PXB-mice and PXB-cells offer a highly physiologically relevant liver model for in vivo and in vitro research, respectively. They have been shown to have versatile applications in studies, ranging from hepatitis B virus (HBV) infection modeling to epigenetic research.
In this round-up, we look back on the past year to showcase some of the most interesting and impactful research utilizing PXB-mice and/or PXB-cells, spanning disease modeling, drug metabolism, and epigenetic editing.
Disease modeling
Understanding human liver diseases requires highly accurate modeling of the human liver environment. However, traditional in vitro and in vivo models often fail to replicate the liver’s complexity, limiting their relevance in translational studies.
Translational models, on the other hand, can offer a more human-relevant platform to investigate disease mechanisms and allow researchers to better understand disease progression and treatment. PXB-mice, transplanted and engrafted with primary human hepatocytes, are able to recapitulate the complex structure and functioning of the human liver. PXB-cells—freshly isolated human hepatocytes—retain stable expression of human-specific enzymes and transporters, have physiologically relevant structures like bile canaliculi, and are stable in long-term culture, making them a valuable in vitro model.
Chronic hepatitis B virus (HBV) infection
Chronic HBV infection is a major global health concern, putting people at risk of death from cirrhosis and liver cancer. The chronic infection is driven by the persistence of covalently closed circular DNA (cccDNA) in the nucleus of infected hepatocytes1. Currently, no therapies can prevent cccDNA production in chronic HBV infection2, and identifying dynamics and quantities of cccDNA in patients remains difficult due to the need for invasive liver biopsies1.
Recent research using PXB-models has sought to increase our understanding of chronic HBV infection and identify potential treatments.
Kitagawa et al (2024): Multiscale modeling of HBV infection1
Kitagawa et al aimed to develop a non-invasive method of estimating levels of intrahepatic cccDNA, using both PXB-cells and PXB-mice by constructing a multiscale mathematical model. Using specific viral markers in serum samples, the mathematical model was roughly able to predict the amount and dynamics of intrahepatic cccDNA. Interestingly, cccDNA had a shorter half-life in the PXB-cell model than in the PXB-mice, which the mathematical model predicted. This suggests the mathematical model could be a valid method of predicting the cccDNA dynamics in humans.
Okada et al (2024): siRNA therapeutic targeting HBV2
Okada et al aimed to investigate the potential of dedicator of cytokinesis 11 (DOCK11), a molecule implicated in maintaining cccDNA, as a potential therapeutic target for chronic HBV infection. To do so, they assessed whether DOCK11 inhibitors suppress HBV cccDNA production in a PXB-mouse model of HBV infection.
The results were promising: inhibition with LNP-encapsulated DOCK11-siRNA successfully suppressed HBV cccDNA in infected PXB-mice. These findings highlight both the therapeutic potential of DOCK11 inhibition and the utility of the PXB-mouse model as a physiologically relevant system to evaluate HBV infection treatment strategies.
Fatty liver disease
Metabolic-associated fatty liver disease (MAFLD), formerly known as nonalcoholic fatty liver disease (NAFLD), and its more advanced form, metabolic-associated steatohepatitis (MASH, previously NASH), are becoming increasingly prevalent,3 with MASH now the leading cause of chronic liver disease worldwide.4 Despite the growing incidence, there are few treatment options available—largely due to the complex and incompletely understood pathogenesis of the disease, and a lack of predictive, human-relevant preclinical models.3,4
Studies by Ichikawa et al (2024) and Wang et al (2023) aimed to broaden our knowledge of MAFLD and MASH using PXB-mouse models.
Ichikawa et al (2024): Multi‑omics analysis of a PXB-mouse fatty liver model3
To better understand MAFLD pathogenesis, Ichikawa and colleagues developed a fatty liver mouse model by feeding PXB-mice a high-fat Gubra-Amylin NASH diet, and administered human growth hormone (hGH) to observe its effect on lipid metabolism.
Multi-omics analysis, histological findings, and ultrasound imaging revealed coordinated changes in gene expression, protein, and metabolite profiles associated with fatty liver in the PXB-mice. While the hGH treatment reduced some signs of fatty liver, it did not significantly impact the liver/kidney ratio, suggesting that it does not fully relieve the impact of the high-fat diet. Overall, the findings demonstrate the potential of PXB-mice as a robust model for investigating the complex regulation and pathogenesis of MAFLD.
Wang et al (2023): siTAZ therapy for NASH-induced fibrosis4
Wang et al explored whether PXB-mice would be valuable model for testing hepatocyte-targeted siRNA therapies.
In PXB mice fed a NASH-inducing diet, treatment with GalNAc-siTAZ was found to reduce liver inflammation and fibrosis compared to a control. This study reinforces the PXB-mouse’s value in modeling human hepatic diseases, and its potential role in advancing preclinical testing of novel NASH treatments.
