Rebecca L Robker

University of Adelaide, Tarndarnya, South Australia, Australia

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Publications (79)299.5 Total impact

  • Michelle Lane, Rebecca L Robker, Sarah A Robertson
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    ABSTRACT: At fertilization, the gametes endow the embryo with a genomic blueprint, the integrity of which is affected by the age and environmental exposures of both parents. Recent studies reveal that parental history and experiences also exert effects through epigenomic information not contained in the DNA sequence, including variations in sperm and oocyte cytosine methylation and chromatin patterning, noncoding RNAs, and mitochondria. Transgenerational epigenetic effects interact with conditions at conception to program the developmental trajectory of the embryo and fetus, ultimately affecting the lifetime health of the child. These insights compel us to revise generally held notions to accommodate the prospect that biological parenting commences well before birth, even prior to conception.
    Science (New York, N.Y.). 08/2014; 345(6198):756-760.
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    ABSTRACT: Kit ligand (KITL) is an important granulosa cell-derived growth factor in ovarian folliculogenesis, but its expression and function in human granulosa cells are currently poorly understood. Based on studies performed in animal models, it was hypothesised that KITL gene expression in human granulosa cells is regulated by androgens and/or growth differentiation factor 9 (GDF9). We utilised two models of human granulosa cells, the KGN granulosa tumour cell line and cumulus granulosa cells obtained from preovulatory follicles of women undergoing assisted reproduction. Cells were treated with combinations of 5α-dihydrotestosterone (DHT), recombinant mouse GDF9, and the ALK4/5/7 inhibitor SB431542. KITL mRNA levels were measured by quantitative real-time PCR. No change in KITL mRNA expression was observed after DHT treatment under any experimental conditions, but GDF9 treatment resulted in a significant decrease in KITL mRNA levels in both KGN and cumulus cells. The effect of GDF9 was abolished by the addition of SB431542. These results indicate that KITL is not directly regulated by androgen signalling in human granulosa cells. Moreover, this study provides the first evidence that GDF9 negatively regulates KITL gene expression in human granulosa cells providing new information on the regulation of these important growth factors in the human ovary.
    Endocrine. 07/2014;
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    ABSTRACT: Oviducts play a critical role in gamete and embryo transport, as well as supporting early embryo development. Progesterone receptor (PGR) is a transcription factor highly expressed in oviductal cells, while its activating ligand, progesterone, surges to peak levels as ovulation approaches. Progesterone is known to regulate oviduct cilia beating and muscular contractions in vitro, but how PGR may mediate this in vivo is poorly understood. We used PGR null mice to identify genes potentially regulated by PGR in the oviducts during the periovulatory period. Histologically, oviducts from PGR null mice showed no gross structural or morphological defects compared to normal, littermates. However, microarray analysis of oviducts at 8 h post-hCG revealed over 1000 PGR-dependent genes. Ten genes were selected for validation using reverse-transcription polymerase chain reaction (RT-PCR) based on their potential roles in oocyte/embryo transport and support. Eight genes were confirmed to be down-regulated (Adamts1, Itga8, Edn3, Prlr, Ptgfr, Des, Myocd and Actg2) and one up-regulated (Agtr2) in PGR null oviducts. Expression of these genes was also assessed in oviducts of naturally cycling mice during ovulation, day 1 and day 4 of pregnancy. Adamts1, Itga8, Edn3, Prlr and Ptgfr were significantly up-regulated in oviducts at ovulation/mating. However, most genes showed basal levels of expression at other times. The exceptions were Prlr and Ptgfr which showed pulsatile increases on day 1 and/or day 4 of pregnancy. This is the first, comprehensive study to elucidate putative PGR-regulated genes in the oviduct and reveals key downstream targets potentially mediating oocyte and embryo transport.
