Reducing and replacing mouse use to model the human platelet response in vivo

Huge numbers of mice are used in the UK to research cardiovascular diseases such as pulmonary embolism. Pulmonary embolism occurs when blood clots form in the legs of bed-ridden patients or occasionally following a long flight in economy class. Until recently research into the causes of pulmonary embolism was carried out in mice by inducing massive pulmonary embolism in conscious animals to induce death or paralysis. An earlier NC3Rs grant allowed us to refine this method so that neither death nor paralysis was induced and the procedure was conducted entirely under general anaesthesia. Our method does, however, require the death of large numbers of mice since we must collect cells from their blood and monitor these cells in additional mice. We want to show now that we can reduce animal use by using cells from human blood rather than animal tissues and infuse the human cells into mice. We shall conduct experiments to demonstrate that blood clots form in our human-mouse model in a way that represents human disease. We shall also demonstrate that the effects of drugs such as aspirin can be evaluated in the mouse by giving the drug to human volunteers rather than by repeatedly and forcibly introducing it to the stomachs of mice. As well as reducing animal use this research will allow us to work with patient samples in an entirely new way which may contribute to cardiovascular research generally. Since a number of research groups have incorporated our methods into their research plans the reduction in mouse use achieved in our own laboratory will be amplified several fold.

Until recently, assessing platelet thromboembolism in mice involved the injection of thrombogenic substances into conscious animals to induce death or paralysis. This procedure inflicted considerable pain and suffering and was scientifically limited since it only modelled one extreme end-point of a disease with a broad spectrum. An NC3Rs project grant awarded in 2006 allowed us to refine this methodology so that we recorded non-lethal responses in anaesthetised mice by monitoring radiolabelled platelets in real-time. As well as refining a procedure from a severe to unclassified level, we were able to reduce mouse use by recording multiple responses within an individual animal. Our refined model involves the death of large numbers of donor mice that are bled for platelets which are radiolabelled and subsequently reinfused into recipient animals. We will now show that human donors can be used instead of mice to reduce mouse use by 50% and reduce the numbers of mice subjected to drug administration procedures. To achieve this we shall infuse radiolabelled human platelets into mice to create a humanised-mouse model. We intend to fully characterise the humanised-mouse as a model of thrombosis by extending our preliminary data and conducting experiments confirming normal physiological platelet responsiveness in our model together with supporting histological analysis. Additionally, we shall demonstrate that in vivo pharmacological experiments with agents such as aspirin can be conducted by giving aspirin to human volunteers rather than gavaging donor mice. In addition to the 3Rs benefits, the development of humanised-mouse models has scientific advantages in enabling us to investigate human rather than animal cells in a controlled, potentially genetically modified, in vivo environment. We intend publishing our work in a high quality peer reviewed journal and participating in stakeholder, scientific and public dissemination events. The 3Rs impact of our work will occur not only within our own group but with groups already collaborating with us who apply our refined methodologies to their own research.