Abstract TP100: Post-Transcriptional Inactivation of MMP-12 Immediately After Reperfusion Facilitates Neurological Recovery After Ischemic Stroke

Abstract

Introduction: We recently showed in a rodent model of transient focal cerebral ischemia that matrix metalloproteinase-12 (MMP-12) induction in the ischemic brain promotes post-stroke blood-brain barrier disruption, apoptosis, demyelination, and infarction. The purpose of the present study is to investigate the role of elevated MMP-12 on post-stroke neurological function and to identify the time window of therapeutic opportunity for MMP-12 suppression. Methods: Adult male Sprague-Dawley rats were subjected to transient middle cerebral artery occlusion and reperfusion. Cohorts of rats (n =8-15/group) were administered with either MMP-12 shRNA or scrambled shRNA sequence (vehicle control) expressing plasmids (1 mg/Kg; intravenous) formulated as nanoparticles. The differences in sample size of various cohorts were attributed to the exclusion criteria followed, high mortality rate in vehicle control-treated group, and sample size required for statistical analysis. To assess the reflex, balance, sensory, and motor functions, rats from various cohorts were subjected to modified neurological severity scoring (mNSS), adhesive removal test, beam walk test and rotarod test at day 1, 3 and 5 of reperfusion. To assess the time window of therapeutic opportunity, various cohorts of rats were treated at 5 min, 3h, and 6h of reperfusion. Investigators blinded to study groups analyzed all outcome parameters. Results: The post-stroke percent survival rate in cohorts treated with MMP12shRNA expressing plasmids range from 82 to 89 as compared to 67 in vehicle control-treated group. The cohort of rats treated at 5 min of reperfusion with MMP-12snRNA expressing plasmids showed significantly better functional recovery as assessed by various neurological tests. However, delayed administration of MMP-12snRNA expressing plasmid (either at 3h or 6h of reperfusion) failed to promote any significant improvement in post-stroke neurological recovery. Conclusions: Post-stroke induction of MMP-12 in the ischemic brain contributes to neurological deficits and impedes recovery. MMP-12 targeting treatments immediately after reperfusion could offer substantial therapeutic benefits.