Follicle Selection in Mares as a Model for Illustrating the Many Hormonal and Biochemical Interactions That Drive a Single Physiological Mechanism.

The mechanism for selection of the future dominant or ovulatory follicle in mares involves a relatively abrupt separation in growth rates between the future dominant follicle and several subordinate follicles and is termed diameter deviation. The event is used to illustrate that a coordinated complex of many follicular, hormonal, and biochemical factors interact and interbalance during a single physiological mechanism. For example, a positive effect of follicle stimulating hormone (FSH) on development of all follicles during the growing phase can later involve a positive effect of luteinizing hormone (LH) but apparently only on the future dominant follicle. In turn, the developing and future dominant follicle produces estradiol which at appropriate times and degrees reduces FSH concentrations to accommodate follicle functions at certain levels of FSH. Meanwhile, the estradiol prevents LH from increasing from a useful to an adverse concentration. These interactions enmesh with the production and roles of other factors (e.g., inhibin, insulin-like growth factor) during follicle selection. The wide array of morphological, hormonal, and biochemical activities occur in harmony even when in the same tissue and often at the same time.

Morphology and Biochemistry of Ovulation.

The process of ovulation involves multiple and iterrelated genetic, biochemical, and morphological events: cessation of the proliferation of granulosa cells, resumption of oocyte meiosis, expansion of cumulus cell-oocyte complexes, digestion of the follicle wall, and extrusion of the metaphase-II oocyte. The present narrative review examines these interrelated steps in detail. The combined or isolated roles of the follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are highlighted. Genes indiced by the FSH genes are relevant in the cumulus expansion, and LH-induced genes are critical for the resumption of meiosis and digestion of the follicle wall. A non-human model for follicle-wall digestion and oocyte release was provided.

O processo de ovulação envolve modificações genéticas, bioquímicas e morfológicas múltiplas e interrelacionadas: suspensão da proliferação das células da granulosa, reinício da meiose do oócito, expansão das células do complexo cumulus-oócito, digestão da parede folicular, e extrusão do oócito. Esta revisão narrativa examina em detalhes cada um desses eventos e os principais genes e proteínas envolvidos. Mais importante, a ação combinada ou isolada do hormônio folículo-estimulante (HFE) e do hormônio luteinizante (HL) é destacada. Detalha-se o papel do HFE na expansão do cumulus e do HL na digestão da parede folicular, permitindo a extrusão do oócito na superfície ovariana. Proveu-se um modelo não humano para explicar a digestão da parede folicular.

Morphology and Biochemistry of Ovulation Morfologia e bioquímica da ovulação

Abstract The process of ovulation involves multiple and iterrelated genetic, biochemical, and morphological events: cessation of the proliferation of granulosa cells, resumption of oocyte meiosis, expansion of cumulus cell-oocyte complexes, digestion of the follicle wall, and extrusion of the metaphase-II oocyte. The present narrative review examines these interrelated steps in detail. The combined or isolated roles of the folliclestimulating hormone (FSH) and luteinizing hormone (LH) are highlighted. Genes indiced by the FSH genes are relevant in the cumulus expansion, and LH-induced genes are critical for the resumption ofmeiosis and digestion of the follicle wall. A nonhuman model for follicle-wall digestion and oocyte release was provided.

Resumo O processo de ovulação envolve modificações genéticas, bioquímicas e morfológicas múltiplas e interrelacionadas: suspensão da proliferação das células da granulosa, reinício da meiose do oócito, expansão das células do complexo cumulus-oócito, digestão da parede folicular, e extrusão do oócito. Esta revisão narrativa examina em detalhes cada um desses eventos e os principais genes e proteínas envolvidos. Mais importante, a ação combinada ou isolada do hormônio folículo-estimulante (HFE) e do hormônio luteinizante (HL) é destacada. Detalha-se o papel do HFE na expansão do cumulus e do HL na digestão da parede folicular, permitindo a extrusão do oócito na superfície ovariana. Proveu-se um modelo não humano para explicar a digestão da parede folicular.

Genetic Regulation of Physiological Reproductive Lifespan and Female Fertility.

