Abstract WP324: MCA/FeCl ₃ Thromboembolic Model, an Easily Reproducible Model for COVID-19-Induced Embolic Cerebrovascular Complications

COVID-19 neurological complications such as strokes and cognitive impairment have been reported. Yet the molecular mechanisms are under investigation. A mild and reproducible thromboembolic model will be a helpful tool for investigating COVID-thromboembolic complications. The aim of this study is to investigate the middle cerebral artery/ferric chloride (MCA/FeCl ₃ ) thromboembolic model as an easily and reproducible model for COVID-19-induced cerebrovascular embolic complications.

Methods: SARS-CoV-2 spike-protein of the alpha variant were injected intravenously (4 ug/animal) in K18 (transgenic knock-in humanized ACE2 in epithelial cells). Seven days later, MCA/FeCl ₃ thromboembolic model was induced in K18 mice by exposing the MCA and placing filter paper wet with FeCl ₃ . Laser speckle imaging was used for the assessment of blood flow and recanalization after 1,2,6, and 24 hrs. TTC was used to assess the infarct volume. Cognitive function was assessed using a novel object recognition test. Cerebral vascular density and blood-brain barrier (BBB) were assessed by immunohistochemistry staining using Iso-B4 lectin and Occludin-5 antibody.

Results: SARS-CoV-2 spike-protein caused a significant increase in the time required for vascular recanalization as detected by laser speckle imaging compared to control K18 mice. (P<0.05). In parallel, spike protein caused a significant increase in infarct size compared to control K18 mice (P<0.05). Our immunohistochemistry showed that spike protein decreased vascular density and increased vascular rarefaction compared to control K18 mice (P<0.05). A novel object recognition test showed that spike protein increased cognitive dysfunction compared to control (P<0.05). Western blot analysis showed that spike protein increased inflammatory markers and decreased BBB tight junction protein compared to control K18 mice (P<0.05). In conclusion , the MCA/FeCl ₃ thromboembolic model is an easily reproducible mouse model to examine COVID-19-induced stroke and cerebrovascular complications.