Mediation of gonadotrophin-stimulated growth and differentiation of human granulosa cells by adenosine-3',5'-monophosphate: one molecule, two messages

Prolactin receptor regulates the seasonal reproduction of striped hamsters

In this study, differential mRNA expression patterns of prolactin receptor (PRLR) in the hypothalamus and gonads, and the correlation with follicle stimulating hormone (FSH) and luteinizing hormone (LH) in striped hamster serum from spring, summer, autumn and winter were analyzed. Mature female and male striped hamsters in oestrus were used. Expression levels of PRLR in the hypothalamus, ovaries and testis from the summer and winter individuals were significantly higher compared with levels from the spring and autumn, whereas FSH and LH serum concentrations from summer and winter individuals were significantly lower compared with that from the spring and autumn. PRLR expression levels in hypothalamus, ovaries and testis were negatively correlated with FSH and LH serum concentrations, illustrating that PRLR might negatively regulate seasonal reproductive activity. PRLR expression levels in ovaries and testes were significantly higher compared with levels in the hypothalamus, suggesting that the regulative effects of PRLR in gonads might be significantly higher compared with that in the hypothalamus. Furthermore, PRLR expression levels from the spring, summer, autumn and winter seasons in the hypothalamus and gonads were significantly higher in females compared with levels in males, indicating that the regulative effect of PRLR might be sex dependent. Taken together, this study helps to understand in depth the seasonal regulative reproduction mechanism of striped hamsters to reasonably control population abundance.

Virus analog decreases estradiol secretion in FSH-treated human ovarian granulosa cells

The aim of this study was to evaluate the effect of virus infection on estradiol (E₂) production in human ovarian granulosa cells. Polyriboinosinic polyribocytidylic acid [Poly (I: C)], a synthetic analog of viral double stranded RNA that can be recognized by Toll like receptor 3 (TLR3), was used to imitate virus infection. Granulosa cells (GCs) obtained from patients undergoing in vitro fertilization and embryo transfer (IVF-ET) were cultured in vitro and treated with Poly (I: C), FSH, or both. Concentration of E₂ was assayed by electrochemiluminescence. The mRNA and protein expression of TLR3 and aromatase were determined by real-time quantitative PCR (qPCR) and Western blot, respectively. The results showed that expression of TLR3 mRNA was significantly increased after Poly (I: C) stimulation. Poly (I: C) decreased E₂ synthesis in FSH-treated GCs. Poly (I: C) inhibited the expression of aromatase in FSH-treated GCs. This study demonstrated that Poly (I: C) inhibits the synthesis of estradiol by granulosa cells under the stimulation of FSH, which might contribute to disturbance of follicular development and ovulation.

Pharmacogenetics of FSH Action in the Female

The purpose of a pharmacogenomic approach is to tailor treatment on the basis of an individual human genotype. This strategy is becoming increasingly common in medicine, and important results have been obtained in oncologic and antimicrobial therapies. The rapid technological developments and availability of innovative methodologies have revealed the existence of numerous genotypes that can influence the action of medications and give rise to the idea that a true "individualized" approach could become in the future a reality in clinical practice. Moreover, compared to the past, genotype analyses are now more easily available at accessible cost. Concerning human reproduction, there is ample evidence that several variants of gonadotropins and their receptors influence female reproductive health and ovarian response to exogenous gonadotropins. In more detail, variants in genes of follicle-stimulating hormone β-chain (FSH-B) and its receptor (FSH-R) seem to be the most promising candidates for a pharmacogenomic approach to controlled ovarian stimulation in assisted reproductive technologies. In the present review, we summarize the evidence regarding FSH-B and FSH-R variants, with special reference to their impact on reproductive health and assisted reproductive technology treatments.

Characterization of the miRNA regulators of the human ovulatory cascade

Ovarian follicular development and ovulation are complex and tightly regulated processes that involve regulation by microRNAs (miRNAs). We previously identified differentially expressed mRNAs between human cumulus granulosa cells (CGCs) from immature early antral follicles (germinal vesicle - GV) and mature preovulatory follicles (metaphase II - M2). In this study, we performed an integrated analysis of the transcriptome and miRNome in CGCs obtained from the GV cumulus-oocyte complex (COC) obtained from IVM and M2 COC obtained from IVF. A total of 43 differentially expressed miRNAs were identified. Using Ingenuity IPA analysis, we identified 7288 potential miRNA-regulated target genes. Two hundred thirty-four of these target genes were also found in our previously generated ovulatory gene library while exhibiting anti-correlated expression to the identified miRNAs. IPA pathway analysis suggested that miR-21 and FOXM1 cooperatively inhibit CDC25A, TOP2A and PRC1. We identified a mechanism for the temporary inhibition of VEGF during ovulation by TGFB1, miR-16-5p and miR-34a-5p. The linkage bioinformatics analysis between the libraries of the coding genes from our preliminary study with the newly generated library of regulatory miRNAs provides us a comprehensive, integrated overview of the miRNA-mRNA co-regulatory networks that may play a key role in controlling post-transcriptomic regulation of the ovulatory process.

