Expression of alpha-smooth muscle actin and fibronectin in tubulointerstitial lesions of cats with chronic renal failure

Objective-To examine renal expression of alpha-smooth muscle actin (alpha-SMA) and fibronectin in cats with tubulointerstitial nephritis (TIN) for use in predicting progression to renal fibrosis. Animals-19 cats with TIN and 9 cats without nephritis. Procedure-Serum creatinine and BUN concentrations were measured. Indices for glomerular extra-cellular matrix (ECM), tubular injury (TI), and fibronectin were determined in renal specimens to quantify the extent of injury and fibrotic lesions. Expression of alpha-SMA in renal tissue was immunohistochemically detected, and correlations were evaluated between the alpha-SMA index and other histologic and clinical variables. Results-The alpha-SMA index in tubulointerstitial areas (1.63 +/- 0.78) was significantly higher in cats with TIN, especially in the periglomerular and peritubular areas, than in cats without nephritis (0.20 +/- 0.14). The alpha-SMA index was significantly associated with the TI index (r(2) = 0.70), fibronectin index (r(2) = 0.95), BUN concentration (r(2) = 0.64), and serum creatinine concentration (r(2) = 0.66). Of special interest was that interstitial alpha-SMA expression appeared evident in the kidneys at an early stage of TIN, prior to the onset of ECM deposition. Conclusion and Clinical Relevance-Analysis of results of histologic and clinical examinations revealed that interstitial alpha-SMA expression may have clinical importance and may be a useful early histologic marker for development of chronic renal failure in cats. An immunohistochemical examination for fibrogenic molecules (such as alpha-SMA expression) may provide fundamental information on the pathogenesis of early-stage renal disease and aid clinical management of cats with chronic renal failure, including TIN.