Description of a novel murine model for ileocystoplasty and early histologic changes

There is concern that bladder augmentation with bowel segments predisposes toward the development of carcinoma. Additionally, patients with neurogenic bladder and bladder cancer often present with advanced stage and have poor survival. Cellular hyperproliferation at the urointestinal junction (UIJ) has been implicated in this scenario. We aimed to develop a reproducible murine model of ileocystoplasty (ICP). We also performed preliminary analysis of any early histologic changes with focus on cellular proliferation at the UIJ. Fifteen 6- to 8-week-old female C57BL/6 mice underwent ICP, where a 1-cm ileal segment was used for bladder augmentation. Four sham mice underwent cystotomy and closure, and four mice did not undergo surgery. The mice were euthanized at 12 weeks postsurgery, and paraffin sections were stained for hematoxylin and eosin (H&E). Cellular proliferation was investigated using Ki-67. A novel model of ICP in mice was developed and demonstrated to be technically feasible in approximately 60 min under the operating microscope. Twelve-week postsurgical survival rates were 80% (12 of 15). The surviving mice had a similar weight gain as the sham mice. H&E sections showed thickened urothelium (six to 10 cell layers) at the UIJ, but sparse mitotic figures and no dysplastic changes. Ki-67 staining was rare in the urothelium, and showed no differences between the sham and ICP mice in the bladder or at the UIJ. We here demonstrate the first murine model of ICP. Preliminary studies did not show evidence of early hyperproliferation at the UIJ or in the bladder, but further long-term studies as well as studies with transgenic mice are warranted.