Fresh vs. Frozen
In today’s competitive environment, time and predictability are essential. Promising drugs may save or improve the lives of patients. In addition, the financial implications of being the first to file a promising new chemical entity (NCE) cannot be underestimated.
In the race to succeed, fresh hepatocytes present a number of challenges for the researcher. Freshly isolated hepatocytes may not be readily available due to reliance on liver donation. This unpredictability may slow the testing of NCEs and may require staff to remain on call for a liver.
Liver resects from biopsies may improve availability but are potentially dangerous as they do not include full serology reporting. In contrast, fully characterized cryopreserved hepatocytes, like those from Celsis In Vitro Technologies, can be immediately procured in large inventories and stored at the laboratory, controlling the scheduling of studies and accelerating time to market. For example, standard induction studies typically may be completed 50% faster (Figure 1).
Cryopreserved hepatocytes may be pre-characterized for enzyme activities, genotypes, and for applications like induction or transport, representing a second major advantage over fresh products. In fact, cryopreserved products may be obtained to meet specific donor requirements while maintaining high levels of viability, confluence, or activity. Large inventories and a minimum five-year shelf life allow researchers to repeat tests at future dates with no difference in product performance. Likewise, research being conducted at multiple sites can draw from the same product lot for consistent, simultaneous research worldwide.
Cryopreserved hepatocytes, however, are sensitive to storage conditions, thawing and plating procedures, and culture maintenance. To mitigate any storage damage, cryopreserved hepatocytes must be stored at less than -150°C. Cryo-plateable and cryo-suspension hepatocytes must be thawed according to the manufacturer’s instructions using appropriate medium. Cryo-plateable hepatocytes also must be seeded uniformly at the optimal cell density, which can affect their plating efficiency. When treated properly, cryo-plateable hepatocytes can be used as if they were freshly isolated hepatocytes.
The use of cryopreserved hepatocytes is recognized as equivalent to using freshly isolated hepatocytes. Acknowledging this trend, the U.S. FDA drafted a Guidance for Industry in 2006 advising that cryopreserved tools are a viable and acceptable alternative to fresh research products, especially in metabolism, toxicity, and drug-drug interaction testing. Many laboratories have demonstrated cryopreserved equivalence to freshly isolated hepatocytes.
As such, several large pharmaceutical companies have adopted cryopreserved hepatocytes as their primary source for stability, transport, and induction studies. As researchers realize the benefits of cryopreserved hepatocytes that can be selected, reserved, and scheduled in advance, an expanding range of applications will be employed like high-throughput screening and high-content screening.