Energy Substrate Metabolism of Mouse Cumulus-Oocyte Complexes: Response to Follicle-Stimulating Hormone Is Mediated by the Phosphatidylinositol 3-Kinase Pathway and Is Associated with Oocyte Maturation1

Selective autophagic degradation of ACLY (ATP citrate lyase) maintains citrate homeostasis and promotes oocyte maturation

Macroautophagy/autophagy is a cellular and energy homeostatic mechanism that contributes to maintain the number of primordial follicles, germ cell survival, and anti-ovarian aging. However, it remains unknown whether autophagy in granulosa cells affects oocyte maturation. Here, we show a clear tendency of reduced autophagy level in human granulosa cells from women of advanced maternal age, implying a potential negative correlation between autophagy levels and oocyte quality. We therefore established a co-culture system and show that either pharmacological inhibition or genetic ablation of autophagy in granulosa cells negatively affect oocyte quality and fertilization ability. Moreover, our metabolomics analysis indicates that the adverse impact of autophagy impairment on oocyte quality is mediated by downregulated citrate levels, while exogenous supplementation of citrate can significantly restore the oocyte maturation. Mechanistically, we found that ACLY (ATP citrate lyase), which is a crucial enzyme catalyzing the cleavage of citrate, was preferentially associated with K63-linked ubiquitin chains and recognized by the autophagy receptor protein SQSTM1/p62 for selective autophagic degradation. In human follicles, the autophagy level in granulosa cells was downregulated with maternal aging, accompanied by decreased citrate in the follicular fluid, implying a potential correlation between citrate metabolism and oocyte quality. We also show that elevated citrate levels in porcine follicular fluid promote oocyte maturation. Collectively, our data reveal that autophagy in granulosa cells is a beneficial mechanism to maintain a certain degree of citrate by selectively targeting ACLY during oocyte maturation.Abbreviations: 3-MA: 3-methyladenine; ACLY: ATP citrate lyase; AMA: advanced maternal age; CG: cortical granule; CHX: cycloheximide; CQ: chloroquine; CS: citrate synthase; COCs: cumulus-oocyte-complexes; GCM: granulosa cell monolayer; GV: germinal vesicle; MII: metaphase II stage of meiosis; PB1: first polar body; ROS: reactive oxygen species; shRNA: small hairpin RNA; SQSTM1/p62: sequestosome 1; TCA: tricarboxylic acid; TOMM20/TOM20: translocase of outer mitochondrial membrane 20; UBA: ubiquitin-associated domain; Ub: ubiquitin; WT: wild-type.

Glucose consumption and gene expression in granulosa cells collected before and after in vitro oocyte maturation in the southern white rhinoceros (Ceratotherium simum simum)

CONTEXT

With two northern white rhinos (NWR) remaining, the continued existence of this species relies on studying their relative, the southern white rhino (SWR).

AIMS

(1) Characterise gene expression in granulosa cells (GC) from SWR cumulus oocyte complexes (COCs) prior to (Pre-) and after (Post-) in vitro maturation (IVM), comparing culture media and oocytes from donors treated with or without gonadotropin stimulation prior to ovum recovery; and (2) evaluate COC glucose consumption in spent media.

METHODS

COCs were retrieved from four SWRs. Granulosa cells were collected before and after IVM in SDZ or IZW medium. Total RNA was evaluated by qPCR.

KEY RESULTS

Oocyte maturation was greater in SDZ than IZW media. Expression of genes associated with follicle development increased in Pre-IVM GC. Six genes were differentially expressed in Post-IVM GC from stimulated compared to unstimulated donors. COCs from stimulated animals consumed more glucose. Fifty seven percent of oocytes in SDZ medium consumed all available glucose.

CONCLUSIONS

Gene expression changed upon in vitro maturation and gonadotropin stimulation. Higher glucose availability might be needed during IVM.

IMPLICATIONS

This is the first study examining GC gene expression and COC metabolic requirements in rhinoceros, which are critical aspects to optimise IVM of rhinoceros oocytes.

Direct impact of gonadotropins on glucose uptake and storage in preovulatory granulosa cells: Implications in the pathogenesis of polycystic ovary syndrome

BACKGROUND

Polycystic ovary syndrome (PCOS) is often associated with higher levels of LH, and arrested ovarian follicular growth. The direct impact of high LH on FSH mediated metabolic responses in PCOS patients is not clearly understood.

METHOD

In order to investigate the impact of FSH and LH on glucose metabolism in preovulatory granulosa cells (GCs), we used [U¹⁴C]-2 deoxyglucose, D-[U¹⁴C]-glucose or 2-NBD glucose to analyse glucose uptake and its incorporation into glycogen. To reproduce the high androgenic potential in PCOS patients, we administered hCG both in vitro and in vivo. The role of IRS-2/PI3K/Akt2 pathway was studied after knockdown with specific siRNA. Immunoprecipitation and specific assays were used for the assessment of IRS-2, glycogen synthase and protein phosphatase 1. Furthermore, we examined the in vivo effects of hCG on FSH mediated glycogen increase in normal and PCOS rat model. HEK293 cells co-expressing FSHR and LHR were used to demonstrate glucose uptake and BRET change by FSH and hCG.

RESULTS

In normal human and rat granulosa cells, FSH is more potent than hCG in stimulating glucose uptake, however glycogen synthesis was significantly upregulated only by FSH through increase in activity of glycogen synthase via IRS-2/PI3K/Akt2 pathway. On the contrary, an impaired FSH-stimulated glucose uptake and glycogen synthesis in granulosa cells of PCOS-patients indicated a selective defect in FSHR activation. Further, in normal human granulosa cells, and in immature rat model, the impact of hCG on FSH responses was such that it inhibited the FSH-mediated glucose uptake as well as glycogen synthesis through inhibition of FSH-stimulated IRS-2 expression. These findings were further validated in HEK293 cells overexpressing Flag-LHR and HA-FSHR, where high hCG inhibited the FSH-stimulated glucose uptake. Notably, an increased BRET change was observed in HEK293 cells expressing FSHR-Rluc8 and LHR-Venus possibly suggesting increased heteromerization of LHR and FSHR in the presence of both hCG and FSH in comparison to FSH or hCG alone.

CONCLUSION

Our findings confirm a selective attenuation of metabolic responses to FSH such as glucose uptake and glycogen synthesis by high activation level of LHR leading to the inhibition of IRS-2 pathway, resulting in depleted glycogen stores and follicular growth arrest in PCOS patients.

