Figure 7. miR-155 antagonist reduces myocardial inflammation during CVB3-induced VM.

C57BL/6 miR-155^+/+ WT male mice received 1 × 10⁵ PFU of CVB3 i.p. on day 0. For in vivo anti–miR-155 treatment, 30 μl lipofectamine 2000 was mixed with miR-155 antagonist or scrambled control (25μg/mouse) dissolved in 170 μl PBS, and the liposome complexes were administered i.v. to mice 3 days prior to CVB3 infection. (A) miR-155 expression in hearts was determined by real-time PCR. (B) Heart sections were stained with H&E on day 7 (Scale bar = 100 μm). The parameters of the viral myocarditis were evaluated including heart weight (C), loss of body weight (D), activity of CK-MB and levels of cTnI (E) on day 7 post-infection. (F) The survival rate of mice was observed until day 10 post-infection. (G) Viral titers were measured using plaque assay. (H) Myocardial infiltrating leukocytes were isolated from the hearts after enzymatic digestion. Activated CD4⁺ T cells were determined by surface CD62L^low expression. (I) 5-bromo-2-deoxyuridine (BrdU) was administered (0.8mg in 1ml PBS) 1 day before termination of mice. The proliferation of CD4⁺ T cells was determined by BrdU incorporation assay in vivo. (J) The proportion of CD4⁺CD25⁺Foxp3⁺ Tregs was analyzed by FACS. Experiments were repeated three times in triplicate with 10 mice per group. Bar graph data are presented as mean ± SD; *P < 0.05, **P < 0.01 and ***P < 0.001 as compared with scrambled control.