Intrahepatic cholangiocarcinoma (iCCA)
Intrahepatic cholangiocarcinoma (iCCA) is a relatively rare, but highly lethal, cancer that develops in the bile ducts of the liver.5 Presently, the cellular origin of iCCA is uncertain, and a hepatocytic origin is not considered in clinical diagnosis, classification, or therapy.5 This gap in understanding poses a challenge for therapeutic development, so recent research aimed to shed light on the cellular origins of this disease.
Hsu et al (2024): Modeling intrahepatic cholangiocarcinomas5
To investigate the possibility of a hepatocyte origin, Hsu et al transduced primary human hepatocytes (PHHs) with lentiviral vectors expressing oncogenes, and transplanted them into livers of cDNA-uPA/SCID (PXB-mouse host animals) and FRGN mice.
Following transplantation, the mice rapidly developed tumors that closely mimicked the morphology and the protein and gene expression profiles of patient-derived iCCAs. These findings provide direct evidence for a hepatocyte origin of peripheral mass-forming (small bile duct type) iCCA and highlight the potential of the PXB-mouse host animal as a platform for generating and studying human liver cancer.
Drug metabolism
Predicting human drug metabolism, clearance, and drug-drug interactions (DDIs) has been a significant hurdle in preclinical research, with there being a need for more reliable in vitro and in vivo models.
Drug metabolism research has demonstrated that PXB-cells and PXB-mice could offer an accurate model to help bridge the gap between preclinical and clinical research.
Feng et al (2024): Predicting hepatic drug transporter-mediated drug-drug interactions (DDIs)6
Drug transporters play an important role in the absorption, distribution, and elimination of numerous drugs. In the liver, organic anion-transporting polypeptide 1B (OATP1B) is a key uptake transporter that can handle a broad range of substances. Inhibiting OATP1B can lead to clinically significant DDIs, but conventional preclinical animal models struggle to predict these interactions due to species differences in substrate specificity and transporter abundance.
Feng at al investigated whether PXB-mice could offer a more valuable model for DDI prediction. To do so, they measured the exposure increases (blood AUC and Cmax) of ten OATP1B substrates, including rosuvastatin, pravastatin and valsartan, in PXB-mice upon co-administration with rifampin (an OATP1B-specific inhibitor), and compared the data to the observed DDIs between OATP1B substrates and single-dose rifampin in humans.
Their findings showed that the mice were successfully able to predict DDIs mediated via the liver OATP1B transporter in humans, including complex DDIs involving inhibition of OATP1B, CYPs and P-gp, for the majority of OATP1B substrates evaluated.
Karlsson et al (2025): Predicting human drug metabolism7
Having a good understanding of how a drug will be metabolized in humans, ahead of clinical trials, is crucial for informing dosing, and for identifying and mitigating potential safety risks. However, current in vitro and in vivo systems often fail to capture the nuances of human metabolic processes, complicating metabolism predictions.
Karlson et al evaluated whether the PXB-mouse could accurately mimic human metabolic profiles, and therefore offer better predictions of drug metabolism. They compared circulating and renally excreted metabolites in PXB-mice to human in vivo data across 12 small molecule drugs: atorvastatin, bosentan, cerivastatin, epristeride, glipizide, irbesartan, moxifloaxcin, PF-05089771, pitavastatin, repaglinide, telmisartan, and tesaglitazar. Their findings demonstrated that, for the majority of the drugs, more than 75% of the human plasma metabolites were detected, indicating that PXB-mouse metabolic patterns closely matched human in vivo data.
Kurniawan et al (2024): Gut-liver crosstalk in drug metabolism8
The small intestine and liver are important in determining the fate of orally administered drugs. Since these organs are interconnected through enterohepatic circulation, it is assumed that there is crosstalk between the organs, mediated through circulating factors—crosstalk that may affect drug metabolism. However, the mechanisms of such crosstalk remain unclear.
To investigate crosstalk mechanisms, Kurniawan et al cocultured PXB-cells with iPSc-derived intestinal cells in a microphysiological system (MPS) — a ‘liver-on-a-chip’ — designed to model the organ interactions in vitro. The system revealed that there was crosstalk between the organ models, as the PXB-cells secreted bile acids that stimulated intestinal lipoprotein release, which in turn was taken up by hepatocytes and enhanced cytochrome P450 activity. This demonstrates that using PXB-cells in MPSs, with appropriate features and cell sources, can be used to study novel crosstalk between organs.
Miyake et al (2025): Prediction of drug disposition for uridine diphosphate glucuronosyltransferase (UGT) substrates9
Assessing drug clearance and DDIs is essential for understanding drug pharmacokinetics (PK). Reliable predictions of drug disposition mediated by metabolizing enzymes, particularly UGT, require highly accurate in vitro and in vivo models.