    Physiological Genomics 06/2014; · 2.81 Impact Factor
  • Kylie Dunning, Darryl L Russell, Rebecca Robker
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    ABSTRACT: Metabolism and ATP levels within the oocyte and adjacent cumulus cells are associated with oocyte quality and optimal development of a healthy embryo. Lipid metabolism provides a potent source of energy and its importance during oocyte maturation is being increasingly recognised. The triglyceride and fatty acid composition of ovarian follicular fluid has been characterised for many species and is influenced by nutritional status (i.e. dietary fat, fasting, obesity and season) as well as lactation in cows. Lipid in oocytes is primarily triglyceride of specific fatty acids which differ by species, stored in distinct droplet organelles that re-localise during oocyte maturation. The presence of lipids, particularly saturated versus unsaturated fatty acids, in in vitro maturation (IVM) systems affects oocyte lipid content as well as developmental competence. Triglycerides are metabolised by lipases which have been localised to cumulus cells as well as oocytes. Fatty acids generated by lipolysis are further metabolised byβ-oxidation in mitochondria for the production of ATP.β-oxidation is induced in cumulus-oocyte complexes by the LH surge and pharmacological inhibition ofβ-oxidation impairs oocyte maturation and embryo development. Promotingβ-oxidation with L-carnitine improves embryo development many species. Thus fatty acid metabolism in the mammalian cumulus-oocyte complex is regulated by maternal physiological and in vitro environmental conditions; and is important for oocyte developmental competence.
    Reproduction 04/2014; · 3.56 Impact Factor
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    ABSTRACT: In-vitro fertilization (IVF) may influence the metabolic health of children. However, in humans, it is difficult to separate out the relative contributions of genetics, environment, or the process of IVF, which includes ovarian stimulation and embryo culture. Therefore, we examined glucose metabolism in young adult humans and in adult male C57BL/6J mice conceived by IVF versus naturally, under energy balanced and high-fat overfeeding conditions. In humans, peripheral insulin sensitivity, as assessed by hyperinsulinemic-euglycemic clamp (80mU/m(2)/min), was lower in IVF (n=14) versus controls (n=20) after 3 days of an energy-balanced diet (30% fat). In response to 3-days of overfeeding (+1250 kcal/day, 45% fat), there was a greater increase in systolic blood pressure in IVF versus controls (P=0.02). Mice conceived following either ovarian stimulation alone or IVF weighed significantly less at birth versus controls (P<0.01). However, only mice conceived by IVF displayed increased fasting glucose, impaired glucose tolerance and reduced insulin-stimulated Akt phosphorylation in liver following 8 weeks of either chow or high-fat diet (60% fat). Thus, ovarian stimulation impaired fetal growth in mouse, but only embryo culture resulted in changes in glucose metabolism that may increase the risk of developing metabolic diseases later in life, and in both mouse and humans.
    Diabetes 04/2014; · 7.90 Impact Factor
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    ABSTRACT: The fertility of high performance (high milk yield) dairy breeds such as the Holstein within the Australian dairy herd has been on the decline for the past two decades. The 12-month calving interval for pasture-based farming practises results in oocyte maturation coinciding with peak lactation, periods of negative energy balance and energy partitioning for lactation, causing energy deficiency in some organ systems, including the reproductive system. Oocyte developmental competence (the ability to undergo successful fertilisation, embryo development and establishment of pregnancy) is intrinsically linked with the composition of follicular fluid (FF). The aim of this study was to determine if there was a relationship between the fat and carbohydrate levels in plasma and FF and the ability to support in vitro oocyte maturation (IVM). Plasma and FF were collected in vivo from eight Holstein cows between 52-151 days post-partum. Plasma glucose trended (P = 0.072) higher and triglyceride levels were significantly higher than in FF (P < 0.05) but there were no relationships between FF and plasma composition. Glucose FF concentration was negatively related to follicular lactate and NEFA levels and days post-partum. Conversely, FF triglyceride concentrations were positively related to FF NEFA levels and negatively related to milk fat and protein composition. Abattoir-derived cumulus oocyte complexes (COCs) were cultured in either 50% FF (FF-IVM) or 50% plasma (plasma-IVM), with on time embryo development then assessed. While there were no differences between animals, blastocyst rates following FF-IVM were negatively related to plasma glucose and days post-partum and positively related to body condition score (BCS) and plasma NEFA levels. In comparison to previous studies, total NEFA levels in FF were not related to animal parameters and did not influence oocyte developmental competence in vitro. Results from this study suggest that days post-partum and BCS influence carbohydrate metabolism within the follicular environment and this may be attributed to the pasture-based feed system applied in the Australian dairy industry.