Folliculogenic factors in photoregressed ovaries: Differences in mRNA expression in early compared to late follicle development

The early stages of ovarian folliculogenesis generally progress independent of gonadotropins, whereas later stages require signaling initiated by FSH. In Siberian hamsters, cycles of folliculogenesis are mediated by changes in photoperiod which depress the hypothalamic pituitary gonadal axis. Reduced gonadotropins lead to decreases in mature follicle development and ovulation; however, early stages of folliculogenesis have not been explored in regressed ovaries. We hypothesized that intraovarian factors that contribute predominantly to later stages of folliculogenesis would react to changes in photoperiod, whereas factors contributing to earlier stages would not change. To probe if the early stages of folliculogenesis continue in the photoinhibited ovary while late stages decline, we measured the mRNA abundance of factors that interact with FSH signaling (Fshr, Igf1, Cox2) and factors that can function independently of FSH (c-Kit, Kitl, Foxo3, Figla, Nobox, Sohlh1, Lhx8). While plasma FSH, antral follicles, and corpora lutea numbers declined with exposure to inhibitory photoperiod, the numbers of primordial, primary, and secondary follicles did not change. Expression of factors that interact with FSH signaling changed with changes in photoperiod; however, expression of factors that do not interact with FSH were not significantly altered. These results suggest that the photoinhibited ovary is not completely quiescent, as factors important for follicle selection and early follicle growth are still expressed in regressed ovaries. Instead, the lack of gonadotropin support that characterizes the non-breeding season appears to inhibit only final stages of folliculogenesis in Siberian hamsters.

Regulation by FSH of the dynamic expression of retinol-binding protein 4 in the mouse ovary

BACKGROUND

Ovarian retinoid homeostasis plays an important role in the physiological function of the ovary. Retinol-binding protein 4 (RBP4) acts as the mediator for the systemic and intercellular transport of retinol and is heavily involved in cellular retinol influx, efflux, and exchange. However, the expression patterns and regulatory mechanisms of Rbp4 in the ovary remain unclear.

METHODS

The expression pattern of ovarian Rbp4 was examined in immature mice during different developmental stages and in adult mice during different stages of the estrous cycle. The potential regulation and mechanisms of ovarian Rbp4 expression by estrogen and related gonadotropins in mouse ovaries were also investigated.

RESULTS

The present study demonstrated that the ovarian expression of Rbp4 remained constant before puberty and increased significantly in the peripubertal period. In adult female mice, the expression of Rbp4 increased at proestrus and peaked at estrus at both the mRNA and protein levels. The protein distribution of RBP4 was mainly localized in the granulosa cell and theca cell layer in follicles. In addition, the expression of Rbp4 was significantly induced by follicle-stimulating hormone (FSH) or FSH + luteinizing hormone (LH) in combination in immature mouse (3 weeks old) ovaries in vivo and in granulosa cells cultured in vitro, both at the mRNA and protein levels. In contrast, treatment with LH or 17β-estradiol did not exhibit any observable effects on ovarian Rbp4 expression. Transcription factors high-mobility group AT-hook 1 (HMGA1), steroidogenic factor 1 (SF-1), and liver receptor homolog 1 (LRH-1) (which have been previously shown to be involved in activation of Rbp4 transcription), also responded to FSH stimulation. In addition, H-89, an inhibitor of protein kinase A (PKA), and the depletion of HMGA1, SF-1, and LRH-1 by small interfering RNAs (siRNAs), resulted in a dramatic loss of the induction of Rbp4 expression by FSH at both the mRNA and protein levels.

CONCLUSIONS

These data indicate that the dynamic expression of Rbp4 is mainly regulated by FSH through the cAMP-PKA pathway, involving transcriptional factors HMGA1, SF-1, and LRH-1, in the mouse ovary during different stages of development and the estrous cycle.

Cellular and Animal Studies: Insights into Pathophysiology and Therapy of PCOS

Basic science studies have advanced our understanding of the role of key enzymes in the steroidogenesis pathway and those that affect the pathophysiology of PCOS. Studies with ovarian theca cells taken from women with PCOS have demonstrated increased androgen production due to increased CYP17A1 and HSD3B2 enzyme activities. Furthermore, overexpression of DENND1A variant 2 in normal theca cells resulted in a PCOS phenotype with increased androgen production. Notably, cellular steroidogenesis models have facilitated the understanding of the mechanistic effects of pharmacotherapies, including insulin sensitizers (e.g., pioglitazone and metformin) used for the treatment of insulin resistance in PCOS, on androgen production. In addition, animal models of PCOS have provided a critical platform to study the effects of therapeutic agents in a manner closer to the physiological state. Indeed, recent breakthroughs have demonstrated that natural derivatives such as the dietary medium-chain fatty acid decanoic acid (DA) can restore estrous cyclicity and lower androgen levels in an animal model of PCOS, thus laying the platform for novel therapeutic developments in PCOS. This chapter reviews the current understanding on the pathways modulating androgen biosynthesis, and the cellular and animal models that form the basis for preclinical research in PCOS, and sets the stage for clinical research.

