Cell relationship in a Wistar rat model of spontaneous prostatitis.

PURPOSE: Prostatitis in men is a painful, noninfectious inflammatory condition. It is similar to interstitial cystitis which is associated with increased bladder mast cell and sensory nerve fiber density as well as suprapubic pain. Certain strains of rats may provide a useful model for studies of the development of spontaneous prostatitis. We evaluated the time course, and involvement of mast cells and sensory nerve fibers in this process using Wistar rats. MATERIALS AND METHODS: The prostates of 4, 6, 8, 10 and 13-week-old male Wistar rats were examined for the degree of inflammation, innervation, mast cell density and nerve mast cell relationship using histochemical and immunocytochemical studies. Bacterial cultures of tissue were performed at 13 weeks. RESULTS: The inflammatory cell index increased progressively with age. Inflammation was moderate and consisted mostly of lymphocytes and macrophages associated with occasional glandular epithelial necrosis and edema. The density of nerve fibers immunoreacting with the neuronal marker protein gene produce 9.5 increased gradually with age and fibers immuno-positive for the sensory neuropeptide calcitonin gene-related peptide more than doubled by 13 weeks compared with by 4 weeks. The density of visible mast cells declined after 4 weeks in a pattern that corresponded with the increased percent of mast cells undergoing degranulation. For the mast cells with calcitonin gene-related peptide immuno-positive nerve fibers within a distance of 40 microm. distance correlated significantly with the degree of degranulation. Bacterial cultures were negative at 13 weeks. CONCLUSIONS: Our results confirm previous reports of spontaneous prostatitis in Wistar rats and indicate that moderate inflammation may occur in 80% of rats at as early as age 13 weeks. While the correlation of the nerve mast cell axis with mast cell degranulation does not prove our hypothesis of mast cell mediated inflammatory mediator release in the development of nonbacterial prostatitis, it suggests that such a relationship is possible.