Human hepatic HepaRG cells maintain high intrinsic CYP450 activity/metabolism and significantly outperform standard HepG2/C3A cells used in drug pharmacology applications

Introduction: Conventional in vitro human hepatic models for drug testing are based on the use of cell lines or primary human hepatocytes (PHHs). However, limited availability, inter-donor functional variability and early phenotypic alterations of PHHs in vitro restrict their use; whilst cell lines such as HepG2/C3As lack a substantial and variable set of liver-specific functions, specifically, CYP450 activity. In this study we compared CYP450 activity/ metabolism between HepG2/C3A and human HepaRG cells as hepatic models for pre-clinical drug testing. Methods: Human hepatic cell lines [HepG2/C3A or HepaRG] were grown to >80% confluence on collagen-I-coated plates and treated (in triplicates) 24 h with prototypical inducers rifampicin (CYP3A4) and omeprazole (CYP1A2), [n=3]. 50μM testosterone or phenacetin were added and supernatant and cell samples taken after 2 hours of incubation at 37°C. CYP1A2/3A4 activity [P450-Glo™-Luminometry; Promega] was determined (Figure 1). Relative turnover of testosterone [HPLC] and phenacetin [LC-MS/MS] metabolites was also measured. Cell phenotype was assessed by light-microscopy, histology (PAS-Glycogen), CYP3A4, F-actin/phalloidin, and JC-1 fluorescent-staining. Results: Figure 1 shows HepaRG CYP1A2/3A4 activity was 40-80x fold >> HepG2/C3A cells [P<0.001]; Drug profiling revealed HepaRGs had both enhanced production of major metabolites of phenacetin and testosterone and more intact drug metabolism compared with HepG2/C3A. In contrast with HepG2/C3A, HepaRGs displayed a more intact hepatic phenotype, including: Strong positive glycogen, CYP3A4 staining, high JC-1-positive intrinsic metabolic activity (ΔΨm) and organotypic gross morphology. Discussion / Conclusion: HepaRG cells may represent a more physiologically-relevant pre-clinical platform for CYP450 activation/ inhibition, safety pharmacology, as well as drug-drug interaction studies.