By Clair Brooks, PhD student at the FRAME Alternatives Laboratory.
Before a drug can be used in humans, it undergoes rigorous scientific testing to ensure its safety. As the liver has a key role in the removal of drugs and toxic substances from the body, it is very susceptible to drug accumulation and associated liver damage. For this reason, the liver is one of the main organs pharmaceutical companies look at when deciding whether a drug is safe or not. Despite this extensive testing, liver toxicity remains one of the main reasons that drugs are recalled from the market (1).
Questioning the accuracy of animal models
The current gold-standard toxicity tests are animal-based, but the number of drugs being recalled has raised questions over how accurately rodent models can predict adverse effects in humans. In addition to doubts over their safety, animal-based toxicology tests are time consuming, costly and have associated animal welfare issues. Together with an ever-increasing number of new drugs being developed, these issues highlight a growing need for alternative toxicity tests.
Animal free testing
Current animal free tests include growing liver cells in artificial settings, but these often fall short due to the difficulties of growing liver cells in an environment that accurately mimics that of the human body, and existing systems fail to replicate the complex structure and size of the liver.
For this reason, the FRAME Alternatives Laboratory is developing a cell-based liver toxicology model that will allow liver cells to be grown in an environment that is complex and physiologically relevant. To mimic the complex structure of the liver, FRAME aims to utilise the technology of 3D-printing. This method uses a computer to control the addition of material building blocks to form a three-dimensional object.
The challenge is to find a material that can be used for 3D printing, but also allows the growth of liver cells. The FRAME team believes this can be achieved using modified alginate – a naturally occurring substance often extracted from brown seaweed. It is already used in a variety of medical applications as it can be easily modified by adding things such as calcium, resulting in the formation of a hydrogel that is both low-cost and biocompatible.
The FRAME Alternatives Laboratory has further modified alginate hydrogels and has already proven that these can support the growth of a cancerous liver cell-line. With further adaptations, the plan is to provide a printable material that allows the culture of primary hepatocytes, liver cells that have been obtained from human donors.
This is not an easy task as there are an endless number of ways to modify alginate hydrogels, and each one needs to be made and then extensively assessed for its effect on liver cells. This is a lengthy process and would significantly slow down the development of this model.
PhD student Elisa Tarsitano is currently optimising the process of a pin printing microarray, which will allow up to 2,862 modified alginates to be screened in one experiment. The most promising alginates can then be analysed and modified further if needed, before being taken forward for 3D-printing.
Once finished, this model has the potential to be used for high-throughput screening, in which large numbers of drugs can be screened quickly and cheaply, so that only the most successful are taken forward into animal models. As the technology develops and its accuracy in predicting toxicity in humans is proven, FRAME hopes that it can completely replace the use of animals in hepatotoxicity testing.
(1) Friedman, Scott E.; Grendell, James H.; McQuaid, Kenneth R. (2003). Current diagnosis & treatment in gastroenterology. New York: Lang Medical Books/McGraw-Hill. pp. 664–679.