Sorbs2 is required for VSMC phenotype plasticity
Authors: McLendon Jared , Linzer Connor , Boudreau Ryan 
Published: May 2023

We have previously shown that cardiomyocyte specific Sorbs2 knockout mice develop dilated heart failure due to cytoskeletal remodeling and impaired myofiber contraction. However, the role of Sorbs2 in VSMC and its contributions to vascular physiology remains unknown. We noticed that Sorbs2 expression is ~1-3 fold more abundant in vascular (tibial, coronary, and aorta arteries) than cardiac tissues (GTEx), and that genetic variation in the Sorbs2 locus significantly associates with vascular diseases, including coronary artery disease (p=8e-10), atherosclerosis (1e-7), and hypertensive heart disease (p=4e-7), and associates with Sorbs2 expression in human arteries (p=6.2e-17). Sorbs2 expression is also significantly decreased in brain aneurysms, in models of hypertension and vascular occlusion, increased in humans and mice with atherosclerosis, and dysregulated in VSMC cultures after mechanical or biochemical stimuli. Promoter analysis shows that the Sorbs2 locus contains 22 conserved CArG boxes (SRF binding sites), and its expression is decreased in smooth muscle specific SRF-KO mice, suggesting SRF transcriptional regulation. Single cell sequencing data shows that Sorbs2 is one of the top 25 smooth muscle enriched genes from human coronary arteries, it is also expressed in several vascular cells, highlighting a need for conditional knockout mice to study Sorbs2 function in VSMC. We crossed Sorbs2ex12Flox mice with transgenic Myh11-CreGFP mice to create smooth muscle knockouts (smKO). Whereas the primary Sorbs2 proteins in heart tissues range 100-140 KD in size, we detect > 80% loss of Sorbs2 immunoreactive bands at 80 and 95 KD in smKO mouse aorta. Preliminary analysis from tail-cuff plethysmography suggests smKO mice may have increased arterial blood pressure driven by diastolic pressure (n=6, p~0.06), perhaps due to increased peripheral vascular resistance, stiffening or impaired relaxation. We next evaluated smooth muscle contractile gene expression in aorta SMC (AoSMC) and found that Sorbs2-smKO had significantly decreased expression of contractile genes Cnn1, Myh11, Acta2, Tagln, and Myocd, suggesting loss of contractile phenotype. Whereas expression of fibronectin is significantly increased in smKO samples, suggesting a need to bolster cell adhesion in the absence of Sorbs2. We next investigated the proliferative capacity of VSMC cultures and found that Sorbs2-smKO cells had significantly reduced growth, with and without PDGF-BB stimulation (20 μg/mL, n=5 wells/genotype/treatment and n=2 SMC cultures/genotype). Proliferation experiments were also performed using AoSMC cultures from Sorbs2F/F mice acutely transduced in vitro with adenovirus (Ad5-Cmv-Cre, MOI=50, U.Iowa Viral Core), and in A7R5 immortalized cells with Sorbs2 siRNA knockdown (Dharmacon, 25 nM), each yielding similar results. Altogether, these data suggest that Sorbs2 is a novel cardiovascular disease associated gene, abundantly expressed in VSMC, that regulates SMC phenotypes. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.