Immunohistochemical and urinary markers of podocyte injury

Renal podocytes play an important role in glomerular filtration. We estimated podocyte injury by light microscopic examination of kidney specimens or by urinary excretion of substances related to podocytes. Fresh kidney sections from 69 patients and urinary sediments from 84 patients with various renal diseases were examined immunohistochemically using fluorescent labelling. Four kinds of monoclonal antibodies which recognize podocytes were used: (1) anti-podocalyxin (anti-PCX) antibody, (2) anti-C3b receptor (anti-C3bR) antibody, (3) anti-podocyte protein, 44 kilodalton, (anti-pp44) antibody, and (4) anti-alpha 3 integrin (anti-Intα3) antibody. Labelling of kidney sections by anti-C3bR (k-C3bR) was reduced in cases of severe glomerular injury, although there were no changes in k-PCX, k-pp44, or k-Intα3 labelling. PCX labelling of urinary sediments (u-PCX) was detected in nearly all cases of glomerulonephritis, u-C3bR was seen in some cases of glomerular injury, u-Intα3 was seen in only a small number of cases of severe glomerular injury, and u-pp44 was not detected in any urinary samples. u-PCX, u-C3bR, u-Intα3, and k-C3bR correlated with the degree of pathological change, the degree of proteinuria and hematuria. These results suggest that immunostaining kidney sections with anti-C3bR antibody and urinary sediments with anti-PCX, anti-C3bR, and anti-Intα3 antibodies might be useful in detecting podocyte injury. Received March 17, 1997; received in revised form and accepted August 1, 1997