The use of Botulinum toxin-a injection for facial wrinkles: a histological and immunohistochemical evaluation.

Botulinum toxin (BTX)-A has been used for years in the reduction of facial wrinkles; however, histological and immunohistochemical changes after its use were not previously investigated. To evaluate histological and immunohistochemical changes after BTX-A injection for facial wrinkles, sixteen volunteers, with wrinkles on the upper third of the face, were subjected to single injection of BTX-A. Skin biopsy specimens were obtained from peri-orbital wrinkle site (crow's feet area) before and after 3 months of BTX-A injection. Using histological and immunohistochemical evaluation coupled with computerized morphometric analysis, measurement of epidermal thickness, wrinkle depth and width as well as quantitative evaluation of collagen types I and III and elastin was performed for skin biopsies. After BTX-A injections, there were significant increase in wrinkle width and granular layer thickness (P < 0.001), while the other histometrical measures as well as the immunohistochemical expression of collagen types I and III and elastin showed no significant difference (P > 0.05). However, collagen fibers showed better organization and orientation after BTX-A injection. The histological changes observed after BTX-A injection for facial wrinkles may help in better understanding of its mechanism of action.