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Abstract Despite the importance of hepatotoxicity testing in the development of new potential pharmaceuticals, standardized methods for preclinical in vitro hepatotoxicity is complicated by the perceived adequacy of approach, diversity of origin of cells, and the ability to retain a satisfactory hepatocellular phenotype. Additionally, the confidence with which cells mimic in vitro hepatocytes is dictated by the spatial dynamics of the cell culture microenvironment. This study sought to compare the proteome of conventional monolayer cultures of an immortalized hepatocyte cell line (HepG2) with more complex three-dimensional spheroid cultures to ascertain whether changes in culture technique better mimic the phenotype of hepatocytes and thereby improve responses to in vivo hepatotoxins. The proteome was assayed using isobaric tagging from six independent experiments, yielding relative quantitation of over 4600 proteins per multiplexed set. Approximately 34% of proteins present in all replicates differed between monolayer and 3D spheroid cultures. These data suggest that the cellular transition from an exponential to an equilibrium growth phase is inconsistent across biological replicates during spheroid formation which then variably alters the proteome from a stable phenotype in monolayers. Continuous exposure to hepatotoxins, did not implicate specific subsets of proteins in describing the associated mechanisms of toxicity of each drug. However, dynamic changes in HepG2 cells cultured as 3D spheroids were described. These data suggest that the duration of spheroid culture could be essential to reconcile the differences observed in the spheroid proteome to achieve reproducible proteomic transitions to a stable 3D spheroid phenotype. [ABSTRACT FROM AUTHOR]

Hepatotoxicity remains a major challenge in drug development despite preclinical toxicity screening using hepatocytes of human origin. To overcome some limitations of reproducing the hepatic phenotype, more structurally and functionally authentic cultures in vitro can be introduced by growing cells in 3D spheroid cultures. Characterisation and reproducibility of HepG2 spheroid cultures using a high-throughput hanging drop technique was performed and features contributing to potential phenotypic variation highlighted. Cultured HepG2 cells were seeded into Perfecta 3D® 96-well hanging drop plates and assessed over time for morphology, viability, cell cycle distribution, protein content and protein-mass profiles. Divergent aspects which were assessed included cell stocks, seeding density, volume of culture medium and use of extracellular matrix additives. Hanging drops are advantageous due to no complex culture matrix being present, enabling background free extractions for downstream experimentation. Varying characteristics were observed across cell stocks and batches, seeding density, culture medium volume and extracellular matrix when using immortalized HepG2 cells. These factors contribute to wide-ranging cellular responses and highlights concerns with respect to generating a reproducible phenotype in HepG2 hanging drop spheroids. [ABSTRACT FROM AUTHOR]