Metabolic co-dependence of the oocyte and cumulus cells: essential role in determining oocyte developmental competence

BACKGROUND

Within the antral follicle, the oocyte is reliant on metabolic support from its surrounding somatic cells. Metabolism plays a critical role in oocyte developmental competence (oocyte quality). In the last decade, there has been significant progress in understanding the metabolism of the cumulus-oocyte complex (COC) during its final stages of growth and maturation in the follicle. Certain metabolic conditions (e.g. obesity) or ART (e.g. IVM) perturb COC metabolism, providing insights into metabolic regulation of oocyte quality.

OBJECTIVE AND RATIONALE

This review provides an update on the progress made in our understanding of COC metabolism, and the metabolic conditions that influence both meiotic and developmental competence of the oocyte.

SEARCH METHODS

The PubMed database was used to search for peer-reviewed original and review articles. Searches were performed adopting the main terms 'oocyte metabolism', 'cumulus cell metabolism', 'oocyte maturation', 'oocyte mitochondria', 'oocyte metabolism', 'oocyte developmental competence' and 'oocyte IVM'.

OUTCOMES

Metabolism is a major determinant of oocyte quality. Glucose is an essential requirement for both meiotic and cytoplasmic maturation of the COC. Glucose is the driver of cumulus cell metabolism and is essential for energy production, extracellular matrix formation and supply of pyruvate to the oocyte for ATP production. Mitochondria are the primary source of ATP production within the oocyte. Recent advances in real-time live cell imaging reveal dynamic fluctuations in ATP demand throughout oocyte maturation. Cumulus cells have been shown to play a central role in maintaining adequate oocyte ATP levels by providing metabolic support through gap junctional communication. New insights have highlighted the importance of oocyte lipid metabolism for oocyte oxidative phosphorylation for ATP production, meiotic progression and developmental competence. Within the last decade, several new strategies for improving the developmental competence of oocytes undergoing IVM have emerged, including modulation of cyclic nucleotides, the addition of precursors for the antioxidant glutathione or endogenous maturation mediators such as epidermal growth factor-like peptides and growth differentiation factor 9/bone morphogenetic protein 15. These IVM additives positively alter COC metabolic endpoints commonly associated with oocyte competence. There remain significant challenges in the study of COC metabolism. Owing to the paucity in non-invasive or in situ techniques to assess metabolism, most work to date has used in vitro or ex vivo models. Additionally, the difficulty of measuring oocyte and cumulus cell metabolism separately while still in a complex has led to the frequent use of denuded oocytes, the results from which should be interpreted with caution since the oocyte and cumulus cell compartments are metabolically interdependent, and oocytes do not naturally exist in a naked state until after fertilization. There are emerging tools, including live fluorescence imaging and photonics probes, which may provide ways to measure the dynamic nature of metabolism in a single oocyte, potentially while in situ.

WIDER IMPLICATIONS

There is an association between oocyte metabolism and oocyte developmental competence. Advancing our understanding of basic cellular and biochemical mechanisms regulating oocyte metabolism may identify new avenues to augment oocyte quality and assess developmental potential in assisted reproduction.

D-Chiro-Inositol Treatment Affects Oocyte and Embryo Quality and Improves Glucose Intolerance in Both Aged Mice and Mouse Models of Polycystic Ovarian Syndrome

Polycystic ovarian syndrome (PCOS) is the main cause of female infertility. It is a multifactorial disorder with varying clinical manifestations including metabolic/endocrine abnormalities, hyperandrogenism, and ovarian cysts, among other conditions. D-Chiro-inositol (DCI) is the main treatment available for PCOS in humans. To address some of the mechanisms of this complex disorder and its treatment, this study examines the effect of DCI on reproduction during the development of different PCOS-associated phenotypes in aged females and two mouse models of PCOS. Aged females (8 months old) were treated or not (control) with DCI for 2 months. PCOS models were generated by treatment with dihydrotestosterone (DHT) on Days 16, 17, and 18 of gestation, or by testosterone propionate (TP) treatment on the first day of life. At two months of age, PCOS mice were treated with DCI for 2 months and their reproductive parameters analyzed. No effects of DCI treatment were produced on body weight or ovary/body weight ratio. However, treatment reduced the number of follicles with an atretic cyst-like appearance and improved embryo development in the PCOS models, and also increased implantation rates in both aged and PCOS mice. DCI modified the expression of genes related to oocyte quality, oxidative stress, and luteal sufficiency in cumulus-oocyte complexes (COCs) obtained from the aged and PCOS models. Further, the phosphorylation of AKT, a main metabolic sensor activated by insulin in the liver, was enhanced only in the DHT group, which was the only PCOS model showing glucose intolerance and AKT dephosphorylation. The effect of DCI in the TP model seemed mediated by its influence on oxidative stress and follicle insufficiency. Our results indicate that DCI works in preclinical models of PCOS and offer insight into its mechanism of action when used to treat this infertility-associated syndrome.

A biophotonic approach to measure pH in small volumes in vitro: Quantifiable differences in metabolic flux around the cumulus-oocyte-complex (COC)

Unfertilised eggs (oocytes) release chemical biomarkers into the medium surrounding them. This provides an opportunity to monitor cell health and development during assisted reproductive processes if detected in a non-invasive manner. Here we report the measurement of pH using an optical fibre probe, OFP1, in 5 μL drops of culture medium containing single mouse cumulus oocyte complexes (COCs). This allowed for the detection of statistically significant differences in pH between COCs in culture medium with no additives and those incubated with either a chemical (cobalt chloride) or hormonal treatment (follicle stimulating hormone); both of which serve to induce the release of lactic acid into the medium immediately surrounding the COC. Importantly, OFP1 was shown to be cell-safe with no inherent cell toxicity or light-induced phototoxicity indicated by negative DNA damage staining. Pre-measurement photobleaching of the probe reduced fluorescence signal variability, providing improved measurement precision (0.01-0.05 pH units) compared to previous studies. This optical technology presents a promising platform for the measurement of pH and the detection of other extracellular biomarkers to assess cell health during assisted reproduction.

Lipidomic profiling of dairy cattle oocytes by high performance liquid chromatography-high resolution tandem mass spectrometry for developmental competence markers

A comparative lipidomic profiling analysis of dairy cattle oocytes with different developmental competences was performed using a combination of high performance liquid chromatography-high resolution tandem mass spectrometry and multivariate statistical analysis. Significant lipidomic changes were identified in degenerating oocytes. Total triacylglycerol in the degenerating oocytes was 1.8-fold higher than that in the normal oocytes; however, total cardiolipin was 53.5% lesser than that in the normal oocytes, which indicated attenuation of energy metabolism. Compared to those in the normal oocytes, triacylglycerols in the degenerating oocytes were composed of longer and more unsaturated acyl chains. In contrast, the acyl chains in free fatty acids present in the degenerating oocytes were shorter and with lesser degree of unsaturation compared to those in the normal oocytes. Moreover, a significant decrease in degenerating oocytes were found in total phosphatidylinositol (14.8 ± 7.6 pmol vs. 24.8 ± 5.5 pmol), total phosphatidylcholine (20.8 ± 8.7 pmol vs. 33.5 ± 7.2 pmol), and total plasmalogen ethanolamine (9.0 ± 4.7 pmol vs. 16.8 ± 5.2 pmol), which indicated dysfunction of lipid-metabolizing enzymes in oocytes during degeneration. Thus, increase of triacylglycerols together with the decrease of certain phospholipid species could be potential markers of oocyte developmental competence. In addition to providing a new approach to investigate the lipidomic changes in oocyte development, the lipidomic profiling in the present study has revealed insights that hold potential to unravel the role of lipid metabolism in oocyte developmental competence in cattle.

Effects of gonadotrophins and insulin on glucose uptake in the porcine cumulus-oocyte complex during IVM

The combination of gonadotrophins (LH and FSH) and insulin is frequently used in porcine oocyte IVM, but the individual effects of gonadotrophins and insulin have not been completely studied. The aim of this study was to investigate the mechanisms involved in glucose metabolism in the swine cumulus-oocyte complex (COC), analysing the effects of gonadotrophins (10IUmL-1 LH+10IUmL-1 FSH) and 0.4μUmL-1 insulin, during 44h of IVM, on glucose transport and consumption, as well as on nuclear maturation and sperm penetration. We evaluated the effects of gonadotrophins and insulin separately or in combination on glucose consumption, membrane permeability to the glucose fluorescent analogue 6-(N -(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-6-deoxyglucose (6-NBDG), the presence of GLUT-4 and oocyte maturation rates, after 44h of IVM. Nuclear maturation percentages increased significantly following the addition of gonadotrophins alone or in combination with insulin to the culture medium (P P P <0.0001). Although gonadotrophins and insulin increased GLUT-4 expression, neither modified 6-NBDG incorporation. In conclusion, gonadotrophins and insulin had different effects during IVM; although gonadotrophins increased maturation rates and glucose consumption, they had no effect on glucose transport, and insulin improved sperm penetration without affecting the parameters related to glucose utilisation. Therefore, glucose metabolism is likely to be primarily regulated by its consumption in metabolic pathways rather than by changes in membrane permeability.

FSH stimulates IRS-2 expression in human granulosa cells through cAMP/SP1, an inoperative FSH action in PCOS patients

Follicle stimulating hormone (FSH) plays a central role in growth and differentiation of ovarian follicles. A plethora of information exists on molecular aspects of FSH responses but little is known about the mechanisms involved in its cross-talk with insulin/IGF-1 pathways implicated in the coordination of energy homeostasis in preovulatory granulosa cells (GCs). In this study, we hypothesized that FSH may regulate IRS-2 expression and thereby maintain the energy balance in GCs. We demonstrate here that FSH specifically increases IRS-2 expression in human and rat GCs. FSH-stimulated IRS-2 expression was inhibited by actinomycin D or cycloheximide. Furthermore, FSH decreases IRS-2 mRNA degradation indicating post-transcriptional stabilization. Herein, we demonstrate a role of cAMP pathway in the activation of IRS-2 expression by FSH. Scan and activity analysis of IRS-2 promoter demonstrated that FSH regulates IRS-2 expression through SP1 binding sites. FSH stimulates SP1 translocation into nucleus and its binding to IRS-2 promoter. These results are corroborated by the fact that siRNA mediated knockdown of IRS-2 decreased the FSH-stimulated PI3K activity, p-Akt levels, GLUT4 translocation and glucose uptake. However, FSH was not able to increase IRS-2 expression in GCs from PCOS women undergoing IVF. Interestingly, IRS-2 mRNA expression was downregulated in GCs from the PCOS rat model. Taken together, our findings establish that FSH induces IRS-2 expression and thereby activates PI3K, Akt and glucose uptake. Crucially, our data confirms a molecular defect in FSH action in PCOS GCs which may cause deceleration of metabolism and follicular growth leading to infertility. These results lend support for a therapeutic potential of IRS-2 in the management of PCOS.

Scientific Statement on the Diagnostic Criteria, Epidemiology, Pathophysiology, and Molecular Genetics of Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is a heterogeneous and complex disorder that has both adverse reproductive and metabolic implications for affected women. However, there is generally poor understanding of its etiology. Varying expert-based diagnostic criteria utilize some combination of oligo-ovulation, hyperandrogenism, and the presence of polycystic ovaries. Criteria that require hyperandrogenism tend to identify a more severe reproductive and metabolic phenotype. The phenotype can vary by race and ethnicity, is difficult to define in the perimenarchal and perimenopausal period, and is exacerbated by obesity. The pathophysiology involves abnormal gonadotropin secretion from a reduced hypothalamic feedback response to circulating sex steroids, altered ovarian morphology and functional changes, and disordered insulin action in a variety of target tissues. PCOS clusters in families and both female and male relatives can show stigmata of the syndrome, including metabolic abnormalities. Genome-wide association studies have identified a number of candidate regions, although their role in contributing to PCOS is still largely unknown.

Female offspring sired by diet induced obese male mice display impaired blastocyst development with molecular alterations to their ovaries, oocytes and cumulus cells

PURPOSE

To investigate the impacts that a paternal high fat diet (HFD) has on embryology, ovarian/cumulus cell gene expression and COC metabolism from female offspring, using a mouse model.

METHODS

Founder male mice were either fed a control diet (CD) or a HFD for 12 weeks. The HFD induced obesity but not diabetes, and founder males were then mated to normal weight CD fed female mice. Female offspring were maintained on a CD, super-ovulated, mated and the resultant zygotes were cultured to the blastocyst stage for embryo morphology, blastocyst cell number and apoptosis assessment. Ovaries and cumulus cells from offspring were collected for gene expression analysis of selected genes that maintain chromatin remodeling and endoplasmic reticulum (ER), metabolic and inflammatory homeostasis. Cumulus/oocyte complexes were also investigated for glucose uptake and lipid accumulation.

RESULTS

Female offspring sired by obese fathers produced embryos with delayed development and impaired quality, displayed increases in ovarian expression of Glut1, Glut3 and Glut4, and an increase in cumulus cell expression of Glut4. Interestingly their COCs did take up more glucose, but did accumulate more lipid.

CONCLUSIONS

A paternal HFD is associated with subfertility in female offspring despite the offspring being fed a CD and this subfertility is concomitant with ovarian/cumulus cell molecular alterations and increased lipid accumulation.

Oocyte environment: follicular fluid and cumulus cells are critical for oocyte health

Bidirectional somatic cell-oocyte signaling is essential to create a changing intrafollicular microenvironment that controls primordial follicle growth into a cohort of growing follicles, from which one antral follicle is selected to ovulate a healthy oocyte. Such intercellular communications allow the oocyte to determine its own fate by influencing the intrafollicular microenvironment, which in turn provides the necessary cellular functions for oocyte developmental competence, which is defined as the ability of the oocyte to complete meiosis and undergo fertilization, embryogenesis, and term development. These coordinated somatic cell-oocyte interactions attempt to balance cellular metabolism with energy requirements during folliculogenesis, including changing energy utilization during meiotic resumption. If these cellular mechanisms are perturbed by metabolic disease and/or maternal aging, molecular damage of the oocyte can alter macromolecules, induce mitochondrial mutations, and reduce adenosine triphosphate production, all of which can harm the oocyte. Recent technologies are now exploring transcriptional, translational, and post-translational events within the human follicle with the goal of identifying biomarkers that reliably predict oocyte quality in the clinical setting.

Glycolytic pathway activity: effect on IVM and oxidative metabolism of bovine oocytes

The aim of the present study was to determine the effect of altering glycolytic pathway activity during bovine IVM on the meiotic maturation rate, oxidative activity, mitochondrial activity and the mitochondrial distribution within oocytes. Glycolytic activity was manipulated using two inhibitors (ATP, NaF) and a stimulator (AMP) of key enzymes of the pathway. Inhibition of glucose uptake, lactate production and meiotic maturation rates was observed when media were supplemented with ATP or NaF. The addition of AMP to the maturation medium had no effect on glucose uptake, lactate production or meiotic maturation. In the absence of gonadotrophin supplementation, AMP stimulated both glucose uptake and lactate production. However, AMP also decreased cytoplasmic maturation, as determined by early cleavage. During IVM, oocyte oxidative and mitochondrial activity was observed to increase at 15 and 22h maturation. Inhibiting glycolysis with ATP or NaF led to a reduced oxidative and mitochondrial pattern compared with the respective control groups. Stimulation of the pathway with AMP increased oxidative and mitochondrial activity. A progressive mitochondrial migration to the central area was observed during maturation; oocytes treated with ATP, NaF or AMP showed limited migration. The present study reveals the effects of altering glycolytic pathway activity in cumulus-oocyte complexes, revealing the link between glycolysis of the cumulus-oocyte complex and the oxidative and mitochondrial activity of the oocyte.

Molecular characterisation and expression profiling of the ENO1 gene in the ovarian follicle of the Sichuan white goose

The ENO1 gene encodes a multifunctional enzyme that has been identified as a key component of the glycolytic pathway. Our previous studies demonstrated that ENO1 gene expression was higher in the ovaries of laying geese compared with prelaying geese. However, the molecular characterisation and expression profiling of the ENO1 gene in geese tissues and ovarian follicles remain to be determined. In this study, ENO1 cDNA (1,445 bp long) of the Sichuan white goose was cloned and characterised. The ORF of ENO1 cDNA is 1,305 bp in length and encodes a 434 amino acid protein with a molecular weight of 47.27 kDa. ENO1 expression in all of the examined tissues was the highest in spleen and the lowest in breast muscle. High expression of ENO1 appeared in the kidney, liver, adrenal gland, and retina. With increasing follicle growth, ENO1 gene expression began to decrease from the small white follicle to F5, which was followed by a sharp increase in expression in F4 and then a gradual decrease in expression from F3 to F1. Furthermore, in the postovulatory follicles (POF), the levels of ENO1 gene expression decreased gradually from POF1 to POF4. In conclusion, the ENO1 transcript was widely distributed in various tissues of the Sichuan white goose, but ENO1 expression was tissue-specific. Furthermore, the results of the ENO1 expression profiling of ovarian follicles suggest that ENO1 may play an important dual role in the progress of follicular development, where ENO1 acts as a glycolytic enzyme and also mediates apoptosis.

Ranking and selection of MII oocytes in human ICSI cycles using gene expression levels from associated cumulus cells

STUDY QUESTION

Can the ranked expression levels of a cohort of cumulus cell (CC) genes be used to select MII oocytes with a potential for blastocyst development and live birth?

SUMMARY ANSWER

A ranking method containing four (HAS2, FSHR, VCAN, PR) of the eight genes evaluated in this study for identifying good quality MII oocytes provides a significantly better outcome compared with random selection and is equally as good as using all oocytes for ICSI.

WHAT IS KNOWN ALREADY

Recent evidence has identified a number of candidate genes in CC that have the potential to serve as markers of oocyte quality; however, a reliable method for selecting MII oocytes with blastocyst and live birth potential remains a challenge.

STUDY DESIGN, SIZE, DURATION

A group of 25 patients (<38 years old) underwent rFSH-stimulated ICSI treatment with single embryo replacement (SET). A total of 270 cumulus cell-oocyte complexes (COCs) were recovered and assessed.

MATERIALS, SETTING, METHODS

Expression levels of eight candidate genes (HAS2, FSHR, SLC2A4, ALCAM, SFRP2, VCAN, NRP1 and PR), corrected for RPL19, were measured in individual CC masses using multiplex QPCR. Expression levels of individual CC masses were assessed and ranked in relation to oocyte developmental indicators (blastocyst formation and live birth).

MAIN RESULTS AND THE ROLE OF CHANCE

From the 25 women, 19 (76%) had achieved a successful live birth delivery following SET. In this population, the selection of MII oocytes according to relative ranking levels of a subset of CC-expressed genes provided a significantly higher chance of identifying a good quality oocyte compared with selecting MII oocytes randomly (blastocyst: 1× MII oocyte: 52 versus 23%, P = 0.008; 3× MII oocytes: 80 versus 52%, P = 0.002; live birth: 1× MII oocyte: 31 versus 15%, P<0.05, 3× MII oocytes: 60 versus 38%, P < 0.05) and a similar chance to that of using all oocytes available after recovery (blastocyst: 80% versus 96%, P = 0.085, live birth: 60% versus 76%, P = 0.206).

