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-S MA) 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 fo r glomerular extra-cellular matrix (ECM), tubular injury (TI), and fibronec tin were determined in renal specimens to quantify the extent of injury and fibrotic lesions. Expression of alpha-SMA in renal tissue was immunohistoc hemically detected, and correlations were evaluated between the alpha-SMA i ndex 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 an d peritubular areas, than in cats without nephritis (0.20 +/- 0.14). The al pha-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 seru m creatinine concentration (r(2) = 0.66). Of special interest was that inte rstitial alpha-SMA expression appeared evident in the kidneys at an early s tage of TIN, prior to the onset of ECM deposition. Conclusion and Clinical Relevance-Analysis of results of histologic and cli nical examinations revealed that interstitial alpha-SMA expression may have clinical importance and may be a useful early histologic marker for develo pment of chronic renal failure in cats. An immunohistochemical examination for fibrogenic molecules (such as alpha-SMA expression) may provide fundame ntal information on the pathogenesis of early-stage renal disease and aid c linical management of cats with chronic renal failure, including TIN.