Spatial Myeloid Landscape of Large Artery Atherosclerotic and Cardioembolic Thrombi Retrieved by Mechanical Thrombectomy

Cardioembolic (CE) and large artery atherosclerosis (LAA) strokes are two main causes of acute ischemic stroke (AIS), carrying a high risk of recurrence. Studies on the composition of CE and LAA thrombi have produced conflicting results, underscoring the need for further investigation into more effective treatment strategies. While myeloid cells such as neutrophils and monocytes are known to promote thrombosis in cardiovascular diseases, their specific roles in thrombosis across AIS subtypes remain unclear. We enrolled 42 AIS patients undergoing endovascular thrombectomy and retrieved their thrombi. Among 42 AIS patients undergoing endovascular thrombectomy, only thrombi and clinical data from patients with large artery atherosclerosis (LAA, n  = 8) or cardioembolic (CE, n  = 27) stroke were included in this study, focusing on the two major etiologic subtypes of AIS. Spatial transcriptomic profiling was performed on thrombi from a subset of these patients (LAA, n  = 4; CE, n  = 4) to investigate the molecular characteristics of myeloid cells. Immunohistochemistry (IHC) was conducted on thrombi from all included patients (LAA, n  = 8; CE, n  = 27) to quantify immune cell populations. Molecular profiling revealed distinct immunological activity between subtypes, despite the absence of statistically significant differences in immune cell abundance by IHC. LAA thrombi exhibited a profibrotic profile, with CD163+ macrophages showing upregulated TGF‐β pathway. scRNA‐seq analysis also revealed an enrichment of profibrotic macrophages in symptomatic atherosclerotic plaques, consistent with spatial transcriptomic findings from atherosclerotic thrombi. In contrast, CE thrombi exhibited increased neutrophil activation and NET formation, with elevated CXCR4 expression in neutrophils. Our findings suggest that the TGF‐β‐mediated profibrotic activity of macrophages and CXCR4‐driven NET formation in neutrophils are associated with distinct patterns of immunothrombosis in LAA and CE strokes, respectively. These observations could contribute to the development of etiology‐specific therapeutic strategies.