Development and characterization of a human arteriovenous malformation (AVM)-on-a-chip model

Brain arteriovenous malformations (AVMs) are a disorder where abnormal, enlarged blood vessels connect arteries directly to veins, without an intervening capillary bed. AVMs are one of the leading causes of hemorrhagic stroke in children and young adults. Most human sporadic brain AVMs are associated with genetic activating mutations in the KRAS gene. Our goal was to develop an in vitro model of human AVMs using human endothelial cells harbouring a clinically relevant KRAS mutation in a dynamic microfluidic culture system to enable vessel formation and perfusion to capture key morphological structure and barrier dysfunction characteristics of AVM. Using a combination of normal and KRAS4AG12V mutated endothelial cells (ECs), we demonstrated that vessels formed by KRAS4AG12V ECs were significantly wider and more leaky than vascular beds formed by wild-type ECs, recapitulating key structural and functional hallmarks of AVMs. Immunofluorescence staining revealed a breakdown of adherens junctions in mutant KRAS vessels only, leading to increased permeability of the vessel network. Furthermore, treatment with a MEK inhibitor, but not a PI3K inhibitor, resulted in an improvement in endothelial barrier function (decreased permeability) without affecting vessel width. Here, we have demonstrated the ability to create human KRAS-dependent AVM-like vessels in vitro in a self-assembling microvessel platform that is amenable to drug testing. ### Competing Interest Statement The authors have declared no competing interest.