Mention animal testing, and it's likely you'll be met with a barrage of very strong opinions on either side, from those who insist the practice is cruel, to scientists who say it is necessary to create invaluable medical treatments.
But while the debate rages about whether or not it is ethical to test on animals, one charity has been doing something very different, and taking animals out of the picture altogether. In fact, in some cases, they've actually replaced animals with humans.
Founded in 1970, the Dr Hadwen Trust (DHT) has awarded millions of pounds to more than 180 projects that use non-animal models in scientific procedures.
"With a lot of the research projects that we fund the academics themselves are telling us that the data coming out of the animal studies has got some very questionable benefits, if any, to the human condition.
"So what we are trying to do is address that by implementing human-focused research approaches," said Dr Brett Cochrane, group head of science at the DHT.
His comments come as the RSPCA calls for more to be done to reduce the use and suffering of laboratory animals.
World Day for Animals in Laboratories, which is marked every year on April 24, commemorates the millions of animals used in medical procedures.
Nearly 4 million animals were used in completed scientific experiments in the UK in 2014, according to the latest Home Office statistics.
The RSPCA reports that 11.5 million animals are being used in the European Union and more than 100 million worldwide.
The 3Rs, replacement, reduction and refinement, help to regulate the use of animals in scientific procedures. The DHT's primary focus is that of 'replacement'.
From leukaemic stem cell research to 3D models of the human blood-brain barrier, the research projects it funds differ hugely. And the scope for non-animal models is increasing.
The DHT describes itself as a "compassionate organisation that is very solution focused to address the animal problem".
The organisation not only looks to replace the number of animals used in experiments but also focuses on improving human health and human safety of drugs, Dr Cochrane said.
Change is possible and that is what we are trying to endorse.
He added: "I am not saying that there have never been any scientific breakthroughs with animals at the heart of the research process.
"But too many animals have been used over the decades for that and what I am saying is that I would like to see far more work being done in that replacement stage to put humans at the heart of the research process.
"There are so many issues around this, around trying to change the culture and process of this, but it is possible."
He added: "Change is possible and that is what we are trying to endorse. We are very pro-research, we are very pro-human health, let’s put the human at the heart of everything we do."
In the past five years, the DHT has invested about £3.2 million in research projects.
Five grants from the DHT's current portfolio:
According to figures from the Home Office and Cancer Research UK, approximately 23,000 mice are used per year to investigate leukaemia. This three-year project, led by Dr Helen Wheadon at the University of Glasgow, aims to develop a stem cell model that has been derived from patient cells and can be used in pre-clinical testing. Dr Wheadon told the Huffington Post UK that, by taking patient samples and re-programming them, a "good humanised model for looking at leukaemia" could be developed.
Type 2 Diabetes
In the UK, 3.3 million people have been diagnosed with diabetes and there is no cure. The aim of Professor Lorna Harries's team at the University of Exeter Medical School is to better understand the mechanisms that cause some pancreatic cells to lose their ability to produce insulin in those suffering from diabetes. Currently an estimated 100,000 animals are used annually worldwide to explore this, with cell lines from rats or mice most commonly used. Professor Harries told the Huffington Post UK that her group is using laboratory-grown human cells. She said: "There are some really good reasons why we shouldn't be using animal models in this and why we should be using people because the human body is very different from animals."
Professor John Graeme Houston's team at the University of Dundee use human bodies donated to medical science, which have been preserved using an alternative embalming process. Their project focuses on the development, testing and training of cardiovascular device implantation to treat arteries and veins. Professor Houston told the Huffington Post UK: "Previously many studies across the world have used animals for this. These tend to be large animals - dogs and pigs - and this is not great. The animals are not the same as us anatomically, they don't have the same diseases." The method being developed by Professor Houston's team is going "very well", he said, and has been used in junior doctor training.
A highly sophisticated 3D "all-human" in vitro (test tube) model of the human blood-brain barrier has been developed by Professor Geoffrey Pilkington's team at Portsmouth University. The aim is to study brain tumour invasion and brain metastasis. The team's work will further the case for increased pre-clinical testing in vitro, therefore removing the need for animal testing prior to clinical trials. The research may be extended to better-understand a wide range of other neurological diseases and disorders.
Genetically-altered mice are often used in current research models by being implanted with pieces of human tumour. There is a concern that data collected via mice models do not translate to the human disease. Professor Oliver Hanemann's team at Plymouth University use a unique model of human cell culture derived from patients at surgery. The team has successfully translated their research into early clinical trials and their results have led to the identification and testing of new targeted therapies.
The RSPCA is calling for more to be done to reduce the use and suffering of laboratory animals.
The animal protection group said that more than 100 million animals are used around the world every years in research and testing.
The RSPCA is calling on the scientific community to take five essential actions:
Greater efforts to replace or avoid animal experiments, including use of humane alternatives.
More critical scrutiny of the value of animal ‘models’ and tests
Stop poorly designed animal experiments from being carried out and published
Laboratories should prove animals they are caring for animals beyond the minimum standards required by law
Far greater honesty about the harms experienced by animals used in research, and the limitations of animal experiments, instead of simply highlighting the benefits.
Dr Penny Hawkins, head of the RSPCA’s research animals team, said: "The days when the scientific community could get away with paying lip service to concerns about animal use are over.
"Many scientists, animal technologists and vets are stepping up and working together to address serious ongoing problems with animal research, but this varies greatly and it is time for everyone to commit to reducing animal use and suffering.”
Dr Hawkins stressed the new biotechnologies that are available, such as 3D printing techniques to create artificial bones and blood vessels.
She said the RSPCA would like to see much greater progress with technologies such as ‘organ-on-a-chip’, which can use biotechnology to replace animal experiments, adding "this has to be the goal for the 21st century".
While the DHT advocates improved animal welfare and a reduction in those species used for laboratory research, the medical charity's fundamental goal is to replace animal-based approaches in experiments.
One of the challenges that the DHT face is a lack of awareness about vivisection, as well as the replacements that are being developed.
Dr Cochrane said: "I would like to see much more of a focus on non-animal based approaches
"Even if it’s not for the animal’s perspective, we are trying to find better treatments and drugs for human diseases so let’s invest in human understanding of those research processes."