Cell Proliferation and DNA Content in Rat Urothelial Lesions after Repeat Intravesical Instillations of Mitomycin C and Bacillus Calmette-Guérin

Abstract

Aim: To study cell proliferation and DNA content in urothelial lesions identified after repeated intravesical instillations of mitomycin C (MMC) and bacillus Calmette-Guérin (BCG) in normal rat urothelium. Material and Methods: A total of 45 rats were divided into nine equal groups: those intravesically instilled with MMC; those receiving BCG intravesically, and a control group intravesically instilled with a physiological solution of sodium chloride (SF). Animals were killed 1, 4 or 8 weeks after the last intravesical instillation. An immunohistochemical streptavidin-biotin-peroxidase technique was performed to investigate Ki-67 expression and the DNA ploidy status was measured using static cytometry. Results: In urothelium exposed to MMC lesions such as simple hyperplasia, dysplasia, carcinoma in situ(CIS), and squamous cell metaplasia were identified. The proliferation index presented values of 11.73, 22.43 and 31.46% in hyperplasias, dysplasias, and CIS, respectively (p < 0.05). The frequency of abnormal DNA content amongst those animals exhibiting simple hyperplasias 25% were aneuploid, in the dysplasia 85.2% were aneuploid (p = 0.041). CIS were all multiploid, and squamous cell metaplasias were all diploid. Animals treated with BCG and SF presented no urothelial lesions and a diploid DNA content. Conclusions: The aneuploid and multiploid DNA content and proliferation index observed in urothelial lesions identified after repeated intravesical instillations of MMC reflect a high degree of genomic instability in such lesions which in itself may lead to rapid regeneration of new phenotypes.