Rational design of FAP-targeted sEVs delivered by microneedles for precision treatment of hypertrophic scars via ferroptosis in hypertrophic scar fibroblasts.

Hypertrophic scars (HS) lack cell-specific therapies because pathogenic hypertrophic scar fibroblasts (HSFs) are hard to inactivate without damaging human dermal fibroblasts (HDFs). Ferroptosis has emerged as a potential antifibrotic vulnerability of activated fibroblasts, yet its translational use is constrained by off-target toxicity of small-molecule inducers. Here, we report a targeted delivery strategy based on small extracellular vesicles (sEVs) surface-decorated with a fibroblast activation protein (FAP) ligand to preferentially deliver a widely used ferroptosis inducer erastin to HSFs. We confirmed that FAP is upregulated in HSFs and HS tissue, and engineered adipose-derived mesenchymal stem cell (ADSC)-derived sEVs loaded with erastin and covalently conjugated with the FAP ligand UAMC1110 (sEVsErF) via EDC/NHS chemistry. sEVsErF retained typical nanoscale characteristics and EV marker profiles and showed preferential uptake by HSFs over HDFs in vitro, which was validated by competitive blocking and FAP knockdown experiments. Functionally, sEVsErF suppressed HSF proliferation and migration and reduced α-SMA, COL I, and COL III expression, accompanied by ferroptosis-associated signatures including lipid peroxidation, glutathione depletion, labile Fe2+ accumulation, and mitochondrial dysfunction. For localized dermal delivery, sEVsErF were incorporated into dissolvable microneedle patches (DMNPs) with GelMA tips and a PVA backing. In a rabbit ear HS model, sEVsErF-DMNPs reduced scar thickness and collagen deposition and modulated ferroptosis- and fibrosis-related readouts in scar tissues. Both in vitro and in vivo rescue experiments using the ferroptosis inhibitor Ferrostatin-1 confirmed that these effects were specifically mediated by ferroptosis. Collectively, these results support FAP as an actionable targeting handle for preferential delivery to scar fibroblasts and suggest that ferroptosis-associated inactivation of HSFs can be leveraged through a microneedle-enabled, locally retained sEV formulation.