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Glomerular endothelial cells promote mesangial cell growth via a PDGF-Like substance
Abstract:
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.
Insights
Glomerular endothelial cells (GEN) stimulate glomerular mesangial cells (GMC) growth via a heat-stable, PDGF-like substance. This interaction, observed in co-culture systems, suggests a novel mechanism in kidney cell regulation.
Area of Science:
- Nephrology
- Cell Biology
- Endocrinology
Background:
- Glomerular endothelial cells (GEN) and glomerular mesangial cells (GMC) are key components of the renal glomerulus.
- The regulatory interactions between these cell types are not fully understood.
- Understanding these interactions is crucial for comprehending kidney physiology and pathology.
Purpose of the Study:
- To investigate the role of GEN in regulating GMC proliferation.
- To identify potential factors secreted by GEN that influence GMC growth.
- To characterize the nature of the substance mediating GEN-GMC interactions.
Main Methods:
- Co-culture of GEN and GMC for 24 hours and 4 days.
- Measurement of [3H]thymidine incorporation and cell counts.
- Collection and testing of conditioned medium (CM) from GEN cultures on GMC growth.
- Inhibition studies using antibodies against various growth factors (PDGF, IL-1β, TNF-α, ET-1).
- Stability assays of the active substance in CM (heat, pH, reducing agent).
Main Results:
- Co-culture with GEN significantly increased GMC proliferation ([3H]thymidine incorporation by 22% and cell count).
- Conditioned medium from GEN cultures dose-dependently stimulated GMC growth.
- The stimulatory effect was inhibited by anti-PDGF antibodies but not by antibodies against IL-1β, TNF-α, or ET-1.
- The active substance in CM was heat-stable and acid-stable but inactivated by mercaptoethanol, suggesting a PDGF-like protein.
Conclusions:
- GEN promote GMC growth through paracrine signaling, independent of direct cell-cell contact.
- A PDGF-like substance secreted by GEN is responsible for stimulating GMC proliferation.
- This finding highlights a novel mechanism of intercellular communication in the glomerulus with implications for kidney health and disease.