Abstract P3033: Thrombospondin-1 Promotes Vascular Smooth Muscle Cell De-differentiation In Diabetes

Abstract

Diabetes is a major risk factor for atherosclerosis. Diabetic patients are prone to increased vascular smooth muscle cell (VSMC) migration and proliferation, hallmarks of VSMC de-differentiation, critical for the evolution of atherosclerosis. Multiple studies, including our earlier work, support the role of thrombospondin-1 (TSP1), a proatherogenic matricellular protein, as a putative link between diabetes and vascular disease. However, molecular mechanism(s) by which TSP1 promotes diabetic vasculopathy are incompletely understood. The goal of this work was to explore whether smooth muscle TSP1 (smTSP1) regulates VSMC phenotypic switch in diabetes. We generated conditional SMC-specific TSP1 knockout (smTSP1 KO ) mice by crossing female TSP1 fl/fl mice with tamoxifen (tmx)-inducible Myh11-CreER T2 male mice. For Cre recombination, 5-wks-old male TSP1 fl/fl Cre tg and age-matched TSP1 +/+ Cre tg littermate mice were treated with 60 mg/Kg/day tmx i.p. once daily for 5 consecutive days. To induce type 2 diabetes, mice cohorts were placed on western diet at 7-wks-age followed by streptozotocin (50 mg/Kg/day, i.p. x 5 days) at 16-wks-age. Mice were harvested at 20-wks-age for plasma and tissue collection. Immunoblotting of aortic lysates revealed significant decrease in TSP1 expression in tmx-treated TSP1 fl/fl Cre tg , validating smTSP1 KO mice. Lack of smTSP1 increased ACTA2 (SM contractile marker) expression by 2-fold accompanied with 50% reduction in CDK4 (cell cycle regulator) expression in diabetic smTSP1 KO vs. smTSP1 WT aortic vessels. Consistently, in murine aortic SMC (MASMC) primary cultures derived from smTSP1 KO mice, loss of smTSP1 augmented (>65%) LMOD1 (SM contractile marker) and SRF (transcriptional activator of SM contractile genes) expression coupled with diminished (45%) vimentin (SM synthetic marker) expression in 25mM glucose-treated smTSP1 KO vs. smTSP1 WT cells. Further, propidium iodide staining via flow cytometry revealed reduced S-phase cell counts concomitant to increased G 0 -G 1 cell distribution in glucose-treated smTSP1 KO vs. smTSP1 WT MASMC. Together, our data demonstrates a direct role of TSP1 in VSMC phenotypic transition and opens novel avenues for cell-specific TSP1-based therapies for treatment of diabetes.