LIMITATIONS, REASONS FOR CAUTION

The present method was validated only for young (<38 years) women, with male infertility, who had no signs of androgenicity, PCOS or endometriosis and were free of any chronic disease. This is a retrospective study that requires further validation in an unselected population.

WIDER IMPLICATIONS OF THE FINDINGS

Results presented in this study could be used to assist the selection of oocytes with high blastocyst developmental potential in frozen oocyte cycles and for the selection of embryos with high developmental potential as early as 18 h after ICSI (2PN stage) in fresh human IVF cycles.

STUDY FUNDING/COMPETING INTEREST(S)

Funding was provided by Fertility Associates Ltd and the New Zealand Government. The authors declare there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.

Comparison of assisted reproductive technology outcomes in infertile women with polycystic ovary syndrome: In vitro maturation, GnRH agonist, and GnRH antagonist cycles

OBJECTIVE

We compared the assisted reproductive technology (ART) outcomes among infertile women with polycystic ovary syndrome (PCOS) treated with IVM, conventional IVF, GnRH agonist, and GnRH antagonist cycles.

METHODS

The prospective study included a total of 67 cycles in 61 infertile women with PCOS. The women with PCOS were randomized into three IVF protocols: IVM/IVF with FSH and hCG priming with immature oocyte retrieval 38 hours later (group A, 14 cycles), GnRH agonist long protocol (group B, 14 cycles), and GnRH antagonist multi-dose flexible protocol (group C, 39 cycles). IVF outcomes, such as clinical pregnancy rate (CPR), implantation rate (IR), miscarriage rate (MR), and live birth rate (LBR), were compared among the three groups.

RESULTS

Age, BMI, and basal FSH and LH levels did not differ among the three groups. The number of retrieved oocytes and 2 pronucleus embryos was significantly lower in group A compared with groups B and C. The CPR, IR, MR, and LBR per embryo transfer showed no differences among the three groups. There was no incidence of ovarian hyperstimulation syndrome in group A.

CONCLUSION

The IR, MR, and LBR in the IVM cycles were comparable to those of the GnRH agonist and GnRH antagonist cycles. The IVM protocol, FSH and hCG priming with oocyte retrieval 38 hours later, is an effective ART option that is comparable with conventional IVF for infertile women with PCOS.

Insulin-stimulated glucose uptake occurs in specialized cells within the cumulus oocyte complex

The oocyte exists within the mammalian follicle surrounded by somatic cumulus cells. These cumulus cells metabolize the majority of the glucose within the cumulus oocyte complex and provide energy substrates and intermediates such as pyruvate to the oocyte. The insulin receptor is present in cumulus cells and oocytes; however, it is unknown whether insulin-stimulated glucose uptake occurs in either cell type. Insulin-stimulated glucose uptake is thought to be unique to adipocytes, skeletal and cardiac muscle, and the blastocyst. Here, we show for the first time that many of the components required for insulin signaling are present in both cumulus cells and oocytes. We performed a set of experiments on mouse cumulus cells and oocytes and human cumulus cells using the nonmetabolizable glucose analog 2-deoxy-d-glucose to measure basal and insulin-stimulated glucose uptake. We show that insulin-stimulated glucose uptake occurs in both compact and expanded cumulus cells of mice, as well as in human cumulus cells. Oocytes, however, do not display insulin-stimulated glucose uptake. Insulin-stimulated glucose uptake in cumulus cells is mediated through phosphatidylinositol 3-kinase signaling as shown by inhibition of insulin-stimulated glucose uptake and Akt phosphorylation with the specific phosphatidylinositol 3-kinase inhibitor, LY294002. To test the effect of systemic in vivo insulin resistance on insulin sensitivity in the cumulus cell, cumulus cells from high fat-fed, insulin-resistant mice and women with polycystic ovary syndrome were examined. Both sets of cells displayed blunted insulin-stimulated glucose uptake. Our studies identify another tissue that, through a classical insulin-signaling pathway, demonstrates insulin-stimulated glucose uptake. Moreover, these findings suggest insulin resistance occurs in these cells under conditions of systemic insulin resistance.

A molecular mechanism underlying ovarian dysfunction of polycystic ovary syndrome: hyperandrogenism induces epigenetic alterations in the granulosa cells

The objective of this study was to explore whether hyperandrogenism induces epigenetic alterations of peroxisome proliferator-activated receptor gamma 1 (PPARG1), nuclear corepressor 1 (NCOR1), and histone deacetylase 3 (HDAC3) genes in granulosa cells (GCs) of polycystic ovary syndrome (PCOS) women and whether these alterations are involved in the ovarian dysfunction induced by hyperandrogenism. Thirty-two infertile PCOS women and 147 infertile women with tubal blockage were recruited. PCOS women were divided into the hyperandrogenism (HA) PCOS group (n = 13) and nonhyperandrogenism (N-HA) PCOS group (n = 19). Sixty female Sprague-Dawley rats were used for PCOS model establishment. In GCs of HA PCOS women, PPARG1 mRNA expression was lower, whereas NCOR1 and HDAC3 mRNA expression were higher than N-HA PCOS women and controls (P < 0.05). When all women were divided into successful and failed pregnancy subgroups according to the following clinical pregnancy outcome, we found lower PPARG1 mRNA levels and higher NCOR1 and HDAC3 mRNA levels in the failed subgroup of HA PCOS (P < 0.05). Two hypermethylated CpG sites in the PPARG1 promoter and five hypomethylated CpG sites in the NCOR1 promoter were observed only in HA PCOS women (P < 0.01 to P < 0.0005). The acetylation levels of histone H3 at lysine 9 and p21 mRNA expression were decreased in human GCs treated with dihydrotestosterone in vitro (P < 0.05). PCOS rat models also showed alterations of PPARG1, NCOR1, and HDAC3 mRNA expression and methylation changes of PPARG1 and NCOR1, consistent with the results from humans. Hyperandrogenism induces the epigenetic alterations of PPARG1, NCOR1, and HDAC3 in GCs, which are involved in the ovarian dysfunction of HA PCOS.

