Development of human induced pluripotent stem cell-derived vascularized hepatic assembloids

Vascularization is a critical process for the proper function of tissues and organs, as it ensures the delivery of nutrients, oxygen, and the removal of waste products. The development of functional vascular networks requires precise differentiation of endothelial cells into tissue-specific lineages, regulated by vascular endothelial growth factor (VEGF), Notch, and Wnt signaling pathways. Reproducing these processes in vitro is a significant challenge in tissue engineering, particularly for generating organ-specific vasculature. In this study, we generated induced pluripotent stem cell (iPSC)-derived, heterogeneous vascular and hepatic organoids under atmospheric oxygen tension and matrix-free conditions, serving as a versatile approach in generating stem cell-derived models in the absence of complex extracellular matrices (ECM) or hypoxic culture. The composition and specification of the vascular organoids, assessed using single-cell RNA sequencing, revealed stage-specific patterns of gene expression. These vascular organoids were shown to interact with and arborize within hepatic organoids, enhancing hepatocyte maturation and function. Single-cell sequencing revealed the enrichment of liver-specific sinusoidal endothelial cell features, and upon further functional validation, attributes including Factor VIII secretion were identified. Collectively, these findings offer new insight into how the co-emergence of organoid populations can contribute to downstream cellular specialization.