Application of IFN-γ-Licensed urine-derived stem cells in SIS hydrogel promotes scar-free wound healing by immunomodulation and microenvironment remodeling

Scar-free wound healing remains an unmet clinical imperative, as dysregulated immune microenvironment during tissue repair drives irreversible fibrosis. While existing treatments (corticosteroid injections, laser therapy, surgical excision) provide symptomatic relief, they fail to address the pathophysiological triad of fibrosis: persistent fibroblast activation, aberrant ECM deposition, and chronic inflammation. Mesenchymal stem cell (MSC) therapy has emerged as a promising strategy to concurrently target these pathological axes. Among MSC sources, urine-derived stem cells (USCs) stand out as a superior candidate, owing to their non-invasive accessibility, minimal ethical concerns, favorable safety profile, and robust proliferative capacity. In this study, we explored the therapeutic potential of IFN-γ-pretreated urine-derived stem cells (γ-USCs) encapsulated in small intestinal submucosa (SIS) hydrogel for scar-free skin wound healing. Our findings demonstrated that IFN-γ pretreatment potentiated the immunomodulatory properties of USCs, driving macrophage polarization toward an anti-inflammatory phenotype to normalize the wound microenvironment. In vitro, γ-USCs significantly suppressed the hyperactivity of keloid fibroblasts and attenuated TGF-β-induced fibrotic responses, as evidenced by reduced collagen deposition and downregulated fibrotic markers. In vivo, using a rabbit ear scar model, SIS hydrogel-encapsulated γ-USCs (γ-USCs@SIS) markedly alleviated scar formation, with histopathological analyses revealing improved tissue architecture, balanced collagen remodeling, and restored skin biological function. Collectively, the γ-USCs@SIS system synergizes the enhanced immunomodulatory capacity of IFN-γ-pretreated USCs with the supportive microenvironment provided by SIS hydrogel, offering an innovative and translatable strategy for scar-free wound healing. This approach holds significant potential to advance fibrosis treatment by addressing the root causes of pathological scarring. Schematic diagram of scarless wound repair using IFN-γ-Pretreated decellularized matrix hydrogel. The SIS hydrogel encapsulates IFN-γ-primed USCs to form the γ-USCs@SIS composite hydrogel, which is applied to the wound site. As the SIS hydrogel degrades gradually, it releases bioactive substances that interact with local cells to promote angiogenesis. Concurrently, the released γ-USCs exert dual functions: they secrete immunomodulatory factors that direct macrophages toward a pro-healing phenotype, thereby mitigating inflammation, and they modulate fibroblast activity to control excessive collagen deposition, thus reducing scar formation. Mechanistically, IFN-γ pre-treatment of USCs inhibits the IL-17 signaling pathway, diminishing the secretion of pro-inflammatory cytokines, and consequently optimizing the wound immune microenvironment to facilitate scarless healing. • Ethical & Non-Invasive Stem Cell Source. urine-derived stem cells (USCs) — non-invasive, low immunogenicity, and ethically compliant—overcoming limitations of traditional stem cell sources (e.g., BM-MSCs) for scalable therapeutic applications. • Innovative Stem Cell-Biomaterial Synergy The γ-USCs@SIS hydrogel combines IFN-γ-pretreated USCs with a small intestinal submucosa (SIS), creating a dual-functional system that promotes scarless wound healing by enhancing immunomodulation and ECM remodeling. • Dual-Action Immunomodulation via IFN-γ Priming IFN-γ pretreatment enhances USCs' intrinsic immunomodulatory capacity while simultaneously reprogramming macrophage polarization toward the pro-regenerative M2 phenotype. This dual mechanism, mediated through IL-17 pathway modulation, creates an optimal anti-inflammatory and pro-healing wound microenvironment. • Native ECM Scaffold for Tissue Regeneration The decellularized SIS hydrogel provides a natural 3D ECM scaffold that inherently maintains native bioactive components, supporting long-term USC viability and activity while facilitating organized collagen deposition (Type III > Type I) for scarless repair. • Clinically Relevant Scarless Repair In a rabbit ear scar model, the hydrogel significantly reduces scarring, accelerates skin appendage regeneration (hair follicles, glands), and balances inflammation-ECM remodeling, offering preclinical proof for translation.