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Inhibition of mesangial cell proliferation by platelet factor 4
J L Barnes1, K A Woodruff, S P Levine
1Department of Medicine, University of Texas Health Science Center, San Antonio 78284-7882, USA.
Abstract:
Platelet factor 4(PF4), an abundant platelet secretory product, is a strong candidate for modulating glomerular pathology. Because PF4 might be released from platelets and influence intrinsic cell growth during glomerular injury, the effect of PF4 on fetal calf serum- and platelet-derived growth factor (PDGF)-induced mesangial cell mitogenesis was examined. Mitogenesis was measured as the amount of 3H-thymidine incorporated into acid-precipitable material as well as by autoradiography. The effect of PF4 on mesangial cell expression of mRNA for PDGF A chain and transforming growth factor-beta (TGF-beta 1) was also examined. Fetal calf serum (10%)- and PDGF (10 ng/mL)-stimulated increases in mesangial cell 3H-thymidine incorporation were inhibited by incremental concentrations of PF4 (1 to 25 micrograms/mL) showing a maximum reduction of approximately 80% at 25 micrograms/mL of PF4. PF4 was effective when added 24 h before and 1, 4, and 8 h, but not 16 h after the addition of PDGF, indicating that inhibition occurred at delayed events in cell-cycle regulation. PF4 inhibited PDGF-induced increments in mRNA encoding PDGF A chain and TGF-beta 1. Also, PF4 did not interfere with PDGF receptor binding. The results of this study show that PF4 is a negative regulator of mesangial cell proliferation and suggest an interference in cell growth by pathways associated with modulation of the autocrine growth factors PDGF and TGF-beta 1.
Insights
Platelet factor 4 (PF4) inhibits mesangial cell proliferation by reducing growth factor signaling. This finding suggests PF4 plays a role in regulating kidney cell growth during injury.
Area of Science:
- Nephrology
- Cell Biology
- Molecular Biology
Background:
- Platelet factor 4 (PF4) is a platelet protein with potential roles in glomerular pathology.
- Glomerular injury involves mesangial cell proliferation, influenced by growth factors like PDGF.
Purpose of the Study:
- To investigate the effect of PF4 on fetal calf serum- and platelet-derived growth factor (PDGF)-induced mesangial cell proliferation.
- To examine PF4's impact on PDGF A chain and TGF-beta 1 mRNA expression in mesangial cells.
Main Methods:
- Mesangial cell mitogenesis was assessed via 3H-thymidine incorporation and autoradiography.
- mRNA expression levels for PDGF A chain and TGF-beta 1 were analyzed.
- PF4's effect on PDGF receptor binding was evaluated.
Main Results:
- PF4 significantly inhibited PDGF- and fetal calf serum-stimulated mesangial cell proliferation in a dose-dependent manner (up to 80% reduction).
- PF4's inhibitory effect was observed when added up to 8 hours after PDGF, indicating interference with later cell-cycle events.
- PF4 reduced PDGF A chain and TGF-beta 1 mRNA levels without affecting PDGF receptor binding.
Conclusions:
- PF4 acts as a negative regulator of mesangial cell proliferation.
- PF4 may modulate glomerular cell growth by influencing autocrine growth factor pathways, specifically PDGF and TGF-beta 1.