Follicle-stimulating hormone potentiates the steroidogenic activity of chorionic gonadotropin and the anti-apoptotic activity of luteinizing hormone in human granulosa-lutein cells in vitro

Luteinizing hormone (LH) and choriogonadotropin (hCG) are glycoprotein hormones regulating ovarian function and pregnancy, respectively. Since these molecules act on the same receptor (LHCGR), they were traditionally assumed as equivalent in assisted reproduction techniques (ART), although differences between LH and hCG were demonstrated at molecular and physiological level. In this study, we demonstrated for the first time that co-treatment with a follicle-stimulating hormone (FSH) dose in the ART therapeutic range potentiates different LH- and hCG-dependent responses in vitro, measured in terms of cAMP, phospho-CREB, -ERK1/2 and -AKT activation, gene expression, progesterone and estradiol production in human granulosa-lutein cells (hGLC). We show that in the presence of FSH, hCG biopotency is about 5-fold increased, in the presence of FSH, in terms of cAMP activation. Accordingly, CREB phosphorylation and steroid production is increased under hCG and FSH co-treatment. LH effects, evaluated as steroidogenic cAMP/PKA pathway activation, do not change in the presence of FSH, which, however, increases LH-dependent ERK1/2 and AKT, but not CREB phosphorylation, resulting in anti-apoptotic effects. The different modulatory activity of FSH on LH and hCG action in vitro corresponds to their different physiological functions, reflecting proliferative effects exerted by LH during the follicular phase and before trophoblast development, and the high steroidogenic potential of hCG requested to sustain pregnancy from the luteal phase onwards.

A Dietary Medium-Chain Fatty Acid, Decanoic Acid, Inhibits Recruitment of Nur77 to the HSD3B2 Promoter In Vitro and Reverses Endocrine and Metabolic Abnormalities in a Rat Model of Polycystic Ovary Syndrome

Hyperandrogenism is the central feature of polycystic ovary syndrome (PCOS). Due to the intricate relationship between hyperandrogenism and insulin resistance in PCOS, 50%-70% of these patients also present with hyperinsulinemia. Metformin, an insulin sensitizer, has been used to reduce insulin resistance and improve fertility in women with PCOS. In previous work, we have noted that a dietary medium-chain fatty acid, decanoic acid (DA), improves glucose tolerance and lipid profile in a mouse model of diabetes. Here, we report for the first time that DA, like metformin, inhibits androgen biosynthesis in NCI-H295R steroidogenic cells by regulating the enzyme 3β-hydroxysteroid dehydrogenase/Δ5-Δ4-isomerase type 2 (HSD3B2). The inhibitory effect on HSD3B2 and androgen production required cAMP stimulation, suggesting a mechanistic action via the cAMP-stimulated pathway. Specifically, both DA and metformin reduced cAMP-enhanced recruitment of the orphan nuclear receptor Nur77 to the HSD3B2 promoter, coupled with decreased transcription and protein expression of HSD3B2. In a letrozole-induced PCOS rat model, treatment with DA or metformin reduced serum-free testosterone, lowered fasting insulin, and restored estrous cyclicity. In addition, DA treatment lowered serum total testosterone and decreased HSD3B2 protein expression in the adrenals and ovaries. We conclude that DA inhibits androgen biosynthesis via mechanisms resulting in the suppression of HSD3B2 expression, an effect consistently observed both in vitro and in vivo. The efficacy of DA in reversing the endocrine and metabolic abnormalities of the letrozole-induced PCOS rat model are promising, raising the possibility that diets including DA could be beneficial for the management of both hyperandrogenism and insulin resistance in PCOS.

Hypomethylation of the LH/choriogonadotropin receptor promoter region is a potential mechanism underlying susceptibility to polycystic ovary syndrome

Our previous genome-wide association study identified LH/choriogonadotropin receptor (LHCGR) as a susceptibility gene for polycystic ovary syndrome (PCOS). The objective of this study was to determine whether the genetic or epigenetic components associated with LHCGR participate in the pathogenesis of PCOS. The exons and flanking regions of LHCGR were sequenced from 192 women with PCOS, and no novel somatic mutations were identified. In addition, the methylation statuses of 6 cytosine-phosphate-guanine (CpG) sites in the promoter region of LHCGR were measured by pyrosequencing using peripheral blood cells from 85 women with PCOS and 88 control women. We identified 2 hypomethylated sites, CpG -174 (corrected P = .018) and -111 (corrected P = .006). Bisulfite sequencing then was performed to replicate these findings and detect additional CpG sites in the promoter. CpG +17 was significantly hypomethylated in women with PCOS (corrected P = .02). Methylation statuses were further evaluated using granulosa cells (GCs), and the region described was hypomethylated as a whole (P = .004) with 8 significantly hypomethylated sites (CpG -174, -148, -61, -43, -8, +10, +17, and +20). Transcription of LHCGR was elevated in women with PCOS compared with that in control women (P < .01). These findings were consistent with the decreased LHCGR methylation status associated with PCOS. The tendency of LHCGR to be hypomethylated across different tissues and its corresponding expression level suggest that hypomethylation of LHCGR is a potential mechanism underlying susceptibility to PCOS. Further studies are needed to evaluate whether a causal relationship exists between LHCGR methylation status and PCOS.

