A microphysiological system HHT-on-a-chip platform recapitulates patient vascular lesions.

Hereditary Hemorrhagic Telangiectasia (HHT) is a rare congenital disease in which fragile vascular malformations (VM) focally develop in multiple organs. There are few treatment options and no cure. HHT patients inherit loss-of-function mutations affecting Alk1-Eng signaling; however, why this manifests as VMs remains poorly understood. Here we have developed a fully human cell-based microphysiological system of perfused vasculature in which inducible shRNA controls endogenous Alk1 in primary endothelial cells (EC). Resulting VMs develop over several days, recapitulate patient VM appearance, and require only a subpopulation of Alk1-deficient EC to trigger lesions. Single-cell transcriptomics suggests microvessel pruning and regression contribute to VM, while loss of PDGFB implicates mural cell recruitment. Finally, pharmacological VEGF/VEGFR inhibition blocks lesion formation. In summary, we have developed an HHT-on-a-chip model that faithfully reproduces HHT patient lesions and that can be used to better understand HHT disease biology and identify potential new HHT drugs.