Bladder cancer cell implantation in reconstructed bladder in vitro: a model of tumour recurrence

OBJECTIVE: To evaluate the involvement of umbrella cells in tumour adhesion and growth, by examining whether human urinary bladder carcinoma cells (HUBCC) can grow on reconstructed urinary bladder mucosa in vitro, as the implantation of tumour cells after resection is thought to be a cause of bladder tumour recurrence. MATERIALS AND METHODS: Normal transitional epithelial cells isolated from porcine bladder were cultured on reconstructed lamina propria using fibroblasts in type I collagen gel. The urothelium thus reconstructed was artificially injured either by a scalpel or by dilute acid, after which transitional epithelial cells began to grow in a stratified fashion within a few days of culture. A HUBCC line (HT-1197) was seeded onto this impaired mucosa to determine whether the cells could become implanted. Cultured cells on the reconstructed mucosa were evaluated by histological observation of vertical paraffin sections. RESULTS: The inoculated transitional epithelial cells grew in a stratified fashion and closely resembled urothelium in vivo. The superficial cells that were in contact with the medium solution differentiated into umbrella cells. HUBCC were unable to adhere to reconstructed mucosa which had not been injured, but these cells could adhere to and become implanted on the reconstructed mucosa after it had been injured either by a scalpel or by dilute acid. After acid injury, only the surface-covering cells were removed sporadically, while the lower epithelial cell layer remained intact. The bladder cancer cells adhered to and proliferated within these stripped regions. CONCLUSION: These results suggest that the urothelium, especially umbrella cells, seems to be important in preventing the adhesion and growth of urinary bladder tumour cells.