    Theriogenology 01/2014; · 2.08 Impact Factor
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    ABSTRACT: The STAT3 transcription factor is a pleiotropic transducer of signalling by hormones, growth factors and cytokines that has been identified in the female reproductive tract from oocytes and granulosa cells of the ovary to uterine epithelial and stromal cells. In the present study we used transgenic models to investigate the importance of STAT3 for reproductive performance in these different tissues. The Cre-LoxP system was used to delete STAT3 in oocytes by crossing Stat3fl/fl with Zp3-cre+ mice, or in ovarian granulosa cells and uterine stroma by crossing with Amhr2-Cre+ mice. Surprisingly, deletion of STAT3 in oocytes had no effect on fertility indicating that the abundance of STAT3 protein in maturing oocytes and fertilized zygotes is not essential to these developmental stages. In Stat3fl/fl;Amhr2-cre+ females impaired fertility was observed through significantly fewer litters and smaller litter size. Ovulation rate, oocyte fertilization and development to blastocyst were unaffected in this line; however, poor recombination efficiency in granulosa cells had yielded no net change in STAT3 protein abundance. In contrast, uteri from these mice showed STAT3 protein depletion selectively from the stomal compartment. A significant reduction in number of viable fetuses on gestational day 18, increased fetal resorptions and disrupted placental morphology were evident causes of the reduced fertility. In conclusion, this study defines an important role for STAT3 in uterine stromal cells during embryo implantation and the development of a functional placenta.
    PLoS ONE 01/2014; 9(7):e101182. · 3.73 Impact Factor
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    ABSTRACT: Fatty acid oxidation is an important energy source for the oocyte; however, little is known about how this metabolic pathway is regulated in cumulus-oocyte complexes. Analysis of genes involved in fatty acid oxidation showed that many are regulated by the luteinizing hormone surge during in vivo maturation, including acyl-CoA synthetases, carnitine transporters, acyl-CoA dehydrogenases and acetyl-CoA transferase, but that many are dysregulated when cumulus-oocyte complexes are matured under in vitro maturation conditions using follicle stimulating hormone and epidermal growth factor. Fatty acid oxidation, measured as production of (3)H2O from [(3)H]palmitic acid, occurs in mouse cumulus-oocyte complexes in response to the luteinizing hormone surge but is significantly reduced in cumulus-oocyte complexes matured in vitro. Thus we sought to determine whether fatty acid oxidation in cumulus-oocyte complexes could be modulated during in vitro maturation by lipid metabolism regulators, namely peroxisome proliferator activated receptor (PPAR) agonists bezafibrate and rosiglitazone. Bezafibrate showed no effect with increasing dose, while rosiglitazone dose dependently inhibited fatty acid oxidation in cumulus-oocyte complexes during in vitro maturation. To determine the impact of rosiglitazone on oocyte developmental competence, cumulus-oocyte complexes were treated with rosiglitazone during in vitro maturation and gene expression, oocyte mitochondrial activity and embryo development following in vitro fertilization were assessed. Rosiglitazone restored Acsl1, Cpt1b and Acaa2 levels in cumulus-oocyte complexes and increased oocyte mitochondrial membrane potential yet resulted in significantly fewer embryos reaching the morula and hatching blastocyst stages. Thus fatty acid oxidation is increased in cumulus-oocyte complexes matured in vivo and deficient during in vitro maturation, a known model of poor oocyte quality. That rosiglitazone further decreased fatty acid oxidation during in vitro maturation and resulted in poor embryo development points to the developmental importance of fatty acid oxidation and the need for it to be optimized during in vitro maturation to improve this reproductive technology.
