In the absence of effective endogenous repair mechanisms after ischemic injury, cell-based therapies have emerged as a potential novel therapeutic approach in ischemic tissue repair. After the initial characterization of putative bone marrow-derived endothelial progenitor cells (EPC) and their potential to promote cardiac and critical limb ischemia neovascularization and to attenuate ischemic injury, more than a decade of intense preclinical research, led to the BM progenitors/EPC-based clinical trials. However, despite early enthusiasm, cell based therapies yielded modest clinical results. Modest clinical outcomes of cell-based therapies may reflect the cellular dysfunction that is known to ensue in EPC/progenitor cells obtained from diabetic animals as well as patients. Compelling evidence indicates that EPCs dysfunction represents a mechanism for impaired vascular repair and angiogenesis in diabetes, subsequently leading to vascular dysfunction. Therefore, understanding the molecular basis of diabetes-induced EPC dysfunction and potentially reversing EPC dysfunction may represent a strategy to enhance cell-based therapeutics for myocardial/ischemic limb repair in diabetic patients. Increasing evidence also indicates that the mechanism underlying hyperglycemic memory and EPC dysfunction may involve epigenetic mechanisms involving enhanced epigenetic repressive marks on vascular genes leading to their epigenetic silencing. Moreover, since hyperglycemic memory is inherited through cell division, and altered epigenetic patterns in diabetic EPCs can be transmitted to daughter cells. Understanding the epigenetic basis of EPC dysfunction in diabetics and epigenetic reprogramming of diabetic EPCs, is therefore, of paramount importance for cell based therapies in diabetic patients. Therefore, our central hypothesis is that epigenetic repressive marks in diabetic EPCs render them dysfunctional and epigenetic modifying agents targeting those repressive marks can reprogram diabetic EPCs to a more functional and reparative phenotype. This project aims to study, in detail, phenotypic, epigenetic and molecular characterization of reprogrammed diabetic EPCs from diabetic mice as well as human CD34+ hematopoietic stem cells from diabetic patients and their exosome derivatives and test the ischemic myocardial repair capacity of these reprogrammed diabetic EPCs in physiologically relevant model of MI and hind limb ischemia. This overall aim will be achieved by conducting experiments organized under the following three specific aims: 1) To evaluate phenotypic stability and reparative potential of epigenetically reprogrammed diabetic EPCs; 2) To determine the specific epigenetic modifications in reprogrammed EPCs and establish a role of HDAC1 and G9a methytransferase in reprogramming process and 3) To establish epigenetic reprogramming rescues functional and reparative deficits in human CD34+ stem cells from patients with Type 2 diabetes.
Heart disease is a leading cause of morbidity and mortality amongst Americans and patients with diabetes poses an additional risk for heart disease and failure. Adult stem cells from patients own bone marrow are currently used in the clinical trials to enhance the repair and regeneration of the diseased heart and have shown limited improvement in patients with ischemic heart disease in part due poor functional properties and survival of stem cells obtained from diabetic patients. Studies proposed in this application provide a novel approach of using small molecules drugs that can reprogram functional deficiencies in stem cells from diabetic animals and patients and findings from this research may significantly improve upon existing regenerative cell therapy programs.
