An Immunogenic Peptide, T2 Induces Interstitial Cystitis/Painful Bladder Syndrome: an Autoimmune Mouse Model for Interstitial Cystitis/Painful Bladder Syndrome

The exact pathophysiology of interstitial cystitis/painful bladder syndrome is unknown; however, autoimmunity is a valid theory. We developed an autoimmune chronic cystitis model by administration of the medium dose of immunogenic peptide T2. Sixty female C57BL/6 mice were divided into six groups. The control group was not treated with any reagent. CFA group was injected with CFA + normal saline, homogenate group with bladder homogenate + CFA, low-dose group with low dose of T2 peptide + CFA, medium dose group with the medium dose of T2 peptide + CFA, and high-dose group with the high dose of T2 peptide + CFA. Micturition habits, withdrawal frequencies of mice, and bladders weight were measured for each group. Hematoxylin and eosin staining and toluidine blue staining were used to investigate bladder inflammation and mast cells accumulation, respectively. T cells infiltration in the bladder tissues and serum TNF-α level were measured by using immunohistochemistry and ELISA, respectively. Mice immunized with the medium dose of T2 peptide (0.225 mg/ml) were extremely sensitive to the applied force, showed greater urine frequencies, and higher bladder weights. Histologic examination revealed severe edema and inflammation in bladder tissues of medium-dose group. Extensive infiltration of T cells in bladder tissues, elevated TNF-α, and increased mast cells accumulation were observed in medium-dose group as compared to that in other groups. EAC mice model established by injecting the medium dose of T2 (0.225 mg/ml) mimics all the symptoms and pathophysiologic characteristics of IC/PBS. We believe that this model can help us to investigate the pathogenesis of IC/PBS.

Establishment of a Novel Autoimmune Experimental Model of Bladder Pain Syndrome/Interstitial Cystitis in C57BL/6 Mice

The aim of this study is to identify whether vaccinating twice with bladder homogenate can establish a new model of experimental autoimmune cystitis (EAC) in C57BL/6 strain mice. C57BL/6 mice were vaccinated with bladder homogenate in complete Freund's adjuvant (CFA) and boost immunized with bladder homogenate in incomplete Freund's adjuvant (IFA) after 2 weeks were used as the EAC model. Mice immunized with phosphate-buffered saline (PBS) in CFA or IFA were used as the control. Micturition habits and suprapubic-pelvic pain threshold were measured 4 weeks after primary immunization. Bladder to body weight ratios and expression of inflammatory cytokines and neurokinin 1 receptor (NK1R) were then examined. Histologic and immunohistochemical examination of the bladder was carried out, and IL-1β, IFN-γ, and TNF-α production by the kidneys, liver, and lungs was also tested. Double-immunized mice were extensively sensitive to pressure applied on the pelvic area (P < 0.001). Compared to single-immunized mice or controls, double-immunized mice showed more micturition frequency, lower urine output per micturition, higher bladder to body weight ratio, and significant elevation in the expression of inflammatory cytokines, including IL-1β, IL-4, IL-6, IL-10, IFN-γ, and TNF-α (all P < 0.05). NK1R gene expression was significantly increased in double-immunized mice compared to the other three groups (P < 0.001). A nonspecific immune response occurred in the liver but was much weaker than bladder inflammation. Our dual immunization EAC model in C57BL/6 mice can effectively mimic the symptoms and pathophysiologic characteristics of BPS/IC and thus can be widely used to investigate the pathogenesis and therapeutic strategies of BPS/IC.