice.