PI3-kinase and mitogen-activated protein kinase in cumulus cells mediate EGF-induced meiotic resumption of porcine oocyte

Role of phosphoinositide 3-kinase/ protein kinase B/ phosphatase and tensin homologue (PI3K/AKT/PTEN) pathway inhibitors during in vitro maturation of mammalian oocytes on in vitro embryo production: A systematic review

Modulation of phosphoinositide 3-kinase/protein kinase B/phosphatase and tensin homologue (PI3K/AKT/PTEN) pathway in mammals yields mixed results. A deep understanding of its regulation can be a powerful tool for better in vitro blastocyst production. This systematic review aims to map the evidence of PI3K/AKT/PTEN pathway modulation during in vitro maturation (IVM), to assess its effects on meiosis resumption and nuclear maturation progression of mammalian oocytes, and their impacts on embryo development and quality. A total of 1058 articles were screened in three databases, and 22 articles were included. Fifty-two IVM assessments were identified, among which 11 evaluated blastocyst yield. Three PI3K inhibitors (3-methyladenine, Wortmannin, and LY294002) and one AKT inhibitor (SH6) were investigated. The impact of this pathway modulation on meiosis resumption in swines and murines was not well established, depending on the inhibitor used, concentration, and media supplementation, while in bovines, resumption seems to be independent of PI3K/AKT/PTEN pathway. However, progression to metaphase II (MII) is highly controlled by this pathway on both bovines and swines. Studies that focused on the inhibition reversibility showed that the removal of the modulator produced MII rates similar to the control group. Experiments that aimed to temporarily block meiosis resumption or reduce PI3K activity resulted in blastocyst production equal to or even higher than control groups. Altogether, these data indicate the paramount potential of this pathway as a possible strategy to improve overall in vitro embryo production efficiency, by synchronizing both nuclear and cytoplasmic maturation.

In Vitro Folliculogenesis in Mammalian Models: A Computational Biology Study

In vitro folliculogenesis (ivF) has been proposed as an emerging technology to support follicle growth and oocyte development. It holds a great deal of attraction from preserving human fertility to improving animal reproductive biotechnology. Despite the mice model, where live offspring have been achieved,in medium-sized mammals, ivF has not been validated yet. Thus, the employment of a network theory approach has been proposed for interpreting the large amount of ivF information collected to date in different mammalian models in order to identify the controllers of the in vitro system. The WoS-derived data generated a scale-free network, easily navigable including 641 nodes and 2089 links. A limited number of controllers (7.2%) are responsible for network robustness by preserving it against random damage. The network nodes were stratified in a coherent biological manner on three layers: the input was composed of systemic hormones and somatic-oocyte paracrine factors; the intermediate one recognized mainly key signaling molecules such as PI3K, KL, JAK-STAT, SMAD4, and cAMP; and the output layer molecules were related to functional ivF endpoints such as the FSH receptor and steroidogenesis. Notably, the phenotypes of knock-out mice previously developed for hub.BN indirectly corroborate their biological relevance in early folliculogenesis. Finally, taking advantage of the STRING analysis approach, further controllers belonging to the metabolic axis backbone were identified, such as mTOR/FOXO, FOXO3/SIRT1, and VEGF, which have been poorly considered in ivF to date. Overall, this in silico study identifies new metabolic sensor molecules controlling ivF serving as a basis for designing innovative diagnostic and treatment methods to preserve female fertility.

Signalling pathways and mechanistic cues highlighted by transcriptomic analysis of primordial, primary, and secondary ovarian follicles in domestic cat

In vitro growth (IVG) of dormant primordial ovarian follicles aims to produce mature competent oocytes for assisted reproduction. Success is dependent on optimal in vitro conditions complemented with an understanding of oocyte and ovarian follicle development in vivo. Complete IVG has not been achieved in any other mammalian species besides mice. Furthermore, ovarian folliculogenesis remains sparsely understood overall. Here, gene expression patterns were characterised by RNA-sequencing in primordial (PrF), primary (PF), and secondary (SF) ovarian follicles from Felis catus (domestic cat) ovaries. Two major transitions were investigated: PrF-PF and PF-SF. Transcriptional analysis revealed a higher proportion in gene expression changes during the PrF-PF transition. Key influencing factors during this transition included the interaction between the extracellular matrix (ECM) and matrix metalloproteinase (MMPs) along with nuclear components such as, histone HIST1H1T (H1.6). Conserved signalling factors and expression patterns previously described during mammalian ovarian folliculogenesis were observed. Species-specific features during domestic cat ovarian folliculogenesis were also found. The signalling pathway terms "PI3K-Akt", "transforming growth factor-β receptor", "ErbB", and "HIF-1" from the functional annotation analysis were studied. Some results highlighted mechanistic cues potentially involved in PrF development in the domestic cat. Overall, this study provides an insight into regulatory factors and pathways during preantral ovarian folliculogenesis in domestic cat.

Selective sweep analysis reveals extensive parallel selection traits between large white and Duroc pigs

In the process of pig genetic improvement, different commercial breeds have been bred for the same purpose, improving meat production. Most of the economic traits, such as growth and fertility, have been selected similarly despite the discrepant selection pressure, which is known as parallel selection. Here, 28 whole-genome sequencing data of Danish large white pigs with an approximately 25-fold depth each were generated, resulting in about 12 million high-quality SNPs for each individual. Combined with the sequencing data of 27 Duroc and 23 European wild boars, we investigated the parallel selection of Danish large white and Duroc pigs using two complementary methods, Fst and iHS. In total, 67 candidate regions were identified as the signatures of parallel selection. The genes in candidate regions of parallel selection were mainly associated with sensory perception, growth rate, and body size. Further functional annotation suggested that the striking consistency of the terms may be caused by the polygenetic basis of quantitative traits, and revealing the complex genetic basis of parallel selection. Besides, some unique terms were enriched in population-specific selection regions, such as the limb development-related terms enriched in Duroc-specific selection regions, suggesting unique selections of breed-specific selected traits. These results will help us better understand the parallel selection process of different breeds. Moreover, we identified several potential causal SNPs that may contribute to the pig genetic breeding process.

In vivo and in vitro activation of dormant primordial follicles by EGF treatment in mouse and human

In the mammalian ovaries, dormant primordial follicles represent the reproductive reserve of individual females. Recently, stimulating the activation of primordial follicles in vitro has been practiced, making the utilization of those dormant follicles to treat female infertility possible. However, there are still lacks of effective upstream molecule and strategy to elevate follicle activation in vivo. In the current study, we revealed that growth factor EGF improved a transiently primordial follicle activation in mice by elevating the CDC42-PI3K signaling activity, and EGF treatment also improved the activation and development of human follicles in ovarian cortical pieces. Using a liquid-solid phase transition bio-gel as a carrier, an efficient in vivo activation system was established by ovarian topical EGF administration to living mice. We found that EGF treatment led to an increase of primordial follicle activation in short time but had no effect on long-term fertility in females. By establishing an inducible premature ovarian insufficiency (POI) mouse model through selectively ablating growing follicles in Zp3-Cre;iDTR mice, we further revealed that our in vivo EGF treatment system improved primordial follicle activation and ovulation of POI ovaries significantly. Taken together, our results revealed that in situ ovarian EGF administration could improve the activation of primordial follicles in living animals, and manipulating activation and development of primordial follicles in vivo might be an efficient approach to improve reproductive health in women.

Circular RNA profiling in the oocyte and cumulus cells reveals that circARMC4 is essential for porcine oocyte maturation

Thousands of circular RNAs (circRNAs) have been recently discovered in cumulus cells and oocytes from several species. However, the expression and function of circRNA during porcine oocyte meiotic maturation have been never examined. Here, we separately identified 7,067 and 637 circRNAs in both cumulus cells and oocytes via deep sequencing and bioinformatic analysis. Further analysis revealed that a faction of circRNAs is differentially expressed (DE) in a developmental stage-specific manner. The host genes of DE circRNAs are markedly enriched to multiple signaling pathways associated with cumulus cell function and oocyte maturation. Additionally, most DE circRNAs harbor several miRNA targets, suggesting that these DE circRNAs potentially act as miRNA sponge. Importantly, we found that maternal circARMC4 knockdown by siRNA microinjection caused a severely impaired chromosome alignment, and significantly inhibited first polar body extrusion and early embryo development. Taken together, these results demonstrate for the first time that circRNAs are abundantly and dynamically expressed in a developmental stage-specific manner in cumulus cells and oocytes, and maternally expressed circARMC4 is essential for porcine oocyte meiotic maturation and early embryo development.

Optimal doses of EGF and GDNF act as biological response modifiers to improve porcine oocyte maturation and quality

It is well documented that both epidermal growth factor (EGF) and glial cell line-derived neurotrophic factor (GDNF) are critical for porcine oocyte maturation, however, little information is known about their mechanism of action in vitro. To gain insight into the mechanisms of action of the optimum doses of EGF and GDNF on porcine oocyte maturation, porcine cumulus–oocyte complexes (COCs) were matured in defined porcine oocyte medium supplemented with EGF, GDNF or a combination of both at varying concentrations (0–100 ng/ml) for 44 h. Nuclear and cytoplasmic maturation were determined in terms of nuclear stage after DNA staining with Hoechst and cortical granule distribution after lectin labeling, respectively. Mature oocytes were subsequently collected for gene expression analysis or subjected to in vitro fertilization and cultured for 7 days. The results showed that EGF and/or GDNF, when administered in a certain dose (50 ng/μl) to the maturation medium, not only effectively improved the synchronization of nuclear and cytoplasmic maturation processes within the oocyte, but enhanced expression of their corresponding receptors in mature oocytes (P < 0.05). Moreover, supplementation with an optimal combination of EGF + GDNF resulted in elevation of TFAM transcripts as well as a decrease of caspase-3 transcripts compared with the other studied groups (P < 0.05). Collectively, our results indicate that treatment of porcine oocytes with specific-dose combinations of EGF and GDNF stimulates oocyte quality and competence by transcriptional modulation of genes involved in oocyte survival and competence.

Combination effects of epidermal growth factor and glial cell line-derived neurotrophic factor on the in vitro developmental potential of porcine oocytes

The developmental potential of in vitro matured porcine oocytes is still lower than that of oocytes matured and fertilized in vivo. Major problems that account for the lower efficiency of in vitro production include the improper nuclear and cytoplasmic maturation of oocytes. With the aim of improving this issue, the single and combined effects of epidermal growth factor (EGF) and glial cell line-derived neurotrophic factor (GDNF) on oocyte developmental competence were investigated. Porcine cumulus-oocyte cell complexes (COCs) were matured in serum-free medium supplemented with EGF (0, 10 or 50 ng/ml) and/or GDNF (0, 10 or 50 ng/ml) for 44 h, and subsequently subjected to fertilization and cultured for 7 days in vitro. The in vitro-formed blastocysts derived from selected growth factor groups (i.e. EGF = 50 ng/ml; GDNF = 50 ng/ml; EGF = 50 ng/ml + GDNF = 50 ng/ml) were also used for mRNA expression analysis, or were subjected to Hoechst staining. The results showed that the addition of EGF and/or GDNF during oocyte maturation dose dependently enhanced oocyte developmental competence. Compared with the embryos obtained from control or single growth factor-treated oocytes, treatment with the combination of EGF and GDNF was shown to significantly improve oocyte competence in terms of blastocyst formation, blastocyst cell number and blastocyst hatching rate (P < 0.05), and also simultaneously induced the expression of BCL-xL and TERT and suppressed the expression of caspase-3 in resulting blastocysts (P < 0.05). These results suggest that both GDNF and EGF may play an important role in the regulation of porcine in vitro oocyte maturation and the combination of these growth factors could promote oocyte competency and blastocyst quality.

Effects of the anti-androgen cyproterone acetate (CPA) on oocyte meiotic maturation in rainbow trout (Oncorhynchus mykiss)

In the present study, we aimed at characterizing the effect of cyproterone acetate (CPA), an anti-androgenic compound, on oocyte meiotic maturation in a freshwater teleost fish species, the rainbow trout (Oncorhynchus mykiss). Fully-grown post-vitellogenic ovarian follicles were incubated in vitro with CPA, luteinizing hormone (Lh) or a combination of CPA and Lh. Incubations were also performed using a combination of Lh and testosterone (T). The occurrence of oocyte maturation (i.e., resumption of the meiotic process) was assessed by monitoring germinal vesicle breakdown (GVBD) after a 72h in vitro incubation. The effect of CPA on the production of 17,20β-dihydroxy-4-pregnen-3-one (17,20βP), the natural maturation-inducing steroid (MIS), was quantified by radioimmunoassay. Our results show that CPA dramatically inhibits Lh-induced oocyte maturation and MIS synthesis. We also observed a synergistic effect of Lh and T on oocyte maturation in highly competent oocytes (i.e., able to resume meiosis after stimulation by low doses of Lh). Our results also show that a combination of CPA and Lh inhibits phosphorylation of extracellular signal-regulated kinase (Erk), kinases that are associated with oocyte maturation in many species. As a whole, our results indicate that CPA has a potential to alter meiotic maturation in rainbow trout. Further analyses are, however, needed to determine the mechanisms by which this anti-androgen interferes with the meiotic process. Furthermore, the present study provides a framework for better understanding of the ecological consequences of exposure to anti-androgens and resulting meiotic maturation abnormalities observed in trout.

Arachidonic and linoleic acid derivatives impact oocyte ICSI fertilization--a prospective analysis of follicular fluid and a matched oocyte in a 'one follicle--one retrieved oocyte--one resulting embryo' investigational setting

Objective

To evaluate human oocyte ability to undergo fertilization and subsequent preimplantation embryonic development in relation to a wide panel of follicular fluid (FF) arachidonic acid derivatives (AAD) and linoleic acid derivatives (LAD) of prospectively selected patients undergoing intracytoplasmic sperm injection (ICSI).

Methodology

Study was designed as a two center (a university clinic and a private clinic) prospective study. 54 women of 181 consecutive couples undergoing ICSI were prospectively found to be eligible for analysis. 'One follicle – one retrieved oocyte – one resulting embryo' approach was used. Each individual follicle was aspirated independently and matched to an oocyte growing in this particular follicular milieu. FF samples were assessed for AAD and LAD by high-performance liquid chromatography; additionally, activity of secretory phospholipase A (sPLA₂) was determined by enzyme-linked immunosorbent assay.

Principal Findings

Increased activity of sPLA₂ and significantly higher AAD and LAD levels were found in FF of oocytes that did not show two pronuclei or underwent degeneration after ICSI in comparison to oocytes with the appearance of two pronuclei. Receiver operating characteristics curve analysis identified acids with the highest sensitivity and specificity: 5oxo-hydroxyeicosatetraenoic, 16-hydroxyeicosatetraenoic, 9-hydroxyoctadecadieneoic and 12-hydroxyeicosatetraenoic. No significant differences between AAD and LAD related to embryo quality were found.

Conclusions/Significance

Our study demonstrates for the first time that elevated concentrations of AAD and LAD in FF at the time of oocyte retrieval significantly decrease the ability of oocytes to form pronuclei after ICSI. This may serve as a new tool for non-invasive assessment of oocyte developmental capacity. However, levels of AAD and LAD are not associated with subsequent embryo quality or pregnancy rate, and therefore more studies are needed to determine their usefulness in human IVF procedure.

Use of both cumulus cells' transcriptomic markers and zona pellucida birefringence to select developmentally competent oocytes in human assisted reproductive technologies

BACKGROUND

Selection of the best oocyte for subsequent steps of fertilization and embryo transfer was shown to be the crucial step in human infertility treatment procedure. Oocyte selection using morphological criteria mainly Zona pellucida (ZP) has been the gold standard method in assisted reproductive technologies (ART) clinics, but this selection approach has limitations in terms of accuracy, objectivity and constancy. Recent studies using OMICs-based approaches have allowed the identification of key molecular markers that quantitatively and non-invasively predict the oocyte quality for higher pregnancy rates and efficient infertility treatment. These biomarkers are a valuable reinforcement of the morphological selection criteria widely used in in vitro fertilization (IVF) clinics. In this context, this study was designed to investigate the relationship between transcriptomic predictors of oocyte quality found by our group and the conventional morphological parameters of oocyte quality mainly the ZP birefringence.

RESULTS

Microarray data revealed that 48 and 27 differentially expressed candidate genes in cumulus cells (CCs) were respectively overexpressed and underexpressed in the ZGP (Zona Good Pregnant) versus ZBNP (Zona Bad Non Pregnant) groups. More than 70% of previously reported transcriptomic biomarkers of oocyte developmental competence were confirmed in this study. The analysis of possible association between ZP birefringence versus molecular markers approach showed an absence of correlation between them using the current set of markers.

CONCLUSIONS

This study suggested a new integrative approach that matches morphological and molecular approaches used to select developmentally competent oocytes able to lead to successful pregnancy and the delivery of healthy baby. For each ZP birefringence score, oocytes displayed a particular CCs' gene expression pattern. However, no correlations were found between the 7 gene biomarkers of oocyte developmental potential and the ZP birefringence score. Further studies using larger lists of candidate markers are required to identify suitable genes that are highly correlated with the morphological criteria, and therefore able to reinforce the accuracy of oocyte selection and the effectiveness of infertility treatment.

Neurotensin enhances sperm capacitation and acrosome reaction in mice

Neurotensin (NT) has multiple functions, ranging from acting as a neurotransmitter to regulating intestinal movement. However, its function in reproductive physiology is unknown. Here, we confirmed the expression and localization of NT receptors (NTR1) in mouse epididymal spermatozoa and investigated the effect of NT on sperm function. Sperm protein tyrosine phosphorylation, one of the indices of sperm capacitation, was facilitated dose-dependently by NT administration. In addition, the acrosome reaction was promoted in capacitated spermatozoa, and addition of a selective antagonist of NTR1 and NTR2 blocked the induction. Furthermore, intracellular calcium mobilization by NT addition was observed. This showed that NT was an accelerator of sperm function via its functional receptors. The presence of NT was confirmed by immunohistochemistry and its localization was observed in epithelia of the uterus and oviduct isthmus and ampulla, which correspond to the fertilization route of spermatozoa. The NT mRNA level in ovulated cumulus cell was remarkably increased by treatment with human chorionic gonadotropin (hCG). Using an in vitro maturation model, we analyzed the effects of FSH, epidermal growth factor (EGF), estradiol, and progesterone in NT production in cumulus cells. We found that FSH and EGF upregulated NT release and mRNA expression. Both FSH- and EGF-induced upregulation were inhibited by U0126, an MAPK kinase inhibitor, indicating that FSH and EGF regulate NT expression via a MAPK-dependent pathway. This evidence suggests that NT can act as a promoter of sperm capacitation and the acrosome reaction in the female reproductive tract.

Effect of epidermal growth factor-like peptides on the metabolism of in vitro- matured mouse oocytes and cumulus cells

Oocyte in vitro maturation (IVM) is an assisted reproductive technology that involves the maturation of cumulus-oocyte complexes (COCs) that are then capable of normal development. We have shown that epidermal growth factor (EGF)-like peptide signaling is perturbed in mouse COCs undergoing IVM when matured with follicle-stimulating hormone (FSH) and/or EGF, but supplementation of IVM with EGF-like peptides amphiregulin or epiregulin improves oocyte developmental competence. Here we aimed to determine whether EGF-like peptides regulate COC metabolism. Immature 129/Sv mouse COCs underwent IVM with FSH, EGF, amphiregulin, epiregulin, betacellulin, or no treatment (control). Epiregulin significantly increased intraoocyte flavin adenine dinucleotide (FAD) and REDOX (reduction and oxidation) ratio compared to FSH and control. Amphiregulin and epiregulin significantly increased the proportion of J aggregates (from JC-1) in oocyte mitochondria compared to control, FSH, or EGF, and this coupled with FAD and REDOX measures indicates greater mitochondrial activity. There were no differences in glucose consumption, lactate production, or glycolysis between COCs matured with FSH, EGF, and EGF-like peptides. COCs matured with EGF or EGF-like peptides exhibited significantly higher mRNA expression of the hexosamine biosynthesis pathway (HBP) rate-limiting enzyme gene Gfpt2, Has2 expression, and global beta-O-linked glycosylation of proteins, compared to control or FSH, suggesting greater HBP activity. Our findings suggest that 1) EGF-like peptides, particularly epiregulin, induce more oocyte mitochondrial activity than EGF or FSH and 2) EGF-like peptides and EGF induce greater HBP activity, enabling more hyaluronic acid synthesis and protein beta-O-linked glycosylation. These metabolic alterations may be a mechanism by which EGF-like peptides increase oocyte developmental competence.

Pre-maturation with cAMP modulators in conjunction with EGF-like peptides during in vitro maturation enhances mouse oocyte developmental competence

Recent studies have independently shown that cyclic adenosine 3'5'-monophosphate (cAMP) modulation prior to in vitro maturation (IVM) and epidermal growth factor (EGF)-like peptide supplementation during IVM improve subsequent oocyte developmental outcomes. This study investigated the effects of an IVM system that incorporates these two concepts. Cumulus-oocyte complexes (COCs) were collected from pre-pubertal mice either 46 hr post-equine chorionic gonadotropin (eCG) (IVM) or post-eCG + post-human chorionic gonadotropin (hCG) stimulation (in vivo maturation; IVV). IVM COCs were treated with the cAMP modulators forskolin and IBMX for 1, 2, or 4 hr (pre-IVM phase) prior to IVM. COCs then underwent IVM with the EGF-like peptides amphiregulin or epiregulin, or with the common IVM stimulants follicle-stimulating hormone (FSH) or EGF. A pre-IVM phase increased the size of the subsequent blastocysts' inner-cell-mass compared to standard IVM, regardless of IVM treatment (P < 0.05). Unlike FSH or EGF, amphiregulin or epiregulin significantly increased blastocyst quality (trophectoderm and total cell numbers) and/or yield (P < 0.01) compared to standard IVM, and were the only treatments that produced blastocysts comparable to IVV-derived blastocysts. Forskolin acutely up-regulated EGF-like peptide mRNA expression after a 2-hr pre-IVM phase (P < 0.001), although EGF receptor and ERK1/2 activities were not significantly different than control. IVV-like levels of EGF-like peptide mRNA expression during IVM were maintained only by supplementing with EGF-like peptides and EGF, since expression levels induced by FSH were significantly lower in vitro than during IVV. However, EGF receptor and ERK1/2 phosphorylation levels were not significantly different across treatment groups. In conclusion, a pre-IVM phase in conjunction with IVM in the presence of EGF-like peptides endows high oocyte developmental competence, as evidenced by increased embryo yield and/or quality relative to FSH and EGF.

Regulation of sheep oocyte maturation using cAMP modulators

Physical removal of mammalian cumulus-oocyte complexes (COCs) from ovarian follicles results in spontaneous resumption of meiosis, largely because of a decrease in cAMP concentrations, causing asynchrony between cytoplasmic and nuclear maturation and decreased oocyte developmental competence. The aim of this study was to modulate cAMP concentrations within ovine COCs to delay spontaneous nuclear maturation and improve developmental competence. Abattoir-derived sheep COCs were cultured for 2 hours (pre-IVM) in 100 μM forskolin (FSK) plus 500 μM 3-isobutyl-1-methylxanthine (IBMX). Pre-IVM (100 μM FSK and 500 μM IBMX) culture increased COC cAMP concentrations 10-fold compared with controls (P < 0.05). With regard to nuclear maturation, with FSK and IBMX and/or with FSH and cilostamide delayed completion of meiosis (metaphase II) by 3 to 4 hours compared with standard IVM (FSH-stimulated induction of meiosis). In this study, pre-IVM (with FSK and IBMX) followed by IVM (with FSH and cilostamide), increased ovine COC cAMP concentrations and delayed, but did not inhibit, completion of nuclear maturation. This did not affect embryo development rates, but increased total cell number of blastocysts compared with IVM with FSH alone (103 ± 6 vs. 66 ± 4 cells, respectively; mean ± SEM; P < 0.05). We inferred that regulation of ovine oocyte cAMP concentrations during IVM improved embryo quality compared with embryos produced by standard IVM methods.

Signaling pathways regulating FSH- and amphiregulin-induced meiotic resumption and cumulus cell expansion in the pig

To define signaling pathways that drive FSH- and epidermal growth factor (EGF)-like peptide-induced cumulus expansion and oocyte meiotic resumption, in vitro cultured pig cumulus-oocyte complexes were treated with specific protein kinase inhibitors. We found that FSH-induced maturation of oocytes was blocked in germinal vesicle (GV) stage by protein kinase A (PKA), MAPK14, MAPK3/1, and EGF receptor (EGFR) tyrosine kinase inhibitors (H89, SB203580, U0126, and AG1478 respectively) whereas phosphoinositide-3-kinase/v-akt murine thymoma viral oncogene homolog (PI3K/AKT) inhibitor (LY294002) blocked maturation of oocytes in metaphase I (MI). Amphiregulin (AREG)-induced maturation of oocytes was efficiently blocked in GV by U0126, AG1478, and low concentrations of LY294002; H89, SB203580, and high concentrations of LY294002 allowed the oocytes to undergo breakdown of GV and blocked maturation in MI. Both FSH- and AREG-induced cumulus expansion was incompletely inhibited by H89 and completely inhibited by SB203580, U0126, AG1478, and LY294002. The inhibitors partially or completely inhibited expression of expansion-related genes (HAS2, PTGS2, and TNFAIP6) with two exceptions: H89 inhibited only TNFAIP6 expression and LY294002 increased expression of PTGS2. The results of this study are consistent with the idea that PKA and MAPK14 pathways are essential for FSH-induced transactivation of the EGFR, and synthesis of EGF-like peptides in cumulus cells and MAPK3/1 is involved in regulation of transcriptional and posttranscriptional events in cumulus cells required for meiotic resumption and cumulus expansion. PI3K/AKT signaling is important for regulation of cumulus expansion, AREG-induced meiotic resumption, and oocyte MI/MII transition. The present data also indicate the existence of an FSH-activated and PKA-independent pathway involved in regulation of HAS2 and PTGS2 expression in cumulus cells.

Activation of extracellular-signal regulated kinase by epidermal growth factor is potentiated by cAMP-elevating agents in primary cultures of adult rat hepatocytes

We investigated the effects of α- and β-adrenergic agonists on epidermal growth factor (EGF)-stimulated extracellular-signal regulated kinase (ERK) isoforms in primary cultures of adult rat hepatocytes. Hepatocytes were isolated and cultured with EGF (20 ng/ml) and/or α(1)-, α(2)- and β(2)-adrenergic agonists. Phosphorylated ERK isoforms (ERK1; p44 mitogen-activated protein kinase (MAPK) and ERK2; p42 MAPK) were detected by Western blotting analysis using anti-phospho-ERK1/2 antibody. The results show that EGF induced a 2.5-fold increase in ERK2-, but not ERK1-, phosphorylation within 3 min. This EGF-induced ERK2 activation was abolished by treatment with the EGF-receptor kinase inhibitor AG1478 (10(-7) M) or the MEK (MAPK kinase) inhibitor PD98059 (10(-6) M). The α(2)-adrenergic and β(2)-adrenergic agonists, UK14304 (10(-6) M) and metaproterenol (10(-6) M), respectively, had no effect in the absence of EGF, but metaproterenol significantly potentiated EGF-induced ERK2 phosphorylation. Moreover, the cell-permeable cAMP analog 8-bromo cAMP (10(-7) M), also potentiated EGF-induced ERK2 phosphorylation. The effects of these analogs were antagonized by the protein kinase A (PKA) inhibitor H-89 (10(-7) M). These results suggest that direct or indirect activation of PKA represents a positive regulatory mechanism for EGF stimulation of ERK2 induction.

Erk2 in ovarian development of green mud crab Scylla paramamosain

We identified extracellular signal-regulated kinase 2 (erk2) from green mud crab, Scylla paramamosain, in this article. It was originally identified from an expressed sequence tag fragment from a normalized gonadal cDNA library. 5' Rapid amplification of cDNA end (RACE) technique was used to obtain the 5' untranslated region (UTR). The full-length cDNA of Sp-erk2 is 1516 bp, including a 5'-terminal UTR of 19 bp, an open-reading frame of 1098 bp, and a 3'-terminal UTR of 399 bp. The translated protein is 365 amino acids in length with a predicted molecular weight of 42 kDa, which is the same as other species. It is the first time that the expression of Sp-erk2 in different stages of ovary development of crustacean was analyzed, and the result showed that the expression of Sp-erk2 increased gradually with ovarian development, with a peak in the mature phase. In situ hybridization histochemistry was used to clarify the detail of expression. Positive signals illustrated that Sp-erk2 mRNA is present in follicular cells when the ovary is in early stages, and in both follicular cells and oocytes when it is in mature phases. All above suggest that Sp-erk2 is important for ovarian development.

