Animals in sarcopenia research

Muscle wastage and sarcopenia research generally uses mice and rats which have been immobilised or given nerve damage to recreate the symptoms of muscle wastage. These experiments are incredibly painful and stressful for the animals involved, and often go on for weeks or months at a time before the animal is eventually killed. It is estimated that around 5.4 million animals have been used in these types of experiments over the past 5 years, in academic settings alone. However, despite the staggering number of animals used in this area of research, there are still no effective treatments available for sarcopenia patients.

There are many reasons that animal experiments to study sarcopenia fail, including important differences in both the overall anatomy, and the muscle fibre structures, between humans and animals. Key differences in genetics, the immune system and the breakdown of drugs also mean that animal experiments don’t always translate into breakthroughs for patients.

The heartbreaking number of animals used with no real patient benefit highlights the desperate need for new, human-specific ways to research sarcopenia, moving away from animal experiments which are not gaining useful results. 

Lab-grown muscle

Some progress in this area has been made using tissue-engineered muscle made from human cells, but it is often difficult to get large enough numbers of cells to use in drug testing and medical research. Muscle tissue can be grown in the lab, but growth can be slow and difficult, meaning that researchers often default to animal experiments.

To help solve this problem, Dr Livia Rocha dos Santos at Nottingham Trent University is developing a new way to scale up the production of tissue-engineered muscle, using a technique that can make ten times more than current commercial production processes.

Dr Santos’ simple technology consists of a cell culture insert that human muscle cells are grown on, combined with an anchoring system. The insert helps the muscle cells to grow in an organised way and in the correct orientation, generating muscle tissue which can contract in the same way as it would in the body, making it an excellent alternative to animal models for use in many types of experiments. 

Replacing animal components

One of the key aims of Dr Santos’ project is to replace the use of animal-derived biomaterials such as foetal calf serum (FCS – a blood product which is a by-product of the meat trade), Matrigel, trypsin (a pig-derived enzyme used to detach cells from the flask they are growing in) and animal-derived cell-freezing medium, with animal-free alternatives. Replacing animal products will make the process completely human-specific, while increasing the reliability and clinical-relevance of the muscle tissue.

Impact and future goals

Dr Santos’ groundbreaking work will revolutionise the field of human tissue-engineering, while improving our understanding of muscle wasting diseases. The tissue engineered muscle can be used to test new drugs, while also creating opportunities for personalised medicine by using patient-derived cells to grow muscle tissue, allowing the effects of drugs to be studied in patients with specific conditions.

In 2023 in the UK alone, 7,906 experiments to study the musculoskeletal system were carried out using mice, with a further 7,197 experiments completed using fish, 448 using sheep, 101 using rats, 83 using cows and 16 using birds. Each of these experiments will have caused significant pain and suffering to the animals involved, but we still don’t fully understand the processes behind sarcopenia. If Dr Santos’ methods were to be widely taken up by researchers in this field, not only could the suffering of countless laboratory animals be prevented, but we would also move a step closer to new and effective treatments for patients.