In vivo, hepatocytes have a polar morphology whereby cell surface proteins vary on the different 3D surfaces. This polar morphology can only be replicated in vitro by providing an overlay of collagen or other basement membrane extracts on top of a hepatocyte monolayer. By “sandwiching” hepatocytes between these basement membrane protein mixtures, they form the correct basal surface structures and a small apical membrane pocket between cells known as bile canaliculi. These structures enable excretion of bile acids from the hepatocytes, replicating the situation in vivo. It is generally accepted that the sandwich culture method best reflects the 3D in vivo shape of hepatocytes, while maintaining the functionality of a 2D format. All of our plated hepatocyte qualification studies are performed using the sandwich culture method.
The most common application of plated hepatocytes for in vitro drug metabolism and pharmacokinetics (DMPK) studies is to determine the potential of drug-drug interactions via induction of the gene expression of various CYP450 enzymes. The amount and activity of these enzymes are known to increase when cells are exposed to certain chemical substances. However, an increase in the activity of a particular P450 enzyme might also affect a different drug in a patient's regime, leading to a drug-drug interaction (DDI) that could impact the efficacy and safety of more than one drug. Regulatory agencies require an analysis of the DDI potential in hepatocytes for CYP3A4, CYP1A2, and CYP2B6, which indicates whether a clinical DDI study is required. Our Cryopreserved Human Hepatocytes, Induction qualified, (HUCPI) are precharacterized to exhibit enzyme induction levels recommended by the FDA for evaluation of DDI.