Engineered three-dimensional liver mimics recapitulate critical rat-specific bile acid pathways.

The research team created a three-dimensional liver mimic using layers of primary rat hepatocytes and liver sinusoidal endothelial cells. They compared this system to conventional in vitro models like hepatocyte monolayers and collagen sandwich cultures. To analyze bile acid levels, they developed a high-pressure liquid chromatography and mass spectrometry method with a detection limit of 1 ng/mL. This technique allowed for precise quantification of eight primary rat bile acids. The team monitored bile acid composition over a 2-week culture period to assess stability and changes in ratios. They focused on the conjugated cholic acid to chenodeoxycholic acid ratio, a key marker of bile acid homeostasis. The study also examined the biosynthesis of tauro-β-muricholic acid in each system. By comparing results across models, the researchers evaluated which system best replicated in vivo conditions.

The three-dimensional liver mimic maintained a conjugated cholic acid to chenodeoxycholic acid ratio similar to that observed in live rats. This ratio was significantly higher in collagen sandwich cultures, indicating a deviation from physiological behavior. The biosynthesis of tauro-β-muricholic acid doubled in the liver mimic over the 2-week period. In contrast, this bile acid decreased in conventional culture systems. The high-pressure liquid chromatography method detected bile acid levels as low as 1 ng/mL, a significant improvement over previous techniques. These findings suggest that the liver mimic better reflects in vivo bile acid homeostasis. The engineered system demonstrated stable bile acid composition over time, unlike other models. These results highlight the liver mimic's potential as a more accurate in vitro platform for studying hepatic metabolism.

The study demonstrated that the three-dimensional liver mimic more accurately recapitulates bile acid homeostasis seen in live rats. The engineered system maintained a bile acid ratio that aligns with in vivo observations, unlike conventional models. The biosynthesis of tauro-β-muricholic acid increased in the liver mimic while decreasing in other systems. These trends suggest that the liver mimic provides a physiologically relevant environment for bile acid metabolism. The high-resolution analytical method enabled precise quantification of bile acids, improving the accuracy of in vitro studies. The findings support the use of engineered liver mimics in future research on hepatic function. The study did not propose new therapeutic directions but emphasized the importance of model selection in bile acid research. The authors suggest that such models could enhance the development of more accurate in vitro systems for liver studies.