C-Kit is Essential for Vascular Smooth Muscle Cell Phenotypic Switch In Vitro And In Vivo After Injury

Pathological vascular remodeling—central to restenosis, atherosclerosis and vascu-lo-proliferative diseases—depends on phenotypic switching of vascular smooth muscle cells (VSMCs) from a quiescent, contractile state to a synthetic, proliferative program. Although the receptor tyrosine kinase c-KIT is implicated in proliferation, migration, and tissue repair, its role in VSMC plasticity has yet to be fully understood. Using c-Kit haploinsufficient mice subjected to right carotid artery ligation (CAL) and primary aortic VSMC cultures, we show that c-Kit is required for the contractile-to-synthetic transition. In vitro, c-Kit haploinsufficiency halved c-Kit expression, reduced BrdU incorporation, and blunted PDGF-BB–induced repression of contractile genes. c-Kit–deficient VSMCs ex-hibited a senescence program with increased p16INK4a/p21 expression and up-regulated senescence-associated secretory phenotype (SASP) mediators. RNA-seq of carotid arteries 7 days post-ligation revealed that wild-type arteries activated cell-cycle pathways and suppressed contractile signatures, whereas c-Kit–deficient carotid arteries failed to fully engage proliferative programs and instead maintained contractile gene expression. At 28 days post CAL in vivo, c-Kit haploinsufficiency produced markedly reduced neointima, fewer Ki67+ VSMCs, more p16INK4a+ cells, and impaired re-endothelialization. Because progenitor-to-VSMC differentiation contributes to remodeling, we tested adult cardiac stem/progenitor cells (CSCs) as a model system of adult progenitor differentiation. Wild-type CSCs efficiently generated induced VSMCs (iVSMCs) with appropriate smooth-muscle gene up-regulation; c-Kit–deficient rarely did so. Restoring c-Kit with a BAC transgene rescued both smooth-muscle differentiation and proliferative competence of c-Kit–deficient iVSMCs. Collectively, our data identify c-Kit as a gatekeeper of repar-ative VSMC plasticity. Adequate c-Kit enables progenitor-to-VSMC commitment and expansion of newly formed VSMCs while permitting injury-induced proliferation and matrix synthesis; reduced c-Kit locks cells in a hypercontractile, senescence-prone state and limits neointima formation. Modulating the c-Kit axis may therefore offer a strategy to fine-tune vascular repair while mitigating pathological remodeling. Overall design: We combine (i) primary mouse aortic VSMCs challenged with platelet-derived growth factor BB (PDGF-BB), (ii) a right carotid artery ligation model with RNA-seq at day 7 and morpho-functional analyses at day 28, and (iii) progenitor-to-VSMC differentiation assays with genetic rescue to test whether c-Kit dosage controls the contractile-to-synthetic switch and reparative proliferation. We identify c-Kit as a dosage-dependent regulator that constrains senescence and enables progenitor commitment and VSMC expansion fol-lowing injury.