Abstract TP2: Increase of EphrinB2/EphB4 Signaling Reduces the Severity of Brain Arteriovenous Malformation in Endoglin Deficient Mice Through Reduction of Angiogenesis and Inflammation

Abstract

Background and Purpose: Vessels in brain arteriovenous malformations (bAVMs) have reduced mural cells and are prone to rupture, causing intracranial hemorrhage. EphrinB2/EphB4 signaling has role in maintaining vascular integrity. Hypothesis: Reducing EphrinB2 in endothelial cells (ECs) enhances, while increasing EphrinB2 reduces bAVM severity in endoglin ( Eng ) deficient mice. Methods: BAVMs was induced by Eng deletion in adult Eng -floxed mice ( Eng f/f ) globally or in ECs using a rosa promoter driving ( Rosa-creER ) or a platelet-derived growth factor b promoter driving ( Pdgfb- icreER) estrogen inducible cre. Pdgfb- icreER was used to delete EphrinB2 in ECs. AAV-VEGF was injected into the brain to induce angiogenesis. Pre-clustered EphrineB2-Fc was delivered intraperitoneally to RosaCreER ; Eng f/f mice and Pdgfb-icreER:Eng f/f mice twice per week for 2 weeks, starting 6 weeks after AVM induction. The brains were taken 8 weeks after AVM induction to study vessel density, dysplasia vessels, mural cell coverage, microhemorrhage and gene expression. Results: RNAseq data shown increased EphB4 in bAVMs of EC Eng deleted mice, suggesting an imbalance of EphrinB2/EphB4 ratio. Co-deletion of EphrinB2 with Eng in ECs increased the penetrance of bAVM phenotype from 46% (EC Eng deletion) to 100%, smooth muscular negative vessels, and increased expression of leukocytes differentiation, inflammatory, and vasculogenesis genes. EphrinB2-Fc treatment reduced vessel density and dysplasia vessels; increased vascular pericyte and smooth muscle cell coverage; decreased microhemorrhage in bAVMs of mice with global or EC Eng deletion, and decreased the expression of pro-inflammatory, oxidative phosphorylation, and angiogenic genes. Conclusion: Co-deletion of EphrinB2 with Eng in ECs enhances bAVM severity by increasing inflammation while EphrinB2-Fc treatment reduced bAVM severity in Eng deficient mice by reducing angiogenesis and inflammation.