In vitro models of the gut-liver axis: what we’ve learned and what remains to be built

The gut-liver axis maintains metabolic homeostasis and immune regulation through continuous bidirectional communication, and its dysregulation contributes to a range of metabolic, inflammatory, and immune-mediated diseases. Integrated gut-liver axis model systems offer unique tools for dissecting these complex interactions by isolating individual variables that are difficult to disentangle in vivo , while allowing flexible experimental controls over them. Here, we review advances in gut-liver axis models from static co-cultures to microfluidic systems and their applications in pharmacokinetic and mechanistic studies. We identify underexplored areas, including metabolite-mediated gut-liver crosstalk, immune-mediated interorgan communication, and disease-specific modeling, and outline technical challenges to achieving physiologically faithful and reliable integrated platforms. By addressing these challenges, gut-liver axis models will contribute to a mechanistic understanding of gut-liver pathobiology that is difficult to achieve through clinical studies, animal models, or individual organ systems alone.