In a mouse model of myocardial infarction, mir-155 deficiency significantly reduced the incidence of cardiac rupture and improved cardiac function compared with wild-type mice.
Does mir-155 deficiency or inhibition reduce cardiac rupture and improve cardiac function following myocardial infarction in a mouse model?
Macrophage-derived mir-155 acts as a paracrine regulator that promotes inflammation and suppresses fibroblast proliferation, suggesting mir-155 inhibition as a potential therapeutic target to reduce adverse events after acute myocardial infarction.
Inflammation plays an important role in cardiac injuries. Here, we examined the role of miRNA in regulating inflammation and cardiac injury during myocardial infarction. We showed that mir-155 expression was increased in the mouse heart after myocardial infarction. Upregulated mir-155 was primarily presented in macrophages and cardiac fibroblasts of injured hearts, while pri-mir-155 was only expressed in macrophages. mir-155 was also presented in exosomes derived from macrophages, and it can be transferred into cardiac fibroblasts by macrophage-derived exosomes. A mir-155 mimic or mir-155 containing exosomes inhibited cardiac fibroblast proliferation by downregulating Son of Sevenless 1 expression and promoted inflammation by decreasing Suppressor of Cytokine Signaling 1 expression. These effects were reversed by the addition of a mir-155 inhibitor. In vivo, mir-155-deficient mice showed a significant reduction of the incidence of cardiac rupture and an improved cardiac function compared with wild-type mice. Moreover, transfusion of wild-type macrophage exosomes to mir-155 −/− mice exacerbated cardiac rupture. Finally, the mir-155-deficient mice exhibited elevated fibroblast proliferation and collagen production, along with reduced cardiac inflammation in injured heart. Taken together, our results demonstrate that activated macrophages secrete mir-155-enriched exosomes and identify macrophage-derived mir-155 as a paracrine regulator for fibroblast proliferation and inflammation; thus, a mir-155 inhibitor (i.e., mir-155 antagomir) has the potential to be a therapeutic agent for reducing acute myocardial-infarction-related adverse events.
Wang et al. (Sun,) conducted a other in Myocardial infarction. mir-155 deficiency vs. Wild-type mice was evaluated on Incidence of cardiac rupture and cardiac function. In a mouse model of myocardial infarction, mir-155 deficiency significantly reduced the incidence of cardiac rupture and improved cardiac function compared with wild-type mice.