Mapping neutrophil fate and function in ischemic stroke: A single-cell roadmap for translational insights

Ischemic stroke (IS) accounts for 71 % of all strokes, whose diagnosis and prognosis require further exploration. Neutrophil extracellular traps (NETs) are produced by neutrophils, and there is already evidence that NETs play a role in IS, but further studies about crosstalk between immune cells, pathways and NETs are still needed.

To assess the expression of neutrophil extracellular traps (NETs), we utilized single sample Gene Set Enrichment Analysis. Stroke-associated NETs genes (SN genes) were identified through differential expression analysis combined with Weighted Correlation Network Analysis. Based on these SN genes, we developed a sophisticated diagnostic model incorporating machine learning techniques. Furthermore, we constructed a single-cell atlas of neutrophil transitions in post-stroke mice. Validation of our findings was conducted both in vitro and in vivo. In vitro, we employed oxygen-glucose deprivation (OGD) experiments to simulate ischemic conditions, facilitating the assessment of NETs formation and monitoring alterations in SN genes expression within neutrophils. In vivo, validation involved tracking changes in peripheral blood levels of these genes in a mouse model of transient middle cerebral artery occlusion (tMCAO) post-cerebral ischemia.

A detailed single-cell landscape depicting the dynamic transitions of neutrophils within the cerebral microenvironment post-stroke has been elaborately constructed. NETs displayed significant differential expression between IS and control groups in peripheral blood, correlating strongly with the activities of neutrophils and macrophages. Pathways pertinent to IS and NETs were delineated. A diagnostic model incorporating two SN genes was developed, demonstrating an AUC greater than 0.98, effectively pinpointing the hyperacute phase of IS. Additionally, the ceRNA networks concerning IS and NETs were mapped out. In vitro validation with oxygen-glucose deprivation (OGD) experiments revealed marked changes in NET formation and SN genes expression in neutrophils, corroborating our computational predictions. In vivo validation using a mouse transient middle cerebral artery occlusion (tMCAO) model confirmed significant changes in peripheral blood levels of F12 and PLXDC2 after cerebral ischemia, proving the excellent predictive value of these markers for IS.

This study elucidates the complex roles and dynamic changes of neutrophils within the cerebral microenvironment of mice from 3 h to 3 days following stroke onset. We have identified key genes, immune cells, signaling pathways, and ceRNA networks implicated in the formation of NETs in IS. Our study constructed a robust diagnostic model capable of detecting the hyperacute phase of IS, with an AUC value greater than 0.98. The inclusion of experimental validation for the SN genes F12 and PLXDC2 not only corroborates our model's predictive accuracy but also underscores its potential utility in clinical settings. These findings offer promising avenues for improving early diagnosis and potentially guiding therapeutic strategies in IS.