Traditional animal rodent models, such as Swiss -Webster mice and Sprague-Dawley rats, have sometimes failed to predict toxicity and pharmacokinetic/pharmacodynamic (PK/PD) behavior of xenobiotics in humans1. Conversely, hepatotoxicity in a rodent study does not always translate into similar toxicity in human subjects. Humanized liver rodent models are immunodeficient animals in which the native liver has been ablated and then engrafted with human hepatocytes, which proliferate to restore the functioning liver. These models offer an opportunity for advanced evaluation of new chemical entities for human specific hepatotoxicity. Humanized models are also useful for infectious disease studies such as hepatitis, which infect and replicate primarily in human hepatocytes but not in rodent2.
Hera has established humanized liver mice as well as has the ability to run toxicology, PK/PD and efficacy studies using rodent models as demonstrated below.
Hera is developing the SRG Platform for humanizing the rat liver which is predicted to have many advantages over humanized liver mice, including more background toxicology data on the rat, serial blood draws, and ~10x more hepatocytes
Creating Humanized Liver Mice
Confirming humanization by measurement of human albumin
Human albumin is detected in the serum of TK-NOG liver-humanized mice. Blood was collected every 2 weeks starting at 2 weeks post-transplant of primary human hepatocytes in TK-NOG mice. Each line represents a single animal. 1-4, males. 5-6, females. Human albumin levels correlate with level of human chimerism (Hasegawa et al., 2011).
Detection of human hepatocytes within the chimeric TK-NOG liver.
Left: H&E staining of liver sections confirms the presence of human cells, which are less eosinophilic than mouse hepatocytes and appear pale in comparison (arrow). Right: immunohistochemistry for human albumin (brown staining).
Example in vivo hepatotoxicity data (non-humanized rats): clinical pathology
Alpha-naphthyl isothiocyanate/ANIT study (right): 75mg/kg dosed IP on days 0, 1, 2 (3 doses, analysis 48 hours post-dose). Blood collection via cardiac puncture for clinical pathology on day 3. Liver extracted, fixed, and processed for histopathology on day 3
CCl4 study (left): 5ml/kg dosed PO on days 0, 1 (2 doses, analysis 48 hours post-dose). Blood collection via cardiac puncture for clinical pathology on day 3. Liver extracted, fixed, and processed for histopathology on day 3
Example in vivo hepatotoxicity data (non-humanized rats): histopathology
1. Xu & Peltz (2016) Can Humanized Mice Predict Drug “Behavior” in Humans? Annu. Rev. Pharmacol. Toxicol. 2016. 56:323–38
2. Calattini et al. (2015) Functional and Biochemical Characterization of Hepatitis C Virus (HCV) Particles Produced in a Humanized Liver Mouse Model. The Journal of Biological Chemistry
3. Xu et al (2014). Fialuridine Induces Acute Liver Failure in Chimeric TK-NOG Mice: A Model for Detecting Hepatic Drug Toxicity Prior to Human Testing. PLOS Medicine, 2014. 11(4): e1001628
4. Hall & Geraus. Taconic Biosciences. Latest Advances in Cell and Tissue Engrafted Mice.
5. Azuma, H., et al., Robust expansion of human hepatocytes in Fah–/–/Rag2–/–/Il2rg –/– mice. Nature Biotechnology, 2007. 25(8): p. 903-10
6. Grompe, M., et al., Pharmacological correction of neonatal lethal hepatic dysfunction in a murine model of hereditary tyrosinaemia type I. Nature genetics, 1995. 10(4): p. 453-460.
7. Peltz, G., Can ‘Humanized’ Mice Improve Drug Development in the 21st Century? Trends Pharmacol Sci. 2013. 34(5): p. 255–260.