Comparison of Steroid and Botulinum Toxin Type A Monotherapy with Combination Therapy for Human Hypertrophic Scars in an Animal Model

Background: Hypertrophic scars are a challenging complication of wound healing, characterized by excessive fibroblast proliferation, collagen deposition, and persistent inflammation. Current intralesional therapies, such as corticosteroids, show partial efficacy but are often associated with adverse effects. Botulinum toxin type A (BoNT-A) has emerged as a potential therapeutic option, and its combination with corticosteroids may provide a synergistic effect. This study aimed to evaluate and compare the histopathological effects of intralesional triamcinolone acetonide, botulinum toxin type A, and their combination in hypertophic scar in an animal model. Methods: A total of forty scar samples were randomly assigned into four groups: control with saline, triamcinolone acetonide, BoNT-A, and a combined regimen of both agents. Histopathological assessment was performed after four weeks, focusing on inflammatory activity, fibroblast proliferation, collagen deposition, necrosis, and tissue reconstruction. Results: The control group exhibited persistent fibroblast activity and dense collagen fibers, consistent with the natural progression of untreated hypertrophic scars. The triamcinolone group showed reduced fibroblast activity but was associated with acute inflammation, epidermal necrosis, and focal collagen deposition. The BoNT-A group demonstrated decreased vascularization, suppressed fibroblast activity, partially organized collagen fibers, and gradual tissue reconstruction. The combination therapy group yielded the most favorable outcomes, with near-complete dermo-epidermal reconstruction, orderly collagen deposition, minimal necrosis, and resolution of persistent inflammation. Conclusion: Both triamcinolone and BoNT-A demonstrated efficacy in reducing hypertrophic scar features; however, their combination produced superior histopathological outcomes, reflecting a synergistic therapeutic effect.