Haemoglobin expression in in vivo murine preimplantation embryos suggests a role in oxygen-regulated gene expression.

Haemoglobin expression is not restricted to erythroid cells. We investigated the gene expression of the haemoglobin subunits haemoglobin, alpha adult chain 1 (Hba-a1) and haemoglobin, beta (Hbb), 2,3-bisphosphoglycerate mutase (Bpgm) and the oxygen-regulated genes BCL2/adenovirus E1B interacting protein 3 (Bnip3), solute carrier family 2 (facilitated glucose transporter), member 1 (Slc2a1) and N-myc downstream regulated gene 1 (Ndrg1) in the murine preimplantation embryo, comparing invivo to invitro gene expression. Relatively high levels of Hba-a1 and Hbb were expressed invivo from the 2-cell to blastocyst stage; in contrast, little or no expression occurred invitro. We hypothesised that the presence of haemoglobin invivo creates a low oxygen environment to induce oxygen-regulated gene expression, supported by high expression of Slc2a1 and Ndrg1 in invivo relative to invitro embryos. In addition, analysis of an invitro-derived human embryo gene expression public dataset revealed low expression of haemoglobin subunit alpha (HBA) and HBB, and high expression of BPGM. To explore whether there was a developmental stage-specific effect of haemoglobin, we added exogenous haemoglobin either up to the 4-cell stage or throughout development to the blastocyst stage, but observed no difference in blastocyst rate or the inner cell mass to trophectoderm cell ratio. We conclude that haemoglobin in the invivo preimplantation embryo raises an interesting premise of potential mechanisms for oxygen regulation, which may influence oxygen-regulated gene expression.

Oral caffeine administered during late gestation increases gestation length and piglet temperature in naturally farrowing sows.

Selection of sows for large litter size has adverse consequences including lesser and more variable birth weights, reduced piglet viability and greater peri- and post-natal piglet mortality. One approach to improve survival might be to feed caffeine to the sow, which improves piglet viability after induced farrowing, but has not been evaluated in sows which farrow naturally. Large White x Landrace sows were fed 0 (CON: n = 30) or 6 g/day caffeine (CAF: n = 34) with their daily feed from 3 days before expected parturition until farrowing. Numbers of piglets born alive and stillborn, as well as piglet vitality and meconium staining score were recorded at birth. Piglet rectal temperature was measured at 3 and 24 h and piglet survival was recorded through lactation. Compared with CON animals, sows of the CAF group had longer gestations (CON: 115.6 ± 0.3 days; CAF: 116.6 ± 0.3 days, P = 0.01) and piglets of CAF sows had greater rectal temperatures 3 h after birth (CON: 37.6 ± 0.2 °C, CAF 38.0 ± 0.2 °C, P<0.05). Although there was no difference in the stillborn numbers per litter fewer CAF sows delivered stillborn piglets when compared to CON sows (CON: 43.3%, CAF: 20.6%, P = 0.05). Piglet survival to day 18 of lactation was not altered by treatment (CON: 90.4 ± 3.2%, CAF: 92.0 ± 2.4%, P>0.05). The current data suggest that maternal supplementation with caffeine is a promising treatment to prevent premature farrowing and increase piglet temperature at birth, and may decrease the incidence of litters with stillborn piglets.

Pre-birth origins of allergy and asthma.

Allergy is a chronic disease that can develop as early as infancy, suggesting that early life factors are important in its aetiology. Variable associations between size at birth, a crude marker of the fetal environment, and allergy have been reported in humans and require comprehensive review. Associations between birth weight and allergy are however confounded in humans, and we and others have therefore begun exploring the effects of early life events on allergy in experimental models. In particular, we are using ovine models to investigate whether and how a restricted environment before birth protects against allergy, whether methyl donor availability contributes to allergic protection in IUGR, and why maternal asthma during pregnancy is associated with increased risks of allergic disease in children. We found that experimental intrauterine growth restriction (IUGR) in sheep reduced cutaneous responses to antigens in progeny, despite normal or elevated IgE responses. Furthermore, maternal methyl donor supplementation in late pregnancy partially reversed effects of experimental IUGR, consistent with the proposal that epigenetic pathways underlie some but not all effects of IUGR on allergic susceptibility. Ovine experimental allergic asthma with exacerbations reduces relative fetal size in late gestation, with some changes in immune populations in fetal thymus suggestive of increased activation. Maternal allergic asthma in mice also predisposes progeny to allergy development. In conclusion, these findings in experimental models provide direct evidence that a perturbed environment before birth alters immune system development and postnatal function, and provide opportunities to investigate underlying mechanisms and develop and evaluate interventions.

Spontaneous intrauterine growth restriction due to increased litter size in the guinea pig programmes postnatal growth, appetite and adult body composition.

