OBJECTIVETo investigate the feasibility of bone marrow mesenchymal stem cells(MSC)with the acellular dermal matrix(ADM) biological patch for the treatment of external anal sphincter injury on the animal models.

METHODSThirty Wistar rats with sphincter injury were randomly divided into three groups. Group A underwent end to end sphincteric repair directly, group B underwent end to end repair and then covered by ADM patch, and group C underwent end to end repair and then covered by ADM which was previously seeded with MSC. After six weeks, the whole ring specimens including anal canal and lower rectum were removed. The hematoxylin and eosin stain and Masson trichrome stain were performed to observe the change of histomorphology.

RESULTSTwo weeks later, the majority of rat models presented with moist anus and crissum with loose stools, which indicated that the model was established successfully. Six weeks after repair, in group A and B, the suffusion of fibrous connective tissue and the infiltration of inflammatory cells were observed at the repair site of sphincter. And lots of collagen fiber which was stained into blue deposited dispersedly at the site of repair with no obvious proliferation of capillaries. However, in group C, the blue collagenous fiber which deposited at the sphincter injury site was less than that in groups A and B. Muscle fibers were observed to be stained into red distributed dispersedly at the repair site of sphincter in group C.

CONCLUSIONSTransplantation of ADM biological patch rich in bone MSC can partly improve the regeneration of rat injured anal sphincter and lessen the formation of cicatrix.