Disruption of the basement membrane underlies common pathogenesis of valvular heart diseases revealed by a pan-valvular single-cell atlas

Background Valvular heart diseases (VHDs) from diverse etiologies including degeneration, congenital malformation, infection, and rheumatic changes lack understood common mechanisms. The basement membrane (BM) role in shared VHD pathogenesis is unexplored. We constructed a pan-valvular single-cell atlas to investigate shared mechanisms across VHDs, focusing on BM integrity. Methods We performed scRNA-seq on 42 human samples including normal controls (aortic, mitral, tricuspid, pulmonary) and diseased valves (regurgitant, degenerative, bicuspid, infective endocarditis, rheumatic). Following quality control and data integration, we identified major cell populations and focused on valvular interstitial cells (VICs) to uncover disease-associated subtypes. Validation was performed using proteomics, bulk RNA-seq, and histological staining. PAX7 function was tested via in silico perturbation and in vivo aortic valve calcification model. Results Integrated analysis identified five major populations: VICs, VECs, mast cells, myeloid cells, lymphocytes. Within VICs, two consistent disease-wide alterations emerged: a myofibroblast-like VIC5 subset was universally upregulated, while a regulatory VIC3 subset was significantly depleted across all VHDs. Notably, we discovered a novel PAX7-expressing myofibroblast-like subpopulation within VIC3 (PAX7+ VIC3). In marked contrast to VIC5, PAX7+ VIC3 was uniformly decreased in all diseased valves and specifically responsible for maintaining BM integrity. Proteomic and bulk RNA-seq data corroborated VIC3-associated signature downregulation in disease. Histologically, diseased valves exhibited disrupted, disorganized BM and marked loss of PAX7+ VICs versus normal controls. In silico PAX7 knockout perturbed gene networks for BM synthesis, ECM organization, and mineralization. Critically, in vivo PAX7 overexpression preserved aortic valve BM integrity, attenuated calcification, and reduced both peak aortic valve velocity and transvalvular pressure gradient. Conclusion This pan-valvular atlas reveals that despite diverse etiologies, VHDs converge on a common cellular pathology: loss of protective PAX7+ VIC3 subpopulation leading to BM disruption as a fundamental pathogenic mechanism across valve types and disease etiologies. Preserving the PAX7+ VIC3-BM axis represents a novel and universal therapeutic target for halting VHD progression.