Abstract WP250: Evaluating & Optimizing the Model of Thrombotic MCAO in Mice

Abstract

Background: The embolic model of middle cerebral artery occlusion (MCAO) by thrombus mimics the ischemic stroke in human and is amenable to thrombolytic therapies with recombinant tissue plasminogen activator. However, this model has not been thoroughly investigated and standardized. The present study was performed to optimize this model in mice. Methods: Male C57BL/6 mice (8-10 week old) were subjected to MCAO induced by autologous or allogeneic thrombus measuring 5, 10, or 15 mm in length. Blood was placed in a tube (20μm diameter) with thrombin before injecting with sterile saline into internal carotid artery (ICA). Cerebral blood flow (CBF) was monitored by laser-Doppler or laser speckle before MCAO. Infarct was assessed by TTC staining 24 hours after MCAO. Neurological deficits were evaluated by modified neurological severity score (mNSS), rotarod test and corner test 1-7 days after ischemia. Results: Thrombus injection resulted in an abrupt drop of CBF to less than 30% of baseline in the MCA territory. The areas with more than 50% CBF decrease at 3 h after thrombus injection was significantly correlated to infarct volume at 24 h after MCAO (r=0.792, P=0.019, Pearson′s correlation analysis), suggesting that continuous decrease in CBF within 3 h can predict brain damage after stroke. No significant differences in infarct volume between autologous and allogeneic thrombus were observed (25.31±6.45 mm 3 vs 23.00±6.31 mm 3 , p>0.05). Allogeneic thrombi of 10 mm and 15 mm lengths caused reproducible infarct with detectable neurological deficits in mice. The 10 mm thrombus was chosen as the optimal thrombus length as it caused similar morphological and functional alterations compared with 60 min suture model of MCAO. In contrast, 15 mm thrombus resulted in significantly larger infract volume, worse sensorimotor functions and higher mortality in mice. Conclusion: Embolic MCAO did not yield stable CBF reduction compared to the classical suture MCAO. However, continuous decrease in CBF in the embolic model for at least 3 h resulted in successful infarct induction. The 10 mm autologous thrombus is suitable to induce reproducible infarct with neurological deficits in adult mice.