The need for new liver research tools
Liver diseases dramatically impact patients' quality of life worldwide and account for approximately 2 million deaths per year worldwide, 1 million due to complications of cirrhosis and 1 million due to viral hepatitis and hepatocellular carcinoma 1. In addition, some cases progress to organ failure and require liver transplantation. Therefore, understanding the cellular and molecular mechanisms of liver disease is a research priority.
The problem with current tools
Current approaches include animal testing for drug screening and toxicity; and animal modelling of acquired and genetic liver pathologies.
One of the main problems with these approaches is that differences between animals and humans in liver pathways make the drug discovery and toxicology findings challenging to extrapolate to humans and now necessitate the use of in vitro models of the human liver 2.
IPSCs disease modelling
Stemnovate generates hepatocyte cells from skin fibroblasts and blood cells reprogrammed into induced pluripotent stem cells (iPSCs). These cells have the potential for disease modelling, drug testing, and future cellular therapies 3.
iPSCs have multiple advantages compared with animal testing. First, disease modelling is more accurate when done in humans. Using these cells avoids patients' need for invasive biopsies. Furthermore, iPSCs have self-renewing properties nearly indefinitely. It is incredible that by adding growth factors and small molecules, iPSCs differentiate into liver cells in vitro 4. Therefore liver differentiation allows liver generation from patients with particular backgrounds to study genotype-phenotype relationships. Such a model can be crucial in drug development and modelling liver diseases such as hepatitis B/C viral infections and even cancers.
To differentiate these cells, we induce definitive endoderm to generate hepatic progenitor cells and final maturation to liver cells by adding specific cocktails of growth factors in culture. These cells express albumin, CK18, cytochrome p450 enzymes, alpha-1-antitrypsin (A1AT), and asialoglycoprotein receptor1 and function similar to primary human hepatocytes.
iPSCs can be generated directly from patients with specific diseases and model the natural progression of the disease in vitro, thus making them an ideal tool to model liver diseases. For example, Stemnovate is working with Prof Cliona O'Farrelly at Trinity College (Dublin, Ireland) to find out why some people can block infection by hepatitis C to improve treatment. Dr O'Farrelly studies women whose immune systems prevent the hepatitis C virus from establishing an infection. She recruited groups of women exposed to the hepatitis C virus (HCV) through a contaminated anti-D blood product, which attacks the liver. Unfortunately, many developed hepatitis C and some died from the disease. To do this, Prof Cliona O'Farrelly's team teamed up with Stemnovate to use white cells from the participant's blood samples and 'reprogram' them to grow as liver cells in the lab, avoiding this way invasive liver biopsies.
At Stemnovate, we have focused on creating liver in vitro and industrialising the process by creating a biobank of fully characterised IPSC lines and a reproducible liver differentiation method, ensuring biomarker profiling and functionality.
Furthermore, we are innovating new applications that have the potential to help new treatment development for liver cirrhosis and liver cancers.
Drugs or their intermediary metabolites can have a toxic effect and induce liver injury, which is the leading cause of acute liver failure and the major reason for drug withdrawal from the market. The search for models that could predict liver toxicity has been a challenge so far. Primary hepatocytes are considered the "gold standard" for drug metabolism and drug toxicity screenings, but their availability is dependent on human donors.
The use of iPSCs-derived hepatocytes in vitro for drug toxicity screenings offers a solution to this problem. Stemnovate iPSCs-derived hepatocytes have been used as a system to study the long-term toxicity of hepatotoxic compounds.
References
- Asrani SK, Devarbhavi H, Eaton J, Kamath PS. Burden of liver diseases in the world. J Hepatol. 2019 Jan;70(1):151-171. DOI: 10.1016/j.jhep.2018.09.014. Epub 2018 Sep 26. PMID: 30266282.
- Volker M. Lauschke (2021) Toxicogenomics of drug-induced liver injury – from mechanistic understanding to early prediction., Drug Metabolism Reviews, 53:2, 245-252, DOI: 10.1080/03602532.2021.1894571
- By defined factors, Takahashi K, Yamanaka S. Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures. Cell. 2006 Aug 25;126(4):663-76. DOI: 10.1016/j.cell.2006.07.024. Epub 2006 Aug 10. PMID: 16904174.
- Sinton, M. C., Meseguer-Ripolles, J., Lucendo-Villarin, B., Wernig-Zorc, S., Thomson, J. P., Carter, R. N., Lyall, M. J., Walker, P. D., Thakker, A., Meehan, R. R., Lavery, G. G., Morton, N. M., Ludwig, C., Tennant, D. A., Hay, D. C., & Drake, A. J. (2021). A human pluripotent stem cell model for the analysis of metabolic dysfunction in hepatic steatosis. iScience, 24(1), [101931]. https://doi.org/10.1016/j.isci.2020.101931