Prolonged remission of severe Cushing syndrome without adrenalectomy in an infant with McCune-Albright syndrome

A 4 month-old girl presented with severe Cushing syndrome caused by McCune-Albright syndrome. After undergoing 19 months of pharmacologic suppression of cortisol production, she has been in clinical remission for more than 6 years. Adrenalectomy may be avoidable even in severe cases of Cushing syndrome associated with McCune-Albright syndrome.

Effects of bushen tiaochong recipe containing serum on ovarian granulosa cell proliferation, steroidogenesis and associated gene expression in rats

OBJECTIVE

To observe the effect of bushen tiaochong recipe (BSTCR) on rats' ovarian granulosa cell (GC) proliferation, steroidogenesis and follicle-stimulating hormone receptor (FSHR), and insulin-like growth factor-1 (IGF-1) mRNA expression using serum pharmacological method.

METHODS

Rats' GCs were incubated with 10% blank serum (as negative control group), follicle-stimulating hormone (FSH)-containing serum (S-FSH, as positive control group), or BSTCR (in different dosages) containing serum (S-BSTCR, as the BSTCR groups) for 48 h. 3H-TdR incorporation was then performed; DNA was measured to analyze the distribution of GCs in the cell cycle and their proliferation index (PI) using a flow cytometer; estradiol (E2) and progesterone (P) content in the culture fluid were examined by radioimmunoassay; and levels of FSHR and IGF-1 mRNA expression in GCs were measured by real-time RT-PCR.

RESULTS

A dose-dependent increase of 3H-TdR incorporation in GC was shown in the BSTCR groups. Cells in G0/G1 phase had markedly less, while those in S phase had a significantly higher increase in the BSTCR groups compared with the negative control group. A high value of PI was also shown in the BSTCR groups, especially in the high dose group where the influence of cell proliferation was stronger than that in the positive control group. The levels of E2 and P in the BSTCR groups of all dosages were significantly higher than those in the negative control group, and did not show any significant difference compared with those in the positive control group. Levels of FSHR and IGF-1 mRNA expression in the BSTCR groups increased in a dose-dependent manner at levels higher than those in the negative control group.

CONCLUSION

S-BSTCR can obviously stimulate the proliferation and steroidogenesis of ovarian GCs. It is speculated that BSTCR could play a regulatory action on ovarian function through two different pathways of endocrine and autocrine by promoting FSHR and IGF-1 mRNA expression.

Real-time monitoring of cAMP response element binding protein signaling in porcine granulosa cells modulated by ovarian factors

The present study was performed to establish a real-time monitoring of the cAMP response element binding protein (CREB) signalling using granulosa cells, and to assess the modulation of CREB activity by potential ovarian autocrine/paracrine and oocyte-derived factors. Granulosa cells were isolated from porcine follicles and cultured for 2 days, and then transfected with CRE-containing pGL3. The cells were directly stimulated or cultured with FSH, LH, forskolin, or a permeable cAMP analog, and/or IGF-I, EGF, bFGF, TGF-beta2 or TNF-alpha, or cumulus-oocyte complex (COCs) for the real-time monitoring of CREB signaling. The activation pattern of CREB signaling consisted of three distinct phases, i.e., burst, attenuation and refractory. In contrast to FSH, LH, and forskolin, a cAMP analog induced the prolonged activation, although three distinct phases were observed at its high concentration. Of all the autocrine/paracrine factors, only IGF-I slightly induced CREB activity. On the other hand, TGF-beta2 and TNF-alpha significantly repressed FSH-stimulated transcriptional activation of CREB by 30% (P < 0.05) and 45% (P < 0.05), respectively. Additionally, coculture with COCs caused a significant suppression of transcriptional activation of CREB signaling stimulated by FSH. These results indicate that ovarian autocrine/paracrine factors such as IGF-I, TGF-beta2, TNF-alpha and oocyte-derived factors modulate the CREB signaling. The present study provides a new approach for direct signaling study on transcription factors under the influences of potential factors.

[Apoptosis of the follicular cells: its implication in ovarian induction protocols]

Atresia, a degenerative process through which many follicles are removed from the grown pool of follicles involves apoptotic changes in the follicular cells. This review analyses the endocrine regulation of apoptotic cell death in ovarian follicle. FSH is the major survival factor for preovulatory follicle but follicle integrity, in vitro, was necessary to its action on granulosa cell. The role of LH is more ambivalent. FSH and LH exert their activity via activation of the cAMP signal. High levels of intracellular cAMP could enhance steroidogenesis and in the same time induce apoptosis in granulosa cells. Moreover, no correlation between steroidogenesis and apoptosis can be established. During ovarian stimulation in IVF protocol, the use of LH, of coasting and of GnRH agonists and antagonists could be deleterious in follicle survival.

