Biofabrication of Multicompartment Human Liver Tissues for Chemical Screening

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ABSTRACT / PROJECT SUMMARY Title: Biofabrication of Multicompartment Human Liver Tissues for Chemical Screening Drug-induced liver injury (DILI) is a leading cause of preclinical and clinical drug attrition, black box warnings on drugs, and withdrawals of drugs from the marketplace. Unfortunately, animal models do not always suffice to evaluate human DILI due to significant species-specific differences in drug metabolism pathways; therefore, in vitro models of the human liver are being increasingly utilized to evaluate compound (drugs/chemicals) metabolism and toxicity. However, current in vitro models of the human liver are unable to determine the effects of compounds on the three major compartments of the liver, namely hepatic, vascular, and biliary, and how toxicity to one compartment may affect the other compartments. Similarly, while there has been some progress in developing implantable liver tissue surrogates as cell-based therapies for patients suffering from end-stage liver failure, such tissues do not contain the above-mentioned liver compartments with physiological interconnections. Our studies have shown that primary human hepatocytes (PHH) and liver endothelial cells (LEC) display high levels of in vivo-like functions for 4+ weeks in vitro when organized into 3-dimensional (3D) extracellular matrix (ECM) microgels that are generated using a high-throughput droplet microfluidics platform (so-called microtissues). This microtissue technology is uniquely suited to control the microenvironment of liver cells and could potentially protect cells from the shear stress induced via 3D bioprinting. Furthermore, we have shown that cholangiocytes display sprouting behavior in decellularized liver ECM (dECM) but not in collagen-I or Matrigel alone and such sprouting behavior can be directed via 3D bioprinting. In this high-risk/high-reward R21 proposal, we will leverage these platforms and findings to test the novel hypothesis that a 3D-printed biomaterial scaffold containing hepatic microtissues and liver dECM can be used to generate liver-like functional and integrated compartments (vascular, hepatic, and biliary). In aim 1, we will fabricate and characterize 3D- printed structures containing hepatic microtissues and LEC-lined vascular channels, while in aim 2, we will incorporate cholangiocytes into the biofabricated structures and investigate the ability to control and detect bile flow. If successful, our efforts will yield a first-of-its-kind scalable 3D-printed human liver tissue containing integrated hepatic, vascular, and biliary compartments that displays stable levels of diverse liver functions for several weeks in vitro. Ultimately, our 3D-printed human liver tissue can be used for investigating the effects of compounds on all three compartments of the liver and their interactions, as well as for implanting into animal models as potential cell-based therapy for chronic liver disease and acute liver failure.