MicroRNAs are emerging as key players in the regulation of the post-myocardial infarction (MI) environment. We previously identified that matrix-treated hearts had down-regulated expression of miR-92a, a miRNA with inflammatory and migratory effects that is normally up-regulated after MI. We have shown that type I collagen matrix treatment at 3h post-MI leads to less inflammation and improved cardiac function, but the underlying mechanisms remain to be better characterized. The goal of this study was to elucidate a possible role of miR-92a in the anti-inflammatory/pro-wound healing effect of matrix treatment post-MI. C57BL/6J mice underwent LAD ligation to induce MI. Hearts were removed at 4h, 1d, 3d, and 7d post-MI and RNA was extracted from infarct and peri-infarct tissue. PCR analysis revealed that hearts injected with matrix at 3h post-MI resulted in significantly decreased miR-92a at 4h, 1d, and 3d compared to non-injected animals at each time point (p<0.0001) and PBS injected animals at 4h and 7d (p<0.004). Several targets of miR-92a and regulators of macrophage polarization were found to be up-regulated (p<0.05) early in MI indicating early amelioration of inflammatory processes. In vitro, macrophages cultured on matrix also had decreased expression of miR-92a compared to cultures on tissue culture poly styrene (TCPS) (p<0.001). Integrins α5 (ITGAα5) and αV (ITGAαV), involved in cell-matrix interactions, as well as inflammatory regulators S1PR1 and SIRT1 were identified as putative miR-92a targets. When miR-92a is over-expressed in macrophages, ITGα5 (p=0.0002), ITGαV (p=0.02), and S1Pr1 (p<0.0001), and SIRT1 (p=0.03) all had decreased expression. STAT3 and IL-10 were found to be moderately down-regulated. In evaluating macrophage phenotypes, M2 macrophages had reduced miR-92a expression on matrix compared to M1 macrophages. The migration of M2 macrophages into the matrix is increased compared to M1 macrophages. We report that the beneficial effects of matrix treatment post-MI may be mediated, at least in part, through its ability to regulate miR-92a and pro-wound healing mechanisms in macrophages. These results present the matrix as a novel non-pharmacological approach to locally regulate miRNAs in vivo for reducing inflammation and protecting the myocardium post-MI.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/35561 |
| Date | January 2016 |
| Creators | Lister, Zachary |
| Contributors | Suuronen, Erik, Rayner, Katey |
| Publisher | Université d'Ottawa / University of Ottawa |
| Source Sets | Université d’Ottawa |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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