Inflammation induced-endothelial cells release angiogenesis associated-microRNAs into circulation by microparticles

Endothelial cells derived microRNAs can be detected in plasma and serum and there is evidence that inflammatory disease states may affect the levels of circulating microRNAs. However, there is no direct proof that inflammation induces endothelial cells to release microRNAs into circulation. This study aimed to explore whether inflammation could induce endothelial cells to release microRNAs into circulation and to investigate whether these released microRNAs derived from endothelial cells were transported in microparticles.

Microparticles were isolated from human atherosclerotic plaques with an active inflammatory phenotype and normal vascular tissue. Flow cytometry and real-time PCR were used to detect the levels of microparticles and microRNAs. Human umbilical vein endothelial cells (HUVEC) was treated with tumour necrosis factor a (TNF-α, 10 ng/ml) for 24 hours, and then HUVEC and the culture medium were respectively collected.

By comparing microparticles isolated from human atherosclerotic plaques with an active inflammatory phenotype (n = 9) and those from normal vascular tissues (n = 9), we found levels of annexin V(+) microparticles and annexin V(+) CD144(+) microparticles were significantly increased in plaques and angiogenesis associated microRNAs (106b, 25, 92a and 21) were also significantly increased in microparticles from plaques. After exposure to TNF-α at a concentration of 10 ng/ml (TNF-α group, n = 3) or DMEM (control group, n = 3) for 24 hours, counts of microparticles and expressions of microRNAs 106b, 25, 92a and 21 in microparticles isolated from medium significantly increased. However, there were no differences in the intracellular levels of microRNAs 25, 92a or 21 isolated from HUVEC between TNF-α group and control group, while microRNA 106b decreased in TNF-α group.

Inflammation could induce endothelial cells to release angiogenesis associated microRNAs into circulation, causing higher levels of circulating endothelial cells derived microRNAs in atherosclerosis.