B7-33 Modulates Fibrotic Signalling in Hypertrophic Scar Fibroblasts: An In Vitro Study Supporting a Novel Therapeutic Strategy

B7-33 is a synthetic single-chain peptide analogue of relaxin (RLX), the latter known for its powerful organ-protective effects however its use is limited by the complex and costly synthesis. B7-33 reproduces the beneficial effects of RLX without triggering pathways often associated with tumorigenesis. Although explored in several therapeutic areas, its potential in hypertrophic scar (HTS) management had not been investigated. This study evaluated, for the first time, the biocompatibility and antifibrotic efficacy of B7-33 on human hypertrophic scar fibroblasts (HSF) and proposed an electrospun peptide-based dressing as a topical strategy for HTS management. Both normal (NHDF) and HSF maintained > 70% viability after 72h exposure to B7-33 (0.03–0.3 μg/mL). Treatment with 298.7 ng/mL B7-33 significantly modulated profibrotic gene expression within 3 days, showing greater Collagen Type I α-1 Chain (COL1A1) downregulation than reference antifibrotic agents. Poly(L-lactide-co-ε-caprolactone) (PLA-PCL, 70:30) solutions above the entanglement concentration (>7.21% w/v ) were electrospun to obtain B7-33-loaded dressings (1.5% w/w ). The resulting fibres (7.06 ± 1.53 μm) enabled controlled release over 72h (96 ± 3.1%). The peptide retained antifibrotic activity after incorporation, as confirmed by qRT-PCR up to 72h. The B7-33 dressing reduced wound closure in HSF, consistent with α-Smooth Muscle Actin (α-SMA) downregulation, without affecting NHDF behaviour. B7-33 dressing exhibited biocompatibility (89.13 ± 6.56%) and hydrophobic behaviour, both in ultrapure water (108.59 ± 2.16°) and simulated wound fluid (111 ± 1.3°), supporting its suitability for exudate management. These findings support B7-33 as an antifibrotic peptide and the feasibility of electrospun dressings for topical HTS management. • Hypertrophic scars arise from persistent TGF-β/Smad pathway activation • B7-33, a Relaxin analogue, shows antifibrotic properties • B7-33 is biocompatible with normal and hypertrophic human fibroblasts (HSF) • B7-33 modulates pro-fibrotic gene expression and cells proliferation in HSF • Advanced Electrospun Dressing enables controlled B7-33 release for scar management