    PLoS ONE 01/2014; 9(2):e87327. · 3.73 Impact Factor
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    ABSTRACT: Exposure of cumulus-oocyte complexes to the hyperglycaemia mimetic, glucosamine, during in vitro maturation impairs embryo development, potentially through upregulation of the hexosamine biosynthesis pathway. This study examined the effects of in vivo periconception glucosamine exposure on reproductive outcomes in young healthy mice, and further assessed the effects in overweight mice fed a high-fat diet. Eight-week-old mice received daily glucosamine injections (20 or 400mgkg) for 3-6 days before and 1 day after mating (periconception). Outcomes were assessed at Day 18 of gestation. Glucosamine treatment reduced litter size independent of dose. A high-fat diet (21% fat) for 11 weeks before and during pregnancy reduced fetal size. No additional effects of periconception glucosamine (20mgkg) on pregnancy outcomes were observed in fat-fed mice. In 16-week-old mice fed the control diet, glucosamine treatment reduced fetal weight and increased congenital abnormalities, but did not alter litter size. As differing effects of glucosamine were observed in 8-week-old and 16-week-old mice, maternal age effects were assessed. Periconception glucosamine at 8 weeks reduced litter size, whereas glucosamine at 16 weeks reduced fetal size. Thus, in vivo periconception glucosamine exposure perturbs reproductive outcomes in mice, with the nature of the outcomes dependent upon maternal age.
    Reproduction Fertility and Development 02/2013; 25(2):405-16. · 2.58 Impact Factor
  • Kylie R Dunning, Rebecca L Robker
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    ABSTRACT: Successful embryo and fetal development is dependent on the quality of the oocyte from which it was derived. Several studies to date have demonstrated the link between appropriate metabolism and sufficient ATP production with oocyte quality and preimplantation embryo development. Metabolism of fatty acids for the purpose of synthesizing ATP occurs within mitochondria via β-oxidation and entry of fatty acids into this organelle is the rate-limiting step in this process. Transport of activated fatty acids into mitochondria is catalyzed by carnitine palmitoyl transferase-I (CPTI) which also requires the metabolite carnitine. Once inside the mitochondrial matrix, fatty acids are broken down into acetyl CoA molecules which are further metabolized via the TCA cycle and electron transport chain to produce ATP. The potential to improve oocyte quality by modulating fatty acid metabolism and β-oxidation with carnitine in culture media formulations or via dietary supplementation has received little attention. This review summarizes studies to date investigating the developmental importance of β-oxidation through the use of metabolic inhibitors and whether regulation by carnitine, in vitro or in vivo, has beneficial effects on oocyte and embryo development. Overall, there is little evidence to date that dietary carnitine can improve oocyte quality or female fertility; however inclusion of l-carnitine to in vitro oocyte maturation and embryo growth media improves embryo outcomes, most likely by supplying the oocyte and embryo with an essential co-factor required to utilize fatty acids.
    Animal reproduction science 08/2012; 134(1-2):69-75. · 1.56 Impact Factor
  • L K Akison, R L Robker
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    ABSTRACT: Progesterone is critical for successful ovulation in the ovary and for the multi-faceted role of the oviduct in mammalian reproduction. Its effects are mediated by progesterone receptor (PGR), which is highly expressed in the ovary, specifically granulosa cells of preovulatory follicles in response to the luteinizing hormone (LH) surge that occurs just prior to ovulation, and in the oviduct, predominantly luminal epithelial cells but also muscle cells. This review will summarize research which shows that progesterone, via the actions of PGR, plays a key role in the functions of these cells and in the important periovulatory events of oocyte release, acquisition of oocyte developmental competence and oviductal transport of the newly formed embryo. PGR is a nuclear receptor that regulates the expression of many downstream target genes. However, although much is known about its expression characteristics in ovarian and oviductal cells, there is still much to unravel about the mechanisms by which PGR exerts its control over these important reproductive processes, particularly in the oviduct.