There is substantial genetic variation for common traits associated with reproductive lifespan and for common diseases influencing female fertility. Progress in high-throughput sequencing and genome-wide association studies (GWAS) have transformed our understanding of common genetic risk factors for complex traits and diseases influencing reproductive lifespan and fertility. The data emerging from GWAS demonstrate the utility of genetics to explain epidemiological observations, revealing shared biological pathways linking puberty timing, fertility, reproductive ageing and health outcomes. The observations also identify unique genetic risk factors specific to different reproductive diseases impacting on female fertility. Sequencing in patients with primary ovarian insufficiency (POI) have identified mutations in a large number of genes while GWAS have revealed shared genetic risk factors for POI and ovarian ageing. Studies on age at menopause implicate DNA damage/repair genes with implications for follicle health and ageing. In addition to the discovery of individual genes and pathways, the increasingly powerful studies on common genetic risk factors help interpret the underlying relationships and direction of causation in the regulation of reproductive lifespan, fertility and related traits.

Neurokinin 3 receptor-selective agonist, senktide, decreases core temperature in Japanese Black cattle.

Heat stress disrupts reproductive function in cattle. In summer, high ambient temperature and humidity elevate core body temperature, which is considered to be detrimental to reproductive abilities in cattle. Neurokinin B (NKB) is a factor that generates pulsatile GnRH and subsequent LH secretion in mammals. Recent studies have reported that NKB-neurokinin 3 receptor (NK3R) signaling is associated with heat-defense responses in rodents. The present study aimed to clarify the role of NKB-NK3R signaling in thermoregulation in cattle. We examined the effects of an NK3R-selective agonist, senktide, on vaginal temperature as an indicator of core body temperature in winter and summer. In both seasons, continuous infusion of senktide for 4 h immediately decreased vaginal temperature, and the mean temperature change in the senktide-treated group was significantly lower than that of both vehicle- and GnRH-treated groups. Administration of GnRH induced LH elevation, but there was no significant difference in vaginal temperature change between GnRH- and vehicle-treated groups. Moreover, we investigated the effects of senktide on ovarian temperature. Senktide treatment seemed to suppress the increase in ovarian temperature from 2 h after the beginning of administration, although the difference between groups was not statistically significant. Taken together, these results suggest that senktide infusion caused a decline in the vaginal temperature of cattle, in both winter and summer seasons, and this effect was not due to the gonadotropin-releasing action of senktide. These findings provide new therapeutic options for senktide to support both heat-defense responses and GnRH/LH pulse generation.

Synergistic effect between LH and estrogen in the acceleration of cumulus expansion via GPR30 and EGFR pathways.

The estrogen membrane receptor GPR30 (also known as G-protein coupled receptor 30) has recently been shown to be involved in the regulation of oocyte maturation and cumulus expansion. However, whether GPR30 expression is regulated by gonadotropin stimulation and how it participates in the regulation of the maturation process is still not clear. In this study, we explored the mechanism underlying the synergy between luteinizing hormone and 17ß-estradiol (17ß-E2) to improve the epidermal growth factor (EGF) response in cumulus oocyte complexes (COCs) during oocyte maturation in mice. The expression and distribution of GPR30, EGFR, and EGF-like growth factors were examined by real-time quantitative PCR, western blot, and immunofluorescence staining. Lyso-Tracker Red labeling was performed to detect the lysosomal activity in follicle granular cells (FGCs). Cumulus expansion of COCs was evaluated after in vitro maturation for 16 h. We found that EGF-like growth factors transmit LH signals to increase GRP30 levels by inhibiting protein degradation in lysosomes. Meanwhile, 17ß-E2 stimulates the GPR30 signaling pathway to increase EGF receptor levels, enhancing the response ability of EGF signaling in COCs and thus promoting cumulus expansion. In conclusion, our study reveals the synergistic mechanism between LH and estrogen in the regulation of cumulus expansion during oocyte maturation process.

LH-induced Transcriptional Regulation of Klf4 Expression in Granulosa Cells Occurs via the cAMP/PKA Pathway and Requires a Putative Sp1 Binding Site.

