Distinct Regulation by Steroids of Messenger RNAs for FSHR and CYP19A1 in Bovine Granulosa Cells

Regulation of granulosa cell cocaine and amphetamine regulated transcript (CART) binding and effect of CART signaling inhibitor on granulosa cell estradiol production during dominant follicle selection in cattle

We previously established a potential role for cocaine and amphetamine regulated transcript (CARTPT) in dominant follicle selection in cattle. CARTPT expression is elevated in subordinate versus dominant follicles, and treatment with the mature form of the CARTPT peptide (CART) decreases follicle-stimulating hormone (FSH)-stimulated granulosa cell estradiol production in vitro and follicular fluid estradiol and granulosa cell CYP19A1 mRNA in vivo. However, mechanisms that regulate granulosa cell CART responsiveness are not understood. In this study, we investigated hormonal regulation of granulosa cell CART-binding sites in vitro and temporal regulation of granulosa cell CART-binding sites in bovine follicles collected at specific stages of a follicular wave. We also determined the effect of inhibition of CART receptor signaling in vivo on estradiol production in future subordinate follicles. Granulosa cell CART binding in vitro was increased by FSH, and this induction was blocked by estrogen receptor antagonist treatment. In follicles collected in vivo at specific stages of a follicular wave, granulosa cell CART binding in the F2 (second largest), future subordinate follicle increased during dominant follicle selection. Injection into the F2 follicle (at onset of diameter deviation) of an inhibitor of the o/i subclass of G proteins (previously shown to block CART actions in vitro) resulted in increased follicular fluid estradiol concentrations in vivo. Collectively, results demonstrate hormonal regulation of granulosa cell CART binding in vitro and temporal regulation of CART binding in subordinate follicles during dominant follicle selection. Results also suggest that CART signaling may help suppress estradiol-producing capacity of the F2 (subordinate) follicle during this time period.

Growth factor receptor-bound protein 14: a potential new gene associated with oocyte competence

The Grb14 protein is a member of the Grb7 protein family. This protein family acts by binding to tyrosine kinase receptors, promoting cell proliferation and differentiation. There is evidence of the involvement of tyrosine kinase factors in the bovine oocyte maturation process. However, Grb14 has not been studied for bovine cumulus–oocyte complexes (COCs). The aim of the present study was to characterize Grb14 mRNA expression in bovine COCs during follicular development. Furthermore, we demonstrated that the expression of Grb14 mRNA is not regulated by estradiol. mRNA expression of Grb14 was assessed in 480 COCs from follicles of different sizes (1–3, 4–6, 6–8 or >8 mm) by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Grb14 mRNA expression decreased in COCs throughout follicular growth (P < 0.05). The role of estradiol in the expression of Grb14 mRNA in COCs was studied. Grb14 mRNA abundance did not differ in COCs cultured in the presence or absence of 17β-estradiol or fulvestrant. In conclusion, we showed that Grb14 mRNA is downregulated in COCs during antral follicle development, a finding that suggests a role for Grb14 in oocyte competence.

CYP19 gene variants affect the assisted reproduction outcome of women with polycystic ovary syndrome

OBJECTIVE

Cytochrome P450 aromatase catalyzes the irreversible transformation of androgens into estrogens. The association of CYP19(TTTA)n polymorphism with the hormonal profile and the assisted reproduction outcome of women with polycystic ovary syndrome (PCOS) was explored.

METHODS

One hundred and thirty-two women with PCOS and 200 with male-factor infertility, as controls, participated in the current study. The CYP19(TTTA)n polymorphism was genotyped, while the hormonal profile was determined at the third day of the menstrual cycle. During oocyte retrieval, the follicular size, the follicle and oocyte numbers were recorded.

RESULTS

Genotype analysis revealed 6 CYP19(TTTA)n alleles with 7-12 repeats. In PCOS women, the CYP19(TTTA)7 allele presence was associated with lower serum E2 levels at the third day of the menstrual cycle (p < 0.009), lower large follicle (p < 0.02) and total oocyte numbers (p = 0.006), but with significantly higher pregnancy rates after assisted reproduction (p < 0.004).

CONCLUSIONS

Potential associations of the CYP19(TTTA)7 allele with ovarian response to standard gonadotrophin stimulation and with assisted reproduction outcome were found in PCOS women, probably due to androgen/estrogen ratio alterations.

