Thymic stromal lymphopoietin contributes to endometriotic lesion proliferation and disease-associated inflammation.

Endometriosis is a chronic disorder in which endometrial-like tissue presents outside the uterus. Patients with endometriosis have been shown to exhibit aberrant immune responses within the lesion microenvironment and in circulation which contribute to the development of endometriosis. Thymic stromal lymphopoietin (TSLP) is an alarmin involved in cell proliferation and the induction of T helper 2 (Th2) inflammation in various diseases, such as asthma, atopic dermatitis, and pancreatic and breast cancer. Recent studies have detected TSLP within endometriotic lesions and shown that its concentrations are elevated in the peritoneal fluid of patients compared with control subjects. However, its role in disease pathophysiology remains unclear. Here, we compared TSLP messenger RNA and protein expression between patient eutopic endometrium, endometriotic lesions, and control endometrial samples. We also assessed its effect on the proliferation and apoptosis of human endometriosis-representative cell lines, as well as on lesion development and inflammation in a mouse model of the disease. We demonstrated that TSLP expression was elevated in the stroma of patient endometriotic lesions compared with control endometrial samples. In cell lines, TSLP treatment reduced the apoptosis of endometrial stromal cells and promoted the proliferation of THP-1 cells. In mice induced with endometriosis, TSLP treatment induced a Th2 immune response within the lesion microenvironment, and led to TSLP receptor modulation in macrophages, dendritic cells, and CD4+ T cells. Furthermore, treatment increased murine endometriotic lesion proliferation. Overall, these results suggest that TSLP modulates the endometriotic lesion microenvironment and promotes a Th2 immune response that could support lesion development.