The 3D spheroid system has been optimized for functional stability and primary human hepatocytes retain expression of phase 1 and phase 2 drug metabolizing enzymes and drug transporters for multiple weeks in culture (Fig. 1a-c).
As a consequence, metabolic profiles remain temporally stable, as demonstrated by maintained metabolic profiles of dextromethorphan (Vorrink et al., 2017). Dextromethorphan is metabolized by CYP2D6 to dextrorphan and by CYP3A4 to 3-methoxymorphinan, which can be metabolized further to 3-hydroxymorphinan. In the study by Vorrink et al, three donors were analyzed which classified phenotypically as extensive (donors 1 and 2) or poor (donor 3) CYP2D6 metabolizers. In both extensive metabolizers, the vast majority of dextromethorphan was demethylated in freshly isolated cells as well as in spheroids after three weeks in culture (Fig. 1d). Over culture time, the metabolic spectrum slightly tilted from CYP2D6-mediated O-demethylation to N-demethylation catalyzed by CYP3A4. Notably, dextromethorphan metabolism in the poor CYP2D6 metabolizer (donor 3) was strongly biased towards 3-methoxymorphinan in freshly isolated cells as well as after long-term spheroid culture in agreement with in vivo data .
Combined, the presented data indicates that metabolic profiles are stable in 3D spheroid culture and phenotypic differences observed in vivo can be successfully translated into an in vitro setting. This constitutes a key prerequisite for metabolic profiling, pharmacokinetic analyses and drug clearance assessments – all of which we provide to our clients.
- Jones et al., CPT, 1996