    Reproduction in Domestic Animals 08/2012; 47 Suppl 4:288-96. · 1.39 Impact Factor
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    ABSTRACT: While formation of the expanded cumulus matrix and its importance for oocyte maturation and ovulation are well described, its function in these processes remains unknown. The degree of expansion and expression of cumulus matrix genes are positively correlated with oocyte quality, suggesting that this matrix plays a key role in oocyte maturation. Based on recognized filtration properties of analogous matrices, we investigated whether the cumulus matrix acts as a molecular filter by assessing diffusion of fluorescently labeled dextrans (neutral and negatively charged) and hydrophilic (glucose) and hydrophobic (cholesterol) metabolites in cumulus oocyte complexes (COCs). Expanded in vivo-matured COCs resisted absorption of glucose and cholesterol compared to unexpanded COCs. In vitro-matured (IVM) COCs have a pronounced deficiency in cumulus matrix proteins and have poor oocyte quality. Here we demonstrate that IVM cumulus matrix has deficient filtration properties, with dextran and glucose and cholesterol molecules diffusing more readily into IVM than in vivo-matured COCs. Taking the inverse approach, we found that prostaglandin E2 (PGE2), synthesized by cumulus cells, is retained within the matrix of in vivo-matured COCs but IVM COCs have reduced capacity to retain PGE2, secreting significantly more into the medium. This is the first demonstration of a biophysical property of the cumulus matrix. The ability to regulate metabolite supply from the surrounding environment while sequestering vital signaling factors, such as PGE2, is likely to impact oocyte maturation. Thus, IVM may reduce oocyte quality due to dysregulated control of metabolites and signaling molecules.
    Biology of Reproduction 07/2012; 87(4):89. · 4.03 Impact Factor
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    ABSTRACT: In the ovarian follicle, oocyte-secreted factors induce cumulus-specific genes and repress mural granulosa cell specific genes to establish these functionally distinct cell lineages. The mechanism establishing this precise morphogenic pattern of oocyte signaling within the follicle is unknown. The present study investigated a role for heparan sulphate proteoglycans (HSPG) as coreceptors mediating oocyte secreted factor signaling. In vitro maturation of cumulus oocyte complexes in the presence of exogenous heparin, which antagonizes HSPG signaling, prevented cumulus expansion and blocked the induction of cumulus-specific matrix genes, Has2 and Tnfaip6, whereas conversely, the mural granulosa-specific genes, Lhcgr and Cyp11a1, were strongly up-regulated. Heparin also blocked phosphorylation of SMAD2. Exogenous growth differentiation factor (GDF)-9 reversed these heparin effects; furthermore, GDF9 strongly bound to heparin sepharose. These observations indicate that heparin binds endogenous GDF9 and disrupts interaction with heparan sulphate proteoglycan coreceptor(s), important for GDF9 signaling. The expression of candidate HSPG coreceptors, Syndecan 1-4, Glypican 1-6, and Betaglycan, was examined. An ovulatory dose of human chorionic gonadotropin down-regulated Betaglycan in cumulus cells, and this regulation required GDF9 activity; conversely, Betaglycan was significantly increased in luteinizing mural granulosa cells. Human chorionic gonadotropin caused very strong induction of Syndecan 1 and Syndecan 4 in mural granulosa as well as cumulus cells. Glypican 1 was selectively induced in cumulus cells, and this expression appeared dependent on GDF9 action. These data suggest that HSPG play an essential role in GDF9 signaling and are involved in the patterning of oocyte signaling and cumulus cell function in the periovulatory follicle.
