Comparison of urine protein profiles in cats without urinary tract disease and cats with idiopathic cystitis, bacterial urinary tract infection, or urolithiasis

Objective—To characterize and compare the urine protein content in cats without urinary tract disease and cats with idiopathic cystitis (IdC), bacterial urinary tract infection (UTI), or urolithiasis. Animals—Control cats (n = 18) and cats with IdC (18), UTI (12), and urolithiasis (12) from which urine samples were obtained and 2 cats with obstructive IdC and 4 additional control cats from which postmortem urinary bladder biopsy specimens were obtained. Procedures—Protein contents in urine samples obtained via cystocentesis or catheterization were measured via the Bradford method. Urine proteins were separated by means of 1-dimensional gel electrophoresis. Evaluation of fibronectin content was performed via western blotting and immunohistochemical analysis. Urinary bladder biopsy specimens were examined histologically and analyzed immunohistochemically for fibronectin. Results—Urine fibronectin content was significantly greater in cats with IdC, compared with control cat findings. Urine fibronectin contents did not differ significantly among controls and cats with UTI or urolithiasis. Histologic examination of bladder biopsy specimens obtained from 2 cats with obstructive IdC revealed destruction of the urothelial lining of the urinary bladder and severe fibrosis; immunohistochemical analysis revealed few fluorescence signals for fibronectin, unlike findings in control bladder biopsy specimens. Conclusions and Clinical Relevance—Results indicated that urine fibronectin content in cats with IdC was greater than that in controls, cats with UTI, or cats with urolithiasis. In cats with IdC, increased permeability of damaged urothelium may result in detachment and leakage of fibronectin into urine. Urine fibronectin might serve as a biomarker for diagnosis of IdC in cats.