Fibrosis Without Macrocalcification: A Novel In Vitro Model to Study Aortic Valve Disease

Background The absence of medical treatment for fibro-calcific aortic valve stenosis (FCAVS), despite its high incidence in high-income countries, emphasizes the need to discover novel therapeutic targets. Given the sex-specific differences in fibrotic and calcific pathways in FCAVS, in vitro approaches capable of independently dissecting these two processes must be developed. This project aims to characterize a new medium able to induce fibrosis specifically in valvular interstitial cells (VICs). Methods Human VICs were isolated from 10 explanted tricuspid aortic valves (5 males and 5 females) and treated with fibrotic and fibrocalcific media for 0, 7 and 14 days. Results As expected, the fibrotic medium increased fibrotic markers (elevated procollagen I, procollagen III, and MMP-2 levels), while the fibrocalcific medium induced calcification (decreased total Ca 2+ levels in supernatants and increased calcific nodules detected by Alizarin Red staining) associated with mild fibrosis, in both males and females VICs (elevated procollagen I and procollagen III levels) without major sex-specific differences. Conclusions This novel fibrotic medium allows for the independent analysis of fibrotic pathways, distinct from calcification ones, in male and female-derived VICs. The minimal sex-specific differences within each milieu suggest that sex-specific differences in FCAVS may be driven more by the surrounding milieu than by intrinsic cellular sex. This medium may help improve our understanding of the pathophysiological processes underlying FCAVS.