Krüppel-like factor 4 (Klf4) plays an important role in the transition from proliferation to differentiation in a wide variety of cells. Previous studies demonstrated its critical role in the luteal transition of preovulatory granulosa cells (GCs). This study used cultured rat preovulatory GCs to investigate the mechanism by which luteinizing hormone (LH) regulates Klf4 gene expression. Klf4 mRNA and protein were rapidly and transiently induced by LH treatment, reaching peak levels after 45 min and declining to basal levels by 3 h. Pretreatment with the protein synthesis inhibitor cycloheximide had no effect on LH-stimulated Klf4 expression, indicating that Klf4 is an immediate early gene in response to LH. To investigate the signaling pathway involved in LH-induced Klf4 regulation, the protein kinase A (PKA) and protein kinase C (PKC) pathways were evaluated. A-kinase agonists, but not a C-kinase agonist, mimicked LH in inducing Klf4 transcription. In addition, specific inhibitors of A-kinase abolished the stimulatory effect of LH on Klf4 expression. Truncation of a Klf4 expression construct to -715 bp (pKlf4-715/luc) had no effect on transcriptional activity, whereas deletion to -402 bp (pKlf4-402/luc) dramatically reduced it. ChIP analysis revealed in vivo binding of endogenous Sp1 to the -715/-500 bp region and maximal transcriptional responsiveness to LH required the Sp1 binding element at -698/-688 bp, which is highly conserved in mice, rats, and humans. These findings demonstrate that Klf4 is activated by LH via the cAMP/PKA pathway and a putative Sp1 binding element at -698/-688 bp is indispensable for activation and suggest that Klf4 could be a target for strategies for treating luteal phase insufficiency induced by an aberrant response to the LH surge.

The role of gonadotrophins in gonocyte transformation during minipuberty.

PURPOSE: Postnatal surge of gonadotrophins, Luteinizing hormone (LH) and Follicle-Stimulating hormone (FSH) known as minipuberty, is critical for gonocyte maturation into spermatogonial stem cells (SSC) in the testis. Gonadotrophins are essential for optimum fertility in men, but very little is known how they regulate germ cells during minipuberty. This study examined whether gonadotrophins play a role on gonocyte transformation in vivo. METHODS: Testes from hypogonadal (hpg) mice and their wild type (WT) littermates (n = 6/group) were weighed, and processed in paraffin at postnatal days (D) 0, 3, 6 and 9. Mouse VASA homologue (germ cell marker), anti-Müllerian hormone (Sertoli cell marker) antibodies and DAPI (nuclei marker) were used for immunofluorescence followed by confocal imaging. Germ cells on or off basement membrane (BM) and Sertoli cells/tubule were counted using Image J and analyzed with GraphPad. RESULTS: Comparing to WT littermates, there were significantly fewer germ cells on BM/tubule (p < 0.05) in D9 hpg mice, whereas there was no significant difference for germ cells off BM/tubule and Sertoli cells/tubule between littermates. However, testicular weight was significantly reduced in D3-D9 hpg mice comparing to WT littermates. CONCLUSION: Gonadotrophin deficiency reduced D9 germ cells on BM indicating impaired gonocyte transformation into SSC. This suggests that gonadotrophins may mediate gonocyte transformation during minipuberty.

Mechanistic model of hormonal contraception.

Contraceptive drugs intended for family planning are used by the majority of married or in-union women in almost all regions of the world. The two most prevalent types of hormones associated with contraception are synthetic estrogens and progestins. Hormonal based contraceptives contain a dose of a synthetic progesterone (progestin) or a combination of a progestin and a synthetic estrogen. In this study we use mathematical modeling to understand better how these contraceptive paradigms prevent ovulation, special focus is on understanding how changes in dose impact hormonal cycling. To explain this phenomenon, we added two autocrine mechanisms essential to achieve contraception within our previous menstrual cycle models. This new model predicts mean daily blood concentrations of key hormones during a contraceptive state achieved by administering progestins, synthetic estrogens, or a combined treatment. Model outputs are compared with data from two clinical trials: one for a progestin only treatment and one for a combined hormonal treatment. Results show that contraception can be achieved with synthetic estrogen, with progestin, and by combining the two hormones. An advantage of the combined treatment is that a contraceptive state can be obtained at a lower dose of each hormone. The model studied here is qualitative in nature, but can be coupled with a pharmacokinetic/pharamacodynamic (PKPD) model providing the ability to fit exogenous inputs to specific bioavailability and affinity. A model of this type may allow insight into a specific drug's effects, which has potential to be useful in the pre-clinical trial stage identifying the lowest dose required to achieve contraception.

Metabolic regulation of kisspeptin - the link between energy balance and reproduction.

