AB45. URO-MCP-1 mice: a model demonstrating UCPPS hallmark symptoms

Introduction and objective: Excessive production of monocyte chemotactic protein-1 (MCP-1) has been observed in various inflammatory, chronic pain, and bladder overactive conditions. We have observed that over half of patients with interstitial cystitis/bladder pain syndrome (IC/BPS) express elevated MCP-1 in the urine. This study was to develop a mouse model that secretes MCP-1 by the urothelium to facilitate the study of IC/BPS in humans.

Methods: A 4.9 Kb transgene consisting of the uroplakin II gene promoter and mouse MCP-1 coding sequence with a secretory element was constructed and microinjected for developing a MCP-1 secreting transgenic mouse line (URO-MCP-1). Mice were screened by tail genotyping and backcrossed onto the C57BL/6 genetic background. RT-PCR was used to assess MCP-1 mRNAs in the bladder and ELISA used to assess MCP-1 protein in the urine. To induce bladder inflammation, lipopolysaccharide (LPS) was administered intravesically. Bladder inflammation was analyzed by histological hematoxylin and eosin (H&E). Von Frey filament stimulation was used to assess pelvic pain and micturition cages used to assess voiding dysfunction. Cadi-05, a novel Toll-like receptor modulator, was intradermally administered once daily for total three doses starting one day before cystitis induction up to day 1. The bladders were analyzed by histological H&E staining at day 2.

Results: URO-MCP-1 mice express MCP-1 mRNA in the bladder but not in other organs. Urine contains ~1,500 pg/mL of MCP-1. While the bladders of URO-MCP-1 mice were normal in the unmanipulated state, they exhibited a much lower threshold trigger for producing exaggerated responses to otherwise sub-noxious inflammatory stimuli such as LPS. Compared to control C57BL/6 mice, URO-MCP-1 mice exhibited clear histological bladder inflammation with intensive edema and cellular infiltration 24 hours after intravesical instillation of even a single low dose of LPS (1 µg in 100 µL). The bladder inflammation peaks at days 1-3 and lasts 5-7 days. URO-MCP-1 mice exhibited pelvic pain and increased urinary frequency and decreased urine output per void after cystitis induction (P<0.05). Intradermal Cadi-05 treatment significantly reduced bladder histopathology (P<0.01).

Conclusions: The URO-MCP-1 model exhibits key symptomatology of IC/BPS and is responsive to intradermal Cadi-05 therapy. This model offers a unique translational opportunity for investigation of the pathological mechanisms and therapeutic development for the human disease.

Keywords: URO-MCP-1 mice; UCPPS; lipopolysaccharide (LPS)