Mitogenic and antioxidant mechanisms of estradiol action in preovulatory ovine follicles: relevance to luteal function

Local effect of allopregnanolone in rat ovarian steroidogenesis, follicular and corpora lutea development

Allopregnanolone (ALLO) is a known neurosteroid and a progesterone metabolite synthesized in the ovary, CNS, PNS, adrenals and placenta. Its role in the neuroendocrine control of ovarian physiology has been studied, but its in situ ovarian effects are still largely unknown. The aims of this work were to characterize the effects of intrabursal ALLO administration on different ovarian parameters, and the probable mechanism of action. ALLO administration increased serum progesterone concentration and ovarian 3β-HSD2 while decreasing 20α-HSD mRNA expression. ALLO increased the number of atretic follicles and the number of positive TUNEL granulosa and theca cells, while decreasing positive PCNA immunostaining. On the other hand, there was an increase in corpora lutea diameter and PCNA immunostaining, whereas the count of TUNEL-positive luteal cells decreased. Ovarian angiogenesis and the immunohistochemical expression of GABAA receptor increased after ALLO treatment. To evaluate if the ovarian GABAA receptor was involved in these effects, we conducted a functional experiment with a specific antagonist, bicuculline. The administration of bicuculline restored the number of atretic follicles and the diameter of corpora lutea to normal values. These results show the actions of ALLO on the ovarian physiology of the female rat during the follicular phase, some of them through the GABAA receptor. Intrabursal ALLO administration alters several processes of the ovarian morpho-physiology of the female rat, related to fertility and oocyte quality.

Biochemical profiling of the follicular environment to predict oocyte competence in cattle

To identify markers of oocyte competence, we compared the biochemical characteristics of fluid and cells from follicles containing oocytes with different capacities to form an embryo. Follicles (5-6 mm) were dissected, and follicular fluid (FF), granulosa cells (GC), cumulus cells (CC) from immature and mature cumulus-oocyte-complexes (COC) were individually collected. The oocytes were matured, fertilized, and cultured individually until day 8 (D8) of development. On D8, the samples were grouped according to embryo production into those that gave rise to blastocysts (EMB) and those that did not reach the blastocyst stage (NEMB). In CCs from immature and mature COCs and GCs, expression of CASP3, SERPINE2, VCAN, LUM, FSHR, EGFR, PGR, and GHR genes was quantified. Cell-free DNA (cfDNA), progesterone, and estradiol concentrations in the FF were determined. Data were analyzed by Mann-Whitney U test (GraphPad Prism 9). GHR was highly expressed in immature CCs from the EMB group, whereas CASP3 was highly expressed in mature CCs from the NEMB group (P<0.05). During maturation, the expression of CASP3 and GHR genes increased only in the NEMB group. ART2 cfDNA was highly detected in FF of the NEMB compared to the EMB group. Progesterone concentration was similar between the groups, whereas estradiol concentration was higher (P<0.05) in the EMB than in the NEMB group. It was concluded that a higher level of GHR transcripts in immature CCs, lower CASP3 expression in CCs from matured COCs, lower levels of ART2, and higher estradiol concentrations in FF may indicate oocytes with greater potential for development.

The Effect of Maternal Exposure to a Diet High in Fats and Cholesterol on the Placental Function and Phenotype of the Offspring in a Rabbit Model: A Summary Review of About 15 Years of Research

The rates of obesity and being overweight are increasing all around the world, especially among women of childbearing age, in part due to overconsumption of lipids. The aim of this summary review was to present the cellular and molecular effects of a hyperlipidic high-cholesterol (H) diet on the maternal and offspring phenotype at the early embryonic, neonatal, weaning and adult stages while considering the effects of sex and to identify the window(s) of vulnerability linked to this exposure in a rabbit model. Before breeding, the H diet induced dyslipidemia and aortic atherosclerosis lesions and increased the number of atretic follicles. In the offspring, the H diet disrupted the embryonic phenotype and induced fetal hypotrophy associated with sex-specific disturbances of the feto-placental unit. In adulthood, the offspring of the H dams were heavier and hyperphagic and had increased blood pressure associated with disturbed gonadal development in both sexes. Vulnerability windows were explored via embryo transfers. The maternal gestational diet was shown to play a key role in the feto-placental phenotype, and preconception programming was unquestionably also observed. These two periods could represent windows of intervention in the context of obesity or being overweight to limit fetal and placental consequences.

The Effect of Alternating High-Sucrose and Sucrose Free-Diets, and Intermittent One-Day Fasting on the Estrous Cycle and Sex Hormones in Female Rats

Relationships between diet, sex hormone concentrations, and the estrous cycle are important from the perspective of infertility and estrogen-dependent disease prevention and treatment. Four dietary interventions reflecting modern eating behaviors were explored. The study involved 50 female rats divided into five feeding groups. The impact of the amount of sucrose consumed (9% and 18% of the dietary energy content), alternating high-sucrose and sucrose-free diets, and a high-sucrose diet combined with intermittent one-day fasting on the estrous cycle and sex hormone concentrations in female rats was assessed. Even low amounts of dietary sucrose (9% of the dietary energy content) were found to lead to increased estradiol (E2) concentrations and decreased progesterone (Pg) concentrations. A high-sucrose diet, even when periodically applied, additionally led to a reduced concentration of luteinizing hormone (LH). The largest changes in the hormones tested were observed with one-day fasting coupled with the high-sucrose diet; in addition, the estrous phase was shortened and the estrous cycle was disrupted. The results of this study show that both the amount of dietary sucrose and also its uptake pattern affect the estrous cycle and sex hormone concentrations in female rats.

Ambient ozone exposure combined with residential greenness in relation to serum sex hormone levels in Chinese rural adults

BACKGROUND

Long-term exposure to ambient ozone (O₃) and residential greenness independently relate to altered hormones levels in urban settings and developed countries. However, independent and their joint associations with progestogen and androgen were sparsely studied in rural regions.

MATERIALS AND METHODS

A total of 6211 individuals were recruited in this study. Random forest model was applied to predict the daily average concentrations of O₃ using the satellites data. Residential greenness was reflected by the normalized difference vegetation index (NDVI). Liquid chromatography-tandem mass spectrometry was used to measure serum progestogen and androgen concentrations. Gender and menopausal status modified associations of long-term exposure to O₃ and residential greenness with hormones levels were analyzed by generalized linear models.

RESULTS

Long-term exposure to O₃ was negatively related to 17-hydroxyprogesterone, testosterone, and androstenedione in both men and women (premenopausal and postmenopausal); the estimated β and 95% CI of ln-progesterone in response to per 10 μg/m³ increment in O₃ concentration was -0.560 (-0.965, -0.155) in postmenopausal women. Association of long-term exposure to O₃ with serum androgen levels in premenopausal and postmenopausal women were alleviated by residing in places with higher greenness. Additionally, a prominent effect of long-term exposure to O₃ related to decreased serum progestogen and androgen levels was found in participants with middle- or high-level of physical activity or lower education level.

CONCLUSIONS

The results suggested that long-term exposure to high levels of O₃ related to decreased serum androgen levels was attenuated by living in high greenness places in women regardless of menopause status. Future studies are needed to confirm the positive health effects of residential greenness on the potential detrimental effects due to exposure to O₃.

Transcriptome Analysis of Porcine Granulosa Cells in Healthy and Atretic Follicles: Role of Steroidogenesis and Oxidative Stress

One of the main causes of female infertility is a deregulated antral follicular atresia, a process of which the underlying molecular mechanisms are largely unknown. Our objective was therefore to characterize the complex transcriptome changes in porcine granulosa cells of healthy antral (HA) and advanced antral atretic (AA) follicles, using ELISA and RNA-Seq followed by qRT-PCR and immunohistochemistry. Granulosa cell RNA-Seq data revealed 2160 differentially expressed genes, 1483 with higher and 677 with lower mRNA concentrations in AA follicles. Bioinformatic analysis showed that the upregulated genes in AA follicles were highly enriched in inflammation and apoptosis processes, while the downregulated transcripts were mainly highlighted in the steroid biosynthesis pathway and response to oxidative stress processes including antioxidant genes (e.g., GSTA1, GCLC, GCLM, IDH1, GPX8) involved in the glutathione metabolism pathway and other redox-related genes (e.g., RRM2B, NDUFS4). These observations were confirmed by RT-qPCR and immunohistochemistry. Additionally, the granulosa cells of AA follicles express significantly stronger 8-OHdG immunostaining, a marker of oxidative DNA damage, implicating that oxidative stress may participate in follicular atresia. We hypothesize that the decrease in anti-apoptotic factors and steroid hormones coincides with increased oxidative stress markers and the expression of pro-apoptotic factors, all contributing to antral follicular atresia.

