Effect of botulinum toxin type a on a rat surgical wound model.

Objectives: The tension on a wound is one of the important factors that determine the degree of fibrosis and scar formation. We hypothesized that local botulinum toxin type A (Botox) induced paralysis of the musculature subjacent to a surgical wound with a skin defect would minimize the repetitive tensile forces on the surgical wound's edges, and this will result in a decreased fibroplastic response and fibrosis of the wound.

Methods: This is a prospective randomized experimental study. Two distinct surgical wounds were made to the dorsum of 15 adult rats, respectively. One of the 2 wounds was injected with Botox, and the other wound was used as a control, and this was done for all the rats' wounds. We evaluated the wound size, the degree of fibrosis and inflammation, the blood vessel proliferation, the thickness of the wound and the expression of transforming growth factor (TGF)-beta1 in the wounds.

Results: There were significant differences of wound size at the 3rd and 4th week between the Botox and control groups (P<0.05). The Botox group showed less infiltration of inflammatory cells than the control group at the 2nd week (P<0.05). The Botox group showed a smaller number of fibroblasts and less fibrosis than the control group at the 4th week (P<0.05). The Botox group showed much strong collagen density than the control group at the 8th week (P<0.05). For the immunohistochemical staining, there was a lower transforming growth factor (TGF)-beta1 expression in the Botox group than that of the control group at the 4th week (P<0.05).

Conclusion: The wounds of the Botox-treated group showed a larger wound size, less infiltration of inflammatory cells and less fibrosis, a much greater amount of collagen and a lower expression of TGF-beta1 than did the control group. Botox might be used to decrease the fibrosis of a surgical wound without damaging the epithelial growth in situations for which decreased fibrosis is necessary, such as for treating laryngeal, tracheal and nasal stenosis.