Improvement of Urethral Sphincter Deficiency in Female Rats following Autologous Skeletal Muscle Myoblasts Grafting

Abstract

Sphincteric deficiency is the most common cause of urinary incontinence in humans. Various treatments have lead to disappointing results due to a temporary benefit. Recent studies raised the possibility that sphincteric deficiency could be treated by implanting skeletal myoblasts. In the present study, we developed in the female rat a model of chronic sphincteric defect to assess the benefit of myoblast injection. Sphincter deficiency was induced by freezing, longitudinal sphincterotomy, and notexin injection, respectively, to obtain a reproducible and irreversible incontinence. Autologous tibialis anteriors were cultured to be injected in the best model. Functional results were evaluated by measuring the urethral pressure with an open catheter. Histology was performed in the excised urethras. Of the three techniques, only longitudinal sphincterotomy caused definitive incontinence by irreversibly destroying the striated sphincter muscle fibers: a 45% decrease of the closure pressure was observed 21 days after the sphincterotomy. At this time, we injected myoblasts at the sphincterotomy site. In the sham-injected group (n = 18), the closure pressure decrease was not significantly modified 21 days after injection. By comparison, a return to near normal value was observed after cell grafting (n = 21). These results and those obtained by others strongly suggest that the use of myoblasts could be a potential innovative therapy for urethral deficiencies leading to incontinence.