N1-Methylnicotinamide: An Anti-Ovarian Aging Hormetin?

Ovarian aging occurs due to the reduction of the quality and quantity of the oocytes, and is regulated by mitochondrial survival and apoptotic signals. Reactive Oxygen Species (ROS) are one of those signals considered detrimental to cellular homeostasis. Nowadays, ROS are regarded as a regulatory factor at low levels as it induces the stress resistance which in turn increases the longevity. It is believed that the main mechanism for the life-promoting role of the ROS mediated by the 5' Adenosine Monophosphate-activated Protein Kinase (AMPK). N1-Methylnicotinamide (MNAM) is well known for its anti-diabetic, anti-thrombotic, and anti-inflammatory activity. Aldehyde oxidase 1 (AOX1) is a detoxifying enzyme, which metabolizes the MNAM and produces two metabolites including N1-methyl-2-pyridone-5- carboxamide (2py) and N1-methyl-4-pyridone-3-carboxamide (4py). The activity of AOX1 enhances the production of ROS and improves the longevity. It has been reported that the MNAM could postpone the aging through the induction of low-level stress. It has been documented that the production of MNAM is significantly higher in the cumulus cells of the patients with Polycystic Ovary Syndrome (PCOS) and its administration on the rat model of PCOS has been shown to alleviate the hyperandrogenism and successfully activate the ovarian AMPK. Therefore, it can be hypothesized that the anti-ovarian aging effects of the MNAM are possibly based on the activation of AMPK through transient elevation of the ROS.

Estradiol and Progesterone Levels are Related to Redox Status in the Follicular Fluid During in vitro Fertilization

Studies have reported a possible association between the levels of oxidative stress biomarkers in follicular fluid (FF) and infertility treatment outcomes. FF analysis can provide important information about oocyte quality. This study aimed to evaluate the possible correlation between oxidative stress biomarker and intrafollicular hormone levels and clinical and laboratory parameters in women during controlled ovarian stimulation. These women were undergoing in vitro fertilization with intracytoplasmic sperm injection (ICSI).The FF samples were acquired from September 2012 to February 2014 from women undergoing private fertility treatment in Rio de Janeiro, Brazil. A total of 196 women who were undergoing ICSI and had different infertility diagnoses were recruited. The FF from each patient (average patient age of 36.3 ± 4.3 years) was collected following puncture of just one follicle with the largest diameter. After ruling out blood contamination by spectrophotometry, 163 patient samples were utilized in the study. In the FF, the progesterone levels were negatively correlated with (a) hydrogen peroxide scavenging capacity (HPSC) (r = −0.294, P < 0.0001), (b) total number of follicles (r = −0.246, P < 0.001) and (c) total number of oocytes punctured (r = −0.268, P = 0.0001). The concentration of serum estradiol exhibited a positive correlation with intrafollicular HPSC (r = 0.165, P = 0.037). Our data indicate that the FF levels of estradiol and progesterone are related to the FF redox status, which is closely associated with the number of oocytes obtained during ICSI procedures.

Reduced ovarian response to controlled ovarian stimulation is associated with increased oxidative stress in the follicular environment

Serum estradiol (E2) level is routinely used to monitor the ovarian response during controlled ovarian hyperstimulation (COH) and the concentration of serum E2 may influence the oocyte quality and pregnancy outcome. However, the knowledge on the association between COH induced serum E2 level, oocyte quality and embryo development is limited. Therefore we investigated the association between serum E2 level, oxidative stress in the follicular fluid and granulosa cells (GCs) response to elucidate the association between E2 level and embryological outcome. In this study, patients (n = 30) undergoing ART were categorized as 'normal responders' (NR, n = 10), 'poor responders' (PR, n = 10) and hyper responders (HR, n = 10). The follicular fluid malondialdehyde (MDA) level was determined. The total RNA extracted from GCs was subjected to analyse the relative abundance of transcripts of stress response genes (P53, caspase 3,8-oxoguanine DNA glycosylase, OGG1 and heat shock protein 70; HSP70) and embryological outcome was noted. Follicular fluid MDA level was significantly higher in PR (p < 0.01) compared NR and HR whereas number of top-quality embryos were significantly lower in PR and HR compared to NR (p < 0.01). The relative expression of P53, HSP70, and OGG1 in GCs was significantly elevated in PR (p < 0.05-0.01). An inverse relationship was established between serum E2 level vs follicular MDA level (r = -0.45; p < 0.01) and follicular MDA level vs. number of top-quality embryos (r = -0.45; p < 0.01). Hence, patients with low serum E2 had elevated oxidative stress in their follicular environment and poor quality embryos implicating the risk of oxidative stress in patients with poor ovarian response.

Necroptosis in stressed ovary

Stress is deeply rooted in the modern society due to limited resources and large competition to achieve the desired goal. Women are more frequently exposed to several stressors during their reproductive age that trigger generation of reactive oxygen species (ROS). Accumulation of ROS in the body causes oxidative stress (OS) and adversely affects ovarian functions. The increased OS triggers various cell death pathways in the ovary. Beside apoptosis and autophagy, OS trigger necroptosis in granulosa cell as well as in follicular oocyte. The OS could activate receptor interacting protein kinase-1(RIPK1), receptor interacting protein kinase-3 (RIPK3) and mixed lineage kinase domain-like protein (MLKL) to trigger necroptosis in mammalian ovary. The granulosa cell necroptosis may deprive follicular oocyte from nutrients, growth factors and survival factors. Under these conditions, oocyte becomes more susceptible towards OS-mediated necroptosis in the follicular oocytes. Induction of necroptosis in encircling granulosa cell and oocyte may lead to follicular atresia. Indeed, follicular atresia is one of the major events responsible for the elimination of majority of germ cells from cohort of ovary. Thus, the inhibition of necroptosis could prevent precautious germ cell depletion from ovary that may cause reproductive senescence and early menopause in several mammalian species including human.

Long-Term Moderate Oxidative Stress Decreased Ovarian Reproductive Function by Reducing Follicle Quality and Progesterone Production

Ovarian aging is a long-term and complex process associated with a decrease in follicular quantity and quality. The damaging effects of reactive oxygen species (ROS) in ovarian aging and ovarian aging-associated disorders have received relatively little attention. Thus, we assessed if the oxidative stress induced by long-term (defined by the Environmental Protection Agency as at least 30 days in duration) moderate ozone inhalation reduced ovarian reserves, decreased ovarian function and induced ovarian aging-associated disorders. The expression of oxidative stress markers and antioxidant enzymes was used to determine the degree of oxidative stress. Ultrastructural changes in ovarian cells were examined via electron microscopy. The ovarian reserve was assessed by measuring multiple parameters, such as the size of the primordial follicle pool and anti-Müllerian hormone (AMH) expression. The estrous cycle, hormone levels and fertility status were investigated to assess ovarian function. To investigate ovarian aging-associated disorders, we utilized bone density and cardiovascular ultrasonography in mice. The levels of oxidized metabolites, such as 8-hydroxy-2´-deoxyguanosine (8-OHdG), 4-hydroxynonenal (4-HNE) and nitrotyrosine (NTY), significantly increased in ovarian cells in response to increased oxidative stress. The ultrastructural analysis indicated that lipid droplet formation and the proportion of mitochondria with damaged membranes in granulosa cells were markedly increased in ozone-exposed mice when compared with the control group. Ozone exposure did not change the size of the primordial follicle pool or anti-Müllerian hormone (AMH) expression. The estrogen concentration remained normal; however, progesterone and testosterone levels decreased. The mice exposed to ozone inhalation exhibited a substantial decrease in fertility and fecundity. No differences were revealed by the bone density or cardiovascular ultrasounds. These findings suggest that the decreased female reproductive function caused by long-term moderate oxidative damage may be due to a decrease in follicle quality and progesterone production.

