Drug-induced liver injury (DILI) is an adverse drug reaction, and is the most common cause of acute liver failure in the US. DILI is a big problem in drug discovery, as it frequently causes approved drugs to be withdrawn from the market.
Some drugs are at high risk of causing DILI because they inhibit the activity of cytochrome P450 (CYP), a group of enzymes that metabolize drugs. CYP inhibition reduces the metabolism rate of other drugs, increasing drug levels to toxic amounts that may trigger DILI. On the other hand, drugs that induce CYP activity may increase metabolism of other drugs and reduce their efficiency. It is therefore important to screen drugs for their effect on CYP activity.
Unfortunately, current models used for preclinical screening are insufficient. Conventional 2D hepatocyte monolayers have limited cell-cell and cell-extracellular matrix interaction, and thus do not accurately represent native tissue environment. Animal models are another option, but they are expensive, slow and often do not reflect the biology of humans. The recent emergence of 3D hepatocyte cultures may provide a solution, due to their high production efficiency and closer representation to the human liver.
In a recent study, Desai et al. developed a method to test for CYP activity using magnetic 3D cell culture.
The 3D cell culture was achieved by mixing thawed hepatocytes with magnetic nanoparticles that attach to the cell membrane. Small magnets were then placed beneath the plate, attracting the magnetized cells to the bottom to form a spheroid. As the cells aggregate, cell-cell interactions stimulate the cells to build a 3D environment that resembles native liver tissue.
The authors treated 3D spheroids with CYP inducers or inhibitors, and examined CYP activity using the P450-Glo™ CYP1A2 Induction and Inhibition Assay (Cat.# V8421). The 3D spheroids responded to treatment similarly to 2D cells, although baseline CYP activity was higher in 3D spheroids. An advantage of the P450-Glo™ Cell-Based Assays is that they are nonlytic and will allow multiplexing with a cell viability assay. Therefore, using the same cells, the authors were also able to compare cell viability of 3D and 2D cells. This was done using the CellTiter-Glo® 3D Luminescent Cell Viability Assay (Cat.# G7570), which is designed to penetrate large spheroids and has increased lytic capacity, resulting in accurate determination of viability. They found no significant difference in cell viability between 3D and 2D cells.
The goal of this study was to demonstrate the ability to assay CYP activity in 3D hepatocyte spheroids. The authors successfully assembled 3D spheroids that can be used for high-throughput preclinical drug screening, which may help reduce incidences of DILI in the future.