Hypothalamic kisspeptin neurons serve as the nodal regulatory centre of reproductive function. These neurons are subjected to a plethora of regulatory factors that ultimately affect the release of kisspeptin, which modulates gonadotropin-releasing hormone (GnRH) release from GnRH neurons to control the reproductive axis. The presence of sufficient energy reserves is critical to achieve successful reproduction. Consequently, metabolic factors impose a very tight control over kisspeptin synthesis and release. This Review offers a synoptic overview of the different steps in which kisspeptin neurons are subjected to metabolic regulation, from early developmental stages to adulthood. We cover an ample array of known mechanisms that underlie the metabolic regulation of KISS1 expression and kisspeptin release. Furthermore, the novel role of kisspeptin neurons as active players within the neuronal circuits that govern energy balance is discussed, offering evidence of a bidirectional role of these neurons as a nexus between metabolism and reproduction.

Gonadotrophins modulate cell death-related genes expression in human endometrium.

Background Gonadotrophins exert their functions by binding follicle-stimulating hormone receptor (FSHR) or luteinizing hormone and human chorionic gonadotropin receptor (LHCGR) present on endometrium. Within ovaries, FSH induces autophagy and apoptosis of granulosa cells leading to atresia of non-growing follicles, whereas hCG and LH have anti-apoptotic functions. Endometrial cells express functioning gonadotrophin receptors. The objective of this study was to analyze the effect of gonadotrophins on physiology and endometrial cells survival. Materials and methods Collected endometria were incubated for 48 or 72 h with 100 ng/mL of recombinant human FSH (rhFSH), recombinant human LH (rhLH) or highly purified hCG (HPhCG) alone or combined. Controls omitted gonadotrophins. The effect of gonadotrophins on cytochrome P450 family 11 subfamily A polypeptide 1 (CYP11A1), hypoxia inducible factor 1α (HIF1A), and cell-death-related genes expression was evaluated by reverse transcription quantitative polymerase chain reaction (RT-qPCR). Immunohistochemistry for microtubule-associated proteins 1A/1B light chain 3B (MAP1LC3B) and apoptotic protease activating factor 1 (APAF-1) was performed. Results Gonadotrophins are able to modulate the endometrial cells survival. FSH induced autophagy and apoptosis by increasing the relative expression of MAP1LC3B and FAS receptor. In FSH-treated samples, expression of apoptosis marker APAF-1 was detected and co-localized on autophagic cells. hCG and LH does not modulate the expression of cell-death-related genes while the up-regulation of pro-proliferative epiregulin gene was observed. When combined with FSH, hCG and LH prevent autophagy and apoptosis FSH-induced. Conclusions Different gonadotrophins specifically affect endometrial cells viability differently: FSH promotes autophagy and apoptosis while LH and hCG alone or combined with rhFSH does not.

The role of FSH and LH in prostate cancer and cardiometabolic comorbidities.

INTRODUCTION: In this article we advance a potential explanation for the incidence of cardiovascular (CV) and cardiometabolic risk in patients undergoing androgen deprivation therapy (ADT) for prostate cancer. Our conceptual model involves the differential impact of gonadotropin-releasing hormone (GnRH) agonists and antagonists on the follicle-stimulating hormone (FSH) system. MATERIALS AND METHODS: Authors searched online repositories and meeting abstract databases for relevant materials. RESULTS: Mounting evidence links FSH with development and progression of prostate cancer. What is also becoming clear is that the differential effects of GnRH agonists and antagonists on FSH may at least partially explain the differing effects these agents have on CV risk during ADT. While GnRH antagonists immediately suppress FSH, GnRH agonists provoke a transient surge in FSH that may contribute to the higher CV risk observed with these agents. Additionally, recent studies suggest that GnRH antagonists may significantly reduce CV risk compared to GnRH agonists, particularly in men with pre-existing CV disease. CONCLUSIONS: Patients with cardiovascular risk factors who require ADT may benefit from the better control of FSH provided by GnRH antagonists. ADT itself appears to heighten CV risk, and data suggest that FSH may at least partly drive this risk by promoting inflammation, atherosclerosis, insulin resistance, adipocyte rearrangement and plaque instability.

Neuronal networks that regulate gonadotropin-releasing hormone/luteinizing hormone secretion during undernutrition: evidence from sheep.

