Abstract TP340: The Level of Occludin in Blood as a Potential Biomarker for Blood-Brain Barrier Damage and Predicting Hemorrhage Transformation After Acute Ischemic Stroke

Abstract

Fear of hemorrhage transformation (HT) has been the primary reason for withholding the effective recanalization therapies (thrombolysis or thrombectomy) from most acute ischemic stroke (AIS) patients. Currently there is no reliable indicator available to predict HT before recanalization. The degradation of tight junction proteins plays a critical role in blood-brain barrier (BBB) disruption in ischemic stroke. We hypothesize that since occludin fragment in peripheral blood is derived from the degradation of occludin on cerebral microvessels, elevated blood occludin level directly reflects BBB disruption and may serve as a biomarker for BBB damage to predict the risk of HT after recanalization. In this study, we determined occludin fragment in the blood of rats, non-human primates and human patients after AIS using ELISA assay, and evaluated its level with BBB damage, HT, and other neurological outcomes. We found that ischemia induced rapid occludin degradation and BBB disruption, while occludin fragment was released into the blood circulation. Cerebral ischemia resulted in a dramatic increase of occludin fragments in rat blood samples after 4-hr ischemia, which was correlated well with occludin loss from ischemic cerebral microvessels. In the blood sample from ischemic rhesus monkeys, occludin level significantly increased after 2h ischemia from baseline, which correlated well with brain infarction shown in MRI images. We further collected the sera of AIS patients as early as they arrived at hospital. Our results indicated that the level of occludin increased in accord with ischemia onset time and neurological dysfunctions. The level of blood occludin in AIS patients with HT was much higher that those without HT. Together, our findings from rats, non-human primates and patients suggest that the level of occludin fragment in blood could serve as a biomarker for HT and neurological outcome following AIS, which could be used to safely guide recanalization for AIS in the clinic.