Abstract
Background
After activation by different factors, platelets can release a large number of platelet microparticles (PMPs), and continue to play a more durable and extensive role in promoting inflammation and thrombosis. Previous studies by our group have shown that PMPs can promote endothelial cell migration and lumen formation in vitro, and promote the release of inflammatory factors from monocytes. However, it is unclear whether PMPs can promote angiogenesis in the plaque and promote vascular wall inflammation and further lead to plaque instability.
Purpose
To investigate the effect of platelet microparticles (PMPs) from C57BL/6 mice on promoting atherosclerotic plaque formation and plaque stability in ApoE−/− mice.
Methods
Forty male apolipoprotein E knockout (ApoE−/−) mice, aged 8 weeks and fed for 4 weeks with high-fat diet, were randomly divided into four groups (n=10 in each group)according to the table of random digit. The mice were respectively injected with PBS (PBS group), PMPs-free supernatants (SUP group), low-dose PMPs (LDP group) and high-dose PMPs (HDP group) once a week through tail vein injection for 8 weeks. At the end of the experiment, the mice were euthanized and the blood samples were collected to detect blood routine, blood lipids, liver and kidney function and inflammatory factors including CRP, IL-1β, TNF-α; The aorta and brachiocephalic trunk were sampled to detect the atherosclerotic plaque formation. Oil Red O staining, H&E staining, Masson staining and immunohistochemistry (CD68, MMP-9, α-SMA) were used to examine the stability of the atherosclerotic plaque in each group.
Results
There were no significant differences in body weight, blood routine (WBC, RBC, PLT, HGB), blood lipids (TG, TCH, LDL, HDL), liver (ALT, AST)and kidney function (UN, Cr)in each group. The levels of serum CRP, IL-1β and TNF-α in LDP group and HDP group were significantly higher than those in PBS group and SUP group (P<0.05). The total area of aortic atherosclerotic plaques in LDP group and HDP group were significantly greater than those in PBS group and SUP group (P<0.05). Compared with the PBS group, the lipid cores of the plaques in the other three groups were significantly increased (P<0.05). The content of collagen and the amount of smooth muscle cells in the plaques were significantly lower in HDP group than in PBS group (P<0.05), while macrophages increased significantly in HDP group (P<0.05).
Conclusion
PMPs promote the formation of atherosclerotic plaques in high-fat-fed ApoE−/− mice, as well as macrophage infiltration and inflammation in the plaques, reduce the content of collagen and the amount of smooth muscle cells, thus decreasing the stability of plaques.
Extracellular vesicles from monocyte/platelet aggregates modulate human atherosclerotic plaque responses