    Endocrinology 07/2012; 153(9):4544-55. · 4.72 Impact Factor
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    ABSTRACT: To determine whether the high lipid content of human follicular fluid influences oocyte maturation. Mouse oocytes as substitutes for human oocytes were exposed to follicular fluids of differing lipid content with outcome monitoring. Private infertility clinic and university laboratory. Seventy-four women seeking assisted reproduction, and gonadotropin-stimulated mice. Assay of follicular fluids for triglyceride and free fatty acids, and stimulation of mouse cumulus-oocyte complexes (COCs) to maturity in vitro in the presence of lipid-rich or lipid-poor follicular fluid. Oocyte lipid content, expression of endoplasmic reticulum stress marker genes, and oocyte maturation assessed in mouse COCs exposed to lipid-rich follicular fluid were compared with complexes exposed to lipid-poor follicular fluid and complexes matured in vivo. Follicular fluids were obtained from women of known body mass index undergoing oocyte aspiration at a private infertility clinic, and the follicular fluids were assayed for triglyceride and free fatty acids; those with the highest and lowest levels of these lipids were selected. The mouse COCs exposed to lipid-rich follicular fluid during their maturation had increased oocyte lipid content, induction of endoplasmic reticulum stress markers, and impaired oocyte nuclear maturation. Increased body mass index is associated with elevated triglycerides and free fatty acids in ovarian follicular fluid. Maturation within this lipid-rich environment is detrimental to oocytes.
    Fertility and sterility 03/2012; 97(6):1438-43. · 3.97 Impact Factor
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    ABSTRACT: Fatty acids such as palmitic acid at high levels are known to induce endoplasmic reticulum (ER) stress and lipotoxicity in numerous cell types and thereby contribute to cellular dysfunctions in obesity. To understand the impact of high fatty acids on oocytes, ER stress and lipotoxicity were induced in mouse cumulus-oocyte complexes during in vitro maturation using the ER Ca(2+) channel blocker thapsigargin or high physiological levels of palmitic acid; both of which significantly induced ER stress marker genes (Atf4, Atf6, Xbp1s, and Hspa5) and inositol-requiring protein-1α phosphorylation, demonstrating an ER stress response that was reversible with the ER stress inhibitor salubrinal. Assessment of pentraxin-3, an extracellular matrix protein essential for fertilization, by immunocytochemistry and Western blotting showed dramatically impaired secretion concurrent with ER stress. Mitochondrial activity in oocytes was assessed by 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolylcarbocyanine iodide staining of inner mitochondrial membrane potential, and oocytes matured in thapsigargin or high-dose palmitic acid had significantly reduced mitochondrial activity, reduced in vitro fertilization rates, and were slower to develop to blastocysts. The deficiencies in protein secretion, mitochondrial activity, and oocyte developmental competence were each normalized by salubrinal, demonstrating that ER stress is a key mechanism mediating fatty acid-induced defects in oocyte developmental potential.
    Molecular Endocrinology 03/2012; 26(4):562-73. · 4.75 Impact Factor
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    ABSTRACT: Although current embryo culture media are based on carbohydrate metabolism of embryos, little is known about metabolism of endogenous lipids. L-carnitine is a β-oxidation cofactor absent in most culture media. The objective was to investigate the influence of L-carnitine supplementation on bovine embryo development. Abattoir-derived bovine cumulus oocyte complexes were cultured and fertilized. Post-fertilization, presumptive zygotes were transferred into a basic cleavage medium ± carbohydrates (glucose, lactate and pyruvate) ± 5 mm L-carnitine and cultured for 4 days in vitro. In the absence of carbohydrates during culture, embryos arrested at the 2- and 4-cell stages. Remarkably, +L-carnitine increased development to the morula stage compared to +carbohydrates alone (P < 0.001). The beneficial effects of L-carnitine were further demonstrated by inclusion of carbohydrates, with 14-fold more embryos reaching the morula stage after culture in the +carbohydrates +L-carnitine group compared to the +carbohydrates group (P < 0.05). Whereas there was a trend for +L-carnitine to increase ATP (P = 0.09), ADP levels were higher and ATP: ADP ratio were 1.9-fold lower (main effect, P < 0.05) compared to embryos cultured in -L-carnitine. Therefore, we inferred that +L-carnitine embryos were more metabolically active, with higher rates of ATP-ADP conversion. In conclusion, L-carnitine supplementation supported precompaction embryo development and there was an additive effect of +L-carnitine +carbohydrates on early embryo development, most likely through increased β-oxidation within embryos.
