Expression of nephrin in pediatric kidney diseases

Nephrin is a podocyte cell adhesion protein located at the slit diaphragm a rea of the kidney glomerulus. Mutations in the nephrin gene (NPHSl) lead to congenital nephrosis, suggesting that nephrin is essential for the glomeru lar filtration barrier. This prompted this study of the expression of nephr in in acquired pediatric kidney diseases using in situ hybridization and im munohistochemistry. In situ hybridization for nephrin mRNA was performed in biopsy samples from patients with proteinuria caused by minimal change nep hrosis, focal seg mental glomerulosclerosis, and membranous nephropathy. Th e expression of nephrin mRNA was evaluated by grading the signal intensity visually and by counting the number of grains in separate glomeruli. No sig nificant difference was observed in these samples as compared with controls . Immunostaining for nephrin was performed using antibodies directed agains t extra- and intracellular parts of the molecule. Nephrin staining gave a l inear pattern along the glomerular capillary loops. In minimal change nephr osis, focal segmental glomerulosclerosis, and membranous nephropathy, the d istribution of nephrin was similar to that in controls. In proliferative fo rms of glomerulonephritides (Henoch-Schonlein nephritis, IgA nephropathy, p ostinfectious and membranoproliferative glomerulonephritis), crescents and sclerotic lesions were negative for nephrin, and mesangial proliferation le d to a scattered and sparse staining pattern. The staining pattern of nephr in was compared to that of ZO-1, a component of the cytoplasmic face of the slit diaphragm. The distributions of these two proteins in capillary tufts were similar in all disease entities studied. In conclusion, immunohistoch emistry and in situ hybridization did not reveal major alterations in the e xpression of nephrin in proteinuric kidney diseases in children. Further st udies are needed for more precise evaluation of the role of nephrin in thes e diseases.