Abstract DP038: Transcriptome of Local Immune Cells in Hyperacute Human Ischemic Stroke Hemorrhagic Transformation

Objective: To evaluate arterial transcriptomic profiles of ischemic milieu using a prospective single-center ischemic stroke biobank of ischemic blood obtained during thrombectomy for large vessel occlusion (LVO). Methods: From September 2021 to February 2024, we selected patients with first-ever LVO of the anterior circulation who underwent endovascular thrombectomy (EVT). We attempted microcatheter aspiration within the core of the arterial occlusion, and bulk RNA sequencing was performed with aspirated arterial blood. Carotid arterial blood was used as control. Arterial transcriptomics were compared between patients with or without hemorrhagic transformations, classified as any degree of hemorrhagic infarct of parenchymal hematoma. Results: During the study period, 156 EVT cases that met the study criteria were performed. Twenty six patients were included for the final analysis. Hemorrhagic transformation was confirmed in 15 patients. Compared to peripheral arterial blood, ischemic arterial blood showed gene enrichment of active cell communication and receptor–ligand interactions, likely involving circulating immune cells; endothelial interactions; paracrine factors; and cytokine, chemokine, or growth factor signaling. Ischemic arterial blood in patients with hemorrhagic transformation showed innate immune activation associated with myeloid cell activation, oxidative stress, endothelial cell and extracellular matrix damage. Analysis of the Database for Annotation, Visualization and Integrated Discovery for significant pathways revealed enrichment in innate immunity pathways such as the NOD-like receptor signaling pathway represented by DEFA family members (DEFA1, DEFA1B, DEFA3, and DEFA4). Downstream immune activation was further supported by upregulation of complement and antigen presentation genes (C1QA, C1QB, C4A, C4B, ELANE, CTSG, CD80, and HLA-DQB1). Selective analysis of genes associated with immune activation revealed increased expression of neutrophil extracellular trap formation (MPO, C5AR1, S100A9), myeloid cells, and oxidative stress, while decreased expression of genes associated with complement and adaptive immunity. Interpretation: This study provides strong evidence for the involvement of immune pathways in ischemic stroke, particularly neutrophil-mediated innate immunity associated with hemorrhagic transformation. By delineating these mechanisms, our results open avenues for the development of gene-targeted neuroprotective strategies.