    Theriogenology 02/2012; 77(8):1632-41. · 2.08 Impact Factor
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    ABSTRACT: Ovulation, the release of the oocyte from the ovarian follicle, is initiated by the luteinizing hormone surge. It is clear that highly controlled degradation of the follicle and ovarian wall is required for passage of the oocyte and accompanying cumulus cells from the follicle, but the mechanism has not yet been elucidated. Here we show that cumulus oocyte complexes (COCs) adopt transient adhesive, migratory, and matrix-invading capacities at the time of ovulation. We characterized cell adhesion, migration, and invasion in preovulatory and postovulatory mouse COCs collected over a time course post-human chorionic gonadotropin (hCG) administration. Adhesion of dispersed cumulus cells and intact COCs to extracellular matrix proteins present in the ovarian wall (collagens, laminin, and fibronectin) increased significantly after hCG treatment and declined immediately after ovulation. Cumulus cell migration was low in unexpanded, equine chorionic gonadotropin-only treated COCs, but increased 4, 8, and 10 h post-hCG, reaching a peak at 12 h post-hCG that coincided with ovulation. The ability of cumulus cells to migrate was rapidly diminished in COCs isolated from the oviduct within 2 h postovulation. Cell migration was cumulus cell specific and was not observed in granulosa cells. Invasion through three-dimensional collagen I and matrigel barriers by preovulatory expanded COCs was equivalent to that of a known invasive breast cancer cell line (MB-231). Cumulatively, these results demonstrate that cumulus cells in the expanded COC transition to an adhesive, motile, and invasive phenotype in the periovulatory period that may be required for successful release of the oocyte from the ovary at ovulation.
    Biology of Reproduction 01/2012; 86(4):125. · 4.03 Impact Factor
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    ABSTRACT: Current embryo culture media are based on the carbohydrate metabolism of embryos. However, little is known about the metabolism of endogenous lipids. This is surprising given the high intracellular lipid densities of embryos of some species and the potential for ATP production via β-oxidation. L-carnitine is a β-oxidation co-factor that is absent in most culture media. The aim of this study is to investigate the influence of carnitine supplementation±carbohydrates on bovine embryo development. Abattoir-derived cattle cumulus-oocyte complexes were cultured and fertilised (Sutton-McDowall et al. 2006 Biol. Reprod. 74, 881-888). Post-fertilisation (24h), presumptive zygotes were transferred into an amino acid-free cleavage media±carbohydrates (glucose, lactate and pyruvate) ±5mM carnitine and cultured for 4 days. The absence of carbohydrates during culture resulted in embryos arresting at the 2- and 4-cell stages. Remarkably, +carnitine significantly increased development to the morula stage compared with +carbohydrates alone (20.4±3% vs 4.7±2.5% morula development; P<0.001). The combination of carbohydrates and carnitine supplementation further improved embryo development, with 14-fold more embryos reaching the morula stage after culture in the +carbohydrates +carnitine group compared with the +carbohydrates group (+carbohydrates=3.1±1.9 vs +carbohydrates +carnitine=43.8±9.1% morula development; P<0.05). The beneficial effects of carnitine supplementation on embryo development were reversed when embryos were cultured in presence of etomoxir, a non-reversible inhibitor of the rate-limiting enzyme of β-oxidation (development to 8-cell stage; +carnitine=33.9±8% vs +carnitine +etomoxir=19.2±4.9%; P<0.05). Intracellular lipid content of embryos +carnitine was determined by culturing presumptive zygotes in media -carbohydrates±carnitine for 24h. Lipid content of embryos was determined by measuring BODIPY 493/503 dye fluorescence. Carnitine supplementation reduced fluorescence intensity 1.8-fold (P<0.001). Adenosine triphosphate and ATP:ADP levels were measured in embryos after 24h of culture±carbohydrates±carnitine. While there was a trend for +carnitine to increase ATP levels (P=0.09), ADP levels were higher and ATP:ADP ratio were 1.9-fold lower (main effect, P<0.05) compared with embryos cultured in -carnitine. This indicates +carnitine embryos were more metabolically active, with higher rates of ATP-ADP conversion. We have shown carnitine supplementation supports pre-compaction embryo development and there is an additive effect of +carnitine +carbohydrate on early embryo development. This is most likely through increased β-oxidation levels within embryos. Current disparities between in vivo and in vitro embryo production, in particular increased lipid content (Romek et al. 2010 Theriogenology 74, 265-276) and decreased developmental potential of in vitro-produced embryos, may be an artefact resulting from limited lipid oxidation in vitro.
