Patients with diabetes mellitus have a higher incidence of cardiovascular complications, such as myocardial infarction and stroke. Diabetic patient's most common cause of death is coronary artery disease, which is a complication of atherosclerosis. However, it is not well understood why atherosclerosis is highly prevalent in diabetic patients. In diabetic mice, we found significantly higher levels of myeloid cells and myeloid cell progenitors in the bone marrow. In a recent study, we described that hematopoietic stem and progenitor cell activation after myocardial infarction increases production of myeloid cells, leading to accelerated atherosclerosis. Based on these observations, we hypothesize that diabetes induces myeloid-biased hematopoietic stem cells (HSCs), increases myelopoiesis, and finally results in exacerbated atherosclerosis due to higher supply of monocytes to plaque. We will test this hypothesis in 3 specific aims: 1.We will investigate if diabetes induces myelopoiesis, particularly monocytopoiesis in hematopoietic organs like the spleen and bone marrow. We will also investigate if diabetes makes monocytes more aggressive. We will use streptozotocin to induce diabetes in C57BL/6 mice (model for type 1 diabetes). Mice homozygous for the obese spontaneous leptin mutation (Lepob/ob; commonly referred to as ob/ob mice) will be used as a model for type 2 diabetes. 2.We will investigate if diabetes biases differentiation of HSCs towards myeloid lineages. We will enumerate HSCs in the bone marrow and spleen, and investigate if HSCs isolated from diabetic mice have a propensity to readily differentiate into myeloid progenitors. To test the mechanism of preferential HSC differentiation towards myeloid lineages, we will investigate the role of interleukin-3 receptor (IL-3R) signaling. 3. We will knock down the receptor for macrophage colony stimulating factor (MCSF-R), responsible for maintenance and differentiation of monocyte progenitors, with an siRNA. We will investigate if MCSF-R knockdown reduces diabetes-induced myelopoiesis, resulting in amelioration of atherosclerosis. The long-term goal of the study is to identify changes at stem and progenitor cell levels in diabetes and develop therapeutic approaches to reduce cardiovascular complications in diabetic patients. To facilitate my transition from a mentored postdoctoral fellowship to a stable independent research position, the K99 phase will be conducted as integrated mentored career development and research activities, and the R00 phase will be devoted to execution of the proposed research, establishing collaborations, and writing an R01 grant.
Patients with diabetes have increased incidence of cardiovascular diseases. However, the cause of the increased cardiovascular risk in diabetes is poorly understood. In fact, no effort has been made to treat the complication of diabetes at the stem and progenitor cell level. Understanding changes in hematopoietic stem cells in diabetes will significantly improve our knowledge on drug development to treat diabetic patients.
