Time- and temperature-dependent autolysis of urinary bladder epithelium during ex vivo preservation

Morphological and functional preservation of urinary bladder epithelium-urothelium after extirpation from an organism enables physiological studies of that tissue and provides the basis for successful organ transplantations. The aim of this study was to determine the optimal temperature for maintaining urothelium in ex vivo conditions. Mouse urinary bladders were kept at the three temperatures usually used for maintaining tissue during transportation: at the temperature of melting ice (1°C), at room temperature (22-24°C), and at the body temperature of most mammals (37°C). Autolytic structural changes were followed with electron microscopy, while destruction of cytoskeleton and intercellular junctions was observed by immunolabeling. The first ultrastructural changes, swelling of mitochondria and necrosis of individual cells, became evident 30 min after extirpation if the tissue was kept at 1°C. After 60 and 120 min in ex vivo conditions, the most severe changes with increasing plasma membrane ruptures were detected at 1°C, while at room temperature only mild changes were detected. At 37°C, the extent of ultrastructural changes was between those of the other two experimental temperatures. Autolytic destruction of cytoskeleton and intercellular junctions was not observed before 2 h after extirpation. After 4 h, severe degradation of cytokeratin 20 and microtubules were found at 1°C and 37°C, while being almost undisturbed at room temperature. On the other hand, the reduction of desmoplakin and ZO-1 labeling was more evident at 37°C than at 1°C and room temperature. These findings provide evidence that room temperature is most appropriate for short ex vivo preservation of urothelial tissue.