Refine, reduce, replace: Imaging of fibrosis and arthritis in animal models.

Non-invasive imaging has great potential to contribute to the 'Three R's' principles for more ethical use of experimental animals. It enables repetitive monitoring of disease progression and measurement of quantitative biomarkers that report on disease progression and therapy efficacy in the same animal, thereby reducing manifold the number of animals needed for in vivo studies whilst advancing our knowledge into the pathophysiology of these diseases. This article reviews applications of non-invasive imaging in the field of fibrosis and arthritis research. It provides evidence for the viability of this approach not only for ethical reasons (reducing numbers and suffering in research animals, according to the 3R principles) but also for accelerating experimental output and making it more translational. The emphasis is on promising developments which will help improving throughput by reducing experiment length and size as well as human resources for data analysis, therefore encouraging a wider spreading of novel imaging technologies.