Gonadotropin-releasing hormone (GnRH) neurons are the final common conduit from the central nervous system in the reproductive axis, controlling luteinizing hormone (LH) secretion from the gonadotropes of the anterior pituitary. Although it is generally accepted that undernutrition inhibits GnRH/LH secretion, the central mechanisms that underlie the link between energy balance and reproduction remain to be fully elucidated. Sheep have been a longstanding and invaluable animal model for examination of the nutritional regulation of GnRH/LH secretion, given their ability to serve a biomedical and agricultural purpose. In this review, we summarize work that has used the ovine model to examine the central mechanisms whereby undernutrition regulates GnRH/LH secretion. Specifically, we focus our attention to the arcuate nucleus of the hypothalamus and on neurons that express kisspeptin, neurokinin B, dynorphin, proopiomelanocortin, and neuropeptide y/agouti-related peptide (NPY/AgRP). We examine their roles in mediating the effects of leptin and insulin and their effects on LH during undernutrition, as well as their regulation under conditions of undernutrition. This review will also highlight the interactions between the aforementioned neuronal networks themselves, which may be important for our understanding of the roles each play in relaying information regarding energy status during times of undernutrition to ultimately regulate GnRH/LH secretion.

[Effects of cetrorelix versus ganirelix in gonadotropin-releasing hormone antagonist cycles for preventing premature luteinizing hormone surges and on clinical outcomes of IVF-ET cycles].

OBJECTIVE: To compare the effects of cetrorelix and ganirelix in gonadotropin-releasing hormone antagonist (GnRH-ant) cycles for preventing premature luteinizing hormone (LH) surges and on clinical outcomes of IVF-ET cycles. METHODS: We retrospectively analyzed 2572 GnRH-ant cycles of in vitro fertilization and embryo transfer from January, 2013 to December, 2016, including 1368 cycles with cetrorelix treatment and 1204 cycles with ganirelix treatment. The baseline characteristics of the patients and the clinical outcomes of the two groups were compared. RESULTS: Compared with those receiving ganirelix treatment, the patients with cetrorelix treatment had a significantly younger age (33.10 vs 33.89 years, P < 0.001) and a lower body mass index (21.57 vs 21.84 kg/m2, P=0.024). After adjustment for age and body mass index of the patients, no significant differences were found between the two groups in the levels of follicle-stimulating hormone (FSH), LH, estradiol (E2), progesterone (P) levels either at the baseline or on the day of hCG triggering, or in the number of oocytes retrieved (P > 0.05). The two groups also had comparable percentages of patients with LH > 10 U/L on the day of hCG triggering (3.7% vs 3.2%) and similar spontaneous ovulation rate (0.6% vs 0.5%), clinical pregnancy rate (47.7% vs 45.9%) and live birth rate (37.5% vs 33.6%) following fresh embryo transfer (P > 0.05). The incidence of moderate to severe ovarian hyperstimulation syndrome, however, was significantly higher in ganirelix group than in cetrorelix group (0.7% vs 0.1%, P=0.006). CONCLUSIONS: Cetrorelix and ganirelix can achieve comparable effects for preventing premature LH surges and can achieve similar clinical outcomes of GnRH-ant cycles, but ganirelix is associated with a significantly higher incidence of moderate to severe ovarian hyperstimulation syndrome.

The Origin of GnRH Pulse Generation: An Integrative Mathematical-Experimental Approach.

