Exosomes and the Cargo microRNAs in Ischemic Heart Disease

Background: To cure ischemic diseases, angiogenesis needs to be improved by various strategies in
ischemic area. Considering that microRNA-132 (miR-132) regulates endothelial cell behavior during
angiogenesis and the safe and efficacious delivery of microRNAs in vivo is rarely achieved, an ideal
vehicle for miR-132 delivery could bring the promise for ischemic diseases. As a natural carrier of
biological molecules, exosomes are more and more developed as an ideal vehicle for miRNA transfer.
Meanwhile, mesenchymal stem cells could release large amounts of exosomes. Thus, this study
aimed to investigate whether MSC-derived exosomes can be used for miR-132 delivery in the
treatment of myocardial ischemia.
Methods: MSC-derived exosomes were electroporated with miR-132 mimics and inhibitors. After
electroporation, miR-132 exosomes were labelled with DiI and added to HUVECs. Internalization of
DiI-labelled exosomes was examined by fluorescent microscopy. Expression levels of miR-132 in
exosomes and HUVECs were quantified by real-time PCR. The mRNA levels of miR-132 target gene
RASA1 in HUVECs were quantified by real-time PCR. Luciferase reporter assay was performed to
examine the targeting relationship between miR-132 and RASA1. The effects of miR-132 exosomes
on the angiogenic ability of endothelial cells were evaluated by tube formation assay. Matrigel plug
assay and myocardial infarction model were used to determine whether miR-132 exosomes can
promote angiogenesis in vivo.
Results: miR-132 mimics were effectively electroporated and highly detected in MSC-derived
exosomes. The expression level of miR-132 was high in HUVECs preincubated with miR-132 mimicelectroporated
exosomes and low in HUVECs preincubated with miR-132 inhibitor-electroporated
exosomes. The expression level of RASA1, miR-132 target gene, was reversely correlated with miR-
132 expression in HUVECs pretreated with exosomes. Luciferase reporter assay further confirmed
that RASA1 was a direct target of miR-132. Exosomes loaded with miR-132, as a vehicle for miRNA
transfer, significantly increased tube formation of endothelial cells. Moreover, subcutaneous injection
of HUVECs pretreated with miR-132 exosomes in nude mice significantly increased their
angiogenesis capacity in vivo. In addition, transplantation of miR-132 exosomes in the ischemic
hearts of mice markedly enhanced the neovascularization in the peri-infarct zone and preserved heart
functions.
Conclusions: The findings suggest that the export of miR-132 via MSC-derived exosomes
represents a novel strategy to enhance angiogenesis in ischemic diseases.