Sphincter contractility after muscle-derived stem cells autograft into the cryoinjured anal sphincters of rats

PURPOSE: This study was designed to determine whether the injection of muscle-derived stem cells into the anal sphincter can improve functional properties in a fecal incontinence rat model. METHODS: Cryoinjured rats were utilized as a fecal incontinence model. The gastrocnemius muscles of normal three-week-old female Sprague-Dawley rats were used for the purification of the muscle-derived stem cells. The experimental group was divided into three subgroups: normal control; cryoinjured; and muscle-derived stem cells (3 × 10⁶ cells) injection group of cryoinjured rats. All groups were subsequently employed in contractility experiments using muscle strips from the anal sphincter, one week after preparation. RESULTS: Contractility in the cryoinjured group was significantly lower than in the control after treatment with acetylcholine and KCl. In the muscle-derived stem cells injection group, contraction amplitude was higher than in the cryoinjured group but not significantly (20.5 ± 21.3 vs. 17.3 ± 3.4 g per gram tissue, with acetylcholine (10^-4 mol/l); 31 ± 14.2 vs. 18.4 ± 7.9 g per gram tissue, with KCl (10^-4 mol/l)). PKH-26-labeled transplanted cells were detected in all of the grafted sphincters. Differentiated muscle masses stained positively for alpha smooth muscle actin and myosin heavy chain at the muscle-derived stem cells injection sites. CONCLUSIONS: This is the first study reporting that autologous muscle-derived stem cell grafts may be a tool for improving anal sphincter function.