Pre-clinical models of endometriosis: a focus on chronic pain

Endometriosis is a multifaceted chronic disease with a complex and variable display of clinical symptoms. Chronic pelvic pain (CPP) affects most women with endometriosis, leaving patients frequently suffering from widespread pain, often associated with painful comorbidities. Despite this significant disease burden, limited progress has been made in elucidating the mechanisms contributing to endometriosis-associated CPP development. Accordingly, therapies that adequately target and treat the debilitating pain remain lacking. Small animal models of endometriosis show considerable promise as pre-clinical tools to investigate the mechanisms of CPP; however, the majority of these studies focus on the pathogenesis and development of endometriosis, which leaves the mechanisms underlying CPP elusive. When established behavioural techniques are incorporated into these pre-clinical animal models of endometriosis, it is apparent that they recapitulate key pain attributes that are observed clinically in women with endometriosis. However, studies often employ only one or two behavioural techniques focused on an individual symptom, rather than utilising multiple techniques to uncover the mechanisms underlying diverse and comorbid pain. As many women with endometriosis suffer from widespread pain that frequently affecting multiple organs, a paradigm shift aimed at encompassing a multifaceted approach is essential for the future study of endometriosis-associated pain.