Gonadotrophins in ovulation induction

For anovulatory women who fail to ovulate or conceive with clomiphene citrate, gonadotrophin ovulation induction has been the conventional second-line therapy. The aim of treatment is to achieve monofollicular development and ovulation. This differs fundamentally from the aim of ovarian stimulation for IVF, in which multiple follicular development is the goal. The small therapeutic window of ovulation induction requires a rigorous approach to monitoring, and willingness to cancel the cycle when multiple follicle development occurs. The two most widely used approaches are the low-dose step-up and the step-down protocols. While the latter more closely mimics the normo-ovulatory cycle, outcomes are similar. For safety reasons, the step-down protocol has not been widely adopted. The principle risks of ovulation induction are ovarian hyperstimulation syndrome and multiple pregnancy. There is a need to individualize treatment if outcomes are to be optimized. The role of adjuvant therapies remains unclear. However, prediction models based on initial screening parameters enable the optimal dose of FSH to be determined, and the identification of patients with a poor prognosis for successful treatment.

Autocrine role of transforming growth factor beta1 on rat granulosa cell proliferation

We evaluated the effects of transforming growth factor beta1 (TGFbeta1), alone or in combination with FSH and estradiol, on DNA synthesis in primary cultures of immature rat granulosa cells. 3H-Thymidine incorporation was significantly stimulated by TGFbeta1 (5.6-fold). This effect was enhanced by FSH (20 ng/ml, 27.7-fold) or estradiol (100 ng/ml, 13.4-fold) or by a combination of both hormones (59.2-fold). Measurement of TGFbeta bioactivity showed the presence of significant amounts of TGFbeta in conditioned medium from granulosa cell cultures, and most of the activity was present in the latent form. FSH alone or in combination with estradiol produced a marked suppression of the production of latent and active TGFbeta. Activated conditioned medium from control cultures of granulosa cell elicited a 1.4-fold increase in thymidine incorporation. This effect was markedly amplified by FSH (3-fold) and estradiol (4.3-fold) and by a combination of both (8.7-fold). The peptide containing the cell-binding domain of fibronectin (RGDSPC) partially inhibited thymidine incorporation stimulated by TGFbeta1. Fibronectin did not synergize with FSH, and the interaction between TGFbeta1 and FSH was even observed in the presence of this protein. The conclusions reached were as follows: 1) TGFbeta1 is an autocrine stimulator of rat granulosa cell DNA synthesis, 2) FSH and estradiol produce a suppression of latent and active TGFbeta production but markedly amplify TGFbeta action, presumably at a postreceptor level, and 3) the stimulatory effects of TGFbeta1 may be only partly mediated by the increased fibronectin secretion.

Gonadotropic control of ovarian follicular growth and development

Development-related paracrine cues that sensitize follicles to follicle stimulating hormone (FSH) and luteinizing hormone (LH) are crucial to the emergence of a single dominant follicle in each ovulatory menstrual cycle. Sex steroids, insulin-like growth factors and members of the transforming growth factor-beta superfamily are key players in the follicular paracrine system. FSH acts through membrane-associated granulosa cell receptors (FSHR) to stimulate granulosa cell proliferation and differentiation. The most responsive follicle at the beginning of the cycle is the first to produce estrogen and express granulosa cell LHR. Paracrine signalling activated by FSH and LH sustains growth and oestrogen secretion until an ovulation-inducing LH surge is discharged by the pituitary gland. LH then reprograms granulosa cell function, leading to terminal differentiation (luteinization) rupture of the follicle wall, and release of the fertilizable egg. The genes regulated by the LH surge orchestrate profound changes in sex steroid production, metabolism and action which are necessary for ovulation. Preovulatory granulosa cells also increase their ability to metabolise cortisone to cortisol, which may be part of a local anti-inflammatory mechanism to promote rapid healing of the ruptured ovarian surface.

Adenovirus-directed expression of a nonphosphorylatable mutant of CREB (cAMP response element-binding protein) adversely affects the survival, but not the differentiation, of rat granulosa cells

Although usually considered to be a constitutively expressed protein, in the primate ovary the expression of CREB (cAMP response element-binding protein) is extinguished after ovulation, and its loss is temporally associated with the cessation of proliferation of luteal cells and the ultimate commitment of the corpus luteum to undergo regression. To determine the cellular consequences of the loss of CREB expression, we expressed a nonphosphorylatable mutant of CREB (CREB M1) in primary cultures of rat granulosa cells using a replication-defective adenovirus vector. Expression of CREB M1 did not block granulosa cell differentiation as assessed by acquisition of the ability to produce estrogen and progesterone in response to FSH or forskolin. However, granulosa cells expressing CREB M1, but not adenovirus-directed beta-galactosidase or enhanced green fluorescent protein, exhibited a 35% reduction in viability that was further reduced to 65% after stimulation with 10 microM forskolin. These results demonstrate that the trophic effects of cAMP (proliferation and survival) on ovarian granulosa cells are functionally separate from the effects of cAMP on differentiation and provide novel evidence that CREB may function as a cell survival factor in the ovary. The separation of signaling pathways that govern differentiation and survival in the ovary thereby provides a mechanism by which progesterone production, which is absolutely essential for the maintenance of pregnancy, can continue despite the cessation of proliferation of luteal cells and their commitment to cell death (luteolysis).

Regulation of the Primate Corpus Luteum: Cellular and Molecular Perspectives

The process of luteinization, during which follicular granulosa cells are transformed into luteal cells, is accompanied by dramatic changes in the responses of luteal cells to luteinizing hormone (LH) and cAMP. The goal of this review is to summarize the findings of recent studies in monkeys, which have shown that the expression of the cAMP-dependent nuclear transcription factor CREB (cAMP-response element-binding protein) ceases upon luteinization, and also to suggest possible consequences of its loss on corpus luteum function and lifespan.

