Minimizing variability in the filament middle cerebral artery occlusion model in C57BL/6 mice by surgical optimization - the PURE-MCAo Model

BACKGROUNDIn the intraluminal filament middle cerebral artery occlusion (fMCAo) model, there is considerable variability in infarct volumes, especially in C57BL/6 mice, which often lack the P1 segment of the posterior cerebral artery (PCA) and therefore develop not only MCA but also PCA area infarcts after fMCAo. Another factor contributing to infarct volume variability is collateral flow to the MCA area. The aim of this study was to establish an optimal surgical method to reduce the infarct volume variability in C57BL/6 mice. METHODSC57BL/6 mice were subjected to 60 min of fMCAo with cerebral blood flow monitored by laser Doppler fluxmetry. The influence of the common carotid artery (CCA) ligation, filament morphology, and the pterygopalatine artery (PPA) ligation on lesion volume and neurological severity score 24 hours after reperfusion were assessed. RESULTThe use of filaments with appropriate length of coating and ligation of the PPA while maintaining perfusion of the CCA prevented the development of infarcts in the PCA area, resulted in pure MCA infarcts (68.3{+/-}14.5mm3, 26.1{+/-}3.6% of the hemisphere with Swansons correction) and reduced the variability of infarct volumes by more than half to 13.9% of the standard deviation divided by mean. CONCLUSIONSUsing improved surgical methods with suitable filaments to induce MCA occlusion in mice, we were able to produce PCA area-unaffected reproducible infarcts exclusively in the MCA area with reduced variability (PURE-MCAo). Our results may thus help to increase the reproducibility of the fMCAo model and reduce the number of animals required in preclinical stroke research.