Miyake et al tested the ability of PXB-mice to model the clearance and DDIs of seven UGT substrates, with and without the UGT inhibitor probenecid, to investigate whether they could offer a predictable drug clearance model. The PXB-mice were accurately able to predict the clearance and DDIs of UGT substrates, both with and without probenecid, supporting their use as a translational model for assessing UGT substrate PK and the impact of co-administered inhibitors.
Scheidecker et al (2024): Organ-on-a-chip models for liver function10
To explore the suitability of PXB-cells in organ-on-a-chip models, Scheidecker et al compared static monoculture with static co-culture and dynamic co-culture of PXB-cells with sinusoidal endothelial cells.
The results showed that drug-metabolizing enzymes were best maintained under static conditions with physiological oxygen levels, while perfusion culture was more conducive to liver tissue regeneration and long-term maintenance. These findings support the use of PXB-cells in co-culture models.
Epigenetic editing
Beyond disease modeling and PK studies, PXB-mice and PXB-cells have recently been used in epigenetic research. Epigenetic editing offers a promising approach to silencing disease-causing genes altering the underlying DNA sequence.
To evaluate the long-term impact, reversibility, and translational relevance of these approaches, human-relevant in vivo and in vitro models are essential.
Tremblay et al (2025): Epigenetic editing of PCSK911
Tremblay et al aimed to test the effectiveness and durability of an epigenetic editor in silencing PCSK9 to reduce low-density lipoprotein levels. The epigenetic silencing of PCSK9 in PXB-cells resulted in significantly reduced PCSK9 secretion and gene expression, which was consistent with targeted PCSK9 methylation. In a humanized mouse model, PCSK9 silencing endured for at least a year and was shown to be reversible.
Notably, these findings were validated in cynomolgus monkeys, where a single administration of the epigenetic editor potently and durably decreased circulating PCSK9 protein levels by approximately 90% with concomitant reduction in low-density lipoprotein cholesterol levels by approximately 70%. These results demonstrate that PXB-cells can be a useful model to predict the efficacy of therapeutics in vivo and underscore the therapeutic potential of durable and reversible epigenetic editing.
Accurate models with wide-reaching impact
Research in the past year has highlighted the value of PXB-mice and PXB-cells as powerful tools for disease modeling, drug metabolism studies, and gene editing research. The ability of these models to closely mimic human liver function makes them invaluable for generating reliable data in drug development and disease research.
As the demand grows for more predictive in vivo and in vitro systems, PXB-models are well positioned to play a greater role in bridging the gap between preclinical research and clinical outcomes. Contact us to find out how PXB-mice and PXB-cells can support your next study!
References
- Kitagawa et al. Multiscale modeling of HBV infection integrating intra-and intercellular viral propagation to analyze extracellular viral markers. PLOS Computational Biology 20.3 (2024): e1011238.
- Okada et al. Lipid nanoparticle-encapsulated DOCK11-siRNA efficiently reduces hepatitis B virus cccDNA level in infected mice. Molecular Therapy Methods & Clinical Development 32.3 (2024).
- Ichikawa et al. Multi-omics analysis of a fatty liver model using human hepatocyte chimeric mice. Scientific Reports 14.1 (2024): 3362.
- Wang et al. Hepatocyte-targeted siTAZ therapy lowers liver fibrosis in NASH diet-fed chimeric mice with hepatocyte-humanized livers. Molecular Therapy Methods & Clinical Development 31 (2023).
- Hsu et al. Human hepatocytes can give rise to intrahepatic cholangiocarcinomas. Gastroenterology 167.5 (2024): 1029-1032.
- Feng et al. Utility of Chimeric Mice with Humanized Livers for Predicting Hepatic Organic Anion-Transporting Polypeptide 1B–Mediated Clinical Drug-Drug Interactions. Drug Metabolism and Disposition 52.10 (2024): 1073-1082.
- Karlsson, et al. Investigation of Biotransformation Pathways in a Chimeric Mouse with a Humanized Liver. International Journal of Molecular Sciences 26.3 (2025): 1141.
- Kurniawan et al. Gut–liver microphysiological systems revealed potential crosstalk mechanism modulating drug metabolism. PNAS nexus 3.2 (2024): pgae070.
- Miyake et al (2025). Quantitative prediction of drug disposition for uridine diphosphate glucuronosyltransferase substrates using humanized mice
- Scheidecker et al (2024). Mechanobiological stimulation in organ‐on‐a‐chip systems reduces hepatic drug metabolic capacity in favor of regenerative specialization
- Tremblay et al. A potent epigenetic editor targeting human PCSK9 for durable reduction of low-density lipoprotein cholesterol levels. Nature Medicine (2025): 1-10.