Enhanced ovarian FKBP51 expression is associated with ovarian aging: a molecular insight for age-related fertility in women.

Abstract

Objective: To study the relationship between FK506-binding protein 51 (FKBP51) and ovarian aging and/or diminished ovarian reserve (DOR) in human ovaries by comparing FKBP51 levels in granulosa cells (GCs) and cumulus cells (CCs), collected during controlled ovarian stimulation (COS) from women of advanced reproductive age and/or with a diagnosis of DOR with that of young women with normal ovarian reserve. To explore the association between increased FKBP51 expression and human ovarian aging further, expression of FKBP51 was compared in ovarian stroma of postmenopausal vs. premenopausal women. Lastly, this relation was further queried by comparing ovarian expression of several collagen genes as markers of ovarian fibrosis in 14-month-old wild-type (Fkbp5^+/+) and Fkbp5 knockout (Fkbp5^-/-) mice.

Design: Laboratory-based experimental study.

Subjects: Samples collected included follicular fluid, CCs, GCs, and serum from group 1: young women with normal ovarian reserve (<35 years; n = 12); group 2: DOR (antimüllerian hormone <1 ng/mL; n = 10); and group 3: women of advanced age with normal ovarian reserve (>37 years; n = 8). Ovarian stromal tissues obtained from surgical specimen of post-menopausal (50-65 years; n = 6) and pre-menopausal (18-30 years; n = 6). Ovarian tissues from 14-month-old Fkbp5^+/+and Fkbp5^-/- mice. All the experiments were performed at an academic-affiliated assisted reproductive technology unit/laboratory.

Exposure: Comparison of FKBP51 expression in GCs and CCs from women undergoing COS, ovarian stromal tissue from pre- and post-menopausal women, and ovarian tissue from aged Fkbp5^+/+and Fkbp5^-/- mice.

Main outcome measures: (1) Level of FKBP51 in human GCs and CCs, collected during COS by performing real-time quantitative polymerase chain reaction (qPCR). (2) Immunohistochemistry to detect FKBP51 levels and Picrosirius Red staining to detect collagen deposition in human ovarian stromal tissue. (3) Real-time qPCR to compare expression levels of several collagen genes in Fkbp5^+/+ and Fkbp5^-/- old mice ovaries. Serum and follicular fluid levels of transforming growth factor β1, and soluble endoglin measured by enzyme-linked immunosorbent assay.

Results: Immunohistochemistry revealed that FKBP51 histologic score levels in ovarian stromal tissue were significantly higher in postmenopausal vs. premenopausal women (mean ± SEM, 160.52 ± 17.75 vs. 120.67 ± 14.33; P=.002). Stronger Picrosirius Red staining, suggestive of fibrosis, was seen in ovarian stromal tissue of postmenopausal vs. premenopausal women (54.06 ± 6.94 vs. 37.50 ± 14.29; P=.02). Analysis of qPCR revealed that (1) Col1a1, Col1a2, Col3a1 levels were significantly lower in ovaries obtained from 14-month-old Fkbp5^-/- vs. Fkbp5^+/+ mice; (2) FKBP5 levels significantly increased in CCs of advanced age women vs. younger women (1.71 ± 0.22 vs. 1.11 ± 0.15; P=.03); and (3) FKBP5 levels were approximately threefold higher in GCs of women with DOR vs. age-matched control (3.22 ± 1.11 vs. 1.30 ± 0.54; P=.03).

Conclusion: This study for the first time demonstrates expression profile of FKBP51 in human ovary and its potential role in ovarian aging. Our results indicate that the up-regulation of FKBP51 is associated with ovarian aging. Moreover, in women undergoing in vitro fertilization treatment, enhanced FKBP51 expression is seen in those with DOR or women of advanced maternal reproductive age, who have poor prognosis. Therefore, drugs targeting inhibition of FKBP51 expression and/or activity may delay ovarian aging or treat premature ovarian aging.