Abstract 298: Microparticles Isolated from Human Atherosclerotic Plaques Stimulate Endothelial Cells Proliferation: Contribution of CD40 Ligand.
Background : Human atherosclerotic plaques contain microparticles (MPs), which are submicron membranes vesicles released from different cell types following activation or apoptosis. Human plaque MPs mainly derive from leukocytes and erythrocytes, but also from smooth muscle and endothelial cells. We investigated the effect of MPs isolated from human atherosclerotic plaques on human endothelial cells proliferation and the possible contribution of CD40 ligand.
Methods and Results : MPs were isolated by sequential centrifugations from human atherosclerotic plaques (758±100mg) surgically obtained from patients undergoing endarterectomy (n=26; 74±2 yrs-old; 81% male). MPs were characterized by phosphatidylserine exposure and specific cell markers using flow cytometry analysis. MPs abundance and cellular origin were not different between asymptomatic and symptomatic patients (n=13 each; p>0.05). However, plaque from symptomatic patients expressed more CD40Ligand+MPs than those from asymptomatic patients (126± 26 vs. 67± 28 CD40L+MPs/μg, respectively; n=13 each ; p=0.05). Endothelial cell proliferation (evaluated by 3H-thymidine incorporation in subconfluent quiescent HUVECs) was increased following exposure to increasing concentrations of plaque MPs for 24 hrs. The maximal 3H-thymidine incorporation induced by plaque MPs was comparable to that evoked by 10 % fetal calf serum (p=0.443 ; n=8). The proliferative effect was greater for MPs obtained from symptomatic than asymptomatic patients (110± 9% vs. 70± 12% of fetal calf serum, n=4 each; p=0.02). Exposure of plaque MPs to an anti-CD40Ligand neutralizing antibody decreased by 33± 10% MPs-induced 3H-thymidine incorporation by endothelial cells (n=6).
Conclusion : This study demonstrates for the first time that MPs isolated from human atherosclerotic plaques stimulate endothelial cell proliferation in part by a CD40 ligand-dependent mechanism. This effect, which is more potent for MPs isolated from symptomatic than asymptomatic patients, could be an important determinant of atherosclerotic plaque vascularisation and progression.