Growth hormone and ovarian function

Growth and reproductive development are closely co-ordinated during puberty but there is also evidence that growth hormone (GH) may have a physiological role in adult ovarian function. Both GH and the insulin-like growth factors (IGFs) have been shown to augment granulosa cell proliferation and steroidogenesis in the human Graafian follicle, suggesting that GH may act as a 'co-gonadotrophin' at ovarian level. Furthermore, the intra-ovarian 'IGF system' (i.e. IGFs and IGF-binding proteins) may be implicated in folicular atresia and in disorders of follicular function associated with polycystic ovary syndrome (PCOS). The clinical importance of GH to ovarian function in the adult is illustrated by the finding that adjuvant GH treatment reduces the dose of exogenous gonadotrophin which is required to induce folliculogenesis in women with hypogonadotrophic hypogonadism. There is, however, no evidence that GH supplementation is of significant clinical benefit in the management of patients with other ovulatory disorders--including PCOS--or in superovulation protocols for in vitro fertilization.

Melatonin and exposure to constant light/darkness affects ovarian follicular kinetics and estrous cycle in Indian desert gerbil Meriones hurrianae

Melatonin mediates photoperiodic influence on reproduction and constant light and darkness affect pineal biosynthesis of melatonin. The present study was undertaken to assess the effects of melatonin and drastic photoperiodic changes on reproduction in a tropical desert species with a fossorial lifestyle. Ovarian follicular kinetics and estrous cycle were studied in the Indian desert gerbil Meriones hurrianae, after treatment with melatonin and exposure to constant light (LL) and darkness (DD) regimes. Melatonin treatment increased (P < 0.001) ovarian weights without changing the uterine weights. While exposure to LL decreased (P < 0.001) both ovarian and uterine weights, exposure to DD had no effect on these weights. Follicular kinetics of growing and regressing follicles revealed that ovaries of melatonin-treated and DD-exposed animals had significantly more growing follicles. Melatonin treatment increased all types of growing follicles, especially antral and Graafian follicles. Exposure to DD increased all types of growing follicles, with the medium sized antral and Graafian follicles being significant (P < 0.01). In contrast to stimulation of follicular growth by melatonin and DD, LL caused regression of all stages of follicular growth and also reduced the number of small preantral follicles. Melatonin treatment increased (P < 0.001) the length of estrous cycle (5.08 to 7.29 days). Gerbils treated with melatonin, exposed to LL and DD, had a longer (P < 0.001) metestrus. Animals held in LL, had the least number (P < 0.001) of estrous smears (1 in 30 days). The results suggest that melatonin is involved in growth of ovarian follicles in the Indian desert gerbil.

Local control of ovarian steroidogenesis

A number of putative paracrine factors are now thought to interact with FSH in the control of ovarian steroidogenesis. The relative importance of these factors remains to be determined, but the presence of the insulin-like growth factors and their binding proteins and the mechanism of control of the latter through the local production of proteases suggests a role for this system in folliculogenesis. We have demonstrated over-production of steroid hormones in tissue from women with polycystic ovaries. Theca cells in monolayer culture produced excessive amounts of progesterone and androstenedione and granulosa cell oestradiol production was considerably enhanced in response to FSH. Recent evidence points to a genetic defect in the expression or translation of steroidogenic hormones as a cause of excess androgen production, but the gene or genes involved has not been established. Data from our group suggest that granulosa cells from anovulatory polycystic ovaries are prematurely matured and we hypothesize that this is due to the interaction of the raised circulating insulin levels with LH in these follicles, an interaction that results in arrested follicular growth.

Role of androgens in follicle maturation and atresia

Androgens are products of progestogen metabolism, intermediates in oestrogen biosynthesis and local regulators of ovarian function. Current understanding of intraovarian androgen formation, metabolism and action is reviewed, highlighting the contribution of androgens to the paracrine regulation of follicular maturation and atresia. Any factor that alters intracellular cAMP levels is a potential modulator of granulosa cell differentiation, and hence follicular development. Androgen appears to modulate gonadotrophin action on granulosa cells through amplification of cAMP-mediated post-receptor signalling. Here it is argued that during intermediate stages of follicular development, locally produced androgen acts via granulosa cell androgen receptors (AR) to promote follicle-stimulating hormone (FSH)-induced granulosa cell differentiation through amplifying cAMP-mediated post-receptor signalling. During late pre-ovulatory follicular development, higher concentrations of cAMP caused by stimulation with luteinizing hormone (LH) suppress granulosa cell proliferation and down-regulate some of the genes induced by FSH at earlier stages of pre-ovulatory development, including aromatase activity. Other granulosa cell functions, including progesterone synthesis, are enhanced by the high concentrations of cAMP induced by LH. There is experimental evidence from studies of rat and non-human primate (common marmoset) ovaries that AR levels in granulosa cells decline during pre-ovulatory follicular maturation. Since androgens augment FSH-induced cAMP formation and action, loss of AR could be a means of avoiding inappropriately high cAMP levels and hence avoiding premature activation of 'high-tone' cAMP-response genes that lead to atresia. Negative regulation of the granulosa cell AR could be part of the intra-ovarian mechanism that determines which follicle(s) becomes dominant and secretes oestrogen in the normal menstrual cycle.

