Model Livers to Replace Lab Rats

German researchers have developed an external model of the liver, which could provide a safer alternative to animal experiments

If you have fever, headaches or a cold, it’s only a short way to the nearest chemist. The drugs, on the other hand, can take up to eight to ten years to develop.

Animal testing has been an essential step in testing drugs, but it continues to raise ethical issues. Furhermore,
humans and animals have different metabolisms, and around 30 per cent of side effects come to light in trials following animal experiments.

Researchers at the the Fraunhofer Institute have developed a model of the liver, which is viable outside the body and is suitable for testing drugs.

“Our artificial organ systems offer an alternative to animal experiments,” said Heike Mertsching, Professor at the Interfacial Engineering and Biotechnology Institute at Fraunhofer.

The test system, which Professor Mertsching has developed jointly with Dr Johanna Schanz, should in future give pharmaceutical companies more security and shorten the path to developing and releasing new drugs.

“Our liver model is a functioning system of blood vessels,” said Dr. Schanz. “We don’t build artificial blood vessels, but use existing ones – from a piece of pig’s intestine.”

All of the pig cells are removed, but the blood vessels are preserved. Human cells are then seeded onto this structure – hepatocytes, which are responsible for breaking down drugs, and endothelial cells, which act as a barrier between blood and tissue cells.

In order to simulate circulation, the researchers put the model into a computer-controlled bioreactor with a flexible tube pump. This enables the nutrient solution to be fed in and carried away in the same way as in veins and arteries in humans.

“The cells were active for up to three weeks,” said Dr. Schanz. “This time was sufficient to analyse and evaluate the functions. A longer period of activity is possible, however.”

The researchers established that the cells work in a similar way to those in the body. They detoxify, break down drugs and build up proteins. These are important pre-conditions for drug tests or transplants, as the effect of a substance can change when transformed or broken down. Many drugs are only metabolised into their therapeutic active form in the liver, while others can develop poisonous substances.

At the moment, the test system is being examined. The researchers say it could provide an alternative to animal testing within two years.

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