An Alternative Photothrombotic Model of Transient Ischemic Attack

Animal models mimicking human transient ischemic attack (TIA) and cerebral microinfarcts are essential tools for studying their pathogenetic mechanisms and finding methods of their treatment. Despite its advantages, the model of single arteriole photothrombosis requires complex experimental equipment and highly invasive surgery, which may affect the results of further studies. Hence, to achieve high translational potential, we focused on developing a TIA model based on photothrombosis of arterioles to combine good reproducibility and low invasiveness. For the first time, noninvasive laser speckle contrast imaging (LSCI) was used to monitor blood flow in cerebral arterioles and reperfusion was achieved. We demonstrate that irradiation of mouse cerebral cortical arterioles using a 532-nm laser with a 1-mm-wide beam at 2.4 or 3.7 mW for 55 or 40 s, respectively, after 15 mg/kg intravenous Rose Bengal administration, induces similar ischemia–reperfusion lesions resulting in microinfarct formation. The model can be used to study the pathogenesis of spontaneously developing cerebral microinfarcts in neurodegeneration. Reducing the exposure times by 10 s while maintaining the same other parameters caused photothrombosis of the arteriole with reperfusion in less than 1 h. This mode of photodynamic exposure caused cellular and subcellular level ischemic changes in neurons and promoted the activation of astrocytes and microglia in the first day after irradiation, but not later, without the formation of microinfarcts. This mode of photodynamic exposure most accurately reproduced human TIA, characterized by the absence of microinfarcts.