Enhanced Maturity and Functionality of Vascular Human Liver Organoids through 3D Bioprinting and Pillar Plate Culture

Liver tissues, composed of hepatocytes, cholangiocytes, stellate cells, Kupffer cells, and sinusoidal endothelial cells, are differentiated from endodermal and mesodermal germ layers. By mimicking the developmental process of the liver, various differentiation protocols have been published to generate human liver organoids (HLOs) in vitro using induced pluripotent stem cells (iPSCs). However, HLOs derived solely from the endodermal germ layer often encounter technical hurdles such as insufficient maturity and functionality, limiting their utility for disease modeling and hepatotoxicity assays. To overcome this, we separately differentiated EpCAM⁺ endodermal progenitor cells (EPCs) and mesoderm-derived vascular progenitor cells (VPCs) from the same human iPSC line. These cells were then mixed in a BME-2 matrix and concurrently differentiated into vascular human liver organoids (vHLOs). Remarkably, vHLOs exhibited a significantly higher maturity than vasculature-free HLOs, as demonstrated by increased coagulation factor secretion, albumin secretion, drug-metabolizing enzyme expression, and bile acid transportation. To enhance assay throughput and miniaturize vHLO culture, we 3D bioprinted expandable HLOs (eHLOs) in a BME-2 matrix on a pillar plate platform derived from EPCs and VPCs and compared them with HLOs derived from endoderm alone. Compared to HLOs cultured in a 50 μL BME-2 matrix dome in a 24-well plate, vHLOs cultured on the pillar plate exhibited superior maturity, likely due to enhanced nutrient and signaling molecule diffusion. The integration of physiologically relevant patterned liver organoids with the unique pillar plate platform enhanced the capabilities for high-throughput screening and disease modeling.