MicroRNA-146a sponge therapy suppresses neointimal formation in rat vein grafts

MicroRNA regulation of phenotypic transformations in vascular smooth muscle: relevance to vascular remodeling

Alterations in the vascular smooth muscle cells (VSMC) phenotype play a critical role in the pathogenesis of several cardiovascular diseases, including hypertension, atherosclerosis, and restenosis after angioplasty. MicroRNAs (miRNAs) are a class of endogenous noncoding RNAs (approximately 19-25 nucleotides in length) that function as regulators in various physiological and pathophysiological events. Recent studies have suggested that aberrant miRNAs' expression might underlie VSMC phenotypic transformation, appearing to regulate the phenotypic transformations of VSMCs by targeting specific genes that either participate in the maintenance of the contractile phenotype or contribute to the transformation to alternate phenotypes, and affecting atherosclerosis, hypertension, and coronary artery disease by altering VSMC proliferation, migration, differentiation, inflammation, calcification, oxidative stress, and apoptosis, suggesting an important regulatory role in vascular remodeling for maintaining vascular homeostasis. This review outlines recent progress in the discovery of miRNAs and elucidation of their mechanisms of action and functions in VSMC phenotypic regulation. Importantly, as the literature supports roles for miRNAs in modulating vascular remodeling and for maintaining vascular homeostasis, this area of research will likely provide new insights into clinical diagnosis and prognosis and ultimately facilitate the identification of novel therapeutic targets.

Defective autophagy triggered by arterial cyclic stretch promotes neointimal hyperplasia in vein grafts via the p62/nrf2/slc7a11 signaling pathway

Autophagy is an adaptation mechanism to keep cellular homeostasis, and its deregulation is implicated in various cardiovascular diseases. After vein grafting, hemodynamic factors play crucial roles in neointimal hyperplasia, but the mechanisms are poorly understood. Here, we investigated the impacts of arterial cyclic stretch on autophagy of venous smooth muscle cells (SMCs) and its role in neointima formation after vein grafting. Rat jugular vein graft were generated via the 'cuff' technique. Autophagic flux in venous SMCs is impaired in 3-day, 1-week and 2-week grafted veins. 10%-1.25 Hz cyclic stretch (arterial stretch) loaded with FX5000 stretch system on venous SMCs blocks cellular autophagic flux in vitro and shows no significant impact on activity of mTORC1 and AMPK. Microtubule depolymerization but not lysosome dysfunction nor autophagosome/amphisome-lysosomal membrane fusion blockade is involved in the impairment of autophagic flux. Microtubule stabilization, induced by paclitaxel treatment and external stents intervention respectively, restores venous SMC autophagy and ameliorates neointimal hyperplasia in vivo. Moreover, autophagy impairment causes accumulation of the cargo receptor p62, which sequesters keap1 to p62 aggregates and results in the stabilization and nuclear translocation of nrf2 to modulate its target antioxidative gene SLC7A11. p62 silencing abrogates the increases of nrf2 and slc7a11 protein expression, glutathione level and venous SMC proliferation triggered by arterial cyclic stretch in vitro, and further hinders nrf2 nuclear translocation, reduces neointimal thickness after vein grafting in vivo. p62 (T349A) mutation also inhibited venous SMC proliferation and alleviated neointimal formation in vivo. These findings suggest that stabilization of microtubules to rescue autophagic flux or direct silencing of p62 are potential therapeutic strategies for neointimal hyperplasia.

Systemic single administration of anti-inflammatory microRNA 146a-5p loaded in polymeric nanomedicines with active targetability attenuates neointimal hyperplasia by controlling inflammation in injured arteries in a rat model

Neointimal hyperplasia (NIH) after revascularization is a key unsolved clinical problem. Various studies have shown that attenuation of the acute inflammatory response on the vascular wall can prevent NIH. MicroRNA146a-5p (miR146a-5p) has been reported to show anti-inflammatory effects by inhibiting the NF-κB pathway, a well-known key player of inflammation of the vascular wall. Here, a nanomedicine, which can reach the vascular injury site, based on polymeric micelles was applied to deliver miR146a-5p in a rat carotid artery balloon injury model. In vitro studies using inflammation-induced vascular smooth muscle cell (VSMC) was performed. Results showed anti-inflammatory response as an inhibitor of the NF-κB pathway and VSMC migration, suppression of reactive oxygen species production, and proinflammatory cytokine gene expression in VSMCs. A single systemic administration of miR146a-5p attenuated NIH and vessel remodeling in a carotid artery balloon injury model in both male and female rats in vivo. MiR146a-5p reduced proinflammatory cytokine gene expression in injured arteries and monocyte/macrophage infiltration into the vascular wall. Therefore, miR146a-5p delivery to the injury site demonstrated therapeutic potential against NIH after revascularization.

MicroRNA-92a -mediated endothelial to mesenchymal transition controls vein graft neointimal lesion formation

PURPOSE

Long-term failure of vein grafts due to neointimal hyperplasia remains an important problem in coronary artery bypass graft surgery. Endothelial to mesenchymal transition (EndMT) contributes to vein graft vascular remodeling. However, there is little study on microRNA-mediated EndMT contributions to neointimal formation in vein graft. We hypothesized that microRNA-92a (miR-92a) might play an important role in determining EndMT contributions to neointimal formation.

METHODS

miR-92a and EndMT-related proteins detected by qRT-PCR and Western blot in vitro and in vivo. Adeno-associated virus 6 (AAV6) delivery gene therapy was used to inhibit neointimal formation in vivo. The intimal hyperplasia of vein grafts was measured by HE staining, the expression of EndMT-related protein in vein grafts was measured by immunofluorescence. Immunohistochemistry and luciferase assay were used to detect potential targets of miR-92a.

RESULTS

The expression of miR-92a was found to be upregulated in neointimal hyperplasic lesions after vein grafting. Using cultured human umbilical vein endothelial cells (HUVECs), we show that TGF-β1 treatment of HUVECs significantly increased miR-92a expression and induced EndMT, characterized by suppression of endothelial-specific markers (CD31 and VE-cadherin) and an increase in mesenchymal-specific markers (a-SMA and vimentin), while inhibition of miR-92a expression blunted EndMT in cultured HUVECs. Furthermore, AAV6 mediated miR-92a suppression gene therapy effectively resulted in decreased EndMT and less neointimal formation in vein grafts in vivo. We further identified that integrin alpha 5 (ITGA5) is a potential target gene involved in the development of neointima formation in these vein grafts.

CONCLUSION

This data suggests that neointimal formation does not solely rely on vascular smooth muscle cell phenotypic switching but is also related to EndMT, and miR-92a-mediated EndMT is an important mechanism underlying neointimal formation in vein grafts.