Primary human hepatocytes can show significant lot-to-lot variability due to the nature of the isolation procedures and hepatocyte function. The lot-to-lot variability can be attributed to donor-to-donor variability, inconsistency in the health of the tissue, and treatments that the donor may have undergone near the time of donation. As a result, hepatocyte lots must be characterized for many different functions in order to provide users with important supplemental data about the health of the cells in addition to the donor demographics.
Each hepatocyte lot should be characterized for post-thaw viability and viable cell yield. Additionally, the cells must be characterized for their ability to form a monolayer in culture. Primary hepatocytes maintain their function for a much longer time when they are able to form tight junctions with other hepatocytes. Therefore, the plating efficiency should be an important factor in selecting an appropriate lot of hepatocytes. As previously noted, primary hepatocytes have many applications, but drug metabolism studies tend to be the most common.
Hepatocytes to be used for basal metabolic activity measurements and metabolite identification should also be evaluated for metabolic competency in terms of the common CYP enzymes, such as CYP1A2, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP3A, which are typically involved in the metabolism of pharmaceuticals. The regulatory agencies have issued official guidance about the performance of drug interaction studies using hepatocytes in vitro. A hepatocyte lot should demonstrate a relevant level of induction of CYP1A2, CYP2B6, and CYP3A4 in response to positive control inducers. (13)
For disease modeling and other applications, the recommended approach for the selection of the best lot is to test several different batches in a pilot assay to determine which is most suitable for your specific application.