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Interconnected cells are responsible for emergent functions ranging from cognition in the brain to cyclic contraction in the heart. In electrically excitable cells, methods for studying cell communication are highly advanced, but in non-excitable cells, generalized methods for studying cell communication are less mature. Immune cells have generally been classified as non-excitable cells with diverse pathophysiologic roles that span every tissue in the body, yet little is known about their interconnectedness because assays are destructive and have low temporal resolution. In this work, we hypothesize that non-excitable immune cells are functionally interconnected in previously unrecognized cell communication networks. To test the hypothesis, we created a hematopoietic calcium reporter mouse (Csf1r-Cre × GCaMP5) and non-destructively quantified the spatiotemporal dynamics of intracellular calcium in vitro and in vivo. In vitro, bone marrow derived macrophages calcium reporters reveal that fatal immune stimulatory DNA-sensing induces rapid intercellular communication to neighboring cells. In vivo, using intravital microscopy through a dorsal window chamber in the context of MC38-H2B-mCherry tumors, Csf1r-GCaMP5 reporters exhibit spatiotemporal dynamics consistent with cell communication. We present a theoretical framework and analysis pipeline for identifying spatiotemporal locations of “excess synchrony” of calcium spiking as a means of inferring previously unrecognized cell communication events. Together, these methods provide a toolkit for investigating known and as-yet-undiscovered cell communication events in vitro and in vivo.

Sterile tissue injury recruits myeloid cells (neutrophils and monocytes) from the bone marrow by stimulating a process known as emergency myelopoiesis. It is commonly assumed that myeloid cells activate proinflammatory signaling pathways within the injured tissue after sensing innate immune-activating molecules in the local microenvironment. Here, we show that pathogenic innate immune signaling in myeloid cells begins far from the site of injury, at their origins in the bone marrow. Using myocardial infarction (MI) as a model of sterile injury, we profiled single cell transcriptomes of >50,000 myeloid cells and found evidence of type I interferon signaling characterized by expression of interferon stimulated genes (ISGs) in a subset of neutrophils and monocytes in the heart, blood, and bone marrow after MI. We validated the findings in humans by quantifying ISG-expression in myeloid cells of patients presenting with acute MI, which revealed ISG levels far exceed that of healthy subjects and are comparable to patients with the interferon-associated autoimmune disease, systemic lupus erythematous. The identification of remote innate immune education raises important questions about how distant tissue injury activates interferon signaling in the hematopoietic compartment. Clinically, our data provide a strategy for quantifying pathogenic subsets of emergency myelopoietic cells in the blood as a biomarker that may identify patients who have disproportionately worse outcomes or who may benefit from immune modulatory therapy after acute MI.