Transporter Certified™ Hepatocytes

Translating In Vitro Knowledge into In Vivo Solutions

High quality cells are critical for reliable cell-based, assay results. Commercially available hepatocytes vary measurably in quality, phenotype, and function, though these differences may not always be visibly evident. In other words, hepatocytes that appear to be the same and express the same level of proteins may not have the same functionality (Figure 1).

Figure 1. A visual comparison of Transporter Certified™ hepatocytes to other commercially available cells that were found to be unacceptable. Cells were plated, overlaid and cultured under conditions demonstrated to maintain transporter expression, localization and function. All plate sources had similar protein values 0.85±0.04 vs. 0.84±0.08 and visual inspection demonstrated no remarkable differences. However, after certification testing, the other commercially available hepatocytes showed little to no functional activity.

Importance of Transporter Certified™

In hepatocytes with no functioning efflux, toxicity can be observed at low, non-physiologic concentrations because uptake continues to occur (Figure 2). Transport Certified hepatocytes have characterized, physiologic uptake and efflux transport, ensuring proper intracellular concentrations. Our kits and contract services use Transporter Certified™ hepatocytes that provide a standard of hepatocyte function and ensure reproducibility from experiment to experiment. Transporter Certified™ hepatocytes can be used for transporter studies, drug interaction experiments, intracellular concentration determination, induction, metabolism, hepatotoxicity or any experiment where transporters and in vivo correlation are important.

Figure 2. These graphs illustrate the importance in using Transporter Certified™ hepatocytes. Using conventionally plated hepatocytes that are not Transport Certified™, potent toxicity is observed, however in vivo, neither compound is considered toxic at these concentrations. Using sandwich-cultured Transporter Certified™ hepatocytes, no toxicity was observed over the concentrations tested. For the conventionally plated hepatocytes, since there was no biliary efflux but functioning uptake, concentrations inside the cells reached toxic levels at low exposures. Therefore, using Transporter Certified™ hepatocytes, with functioning uptake, biliary and basolateral efflux, you can obtain more clinically-relevant results.

What is the Transporter Certified™ process?

We perform a rigorous evaluation of human cryopreserved hepatocytes that includes a third party plating and viability assessment as well as phase II activity. Functionally, we quantitate the level of transporter activity using drug reference probes that focus on uptake, biliary efflux, and basolateral efflux activities. In addition, we assess the inhibition of these transporters as well as the intracellular concentrations of these same probes. Because the intracellular concentration is the result of all of the transport activities working in concert, these values reflects the balance of these functions together. We express this as a Kp ratio that is the concentration of compound inside the cell to the concentration on the outside. A Kp ratio of 1 indicates that the concentration inside the cell is the same as outside the cell. Activities that are high or low may still have an appropriate Kp ratio. When uptake and efflux are out of balance however, the Kp ratio can deviate dramatically, and in some cases, the range of values can be as high as 100-fold different indicating that transporter activity is not physiologically relevant. These cells are not Certified and should not be used for any in vivo predictive experiments.

We assess bile acid profiles within the cell since functioning hepatocytes synthesize and transport bile acids. We measure the various species and verify that the correct ratios of bile acid conjugates are observed. Finally, this information is compared to an extensive historical database and a defined range of performance is provided for each certification (Figure 3).

Figure 3. This graph highlights human hepatocytes that were not Certified due to low uptake activity. Rosuvastatin, primarily taken up by OATP1B3, was found to have little to no biliary clearance in these cells. Human hepatocytes that were Certified and maintained physiologic uptake, biliary and basolateral efflux, showed biliary clearance of rosuvastatin that was similar to what is observed in vivo.

The following laboratories have cryopreserved human hepatocytes available that have been Certified to culture out to 5 days and maintain uptake, biliary and basolateral efflux transporters as well as proper bile cannuliculi formation. Our Transporter Certified™ Cryopreserved Hepatocyte Partners include:

How do I get Transporter Certified™ hepatocytes?

Hepatocytes and hepatocyte kits are widely available commercially, however, only our Transporter Certified™ partners above have allowed assessment of their product to verify quality.

Request Transporter Certified™ hepatocytes from your vendor or contact us for more information!

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*B-CLEAR® is covered by US Patent 6,780,580 and other worldwide patents issued & pending.