Investigating the pathogenesis of large vessel occlusion in arterial thrombosis and acute ischemic stroke

Abstract

Acute ischemic stroke (AIS) is caused by pathological clot formation (thrombosis) within major blood vessels leading to the brain, causing subsequent occlusion. This constitutes a medical emergency where supply of oxygen and nutrients to the brain is blocked and may result in neurological damage and death. A major treatment option for AIS is the utilisation of thrombolytic therapies to degrade clot components, reopen blood vessels, and restore blood perfusion. Recombinant-tissue plasminogen activator (r-tPA), a fibrinolytic agent, has been the sole therapeutic approved for treatment of AIS via intravenous thrombolysis (IVT) since 1996 despite significant limitations which undermine its effectiveness. Although ongoing research demonstrates that adjunctive therapy such as the use of antiplatelets improves recanalisation and decreases reocclusion events, current antithrombotics on the market are unable to be used for AIS treatment due to endangerment of patient safety, namely, dangerous bleeding complications. As such, current treatment options for stroke patients are extremely limited. The first section of this thesis characterises murine models of arterial thrombosis, including electrolytic injury and ferric chloride–induced thrombosis in the common carotid artery. The thesis then details the development of a novel intravital macroscopy system, High-resolution Fluorescent Large Artery Intravital Macroscopy (Hi-FLAIM), enabling real-time visualisation of clot dynamics in vivo. Using this system, platelet and fibrin spatiotemporal organisation and determinants of clot stability are examined, and visualisation of fibrinolysis reveals unexpected fibrin-enhancing effects of r-tPA that may undermine thrombolysis. The final section assesses thrombolysis with adjunctive therapies and novel thrombin inhibitors in a mouse in situ carotid artery thrombolysis stroke model. Collectively, these studies aim to support the development of improved therapeutic strategies for AIS.