    Reproduction Fertility and Development 12/2011; 24(1):158-9. · 2.58 Impact Factor
  • Linda L-Y Wu, Robert J Norman, Rebecca L Robker
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    ABSTRACT: Obesity can have detrimental effects on pregnancy rates in natural conceptions and also in women undergoing IVF or intracytoplasmic sperm injection (ICSI). This review summarises the most recent clinical literature investigating whether obesity impacts oocyte quality and early embryo growth. In other tissues, obesity leads to lipotoxicity responses including endoplasmic reticulum stress, mitochondrial dysfunction and apoptosis. Recent reports indicate that lipotoxicity is a mechanism by which obesity may impact oocyte quality.
    Reproduction Fertility and Development 12/2011; 24(1):29-34. · 2.58 Impact Factor
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    ABSTRACT: Oocyte developmental competence is acquired throughout folliculogenesis and is associated with appropriate differentiation and responsiveness to the luteinizing hormone (LH) surge. The recent development of a novel system for culturing ovarian follicles in a three-dimensional alginate matrix shows promise in phenocopying in vivo folliculogenesis. However, oocytes from follicles grown in vitro have a reduced capacity to complete nuclear maturation and be fertilized compared to oocytes matured in vivo. Oocyte metabolism is closely linked with oocyte quality, and we have recently shown that beta-oxidation of lipids is essential for oocyte developmental competence. Thus we investigated whether upregulation of beta-oxidation by treatment with the fatty acid transport cofactor l-carnitine could improve folliculogenesis and developmental competence of mouse follicles following three-dimensional culture. Ovarian hormones (androstenedione, estradiol, and progesterone) and the induction of cumulus matrix proteins (hyaluronan and ADAMTS1) were similar to in vivo follicles, indicating that appropriate differentiation of follicular cells occurs in cultured follicles after an LH/human chorionic gonadotropin (hCG) stimulus. l-carnitine did not alter survival, growth, or differentiation of follicles. However, l-carnitine supplementation significantly increased beta-oxidation, and markedly improved both fertilization rate and blastocyst development. Together, these results show that appropriate responsiveness of the follicle to the LH/hCG surge occurs following three-dimensional follicle culture but limitations on key metabolic requirements remain. l-carnitine supplementation during in vitro follicle culture increased lipid metabolism and improved oocyte developmental competence.
    Biology of Reproduction 05/2011; 85(3):548-55. · 4.03 Impact Factor

Publication Stats

2k Citations
299.50 Total Impact Points

Institutions

  • 2007–2014
    • University of Adelaide
      • • School of Paediatrics and Reproductive Health
      • • Research Centre for Reproductive Health
      Tarndarnya, South Australia, Australia
  • 2011
    • University of Newcastle
      • School of Environmental and Life Sciences
      Newcastle, New South Wales, Australia
  • 2010
    • Sun Yat-Sen University of Medical Sciences
      Shengcheng, Guangdong, China
  • 2004–2007
    • The Queen Elizabeth Hospital
      • Department of Obstetrics and Gynaecology
      Tarndarnya, South Australia, Australia
  • 1997–2007
    • Baylor College of Medicine
      • • Department of Pediatrics
      • • Department of Molecular & Cellular Biology
      Houston, TX, United States
  • 2000
    • Trinity University
      • Department of Biology
      San Antonio, TX, United States