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Clues to the mystery of feline idiopathic cystitis

Treutlein G, Dorsch R, Euler KN, et al. Novel potential interacting partners of fibronectin in spontaneous animal model of interstitial cystitis. PLoS ONE. 2012; 7: e51391. [Free, full text]
Researchers from Ludwig Maximilian University of Munich and collaborators recently showed that cats diagnosed with feline idiopathic cystitis (FIC) have increased urinary fibronectin compared to healthy cats and to cats with urinary tract infection or urolithiasis. In this study, the researchers further investigated fibronectin and its interaction with other proteins in the urine and urinary bladder tissue of cats with FIC and provide additional insight into the pathophysiology of this disease.

Feline idiopathic cystitis is a common disease condition afflicting 50-69% of cats presenting with lower urinary tract signs. The underlying pathomechanism of FIC has not been clearly established. Many theories have been proposed including environmental stress with inappropriate neuroendocrine response, disruption of the urinary bladder urothelium glycosaminoglycan layer affecting bladder permeability, viral infection (e.g., feline calicivirus, feline herpesvirus, feline syncytial-forming virus), and dietary triggers (e.g., ash content, dry cat food, fish-flavored cat food). The pathophysiology of FIC is likely a systemic disease condition involving complex interactions between several body systems (i.e., nervous, endocrine, immune, and cardiovascular). 

Fibronectin is a high-molecular weight glycoprotein of the extracellular matrix, and is involved in cell adhesion, migration, growth, differentiation and wound healing. Alteration of fibronectin expression, degradation, and organization has been associated with various pathologies, including cancers and fibrosis. Fibronectin and its interaction with other proteins in cats with FIC suggest a more important role of fibrosis in the pathogenesis of this disease.

A total of 46 urine samples were collected from two groups of cats: the FIC group (n=26) and the healthy control group (n=20). Immunoprecipitation and mass spectrometry were used to identify proteins that co-precipitated with urinary fibronectin. In addition, urinary bladder tissue from 3 cats with obstructive FIC and 4 healthy cats were examined using immunohistochemical methods to investigate expression patterns of identified co-purified proteins of fibronectin. The authors identified eight proteins that co-purified with fibronectin. Expression patterns in urine and bladder tissue of four of these proteins (C4a, Galectin-7, I-FABP and thioredoxin) were determined. Results suggest that cell death, tissue damage, inflammation, and oxidative stress are part of the pathogenesis of FIC. Further work is required to continue the process of understanding this complex disease. [GO]

See also: Lemberger SIK, Deeg CA, Hauck SM, et al. Comparison of urine protein profiles in cats without urinary tract disease and cats with idiopathic cystitis, bacterial urinary tract infection, or urolithiasis. Am J Vet Res. 2011; 72: 1407-15.