Control of Oocyte Growth and Development by Intercellular Communication Within the Follicular Niche

In the mammalian ovary, each oocyte grows and develops within its own structural and developmental niche-the follicle. Together with the female germ cell in the follicle are somatic granulosa cells, specialized companion cells that surround the oocyte and provide support to it, and an outer layer of thecal cells that serve crucial roles including steroid synthesis. These follicular compartments function as a single physiological unit whose purpose is to produce a healthy egg, which upon ovulation can be fertilized and give rise to a healthy embryo, thus enabling the female germ cell to fulfill its reproductive potential. Beginning from the initial stage of follicle formation and until terminal differentiation at ovulation, oocyte and follicle growth depend absolutely on cooperation between the different cellular compartments. This cooperation synchronizes the initiation of oocyte growth with follicle activation. During growth, it enables metabolic support for the follicle-enclosed oocyte and allows the follicle to fulfill its steroidogenic potential. Near the end of the growth period, intra-follicular interactions prevent the precocious meiotic resumption of the oocyte and ensure its nuclear differentiation. Finally, cooperation enables the events of ovulation, including meiotic maturation of the oocyte and expansion of the cumulus granulosa cells. In this chapter, we discuss the cellular interactions that enable the growing follicle to produce a healthy oocyte, focusing on the communication between the germ cell and the surrounding granulosa cells.

Soy isoflavones administered to rats from weaning until sexual maturity affect ovarian follicle development by inducing apoptosis

Twenty-one-day-old female Wistar rats were treated daily with orally administered soy isoflavones (SIFs) at concentrations of 50, 100, or 200 mg/kg body weight from weaning until sexual maturity (3 mo.), and ovarian follicle development was evaluated. At the end of the treatment period, the ultrastructure of the ovarian granulosa cells was examined by transmission electron microscopy. The apoptotic cell death of ovarian granulosa cells was detected using TUNEL staining. The mRNA expression levels of caspase-3, caspase-8, caspase-9, Bcl2, Bax, and Fas were determined by real-time quantitative PCR. The protein expression levels of caspase-3, Bcl2, Bax, and Fas were determined by western blotting. Our data showed that exposure to SIFs resulted in morphological changes consistent with ovarian granulosa cell apoptosis. The percentage of TUNEL-positive granulosa cells was increased. The mRNA expression levels of the apoptosis-related genes caspase-3, caspase-8, caspase-9, Bax, and Fas increased significantly. The protein levels of Bax, Fas, and cleaved caspase-3 were also increased. These results indicate that the exposure of rats to modest doses of SIFs from weaning until sexual maturity can affect ovarian follicle development by inducing apoptosis. The mechanism of SIF-induced alterations in ovarian follicle development may involve the activation of Fas-mediated and Bcl2/Bax-mediated apoptotic signaling pathways.

Efficacy of ovarian tissue cryopreservation in a major European center

PURPOSE

To evaluate the effect of cryopreservation and thawing of ovarian tissue from oncological patients opting for fertility preservation on ovarian tissue viability.

METHODS

In this prospective cohort study, the ovarian tissue viability before and after cryopreservation and thawing was measured for 25 newly diagnosed oncological patients who had their ovarian tissue cryopreserved. Outcome measures were follicle integrity (histology), follicle viability (Calcein viability assay), steroid hormone production (estradiol and progesterone production in vitro) and overall tissue viability (glucose uptake in vitro). This study was conducted at a Cryobank for storage of ovarian tissue in a university hospital.

RESULTS

Cryopreserved/thawed ovarian tissue showed a decreased glucose uptake when compared to tissue that had not been cryopreserved. In addition, a diminished E2 and P4 production was observed after cryopreservation and thawing, despite the fact that numbers of viable follicles as determined by the Calcein viability assay were comparable. Histological examination revealed a higher percentage of degenerated follicles after cryopreservation and thawing.

CONCLUSIONS

Ovarian tissue cryopreservation and thawing impairs the viability of ovarian tissue in oncological patients opting for fertility preservation.

Ovarian aging-like phenotype in the hyperandrogenism-induced murine model of polycystic ovary

There are prominently similar symptoms, effectors, and commonalities in the majority of characteristics between ovarian aging and polycystic ovarian syndrome (PCOS). Despite the approved role of oxidative stress in the pathogenesis of PCOS and aging, to our knowledge, the link between the PCO(S) and aging has not been investigated yet. In this study we investigated the possible exhibition of ovarian aging phenotype in murine model of PCO induced by daily oral administration of letrozole (1 mg/kg body weight) for 21 consecutive days in the female Wistar rats. Hyperandrogenization showed irregular cycles and histopathological characteristics of PCO which was associated with a significant increase in lipid peroxidation (LPO) and reactive oxygen species (ROS) and decrease in total antioxidant capacity (TAC) in serum and ovary. Moreover, serum testosterone, insulin and tumor necrosis factor-alpha (TNF-α) levels, and ovarian matrix metalloproteinase-2 (MMP-2) were increased in PCO rats compared with healthy controls, while estradiol and progesterone diminished. Almost all of these findings are interestingly found to be common with the characteristics identified with (ovarian) aging showing that hyperandrogenism-induced PCO in rat is associated with ovarian aging-like phenotypes. To our knowledge, this is the first report that provides evidence regarding the phenomenon of aging in PCO.

Dietary lipid and cholesterol induce ovarian dysfunction and abnormal LH response to stimulation in rabbits

BACKGROUND/AIM

Excess of fat intake is dramatically increasing in women of childbearing age and results in numerous health complications, including reproductive disorders. Using rabbit does as a biomedical model, the aim of this study was to evaluate onset of puberty, endocrine responses to stimulation and ovarian follicular maturation in females fed a high fat high cholesterol diet (HH diet) from 10 weeks of age (i.e., 2 weeks before normal onset of puberty) or a control diet (C diet).

METHODOLOGY/PRINCIPAL FINDINGS

Three experiments were performed, each including 8 treated (HH group) and 8 control (C group) does. In experiment 1, the endocrine response to Gonadotropin releasing hormone (GnRH) was evaluated at 13, 18 and 22 weeks of age. In experiment 2, the follicular population was counted in ovaries of adult females (18 weeks of age). In experiment 3, the LH response to mating and steroid profiles throughout gestation were evaluated at 18 weeks of age. Fetal growth was monitored by ultrasound and offspring birth weight was recorded. Data showed a significantly higher Luteinizing hormone (LH) response after induction of ovulation at 13 weeks of age in the HH group. There was no difference at 18 weeks, but at 22 weeks, the LH response to GnRH was significantly reduced in the HH group. The number of atretic follicles was significantly increased and the number of antral follicles significantly reduced in HH does vs. controls. During gestation, the HH diet induced intra-uterine growth retardation (IUGR).

CONCLUSION

The HH diet administered from before puberty onwards affected onset of puberty, follicular growth, hormonal responses to breeding and GnRH stimulation in relation to age and lead to fetal IUGR.

Follicular fluid hydrogen peroxide and lipid hydroperoxide in bovine antral follicles of various size, atresia, and dominance status

PURPOSE

To avoid inducing a state of oxidative stress (OS), assisted reproductive technologies (ART) must maintain a balance of reactive oxygen species (ROS) and antioxidants during the in vitro culture of oocytes. However, oocyte requirements and tolerance thresholds for ROS during in vivo development are still unclear. Previous studies have examined ROS levels in follicular fluid (FF) using pooled samples or according to follicle size. This study sought to examine two OS markers, lipid hydroperoxides (LPO) and hydrogen peroxide (H2O2), in FF of individually sampled follicles from bovine ovary pairs according to follicle size, atresia, and dominance status.

METHODS

TUNEL and cleaved Caspase-3 labeling were used to identify apoptotic granulosa cells and determine follicle atresia status. LPO were measured directly for the first time in FF.