Concerted stimulation of rat granulosa cell deoxyribonucleic acid synthesis by sex steroids and follicle-stimulating hormone

Although follicle-stimulating hormone (FSH) and estrogens are known to be the main physiological stimuli for the development of the ovarian follicle in mammals, their growth-promoting activity has not been clearly established "in vitro". Furthermore, experimental evidence indicates that FSH and estradiol can independently inhibit granulosa cell proliferation. The present study was aimed at examining the effect of sex steroids in combination with FSH, on DNA synthesis in rat granulosa cells cultured in completely defined medium. Estradiol and FSH, when added separately, produced a significant inhibition of [3H] thymidine incorporation. In contrast, a combination of a low dose of FSH (20 ng/ml) with estradiol (100 ng/ml) produced a shift in the period of maximal DNA synthesis from 96 to 48 h after plating. Dose response studies showed that estradiol effects were produced at physiological intraovarian concentrations (1-100 ng/ml), whereas the effects of FSH were biphasic, with high doses (200 ng/ml) being inhibitory. A similar biphasic dose response curve was observed with increasing concentrations of a cAMP derivative in the presence of maximally effective doses of either an aromatizable steroid (androstenedione), insulin or insulin-like growth factor I. Non-aromatizable androgens (5alpha-dihydrotestosterone, 5alpha-androstane 3alpha-17beta diol and androsterone) showed a potency comparable to that of estradiol. The effect of 5alpha-dihydrotestosterone was completely blocked by a specific antiandrogen (hydroxy-flutamide), indicating that it was mediated by the androgen receptor. The effects of estradiol and androgens were not additive. The interaction between estradiol and FSH was further amplified in the presence of a maximally effective dose of insulin. Data presented herein indicate that both estrogens and androgens are able to elicit a mitogenic response in purified granulosa cells, cultured in a completely defined medium, provided the cells are stimulated by a physiological dose of FSH. These results suggest that, during follicular development, the stimulus for granulosa cell proliferation is given by the concerted action of steroid and peptide hormones acting through different signalling pathways.

Regulation of ovarian follicle differentiation in gonadotrophin-stimulated rats

The aim of the present study was to investigate the regulation of the in vitro DNA synthesis of ovarian cells recovered from prepubertal rats 48 h after administration of pregnant mare's serum gonadotrophin alone (granulosa cells) or followed by human chorionic gonadotrophin (luteal cells). Isolated granulosa cells were cultured in serum-free medium, different stimuli added for periods of 48 h, and 3H-thymidine incorporation was measured. Both follicle-stimulating hormone (FSH) and luteinizing hormone (LH) inhibited 3H-thymidine incorporation by cultured granulosa cells in a dose-dependent manner (FSH: 10, 100, 200 ng/mL = 26, 41, 49% inhibition, respectively; LH: 0.1, 1, 10 ng/mL = 11, 37, 75% inhibition, respectively). On the other hand, estradiol was found to stimulate 3H-thymidine incorporation in granulosa cells (Estradiol: 5, 50, 500 ng/mL = 17, 37, 76% stimulation, respectively). In luteal cells, the rate of basal 3H-thymidine incorporation was very low (granulosa cells: 2560 +/- 310; luteal cells: 661 +/- 92 cpm/100,000 cells) and not modified by any stimulus. To determine the possible production of an inhibitory growth factor by the early corpus luteum, 3H-thymidine incorporation by granulosa cells was assessed in the presence of 10% conditioned media (CM) recovered from luteal cell cultures. A marked inhibition both in basal and estradiol-stimulated 3H-thymidine incorporation was observed (74 and 76% of inhibition, respectively). Results suggest that an inhibitory growth factor produced by luteal cells after luteinizing gonadotrophin stimulus could be involved in the differentiation of growing follicles to corpus luteum.

Proliferation and progesterone production of ovine luteal cells from several stages of the estrous cycle: effects of fibroblast growth factors and luteinizing hormone