Ontogeny of the ovary in polycystic ovary syndrome

Activation of primordial follicles into the growing pool, selection of the dominant follicle, and its eventual ovulation require complex endocrine and metabolic interactions as well as intraovarian paracrine signals to coordinate granulosa cell proliferation, theca cell differentiation, and oocyte maturation. Early preantral follicle development relies mostly upon mesenchymal-epithelial cell interactions, intraovarian paracrine signals, and oocyte-secreted factors, whereas development of the antral follicle depends on circulating gonadotropins as well as locally derived regulators. In women with polycystic ovary syndrome (PCOS), ovarian hyperandrogenism, hyperinsulinemia from insulin resistance, and altered intrafollicular paracrine signaling perturb the activation, survival, growth, and selection of follicles, causing accumulation of small antral follicles within the periphery of the ovary, giving it a polycystic morphology. Altered adipocyte-ovarian interactions further compound these adverse events on follicle development and also can harm the oocyte, particularly in the presence of increased adiposity. Finally, endocrine antecedents of PCOS occur in female infants born to mothers with PCOS, which suggests that interactions between genes and the maternal-fetal hormonal environment may program ovarian function after birth.

Prostaglandin F2α regulation of mRNA for activating protein 1 transcriptional factors in porcine corpora lutea (CL): lack of induction of JUN and JUND in CL without luteolytic capacity

Porcine corpora lutea (CL) develop sensitivity to regression by prostaglandin F2α (PGF2α), termed luteolytic capacity, about 13 d after estrus. We postulated that PGF2α regulation of activating protein 1 (AP-1) transcriptional factor expression underlies acquisition of luteolytic capacity. CL were collected from gilts on day 9 (estrous cycle) or day 17 (pseudopregnancy) before or after PGF2α treatment with mRNA measured for FOS, FOSB, FOSL1, FOSL2, JUN, JUNB, and JUND and the AP-1 target genes CCL2 and SERPINE1. At 0.5 h after PGF2α, both day-9 and day-17 CL had increased (P < 0.01) mRNA for FOS (2,225% and 1,817%), JUNB (237% and 358%), and FOSB (1,060% and 925%). Intriguingly, at 0.5 h after PGF2α there was increased (P < 0.01) mRNA encoding JUN (1,099%) and JUND (300%) in day-17 but not day-9 CL. At 10 h after PGF2α there was elevated FOSB mRNA in day-17 (771%) but not day-9 CL and no PGF2α-induced change in FOS, JUN, JUND, and JUNB mRNA in day-9 or day-17 CL. Treatment with PGF2α increased mRNA for AP-1-responsive genes, CCL2 at 0.5 h (202%) and CCL2 and SERPINE1 at 10 h (719% and 1,515%), only in day-17 CL. Thus, many of the fos family of transcription factors are dramatically induced by PGF2α in CL with or without luteolytic capacity. However, PGF only induced JUN and JUND expression in CL with luteolytic capacity, a finding that may be key for understanding the acquisition of luteolytic capacity, given that JUN is the only AP-1 family member with strong N-terminal trans-activation activity.

Norepinephrine stimulates progesterone production in highly estrogenic bovine granulosa cells cultured under serum-free, chemically defined conditions

BACKGROUND

Since noradrenergic innervation was described in the ovarian follicle, the actions of the intraovarian catecholaminergic system have been the focus of a variety of studies. We aimed to determine the gonadotropin-independent effects of the catecholamine norepinephrine (NE) in the steroid hormone profile of a serum-free granulosa cell (GC) culture system in the context of follicular development and dominance.

METHODS

Primary bovine GCs were cultivated in a serum-free, chemically defined culture system supplemented with 0.1% polyvinyl alcohol. The culture features were assessed by hormone measurements and ultrastructural characteristics of GCs.

RESULTS

GCs produced increasing amounts of estradiol and pregnenolone for 144h and maintained ultrastructural features of healthy steroidogenic cells. Progesterone production was also detected, although it significantly increased only after 96h of culture. There was a highly significant positive correlation between estradiol and pregnenolone production in high E2-producing cultures. The effects of NE were further evaluated in a dose-response study. The highest tested concentration of NE (10 (-7) M) resulted in a significant increase in progesterone production, but not in estradiol or pregnenolone production. The specificity of NE effects on progesterone production was further investigated by incubating GCs with propranolol (10 (-8) M), a non-selective beta-adrenergic antagonist.

CONCLUSIONS

The present culture system represents a robust model to study the impact of intrafollicular factors, such as catecholamines, in ovarian steroidogenesis and follicular development. The results of noradrenergic effects in the steroidogenesis of GC have implications on physiological follicular fate and on certain pathological ovarian conditions such as cyst formation and anovulation.

