Liver Tissueoid on‐a‐Chip Modeling Liver Regeneration and Allograft Rejection

ABSTRACT 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.