IL-10 improves cardiac remodeling after myocardial infarction by stimulating M2 macrophage polarization and fibroblast activation

Inflammation resolution is important for scar formation following myocardial infarction (MI) and requires the coordinated actions of macrophages and fibroblasts. In this study, we hypothesized that exogenous interleukin-10 (IL-10), an anti-inflammatory cytokine, promotes post-MI repair through actions on these cardiac cell types. To test this hypothesis, C57BL/6J mice (male, 3- to 6-month old, n = 24/group) were treated with saline or IL-10 (50 μg/kg/day) by osmotic mini-pump infusion starting at day (d) 1 post-MI and sacrificed at d7 post-MI. IL-10 infusion doubled plasma IL-10 concentrations by d7 post-MI. Despite similar infarct areas and mortality rates, IL-10 treatment significantly decreased LV dilation (1.6-fold for end-systolic volume and 1.4-fold for end-diastolic volume) and improved ejection fraction 1.8-fold (both p < 0.05). IL-10 treatment attenuated inflammation at d7 post-MI, evidenced by decreased numbers of Mac-3-positive macrophages in the infarct (p < 0.05). LV macrophages isolated from d7 post-MI mice treated with IL-10 showed significantly elevated gene expression of M2 markers (Arg1, Ym1, and Tgfb1; all p < 0.05). We further performed RNA-seq analysis on post-MI cardiac macrophages and identified 410 significantly different genes (155 increased, 225 decreased by IL-10 treatment). By functional network analysis grouping, the majority of genes (133 out of 410) were part of the cellular assembly and repair functional group. Of these, hyaluronidase 3 (Hyal3) was the most important feature identified by p value. IL-10 treatment decreased Hyal3 by 28%, which reduced hyaluronan degradation and limited collagen deposition (all p < 0.05). In addition, in vivo IL-10 treatment increased fibroblast activation (proliferation, migration, and collagen production), an effect that was both directly and indirectly influenced by macrophage M2 polarization. Combined, our results indicate that in vivo infusion of IL-10 post-MI improves the LV microenvironment to dampen inflammation and facilitate cardiac wound healing.