Elucidation of the pathophysiology of interstitial cystitis/bladder pain syndrome via experimental autoimmune cystitis rat model

Although the cause of interstitial cystitis/painful bladder syndrome (IC/PBS) remains unknown, autoimmune involvement has been strongly suggested to be a contributing factor. To elucidate the pathophysiology of IC/PBS, we characterized the experimental autoimmune cystitis (EAC) in rats. Adult female Sprague-Dawley rats were divided into the EAC and control groups. The EAC rats were generated by administrating a homogenate of donor rat bladder tissue as a bladder antigen. The characteristics of the two groups were determined by evaluating pain behavior and conducting cystometry, histopathology, and molecular analyses. The EAC rats showed: [1] a decreased paw withdrawal threshold, [2] a reduced intercontraction interval on cystometry, [3] the irregular surfaces of the umbrella cells of epithelium throughout the bladder wall, [4] accumulation of stress granules in the bladder and vascular endothelium, [5] the increased expression of genes related to inflammation and ischemia at the mRNA and protein levels, [6] a significantly increased paw withdrawal threshold with pain treatment, and [7] the induction of glomerulation of the bladder wall, epithelium denudation, and lymphocyte infiltration in the interstitium by bladder distension. These results suggest that the EAC rats showed pain and frequent urination with the overexpression of inflammatory chemokines, reflecting clinical IC/BPS, and the bladder epithelium and vascular endothelium may be the primary sites of IC/BPS, and bladder injury such as bladder distension can cause progression from BPS to IC with Hunner lesions.