Elevated level of 17β-estradiol is associated with overexpression of FSHR, CYP19A1, and CTNNB1 genes in porcine ovarian follicles after prenatal and neonatal flutamide exposure

Recent studies suggest that disturbed androgen action during gestational and neonatal periods leads to reprogramming of the trajectory of ovarian development, manifested by altered follicular functioning in adulthood. In this study, we tested whether prenatal and neonatal exposure to antiandrogen flutamide affected ovarian 17β-estradiol (E(2)) synthesis and the associated gene expression in large antral follicles of adult pigs. Flutamide was injected into pregnant gilts between Days 80 and 88 of gestation and into female piglets between Days 2 and 10 postnatally. After animals reached sexual maturity, the ovaries were collected from treated and nontreated (control) pigs. The analysis of E(2) concentration in follicular tissues, as well as FSH and LH levels in plasma of control and flutamide-treated animals were conducted. In addition, the expression of mRNAs and proteins for FSH receptor (FSHR), cytochrome P450 aromatase (CYP19A1) and β-catenin (CTNNB1) was examined in large antral follicles of adult pigs. The E(2) concentration was greater in response to flutamide administered prenatally (P < 0.05) and neonatally (P < 0.01), whereas there was no changes in plasma gonadotropin concentration. Real-time polymerase chain reaction analysis revealed significant upregulation of FSHR, CYP19A1, and CTNNB1 at the mRNA level after maternal (P < 0.001, P < 0.01, P < 0.05, respectively) and neonatal (P < 0.001, P < 0.001, P < 0.01, respectively) flutamide exposure. The expression of FSHR protein was higher (P < 0.01) only after neonatal exposure to flutamide, whereas CYP19A1 and CTNNB1 proteins were upregulated in response to both prenatal (P < 0.01) and neonatal (P < 0.001) flutamide administration. Furthermore, membranous CTNNB1 immunolocalization indicates that it is not involved in regulation of FSH-mediated CYP19A1 activity as a transcription factor, but rather contributes to the intercellular adhesion. Concluding, it appears that the higher E(2) level in response to flutamide treatments is a result of the intensified aromatization and local E(2) action at the ovary level. The observed changes might influence the normal follicle development and pig fertility as a consequence.

Effects of fibroblast growth factor 9 (FGF9) on steroidogenesis and gene expression and control of FGF9 mRNA in bovine granulosa cells

Gene expression of fibroblast growth factor-9 (FGF9) is decreased in granulosa cells (GC) of cystic follicles compared with normal dominant follicles in cattle. The objectives of this study were to investigate the effects of FGF9 on GC steroidogenesis, gene expression, and cell proliferation and to determine the hormonal control of GC FGF9 production. GC were collected from small (1-5 mm) and large (8-22 mm) bovine follicles and treated in vitro with various hormones in serum-free medium for 24 or 48 h. In small- and large-follicle GC, FGF9 inhibited (P < 0.05) IGF-I-, dibutyryl cAMP-, and forskolin-induced progesterone and estradiol production. In contrast, FGF9 increased (P < 0.05) GC numbers induced by IGF-I and 10% fetal calf serum. FGF9 inhibited (P < 0.05) FSHR and CYP11A1 mRNA abundance in small- and large-follicle GC but had no effect (P > 0.10) on CYP19A1 or StAR mRNA. In the presence of a 3β-hydroxysteroid dehydrogenase inhibitor, trilostane, FGF9 also decreased (P < 0.05) pregnenolone production. IGF-I inhibited (P < 0.05) whereas estradiol and FSH had no effect (P > 0.10) on FGF9 mRNA abundance. TNFα and wingless-type mouse mammary tumor virus integration site family member-3A decreased (P < 0.05) whereas T(4) and sonic hedgehog increased (P < 0.05) FGF9 mRNA abundance in control and IGF-I-treated GC. Thus, GC FGF9 gene expression is hormonally regulated, and FGF9 may act as an autocrine regulator of ovarian function by slowing follicular differentiation via inhibiting IGF-I action, gonadotropin receptors, the cAMP signaling cascade, and steroid synthesis while stimulating GC proliferation in cattle.

FGF10 inhibits dominant follicle growth and estradiol secretion in vivo in cattle

Fibroblast growth factors (FGFs) are involved in paracrine control of follicle development. It was previously demonstrated that FGF10 decreases estradiol (E2) secretion in granulosa cell culture and that theca cell FGF10 mRNA expression is decreased in healthy follicles from abattoir ovaries. The main objectives of this study were to evaluate FGF10 and FGFR2b mRNA expression during follicular development in vivo, to evaluate the effect of FGF10 on follicle growth using Bos taurus taurus cows as a model, and to gain more insight into the mechanisms through which FGF10 inhibits steroidogenesis. Messenger RNA encoding both FGF10 and FGFR2b (main FGF10 receptor) was significantly more expressed in subordinate follicles (SFs) than in dominant follicles (DFs). The intrafollicular injection of FGF10 into the largest growing follicle at 7–8 mm in diameter interrupted the DF growth in a dose-dependent manner (11±0.4, 8.3±1 and 5.9±0.3 mm for 0, 0.1, and 1 μg/ml FGF10, respectively, at 72 h after treatment; P<0.05). In a third experiment, follicles were obtained 24 h after FGF10 (1 μg/ml) or PBS treatment through ovariectomy. In theca cells, FGF10 treatment did not affect mRNA encoding steroidogenic enzymes, LHCGR and IGFBPs, but significantly upregulated FGF10 mRNA expression. The expression of CYP19A1 mRNA in granulosa cells was downregulated by FGF10 treatment, which was accompanied by a 50-fold decrease in E2 production, and decreased cyclin D2 mRNA. These results have shown that FGF10 and its receptor FGFR2b are more expressed in SFs and provide solid in vivo evidence that FGF10 acts as an important regulator of follicular growth in cattle.

