Abstract
BACKGROUND: Neointimal hyperplasia after vascular injury reflects excess smooth muscle cell (SMC) proliferation with impaired endothelial recovery. We tested the hypothesis that selective Janus kinase 3 (JAK3) inhibition with the FDA-approved drug Ritlecitinib limits neointima while accelerating reendothelialization. METHODS: We used mouse carotid wire injury and a human internal mammary artery (IMA) xenograft model to evaluate effects of genetic JAK3 loss in SMCs or oral Ritlecitinib in vascular remodeling. Mechanistic studies in SMCs assessed JNK/c-Jun signaling and its regulation of thrombospondin-1 (TSP-1) and vascular endothelial growth factor A (VEGF-A) using RNA-seq and CUT&RUN. Rescue experiments tested whether VEGF-A neutralization or exogenous TSP-1 reversed the antineointimal effects. Patient-derived IMA SMCs were analyzed for variabilities in drug responses. RESULTS: Genetic JAK3 loss in SMCs or oral Ritlecitinib reduced neointimal area and intima/media ratio and increased luminal CD31+ coverage in both models. In SMCs, Ritlecitinib suppressed JNK/c-Jun signaling, downregulated TSP-1, and restored VEGF-A, shifting the milieu toward endothelial regeneration. RNA-seq and CUT&RUN corroborated JNK/c-Jun- dependent control of TSP-1 and VEGFA. VEGF-A neutralization or exogenous TSP-1 abrogated the anti-neointimal phenotype. In patient-derived IMA SMCs, variable drug response was linked to the JAK3 Pro893Asn variant and a VEGFA promoter SNP. CONCLUSION: Selective JAK3 inhibition by Ritlecitinib simultaneously restrains SMC proliferation and promotes endothelial repair through modulating TSP-1 and VEGF-A activities. Ritlecitinib merits clinical evaluation as a precision therapy to prevent restenosis, with genetic stratification to identify responders.