In vitro investigations of tissue-engineered multilayered urothelium established from bladder washings

Human urothelial cells (HUCs) are commonly isolated from native urothelium requiring open or endoscopic surgery. The aim of this study was to raise primary monolayer cultures of HUCs from bladder washings, to generate multilayered urothelial sheets in vitro, to characterise the sheets immunologically, and to prove their viability.

Irrigation fluids were taken from 29 adult patients. Isolated cells were cultured in serum-free keratinocyte medium. Confluent monolayer cultures were stratified, and evolved cell sheets were harvested after 10-16 d. Pancytokeratins and cytokeratin 20 (CK20) in the stratified cultures and the detached sheets were immunologically detected. To exclude the presence of mesenchymal cells, antibodies against fibroblast surface antigen and smooth muscle alpha-actin were used. In addition, expression of p63 and uroplakin III was investigated. The viability of the detached cell sheets was proven by establishing explant cultures of small sheet sections.

Confluent primary HUC cultures were established in 55.2% of the collected bladder washings between days 15-20. Multilayered urothelium developed in 62.5% of the monolayers. Histology revealed stratified cell layers similar to native urothelium. Both stratified cultures and detached sheets stained 100% positive for pancytokeratins and partially for CK20, indicating differentiation into superficial cells. No positive staining was observed with the mesenchymal markers used. p63 was expressed partially. Uroplakin III expression was not observed. Cell sheet viability was confirmed by rapid cell outgrowth in explant cultures.

Isolation of HUCs from bladder washings is a minimally invasive approach to establish primary urothelial cultures for creating autologous multilayered urothelial sheets.