RESULTS

Non-atretic follicles and dominant follicles contained more FF H2O2 than atretic follicles and corresponding subordinate follicles, respectively. FF LPO did not vary in relation to atretic status, and no difference existed between dominant and subordinate follicles. However, FF LPO was significantly lower in first subordinate follicles than in the second subordinate follicles from each ovary pair. Neither H2O2 nor LPO levels correlated with follicle size.

CONCLUSIONS

These data provide clear evidence that the events of antral folliculogenesis are relevant to ROS dynamics in vivo. Furthermore, such studies will help to optimize in vitro conditions for oocyte culture protocols, particularly when combined with a comparison of oocyte quality with respect to source follicle characteristics.

Follicular growth and atresia in mammalian ovaries: regulation by survival and death of granulosa cells

The mammalian ovary is an extremely dynamic organ in which a large majority of follicles are effectively eliminated throughout their reproductive life. Due to the numerous efforts of researchers, mechanisms regulating follicular growth and atresia in mammalian ovaries have been clarified, not only their systemic regulation by hormones (gonadotropins) but also their intraovarian regulation by gonadal steroids, growth factors, cytokines and intracellular proteins. Granulosa cells in particular have been demonstrated to play a major role in deciding the fate of follicles, serving molecules that are essential for follicular growth and maintenance as well as killing themselves by an apoptotic process that results in follicular atresia. In this review, we discuss the factors that govern follicular growth and atresia, with a special focus on their regulation by granulosa cells. First, ovarian folliculogenesis in adult life is outlined. Then, we explain about the regulation of follicular growth and atresia by granulosa cells, in which hormones, growth factors and cytokines, death ligand-receptor system and B cell lymphoma/leukemia 2 (BCL2) family members (mitochondria-mediated apoptosis) are further discussed.

Letrozole induces hepatotoxicity without causing oxidative stress: the protective effect of melatonin

AIM

The aim of this study was to determine the effects of letrozole (LTZ), an aromatase inhibitor (AI), and melatonin (MLT) on hepatic function and oxidative stress in female rats.

MATERIAL AND METHODS

A total of 32 female rats were divided equally into four groups (n = 8). Control group received saline (0.5 ml/day, oral gavage). LTZ was administered to rats by daily oral gavage at 1 mg/kg dose. LTZ + MLT group was given LTZ (1 mg/kg, oral gavage) plus MLT (0.5 mg/kg/day, s.c.). MLT group was given MLT (0.5 mg/kg/day) by s.c. injection. The activities of superoxide dismutase (SOD) and catalase (CAT) and malondialdehyde (MDA) levels were measured in liver tissue. Total antioxidant capacity (TAC), total oxidant status (TOS), ALT, AST, GGT, ALP, LDH, bilirubin, BUN, creatinine, total cholesterol (TC), high-density lipoprotein (HDL) and triglyceride (TG) were assayed in serum samples.

RESULTS

The oxidative stress parameters did not differ between groups. LTZ administration increased hepatic function parameters such as AST, LDH, ALP, bilirubin and MLT improved the disturbances of hepatic function. LTZ caused minimal histological changes in liver tissue and MLT treatment reversed those dejenerations.

DISCUSSION

LTZ may cause hepatotoxicity without inducing oxidative stress and MLT restores hepatic activity.

Could oxidative stress influence the in-vitro maturation of oocytes?

In the efforts aimed at improving the quality of in-vitro-matured human oocytes, the dynamic balance and roles of pro-/antioxidants merit further consideration. In-vitro maturation (IVM) is emerging as a popular technology at the forefront of fertility treatment and preservation. However, standard in-vitro culture conditions exert oxidative stress or an imbalance between oxidants and antioxidants. Reactive oxygen species (ROS) are oxygen-derived molecules formed as intermediary products of cellular metabolism. By acting as powerful oxidants, ROS can oxidatively modify any molecule, resulting in structural and functional alterations. ROS are neutralized by an elaborate defence system consisting of enzymatic and nonenzymatic antioxidants. This review captures the inherent and external factors that may modulate the oxidative stress status of oocytes. It discusses the suspected impacts of oxidative stress on the gamut of events associated with IVM, including prematuration arrest, meiotic progression, chromosomal segregation, cytoskeletal architecture and gene expression. In-vivo and in-vitro strategies that may overcome the potential influences of oxidative stress on oocyte IVM are presented. Future studies profiling the oxidative stress status of the oocyte may permit not only the formulation of a superior IVM medium that maintains an adequate pro-/antioxidant balance, but also the identification of predictors of oocyte quality.

Anti-mullerian hormone is associated with advanced glycosylated end products in lean women with polycystic ovary syndrome

OBJECTIVE

Oocyte maturation process characterizes polycystic ovary syndrome (PCOS). The mechanisms of this abnormality leading to chronic anovulation are under investigation. Advanced glycosylated end products (AGEs), a marker of oxidative stress linked with oocyte maturation are localized in granulosa cells and are increased in sera, in women with PCOS. The aim of this study was to investigate the relationship, whether there is an association between the anti-mullerian hormone (AMH), a hormone produced by granulosa cells and AGEs in ovulatory and anovulatory PCOS (PCOS-Anov), as well as in non-PCOS anovulatory (Non-PCOS Anov) women. Design Cross-sectional study.

METHODS

Data from sixty women with PCOS (37 anovulatory and 23 regularly ovulating) were compared with eleven Non-PCOS Anov women and 25 normal women. In each subject biochemical, hormonal, and ultrasonographic parameters were studied.

RESULTS

AMH values were statistically significantly higher in PCOS-Anov (7.63+/-3.12) in comparison with ovulatory PCOS (PCOS-Ov; 4.92+/-2.50), Non-PCOS Anov (3.66+/-1.4), and controls (4.02+/-1.27 ng/ml). AGEs demonstrated a similar pattern: 8.70+/-1.65 in PCOS-Anov, 7.43+/-1.79, PCOS-Ov, 5.21+/-0.09, Non-PCOS Anov, and 5.85+/-0.89 U/ml in controls (P<0.005 for all comparison respectively). Follicle number was significantly higher in PCOS-Anov in comparison with other groups. A significant positive correlation between AMH and AGEs was observed (r: 0.326, P<0.01), and with the estimated AMH/AGEs ratio to follicle number (r: 0.42, P: 0.0001) and the presence of anovulation.

CONCLUSIONS

These data suggest that an oxidative marker, AGEs, and AMH, may interact in the anovulatory mechanisms in women with PCOS.

Methoxychlor and estradiol induce oxidative stress DNA damage in the mouse ovarian surface epithelium

Estrogenic compounds such as 17beta-estradiol (E(2)) and methoxychlor (MXC) induce oxidative stress damage in breast cells and mouse ovarian follicles, respectively. However, little is known about whether estrogenic compounds cause oxidative stress in the ovarian surface epithelium (OSE). Thus, this work tested the hypothesis that E(2) and MXC cause oxidative stress in the OSE. To test this hypothesis, we employed an improved mouse tissue culture assay in which OSE cells were treated with hydrogen peroxide (H2O2; positive control), MXC, or E(2) +/- the anti-oxidant vitamin E, or progesterone. The cells then were subjected to a novel direct immunofluorescent assay in which cells in the microtiter plate were reacted with antibodies that detect oxidative damage to DNA (8-hydroxy-2'-deoxyguanosine). The signal was identified with a tyramide Alexa Fluor fluorescent probe and quantified by microfluorimetry. Correction for cellularity was carried out for each well with a fluorescent DNA dye system (CyQuant) at a different wavelength. After 24 h, the mean Alexa Fluor CyQuant ratio was 11.3 +/- 0.9 for controls, 132 +/- 15 for H2O2 treated positive control cells (p < or = 0.01 from control), 105 +/- 6.6 for E(2) treated cells (p < or = 0.01 from control), and 64 +/- 5.1 for MXC-treated cells (p < or = 0.01 from control). After 72 h, the mean ratio was 121 +/- 10.6 for controls, 391 +/- 23 for H2O2 treated cells (p < or = 0.01 from control), 200 +/- 15 for E(2) treated cells (p < or = 0.03), and 228 +/- 21 for MXC-treated cells (p < or = 0.01). Further, vitamin E, but not progesterone, protected OSE cells from E(2)- and MXC-induced oxidative damage. This study demonstrates the feasibility of direct immunofluorescent quantitation of DNA adducts in cell cultures without DNA extraction. Moreover, these data indicate that E(2) and MXC produce oxidative DNA damage in the OSE, and that this damage is prevented by the anti-oxidant vitamin E.

