TUFT-TO-CAPSULE ADHESIONS AND THEIR PRECURSORS - DIFFERENCES BETWEEN THE VASCULAR AND TUBULAR POLES OF THE HUMAN GLOMERULUS

Human glomerular capillary tufts were removed by microdissection and s canning electron microscopy was used to examine the surface of the cap illary tuft and the interior of its Bowman's capsule in order to ident ify connections between the tuft and capsule. Glomeruli were examined in histologically normal rend cortex from 12 kidneys removed for tumou r and 12 renal allografts removed for end-stage rejection. In normal k idney, the glomerular tuft was connected to Bowman's capsule by single podocytes and their processes. At the vascular pole, these were predo minantly associated with parietal podocytes which lined Bowman's capsu le. At the tubular pole, occasional podocytic processes derived from t he capillary tuft bridged Bowman's space and connected to Bowman's cap sule where there were no parietal podocytes. These podocytic connectio ns were also found in all rejected transplants, but in addition adhesi ons were identified which consisted of thicker connections between the tuft and capsule. At the vascular pole, tuft-to-capsule adhesions wer e found in all 12 kidneys; these were always associated with parietal podocytes. Tubular pole adhesions were identified in ten of the 12 tra nsplants. They were associated with abnormal squamous cells, but not w ith parietal podocytes. When the capillary tuft herniated into the pro ximal tubule, the tufts sometimes formed an adhesion with the origin o f the proximal tubule. These observations suggest that podocyte connec tions between the glomerular tuft and Bowman's capsule may be precurso rs of glomerular adhesions at the vascular pole. Since tuft-to-capsule adhesions at the vascular pole differ morphologically from those at t he tubular pole, this may reflect different pathogenetic mechanisms at the opposite poles of the glomerulus. (C) 1998 John Wiley & Sons, Ltd .