Effects of Immunologically Induced Cystitis on Rat Bladder Histology and Permeability

Shin, Hyen Cheol; Kim, Young Soo; Kim, Dong Seok

Abstract

Interstitial cystitis is an inflammatory disease of unknown etiology. To facilitate the study of the pathophysiology of interstitial cystitis, an animal model that correlates with the etiology of interstitial cystitis and expresses histologic features consistent with those observed in interstitial cystitis patients was developed. Changes in permeability and histology were investigated in experimental cystitis induced by intravesical antigen challenge following sensitization. Rats were sensitized by intraperitoneal injection of ovalbumin (10mg/ml/kg) given on days 1, 3 and 5. The experiments were performed 4 weeks after the last injection. Controls were run simultaneously with the sensitized animals. Each group ( unsensitized and sensitized) was divided into two subgroups; Rats treated with intravesical ovalbumin (10mg/ml, 1ml) or those receiving 1ml saline intravesically. After antigen (or saline) challenge for one hour, 1ml of 14C-urea was placed into the bladder for two hours. We examined the peripheral blood concentration of 14C-urea at periods up to 120 minutes. There was a progressive increase in the blood level of 14C-urea with time only in the sensitized ovalbumin group. There was no 14C-urea present in the blood of the sensitized saline or in any unsensitized groups. We also measured mast cell density in the submucosa and detrusor muscle layer with Leiz light microscope (x 200). There was no statistical difference in submucosal mast cell densities among all groups. There was a significant increase in detrusor mast cell density only in the sensitized-ovalbumin when compared to the other groups. And degranulated mast cells in the detrusor and submucosa were found only in sensitized-ovalbumin group. With the method employed in this study, we could successfully induce cystitis in rats, without any chemical or mechanical damage to the bladder, by immunologic methods that depends on an allergic response of bladder mucosa. This experimental cystitis expresses histologic features similar to interstitial cystitis of human that increases the bladder mucosal permeability and increases the mast cell numbers in the detrusor muscle.