The dysregulated IL-23/TH17 axis in endometriosis pathophysiology

Endometriosis is a chronic inflammatory disease where endometrial-like tissue grows ectopically, resulting in pelvic pain and infertility. Interleukin (IL)-23 is established as a key contributor in the development and differentiation of a subset of T cells known as T-helper 17 (TH17) cells, driving TH17 cells towards a pathogenic profile. In a variety of inflammatory and autoimmune disorders, such as psoriasis and rheumatoid arthritis, TH17 cells secrete proinflammatory cytokines including IL-17, contributing to the disease pathophysiology. Our studies and others have implicated IL-17 and TH17 cell dysregulation in endometriosis, which is associated with disease severity. Here we address whether IL-23 driven TH17 cells contribute to the cardinal features of lesion proliferation, vascularization, and inflammation in endometriosis using patient samples, representative cell lines, and our established mouse model of endometriosis. Our results indicate significantly dysregulated expression of key genes in the IL-23/TH17 axis in patient ectopic and eutopic endometrial samples and increased IL-23 protein in patient plasma compared to healthy controls. In-vitro studies using primary human TH cells determined that IL-23 cocktail treatment significantly increased the frequency of pathogenic TH17 cells. Similarly, treatment with recombinant human (rh)IL-23 on cell lines (12Z, EECC, HUVEC, and hESC) representative of the endometriotic lesion microenvironment led to a significant increase in cytokines and growth factors known to play a role in lesion establishment and maintenance. In a syngeneic mouse model of endometriosis, treatment with recombinant mouse (rm)IL-23 led to significant alterations in numbers of myeloid and T cell subsets in peritoneal fluid and significantly increased numbers of giant cells within the lesion. Endometriotic lesions from rmIL-23 mice did not reveal significant alterations in proliferation and vascularization, although trends of increased proliferation and vascularization were observed. Collectively, these findings provide insights into the impact of the IL-23/TH17 axis on local immune dysfunction and broadly on the pathophysiology of endometriosis.