3D spheroid culture as a tool for studying drug metabolism

Significance of the Topic

The liver is the primary organ responsible for drug metabolism, and primary human hepatocytes are the gold standard for in vitro metabolism studies. Three-dimensional (3D) spheroid cultures of cryopreserved human hepatocytes offer improved cellular architecture and extended phenotypic stability compared with traditional two-dimensional (2D) monolayers, making them attractive for drug discovery and safety assessment.

Study Objectives and Overview

This application note aimed to directly compare metabolic activities of key cytochrome P450 enzymes in 2D versus 3D human hepatocyte culture models. Six probe substrates covering CYP1A2, CYP2B6, CYP2C9, CYP2D6 and CYP3A4 were incubated in both formats to evaluate the assay window, metabolite formation rates and overall utility of 3D spheroids for drug metabolism studies.

Methodology and Instrumentation

• Cell Culture
    • 3D spheroids formed from 3,000 cryopreserved human hepatocytes per well in ultra-low attachment plates. Media changed every 48–72 hours over a nine-day period.
    • 2D cultures seeded on collagen-coated 96-well plates at 50,000 cells per well, following established protocols.
• Metabolic Incubation
    • On day 10, both cultures were exposed to Williams’ E medium with six probe compounds: dextromethorphan (150 µM), midazolam (100 µM), phenacetin (200 µM), bupropion (500 µM), testosterone (400 µM) and tolbutamide (500 µM).
    • Incubation times: 2 hours for most substrates in 2D, extended to 8 hours in 3D; tolbutamide: 4 hours (2D) and 16 hours (3D).
• LC-MS Analysis
    • Separation on a Hypersil BDS C18 column using water/0.1% formic acid (A) and ACN/0.1% formic acid (B) gradient with Vanquish™ Flex UHPLC.
    • Detection on Q Exactive™ Plus Hybrid Quadrupole-Orbitrap MS (HESI-II probe, polarity switching). Full-scan resolution at 35,000 and data-dependent HCD MS2 for metabolite identification and quantitation.

Main Results and Discussion

High-resolution mass spectrometry readily detected all target metabolites from single 3D spheroids despite the lower cell count. When normalized to cell number and incubation time, 3D cultures exhibited equal or higher metabolite formation rates for CYP2D6 (dextrorphan), CYP3A4 (1-hydroxymidazolam), CYP1A2 (acetaminophen), CYP2B6 (hydroxybupropion), CYP3A4 (6β-hydroxytestosterone) and CYP2C9 (4-hydroxytolbutamide) compared with 2D monolayers. These findings align with previously observed upregulation of CYP gene expression and albumin secretion in 3D spheroids.

Benefits and Practical Applications

• Enhanced Phenotypic Stability: 3D spheroids maintain hepatic functions over extended culture periods.
• Sensitive Metabolism Assays: Robust detection of low-abundance metabolites enables reliable CYP activity profiling.
• High-Throughput Capability: Small spheroid size permits parallel screening of multiple compounds with reduced cell usage.

Future Trends and Opportunities

Advancements may include integration of 3D hepatocyte spheroids with non-parenchymal cell types for more complex liver models, organ-on-chip platforms for dynamic flow conditions, and application to personalized medicine by using donor-specific spheroid cultures. Coupling with high-content imaging or transcriptomic profiling could further enrich mechanistic insights into drug metabolism and toxicity.

Conclusion

The study demonstrates that 3D primary human hepatocyte spheroids constitute a powerful and efficient platform for in vitro drug metabolism research. They offer improved enzyme expression, extended longevity and comparable or superior metabolic activity relative to conventional 2D cultures, supporting their use in high-throughput ADME screening.

Reference

1. Thermo Fisher Scientific. User Guide: Cryopreserved 3D-Spheroid Qualified Human Hepatocytes. Pub. No. MAN0018280.
2. Thermo Fisher Scientific. Thawing and Plating Cryopreserved Hepatocytes Protocol.
3. Thermo Fisher Scientific. Primary Human Hepatocyte 3D Spheroids for Studying Hepatic Function and Drug Toxicity. Poster.