Anti-vitronectin single-chain variable fragment targeting the hemopexin-like domain decreases age-related macular degeneration indicators in ex vivo models of the retinal pigment epithelium

Vitronectin is a prominent constituent of the extracelluar matrix (ECM) that plays a key role in inflammation by regulating cell adhesion, migration, and complement activation. Together with other inflammatory biomarkers, lipids, and hydroxyapatite, an ECM component, vitronectin, accumulates in abnormal deposits and drusen associated with age-related macular degeneration (AMD). Using an engineered polypeptide (VnHX) containing the hexmopexin-like domain (HX) of vitronectin, we found that the HX domain directly promotes hydroxyapatite (HAP) accumulation. Next, we screened humanized single-chain variable fragments (scFvs) against vitronectin that inhibit the interaction between VnHX and HAP, leveraging the binding of VnHX to HAP. We then tested these scFvs for their ability to block Vn-containg deposits secreted by stem cell-derived retinal pigment epithelium (RPE). In this in vitro drusen model, treatment with the anti-vitronectin antibodies decreased vitronectin accumulation. Furthermore, the antibody treatment led to decreased accumulation of C5b-9 and clusterin, indicating alterations in the complement pathway and cellular stress. These results support that vitronectin has a functional role drusen accumulation and possibly in AMD progression. Vitronectin would be a novel, promising therapeutic target for AMD.