Date of Award
Ph.D. in Pharmaceutical Sciences
Pharmaceutics and Drug Delivery
James A. Stewart, Jr.
Chronic hyperglycemia is one of the main characteristics of type 2 diabetes mellitus (T2DM). With the increased prevalence of T2DM, the risk of cardiovascular complications, including heart attack or stroke, is increased. Complications linked to the vasculature are increased vascular calcification (VC) or mineral deposition within the medial layer of conducting arteries. Under calcification conditions, vascular smooth muscle cells (VSMCs) undergo an osteogenic switch to an osteoblast-like cell and begin producing bone proteins. Chronic hyperglycemia can also result in increased extracellular matrix (ECM) synthesis, accumulation, and crosslinking. One of the cell types responsible for increased ECM synthesis are ‘activated’ fibroblasts or myofibroblasts, which can alter the dynamic plasticity of the ECM. Like VSMCs, adventitial fibroblasts (AFBs) change their phenotype and function to become involved in the osteogenic response. Studies have proposed the release of chemokines or signaling proteins, like transforming growth factor-? (TGF-?), osteopontin (OPN), and osteocalcin (OCN), from VSMCs and AFBs will promote ECM calcification; however, the exact mechanisms are unclear. The advanced glycation end-products (AGE)/receptor for AGE (RAGE) signaling cascade has been implicated as a potentiator of VC in T2DM; however, its role is unknown. Therefore, we hypothesized that T2DM promoted vascular calcification in a RAGE-mediated mechanism, and changes in RAGE signaling synergistically altered VSMC-AFB responses and interactions to differentially promote vascular calcification. The first study determined the impact of VC and T2DM on VSMCs and AFBs AGE/RAGE-mediated signaling mechanisms. In vitro studies were performed using calcified VSMCs or AFBs from diabetic, non-diabetic, diabetic RAGE knockout (RKO), and non-diabetic RKO male mice to determine if AGE-mediated RAGE signaling was responsible for driving the response to calcification in both VSMCs and AFBs in our in vitro cell culture model. The second study evaluated the impact of AGE/RAGE-mediated paracrine signaling between VSMC-AFB in response to calcification and T2DM. In vitro studies with all genotypes were used to determine if calcified cells released chemokine signal(s) because of calcification and/or AGE treatment to elicit an osteogenic response in the opposing cell type. The third study described the response of elevated AGE/RAGE signaling in an explanted aorta model in which calcification conditions could be controlled to model the in vivo microenvironment. Whole aortas with and without the adventitial layer from all genotypes were examined to determine if the presence of the adventitial layer impacted molecular changes because of vascular calcification and a hyperglycemic microenvironment. Completion of this project defined a functional link between the AGE/RAGE signaling cascade and diabetes-mediated vascular calcification and establish a role for VSMC-AFB interactions in response to a calcifying and hyperglycemic environment.
Kennon, Amber Michelle, "Influence of RAGE Signaling on Cellular Communication in Diabetes-Mediated Vascular Calcification" (2021). Electronic Theses and Dissertations. 2019.