The role of androgens in follicle maturation and ovulation induction: friend or foe of infertility treatment?

BACKGROUND

Effects of androgens on follicle maturation have been controversial for some time. Here, we review the potential of their applications in improving human ovulation induction, based on human and animal data, reported in the literature.

METHODS

We reviewed the published literature for the years 2005-2011, using relevant key words, in PubMed, Medline and Cochrane reviews, and then performed secondary reviews of referenced articles, which previously had not been known or preceded the searched time period. A total of 217 publications were reviewed.

RESULTS

Contrary to widely held opinion, recent data, mostly developed in the mouse, convincingly demonstrate essential contribution of androgens to normal follicle maturation and, therefore, female fertility. Androgens appear most engaged at preantral and antral stages, primarily affect granulosa cells, and exert effects via androgen receptors (AR) through transcriptional regulation but also in non-genomic ways, with ligand-activated AR modulating follicle stimulating hormone (FSH) activity in granulosa cells. While some androgens, like testosterone (T) and dehydroepiandrosterone (DHEA), appear effective in improving functional ovarian reserve (FOR) in women with diminished ovarian reserve (DOR), others may even exert opposite effects. Such differences in androgens may, at least partially, reflect different levels of agonism to AR.

DISCUSSION

Selective androgens appear capable of improving early stages of folliculogenesis. They, therefore, may represent forerunners of a completely new class of ovulation-inducing medications, which, in contrast to gonadotropins, affect follicle maturation at much earlier stages.

Possible involvement of Class III phosphatidylinositol-3-kinase in meiotic progression of porcine oocytes beyond germinal vesicle stage

Phosphatidylinositol-3-kinases (PI3Ks) play pivotal roles in meiotic progression of oocytes from metaphase I to metaphase II stage. Using a Class III-specific inhibitor of PI3K, 3-methyladenine (3MA), this study shows that Class III PI3K may be essential for meiotic progression of porcine oocytes beyond germinal vesicle (GV) stage. Treatment of immature porcine oocytes with 3MA for 22-42 h arrested them at the GV stage, irrespective of the presence or absence of cumulus cells. Furthermore, a significantly high proportion (60.9 ± 13.8%) of 3MA-treated oocytes acquired a nucleolus completely surrounded by a rim of highly condensed chromatin (GV-II stage). The GV-arresting effect of 3MA was, however, completely reversible upon their further culture in the absence of 3MA for 22 h. When cumulus-oophorus-complexes (COCs), arrested at the GV stage for 22 h by 3MA, were further cultured for 22 h in the absence of 3MA, 96.1 ± 1.5% of oocytes reached the MII stage at 42 h of IVM and did not differ from non-treated control oocytes with respect to their ability to fertilize, cleave and form blastocyst (P > 0.05) upon in vitro fertilization (IVF) or parthenogenetic activation (PA). These data suggest that 3MA efficiently blocks and synchronizes the meiotic progression of porcine oocytes at the GV stage without affecting their ooplasmic maturation in terms of post-fertilization/activation in vitro embryonic development. Our data also provide indirect evidence for the likely participation of Class III PI3K in meiotic maturation of porcine oocyte beyond the GV stage.

The signal pathway of gonadotrophins-induced mammalian oocyte meiotic resumption

Fully grown mammalian oocytes are arrested at the first meiotic prophase until a surge of gonadotrophin at the mid-cycle. The actions of gonadotrophins, follicle stimulating hormone (FSH) and luteinizing hormone (LH), on oocyte meiotic resumption are believed to be mediated in large part through increasing the production of cyclic adenosine 3',5'-monophosphate and subsequent activation of mitogen-activated protein kinase (MAPK) in its surrounding cumulus granulosa cells. Recent findings indicate that gonadotrophins-induced epidermal growth factor-like growth factors, meiosis activating sterol and gonadal steroid hormones, possibly via protein kinase A II and protein kinase C pathways, are involved in the activation of MAPK. Another second messenger cyclic guanosine 3',5'-monophosphate induced by nitric oxide or natriuretic peptides system mediates the function of gonadotrophins during oocyte meiotic resumption. FSH and LH induced pathways may either directly overlap or each hormone may utilize redundant pathways in oocyte maturation. A detailed appreciation of different FSH and LH-activated signaling pathways in mammalian oocytes will be needed in understanding their actions in follicular development and oocyte maturation.

