Figure 1. Human ectopic artificial liver mouse. Primary human hepatocytes are cocultivated with stabilizing stromal mouse fibroblasts on collagen-coated plates for 7-10 days. They are then encapsulated with human liver endothelial cells in polyethylene glycol-diacrylate (PEG-DA) scaffolds derivatized with adhesion Arg-Gly-Asp-Ser (RGDS) peptides. The human ectopic artificial livers (HEALs) are about 20 mm in diameter and 250 m thick, with about 0.5106 human hepatocytes. They are surgically placed intraperitoneally into laboratory mice, in which the implants become engrafted and vascularized. The HEAL mice provide models to study human metabolites, drug exposure via different routes, drug-drug interactions and drug toxicity. (Figure based on Figure 1 in ref. 1.)