Abstract 371: The Role Of Scleraxis In Inducing Vascular Stiffness

Abstract

Vascular dysfunction underlies numerous significant diseases including diabetes, atherosclerosis and hypertension. Vascular dysfunction can be a result of altered smooth muscle contraction/relaxation, and impaired endothelial cell function within the vessel wall. Vascular fibrosis involves an increase in the thickness of vessel wall. This contributes to either an increase in extracellular matrix (ECM) synthesis or induced vascular smooth muscle proliferation within the vessel wall, or both, causing stiffer vessels with impaired tone and reduced lumen diameter.Our lab identified the transcription factor scleraxis as a novel master regulator of fibrotic signaling in the myocardium, showing scleraxis is sufficient to induce fibroblast to myofibroblast phenotype conversion, a critical step in the development of fibrosis, and directly up-regulates ECM genes in cardiac fibroblasts. Angiotensin II (AngII) was reported to induce vascular fibrosis via activation of the transcription factor Smad3 in aortic vascular smooth muscle cells. Our lab has shown that Smad3 physically interacts with scleraxis, and critically requires scleraxis to drive TGFβ/Smad fibrotic signaling in cardiac fibroblasts.Our preliminary data has revealed that scleraxis is detectable in the arterial wall, and scleraxis expression is elevated in high pressure versus low pressure regions of vessels. Loss of scleraxis in the aortas of scleraxis knock-out mice reveals a discontinuation and disarrangement in the structure of vascular wall. We thus hypothesize that scleraxis is sufficient and necessary to induce vascular fibrosis.Pressure myography data reveals an increase in vascular stiffness and thickness of 3rd order mesenteric arteries of smooth muscle-specific scleraxis overexpression mice. Also, our data shows that vascular stiffness is significantly increased in AngII-induced scleraxis overexpression mice with a relative increase in telemetry blood pressure measurements and pulse wave velocity. Histological sections suggest a reduction of the translamellar ECM accumulations in AngII-induced scleraxis overexpression aortas. To summarize, scleraxis may contribute to vascular stiffness by inducing vascular smooth muscle proliferation.