MMP9^High Neutrophils are Critical Mediators of Neutrophil Extracellular Traps Formation and Myocardial Ischemia/Reperfusion Injury

Neutrophil extracellular traps (NETs) are increasingly recognized as pivotal players and potential therapeutic targets in neutrophil-mediated reperfusion injury. Despite their importance, the effects and variability of circulating neutrophils in relation to NET formation during myocardial ischemia/reperfusion injury (MI/RI) remain inadequately characterized. In this study, single-cell transcriptomes of neutrophils isolated from the blood of healthy donors and MI/RI patients are analyzed. The results reveal that MI/RI neutrophils transition from a high IFIT1 expression profile into four distinct states, two of which exhibit elevated MMP9 transcription. These MMP9^High neutrophil subpopulations are instrumental in the NET formation and correlate positively with the severity of MI/RI. Further investigation identifies the transcription factor SPI1 as a key regulator of this transition, acting through modulation of CST7 expression. Targeting SPI1 or CST7 significantly reduces the prevalence of MMP9^High neutrophils and NET formation, resulting in improved MI/RI outcomes. These findings offer new insights into neutrophil heterogeneity and pinpoint a specific subset critical for NET formation, underscoring their potential as diagnostic biomarkers and therapeutic targets for MI/RI management.