Liver Tissueoid on-a-Chip Modeling Liver Regeneration and Allograft Rejection.

The lack of physiologically relevant in vitro models remains a limitation in liver transplantation research. Progress in organ-on-a-chip technologies enables the generation of clinically translatable data in vitro. A vascularized liver tissueoid-on-a-chip (LToC) model is engineered to replicate human liver tissue's structural and functional features for modeling liver regeneration and allograft rejection. The LToC comprises a microfluidic device containing donor-matched human hepatic progenitor cells and intrahepatic portal vein endothelial cells embedded in a fibrin matrix and maintained in dynamic culture for 49 days. The system supports self-assembly into a perfusable microvascular network and liver lobule-like architecture, with >95% cell viability, stable vascular integrity, and active hepatic function (albumin, urea, complement factors, and hepatocyte growth factor secretion). The mature tissueoid includes hepatocytes (CK18+, albumin+, CYP2D6+), cholangiocytes (CK19+, EPCAM+), Kupffer cells (CD68+), stellate cells (PDGFR-β+), and endothelial cells (CD31+). Perfusion with allogeneic T cells induces cellular rejection, characterized by decreased viability, endothelial disruption, hepatic marker loss, HLA-I upregulation, and a proinflammatory cytokine response (IL-6, TNF-α, IL-1β, IFN-γ, granzyme A and B, and perforin). The LToC provides a physiologically relevant platform for studying immune-mediated liver injury, tissue regeneration, and allograft rejection, with potential applications in immunosuppressive drug testing and personalized transplant medicine.