Context: FSH receptor (FSHR), besides being expressed in gonads, is also expressed in some extragonadal tissues at low levels.
Objective: We examined the functional expression of FSHR in different types of endometriotic lesions.
Design: Extensive studies were carried out to detect functional FSHR expression and FSH-stimulated estrogen production in ovarian endometriomas and recto-vaginal endometriotic nodules (RVEN). Normal endometrium, ovary, and myometrium tissues from nonpregnant cycling women served as controls.
Settings: This laboratory-based study was carried out on tissue specimens from patients with endometriosis and healthy donors.
Results: Endometriotic lesions and normal secretory-phase endometrium showed FSHR expression at both mRNA and protein level. RVEN and ovarian endometrioma demonstrated up-regulated CYP19A1, dependent on the activation of CYP19A1 proximal promoter II. Estrogen receptor-β (ESR2) expression was significantly increased in RVEN vs normal endometrium. Recombinant human FSH stimulation of RVEN explants significantly increased estradiol production and CYP19A1 and ESR2 expression. FSHR was up-regulated in recombinant human FSH-stimulated endometrial and decidualized stromal cells with increased CYP19A1 expression.
Conclusions: We described a novel functional FSHR expression, where FSH-stimulated CYP19A1 expression and estrogen production in RVEN are demonstrated. This locally FSH-induced estrogen production may contribute to the pathology, development, progression, and severity of RVEN.