Differential regulation of gonadotropin receptors by bone morphogenetic proteins in the zebrafish ovary

Follicle-stimulating hormone receptor (fshr) and luteinizing hormone/choriogonadotropin receptor (lhcgr) exhibit differential temporal expression patterns during zebrafish folliculogenesis with fshr being dominant during vitellogenic growth and lhcgr increasing its expression dramatically before maturation. The dynamic and distinct expression patterns of fshr and lhcgr suggest that they are under tight regulatory control. However, the underlying mechanisms for the differential expression of the two receptors remain unknown. We have recently demonstrated that members of bone morphogenetic protein (BMP) family are largely expressed in the oocyte, while their receptors are exclusively localized on the follicle cells, suggesting a potential paracrine signaling from the oocyte to the follicle cells by BMPs. In this study, we investigated the effects of zebrafish BMP2b (zfBmp2b) and BMP4 (zfBmp4) on the expression of fshr and lhcgr using a novel co-culture approach. The recombinant zfBmp2b or zfBmp4-producing CHO cells were co-cultured with the zebrafish follicle cells followed by real-time qPCR analysis of fshr and lhcgr expression. Our results showed that zfBmp2b and zfBmp4 both down-regulated fshr, while up-regulated lhcgr expression at 24 h of co-culturing. This finding, together with the high expression level of BMP receptors in the follicle cells prior to oocyte maturation, strongly suggests a potential role for BMPs in the differential expression of fshr and lhcgr, especially in the full-grown follicles before maturation. As BMPs are largely expressed in the oocyte, this also implies an important role for the oocyte in orchestrating the differentiation and function of the follicle cells.

Androgen-specific regulation of FSH signalling in the previtellogenic ovary and pituitary of the New Zealand shortfinned eel, Anguilla australis

The evidence for androgens having a pivotal role in the functioning of the female reproductive axis--such as initiating puberty or vitellogenesis--is mounting. However, the use of aromatizable androgens and the tissue-specific focus of most studies often make it unclear if androgenic effects throughout the axis proceed via androgen or estrogen signalling mechanisms. In this study, we assessed the effects of 11-ketotestosterone (11KT, a non-aromatizable androgen) on the pituitary and ovary of previtellogenic (PV) freshwater eels Anguilla australis, comparing them with eels naturally undergoing early vitellogenesis (EV). We found that 11KT treatment produces molecular and morpho-physiological phenotypes that were generally intermediate between PV and EV. Most notably, we demonstrated that 11KT induces effects on follicle-stimulating hormone (FSH) signalling in the pituitary and ovaries that are in opposition to each other. Thus, 11KT significantly reduced fshβ subunit expression in the pituitary. At the same time, 11KT dramatically increased mRNA levels of ovarian FSH receptor and plasma levels of estradiol-17β, very likely sensitizing the previtellogenic follicle to the FSH signal. Androgens therefore may be important in facilitating puberty in the eel.

Aromatase (CYP19) gene variants influence ovarian response to standard gonadotrophin stimulation

PURPOSE

The association of cytochrome P450 aromatase gene CYP19(TTTA) ( n ) polymorphism with ovarian response to FSH stimulation was explored.

METHODS

Three hundred women undergoing medically assisted reproduction and 300 women with at least one spontaneous pregnancy participated in the study. CYP19(TTTA) ( n ) polymorphism was genotyped, while serum hormones were determined. During oocyte retrieval, the follicular size, the follicle and oocyte numbers were recorded.

RESULTS

Six CYP19(TTTA) ( n ) alleles with 7 to 12 repeats were revealed. Women homozygous for long CYP19(TTTA) ( n ) alleles presented with lower serum FSH levels at the third day of the menstrual cycle (p < 0.001) and higher large follicle numbers (p < 0.01), compared to women homozygous for short CYP19(TTTA) ( n ) alleles. The CYP19(TTTA) ( 7 ) allele was associated with higher serum FSH levels (p < 0.003), with lower total follicle (p < 0.02) and large follicle numbers (p < 0.03), while CYP19(TTTA) ( 7 ) allele-carriers presented more frequently with small follicles than CYP19(TTTA) ( 7 ) allele-non carriers (p < 0.01).

CONCLUSIONS

CYP19 genetic variants were associated with ovarian reserve and response to standard gonadotrophin stimulation of women undergoing in vitro fertilization.