Acute fasting decreases the expression of GLUT1 and glucose utilisation involved in mouse oocyte maturation and cumulus cell expansion

Acute fasting impairs meiotic resumption and glucose consumption in mouse cumulus cell and oocyte complexes (COCs). This study examines the effects of acute fasting on the regulation of glucose transporter 1 (GLUT1) expression and glucose consumption in oocyte maturation. Our results indicate that the restriction of glucose utilisation by 2-deoxyglucose (2-DG) mimicked the inhibitory effects of acute fasting on oocyte meiotic resumption and cumulus cell expansion, effects that were rescued by high glucose concentrations in the culture medium. GLUT1 protein levels were higher in cumulus cells compared with oocytes, and GLUT1 expression in COCs increased with FSH treatment in vitro. However, under acute fasting conditions, GLUT1 expression in COCs decreased and the response to FSH disappeared. Exposure to high glucose conditions (27.5 mM and 55 mM), significantly increased both glucose consumption and GLUT1 levels in COCs. Inhibition of GLUT1 function using an anti-GLUT1 antibody significantly inhibited FSH-induced oocyte meiotic resumption. Taken together, these results suggest that acute fasting decreases GLUT1 expression and glucose utilisation, inhibiting the processes of oocyte maturation and cumulus cell expansion.

The impact of obesity on egg quality

Obesity in women is a concern in many countries. This causes numerous health issues; however, this review focuses on the impact of obesity on women's reproduction, and in particular the oocyte. Data from infertility clinics and experimental animal models that address the effects of obesity are presented. Bidirectional communication and metabolic support from the surrounding cumulus cells are critical for oocyte development, and the impact of obesity on these cells is also addressed. Both oocyte maturation and metabolism are impaired due to obesity, negatively impacting further development. In addition to reproductive hormones, obesity induced elevations in insulin, glucose, or free fatty acids, and changes in adipokines appear to impact the developmental competence of the oocyte. The data indicate that any one of these hormones or metabolites can impair oocyte developmental competence in vivo, and the combination of all of these factors and their interactions are the subject of ongoing investigations.

A single early postnatal estradiol injection affects morphology and gene expression of the ovary and parametrial adipose tissue in adult female rats

Events during early life can affect reproductive and metabolic functions in adulthood. We evaluated the programming effects of a single early postnatal estradiol injection (within 3h after birth) in female rats. We assessed ovarian and parametrial adipose tissue morphology, evaluated gene expression related to follicular development and adipose tissue metabolism, and developed a non-invasive volumetric estimation of parametrial adipose tissue by magnetic resonance imaging. Estradiol reduced ovarian weight, increased antral follicle size and number of atretic antral follicles, and decreased theca interna thickness in atretic antral follicles. Adult estradiol-injected rats also had malformed vaginal openings and lacked corpora lutea, confirming anovulation. Estradiol markedly reduced parametrial adipose tissue mass. Adipocyte size was unchanged, suggesting reduced adipocyte number. Parametrial adipose tissue lipoprotein lipase activity was increased. In ovaries, estradiol increased mRNA expression of adiponectin, complement component 3, estrogen receptor α, and glucose transporter 3 and 4; in parametrial adipose tissue, expression of complement component 3 was increased, expression of estrogen receptor α was decreased, and expression of leptin, lipoprotein lipase, and hormone-sensitive lipase was unaffected. These findings suggest that early postnatal estradiol exposure of female rats result in long-lasting effects on the ovary and parametrial adipose tissue at adult age.

The pivotal role of glucose metabolism in determining oocyte developmental competence

The environment that the cumulus oocyte complex (COC) is exposed to during either in vivo or in vitro maturation (IVM) can have profound effects on the success of fertilisation and subsequent embryo development. Glucose is a pivotal metabolite for the COC and is metabolised by glycolysis, the pentose phosphate pathway (PPP), the hexosamine biosynthesis pathway (HBP) and the polyol pathway. Over the course of oocyte maturation, a large proportion of total glucose is metabolised via the glycolytic pathway to provide substrates such as pyruvate for energy production. Glucose is also the substrate for many cellular functions during oocyte maturation, including regulation of nuclear maturation and redox state via the PPP and for the synthesis of substrates of extracellular matrices (cumulus expansion) and O-linked glycosylation (cell signalling) via the HBP. However, the oocyte is susceptible to glucose concentration-dependent perturbations in nuclear and cytoplasmic maturation, leading to poor embryonic development post-fertilisation. For example, glucose concentrations either too high or too low result in precocious resumption of nuclear maturation. This review will discuss the relevant pathways of glucose metabolism by COCs during in vivo maturation and IVM, including the relative contribution of the somatic and gamete compartments of the COC to glucose metabolism. The consequences of exposing COCs to abnormal glucose concentrations will also be examined, either during IVM or by altered maternal environments, such as during hyperglycaemia induced by diabetes and obesity.

Pertinence of apoptosis markers for the improvement of in vitro fertilization (IVF)

In assisted reproductive technology (ART), the pregnancy and birth rates following in vitro fertilization (IVF) attempts are still low. Recently, apoptotic markers have been suggested as new criteria for oocyte and embryo quality selection. Many studies have provided evidence that poor oocyte and embryo quality can be associated with apoptosis. The aim of this review is to summarize our current knowledge on the apoptotic process in oocytes and embryos, and focus on the possibility for using apoptotic markers as a reliable and predictive marker to select competent oocytes and embryos during IVF. Moreover, it is currently accepted that IVF failures, linked to poor embryo quality, are, in part, associated with suboptimal in vitro culture conditions. Here, we also review the current state of knowledge concerning how the genetic control of apoptosis during folliculogenesis and pre-implantation embryonic development is affected by in vitro culture conditions during IVF. In the future, identification of apoptotic markers in ART for oocyte and embryo selection should result in the development of new agonistic or antagonistic molecules of apoptosis by medicinal chemistry.

Follicular fluid content and oocyte quality: from single biochemical markers to metabolomics

The assessment of oocyte quality in human in vitro fertilization (IVF) is getting increasing attention from embryologists. Oocyte selection and the identification of the best oocytes, in fact, would help to limit embryo overproduction and to improve the results of oocyte cryostorage programs. Follicular fluid (FF) is easily available during oocyte pick-up and theorically represents an optimal source on non-invasive biochemical predictors of oocyte quality. Unfortunately, however, the studies aiming to find a good molecular predictor of oocyte quality in FF were not able to identify substances that could be used as reliable markers of oocyte competence to fertilization, embryo development and pregnancy. In the last years, a well definite trend toward passing from the research of single molecular markers to more complex techniques that study all metabolites of FF has been observed. The metabolomic approach is a powerful tool to study biochemical predictors of oocyte quality in FF, but its application in this area is still at the beginning. This review provides an overview of the current knowledge about the biochemical predictors of oocyte quality in FF, describing both the results coming from studies on single biochemical markers and those deriving from the most recent studies of metabolomics.

