One of the most, if not the most, contentious issues in science is the use of animals in research. Scientists experiment on animals for a host of different reasons, including basic research to explore how organisms function, investigating potential treatments for human disease, and safety and quality control testing of drugs, devices and other products. Its proponents point to the long list of medical advances made possible with the help of animal research. Opponents believe it is cruel and meaningless, as observations in animals often do not translate directly to humans.
In 1959, William Russell and Rex Burch proposed their “3Rs” guidelines for making the use of animals in scientific research more humane: restrict the use of animals; refine experiments to minimise distress; and replace tests with alternative techniques. Over the course of five decades their guidelines have become widely accepted worldwide, and while the reliability of published reports on the numbers used varies, they do at least provide a snapshot of historical trends. Around 29 million animals per year are currently used in experiments in the US and European Union countries. (Rats and mice make up around 80% of the total.) This is less than half the total in the mid-1970s – a significant drop, but one that has plateaued in the last decade.
“In the late 1980s, people thought animal research was singing its swan song,” says Larry Carbone, a senior veterinarian at the University of California in San Francisco. Fresh out of veterinary school in 1987, Carbone landed a job as an animal vet at Cornell University, in New York State. At that time the numbers of animals being used in experiments and testing was on the decline: the campus was building a new multi-storey biotechnology facility, with just three rooms containing animal breeding and living facilities.
But then came the development of tools that could selectively modify individual genes in mice. This proved to be such a powerful and popular technique that the decreasing trend in animal use ground to a halt.
Now, a raft of novel experimental techniques may help to push numbers down again. Improvements in imaging methods that offer a peek inside the bodies of animals allow scientists to get more and better data from each experiment than before. For example, researchers previously had to cull multiple mice at different stages of tumour development, but now they can non-invasively watch the disease unfold in a single living animal using a fluorescent dye. Similarly, as brain-imaging techniques become more advanced, some questions that are now addressed with experiments in monkeys might be better answered by peering into the human brain. “My prediction is that human volunteers will be able to replace monkeys more and more in the next 10-20 years,” says Carbone.
Meanwhile in vitro advances are also pointing towards reliable alternative methods. One such advance is the ability to re-program human skin cells into a primordial, stem cell-like state. These “induced pluripotent cells” could be converted into any specialised cell in the body, like liver or kidney cells, and these could be generated from people with a particular illness, giving researchers a potent and patient-specific model of that disease in a dish. Lab-on-a-chip technologies – and perhaps one day, lab-grown organs – could also provide increasingly sophisticated ways to identify disease mechanisms or test prospective medicines.
Trends also show that some sectors are doing more than others to reduce animal use. Some believe technological advances will one day make animal studies unnecessary, while others argue that “non-living” models will never be capable of reliably replicating all of the uses of laboratory mice and other creatures.