Assessment of the efficacy of potassium titanyl phosphate laser, intralesional vitamin D, and intralesional dupilumab in a rabbit ear hypertrophic scar model

Objective: Hypertrophic scar (HS) formation is a condition that arises from the dysregulation of complex biological mechanisms involved in wound healing, leading to both aesthetic and functional complications. Current treatment methods are often insufficient or associated with significant side effects. This study aims to evaluate the histopathological and molecular effects of intralesional dupilumab, vitamin D3, and KTP laser—agents whose efficacy has not been previously demonstrated in controlled experimental animal models—in comparison with the classical treatment agent, triamcinolone acetonide (TA), for the management of HS. Materials and Methods: In this study, the well-established rabbit ear model was employed to simulate hypertrophic scar formation, and the model was successfully created using safe and modern surgical techniques. Animals were randomly assigned to six groups: sham, control, intralesional triamcinolone acetonide (TA), intralesional dupilumab, intralesional vitamin D3, and KTP laser. Treatments were administered at standard doses, directly targeting the scar tissue. After a four-week follow-up, tissue samples were collected for detailed analysis. Histopathological evaluation included Scar Elevation Index (SEI), fibrosis grade, collagen density, and capillary count. At the molecular level, a comprehensive panel of biomarkers representing various aspects of scar biology—TGF-β, PDGF, VEGF, EGF, FGF, CTGF, IL-17, MMP-2, MMP-9, collagen types I and III, fibronectin, and vimentin—were assessed via gene expression analysis. This study distinguishes itself from previous literature by its modeling technique and extensive evaluation parameters. Results: All histological and molecular parameters in the sham group remained within physiological limits, reflecting normal tissue structure. In the control group, consistent with hypertrophic scarring, significant increases were observed in SEI, fibrosis, collagen density, and capillary count, with marked elevations in inflammatory and proliferative biomarkers, and decreased levels of MMP-2 and MMP-9 (p<0.001). The TA and dupilumab groups demonstrated significant improvements at both histological and molecular levels. Dupilumab showed comparable efficacy to TA, inducing significant reductions in TGF-β, PDGF, VEGF, EGF, FGF, CTGF, fibronectin, vimentin, and collagen types I and III (p<0.001). Additionally, a significant positive correlation was found between VEGF levels and capillary count in the dupilumab group, indicating that molecular suppression was reflected histologically. The vitamin D group showed significant decreases in inflammatory and remodeling-associated markers such as TGF-β, IL-17, EGF, PDGF, FGF, vimentin, and collagen type III (p<0.001), and demonstrated the most pronounced increase in MMP-2 levels (p<0.001), contributing to ECM balance. The KTP laser group supported vascular regression, resulting in significant decreases in SEI and capillary count (p<0.05), and induced significant changes in VEGF, FGF, IL-17, fibronectin, MMP-2, and collagen type I (p<0.001). Dupilumab was found to be as effective as TA in all parameters except for MMPs and IL-17 (p<0.001). The study demonstrated that each treatment modality exerted significant effects on scar tissue through distinct biological mechanisms. Conclusion: This controlled experimental animal model demonstrated the potential efficacy of intralesional dupilumab, vitamin D3, and KTP laser in the treatment of hypertrophic scars. Dupilumab was found to be as effective as TA and may serve as a promising alternative therapeutic agent. Vitamin D3 emerged as a safe and cost-effective option, while KTP laser showed significant impact on vascular regression and ECM remodeling. This study provides a novel contribution to the literature by demonstrating the utility of these agents—whose efficacy had not been previously explored in controlled animal models—for the treatment of HS. Keywords: Hypertrophic scar, wound healing, scar remodeling, intralesional therapy, dupilumab, vitamin D3, KTP laser, triamcinolone acetonide, fibrosis, molecular biomarkers, TGF-β, PDGF, VEGF, EGF, FGF, CTGF, IL-17, MMP-2, MMP-9, collagen type I, collagen type III, collagen a1, collagen a3, fibronectin, vimentin, ECM (extracellular matrix), SEI (Scar Elevation Index), histopathological evaluation, capillary density, rabbit ear model, experimental animal study, angiogenesis, anti-inflammatory therapy, collagen synthesis, fibroblast activity, proliferative phase, remodeling phase, non-steroidal treatment alternatives, biological agents, laser therapy, keloid, scar modulation.