Microclots and Neutrophil Activation as Potential Indicators for Stroke Risk and Reperfusion Failure

Overview

Stroke remains a major health burden worldwide. Many patients are severely disabled and stay in need of care. Mechanical thrombectomy has dramatically improved outcomes for stroke patients with large vessel occlusions, yet 40-50% of patients with successful recanalization remain severely disabled despite successful recanalization, a scenario called "futile recanalization". One of the causes for this lack of treatment effect is capillary obstruction, or "no reflow", potentially resulting from activated neutrophils and micrometer-sized blood clots. To address this issue, we employ digital holotomographic and atomic force microscopy to investigate the structural and chemical characteristics of blood and clot material in stroke patients and individuals at high risk of developing a stroke. Our study elucidates the association of activated neutrophils and microclots with stroke risk, and may be associated with clinical outcome, stroke ethology and reperfusion failure in patients with stroke. Leveraging label-free microscopy tools, could potentially lead to the discovery of new biomarkers for individualized stroke treatment and prevention, ultimately offering rapid identification of at risk patients and improving clinical outcomes

Background: Stroke remains a major health burden worldwide. Many patients are severely disabled and stay in need of care. Since introducing mechanical thrombectomy as a therapeutic option, clinical outcome has drastically improved over the last few years. However, despite successful macrovascular reperfusion (recanalization), patients with stroke still have a significant risk (about 40-50%) of remaining severely disabled, a scenario called "futile recanalization". One of the causes for this lack of treatment effect is capillary obstruction, or "no reflow", potentially resulting from activated neutrophils and micrometer-sized blood clots. Previous work in rodent stroke models demonstrated that removal of these capillary stalls indeed improves reperfusion and recovery after stroke. However, there is a lack of knowledge regarding the role of neutrophils or microclots in patients with stroke, and their potential to indicate reperfusion failure. Aim: The goal of our study is to search for activated neutrophils and microclots in peripheral blood samples from patients with stroke. We anticipate that neutrophil and microclot characteristics such as size, shape, or surface structure may indicate stroke risk, and may be associated with clinical outcome, stroke ethology and reperfusion failure in patients with stroke. Our goal is to improve the prediction of stroke risk and treatment success. Methodology: We plan to prospectively include 500 patients with acute and chronic stroke, as well as a control group. We have teamed up with biophysicists from the Swiss Federal Laboratories for Materials Science (EMPA) using the novel microscopic tools 3D rotational digital tomography (DHTM) to achieve an unprecedented resolution of less than 10 μm for detection of altered neutrophil phenotypes and microclots in peripheral blood samples. Furthermore, in patients undergoing mechanical thrombectomy, retrieved clots will be analyzed with high-density micro-computertomography (micro-CT). Quantity, mechanical and structural properties of microclots and neutrophils will be correlated with risk of reperfusion failure, stroke recurrence and clinical recovery. Analyses of clots from patients with large vessel occlusion will be used to derive risk of reperfusion failure along with most likely source of the clot, and thus, most likely stroke etiology. Potential Significance: Current diagnostic tools are insufficient to predict response to treatment, clot source or stroke recurrence risk. Our project has the potential to discover new, clinically applicable biomarkers identifying patients at risk within a few hours, enabling individualized stroke treatment and prevention.