Investigating etiological markers in acute ischemic stroke clots

Identifying etiological biomarkers in acute ischemic stroke (AIS) clots is vital for optimizing diagnosis, treatment and outcomes. Thrombo-inflammatory components such as lymphocytes, macrophages, neutrophils, and neutrophil extracellular traps (NETs) associate with stroke risk factors and form a thrombus through different mechanisms. Clot contraction is a platelet-driven process of fibrin remodelling, involving multiple factors like the cytoskeletal proteins Talin and Myosin-9 and the coagulation factor XIIIa-mediated fibrin cross-linking which can alter the clot density, permeability and size. We studied the expression of the different WBC subtypes, NETs as well as markers that are involved in clot contraction like Talin, Myosin-9 and FXIIIa in clots from different etiologies to improve our understanding of the stroke pathophysiology. AIS clots from 100 cases each of large artery atherosclerosis (LAA), cardioembolic (CE) and cryptogenic stroke etiology were collected per-pass as part of the CÚRAM RESTORE registry of AIS clots and were analysed for the expression of WBC subtypes and NETs. For the analysis of Talin, Myosin-9 and FXIIIa expression, clots from 50 cases from each etiology were included. The extracted clot area (mm2) was measured using ImageJ software. Martius Scarlet Blue stain was used to identify the main histological components of the clots. Immunohistochemical staining was used to identify the expression of each marker as well as the distribution pattern of NETs, Talin, Myosin-9 and FXIIIa. The cellular and histological components were quantified using Orbit Image Analysis software. LAA clots were larger, with more red blood cells and fewer WBCs than CE clots. CE clots were smaller and showed higher expression of neutrophils and web-like NETs as well as higher expression of the proteins involved in clot contraction. NETs distribution was significantly associated with peripheral location in CE clots, while a mixed distribution was observed in LAA clots. The expression of Talin, Myosin-9 and FXIIIa in CE clots showed a cluster-like distribution throughout the clot structure, whereas in LAA clots, they were mainly around the periphery of the clot. The differences in clot size, composition and biomarkers expression and distribution between CE and LAA clots suggests an etiology-specific mechanism of thrombosis which can provide insight into the mechanism of clot formation in AIS. This can inform therapeutic strategies such as thrombectomy and thrombolytic therapy and can guide future research into more personalized stroke management.

Publisher

University of Galway

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CC BY-NC-ND

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University of Galway Theses (PhD Theses)