Differential regulation of gonadotropin receptors (fshr and lhcgr) by estradiol in the zebrafish ovary involves nuclear estrogen receptors that are likely located on the plasma membrane

FSH and LH are gonadotropins (GTH) that control all major events of gonadal function. FSH and LH signal through their cognate receptors, FSH receptor and LH/choriogonadotropin receptor, respectively, across vertebrates. Compared with the information in mammals, very little is known about these receptors in fish, especially the regulation of their expression. In female zebrafish, fshr and lhcgr exhibit significant temporal difference in expression, with fshr increasing first when the follicles are activated to enter the vitellogenic growth phase and lhcgr lagging behind. This raises an interesting question on the differential regulation of these two GTH receptors (GTHR) during folliculogenesis. Using a primary follicle cell culture, the present study demonstrated that 17β-estradiol (E2), but not testosterone, was a potent endocrine hormone that differentially regulated the expression of fshr and lhcgr. Although E2 stimulated both receptors, its effect on the steady-state level of lhcgr mRNA was much higher (>8-fold up-regulation) than that of fshr (∼0.5-fold increase). E2 likely acted at the transcription level via its nuclear estrogen receptors (ERα and ERβ), because ICI 182,780 could abolish its effects. However, our evidence suggested that these receptors might be localized on the plasma membrane, because β-estradiol 6-(O-carboxy methyl)oxime:BSA could fully mimic the effects of E2. Demonstrating that E2 is likely one of the differentiating factors for the distinct expression of the two GTHR in the zebrafish ovary, this study sheds important light on the functions of the two GTH and their receptors in fish as well as the conservation and diverse aspects of GTHR regulation across vertebrates.

Induction of mRNA for chemokines and chemokine receptors by prostaglandin F2α is dependent upon stage of the porcine corpus luteum and intraluteal progesterone

This study tested the hypotheses that prostaglandin (PG) F(2α) increases expression of genes related to recruitment of leukocytes in mature but not early corpus luteum (CL) and that insensitivity to PGF(2α) action in early CL is dependent on high intraluteal progesterone (P4) concentrations. Experiment 1 examined early (0.5 h) and late (10 h) in vivo effects of PGF(2α) on mature (d 17 of pseudopregnancy) and early (d 9) porcine CL. Real-time PCR was used to measure mRNA for chemokines (IL8, CXCL2, CCL2, CCL8, CCL4, CCL11) and chemokine receptors (CCR1, CCR2, CXCR2, CCR5). Western blotting was used to measure protein expression and phosphorylation of nuclear factor-κB proteins. Treatment with PGF(2α) for 10 h increased mRNA for almost all of these genes (all expect CXCL2 and CCL11) in d 17 CL but not d 9 CL. Treatment with PGF(2α) also led to greater phosphorylation of nuclear factor-κB-1A protein in d 17 than d 9 CL. Experiment 2 had a 2 × 2 factorial design with d 9 gilts treated or not treated with epostane (3β-hydroxysteroid dehydrogenase inhibitor to suppress intraluteal P4) and treated or not treated with PGF(2α). Treatment with PGF(2α) (10 h) or epostane alone did not induce expression of any of these genes in d 9 CL. However, PGF(2α) + epostane increased expression of all of these genes except CCL11. In conclusion, PGF(2α) increases mRNA for chemokines and chemokine receptors in mature CL with similar PGF(2α) effects induced in early CL if intraluteal P4 is suppressed prior to PGF(2α) treatment.

Angiotensin II profile and mRNA encoding RAS proteins during bovine follicular wave

Angiotensin II (AngII) has a role in ovarian follicle development, ovulation, and oocyte meiotic resumption. The objective of the present study was to characterise the AngII profile and the mRNA encoding RAS proteins in a bovine follicular wave. Cows were ovariectomised when the size between the largest (F1) and the second largest follicle (F2) was not statistically different (day 2), slightly different (day 3), or markedly different (day 4). AngII was measured in the follicular fluid and the mRNA abundance of genes encoding angiotensin-converting enzyme (ACE), (pro)renin receptor, and renin-binding protein (RnBP) was evaluated in the follicular cells from F1 and F2. The AngII levels increased at the expected time of the follicular deviation in F1 but did not change in F2. However, the expression of the genes encoding ACE, (pro)renin receptor, and RnBP was not regulated in F1 but was upregulated during or after the follicular deviation in F2. Moreover, RnBP gene expression increased when the F1 was treated with the oestrogen receptor-antagonist in vivo. In conclusion, the AngII concentration increased in the follicular fluid of the dominant follicle during and after deviation and further supports our finding that RAS is present in the ovary regulating follicular dominance.

