Abstract 712: Screening of Thrombolytic Agents in vivo Using a Novel Zebrafish Model of Ischemic Stroke Induced by Photochemical Thrombosis

Background: Timely thrombolytic therapy for acute ischemic stroke is important for improving neurological prognosis. Screening of thrombolytic agents on contemporary animal models of focal ischemic stroke is generally difficult as they require sophisticated surgical procedures such as induction of cerebral artery occlusion through mechanical ligation. Herein we seek to develop a novel zebrafish (Danio rerio) model of acute ischemic stroke for screening of thrombolytic drugs. Methods: All experiments were performed on a modified confocal optical microscope, which allows the induction of thrombosis at a selected blood vessel of larval zebrafish and the imaging of thrombotic and thrombolytic processes in real time. To initiate photochemical thrombosis, a 532-nm laser was focused at a blood vessel of a larva (4 dpf) that had been injected with a photosensitizer (rose bengal). To test the thrombolytic activity of tPA, we injected tPA to the blood vessel of a larval with a thrombus that partially occluded the blood flow. Results: Through photochemical means, we induced endothelial injury at selected blood vessel which subsequently triggered thrombosis. We show that an occlusion at the 1st branch of central artery drastically diminished the hemodynamics and cardiac function of larval zebrafish and impaired their capability to maintain balance during swimming whereas that at the basilar artery resulted in a high death rate. Immunofluorescent imaging shows that the photochemically induced thrombus comprised fibrins and platelets. After the injection of tPA to a larval with a partially occluded blood vessel, the fibrin mesh on the thrombus appeared sparse and limp which eventually led to the restoration of blood flow. Conclusions: Our zebrafish model of ischemic stroke is convenient to adapt and is highly reproducible. This model can potentially become an effective platform that benefits the screening of thrombolytic agents and the optimization of their dose.