Refinement, reduction and replacement approaches to in vivo cardiovascular research.

In this review, the justification and benefits of refinement, reduction and replacement (3Rs) approaches to cardiovascular research are examined using the field of platelet biology and arterial thrombosis as an example. Arterial thrombosis is a platelet-driven condition and platelets are regulated by autologous signals, but also by external factors such as the vascular endothelium. In vitro assays using isolated platelets therefore poorly reflect in vivo platelet function and human disease. As a consequence, animal models, including mouse models, are frequently used. In particular, models of thromboembolic mortality have been successfully employed to determine the role of the vascular endothelium in regulating platelet function and thrombosis in vivo. Such models raise both scientific and ethical concerns and have recently been refined permitting the use of fewer mice at a lower severity level. These refinements have been scientifically beneficial in permitting analysis of the development and progression of thrombotic diseases and in improving our understanding of the role of the vascular endothelium in regulating platelet function and thrombosis. For many, the ultimate goal in 3Rs-driven science is replacement of animal models with non-animal alternatives; this is exemplified, in the platelet field, by the development of in vitro flow systems. The development of 3Rs approaches to cardiovascular research is shown to have led to improved scientific models. Further characterization and use of these models will likely contribute to increased understanding of thrombotic disease processes and facilitate drug development in the cardiovascular field.