Abstract 220: Epigenetic Reprogramming Rescues Diabetic Endothelial Progenitor Cell Dysfunctions and Enhances Their Reparative Activities in Ischemic Tissue Repair

Abstract

Type 2 Diabetes mellitus (DM) is the leading cause of death in the United States with concomitant complications from circulatory disorders including endothelial cell (EC)/endothelial progenitor cell (EPC) dysfunction in a variety of organs including heart. Although clinical trials of bone marrow progenitors/EPCs have shown some promise, however, diabetic dysfunction of EPC limits the functional benefits of stem/EPC-based cellular therapies. Emerging evidence suggests that epigenetic silencing of functional genes leads to dysfunctional EPCs in diabetes. In the present study, we show that epigenetic modulation of diabetic EPCs using small molecules epigenetic modifiers rescue diabetes-induced EPC dysfunction. EPCs from diabetic (db/db) mice were treated with valproic acid (VPA, histone deacetylase inhibitor) and 5’-azacytidine (5’-Aza; DNA methyltransferase, DNMT, inhibitor), and their function was determined both in vitro and in vivo. In contrast to untreated EPCs, treatment with VPA/5’-Aza, enhanced their angiogenic activities including tube formation, survival and proliferation. Expression of multiple pro-angiogenic genes including eNOS, and VEGF/VEGFR2 was upregulated in reprogrammed EPCs and chromatin immunoprecipitation experiments confirmed enhanced histone3-lysine9 acetylation (H3K9ac) of these gene promoters. Reprogrammed EPCs displayed reduced protein expression of DNMT3a and DNMT3b; whereas expression of histone H3K9ac and H3K14ac (gene activating epigenetic mark) was up-regulated. In db/db mouse hind limb ischemia model, transplantation of reprogrammed EPCs restored blood flow, enhanced capillary density and muscle architecture and resulted in significant limb salvage. In a myocardial ischemia model in db/db mice, transplantation of reprogrammed EPCs enhanced left ventricular functions, reduced infarct size and increased capillary density in the border zone. Taken together our data suggests that the reprogramming of db/db-derived EPCs might result in pattern shift of epigenetic modifications, leading to up-regulation of functional genes repressed by hyperglycemia and may rescue dysfunctional EC/EPC phenotype leading to improved functional repair capacity of diabetic stem cells/EPCs.