Tubular osteopontin expression in human glomerulonephritis and renal vasculitis

Tubulointerstitial change is a common histopathologic feature of acute and chronic glomerular diseases and is more closely correlated than glomerular damage with renal function and subsequent outcome. Monocyte infiltration is presumed to be initiated by chemoattractants and has a pivotal role in tub ulointerstitial changes. Osteopontin (OPN) is a candidate as such a chemoat tractant and has been shown to recruit monocytes into the interstitium of a nimal models of renal diseases. In this study, we investigated OPN expressi on by immunostaining and its correlation with clinical and histopathologic parameters in patients with immunoglobulin A (IgA) nephropathy, diffuse pro liferative lupus nephritis (DPLN), and myeloperoxidase-antineutrophil cytop lasmic autoantibody-associated microscopic polyangiitis (MMP), Twenty patie nts with IgA nephropathy, 12 patients with DPLN, and 14 patients with MMP w ere studied. OPN expression, which was constitutively observed on the apica l membrane of distal tubules, was upregulated in the cytoplasm of proximal and distal tubular epithelium parallel to the degree of interstitial mononu clear cell infiltration in patients with IgA nephropathy, as well as those with DPLN. CD68(+) monocyte infiltration significantly correlated with the degree of OPN expression in the tubular epithelium. Conversely, there was n o apparent induction of OPN in the proximal and distal tubular epithelium o f patients with MMP despite remarkable monocyte infiltration. In conclusion , these data suggest that inducible expression of OPN in the tubular epithe lium seems to be associated with interstitial monocyte infiltration and sub sequent tubulointerstitial changes in some forms of human renal diseases. ( C) 2000 by the National Kidney Foundation, Inc.