Background: CD4+ cells are implicated in the healing process after myocardial infarction (MI). We sought to investigate the role of interleukin-23 (IL-23) deficiency, a cytokine important in differentiation of CD4+ cells, in scar formation of the ischemic heart.
Methods and results: MI was performed in wild-type and IL23p19-/- mice. Thirty-day mortality, hemodynamic function 4 days after MI and myocardial inflammation, and remodeling 4 and 30 days after MI were examined. Differentiation of fibroblasts from infarcted and noninfarcted hearts into myofibroblasts was examined under basal conditions and after stimulation with interferon-γ, IL-17α and IL-23. Interleukin-23p19-/- mice showed higher expression of proinflammatory cytokines and immune cell infiltration in the scar early after MI compared with wild-type mice. A stronger interferon-γ/Th1 reaction seemed to be responsible for the increased inflammation under IL-23 deficiency. Expression of α-smooth muscle actin (α-SMA), collagen I and III was significantly higher in the heart tissue and isolated cardiac fibroblasts 4 days after MI in the wild-type mice. Interleukin-23p19-/- mice showed impaired healing compared with wild-type mice, as seen by significantly higher mortality because of ventricular rupture (40% higher after 30 days) and stronger left ventricular dilation early after MI. Stimulation of cardiac fibroblasts with interferon-γ, the main Th1 cytokine, but not with IL-23 or IL-17α, led to a significant downregulation of α-smooth muscle actin, collagen I and III and decreased migration and differentiation to myofibroblasts.
Conclusions: IL-23 deficiency leads to increased myocardial inflammation and decreased cardiac fibroblast activation, associated with impaired scar formation and adverse remodeling after MI.
Keywords: fibroblasts; interleukin-23; left ventricular remodeling; myocardial infarction.