Functional External Anal Sphincter Reconstruction for Treatment of Anal Incontinence Using Muscle Progenitor Cell Auto Grafting

Abstract

This study aimed to investigate the feasibility of autologous muscle progenitor cell transplantation for anal sphincter regeneration in a rabbit model of anal incontinence. We examined the serial changes in structure, with particular emphasis on histology and functional properties of the anal sphincter. External anal sphincterotomy was performed in 21 rabbits; these rabbits were randomly assigned to 2 groups. In group I (n = 9), autologous muscle progenitor cells were isolated from quadriceps myofiber explants, labeled with PKH-26, and injected into sphincter 3 weeks after sphincterotomy. In group II (n = 12), saline buffer was injected at the site of damage. Sphincter electromyography and manometry were performed immediately before sphincterotomy and 14, 28, and 60 days after injection in 3 animals in each group at every interval and the findings were correlated with histomorphological studies. In addition, electromyography and manometry were performed in the remaining 3 rabbits in group II after 6 months. In group II, a flaccid sphincter persisted during the 6 months of follow-up. In group I, muscle progenitor autografting accelerated sphincter myofiber repair and improvement in functional capacity of the damaged sphincter. Fluorescently labeled cells were detected in all of the grafted sphincters; regenerated myotubes were detectable at the injection site as evidenced by the presence of desmin. We also observed a significant decrease in interstitial fibrosis in the 4th week and strikingly higher amounts of Ki-67-positive cells in group I. Manometry and electromyography showed a significant improvement in the mean resting anal canal pressure and sphincteric electrical activity 4 weeks after cell injection, respectively. Transplanting muscle progenitor cells showed the potential for recapitulation of a myogenic program when injected into deficient rabbit anal sphincter. Objective anal measures of resting and stimulated pressures and electromyographic profile improved. Stem cell-mediated anal myoplasty warrants additional investigation as a new method to treat anal incontinence before attempting this modality in the clinical setting.