Human hepatocytes: Isolation, cryopreservation and applications in drug development
Introduction
Primary cultures of hepatocytes represent an experimental tool that has been used extensively in biomedical research, both in academia as well as for commercial purposes such as drug development. The most exciting advances are the successful isolation, culturing, and cryopreservation of hepatocytes from human livers. Human hepatocytes are used routinely in drug development as an experimental model for the evaluation of key human-specific drug properties such as metabolic fate, drug–drug interactions, and drug toxicity. The applications range from the early screening the most appropriate new chemical entities for further development, to the determination of key drug properties for New Drug Applications (e.g. drug–drug interactions) to U.S. FDA.
Successful application of human hepatocytes in drug development requires a thorough understanding of the strengths and weaknesses of this valuable experimental system. This review is an effort to present a comprehensive review on the state-of-the-art of the isolation, cryopreservation, and applications of human hepatocytes in drug development, with emphasis on the research performed in our laboratories in the past 20 years.
Section snippets
Human hepatocyte isolation
One of the major advances in human hepatocyte technology is the availability of human livers for research. In the United States, livers procured but not used for transplantation are allowed to be used in research. The major reasons that procured livers are not used for transplantation are as follows:
- 1.
unavailability of a matched recipient;
- 2.
physical damage to the liver;
- 3.
pre-existing liver diseases;
- 4.
breach of sterility during the procurement process;
- 5.
high liver fat content;
- 6.
inappropriate age (too young
Cryopreservation
Hepatocytes, especially human hepatocytes, are now routinely used after they are cryopreserved [7], [8]. The general procedures for hepatocyte cryopreservation have not deviated extensively from the original procedures [9]. Via the use of equipments to control freezing rates (e.g. programmable control-rate freezer) and appropriate cryopreservation agents (e.g. dimethyl sulfoxide), hepatocytes now can be stored in liquid nitrogen (lower than −150 °C) for an extensively time period (years) with
Application of human hepatocytes in drug development
The key areas in drug development that can benefit from the use of human hepatocytes are drug metabolism, drug–drug interaction, and drug toxicity evaluation.
Conclusions
In the past decade, human hepatocytes have been used increasingly in drug development. The experience as of now is that relevant information can be obtained with this experimental system, including human-specific drug properties such as metabolic stability and fate, drug–drug metabolizing enzyme interactions, drug–transporter interactions, and drug toxicity. The availability of human hepatocytes for research has been dramatically increased due to the increased availability of commercial sources
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