After tissue injury, all macrophages (Ly6C+ inflammatory macrophages and CX3CR1+ tissue-resident macrophages) are activated and differentiate into M1-like inflammatory cells, and migrate into the wound site15, 16, 17, 18, 19, but the distinct role of macrophage subpopulations in HF stem cell activation is unclear. Here, CX3CR1 is linked to hydrops fetalis.