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Ovarian circadian oscillators have been implicated in the reproductive processes of mammals. However, there are few reports regarding the detection of ovarian clock-controlled genes (CCGs). The present study was designed to unravel the mechanisms through which CCG ovarian circadian oscillators regulate fertility, primarily using quantitative RT-PCR and RNA interference against Bmal1 in rat granulosa cells. Mature granulosa cells were prepared from mouse Per2-destabilized luciferase (dLuc) reporter gene transgenic rats. A real-time monitoring system of Per2 promoter activity was employed to detect Per2-dLuc oscillations. The cells exposed to luteinizing hormone (LH) displayed clear Per2-dLuc oscillations and a rhythmic expression of clock genes (Bmal1, Per1, Per2, Rev-erbα, and Dbp). Meanwhile, the examined ovarian genes (Star, Cyp19a1, Cyp11a1, Ptgs2, Lhcgr, and p53) showed rhythmic transcript profiles except for Hsd3b2, indicating that these rhythmic expression genes may be CCGs. Notably, Bmal1 small interfering (si)RNA treatment significantly decreased both the amplitude of Per2-dLuc oscillations and Bmal1 mRNA levels compared with nonsilencing RNA treatment in luteinizing granulosa cells. Depletion of Bmal1 by siRNA decreased the transcript levels of clock genes (Per1, Per2, Rev-erbα, and Dbp) and examined ovarian genes (Star, Cyp19a1, Cyp11a1, Ptgs2, Hsd3b2, and Lhcgr). Accordingly, knockdown of Bmal1 also inhibited the synthesis of progesterone and prostaglandin E2, which are associated with crucial reproductive processes. Collectively, these data suggest that ovarian circadian oscillators regulate the synthesis of steroid hormones and prostaglandins through ovarian-specific CCGs in response to LH stimuli. The present study provides new insights into the physiologic significance of Bmal1 related to fertility in ovarian circadian oscillators.

The circadian oscillator is generated within the suprachiasmatic nuclei and synchronizes circadian clocks in numerous peripheral tissues. The molecular basis is composed of a number of genes and proteins that form transcriptional and translational feedback loops. Such molecular oscillators are also operative in peripheral tissues, including in the uterus. Although ovarian steroids regulate the function of uterine endometrial stromal cells, the modulation of ovarian steroids on the circadian rhythms remains unknown. Here we investigate the possibility that estradiol (E2) and progesterone (P4) modulate the circadian oscillator of the stromal cells. The study using transgenic rats constructed with Period 2 (Per2) promoter-destabilized luciferase (Per2-dLuc) gene, with the real-time monitoring system of Per2-dLuc oscillation. The stromal cells displayed constant Per2-dLuc oscillation after treatment with dexamethasone, suggesting that the circadian oscillator is operative. However, the circadian oscillator was disrupted by in vivo administration of human chorionic gonadotropin (hCG) following equine chorionic gonadotropin (eCG), although it was altered into a rhythmic pattern 4 days later following hCG. Chronic treatment with P4 induced constant Per2-dLuc oscillation in the stromal cells from eCG-treated immature and pregnant rats, whereas E2 did not promote such a rhythmic Per2-dLuc oscillation. Collectively, P4 synchronizes the circadian oscillator of the uterus endometrial stromal cells through transcriptional and translational feedback loops of the clockwork system.

It has been established that estrogen can alter circadian rhythms in behavior and endocrine physiology in rodents. The uterus is a reproductive organ that is critically dependent on regulation by ovarian steroids. Here, we examined the expression of Per1 in different compartments of the uterus, and explored whether the ovarian steroids could regulate Per1 expression employing ovariectomized rat uterus. RT-PCR analysis showed that Per1 was cyclically expressed in the uterus. As revealed by in situ hybridization, the staining intensity of Per1 mRNA was stronger at ZT 8 than at ZT 0 in the uterine luminal epithelium (LE), stroma (S), and myometrium (M) compartments, but was not changed in the glandular epithelium (GE). Both in situ hybridization and immunofluorescence analyses revealed that estradiol (E(2)) administration induced high expression of Per1 in the LE, GE, and M, and less expression in the S compartment. Progesterone (P(4)) treatment resulted in an obvious enhancement of Per1 expression in the LE, GE, and S, but unchanged in the M compartment. Furthermore, the E(2)- and P(4)-activated Per1 expression was significantly repressed by their respective antagonists, ICI182 780 and RU486. These findings were further supported by RT-PCR analysis of Per1 expression in cultured uterine stromal cells. Collectively, the present data indicate that E(2) and P(4) might be involved in modification of circadian rhythm via direct regulation of the expression of clock genes.