Evaluation of the relationship between follicular fluid oxidative stress, ovarian hormones, and response to gonadotropin stimulation

OBJECTIVE

To investigate the relationship between oxidative stress and the underlying causes of infertility, preovulatory ovarian hormones, and ovarian response to gonadotropin stimulation in patients undergoing assisted reproductive techniques.

DESIGN

Prospective, cross-sectional study.

SETTING

Assisted conception unit, university hospital.

PATIENT(S)

One hundred thirty women presenting with infertility, of the following types: male factor (n = 56), unexplained (n = 36), tubal factor (n = 16), polycystic ovary syndrome (n = 15), and endometriosis (n = 7).

INTERVENTION(S)

Follicular fluid (FF) and peripheral blood samples were collected at oocyte retrieval.

MAIN OUTCOME MEASURE(S)

Blood and FF samples were analyzed for inhibin A, inhibin B, activin A, anti-Müllerian hormone, and E(2) by using ELISA. Total antioxidant capacity (TAC) was measured in plasma and FF by using a calorimetric microplate assay.

RESULT(S)

There was no significant relationship between plasma or FF TAC and the underlying etiology of infertility. There was a statistically significant positive association between FF E(2) levels and TAC (r = 0.26). Higher antral follicle count, delta E(2) (day 3 E(2) minus day 2 E(2)), preovulatory serum anti-Müllerian hormone, inhibin B, and E(2) were associated with good ovarian response, whereas higher FF E(2) was associated with a statistically significant poor response. No significant direct relationship was observed between TAC and ovarian response as well as between TAC or any of the parameters measured and pregnancy outcome.

CONCLUSION(S)

Oxidative stress has an impact on the production of granulosa cell steroid hormones, in particular E(2), which is an important predictor of ovarian response. The positive association between FF E(2) and total antioxidant capacity suggests that E(2) may play a role in the ovarian antioxidant-oxidant balance.

Steroidogenic changes and steady state amount of messenger RNA encoding steroidogenic enzymes, gonadotropin receptors and cell-death signalling in the dominant ovarian follicle during estradiol-induced atresia in cattle

Changes in steroidogenic function and associated gene expression were characterized in dominant ovarian follicles (DF) of cattle where follicles were induced to become atretic by systemic administration of estradiol benzoate (EB). In experiment 1, follicular fluid (FF) steroid concentrations in the DF were measured at 12-hourly time points for 48 h in heifers treated with 1 mg EB i.m./500 kg body weight (EB; n=20) as compared with untreated controls (C; n=19). Treatment with EB promoted a transient reduction in circulating FSH, a rapid (12 h) and sustained reduction in FF estradiol, a rapid (12 h) but transient reduction in FF progesterone and a delayed (36 h) increase in FF testosterone concentrations. In experiment 2, whole follicular wall tissue was collected from DF of mature non-lactating cows allocated to a 0 h control group (0 HC: n=7), a 24h control group (24 HC; n=7) or an EB-treated group where tissue was collected 24 h after administration of 1 mg EB i.m./500 kg body weight (EB; n=8). As for experiment 1, EB promoted a transient reduction in circulating FSH, a pronounced reduction in FF estradiol and a smaller but significant reduction in FF progesterone concentrations. Semi-quantitative RT-PCR on follicular wall tissue revealed that the loss in estrogen activity at 24 h after EB was associated with two-fold reduction in aromatase mRNA, with an apparent acceleration in loss of 17alpha-hydroxylase mRNA. Expression of genes for gonadotropin receptors (LHR and FSHR) and a cell-death signalling pathway (Fas antigen and Fas ligand) were unchanged during the initial 24h of EB-induced atresia. These results suggest that EB initiates atresia in dominant ovarian follicles through a rapid suppression of follicular estradiol synthesis, an effect associated with down-regulation of the aromatase gene. A transient suppression in circulating FSH following administration of EB appears to have initiated these events, and it is suggested that subsequent processes involved in atresia follow this loss in estrogenic function.

Lipid peroxidation and renal cell carcinoma: further supportive evidence and new mechanistic insights

We have recently proposed lipid peroxidation as a unifying mechanistic pathway by which several seemingly unrelated risk/protective factors (obesity, hypertension, diabetes, smoking, oophorectomy/hysterectomy, parity, antioxidants) affect renal cell carcinoma development. In experimental studies, increased lipid peroxidation is a principal mechanistic pathway in renal carcinogenesis induced by different chemicals. In this communication, we provide additional lines of evidence that further support a role for lipid peroxidation on renal cell cancer development. (1) Lipid peroxidation may explain the role of other risk (analgesic use, pre-eclampsia) or protective (alcohol intake, oral contraceptives) factors for renal cell carcinoma. (2) Additional experimental evidence supports lipid peroxidation as an important mechanism in renal carcinogenesis, and (3) Existing evidence support a cross-talk between the lipid peroxidation pathway and other pathways that are relevant to renal carcinogenesis, such as apoptosis, VHL, and possibly other pathways.

Histological and steroidogenic changes in dominant ovarian follicles during oestradiol-induced atresia in heifers

Histological and steroidogenic changes within dominant ovarian follicles (DFs) undergoing atresia following systemic administration of oestradiol benzoate (ODB) were characterized in beef heifers. At 5.6 ± 0.1 days after the onset of oestrus, heifers received 1 mg ODB i.m./500 kg body weight (ODB; n = 15) or served as controls (n = 15). Timing of treatment initiation was designated as hour (h) 0 on day (d) 0, and coincided with the presence of the DF of the first follicular wave (DF1). Within treatments, the DF1 was collected following ovariectomy in four animals at h 12, h 36 or after ultrasonic detection of a new wave (NW) of ovarian follicular development. In heifers of the NW groups (n = 7 per treatment), blood samples were collected at intervals of 20 min for 12 h beginning at h − 12, 0, 24 and 48 to characterize circulating LH patterns. Administration of ODB suppressed (P < 0.01) mean concentrations of LH at h 24 and h 48 by preventing (P < 0.05) the increase in LH pulse amplitude observed in controls, but had no effect on FSH. Follicular fluid (FF) concentrations of androgens and oestradiol were reduced at h 36 in the ODB-treated group. The diameter of the DF1 and the number of granulosa cell layers were also reduced in ODB-treated as compared with control heifers. Treatment differences were not observed in the proportion of apoptotic granulosa cells as assessed using the TUNEL assay method, and timing of a new wave of follicular development (d 4.6 ± 0.2) was similar (P > 0.1) among treatments. A prominent characteristic of oestradiol-induced atresia of the DF1 of the oestrous cycle in heifers was a loss in oestrogenic function associated with reduced LH support. However, the timing of new follicular development may be influenced by a factor(s) other than the status of the DF undergoing oestradiol-induced atresia.

Reactive oxygen species in ovarian physiology

Cells living under aerobic conditions always face oxygen paradox. Oxygen is necessary for cells to maintain their lives. However, reactive oxygen species such as superoxide radical ( ), hydroxyl radical (OH^-) and hydrogen peroxide (H₂O₂) are generated from oxygen and damage cells. Oxidative stress occurs as a consequence of excessive production of reactive oxygen species and impaired antioxidant defense systems. Antioxidant enzymes include: superoxide dismutase (SOD), which is a specific enzyme to scavenge superoxide radicals; copper-zinc SOD, located in the cytosol; and manganese SOD, located in the mitochondria. Both types of SOD belong to the first enzymatic step to scavenge superoxide radicals. It has been reported that a number of local factors such as cytokines, growth factors and eicosanoids are involved in the regulation of ovarian function, in addition to gonadotropins and ovarian steroid hormones. Since reactive oxygen species are generated and SOD is expressed in the ovary, there is a possibility that reactive oxygen species and SOD work as local regulators of ovarian function. The present review reports that reactive oxygen species and their scavenging systems play important roles in several processes of reproductive physiology, including follicular development, oocyte maturation, ovulation, corpus luteum function and follicular atresia. (Reprod Med Biol 2005; 4: 31- 45).

