Development of human brain organoids with functional vascular-like system

Human cortical organoids (hCOs), derived from human embryonic stem cells (hESCs), provide an excellent platform to study human brain development and diseases in complex 3D tissue. However, current hCOs lack microvasculature, resulting in limited oxygen and nutrient delivery to inner-most parts of hCOs. Previous studies demonstrated that the expression of human ETS variant 2 (hETV2) directly converts human fibroblasts to functional endothelial cells. Here, we engineered hESCs to ectopically express hETV2 to create in vitro vasculature in hCOs, namely vhCOs (vascularized hCOs). hETV2-expressing cells in hCOs contributed to forming a complex vascular network in hCOs. Importantly, the presence of vascularization resulted in enhanced functional maturation of organoids. We found that vhCOs acquired several blood-brain barrier (BBB) characteristics including increased expression of tight junctions, nutrient transporters, and trans-endothelial electrical resistance. Finally, hETV2-induced endothelium supported the formation of perfused blood vessels in vivo. These vhCOs form vasculature that resemble early prenatal brain, and present a robust model to study brain disease in vitro. mRNA profiles of vascularized brain cortical organoids with single-cell level were generated by deep sequencing