Pharmaceutical researchers are continuously searching for the ideal model to understand the biotransformation and clearance
of their novel drug compounds. The use of in vitro models in early-stage drug development can facilitate elimination of unsuitable new chemical entities (NCEs) before they
ever reach clinical trials, the most costly and resource-intensive portion of the drug development process. The goal is to
create in vitro models that best represent physiological conditions and retain stable cellular functions to better predict in vivo effects.
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Liver cell co-cultures can offer a more comprehensive in vitro model to study the effects of intercellular signaling on xenobiotic metabolism. Non-parenchymal cells (NPC) of the liver
such as Kupffer, sinusoidal, endothelial, and stellate cells can be co-cultured with hepatocytes to more accurately mimic
in vivo conditions.
Kupffer cells are a type of macrophage located within the liver sinusoid that are of particular interest because of their
key role in the modulation of drug-metabolizing enzymes following immunological response. Hepatocyte/Kupffer cell co-cultures
can be seeded at ratios with increasing Kupffer cell content to allow investigators to compare inflammation versus normal-state
response. Stimulation of the co-cultures with lipopolysaccharide (LPS) results in the release of a variety of soluble factors,
such as nitric oxide (NO) or pro-inflammatory cytokines, such as IL-6 and TNF-α. The response to inflammation and infection
can lead to altered gene expression, down-regulation of cytochrome P450 (CYP) enzymes, and depression of the mechanisms underlying
The use of hepatocyte/Kupffer cell co-cultures is also important in the screening of therapeutic proteins and biologics. These
drugs are more heterogeneous in composition, follow different pathways of elimination, and have greater potential to elicit
an immune response. Their impact on CYP enzyme suppression and the potential to cause small molecule toxicity should be thoroughly
studied before reaching clinical trials.
Other advantages to culturing hepatocytes with NPCs are longer maintenance in culture and higher liver-specific function.
Fresh and cryopreserved hepatocytes and non-parenchymal cells from the same donor or pool of donors allow researchers to reconstitute
compatible cells in a physiologically relevant format that is most appropriate for their experiment.