Luteal stage dependence of pituitary response to gonadotrophin-releasing hormone in cyclic dairy ewes subjected to synchronisation of ovulation

Possible hormonal aberrations precluding conception or maintenance of pregnancy in dairy ewes subjected to ovulation synchronisation were investigated in this study. The pituitary response to exogenous gonadotrophin-releasing hormone (GnRH) was tested at different luteal stages in 36 ewes. Oestruses were synchronised by using progestagen-impregnated sponges and the animals were randomly allotted into one of three treatment groups (A, B and C; n = 12 for each). Treatments commenced on Days 4, 9 and 14 of the new cycle (oestrus was defined as Day 0). Ewes were given two GnRH injections, 5 days before and 36 h after a prostaglandin F2α (PGF2α) injection, and the animals were inseminated 12–14 h after the second GnRH injection (modified OVSYNCH). For luteinising hormone (LH) determination blood samples were withdrawn from six ewes of each group at the time of GnRH administration, and 30, 90, 180, 270 and 360 min later. Progesterone was assayed in samples taken every other day starting from oestrus and for 17 days after the second GnRH injection, and in an additional sample collected on the day of insemination. After the first GnRH injection, the LH concentration was higher in Group C than in Groups B and A (mean ± s.d.: 64.8 ± 10.0 ng mL−1, 41.3 ± 3.7 ng mL−1 and 24.6 ± 9.0 ng mL−1, respectively; P < 0.05), whereas after the second GnRH injection a uniform LH release was found in all groups. PGF2α caused a significant decrease in progesterone (P4) concentration in all groups; however, at artificial insemination ewes that conceived had significantly lower P4 concentration in comparison with those that failed to conceive. As early as Day 5, pregnant animals had higher P4 concentrations than non-pregnant animals. Overall, 21 animals conceived (seven, nine and five ewes from Groups A, B and C, respectively). These results indicate that the proposed protocol is equally effective in inducing a preovulatory LH surge at any stage of the luteal phase, and that elevated P4 concentration along with a delayed P4 increase should be considered as a causative factor for inability to conceive.

Corpora lutea induced by gonadotrophin-releasing hormone treatment of anoestrous Welsh Mountain ewes: reduced sensitivity to luteinizing hormone in vivo and to chorionic gonadotrophin in vitro

Seasonally anoestrous Welsh Mountain ewes received 250 ng gonadotrophin-releasing hormone (GnRH) every 2 h, with (Group 1;n= 13) or without (Group 2;n= 14) progesterone priming for 48 h. Fourteen control ewes (Group 3) were studied during the luteal phase in the breeding season. Animals in Group 4 (n= 12) received progesterone priming followed by 250 ng GnRH at increasing frequency for 72 h, while ewes in Group 5 (n= 13) were given three bolus injections of 30 μg GnRH at 90-min intervals. All treatment regimens induced ovulation. However, only corpora lutea (CL) from ewes in Group 3 (breeding season) or Group 4 exhibited normal luteal function. Luteal luteinizing hormone (LH) receptor levels were significantly higher on day 12 than day 4, and CL from groups with adequate CL (3 and 4) had significantly higher125I-human chorionic gonadotrophin (hCG)-binding levels than the three groups with inadequate CL on day 12. LH-binding affinity was unchanged. Exogenous ovine LH (10 μg)in vivoon days 3 or 11 after ovulation induced a pulse of progesterone in ewes with adequate CL: however, ewes in Groups 1, 2 and 5 showed no significant response. Basal progesterone secretionin vitrowas significantly greater on day 4 than on day 12. Maximal steroidogenic responses of adequate and inadequate CL to hCG and to dibutyryl cyclic-3′,5′-AMP were similar at both stages of the luteal phase. However, the EC50for hCG on days 4 and 12 was 10-fold lower for groups with an adequate CL (0.1 IU hCG/ml) than for inadequate-CL groups (1 IU hCG/ml;P<0.05). Thus, in addition to the well-characterized premature sensitivity of GnRH-induced inadequate CL to endometrial luteolysin, we have shown (1) a marked decrease in total number of cells in the CL, a profound reduction in vascular surface area, and a decrease in mean large luteal cell volume (with no change in large luteal cell numbers), (2) decreased luteal LH receptor and progesterone content compared with adequate CL and (3) that CL that were becoming, or were destined to become, inadequate failed to respond to ovine LHin vivoand were 10-fold less sensitive to hCG in terms of luteal progesterone secretionin vitro.

Influences of FSH and EGF on primordial follicles during in vitro culture of caprine ovarian cortical tissue

Factors that control the onset of folliculogenesis are critical to female gamete production, but poorly understood. The aim of the present study was to investigate the effects of FSH and EGF on the activation and growth of goat primordial follicles in vitro. To this end, pieces of goat ovarian cortex were cultured in vitro for 1, 3 or 5 days, at 39 degrees C in an atmosphere containing 5% CO(2), in minimum essential medium supplemented with insulin, transferrin, selenium, pyruvate, glutamine, hypoxanthine, BSA, penicillin, streptomycin and fungizone and with or without FSH (100 ng/ml) and/or EGF (100 ng/ml). At the end of the culture periods, the relative proportions of primordial, intermediate, primary and secondary follicles were calculated and compared with those in non-cultured tissue. In addition, mitotic activity of granulosa cells was studied by immunohistochemistry for proliferating cell nuclear antigen (PCNA). In brief, it was found that goat primordial follicles activate spontaneously during culture in vitro and, while neither FSH nor EGF affected the proportion of primordial follicles that entered the growth phase, both stimulated an increase in oocyte and follicle diameter, especially in intermediate and primary follicles cultured for 5 days. On the other hand, there was no significant effect of culture or either growth factor on the proportion of PCNA-stained growing follicles. Contrary to expectations, neither FSH nor EGF affected follicle viability or integrity during culture, since the percentages of intact follicles did not differ between control, FSH and/or EGF containing medium. In conclusion, this study demonstrated that goat primordial follicles activate spontaneously in vitro, and that both FSH and EGF stimulate an increase in follicle size by promoting oocyte growth.

Survival and growth of goat primordial follicles after in vitro culture of ovarian cortical slices in media containing coconut water

The development of culture systems to support the initiation of growth of primordial follicles is important to the study of the factors that control the earliest stages of folliculogenesis. We investigated the effectiveness of five culture media, two supplements and three culture periods on the survival and growth of goat primordial follicles after culturing ovarian cortex. The media were based on minimal essential minimum (MEM) and coconut water solution (CWS) added in the proportion of 0, 25, 50, 75 or 100%. The two supplements were none versus supplemented with insulin-transferrin-selenium, pyruvate, glutamine, hypoxanthine, and BSA. Pieces of goat ovarian cortex were cultured in the media for 1, 3 or 5 days and representative samples were evaluated at day 0 as non-cultured controls. The replicates were the two ovaries of five mixed breed goats. The number of primordial, intermediate, primary and secondary follicles at each period of culture and the number of degenerated follicles were evaluated. Mitotic activity of granulosa cells was studied by immunolocalization of proliferating cell nuclear antigen (PCNA). The number of follicles in each stage and degenerated follicles were statistically analyzed by ANOVA using a factorial design and the significance of differences assessed using Tukey test. Chi-square test was used to compare the percentage of follicles with PCNA positive granulosa cells. As the culture period progressed, the number of primordial follicles fell and there was a significant increase in the number of primary follicles. The fall in the number of primordial follicles was particularly marked after 1 day culture. No effect of media on the number of primordial and primary follicles was observed after culture, but MEM as well as supplements increased the number of intermediate follicles. Follicular degeneration was kept at the same level after culture in the media tested, except for pure CWS that increased the number of degenerated follicles. In contrast, addition of supplements to culture media reduced follicular degeneration. In non-cultured tissue, PCNA was expressed in granulosa cells of 31.6% of the growing follicles. This percentage had not significantly changed after 5 days culture in the various media, indicating the maintenance of proliferation activity of granulosa cells during culture. In conclusion, it is shown that goat primordial follicles may be successfully activated after in vitro culture in all media tested. However, when pure CWS is used the follicular degeneration is enhanced, but the addition of supplements to culture media decrease follicular degeneration.