Testosterone, not 5α-dihydrotestosterone, stimulates LRH-1 leading to FSH-independent expression of Cyp19 and P450scc in granulosa cells

Androgens are crucial for normal folliculogenesis and female fertility as evidenced in androgen receptor-null and granulosa cell conditional knockout mice. It is thought, however, that the multiple effects of androgens in the ovary are mainly complementary to the actions of gonadotropins. Using primary rat granulosa cells, we demonstrated that in the absence of gonadotropins, testosterone (T) increases aromatase (Cyp19) and P450 side-change cleavage expression, two enzymes crucial for normal ovarian function. T can be converted into estradiol, a classical estrogen, by Cyp19 and into 5α-dihydrotestosterone, a pure androgen, by 5α-reductase. However, inhibition of Cyp19 and/or 5α-reductase did not prevent the stimulatory effects of T. In contrast, the effect of this steroid was potentiated by blocking 5α-reductase. Additionally, T, not 5α-dihydrotestosterone, stimulates liver receptor homolog-1 (LRH-1) expression, whereas the expression of steroidogenic factor-1 (SF-1) was not affected by either steroid. LRH-1 and SF-1 are transcription factors known to be involved in the regulation of Cyp19. Accordingly, small interference RNA against LRH-1 prevented Cyp19 and P450 side-change cleavage up-regulation whereas anti-SF-1 small interference RNA had no effects. Chromatin immunoprecipitation demonstrated that T stimulation of LRH-1 leads to the recruitment of LRH-1 to the native Cyp19 promoter, which was not affected by cotreatment with 5α-reductase and Cyp19 inhibitors. Finally, gel shift and supershift analysis demonstrated that the androgen receptor binds to an androgen response element located within the LRH-1 promoter. These results provide novel evidence that T has a direct effect on the expression of genes involved in granulosa cell differentiation.

Follicular somatic cell factors and follicle development

Considerable attention is currently paid to oocyte-derived secreted factors that act upon cumulus and granulosa cells. Also important for follicle development are somatic cell-derived secreted factors. This is illustrated by the ability of granulosa cell-derived Kit ligand (KITL) to promote primordial follicle activation, and the loss of follicle development that accompanies KITL gene disruption. This review summarises our current understanding of somatic cell factors during both preantral and antral follicle growth, involving not only signalling from granulosa cells to the oocyte, but also signalling between granulosa and theca cells. Principal granulosa cell-derived factors include activin, anti-Müllerian hormone (AMH), bone morphogenetic proteins (BMPs) and fibroblast growth factors (FGFs). Theca cells also secrete BMPs and FGFs. The interplay between these factors is equally important for follicle growth as the activity of oocyte-derived factors.

Effect of decreasing intraluteal progesterone on sensitivity of the early porcine corpus luteum to the luteolytic actions of prostaglandin F2alpha

Prostaglandin F2alpha (PGF) causes luteolysis of the pig corpus luteum (CL) only after Day 12 of the estrous cycle. Recent evidence indicates that progesterone (P4) may protect the CL from cell death. The present study tested the hypothesis that acute inhibition of P4 by treatment with epostane (EPO; 3betaHSD inhibitor) in CL lacking luteolytic capacity (Day 9 CL) will allow PGF to induce responses associated with luteolysis. Multiple PGF-induced responses were evaluated, including genes involved in production of PGF and estradiol-17beta, apoptosis (caspase 3), and transcription (FOSB). These responses are associated with PGF-induced luteolysis and do not normally occur in CL lacking luteolytic capacity. Animals on Day 7 after estrus were divided into four groups: 1) control (C), 2) PGF, 3) EPO, and 4) PGF plus EPO (PGF+EPO). Treatment with EPO (10 mg/kg) or vehicle was given every 12 h for 36 h. Treatment with PGF (25 mg) or vehicle was given at 38 h, and CL were collected from all animals at 48 h. Some CL from each animal were frozen in liquid nitrogen for mRNA and protein analysis. Remaining CL were incubated in media for 2 h for determination of P4 and PGF production. EPO dramatically decreased production of P4 by luteal tissue (ng/mg tissue) by 90% and 95% in EPO and PGF+EPO groups, respectively, compared to C (P < 0.01). Low production of PGF by luteal tissue was found in C, PGF, and EPO groups; however, treatment with PGF+EPO dramatically increased (782%) luteal PGF production. Similar to intraluteal PGF production, increased mRNA for cyclooxygenase 2 (PTGS2) and phospholipase A2 (group IB; PLA2G1B) was found in the PGF+EPO, but not in the EPO or PGF, group. Aromatase (CYP19A1) mRNA was not induced by PGF or EPO; however, PGF+EPO caused a more than 40-fold increase in CYP19A1 mRNA (P < 0.01). CASP3 mRNA was increased (P < 0.01) by EPO (3.4-fold) and by PGF (2.7-fold) but was most dramatically increased by PGF+EPO (5.3-fold), whereas caspase activity was only increased by PGF (1.5-fold) or PGF+EPO (2.2-fold). Thus, these data support the hypothesis that elimination of the protective effect of intraluteal P4 does not directly cause luteolysis of the early CL but allows PGF to induce luteolytic responses in CL lacking luteolytic capacity.

