Discussion
Our study suggested that IL-10 has an effective dose range on Mφ phenotypes, and intramyocardial IL-10 treatment may trigger cardioprotective or unwanted effects post-MI in a dose-dependent manner.
Methods
Using RAW264.7 monocyte models, we examined whether administering differential doses of exogenous IL-10 (0-1,000 ng/mL) perturbs classic M1 (pro-inflammatory) and M2 (anti-inflammatory) phenotypes of polarized Mφ or even alters the phenotypic transition of prospective M1 and M2 polarization. We then investigated the impact of single intramyocardial IL-10 administration on cardiac function, structure, and inflammation post-MI, using a mouse MI model.
Results
Compared with 0-ng/mL control, 250-ng/mL IL-10 had the strongest overall effects in decreasing M1 and increasing M2 phenotypes on polarized Mφ while ≥500-ng/mL IL-10 dampened M1 polarization and augmented native IL-10 secretion more effectively than low doses in vitro. Echocardiography revealed that the 250-ng group had consistently higher contractile function and lower left ventricular (LV) dilatation than the saline control over 6 weeks while ≥1,000-ng groups exhibited transient lower LV ejection fraction at 5 days post-MI in vivo. Moreover, different doses of IL-10 differentially modulated myocardial gene expression, phagocytic cell infiltration at the infarct, LV fibrosis, and revascularization post-MI, with some, but not all, doses exerting beneficial effects.