Successful piglet production in a chemically defined system for in-vitro production of porcine embryos: dibutyryl cyclic amp and epidermal growth factor-family peptides support in-vitro maturation of oocytes in the absence of gonadotropins

To induce meiotic resumption of porcine oocytes, it is thought to be necessary to expose the cumulus-oocyte complexes (COCs) to gonadotropins during in-vitro maturation (IVM). However, the detailed mechanism of meiotic resumption by gonadotropins is still unknown, and successful piglet production has not been reported by using oocytes matured in gonadotropin-free media and fertilized in vitro. The present study was undertaken to examine the combinational effects of epidermal growth factor (EGF)-family members and dibutyryl cyclic AMP (cAMP) in a chemically defined medium on IVM of porcine oocytes and the developmental competence following in vitro fertilization (IVF). The basic IVM medium was a chemically defined medium, modified porcine oocyte medium (mPOM). Supplementation of the IVM medium with 10 or 1000 ng/ml EGF, amphiregulin and betacellulin during the whole IVM period, except for 10 ng/ml amphiregulin, increased the percentage of oocytes maturing to the metaphase-II stage. When COCs were exposed to both dibutyryl cAMP and EGF-family members during the first 20-h of IVM and then culture was continued in the absence of EGF-family members and dibutyryl cAMP, the incidence of metaphase-II oocytes was significantly increased and was not different from that of oocytes cultured in a standard IVM system with gonadotropins. The developmental competence of the oocytes to the blastocyst stage following IVF was no different from that of control oocytes matured with gonadotropins. When these blastocysts were transferred into the uterine horn of three recipients, all of gilts became pregnant and delivered a total of 11 piglets. These observations indicate that supplementation of a chemically defined maturation medium with EGF-family members and dibutyryl cAMP during the first 20 h of IVM can support well the meiotic progress and developmental competence of porcine oocytes.

Androgen receptor's destiny in mammalian oocytes: a new hypothesis

Unlike the well-established roles of androgen and androgen receptor (AR) in males, the functions of this steroid and its receptor in the ovary are still unclear. For decades, androgen and AR have long been considered to play a negative (at least not a positive) role in mammalian oocyte maturation. However, recent studies by us and others showed their positive influence in promoting meiotic maturation. On the other hand, rapid non-genomic effects of androgens have been observed and are now generally accepted as contributing to the physiological effects of the steroids and their related receptors in somatic cells, and this has stimulated us to explore the complex roles of AR in the ovary. Based on the classic dogma and new findings, we collected evidence to propose that the expression of AR shifts from the oocytes to the theca cells and finally disappears in the oocytes during evolution. It is suggested that the non-genomic pathway involving androgen and AR in the mammalian oocytes, unlike somatic cells, cells will undergo elimination. The function of androgen and AR in promoting meiotic maturation may have been replaced gradually by gonadotrophins. Moreover, a possible relationship between AR and polycystic ovary syndrome is also discussed, which might provide a clue for the pathology of the disease.

3',5'-cyclic adenosine monophosphate response element binding protein up-regulated cytochrome P450 lanosterol 14alpha-demethylase expression involved in follicle-stimulating hormone-induced mouse oocyte maturation

Cytochrome P450 lanosterol 14alpha-demethylase (CYP51) is a key enzyme in sterols and steroids biosynthesis that can induce meiotic resumption in mouse oocytes. The present study investigated the expression mechanism and function of CYP51 during FSH-induced mouse cumulus oocyte complexes (COCs) meiotic resumption. FSH increased cAMP-dependent protein kinase (PKA) RIIbeta level and induced cAMP response element-binding protein (CREB) phosphorylation and CYP51 expression in cumulus cells before oocyte meiotic resumption. Moreover, CYP51 and epidermal growth factor (EGF)-like factor [amphiregulin (AR)] expression were blocked by (2)-naphthol-AS-Ephosphate (KG-501) (a drug interrupting the formation of CREB functional complex). KG-501 and RS21607 (a specific inhibitor of CYP51 activity) inhibited oocyte meiotic resumption, which can be partially rescued by progesterone. These two inhibitors also inhibited FSH-induced MAPK phosphorylation. EGF could rescue the suppression by KG-501 but not RS21607. Furthermore, type II PKA analog pairs, N(6)-monobutyryl-cAMP plus 8-bromo-cAMP, increased PKA RIIbeta level and mimicked the action of FSH, including CREB phosphorylation, AR and CYP51 expression, MAPK activation, and oocyte maturation. All these data suggest that CYP51 plays a critical role in FSH-induced meiotic resumption of mouse oocytes. CYP51 and AR gene expression in cumulus cells are triggered by FSH via a type II PKA/CREB-dependent signal pathway. Our study also implicates that CYP51 activity in cumulus cells participates in EGF receptor signaling-regulated oocyte meiotic resumption.