Varigenix® Hepatocyte Panels 

Charles River, in association with Varigenix^®, now offers a new tool that has been validated to study the impact of genetic variation in pharmacogenomics and toxicogenomics. Varigenix^® hepatocyte panels express genetic variability comparable to human populations and are available as four products. Each of the four hepatocyte panels consist of ~1 million cryopreserved suspension hepatocytes.

The first panel is currently available for purchase and other panels will be produced to meet market demand. These hepatocyte panels are designed to facilitate evaluation of the importance of genetic variation in drug metabolism, drug effectiveness, drug toxicity, environmental toxin interactions, and many other biomedical uses. These panels include:

To validate the value of these panels, studies were performed on acetaminophen. Acetaminophen is one of the most hepatotoxic drugs in clinical use and individuals show significant variation in their response to it. Nevertheless, previous research has not been able to establish how genetic variation influences the effect of acetaminophen on hepatocytes in vitro (1).

Using Varigenix^® hepatocyte panels, it is now possible to clearly demonstrate genetic variation in individual responsiveness to in vitro treatment with 0.5 mM acetaminophen for 9 hours (6). Relative to untreated controls, approximately half of the cell panel shows cytotoxicity that ranged from +8 to +170 LDH/DNA units, whereas the other half of the cell panel shows cytoprotection from the typical decrease in viability that occurs during culture. The cytoprotective effect ranged from -9 to -42 LDH/DNA units. The values in the following figure are expressed as [treated LDH as RFU/ DNA as ng/mL] - [untreated LDH as RFU/ DNA as ng/mL)].

Published references provide evidence that cytoprotective and cytotoxic effects of acetaminophen have previously been defined in other situations (2-5).

When this bimodal acetaminophen viability trait was evaluated using the quantitative trait locus [QTL] mapping function of the GeneNetwork system, a significant QTL was detected on chromosome 6 at ~136 mB as shown in the figure on the right.

Of the genes associated with this QTL, 11 had cis characteristics. They include Cdkn1b, Dusp16x, Pde6h, Plbd1, Arhgdib, Art4, Gpr19, Hebp1, Lrp6 and Pik3c2 . Of these, Lrp6 is implicated as the key regulatory quantitative trait gene (QTG) because it was the most highly co-expressed with the acetaminophen viability trait and because a recent abstract reported that ablation of the Lrp5 and Lrp6 genes leads to resistance to acetaminophen toxicity (7). These findings predict that a member of the Wnt-Lrp6 signaling pathway will be of significance in acetaminophen toxicity in man. 

The use of Varigenix^® hepatocyte panels not only makes it possible to detect excellent genetic variation in viability responses to acetaminophen treatment in vitro, but also makes it possible to define significant genetic mechanisms with the potential to regulate this bimodal viability effect of acetaminophen. As a result, it is anticipated that Varigenix^® hepatocyte panels will be equally valuable in other pharmacogenomic and toxicogenomic studies.

To obtain additional information on Varigenix^® hepatocyte panels that are available from Charles River Laboratories and data analysis services that are available from Varigenix^®, please contact:

Robert E. Scott, M.D.
Varigenix, Inc.
901-268-8285
res@varigenix.com

or

Aidan Synnott, Ph.D.
Charles River Laboratories, Inc.
919-462-8338
Aidan.Synnott@crl.com

References:

1. Martinez SM, Bradford BU, Soldatow VY, Kosyk O, Sandot A, Witek R, Kaiser R, Stewart T, Amaral K, Freeman K, Black C, LeCluyse EL, Ferguson SS, Rusyn I. "Evaluation of an in vitro toxicogenetic mouse model for hepatotoxicity." Toxicol Appl Pharmacol. 249:208-16 (2010). 

2. Moyer AM, Fridley BL, Jenkins GD, Batzler AJ, Pelleymounter LL, Kalari KR, Ji Y, Chai Y, Nordgren KK, Weinshilboum RM. "Acetaminophen-NAPQI hepatotoxicity: a cell line model system genome-wide association study."  Toxicol. Sci. 120:33-41 (2011).

3. Jaeschke H, McGill MR, Williams CD, Ramachandran A. "Current issues with acetaminophen hepatotoxicity--a clinically relevant model to test the efficacy of natural products." Life Sci. 88:737-45 (2011).

4.  Nouri M, Pipelzadeh M.H., Rashidi I, Dara T. "A Comparative Study upon the Cytoprotective Effect of Prostaglandin F2 and Acetaminophen on Indomethacin and Absolute Alcohol-induced Gastric Damage." International Journal of Pharmacology. 3:227 (2007).

5.Ota S, Razandi M, Sekhon S, Terano A, Hiraishi H, Ivey KJ. "Cytoprotective effect of acetaminophen against taurocholate-induced damage to rat gastric monolayer cultures." Dig Dis Sci. 33:938-44 (1988). 

6. RW Williams, RM Kaiser, S Hoynowski and RE Scott. "New high-throughput in vitro hepatocyte panels detect drug-genotype interactions: High genetic diversity in response to acetaminophen." Society of Toxicology Meeting Abstract. #2774, March 2012.