Fertility critically depends on the gonadotropin-releasing hormone (GnRH) pulse generator, a neural construct comprised of hypothalamic neurons coexpressing kisspeptin, neurokoinin-B and dynorphin. Here, using mathematical modeling and in vivo optogenetics we reveal for the first time how this neural construct initiates and sustains the appropriate ultradian frequency essential for reproduction. Prompted by mathematical modeling, we show experimentally using female estrous mice that robust pulsatile release of luteinizing hormone, a proxy for GnRH, emerges abruptly as we increase the basal activity of the neuronal network using continuous low-frequency optogenetic stimulation. Further increase in basal activity markedly increases pulse frequency and eventually leads to pulse termination. Additional model predictions that pulsatile dynamics emerge from nonlinear positive and negative feedback interactions mediated through neurokinin-B and dynorphin signaling respectively are confirmed neuropharmacologically. Our results shed light on the long-elusive GnRH pulse generator offering new horizons for reproductive health and wellbeing.SIGNIFICANCE STATEMENT The gonadotropin-releasing hormone (GnRH) pulse generator controls the pulsatile secretion of the gonadotropic hormones LH and FSH and is critical for fertility. The hypothalamic arcuate kisspeptin neurons are thought to represent the GnRH pulse generator, since their oscillatory activity is coincident with LH pulses in the blood; a proxy for GnRH pulses. However, the mechanisms underlying GnRH pulse generation remain elusive. We developed a mathematical model of the kisspeptin neuronal network and confirmed its predictions experimentally, showing how LH secretion is frequency-modulated as we increase the basal activity of the arcuate kisspeptin neurons in vivo using continuous optogenetic stimulation. Our model provides a quantitative framework for understanding the reproductive neuroendocrine system and opens new horizons for fertility regulation.

Circadian Function in Multiple Cell Types Is Necessary for Proper Timing of the Preovulatory LH Surge.

The timing of the preovulatory surge of luteinizing hormone (LH), which occurs on the evening of proestrus in female mice, is determined by the circadian system. The identity of cells that control the phase of the LH surge is unclear: evidence supports a role of arginine vasopressin (AVP) cells of the suprachiasmatic nucleus (SCN), but it is not known whether vasopressinergic neurons are necessary or sufficient to account for circadian control of ovulation. Among other cell types, evidence also suggests important roles of circadian function of kisspeptin cells of the anteroventral periventricular nucleus (AvPV) and gonadotropin-releasing hormone (GnRH) neurons of the preoptic area (POA), whose discharge is immediately responsible for the discharge of LH from the anterior pituitary. The present studies used an ovariectomized, estradiol-treated preparation to determine critical cell types whose clock function is critical to the timing of LH secretion. As expected, the LH surge occurred at or shortly after ZT12 in control mice. In further confirmation of circadian control, the surge was advanced by 2 h in tau mutant animals. The timing of the surge was altered to varying degrees by conditional deletion of Bmal1 in AVPCre, KissCreBAC, and GnRHCreBAC mice. Excision of the mutant Cnsk1e (tau) allele in AVP neurons resulted in a reversion of the surge to the ZT12. Conditional deletion of Bmal1 in Kiss1 or GnRH neurons had no noticeable effect on locomotor rhythms, but targeting of AVP neurons produced variable effects on circadian period that did not always correspond to changes in the phase of LH secretion. The results indicate that circadian function in multiple cell types is necessary for proper timing of the LH surge.

The Impact of Morphine on Reproductive Activity in Male Rats Is Regulated by Rf-Amid-Related Peptide-3 and Substance P Adjusting Hypothalamic Kisspeptin Expression.

Obviously, opiates (e.g., morphine) are associated with the suppression and dysfunction of reproductive axis. It has been reported that substance P (SP) and RF-amid-related peptide-3 (RFRP-3) can exhibit anti-opioid effects in some regions of the nervous system. Moreover, SP and RFRP-3 are deemed as neuropeptides which exert modulatory and regulatory impacts on the function of the reproductive axis. The precise interactions of morphine with SP or RFRP-3 on the parameters of the reproductive activity, however, are not fully known. The present study was aimed to determine the impacts of the interaction of morphine either with SP or RFRP-3 on the hormonal and behavioral parameters of reproductive activity in male rats. In addition, it was aimed at determining whether the effects of these interactions rely on kisspeptin/G protein coupled receptor 54 (GPR54) pathway as the main upstream pulse generator and the mediator of the function of many inputs of gonadotropin-releasing hormone (GnRH)/luteinizing hormone (LH) system or not. Altogether, the resulted data from the sexual behavior tests, radioimmunoassay of LH/testosterone, and real-time quantitative PCR for the assessment of the expression of hypothalamic Kiss1, Gpr54, and Gnrh1 genes following concomitant administration of morphine with SP or RFRP-3 revealed that the suppressing effects of morphine on the parameters of reproductive axis activity can be affected by the administration of either RFRP-3 or SP. It is advocated that SP and RFRP-3, by the modulation of the expression of hypothalamic Kiss1, can possibly antagonize the effects of morphine on GnRH/LH system and sexual behavior.

