Crosstalk of smooth muscle cell-derived fibronectin and cGMP signaling is atheroprotective

Rupture of unstable atherosclerotic plaques can lead to heart attack and stroke. Smooth muscle cells (SMCs) generate extracellular matrix (ECM) that contributes to plaque stability. Phenotypic switching of SMCs during atherogenesis may influence ECM composition and stability of plaques. cGMP signaling modulates SMC growth and phenotype, but how the ECM affects this process in atherosclerotic lesions is not well understood. Fibronectin (Fn1) is an abundant component of the plaque ECM and has been linked to coronary artery disease (CAD) risk in humans. To study the role of SMC-derived Fn1 in SMC phenotypic switching, we generated conditional knockout mice lacking Fn1 in SMCs on an ApoE-deficient background (Fn-smko mice). As compared to control mice, Fn‑smko mice had larger lesions with less Acta2+ cells and reduced collagen content in the fibrous cap indicative of decreased plaque stability. A combination of scRNA-seq, SMC lineage tracing and immunostaining showed that Fn-smko lesions contained more modulated SMCs than control plaques. Interestingly, the shift in SMC phenotypes was associated with increased expression of the NO-sensitive guanylyl cyclase (NO-GC) in modulated plaque cells. Like Fn1, NO-GC has been linked to CAD risk in humans. Real-time analyses of primary aortic SMCs revealed increased growth of Fn-smko cells associated with high activity of the NO-cGMP pathway. Collectively, our findings provide strong evidence that SMC-derived Fn1 promotes an atheroprotective SMC phenotype associated with reduced NO-cGMP signaling. This study also reveals a link between two CAD risk genes, Fn1 and NO-GC.