Electron microscopy shows foot process effacement and focal mesangial cell interposition, and mesangiolysis may be present (54). Endothelial cell "dedifferentiation" is often evident, as manifested by a loss of the normal fenestrations (55,56). Loss of this normal differentiated structure of glo-merular endothelial cells should markedly restrict bulk water flow through the capillary wall and decrease filtration. The other diseases with similar
light and electron microscopic glomerular features also are characterized by endothelial injury (thrombotic microangiopathy, scleroderma, and eclampsia). A chronic lesion in the peritubular capillaries has been observed consisting of splitting and multilayered duplication of the basement membrane, analogous to and correlated with the chronic glomerular changes (57). Thus, the common theme in chronic rejection is endothelial damage at the level of the arteries, glomeruli, and peritubular capillaries.
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