Metabolic syndrome (MetS) is a constellation of metabolic disorders that increase the incidence of
cardiovascular diseases. Risks of macrovascular complications are significantly enhanced in individuals with
MetS. However, the molecular basis for accelerated atherosclerosis in MetS remains poorly understood.
Hyperglycemia and hyperleptinemia, co-existing features of MetS, are independent risk factors for
development of atherosclerotic vascular disorders. Thrombospondin-1 (TSP-1) is a matricellular protein with
increased expression in diabetes, obesity and MetS. Multiple clinical studies, including animal data, highlight a
role of TSP-1 in vascular pathology. Our data suggest that a TSP-1-dependent mechanism, specific to MetS
where hyperglycemia and hyperleptinemia co-exist, mediates accelerated vasculopathy in MetS. However, the
precise mechanism by which TSP-1 drives vascular disease in MetS is unclear. Relevant to this application
are observations that in a murine model of combined MetS and atherosclerosis, TSP-1 expression correlates
with atherosclerotic lesion formation and increased smooth muscle cell (SMC) de-differentiation to a synthetic
proliferative phenotype. Accordingly, the overarching goal of this proposal is to delineate the regulatory
mechanism of TSP-1 on SMC phenotypic plasticity and lesion pathogenesis in MetS. We hypothesize that
TSP-1 induces VSMC de-differentiation to an atherogenic phenotype via activation of specific transcriptional
pathways in MetS. We further postulate that targeted TSP-1 deletion will blunt these pathways blocking
atherosclerotic complications in MetS. The specific aims are: 1) We will determine the molecular mechanism
by which TSP-1 regulates VSMC phenotypic switching in metabolic syndrome, 2) We will interrogate whether
TSP-1 regulates lesion pathogenesis in metabolic syndrome. This will be tested via loss of function
approaches using mouse models of MetS and combined MetS with atherosclerosis, with genetic TSP-1
deletion, as well as aortic SMC primary cultures in vitro derived from MetS mice. In addition, we will perform
SMC lineage tracing studies in vivo using the atherosclerotic mouse model of MetS with TSP-1 deletion,
expressing Cre-inducible SMC-specific reporter gene (ROSA26-eYFP), with SMCs genetically labeled with
yellow fluorescent protein (YFP). We will utilize different biochemical, histological and molecular biology
approaches in combination with High-frequency Ultrasound Imaging, en-face atherosclerotic lesion assay, HDL
function studies as well as metabolic phenotyping using EchoMRI and CLAMS. Overall, this proposal will
advance our fundamental understanding of the molecular basis of atherosclerotic vascular disease in MetS
and open novel avenues for development of TSP-1-targeted therapies for the treatment of MetS-induced
vasculopathy. Of relevance to R15 AREA grants, this project will provide an excellent platform to advance
undergraduate and graduate student research, strengthening the research setting of our institute.