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

Previous studies have shown that epidermal growth factor (EGF) has the ability to promote in vitro cultured porcine oocyte maturation. However, little is known about the detailed downstream events in EGF-induced meiotic resumption. We designed this study to determine the relationship of EGF, EGFR, phosphatidylinositol 3-kinase (PI3-kinase), MAPK, and germinal vesicle breakdown (GVBD) during oocyte maturation. Our results showed that GVBD in cumulus-enclosed oocytes (CEOs) but not in denuded oocytes (DOs) was induced by EGF in a dose-dependent manner, which indicated that cumulus cells but not oocyte itself were the main target for EGF-induced meiotic resumption. Furthermore, we found that MAPK in cumulus cells rather than in oocyte was activated immediately after EGF administration. To explore whether EGF exerts its functions through MAPK pathway, the activities of EGF receptor (EGFR) and MAPK were inhibited by employing AG1478 and U0126, respectively. Inhibition of MAPK blocked EGF-induced GVBD, whereas inhibition of EGFR prevented MAPK activation. Both AG1478 and U0126 could lead to the failure of EGF-induced GVBD singly. Notably, we found that LY294002, a specific inhibitor of PI3-kinase, effectively inhibited EGF-induced MAPK activation as well as subsequent oocyte meiotic resumption and this inhibition could not be reversed by adding additional EGF. Thus, PI3-kinase-induced MAPK activation in cumulus cells mediated EGF-induced meiotic resumption in porcine CEOs. Together, this study provides evidences demonstrating a linear relationship of EGF/EGFR, PI3-kinase, MAPK and GVBD and presents a relatively definitive mechanism of EGF-induced meiotic resumption of porcine oocyte.

Effect of human granulosa cell co-culture using standard culture media on the maturation and fertilization potential of immature human oocytes

OBJECTIVE

To determine whether culture of immature human oocytes with and without autologous cumulus cells (CC) in standard culture medium would provide additional oocytes for use in IVF procedures.

DESIGN

Prospective study.

SETTING

Hospital-based IVF practice.

PATIENT(S)

Sixty-one women undergoing 62 IVF-embryo transfer procedures between August 2004 and June 2005.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Oocyte maturation after culture with and without CC, oocyte fertilization, and zygote cleavage.

RESULT(S)

Culture with CC did not alter the maturation rate for metaphase I (M I) oocytes to the metaphase II (M II) stage. Germinal vesicle (GV) stage oocytes cultured with CC matured at a significantly higher rate than did GV oocytes cultured without CC. Although acceptable fertilization rates were obtained (62.1%), "usable" embryo yield was very low (13.0%).

CONCLUSION(S)

This study demonstrated good maturation of M I oocytes but poor maturation of GV oocytes in standard culture medium. Of the immature oocytes that did mature, were fertilized, and cleaved to embryos, only a very small number were actually suitable for patient use. Therefore, these extended culturing techniques were inefficient in maturing and providing additional oocytes/embryos for patient use. The use of specialized in vitro maturation medium may improve the utility of this process.

Molecular methods for selection of the ideal oocyte

Some recent strategies for identifying the ideal oocyte for insemination in assisted reproduction techniques are reviewed. Established methods of assessing the female gamete, such as morphological evaluation of oocytes and cytogenetic analysis of polar bodies using fluorescence in-situ hybridization, will soon be joined by more advanced cytogenetic methods such as the use of comparative genomic hybridization to improve understanding of oocyte genetics. It seems likely, however, that the greatest advances will originate from the evolution of molecular genetic technologies. The application of microarray technology to individual oocytes and their associated cumulus cells has recently been accomplished, providing a simultaneous assessment of activity for thousands of genes and revealing potential viability markers. Furthermore, improved equipment and optimized methods of mass spectrometry have provided sufficient sensitivity to allow proteomic profiles to be generated from single oocytes and embryos, while metabolomic investigations have searched for indicators of oocyte/embryo quality in spent culture medium. Techniques of this type may ultimately lead to non-invasive tests for oocyte quality revealing previously hidden information concerning both oocyte and embryo developmental competence. Once fully validated, these new approaches are expected to revolutionize oocyte and embryo selection, leading to improved implantation rates and higher probabilities of success using elective single embryo transfer.

Effects of in vitro oocyte maturation and embryo culture on the expression of glucose transporters, glucose metabolism and insulin signaling genes in rhesus monkey oocytes and preimplantation embryos

Glucose plays a fundamental role during oogenesis and embryogenesis, satisfying the metabolic demands of oocytes and embryos, providing for stored energy reserves in the form of glycogen and supporting nucleotide biosynthesis via the pentose phosphate pathway. Glucose also contributes to the production of amino acids, glycosylated proteins and extracellular components. A detailed understanding of the molecular mechanisms that mediate and regulate glucose uptake and metabolism at different stages of oogenesis and preimplantation embryogenesis could greatly benefit the development of improved methods for in vitro oocyte maturation and in vitro embryo production. Although these processes have been examined in a variety of rodent and agricultural species, detailed information has not yet been described for non-human primates. In this study, we examined the expression of the genes encoding glucose transporters, glucose metabolism enzymes and potential regulators of glucose metabolism in rhesus monkey oocytes and embryos. The data reveal stage-specific regulation of expression of specific types of glucose transporters, stage-specific changes in expression of genes related to different pathways of glucose metabolism and temporal changes in the expression of mRNAs related to insulin signaling. Additionally, the data reveal significant differences in expression of some of these genes in cultured embryos as compared with flushed embryos and between oocytes and embryos obtained following different hormonal stimulation and oocyte maturation protocols.

A comparative analysis of metabolism and viability in porcine oocytes during in vitro maturation

The importance of oocyte quality cannot be overstated, because it impacts all subsequent events during development of the embryo, the fetus and even the resulting offspring. Oocyte metabolism plays a critical role in supporting developmental competence via multiple mechanisms. It is beginning to be understood that metabolic pathways not only affect cytoplasmic maturation but may control nuclear maturation as well. A complete understanding of the precise roles that metabolism plays in determining oocyte quality is crucial for developing efficient in vitro maturation systems to support acquisition of oocyte competence. To date, this pursuit has not been entirely successful. Work in our laboratory on porcine oocyte metabolism has elucidated some of the intricate control mechanisms at work within the oocyte, not only for energy production, but also encompassing progression of nuclear maturation, mitochondrial activity and distribution, and oxidative and ionic stresses. We hypothesize that by utilizing oocyte metabolic data, we can develop more appropriate in vitro maturation systems that result in increased oocyte and embryo developmental competence.