Steroidogenic acute regulatory protein and luteinizing hormone are required for normal ovarian steroidogenesis and oocyte maturation in zebrafish†.

In recent studies, luteinizing hormone (LH) was reported to play important roles in oocyte maturation. However, the mechanism by which LH signaling, especially regarding the steroidogenesis process, affects oocyte maturation has not been clarified. In this study, zebrafish models with a functional deficiency in luteinizing hormone beta (Lhb) or steroidogenic acute regulatory protein (Star), an enzyme that promotes the transport of cholesterol into the inner mitochondrial membrane for maturation-induced hormone (MIH) production, were generated using transcription activator-like effector nucleases (TALENs). Similar phenotypes of the maturation-arrested oocytes in both female mutants have been observed. The levels of MIH in the oocytes of the female mutants were clearly decreased in both the lhb and star knockout zebrafish. The expression of star was dramatically down-regulated in the lhb mutant follicles and was clearly promoted by forskolin and hCG in vitro. Furthermore, treatment with the MIH precursors, pregnenolone or progesterone, as well as with MIH itself rescued the maturation-arrested oocyte phenotypes in both lhb and star mutants. The plasma levels of other steroids, including testosterone, estradiol, and cortisol, were not affected in the lhb mutants, while the levels of gonad hormones testosterone and estradiol were significantly increased in the star mutants. The cortisol levels were decreased in the star mutants. Collectively, our results confirm that LH plays important roles in the initiation of MIH synthesis from cholesterol and maintains oocyte maturation in zebrafish, as well as provide evidence that Star might act downstream of LH signaling in steroidogenesis.

Time of copulation during estrus period on estrus duration and LH response in Boer goats.

The objectives of this investigation were to determine the effect of the time of copulation during the estrus period on estrus duration and luteinizing hormone (LH) response in goats. A controlled randomized study with two replicates (first = n = 12; second = n = 24), in which Boer does were divided at each replicate into three groups, was performed. Copulations at the beginning of estrus (two copulas within the first 4 h after estrus; COP-1; n = 12), copulations around the middle of estrus (two copulas around 16 h after estrus; COP-2; n = 12), and noncopulations (only mounts) throughout the estrus period (control group; CON; n = 12) were performed. Estrus duration for CON group was 41.3 ± 8.2 h; for COP-1, it was 34.0 ± 5.3 h, and for COP-2, it was 39.7 ± 6.9 h (P = 0.04). Differences were detected between COP-1 and CON groups (P = 0.01) and between COP-1 and COP-2 groups (P = 0.05) but not between CON and COP-2 groups (P = 0.56). The LH peak time for the CON group was 20.0 ± 8.0 h; for the COP-1 group, it was 13.0 ± 3.6 h, and for the COP-2 group, it was 20.5 ± 5.8 h (P = 0.04). The COP-1 group was different than the COP-2 (P = 0.02) and CON groups (P = 0.03), and no differences were detected between these last two groups (P = 0.87). It was concluded that copulation reduced estrus duration and hastened the LH peak time only when performed during the beginning of estrus.

[The role of EGF-like factor signaling pathway in granulosa cells in regulation of oocyte maturation and development].

The surge of luteinizing hormone (LH) in preovulatory ovarian follicles triggers the resumption of meiosis in oocytes and induces the proliferation of surrounding cumulus granulosa cells. It is believed that LH receptors are expressed in the mural granulosa cells, but not the oocytes and the surrounding cumulus cells, suggesting that the LH signaling is mediated by factors produced by the granulosa cells. However, the mechanism underlying oocyte maturation induced by LH before ovulation has been controversial. Current studies suggest that LH binds on to its receptor on granulosa cells of the follicular wall to promote the production of EGF-like factors, which activate various signaling cascades and induce oocyte maturation and development. Since the in vitro maturation system is difficult to simulate the in vivo physiological environment, in vitro cultured follicles are likely to be de?cient in the EGF-like factors, which could result in the poor developmental competency of in vitro cultured oocytes and restrict their efficient utilization. In this review, we summarize the EGF-like factor signaling system in granulosa cells and its regulation of oocyte maturation and development. It aims to optimize the in vitro maturation culture system of oocytes and increase the EGF-like factor signaling system in cumulus granulosa cells, thereby providing a framework for improving the efficiency on in vitro maturation of oocytes.