Blockade of osteopontin inhibits glomerular fibrosis in a model of anti-glomerular basement membrane glomerulonephritis.

BACKGROUND In our rat model for anti-GBM GN, severe fibrosis follows glomerular inflammation. A potential role of extracellular matrix protein osteopontin (OPN) in glomerular fibrosis was investigated. METHODS Neutralizing OPN antiserum or control normal serum was injected into the experimental rats at late inflammatory/early fibrotic stage. Glomerular inflammation and fibrosis were determined. RESULTS OPN antiserum treatment had little effect on glomerular inflammation. However, the antiserum treatment resulted in a significant reduction in number of fibrotic glomeruli (50% of the controls). Histology observation showed that fibrotic tissue in glomeruli of the antiserum treated rats was mild and poorly developed. OPN antiserum treatment resulted in downregulated glomerular expression of collagen 1α1; collagen deposition in the antiserum treated rats reduced to <30% of that for normal serum controls. CONCLUSION Neutralization of OPN inhibited progression of fibrosis in vivo when given at early fibrotic stage. Thus, OPN may be a therapeutic target for glomerular fibrosis.