Immune-inflammatory dysregulation modulates the incidence of progressive fibrosis and diastolic stiffness in the aging heart

► Immune dysregulation causes myocardial fibrosis and diastolic dysfunction in aging mice. ► Diastolic dysfunction is associated with an increased infiltration of CD45+ fibroblasts. ► Progressive fibrosis is accompanied by elevated mRNA level for MCP-1 and IL-13. ► In vitro studies demonstrate that IL-13 enhances monocyte to fibroblast transformation.