Glomerular endothelial cells secrete a heparinlike inhibitor and a peptide stimulator of mesangial cell proliferation.

The regulation of cell growth in the kidney glomerulus plays a key role in many physiologic and pathologic processes. In this communication the authors have examined the possible role of glomerular endothelial cells as potential regulators of mesangial cell proliferation. Conditioned medium was collected from confluent cultures of glomerular endothelial cells and tested for its effects on glomerular mesangial cell and vascular smooth muscle cell growth. When glomerular endothelial cell-conditioned medium was mixed 1:1 with normal growth medium, the growth of these two closely related cell types was inhibited by 60-70%. If the conditioned medium was diluted to 1:9, a stimulation of mesangial and smooth muscle cells growth was seen. Approximately 70% of the antiproliferative activity was destroyed by a highly purified heparinase; the other 30% was sensitive to trypsin. Approximately 90% of the mitogenic activity was protease-sensitive. These results suggest that glomerular endothelial cells may participate in part in mesangial cell growth regulation via a heparin-mediated mechanism.