Angiopoietin-2 Inhibition Rescues Arteriovenous Malformation in a Smad4 Hereditary Hemorrhagic Telangiectasia Mouse Model

Background: Hereditary hemorrhagic telangiectasia is an autosomal dominant vascular disorder caused by heterozygous, loss-of-function mutations in 4 transforming growth factor beta (TGFβ) pathway members, including the central transcriptional mediator of the TGFβ pathway, Smad4. Loss of Smad4 causes the formation of inappropriate, fragile connections between arteries and veins called arteriovenous malformations (AVMs), which can hemorrhage leading to stroke, aneurysm, or death. Unfortunately, the molecular mechanisms underlying AVM pathogenesis remain poorly understood, and the TGFβ downstream effectors responsible for hereditary hemorrhagic telangiectasia–associated AVM formation are currently unknown. Methods: To identify potential biological targets of the TGFβ pathway involved in AVM formation, we performed RNA- and chromatin immunoprecipitation–sequencing experiments on BMP9 (bone morphogenetic protein 9)-stimulated endothelial cells (ECs) and isolated ECs from a Smad4-inducible, EC-specific knockout...