A primary role of plasma membrane P-glycoprotein (P-gp), encoded by multidrug resistance type I (MDR1), is to protect against naturally occurring xenotoxics. Progesterone (P(4)) profoundly influences MDR1 expression in granulosa cells and luteal cells. Here, P(4) regulation of MDR1 expression was investigated in porcine granulosa cells using the P(4)-mediated promoter activity assay and a P4 receptor (PR) antagonist (RU-486). The promoter activity was measured chronologically for 48 h in cells transfected with the PR response element-containing pGL3. LH could stimulate the promoter activity through endogenous P4, with a maximum activity at 5 h. MDR1 mRNA level was highly maintained at 24-36 h. Conversely, exogenous P4 prolonged the promoter activity to further 10 h, and the high level of MDR1 mRNA was maintained even at 48 h. RU-486 completely inhibited the promoter activity, but the level of MDR1 mRNA rapidly increased in the presence of RU-486. The granulosa cells may become susceptible to RU-486 as a xenotoxic to rapidly express MDR1 for protection against it. These results indicate that MDR1 is expressed in porcine granulosa cells through P4-dependent and -independent regulations.

P-glycoprotein (P-gp) coded with the multidrug resistance type I (MDR1) is expressed in various normal tissues including ovaries and may function as detoxification and steroid transport. The present study was performed to analyze the expression and function of MDR1 in granulosa cells stimulated with FSH, LH, estradiol-17beta (E) and progesterone (P). The granulosa cells isolated from porcine ovarian follicles were cultured for 24h in a serum-supplemented medium, and then cultured for 48h with the hormones in a serum-free culture medium. MDR1 was highly expressed in large follicles and induced in cultured granulosa cells stimulated with LH as revealed by RT-PCR. Highly expressed MDR1 resulted in the increased P-gp activity. However, FSH had no effect. P significantly increased the MDR1 expression and P-gp activity in the cells stimulated with LH, whereas E had no stimulatory effect. Aminoglutethimide suppressed the MDR1 expression and P-gp activity, but which were completely restored by P. These results indicate that P participates in MDR1 expression and P-gp function of granulosa cells.

The induction of the decidualization of endometrial stromal cells is possible in an in vitro cell culture system. However, thus far, methods differ according to species or cell type, and a more stable or universal system has not yet been developed. The purpose of the present study has been to establish an in vitro decidualization system in primary cultured rat endometrial stromal cells (RES). The RES were treated with medroxyprogesterone acetate and dibutyryl-cyclic adenosine monophosphate (MPA treatment), estradiol and progesterone, or arachidonic acid. After 24 h of treatment, cells responded to all of the stimulations by expressing desmin mRNA. However, decidual/trophoblast prolactin-related protein (dPRP) mRNA was only expressed in the MPA-treated cells. Desmin and dPRP mRNA were not expressed after MPA treatment of the RES derived from immature rat uteri. However, mRNA from both desmin and dPRP were expressed in RES derived from gonadotrophin-injected immature rats. The expression of matrix metalloproteinase-2 (MMP-2) and MMP-9 mRNA did not change after the decidual treatment of RES examined by real-time polymerase chain reaction. However, the results of gelatin zymography showed that the active forms of MMP-2 and MMP-9 significantly increased after in vitro decidualization ( P < 0.05). We conclude that MPA treatment is the most effective method for stimulating decidualization in RES. Use of this system has revealed that sexual maturation and gonadotrophins are important for RES with regard to decidualization. Furthermore, the activity of MMP-2 and MMP-9 might increase during decidualization without a corresponding increase of the expression of these genes. [ABSTRACT FROM AUTHOR]