Identification of genes involved in apoptosis and dominant follicle development during follicular waves in cattle

We hypothesize that granulosa and theca cells from growing dominant follicles, with relatively high intrafollicular concentrations of estradiol, have a greater expression of genes involved in inhibiting apoptosis pathways and lower expression of genes involved in apoptosis pathways than growing subordinate follicles with lower estradiol concentrations. Using the well-characterized bovine dominant follicle model, we collected granulosa and theca cells from individual dominant and the largest subordinate follicle 3 days after initiation of a follicular wave in four animals. Based on ultrasound analysis, both follicle types were in the growth phase at the time of ovariectomy. However, dominant follicles were larger (9.8 +/- 1.0 versus 7.6 +/- 0.6 mm in diameter, P < 0.05) and had greater intrafollicular concentrations of estradiol (132.2 +/-3 8.5 versus 24.1 +/- 12.1 ng/ml, P < 0.05), compared with the largest subordinate follicles. We used bovine cDNA microarrays, which contained a total of 1400 genes, including a subset of 53 genes known to be involved in apoptosis pathways, to determine which apoptosis and marker genes from each of the four dominant versus subordinate follicles were potentially differentially expressed. Using a low stringency-screening criterion, 22 genes were identified. Quantitative real-time polymerase chain reaction confirmed that 16 of these genes were differentially expressed. Our novel results demonstrate that the high intrafollicular concentrations of estradiol in growing dominant follicles were positively associated with enhanced expression of mRNAs in granulosa cells for aromatase, LH receptor, estradiol receptor beta, DICE-1, and MCL-1, compared with granulosa cells from subordinate follicles (all survival-associated genes). In contrast, the relatively low intrafollicular concentrations of estradiol in growing subordinate follicles were positively associated with enhanced expression of mRNAs in granulosa cells for beta glycan, cyclo-oxygenase-1, tumor necrosis factor alpha, caspase-activated DNase, and DRAK-2, and in theca cells for beta glycan, caspase 13, P58(IPK), Apaf-1, BTG-3, and TS-BCLL, compared with granulosa or theca cells from dominant follicles (genes that are all associated with cell death and/or apoptosis). We suggest that that these genes may be candidate estradiol target genes and that they may be early markers for the final stages of follicle differentiation or initiation of apoptosis and thus selection of dominant follicles during follicular waves.

The role of sex steroid receptors in sheep female reproductive physiology

Cell responsiveness to steroid hormones is related to the number and affinity of its receptors, thus factors affecting steroid expression will influence tissue sensitivity and functionality. The present review discusses the role of oestrogen and progesterone receptors in sheep female reproductive physiology. The mechanism of steroid hormone action in the target cell is introduced first; the tissue distribution, physiological functions and regulation of oestrogen receptor subtypes and progesterone receptor isoforms in ruminants are reported. The role of steroid receptors in target tissues (with emphasis on the uterus and pituitary gland) during different physiological events is addressed in an attempt to clarify oestrogen and progesterone actions in different developmental and reproductive stages: prepubertal period, oestrous cycle, pregnancy, post-partum period and seasonal anoestrus. The present review shows how the distinct reproductive stages are accompanied by dramatic changes in uterine receptor expression. The role of oestrogen and progesterone receptors in the molecular mechanism responsible for premature luteolysis that results in subnormal luteal function is discussed. Finally, the effect of nutrition on sex steroid receptor expression and the involvement on reproductive performance is reported.

Estrogen is not directly required for oocyte developmental competence

Oocyte maturation and ovulation require a coordinated interaction between gonadotrophs, steroid hormones, and growth factors. The extent to which estrogen is required in this process, however, remains unclear. To better understand the role of estrogen in maintaining developmental competence of mammalian oocytes, we studied the Aromatase knockout (ArKO) mouse, which has been genetically engineered to be incapable of synthesizing endogenous estrogen. Previous studies have established that ArKO female mice are anovulatory with ovaries that progressively degenerate, developing hemorrhagic cystic follicles. In young ArKO females, however, apparently healthy follicles and oocytes have been observed. We investigated if these oocytes could be induced to ovulate, then mature, fertilize, and develop in vitro. Following a standard superovulation protocol, ArKO oocytes did not ovulate. When recovered manually from the ovary, however, ArKO oocytes successfully progressed through in vitro maturation, fertilization, and development to the blastocyst stage at the same rate as wild-type and heterozygote littermates. Therefore, it appears that estrogen is not required for the production and growth of oocytes capable of maturation and complete preimplantation development but is required for continued follicle growth and feedback regulation of ovulation.

Physiopathological aspects of corpus luteum defect in infertile patients with mild/minimal endometriosis

PURPOSE

We describe a physiopathological model to the luteal insufficiency of infertile patients with mild/minimal endometriosis with normal hormone measurements in the early follicular phase.

METHODS

We designed a case-control study with 24 patients, 14 fertile with in-phase endometrium (control group) and 10 infertile with mild/minimal endometriosis and luteal insufficiency (study group). The histologic dating of endometrium was performed during cycle days 23-25 and serum TSH, FSH, LH, prolactin, and estradiol levels were measured during the early follicular phase (cycle day 3). Progesterone serum levels were measured in three different occasions during the luteal phase.

RESULTS

Patients with out-of-phase endometrium have lower estradiol levels (P = 0.031) and decreased progesterone secretion (P = 0.012) during the late luteal phase. Serum prolactin, TSH, FSH, and LH levels were similar between the groups (P > 0.05).

CONCLUSIONS

The physiopathology of luteal phase defect in infertile patients with mild/minimal endometriosis is associated with a small and large luteal cells dysfunction, characterized by abnormal follicular phase (lower estradiol serum levels) and lower progesterone LH-dependent secretion.

Steroids as local regulators of ovarian activity in domestic animals

The presented overview gives clear evidence for steroids as local regulators of follicular and luteal activity. In the follicle, estrogen receptor-alpha (ERalpha) and ERbeta expression are demonstrated in cow, ewe and pig. Besides species specific effects in general, there is evidence that estradiol-17beta (E(2)) exerts a dose-dependent inhibition on the secretion of progesterone (P(4)) by both theca interna cells (TI) and granulosa cells (GC). GC enhance the ability of the TI to produce androstendione by supplying them with progestin precursor. Androgen produced by TI enhances the ability of the GC to make E(2), and high concentrations of E(2) in the preovulatory follicle inhibit 3beta-HSD in both TI and GC and thus, may promote the use of the pathway Delta(5) for TI androgen production. The authors suggest that E(2) acts within the follicle to exert positive feedback on androgen and E(2) production, and exerts mitotic and anti-atretic or anti-apoptotic effects on follicular cells. Parts of the E(2)-mediated local action are regulated by stimulating effects on hormone receptors (LH, FSH, oxytocin). Gap junctions permit transfer of nutrients and cytokines to and from the avascular GC and oocyte, and formation is stimulated by estrogens. In bovine corpus luteum (CL) there is evidence that P(4) may directly regulate the production of P(4), oxytocin and prostaglandins (PGs) in a cycle dependent fashion. In most of domestic animal species, there is clear evidence for CL production of E(2) with clear stimulatory and luteotropic effects on P(4), and an intraluteal circuit that involves paracrine effects of E(2), oxytocin and PGF(2alpha) (especially in pigs). In contrast, there are species (ruminants, mares) in which the evidence for important local effects of E(2) is less clear, although expression of ERalpha, ERbeta and progesterone receptor (PR) is documented. Progesterone is very important for the regulation of CL lifetime by effects on the endometrium and release of the luteolytic signal PGF(2alpha). In conclusion, steroids as local regulators of ovarian activity are now documented and may stimulate further research in this field.

