Minimally invasive myocardial infarction model recapitulates patient immune responses and reveals a pathogenic role for immature neutrophils

Myocardial infarction (MI) triggers a systemic neutrophil response, yet the roles of distinct neutrophil subsets in cardiac remodeling remain unclear. Studying this requires murine models that accurately mirror human neutrophil dynamics. Here, we show that a minimally invasive intact-chest MI model is more pathophysiologically relevant than the standard open-chest approach for investigating post-MI immune responses. In the open-chest model, surgical trauma disrupts bone marrow homeostasis, releases large numbers of immature neutrophils, and masks MI-specific immune mechanisms. In contrast, the intact-chest model preserves bone marrow integrity and induces only a modest rise in circulating immature neutrophils, closely reflecting MI patient profiles. We further demonstrate that accumulation of immature neutrophils in the infarcted heart exacerbates cardiac dysfunction. Beyond neutrophils, the overall cardiac immune landscape differs markedly between both models. Collectively, our findings establish the intact-chest model as superior for studying post-MI inflammation and reveal immature neutrophils as mediators of adverse cardiac remodeling.