Effect of chemerin on human granulosa cell function

Abstract

Chemerin is an adipokine that may be secreted by many other body tissues including the ovary besides adipose tissue. Some studies have revealed that chemerin may also exert its role in regulating the ovarian function. The higher levels of serum chemerin have been detected in patients with polycystic ovary syndrome (PCOS) than healthy women, hence suggesting a possible link between anovulation and obesity. It has been proved that chemerin and its receptor (CMKLR1) are highly expressed in the granulosa cells. Thus, it was hypothesized that chemerin may have potential inhibitory effect on granulosa cell function. At the preantral and antral stages of follicles, the granulosa cell is responsible for the secretion of anti-Müllerian hormone (AMH), an important hormone related to the regulation of follicular development. Meanwhile, the granulosa cells are also an important site where androgens are converted to estrogens with aromatase acting as the catalyzing enzyme. In this study, the human non-luteinized granulosa cell line (HGrC1) was selected as an in vitro model to study the effect of chemerin on these two aspects of human granulosa cell functions, namely the expression of AMH and AMH receptor (AMHRII), and the expression and activity of aromatase. Archived serum samples from 373 women were assayed for chemerin and AMH. There was no significant correlation between serum chemerin and AMH (p >0.05). HGrC1 cells were treated with recombinant human chemerin at 0, 10, 100, and 1000ng/ml. The expression of AMH and AMHRII were amplified and analyzed by real-time polymerase chain reaction (PCR). Our results demonstrated that chemerin had no effect on the expressions of AMH and AMHRII in HGrC1 cells. To explore the effect of chemerin on FSH-induced aromatase expression and activity, HGrC1 cells were treated with recombinant human chemerin (0, 10, 100, and 1000ng/ml) in the presence of androstenedione (10μM) and FSH (5IU/ml). The spent culture media were collected to measure the estradiol and testosterone concentration, and the total RNA of cells was isolated for analysis of aromatase gene expression. It showed that the expression of aromatase was significantly downregulated in the presence of chemerin in a dose-dependent manner (p <0.05). There was an apparent trend of lower estradiol production in the spent culture medium upon treatment with increasing doses of chemerin, although statistical significance was not reached (p >0.05). In conclusion, chemerin inhibits the FSH-induced aromatase expression but has no effect on the expression of AMH and AMHRII in human nonluteinized granulosa cells.