Laboratory animal science is an evidence based scientific discipline and an important element in the responsible use of animals in biomedical research. A major focus is implementation of the 3Rs’ principles,
replacement, reduction, and refinement, which are a pre-requisite of ethically acceptable research using animal models. At the level of the preclinical study, the quality of research results is influenced by the
frequency and severity of interventions inflicted on the model animal and the number of refinements implemented to counteract the harms stemming from them. Implementation of refinements at the level of the in vivo preclinical study should be clearly documented at all stages, the planning, conducting and the reporting stages, to help achieve more rigorous, transparent and translatable animal-based research. Failure
to implement the 3Rs and to document their use at all stages of preclinical in vivo research increases the risks of bias and impairs translatability of preclinical research. Some biases, like selection bias and detection bias, may be prevented through simple study design features like randomisation and blinded assessment. The goal of this PhD study was to elucidate to which extent the refinements implemented influenced a rat model of RA, to provide more methodological detail of the rodent adjuvant-induced arthritis (AIA) model and to suggest best practices, higher validity protocols aiming to improve predictability of the AIA model. Refinement principles require application of pharmacologic refinements (analgesia and anaesthesia) as well as non-pharmacologic refinements into research protocols involving animals aiming to protect the welfare of research animals and consequently, the quality of animal-based research.In our investigations (Studies 1, 2 and 3) we applied and explored the effects of a number of pharmacologic
refinements more in line with the medical treatments of humans suffering from arthritis (e.g. treatments with indomethacin, fluoxetine and buprenorphine) and non-pharmacologic refinements (e.g. varied cage
density and environmental enrichment (EE) appropriate for the modelled disease, blinding of subjective outcome assessments) aiming to assess how their application affected key translational parameters and the robustness of the rat AIA model.

Study 1 demonstrated robustness of the model as we did not find evidence that alterations in the housing conditions of the rats (cage density and EE) influenced our results, the variability of these or the inflammation parameters monitored. The second study did not provide evidence supporting analgesic effects of the antidepressant fluoxetine nor its impacts on disease progression and severity. In Study 3, combined indomethacin and buprenorphine therapy did not significantly impact the validity of the AIA model. Comparing visual and histopathology blinded, and informed assessments confirmed best in vivo preclinical practice recommendations advocating blinding as a mandatory practice in conduct of preclinical in vivo efficacy studies. Furthermore, conduct of rat AIA protocols in Croatia and Israel confirmed the AIA model was reasonably robust, which is positive given that it remains a widely used model. To conclude, this PhD project undertook 3 comprehensive comparative studies based on the rat AIA model, providing empirical evidence on the causal relationships between specific aspects of study design and use of refinements, and the outcome are protocols that are methodologically more detailed and better validated, supporting clinical development and translatability.