Urothelium regeneration using viable cultured urothelial cell sheets grafted on demucosalized gastric flaps

Most of the papers in this section are studies of cellular biology in urological cancer. Each of the four papers assess a particular aspect of four different types of cancer: prostate, bladder, renal, and testicular. The other two reports are on unrelated issues; in the first, the authors write about urothelial regeneration using viable cultured urothelial cell sheets grafted onto demucosalized gastric flaps, and in the second, on the in vivo expression of nitric oxide synthase. OBJECTIVE To evaluate urothelium regeneration by grafting viable cultured urothelial cell sheets, harvested from temperature‐responsive culture surfaces, on demucosalized gastric flaps in a dog model. MATERIALS AND METHODS Viable urothelium was obtained from eight beagle dogs by partial cystectomy. Harvested urothelial cells were seeded on temperature‐responsive culture dishes modified with the thermally sensitive polymer, poly(N‐isopropylacrylamide). Urothelial cells cultured for 3 weeks generated contiguous urothelial cell sheets that were noninvasively harvested with no enzymatic treatment from these dishes, by reducing culture temperature. Urothelial cell sheets were autografted onto surgically demucosalized gastric flaps. Three weeks after autografting the dogs were killed and the gastric flaps with the urothelial cell sheets were examined. Cell and tissue characteristics were compared between these urothelial cell sheet‐grafted gastric flaps and native urothelium. Ultrafine structures were also examined by electron microscopy. RESULTS Five of the eight urothelial cell sheet‐grafted flaps showed viable urothelial regeneration. Urothelial cell sheets attached spontaneously to demucosalized tissue surfaces completely, with no suture or fixing, and developed into a stratified viable epithelium very similar to native urothelium. Regenerated urothelium remained unstained by antiproton pump antibody, which typically stains epithelial cells positively in gastric mucosal layers. On three of the eight flaps where there were severe haematomas, grafted cell sheets were not adherent and there was no urothelial regeneration. CONCLUSIONS Urothelial cell sheets were autografted onto dog demucosalized gastric flaps successfully, with no suture or fixation, generating a multilayered urothelium in vivo . The novel intact cell‐sheet grafting method rapidly produces native‐like epithelium in vivo . This versatile technology should prove useful in urinary tract tissue engineering and surgical reconstruction.