Reduced oxygen concentration improves the developmental competence of mouse oocytes following in vitro maturation

Reduced atmospheric oxygen concentration is beneficial to embryo development; however, optimal oxygen concentration for oocyte maturation remains undetermined. Likewise, there is no consensus of appropriate medium supplementation during maturation. The objective of this study was to determine whether oxygen tension (20% or 5% O2) and epidermal growth factor (EGF) affect oocyte metabolism and subsequent embryo development. Cumulus-oocyte complexes (COCs) were collected from 28-day-old equine chorionic gonadotropin (eCG) primed or unprimed F1 (C57BL/6xCBA) mice. COCs were matured in defined medium in one of four groups: 20% O2, 20% O2 + EGF, 5% O2, 5% O2 + EGF. In vivo matured COCs were also collected for analysis. COCs from unprimed mice, matured in 5% O2 +/- EGF or 20% O2 + EGF had higher metabolic rates than COCs matured in 20% O2 (P < 0.05). COCs from primed mice had higher metabolic rates when matured in the presence of EGF, regardless of oxygen tension (P < 0.01). Oxygen uptake and mitochondrial membrane potential were higher for in vivo matured oocytes and oocytes matured under 5% O2 compared to oocytes matured under 20% O2 (P < 0.05). Blastocyst formation was not different between maturation groups (primed or unprimed); however, embryo cell numbers were 20-45% significantly higher when COCs were matured at 5% O2 (P < 0.05). Results suggest that oocytes matured in physiological concentrations of oxygen have improved development and metabolic activity, more closely resembling in vivo maturation. These findings have implications for oocyte maturation in both clinical and research laboratories.

Metabolic markers of developmental competence for in vitro-matured mouse oocytes

In vitromaturation of oocytes has enormous potential in assisted reproductive technology, but its use has been limited due to insufficient knowledge of oocyte physiology during this dynamic period and lack of an adequate maturation system. The aim of this study was to characterize the metabolic profiles of three groups of oocytes throughout maturation: cumulus–oocyte complexes (COCs), denuded oocytes, and denuded oocytes co-cultured with cumulus cells. Mouse oocytes were collected from 28-day-old unstimulated females and matured in a defined medium. Oocytes were matured individually and transferred into fresh 0.5 μl drops of medium at 4 h intervals until 16 h. Ultramicrofluorimetry was used to quantitate carbohydrate consumption from and metabolite release into the medium. Glucose consumption and lactate production of COCs increased (P< 0.001) over the maturation interval (0–16 h). Glucose consumption by COCs that subsequently fertilized was higher between 8–12 h of maturation than by COCs that did not fertilize (38 versus 29 pmol/COC per h, respectively;P< 0.01). Lactate production by COCs that subsequently fertilized was higher between 8–16 h of maturation, than by oocytes that did not fertilize (8–12 h, 66 versus 46 pmol/COC per h,P< 0.01; 12–16 h, 56 versus 40 pmol/COC per h, respectively;P< 0.05). These data indicate that the final hours of maturation may hold a unique marker of oocyte competence, as during this time fertilizable COCs take up more glucose and produce more lactate than those not subsequently fertilized.

Impaired insulin-dependent glucose metabolism in granulosa-lutein cells from anovulatory women with polycystic ovaries

BACKGROUND

Insulin resistance and hyperinsulinaemia are well-recognized characteristics of anovulatory women with polycystic ovary syndrome (PCOS) but, paradoxically, steroidogenesis by PCOS granulosa cells remains responsive to insulin. The hypothesis to be tested in this study is that insulin resistance in the ovary is confined to the metabolic effects of insulin (i.e. glucose uptake and metabolism), whereas the steroidogenic action of insulin remains intact.

METHODS

Granulosa-lutein cells were obtained during IVF cycles from seven women with normal ovaries, six ovulatory women with PCO (ovPCO) and seven anovulatory women with PCO (anovPCO). Mean body mass index was in the normal range in all three groups. Granulosa-lutein cells were cultured with insulin (1, 10, 100 and 1000 ng/ml) and LH (1, 2.5 and 5 ng/ml). Media were sampled at 24 and 48 h and analysed for glucose uptake, lactate production and (48 h only) progesterone production.

RESULTS

Insulin-stimulated glucose uptake by cells from anovPCO was attenuated at higher doses of insulin (100 and 1000 ng/ml) compared with that by cells from either ovPCO (P=0.02) or controls (P=0.02). Insulin and LH stimulated lactate production in a dose-dependent manner, but insulin-dependent lactate production was markedly impaired in granulosa-lutein cells from anovPCO compared with either normal (P=0.002) or ovPCO (P<0.0001). By contrast, there was no difference in insulin-stimulated progesterone production between granulosa-lutein cells from the three ovarian types.

CONCLUSIONS

Granulosa-lutein cells from women with anovPCOS are relatively resistant to the effects of insulin-stimulated glucose uptake and utilization compared with those from normal and ovPCO, whilst maintaining normal steroidogenic output in response to physiological doses of insulin. These studies support the probability of a post-receptor, signalling pathway-specific impairment of insulin action in PCOS.

Follicle-Stimulating Hormone Affects Metaphase I Chromosome Alignment and Increases Aneuploidy in Mouse Oocytes Matured in Vitro1

Follicle-Stimulating Hormone (FSH) at a wide range of doses is routinely added to culture media during in vitro maturation (IVM) of oocytes, but the effects on oocyte health are unclear. The suggestion that superovulation may cause aneuploidy and fetal abnormalities prompted us to study the potential role of FSH in the genesis of chromosomal abnormalities during meiosis I. Mouse cumulus-oocyte complexes (COCs) isolated from the antral follicles of unprimed, sexually immature B6CBF1 mice were cultured in increasing concentrations of FSH. Following culture, matured oocytes were isolated, spread, stained with DAPI, and the numbers of chromosomes counted. Significantly increased aneuploidy, arising during the first meiotic division, was observed in metaphase II oocytes matured in higher concentrations of FSH (> or =20 ng/ml). The effect of FSH on spindle morphology and chromosome alignment during metaphase I was then explored using immunocytochemistry and three-dimensional reconstruction of confocal sections. High FSH had no effect on gross spindle morphology but did alter chromosome congression during prometaphase and metaphase, with the spread of chromosomes across the spindle at this time being significantly greater in oocytes cultured in 2000 ng/ml compared with 2 ng/ml FSH. Analysis of three-dimensional reconstructions of spindles in oocytes matured in 2000 ng/ml FSH shows that chromosomes are more scattered and farther apart than they are following maturation in 2 ng/ml FSH. These results demonstrate that exposure to high levels of FSH during IVM can accelerate nuclear maturation and induce chromosomal abnormalities and highlights the importance of the judicious use of FSH during IVM.