This study was conducted to evaluate the effects of fibroblast growth factor 1 (FGF-1), fibroblast growth factor 2 (FGF-2), or luteinizing hormone (LH) on proliferation and progesterone secretion of ovine luteal cells from days 5, 10, or 15 after estrus (estrus = day 0; n = 4 or 5 ewes/day). After enzymatic dispersion, luteal cells were incubated in the presence or absence of various doses of FGF-1, FGF-2, LH, or fetal bovine serum (FBS) (positive control) in serum-free media for 7 days in 24-well plates. Cells were counted on day 7 of culture and media analyzed for progesterone concentration. For all treatments, maximal effects (Emax) and dissociation constants (KD) were calculated. In addition, luteal cells were cultured in eight-chamber slides and treated as above, but on day 7 of culture cells were fixed and stained for the presence of 3beta-hydroxy-delta 5-steroid dehydrogenase (3beta HSD). The number of steroidogenic (3beta HSD positive) cells per unit area was counted for control cultures (no treatment) and cultures treated with the most effective doses of FGF-1, FGF-2, LH, OR FBS in proliferation and (or) progesterone assays. FGF-1, FGF-2, AND FBS stimulated (p < 0.05) proliferation of luteal cells from all stages of luteal development in a dose-dependent manner. In addition, LH increased (p < 0.01) the number of 3beta HSD-positive cells across all stages of luteal development. Moreover, LH and FBS increased (p < 0.05) progesterone secretion by luteal cells from all stages in a dose-responsive manner, but the effects of FGF-1 and FGF-2 were variable. For proliferation, the Emax of all factors was greatest (p < 0.01) on day 5, whereas the KD values were similar across days of the estrous cycle. For progesterone production, the Emax and KD of LH and FBS were similar and did not differ across the estrous cycle. These data demonstrate the luteal cells from the early luteal phase of the estrous cycle exhibit the greatest ability to proliferate and (or) increase their progesterone secretion in response to FGF-1, FGF-2, LH, or FBS. In addition, although LH does not affect the total number of luteal cells in culture, it does increase the number of steroidogenic cells. These data indicate that in addition to LH, fibroblast growth factors may be involved in regulation of luteal growth and differentiation in ewes.

Ovarian follicular growth, ovulation and atresia. Endocrine, paracrine and autocrine regulation

This chapter describes a finely tuned series of events that results in ovarian morphological changes including follicular growth, dominant follicle selection, oocyte development, ovulation, and corpus luteum formation. These changes are under the obligate control of the pituitary gonadotropins FSH and LH. The signaling mechanisms whereby the gonadotropins stimulate these changes in the ovary are now well described. The gonadotropin membrane receptors have been cloned and the cellular events proceeding from receptor binding to phosphorylation of protein gene regulators, such as CREB, have been elucidated. A whole series of intraovarian paracrine and autocrine regulators have been described as having the capability of "fine tuning" the effects of gonadotropins (see Tables I and II), and they are likely involved in dominant follicle selection and the demise of the corpus luteum. The roles of the individual paracrine regulators are, as of yet, not well known, but the IGF system offers an attractive paradigm for these intraovarian factors. Lastly, we have described the explosion of data on intracellular and intranuclear regulators. The challenge for us will be to understand the physiological significance of the seemingly unlimited number of regulatory possibilities. Much has been learned concerning the regulation of the morphological changes seen in the ovary, but much more remains to be elucidated.

Severe endocrine and nonendocrine manifestations of the McCune-Albright syndrome associated with activating mutations of stimulatory G protein GS

McCune-Albright syndrome (MCAS) is a sporadic disease classically including polyostotic fibrous dysplasia, café au lait spots, sexual precocity, and other hyperfunctional endocrinopathies. An activating missense mutation in the gene for the alpha subunit of GS, the G protein that stimulates cyclic adenosine monophosphate formation, has been reported to be present in these patients. The mutation is found in variable abundance in different affected endocrine and nonendocrine tissues, consistent with the mosaic distribution of abnormal cells generated by a somatic cell mutation early in embryogenesis. We describe three patients with MCAS who had profound endocrine and nonendocrine disease and who died in childhood. Two of the patients were severely ill neonates whose complex symptoms did not immediately suggest MCAS. A mutation of residue Arg201 of GS alpha was found in affected tissues from all three children. A review of the literature and unpublished case histories emphasizes the existence of other patients with severe and unusual clinical manifestations. We conclude that the manifestations of MCAS are more extensive than is generally appreciated, and may include hepatobiliary disease, cardiac disease, other nonendocrine abnormalities, and sudden or premature death.

Establishment of steroidogenic granulosa cell lines expressing follicle stimulating hormone receptors

Follicle stimulating hormone (FSH) plays an important role in the regulation of oogenesis, spermatogenesis and production of steroid hormones. Receptors to FSH, which are uniquely expressed in ovarian granulosa and testicular Sertoli cells, are rapidly lost in tissue culture conditions and upon cell transformation. We have succeeded, by triple transfection of primary rat granulosa cells with SV40 DNA, Ha-ras oncogene and an FSH receptor expression plasmid, to establish stable steroidogenic cell lines expressing FSH receptors. The cell lines respond to rat, ovine and bovine FSH, which stimulate progesterone production at levels comparable to primary granulosa cells obtained from preovulatory follicles. No steroidogenic response is detected upon stimulation with ovine luteinizing hormone or human chorionic gonadotropin. The steroidogenic response is accompanied by de novo appearance of adrenodoxin which serves as a marker for the mitochondrial steroidogenic enzyme system. These cells express approximately 27,000 receptors per cell with a Kd of 100-115 pM. This Kd is close to the value calculated for the native receptor. The ED50 for the steroidogenic response to ovine FSH is 200 pM, suggesting a tight coupling between receptor activation and the steroidogenic response. FSH induces pronounced morphological changes in the established cell lines, which are also characteristic of primary granulosa cells. These FSH responsive cell lines can serve as a useful model for the study of the structure and function of the FSH receptor and the effect of oncogenes on its expression.