Calcium Signaling in Macrophages During a Wound Response In Vivo

Macrophages are among the earliest responders to tissue injury and remain associated with the wound throughout the healing process. Calcium (Ca²⁺) signaling regulates many immune cell behaviors, yet its role in macrophage responses to injury in vivo remains poorly defined. Here, we used transgenic zebrafish (Danio rerio) and Danionella cerebrum lines that specifically express the genetically encoded Ca²⁺ indicator, GCaMP, in macrophages. Live confocal imaging was used to monitor macrophage Ca²⁺ dynamics during the early wound response. We found that injury triggers macrophage recruitment to the wound site, where cells exhibit robust and repetitive intracellular Ca²⁺ transients that persist for several hours. Pharmacological perturbation revealed that endoplasmic reticulum Ca²⁺ stores contribute to sustaining these transients, while additional Ca²⁺ sources likely participate in macrophage Ca²⁺ signaling in vivo. Functionally, these Ca²⁺ transients do not appear to be required for chemotaxis, phagocytosis, or TNFα activation during the early stages of wound healing. Together, these findings uncover a previously uncharacterized macrophage Ca²⁺ signaling behavior and highlight the complexity of Ca²⁺ regulation during tissue injury responses in vivo.