Reproduction of functional smooth muscle tissue and partial bladder replacement

OBJECTIVE: To find a means of bladder augmentation that would avoid the complications encountered with the use of bowel segments, using a newly developed acellular biomaterial, the bladder acellular matrix graft (BAMG), as a homologous graft. MATERIALS AND METHODS: Thirty-four rats underwent a partial cystectomy (40-50%) and grafting with a BAMG of equal size. Eleven rats died within the first 72 h. probably from urinary leakage caused by obstruction of the bladder neck with stones or coagula; the surviving 23 were killed at varying intervals after cystectomy and examined. RESULTS: After providing initial bladder enlargement, the graft was progressively infiltrated by the vessels and smooth muscle cells of the host: furthermore, the mucosal lining was complete within 10 days. After 4 weeks, all bladder wall components were evident histologically in the graft. The ingrowth was complete after 8 weeks, except for neural regeneration, which was only partial. At 12 weeks, the bladder wall muscle structure in the graft was so well developed that it was difficult to delineate the junction between host bladder and BAMG. Neural regeneration continued to improve. Normal bladder capacities were maintained throughout the study. CONCLUSION: The BAMG appears to serve, without rejection, as a framework of collagen and elastin for the ingrowth of all bladder wall components. The reason for the better acceptance of the BAMG than of other bladder augmentation grafts requires further investigation.