# C-Kit Is Essential for Vascular Smooth Muscle Cell Phenotypic Switch In Vitro and In Vivo After Injury

## TL;DR

The study shows that c-Kit is crucial for vascular smooth muscle cells to switch their function during injury repair, impacting vascular remodeling and disease.

## Contribution

This study identifies c-Kit as a key regulator of vascular smooth muscle cell plasticity during injury repair, both in vitro and in vivo.

## Key findings

- c-Kit haploinsufficiency impairs the phenotypic switch of vascular smooth muscle cells to a synthetic state.
- Reduced c-Kit leads to increased senescence and impaired neointima formation after vascular injury.
- Restoring c-Kit rescues smooth muscle differentiation and proliferation in progenitor-derived cells.

## Abstract

Pathological vascular remodeling—central to restenosis, atherosclerosis, and vasculo-proliferative diseases—depends on the 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 5-bromo-2′-deoxyuridine (BrdU) incorporation, and blunted platelet-derived growth factor BB (PDGF-BB)-induced repression of contractile genes. c-Kit–deficient VSMCs exhibited a senescence program with increased p16INK4a/p21 expression and upregulated 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 upregulation; c-Kit–deficient rarely did so. Restoring c-Kit with a BAC transgene rescued both the smooth-muscle differentiation and proliferative competence of c-Kit-deficient iVSMCs. Collectively, our data identified c-Kit as a gatekeeper of reparative VSMC plasticity. Adequate c-Kit enables progenitor-to-VSMC commitment and the 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.