Phosphatidylserine-Rich circulating extracellular vesicles activate TAM receptor signaling to promote skin wound repair

Phosphatidylserine (PS) is an anionic phospholipid that acquires signaling activity when exposed on membrane surfaces. Although small extracellular vesicles (sEVs) have been implicated in diverse biological processes, the contribution of membrane-associated PS to vesicle-mediated signaling remains incompletely understood. Here, we show that circulating small extracellular vesicles (csEVs) activate dermal fibroblasts and keratinocytes through a PS-dependent receptor signaling mechanism. Pharmacological blockade of PS using annexin V markedly attenuated csEV-induced cellular proliferation, migration, and paracrine factor expression. Mechanistically, PS-rich csEV membranes activated TAM family receptors and inhibition of TAM receptors suppressed csEV-induced cellular responses. To determine whether PS-mediated membrane signaling is sufficient to account for csEV bioactivity, we generated phosphatidylserine liposomes (PSLs) as a reductionist membrane mimetic. PSLs reproduced key csEV-induced responses in fibroblasts and keratinocytes in vitro and recapitulated csEV activity in ex vivo porcine skin explants and in vivo mouse wound models. Collectively, our data identify membrane-exposed phosphatidylserine as a key determinant of csEV bioactivity and define a PS-TAM receptor signaling axis that regulates skin cell activation.