Successful engraftment of bladder organoids in de-epithelialized mouse colon.

Purpose: To engraft bladder organoids (BO) on de-epithelialized mouse colon using an epithelial replacement technique. Methods BO cultured using bladder specimens from enhanced green fluorescent protein (EGFP) transgenic mice were engrafted to replace proximal colon epithelium stripped from an approximately 1cm long target site in syngeneic wild-type recipient mice (n = 9) by exposure to ethylenediaminetetraacetic acid by infusion and flushing with phosphate buffered saline. Target sites were harvested on postoperative days 2, 7, and 28 for hematoxylin-eosin staining and immunofluorescence. Results Histology on postoperative days 7 and 28 showed BO derived EGFP + cells forming multiple layers on the luminal surface of the colon. Immunohistochemistry showed that EGFP + areas were positive for CK5 and CK14, markers for basal and immature subtype urothelium, respectively, but negative for CA2, a marker for colonic epithelium. Ki67 was detected predominantly in the basal parts of EGFP + areas on post-operative day 7 and day 28. Conclusions This is the first report of successful engraftment of BO in de-epithelialized colon with urothelial tissue reconstituted by actively-proliferating cells. This technique could be developed for augmentation cystoplasty to prevent bladder calculi formation and malignant transformation.