Eight-hydroxy-2'-deoxyguanosine in granulosa cells is correlated with the quality of oocytes and embryos in an in vitro fertilization-embryo transfer program

OBJECTIVE

To determine the effects of oxidative stress on the quality of oocytes and embryos, 8-hydroxy-2'-deoxyguanosine (8-OHdG) in granulosa cells was quantitatively studied during an in vitro fertilization and embryo transfer (IVF-ET) program.

DESIGN

Immunocytochemical staining of 8-OHdG in granulosa cells was quantitatively estimated using a charge-coupled device camera and analyzed using the National Institute of Health Image (NIH Image) freeware on a computer .

SETTING

Obstetrics and gynecology department in a university hospital.

PATIENT(S)

Ninety-six infertile couples undergoing IVF-ET treatment and intracytoplasmic sperm injection (IVF, n = 72; intracytoplasmic sperm injection, n = 24).

INTERVENTION(S)

Oocytes, granulosa cells, and follicular fluids were collected 35-36 hours after the administration of hCG.

MAIN OUTCOME MEASURE(S)

8-OHdG indices were obtained for mural [8-OHdG index (m)] and cumulus [8-OHdG index (c)] granulosa cells.

RESULT(S)

A negative correlation between the fertilization rate and both 8-OHdG indices (c and m) was found. The rate of production of good embryos also showed a negative correlation with the 8-OHdG index (m) and the 8-OHdG index (c). Negative correlations between the 8-OHdG index (c) and E2 levels in follicular fluid were observed. Endometriosis patients showed a higher 8-OHdG index (c) than did patients with other infertility causes, such as tubal, male factor, and unknown.

CONCLUSION(S)

Oxidative stress in granulosa cells lowered fertilization rates and subsequently led to a decrease in the quality of embryos. The quality of oocytes for endometriosis patients was impaired by the presence of 8-OHdG. This might be one causative factor in infertility in endometriosis patients.

Steroid hormonal regulation of proliferative, p53 tumor suppressor, and apoptotic responses of sheep ovarian surface epithelial cells

Ovarian surface epithelial cells have been implicated in the genesis of common ovarian cancers. The integrity of DNA of ovarian surface epithelial cells contiguous with the ovulatory stigma becomes compromised during the rupture process; most cells degenerate by apoptosis, however some, bearing sublethal lesions, persist along the margins of ovulated follicles. Clonal expansion of a genetically-damaged surface epithelial cell (i.e. with unrepaired DNA, but not committed to death) can presumably give rise to ovarian carcinoma. It was hypothesized that estradiol and progesterone regulate ovarian surface epithelial cell-cycle dynamics associated with folliculo-luteal transitions and ovulatory wound repair/remodeling. Progesterone up-regulated the tumor suppressor p53 and inhibited baseline and estradiol-stimulated proliferation of cultured sheep ovarian surface epithelial cells. Anti/mitotic responses to steroid hormones were transcriptionally- and receptor-dependent. Rates of apoptosis (DNA fragmentation) were unaffected by progesterone. High concentrations of estradiol, via a nongenomic (perhaps antioxidant) mechanism, suppressed basal and H(2)O(2)-induced apoptosis. We suggest that, progesterone serves to inhibit proliferation of ovarian surface epithelial cells throughout the luteal phase--providing the time (growth arrest) required to correct any metabolic disturbances to DNA that are perpetrated as an inevitable by-product of the ovulatory process. With luteolysis and dominance of an estrogenic preovulatory follicle the ovarian surface epithelium is then regenerated. Thus, it is conceivable that perturbations to the steroid hormonal milieu of ovarian cycles could be a predisposing factor for cancerous transformation of an ovarian surface epithelial cell.

Circulating gonadotrophins and follicular dynamics in anestrous ewes after treatment with estradiol-17beta

Plasma FSH, LH, estradiol (E2) and progesterone (P4) profiles and patterns of follicular growth and regression by ultrasonography were determined after E2 treatment (1 microg/kg) in anestrous ewes. Fifteen ewes were treated with one (group I, n=7) or two (group II, n=4) i.m. injections of E2 with a 24h interval, or two oil injections with a 24h interval (group C, n=4). Blood samples for E2, P4, FSH and LH determinations were collected daily 4 days before the initiation of the treatment (day 0), when bleeding increased to every 2h starting 2h before treatment until 56h after the first injection and from then on every 6h until day 8, and twice per day till the end of the experiment (day 9). During the experimental period (days -4 to 9), transrectal ultrasonic examinations were carried out daily using a 7.5 MHz linear array probe. Number and size of follicles > or =3mm in diameter were recorded. No estrous was detected before, during or after treatment. LH and FSH surges were observed 10-18h after the first E2 injection. The second E2 injection stimulated another release of LH but no surges. E2 inhibited FSH levels before the surge and the second E2 injection induced a longer inhibition. No ovulation was detected by ultrasonography during the experimental period and P4 levels remained low (<0.7 nmol/l) before, during and after the treatment in all ewes. There was an effect of E2 treatment on the diameter of the largest follicle, a decrease could be observed 3 days after the first injection in both ewes of groups I and II. The E2-treated groups had a higher frequency of ewes showing wave emergence on day 3 (day 1.5+/-1,2.4+/-0.4 and 2.5+/-0.5 for control, groups I and II). LH and FSH surges were observed after E2 treatment, but were not able to provoke ovulation neither luteinization. In contrast, the treatment was associated with the regression of the largest follicle and with emergence of a new follicular wave on day 3.

Estrogenic upregulation of DNA polymerase beta in oocytes of preovulatory ovine follicles

The basic premise of this investigation was that local hormonal control of stockpiling of the base excision repair polymerase (poly) beta within oocytes of preovulatory follicles occurs as a function of cytoplasmic maturation. There was an increase in immunoreactive poly beta in sectioned oocytes of preovulatory ovine follicles during a 12-36-hour interval following the onset of prostaglandin (PG) F2alpha-induced (Day 14 of the estrous cycle) luteal regression; this response was not observed in subordinate (nonovulatory) follicles. Accumulation of poly beta in oocytes at 36 hr after PGF2alpha was negated by treatment of ewes at 12 hr with the aromatase inhibitor Arimidex or an ovulatory dose of GnRH (which, via surge gonadotropin stimulation, acutely downregulates the proestrous rise in follicular estrogen biosynthesis). Estradiol-17beta stimulated poly beta expression (transcriptional control) in oocytes of explanted (12 hr after PGF2alpha) follicles (24-hour incubation). We suggest that a critical period of estrogen amplification in the preovulatory follicle underscores the capacity of its oocyte to efficiently repair DNA and therefore reconcile spontaneous infidelities in genomic integrity that inevitably occur during preimplantation embryogenesis.

Effects of low O2 and ageing on spindles and chromosomes in mouse oocytes from pre-antral follicle culture

To assess their quality, spindles were analysed in mouse oocytes from pre-antral follicle culture. High or low oxygen tension was present during the last 16 or 20 h post human chorionic gonadotrophin (HCG)/epidermal growth factor (EGF) addition. Most oocytes from pre-antral follicle culture possessed typical anastral spindles with flat poles resembling those of ovulated, in-vivo-matured oocytes of sexually mature mice, while denuded oocytes in-vitro matured to metaphase II (MII) formed significantly longer, slender spindles with pointed, narrow poles. Spindles in oocytes from follicle culture were only slightly shorter and less compact at the equator as compared with those of oocytes matured in vivo. Chromosomes were well aligned at the equator in MII oocytes obtained from follicle culture with high oxygen. Maturation rate was significantly reduced by lowering oxygen tension to 5% O2. Prolonged culture and the presence of only 5% O2 dramatically increased the percentage of MII oocytes with unaligned chromosomes. These observations indicate that sufficient oxygen supply and time of retrieval after initiation of resumption of maturation by HCG as well as the microenvironment and cell-cell interactions between oocytes and their somatic compartment are critical in affecting the oocyte's capacity to mature to MII, to form a functional spindle, and to align chromosomes correctly.