Association between FOXP3+ regulatory T-cells and occurrence of peritoneal lesions in women with ovarian endometrioma and dermoid cysts.

RESEARCH QUESTION: Is there any relationship between numbers of FOXP3+ regulatory T-cells (Treg) and occurrence of peritoneal lesions in women with ovarian endometrioma and dermoid cysts?

DESIGN: Retrospective and prospective case-controlled cohort study. Peritoneal lesions were collected from 27 women with ovarian endometrioma and 25 women with dermoid cysts. Peritoneal fluid was collected from 36 women with ovarian endometrioma and 42 women with dermoid cysts. Tissue expression of Forkhead box P3 (FOXP3), one of the transcription factors of Treg cells, and transforming growth factor-beta (TGF-β) were examined by immunohistochemistry. Interleukin-6 (IL-6) and TGF-β levels in the peritoneal fluid were measured by enzyme-linked immunosorbent assay.

RESULTS: Ovarian endometrioma cases with coexisting peritoneal lesions were significantly more frequent than dermoid cyst cases with coexistent peritoneal lesions (269/350 [76.9%] versus 74/414 [17.9%]; P < 0.001). Numbers of FOXP3+ Treg cells were significantly higher in peritoneal lesions of women coexistent with ovarian endometrioma (F = 21.52, P < 0.001) and dermoid cysts (F = 22.01, P < 0.001) compared with women without peritoneal lesions. Higher FOXP3+ Treg cell numbers in pathological lesions corresponded with significantly higher TGF-β (P < 0.001) and lower IL-6 (P = 0.020) levels in peritoneal fluid of women with peritoneal lesions compared with women without lesions.

CONCLUSIONS: This study confirms current speculation that endometriosis is related to alteration in Treg cells, causing survival and implantation of ectopic endometrial lesions in women with endometrioma and dermoid cysts. The findings may clarify why only 10% of women in the general population develop endometriosis despite cyclic menstruation with retrograde flow occurring in >90% of women.