Botulinum toxin type a intralesional monotherapy for treating human hypertrophic scar in a dose-dependent manner: In an animal model.

Background: The effect of Botulinum toxin type A (BTX-A) in treating or preventing a hypertrophic scar (HS) had been reported in clinical studies. However, the dose-effect relationship remains unclear.

Objective: To study the dose-effect relationship of BTX-A intralesional monotherapy treating human HS.

Methods: Six HS tissues were collected from six patients. Each tissue was segmented into 24 specimens and split into four groups: negative control (group A), 0.5U BTX-A (group B), 1U BTX-A (group C), and 2U BTX-A (group D). Six nude mice, each was prepared by implanting four specimens (one from each group) into the back for a total of 24 specimens. The process mentioned above were repeated six times. A re-entry operation was performed to obtain the specimens after 8 weeks. The weight of HS, the expression of decorin and TGF-β, the proliferation, and migration ability of hypertrophic scar fibroblasts (HSFBs) were compared among groups.

Results: The weight of HS, the expression of decorin and TGF-β, the proliferation, and migration ability of HSFBs showed significant differences in groups C and D as compared to group A; there has been no statistical significance in group B.

Conclusion: BTX-A showed significant therapeutic efficacy when compared with the negative control group in a dose-dependent manner. BTX-A can reduce the weight of HS, upregulate the expression of decorin, downregulate the expression of TGF-β, and inhibit HSFBs proliferation and migration ability. This study indicates that BTX-A intralesional monotherapy treating HS should reach a threshold dose to achieve an effective treatment, and a high dose of BTX-A is more effective than a low dose.