Reverse bioengineering of the liver: developmental principles for next-generation liver-on-a-chip systems.

Despite major advances in liver-on-a-chip and organoid technologies, most current in vitro liver models remain limited. Here, it is argued that these limitations are fundamentally conceptual rather than purely technical. Reverse bioengineering is introduced as a unifying design framework for liver-on-a-chip systems, in which human liver development is treated as the primary engineering blueprint rather than adult hepatic phenotype as the endpoint. Existing cell sources, liver organoids, and liver-on-a-chip platforms are critically evaluated, demonstrating that each capture complementary but incomplete aspects of liver development. Pluripotent stem cells uniquely enable access to intrinsic developmental programs and cellular diversity, organoids partially reconstruct early developmental trajectories through self-organization, and microphysiological systems provide extrinsic cues without fully encoding developmental execution. Finally, futured directions are outlined, highlighting developmentally coordinated multi-organ systems, quantitative developmental benchmarks, and the emerging role of multi-omics-enabled Digital Twins and artificial intelligence in guiding and interpreting liver-on-a-chip design.