Platelet microparticle delivered microRNA-Let-7a promotes the angiogenic switch

Abstract

Platelet microparticle (PMP)-induced angiogenesis plays a key role in tumour metastasis and has been proposed to contribute towards cardiovascular disease by enhancing atherosclerotic plaque vulnerability. However, the mechanisms underlying PMP induced angiogenesis are ill defined. Recent reports demonstrate that PMPs deliver micro-RNAs (miRNAs) to recipient cells, controlling gene expression. We therefore evaluated whether miRNA transfer was a key regulator of PMP-induced angiogenesis. Co-culturing PMPs with human umbilical vein endothelial cells (HUVEC) on extracellular matrix gel induced robust capillary like structure formation. PMP treatment altered the release of angiogenesis modulators from HUVEC, including significantly reducing production of anti-angiogenic thrombospondin-1 (THBS-1). Both functional responses were abrogated by treating PMPs with RNase, suggesting the transfer of PMP-derived RNA was a critical event. PMPs were an abundant source of miRNA Let-7a, which was transferred to HUVEC following co-incubation. Using luciferase reporter assays we have shown that Let-7a directly targets the 3'UTR of the THBS-1 mRNA. HUVEC transfection with a Let-7a anti-sense oligonucleotide reduced the ability of PMPs to inhibit THBS-1 release, and significantly decreased PMP induced in vitro angiogenesis. Antibody neutralisation of THBS-1 reversed the anti-angiogenic effect of let-7a inhibition in PMP treated HUVEC, highlighting Let-7a dependent translational repression of THBS-1 drives angiogenesis. Importantly, plasmid overexpression of Let-7a in HUVEC alone induced robust tubule formation on extracellular matrix gel. These data reveal a new role for Let-7a in promoting angiogenesis and show for the first time PMPs induced angiogenic responses occur through miRNA regulation of HUVEC.

The role of microvesicles and its active molecules in regulating cellular biology

“…Platelet‐derived microvesicles were incubated with human umbilical vein endothelial cells (HUVECs), internalized by HUVECs, and the carrying microRNA let‐7a was transferred to HUVECs. The active substance microRNA let‐7a can directly target the 3′ untranslated regions (3′UTRs) of THBS‐1 and inhibit the release of THBS‐1, affecting the angiogenesis response . In addition, PMV infiltration in solid tumours, the anchoring to tumour cells and the metastasis of microRNAs result in the gene suppression of tumour cells, which can inhibit the growth of primary tumours and affect the immune response, the angiogenesis of tumours and other cancer‐related processes.…”

The “Janus Face” of Platelets in Cancer

“…MVs also deliver angiogenic signals [27]: Transfer of miRNA let-7a or miR-27b in endothelial cells down-regulates the expression of the anti-angiogenic modulator thrombospondin-1, thus enhancing platelet-dependent endothelial tube formation [168,169].…”

The role of microvesicles containing microRNAs in vascular endothelial dysfunction

“…It has long been reported that miRNAs are a significant cargo contained by MVs . Advances in this field will contribute to a better understanding of the role of delivered miRNAs in pathology and enable them to be identified as therapeutic targets …”

“…These two kinds of miRNAs can inhibit migration and tube formation of HUVECs by targeting selectin‐P (SELP) and platelet‐derived growth factor receptor alpha (PDGFRα) to enhance vascular endothelial cell damage . Recently, a data showed for the first time that miR‐let‐7a delivered by PMV targeted the 3′ UTR of anti‐angiogenic thrombospondin‐1 (THBS‐1) mRNA and potently inhibited THBS‐1 protein synthesis to drive endothelial tubule formation in vitro …”

“…89 Recently, a data showed for the first time that miR-let-7a delivered by PMV targeted the 3′ UTR of anti-angiogenic thrombospondin-1 (THBS-1) mRNA and potently inhibited THBS-1 protein synthesis to drive endothelial tubule formation in vitro. 56 PMVs containing miR-223 have been shown to regulate genes in HUVEC, including two endogenous endothelial genes: FBXW7 and EFNA1. 82 In another experiment, platelet-secreted miR-223 via PMVs targeted endothelial cell insulin-like growth factor 1 receptor (IGF-1R) and thus promoted cell apoptosis induced by advanced glycation end products.…”