Glomerular endothelial cells promote mesangial cell growth via a PDGF-Like substance.

We conducted these experiments to determine whether glomerular endothelial cells (GEN) may play a role in the regulation of glomerular mesangial cells (GMC) growth. When GMC were separately co-cultured with GEN for 24 h, [3H]thymidine incorporation into GMC increased by 22%. In addition, when GMC were co-cultured with GEN for 4 days, the GMC count increased statistically. Conditioned medium (CM) was obtained from confluent GEN monolayers and tested for its effect on GMC growth. When CM was mixed with RPMI 1640 medium containing fetal calf serum (final concentration: 10%), GMC growth was potentiated in a dose-dependent manner. This stimulatory effect of CM from GEN cultures was inhibited by the addition of anti-human platelet-derived growth factor (PDGF) antibody. However, antibodies against interleukin 1-beta, tumor necrosis factor-alpha and endothelin-1 did not affect the stimulatory effect of CM. Moreover, the modulator contained in CM was stable at 100 degrees C, and pH 2.5 at 22 degrees C for 30 min. When treated with 2 mM mercaptoethanol, this activity was almost completely lost. These findings suggest that GEN promote GMC growth in co-culture systems, without direct contact, by means of a PDGF-like substance.