Portions of basement membrane with decreased negative charge in various glomerulonephritis

The decrease in negative charge was evaluated in different portions of the basement membrane as well as the lamina rara externa (LRE) and lamina rara interna (LRI). The subjects were nine patients [2 patients with focal segmental glomerulosclerosis (FGS), 2 with membranoproliferative glomerulonephritis (MPGN), 3 with IgA nephropathy, and 2 with Henoch-Schoenlein purpura nephritis (HSPN)] and 2 patients with minor glomerular abnormalities and 1 with tubulo-interstitial nephritis (TIN) as controls. Polyethyleneimine (PEI) was used as a cationic probe. The basement membrane was divided into the peripheral portion (loop basement membrane 7 microns or more from the anchor portion), proximal portion (within 3 microns of the anchor portion), and the paramesangial portion in the paramesangial basement membrane. In each portion, PEI granules per 1 micron of the LRE and LRI were counted. Anionic sites were decreased in the patients with FGS and MPGN, but the damage pattern differed between the two diseases. In the patients with FGS, the decrease in anionic sites was most marked in the peripheral portion with an even greater decrease in the LRI. In the patients with MPGN, the decrease was uniform among the portions. On the other hand, no significant difference was observed in any portion between the patients with IgA nephropathy or HSPN and the controls. The portions with decreased negative charge varied among various glomerular diseases, suggesting different developmental mechanisms.