Rat and dog quad-culture liver chip models: Characterization and use to interrogate a potential flavin-containing monooxygenase-mediated, species-specific toxicity of a histamine receptor antagonist.

Microphysiological systems (MPS) contain multiple cell types in three-dimension and often incorporate fluidic shear forces. There is interest in MPS for disease and efficacy modeling, safety and disposition studies. Animal cell-based MPS are needed to provide confidence in translation of data from human cell-based MPS. We developed rat and dog quad-culture liver MPS incorporating primary hepatocytes, sinusoidal endothelial, Kupffer and stellate cells. Using cryopreserved primary cells, we established a protocol for co-culturing cells under physiological flow conditions. Cells were evaluated for viability, morphology and function (e.g., albumin production, cytochrome P450 and flavin-containing mono-oxygenase (FMO) activity). Optimized culture conditions maintained high-quality rat and dog liver chips for up to 7 days. Model performance was evaluated with ABT-288, a histamine-3 receptor antagonist that caused elevated serum transaminases in dogs but not rats. This finding was partially attributed to high levels of FMO-mediated N-oxide metabolite produced in the dog. Key findings in our study were 1) dog chips showed much higher FMO-mediated N-oxidation compared to rat, and 2) dog chips exhibited modestly higher sensitivity to ABT-288 toxicity endpoints (albumin, alanine transaminase and lactate dehydrogenase) compared to rat. Species differences in N-oxidation were not observed in rat and dog liver microsomes or 2D hepatocyte monocultures, suggesting that properties of the quad-culture MPS were necessary to model higher FMO activity observed in dogs in vivo. The data suggest that this preclinical species liver chip model provides novel understanding of vitro to in vivo translation of ABT-288 dog liver toxicity.