Expression and function of fibroblast growth factor 18 in the ovarian follicle in cattle

Fibroblast growth factors (FGF) are involved in paracrine signaling between cell types in the ovarian follicle. FGF8, for example, is secreted by oocytes and controls cumulus cell metabolism. The closely related FGF18 is also expressed in oocytes in mice. The objective of this study was to assess the potential role of FGF18 in follicle growth in a monovulatory species, the cow. Messenger RNA encoding FGF18 was detected primarily in theca cells, and in contrast to the mouse, FGF18 was not detected in bovine oocytes. Addition of FGF18 protein to granulosa cell cultures inhibited estradiol and progesterone secretion as well as the abundance of mRNA encoding steroidogenic enzymes and the follicle-stimulating hormone receptor. In vivo, onset of atresia of the subordinate follicle was associated with increased thecal FGF18 mRNA levels and FGF18 protein in follicular fluid. In vitro, FGF18 altered cell cycle progression as measured by flow cytometry, resulting in increased numbers of dead cells (sub-G1 peak) and decreased cells in S phase. This was accompanied by decreased levels of mRNA encoding the cell cycle checkpoint regulator GADD45B. Collectively, these data point to a unique role for this FGF in signaling from theca cells to granulosa cells and suggest that FGF18 influences the process of atresia in ovarian follicles.

LH/hCGR gene expression in human cumulus cells is linked to the expression of the extracellular matrix modifying gene TNFAIP6 and to serum estradiol levels on day of hCG administration

BACKGROUND

Recent studies suggest a role for luteinizing hormone and human chorionic gonadotrophin receptor (LH/hCGR) signalling in the regulation of the oocyte-cumulus oophorus cell interplay. The present study aimed at assessing the LH/hCGR gene expression in cumulus cells (CCs) surrounding oocytes in patients undergoing controlled ovarian hyperstimulation (COS) before ICSI and to relate the LH/hCGR expression to other COS quality parameters.

METHODS

CCs from single oocytes of normal responder patients were analysed by DNA microarrays. Concomitantly, estradiol levels on the day of hCG administration, CC morphology, total collected oocyte and metaphase II oocyte number were assessed in relation to LH/hCGR gene expression in CC.

RESULTS

The transcriptome analysis of CC indicated a variable expression of LH/hCGR among the patients and intra-patients. LH/hCGR mRNA expression was negatively correlated with serum estradiol level on the day of hCG administration. Eighty-five genes were significantly modulated between CCs from patients with a high and a low LH/hCGR expression. These genes are involved principally in steroid metabolism and in the ovulation process and include TNFAIP6, a gene expressed during CC-oocyte complex (COC) expansion. There were no significant differences in LH/hCGR gene expression profile between COS protocols.

CONCLUSIONS

LH/hCGR is expressed in CC under COS conditions. LH/hCGR expression level is associated with TNFAIP6 gene expression and negatively correlated with serum estradiol level on the day of hCG administration.

Aromatase gene and its effects on growth, reproductive and maternal ability traits in a multibreed sheep population from Brazil

We determined the polymorphism C242T of the aromatase gene (Cyp19) and its allelic frequency, as well as the effect of the variants on productive and reproductive traits in 71 purebred Santa Inês sheep, 13 purebred Brazilian Somali sheep, nine purebred Poll Dorset sheep, and 18 crossbred 1/2 Dorper sheep. The animals were genotyped using the PCR-RFLP technique. The influence of the animal's genotype on its performance or on the performance of its lambs was analyzed by the least square method. Another factor assessed was the importance of the animal's genotype in analysis models for quantitative breeding value estimates, and whether there were differences among the averages of breeding values of animals with different genotypes for this gene. In the sample studied, no AA individuals were observed; the AB and BB frequencies were 0.64 and 0.36, respectively. All Brazilian Somali sheep were of genotype BB. All 1/2 Dorper BB animals presented a lower age at first lambing, and the Santa Inês BB ewes presented a lower lambing interval. In these same genetic groups, AB ewes presented higher litter weight at weaning. This is evidence that BB ewes have a better reproductive performance phenotype, whereas AB ewes present a better maternal ability phenotype. However, in general, animals with genotype AB presented better average breeding values than those with genotype BB.

Applications of estradiol and testosterone assays in the management of the infertile female patient

A collaborative effort to improve steroid hormone measurements in patient care was convened by the Centers for Disease Control in March 2008 to discuss the need for enhanced performance and standardization of clinical estradiol and testosterone assays. This article discusses the current status of estradiol and testosterone assays in the treatment of infertile women to include the assessment of ovarian reserve, ovulation induction and follicle tracking, ovarian hyperstimulation syndrome, and the role of testosterone in fertility management.

