Effect of Endothelial Microparticles Induced by Hypoxia on Migration and Angiogenesis of Human Umbilical Vein Endothelial Cells by Delivering MicroRNA-19b.

Background: Microparticles (MPs) are small extracellular plasma membrane particles shed by activated and apoptotic cells, which are involved in the development of atherosclerosis. Our previous study found that microRNA (miR)-19b encapsulated within endothelial MPs (EMPs) may contribute to the upregulation of circulating miR-19b in unstable angina patients. Hypoxia is involved in atherosclerosis as a critical pathological stimulus. However, it still remains unclear whether the increase of miR-19b levels in EMPs is related to hypoxia and if the effect of miR-19b - wrapped within EMPs - stimulates hypoxia on vascular endothelial cells. This study aimed to explore the changes of miR-19b in EMPs induced by hypoxia as well as their effects on endothelial cells.

Methods: Human umbilical vein endothelial cells (HUVECs) were cultured in vitro and arranged to harvest EMPs in two parts: the first part consisted of EMP and EMP and the second part included EMP, EMP, and EMP. Cell migration was detected by scratch migration and transwell chamber migration. Angiogenesis was assessed by tube formation assays. Furthermore, we predicted the target gene of miR-19b by bioinformatics analysis, and luciferase assay was used to verify the targeted gene of miR-19b. Data were analyzed by one-way analysis of variance. Student's t-test was used when two groups were compared.

Results: Compared with EMP- and EMP-inhibited migration of cells by scratch migration assay (80.77 ± 1.10 vs. 28.37 ± 1.40, P < 0. 001) and transwell chamber migration assay (83.00 ± 3.46 vs. 235.00 ± 16.52, P < 0.01), the number of tube formations was markedly reduced by 70% in the EMP group (P < 0.001) in vitro analysis of HUVECs. Meanwhile, a strong inhibition of migration and tube formation of HUVECs in the presence of miR-19b-enriched EMP was observed. This effect might be due to the delivery of miR-19b in EMPs. Transforming growth factor-β2 (TGFβ2) was predicted to be one of the target genes of miR-19b, and we further confirmed that TGFβ2 was a direct target gene of miR-19b using the luciferase assay. The expression of TGFβ2 in HUVECs was inhibited by treatment with EMP and EMP.

Conclusions: MiR-19b in EMPs induced by hypoxia could reduce endothelial cell migration and angiogenesis by downregulating TGFβ2 expression, which may have inhibited the progression of atherosclerosis.