VASCULAR EXPRESSION OF ANGIOPOIETIN1, α5B1 INTEGRIN AND TIGHT JUNCTION PROTEINS IS TIGHTLY REGULATED DURING VASCULAR REMODELING IN THE POST-ISCHEMIC BRAIN

The post-stroke angiogenic response is accompanied by changes of tight junctions (TJs) of the blood brain barrier (BBB). However, the precise dynamic change of TJ proteins (TJPs) in the different stages of stroke induced vascular remodeling and the molecules mediating these processes have yet to be fully defined. To investigate the temporal relationship between changes in TJPs, the proangiogenic factor alpha 5 beta 1 integrin and the anti-permeability factor Ang1 in cerebral vessels following cerebral ischemic stroke, male C57BI/6 mice were subject to 90 min of ischemia by temporary occlusion of the middle cerebral artery followed by reperfusion and their brains analyzed 0, 1, 2, 4, 7 and 14 days post-ischemia. Immunofluorescent studies demonstrated that in the ischemic penumbra, TJPs claudin-5 and ZO-1 levels decreased during the early stages of vascular remodeling, but then increased in the later stages. In contrast, within the ischemic core, TJPs levels decreased over the 14-day time-course, plateaued at day 4, and remained at low levels up to day 14. In the penumbra, Ang1 expression was induced, peaking at the same time point as alpha 5 beta 1 expression. Consistent with these findings, oxygen glucose deprivation/reperfusion induced expression of alpha 5 beta 1 and Ang1 on brain endothelial cell (BEC) in a similar manner in vitro, which correlated closely with BEC proliferation and increased expression of TJPs. Our results demonstrate that in the post-ischemic penumbra, a tight temporal correlation exists between the angiogenic markers alpha 5 beta 1 and Ang1 and the TJPs, suggesting a potential role for Ang1 and alpha 5 beta 1 in promoting BBB integrity following ischemic stroke. (C) 2017 IBRO. Published by Elsevier Ltd. All rights reserved.