Functional AR signaling is evident in an in vitro mouse follicle culture bioassay that encompasses most stages of folliculogenesis

Androgens have distinct physiological functions within the ovary. The biological action of androgens is primarily exerted through transcriptional regulation by the nuclear androgen receptor (AR), but the molecular cascades governed by AR remain largely unknown. At present, there is imminent concern that environmental man-made chemicals with antiandrogenic properties, among others, are capable of modulating hormonal responses, thereby interfering with normal physiological processes that are critical to fertility. In the present study, we aimed to further characterize a standardized and reproducible follicle culture system in terms of AR expression during in vitro folliculogenesis to be able to use it as a bioassay to study effects of antiandrogens on follicular and oocyte growth, steroid secretion profile, and oocyte meiotic maturation capacity. Immunohistochemical analysis revealed that cytoplasmic AR protein was translocated to the nucleus of granulosa and theca cells in response to endogenous androgen production in theca cells during preantral follicular development. During the antral phase in vitro, AR was differentially expressed in mural and cumulus cells, implying an oocyte-mediated regulation. Treatment of follicles with hydroxyflutamide or bicalutamide, two model antiandrogenic compounds, resulted in reduced follicular growth during the preantral phase, altered steroidogenic environment, and arrest in oocyte meiotic maturation in response to human chorionic gonadotropin. Androgen receptor expression in the culture model corresponded well to what is described in vivo, and this system revealed several ovarian functions targeted by AR antagonists that can be further investigated using more in-depth molecular techniques.

Polycystic ovarian syndrome: pathophysiology, molecular aspects and clinical implications

Polycystic ovarian syndrome (PCOS) is universally recognised as the commonest endocrinopathy of women. The definition and the aetiological hypotheses of PCOS are continuously evolving to accommodate expanding knowledge on the syndrome, which is now known to be more complex than purely a reproductive disorder. Increased androgen synthesis, disrupted folliculogenesis and insulin resistance lie at the pathophysiological core of PCOS. An intriguing concept involves the perpetuation of a vicious circle with endocrine/reproductive and metabolic components. An unfavourable metabolic environment may unmask genetic traits of ovarian dysfunction, and the unfolding endocrine derangement could further aggravate the metabolic disarray. This article reviews the molecular mechanisms known to underlie the ovarian and metabolic abnormalities characterising PCOS. The putative interdependence between reproductive and metabolic aspects of PCOS, and therapeutic implications for the management of PCOS, are also discussed.

Differential actions of FSH and LH during folliculogenesis

In the gonadotrophin-dependent stage of follicular development, FSH- and LH-signalling pathways play an obligatory role in follicle differentiation, selection and survival. Under the effect of LH the theca-interstitial cell layer acts as an androgen producer. Thus, androgen diffusing into the mural granulosa cell layer represents the substrate for FSH-induced aromatase for follicular oestradiol synthesis. This is the landmark 'two cell-two gonadotrophin' concept in the physiology of ovarian function in mammals. The increase in plasma FSH during luteo-follicular transition is the basis for follicle selection. The rise of FSH to the threshold concentration represents a critical condition for the growth of the most sensitive follicle in a given time frame of the last 14 days of the dominant follicle odyssey. The gonadotrophin-induced follicular oestradiol secretion inhibits pituitary secretion of FSH, which in turn causes the concentration of FSH in the developing cohort follicles to drop below threshold concentrations and the arrest of the development of the less FSH-sensitive follicle (FSH threshold and window concept). In the gonadotrophin-dependent phase of follicular development, LH also seems to acts within a critical window of the hormone concentration framed between the minimal threshold and a ceiling for the normal functions of the follicle unit.

Development of primordial follicles in the hamster: role of estradiol-17beta

The role of E2 on primordial follicle formation was examined by treating neonatal hamsters with 1 or 2 microg estradiol cypionate (ECP) at age postnatal d 1 (P1) and P4 or by in vitro culture of embryonic d 15 (E15) ovaries with 1, 5, or 10 ng/ml estradiol-17beta (E2). The specificity of E2 action was examined by ICI 182,780. One microgram of ECP maintained serum levels of E2 within the physiological range, significantly reduced apoptosis, and stimulated the formation and development of primordial follicles. In contrast, 2 microg ECP increased serum E2 levels to 400 pg/ml and had significantly less influence on primordial follicle formation. In vivo, ICI 182,780 significantly increased apoptosis and caused a modest reduction in primordial follicle formation. The formation and development of primordial follicles in vitro increased markedly with 1 ng/ml E2, and the effect was blocked by ICI 182,780. Higher doses of E2 had no effect on primordial follicle formation but significantly up-regulated apoptosis, which was blocked by ICI 182,780. CYP19A1 mRNA expression occurred by E13 and increased with the formation of primordial follicles. P4 ovaries synthesized E2 from testosterone, which increased further by FSH. Both testosterone and FSH maintained ovarian CYP19A1 mRNA, but FSH up-regulated the expression. These results suggest that neonatal hamster ovaries produce E2 under FSH control and that E2 action is essential for the survival and differentiation of somatic cells and the oocytes leading to the formation and development of primordial follicles. This supportive action of E2 is lost when hormone levels increase above a threshold.