Experimental assessment of small intestinal submucosa as a bladder wall substitute

This study determined the feasibility of promoting urinary bladder regeneration with porcine-derived small intestinal submucosa (SIS). Twenty-two Sprague-Dawley rats underwent partial cystectomy with immediate bladder augmentation with SIS. Bladders were harvested for histologic evaluation at 2, 4, 8, 12, 24, and 48 weeks. Histologically at 2 weeks, there was infiltration of the graft material with viable host cells consisting of fibroblasts, macrophages, and blood vessels covered by complete mucosal urothelium comprised of transitional cells. During the next 10 weeks, collagen formation and maturation were noted, and by the end of 12 weeks, the SIS graft was comprised of a mature collagen matrix admixed with thinly scattered disorganized smooth muscle bundles and covered by normal urothelium. At 48 weeks, all three layers of the normal bladder (urothelium, smooth muscle, and serosa) were present and were grossly and microscopically indistinguishable from the normal rat urinary bladder. This study further supports the concept of bladder regeneration and suggests that SIS may be a viable material for bladder augmentations.