Animal Models of Psoriatic Arthritis: Scientific Value, Ethical Challenges and Principles of Care in Research of Painful Conditions

Psoriatic arthritis is a chronic inflammatory musculoskeletal condition that affects a notable fraction of patients with psoriasis. It is usually preceded by the typical psoriatic skin lesions and is characterized by joint pain, stiffness and swelling, as well as a variety of other musculoskeletal and extra-articular features. It significantly affects quality of life, with patients reporting pain, fatigue, stiffness and impaired sleep, which lead to limitations in daily activities and a decline in emotional health. Despite the increasing therapeutic options, the pathophysiology of this condition remains only partly understood and animal models have often been used to study the different immunological and genetic factors. This thesis will review the different models that phenotypically mirror aspects of psoriatic arthritis, with a focus on welfare. The predominant species used is the mouse, given the very extensive research for understanding their immune system and genome, as well as the practicality and cost of laboratory mice husbandry. Most mouse models of psoriatic arthritis have been created through genetic engineering or injecting inflammatory cytokine-encoding DNA. The thesis will also place emphasis on the care principles and welfare considerations for the specific models throughout their lifespan. It will propose a scale built on previously established assessment frameworks, providing specific parameters to monitor for the assessment of pain levels and suffering in psoriatic arthritis studies. Finally, the thesis will discuss the scientific justification and guidelines, as well as the current EU and Italian laws regarding studying painful conditions on live animal models.