Generation of synthetic vascular organoids via orthogonal programming of human pluripotent stem cells

The development of functional human vasculature is essential for tissue engineering, disease modeling, and regenerative medicine. Conventional differentiation protocols of vascular lineages often exhibit lineage heterogeneity and limited control over cellular ratios. Here, we describe a protocol for generating vascular organoids (VOs) via orthogonal forward programming of hPSCs. By utilizing doxycycline-inducible activation of the transcription factors ETV2 and NKX3.1, hPSCs are rapidly directed toward endothelial and mural cell lineages, respectively. This strategy enables the assembly of VOs with precisely tunable cellular compositions within six days. When combined with fluorescent reporter lines (PECAM1-mRuby3 and ACTA2-EGFP), vascular networks can be visualized in real time without the need for tissue clearing or immunostaining. We detail procedures for stable cell line engineering, 3D organoid assembly, in vitro angiogenesis assays for drug screening, and in vivo transplantation under the mouse kidney capsule to form perfusable human vasculature. This platform provides a flexible, standardized, and scalable tool for investigating vascular biology, modeling inherited vasculopathies, and enhancing the vascularization of co-transplant tissues.