Long-term inflammatory and neoplastic reaction of prostate tissues during its transurethral infection with uropathogens: evaluation of the results of animal model study

Introduction. There is no convincing evidence of the persistence of acute or the development of chronic bacterial-induced prostatic inflammation in the long term when infected with various titers of the uropathogen. Along with this, controversial data are presented on the relationship between post-infectious chronic inflammation and neoplastic changes in prostate tissues. Objective. To carry out, based on the experimental data: 1) assessment of the degree ofbacterial contamination and the severity ofhistological changes in prostate tissues on the 60th follow-up day in case of transurethral infection with various uropathogens in titers of 102,3,5 CFU/ml; 2) fundamental comparative analysis between the indicators of the inoculated test-titer and microbial load with the severity of histological changes in prostate tissues; 3) verification of neoplastic transformations in the prostate tissues during a long-term persistent bacterial-induced inflammatory process. Materials and methods. Animal studies were conducted using FELASA protocols. Laboratory animals: 14 New Zealand rabbits. Tested uropathogens: aerobes - E. coli, S. haemolyticus, anaerobes - P. niger. Titers: 102,3,5 CFU/ml. Uropathogen inoculation technique: topical transurethral. Randomization: all laboratory animals were divided into 5 groups according to the uropathogen (4 experimental, 1 control). Follow-up period: 60 days. Sacrification and autopsy of the animals were performed on day 60. Biopsies were taken from various parts of the prostate, as well as from the bladder neck and the edge of the membranous urethra. Cultural, histological and immunohistochemical (expression of p53 and Ki-67) studies of prostate tissues were conducted. Statistical data processing was performed using the GraphPad Prism 9.0 program (GraphPad Software Inc., Graphpad Holdings LLC, San Diego, CA, USA) applying descriptive and non-parametric statistics. Results. Two individuals infected with S. haemolyticus + P. niger had a lethal outcome. The contamination of prostate tissue was determined in all cases of infection. In 88.9% of the cases, an increase in tissue microbial load was determined compared to the initial titer. Multivariate analysis of culture study values revealed the presence of intragroup differences in prostate contamination only between infection with E. coli 103 CFU/ml and E. coli 105 CFU/ml (p=0.006), as well as intergroup differences between infection with E. coli 105 CFU/ml and P. niger 105 CFU/ml (p=0.013). The histological study revealed moderate proliferative inflammation after inoculation with 102,3,5 CFU/ml in the E. coli and S. haemolyticus groups. In the case of S. haemolyticus, it was more pronounced due to the presence of persistent alterative lesion foci; in the P. niger group, mild proliferative transformations were observed in prostate tissues in all cases. The immunohistochemical study of changes determined p53 expression (=10.0%) in some areas ofthe glandular epithelium of prostate glands (but without a positive internal control) only in case of infection with E. coli 105 CFU/ml. Areas of glandular epithelium with Ki-67 expression (625.0%) were visualized in all tested groups, mainly at titers of 103 and 105 CFU/ml, but the severity of proliferative activity was not high (1+). There were no foci of prostate tissue with simultaneous nuclear activity of p53 and Ki-67. Conclusion. Proliferative inflammation of different intensity in prostate tissues was observed after sixty days. Its severity was mainly determined by the type of infecting agent (S. haemolyticus > E. coli > P. niger) and was not dependent on the inoculated titer and the subsequent microbial load of prostate tissues. No areas of neoplastic transformation of prostate tissues were reliably identified in the case of a bacterial-induced inflammatory process in the estimated follow-up period.

Ki-67, prostatitis, bacterial, contamination, prostate cancer, p53, Ki-67, animal model