Intrauterine growth restriction (IUGR) and subsequent neonatal catch-up growth are implicated in the programming of increased appetite, adiposity and cardiometabolic diseases. Guinea pigs provide an alternate small animal model to rodents to investigate mechanisms underlying prenatal programming, being relatively precocial at birth, with smaller litter sizes and undergoing neonatal catch-up growth after IUGR. The current study, therefore, investigated postnatal consequences of spontaneous IUGR due to varying litter size in this species. Size at birth, neonatal, juvenile (post-weaning, 30-60 days) and adolescent (60-90 days) growth, juvenile and adolescent food intake, and body composition of young adults (120 days) were measured in 158 male and female guinea pigs from litter sizes of one to five pups. Compared with singleton pups, birth weight of pups from litters of five was reduced by 38%. Other birth size measures were reduced to lesser degrees with head dimensions being relatively conserved. Pups from larger litters had faster fractional neonatal growth and faster absolute and fractional juvenile growth rates (P<0.005 for all). Relationships of post-weaning growth, feed intakes and adult body composition with size at birth and neonatal growth rate were sex specific, with neonatal growth rates strongly and positively correlated with adiposity in males only. In conclusion, spontaneous IUGR due to large litter sizes in the guinea pig causes many of the programmed sequelae of IUGR reported in other species, including human. This may therefore be a useful model to investigate the mechanisms underpinning perinatal programming of hyperphagia, obesity and longer-term metabolic consequences.

The effects of season and moderate nutritional restriction on ovarian function and oocyte nuclear maturation in cycling gilts.

The fertility of female pigs is impaired during summer and in response to restriction of feed intake, resulting in reduced productivity of the breeding herd. This study determined the effect of season and moderate nutritional restriction on ovarian function and oocyte developmental competence of cycling gilts. Eighty prepubescent gilts were used across two seasons-summer (S: January to March) and winter (W: June to August)-and received either a high (2.5× maintenance) or a moderately restricted (1.5× maintenance) feeding level for the first 19 days of their second estrous cycle. On Day 19, ovaries were collected post-slaughter. Diameters of all surface follicles over 1 mm were measured. All follicles ≥4 mm were aspirated and cumulus-oocyte complexes underwent in vitro maturation for ∼44 hours to assess oocyte developmental competence on the basis of metaphase II (MII) attainment. Moderate dietary nutrition reduced daily liveweight gain but did not affect the ovarian follicle population or oocyte developmental competence. The number of large follicles (≥6 mm) was lower during summer (S: 10.7 ± 1.74 vs. W: 15.5 ± 1.15, P < 0.05), as was the proportion of oocytes at the germinal vesicle stage of meiosis (S: 0.06 ± 0.02 vs. W: 0.08 ± 0.02, P < 0.05). However, the proportion of oocytes attaining MII was similar in summer and winter (S: 0.72 ± 0.04 and W: 0.69 ± 0.06, P > 0.05). Intrafollicular concentrations of luteinizing hormone were higher in summer (S: 43.05 ± 6.44 vs. W: 12.05 ± 5.12 ng/mL, P < 0.001), whereas estradiol was lower (S: 1.27 ± 0.36 vs. W: 27.52 ± 5.59 ng/mL, P < 0.001). In conclusion, our data demonstrated that in summer, follicle growth beyond 6 mm is impaired during the periovulatory period, without affecting oocyte meiotic competence. Importantly, these data also demonstrated that ovarian follicle growth and the capacity of oocytes to reach MII in vitro appear unaffected by moderate nutritional restriction during the preceding estrous cycle.

Lactation estrus induction in multi- and primiparous sows in an Australian commercial pork production system.

This study evaluated the effect of full physical boar exposure and split weaning on the incidence of lactation estrus within a large commercial piggery. A total of 299 multiparous (MP; parity 2.5 ± 0.03) and 303 primiparous (PP) sows of Large White × Duroc × Landrace genetics were individually housed in conventional farrowing crates from 1 wk before expected farrowing until weaning on Day 30.7 ± 0.05 postparturition. Before shed entry, sows were allocated randomly within parity to receive either boar exposure (BE; n = 454) or no BE (No BE; n = 149). Sows assigned to receive BE were then allocated to 1 of 2 litter size treatments: litter size unchanged (BE; n = 302) or BE and the litter permanently reduced (split weaned) to 7 piglets (BESPW7; n = 152) on Day 18 of lactation. From Day 18 of lactation until weaning, sows in both BE treatments were taken daily to a detection mating area where they received 15 min of full physical BE and were artificially inseminated at the first observed estrus. Providing sows with BE increased the incidence of lactation estrus, with a further increase observed when litter size was reduced to 7 piglets (16% No BE vs. 62% BE and 75% BESPW7; P < 0.05). Multiparous sows exhibited a greater incidence of lactation estrus than PP sows irrespective of treatment (81 compared to 52%, respectively; P < 0.05). Both MP and PP sows exhibited an increased incidence of lactation estrus when a portion of the litter was removed (MP: 76 vs. 89% and PP: 47 vs. 61%; P < 0.05). Farrowing rates were higher in BE MP sows mated postweaning and all BESPW7 sows mated postweaning when compared to their counterparts mated in lactation (P < 0.05). Percentage live weight loss over the course of lactation was greatest for sows in the No BE compared to the BE and BESPW7 treatments (7.7% ± 0.5 vs. 5.4% ± 0.3 and 4.5% ± 0.4, respectively; P < 0.05). Between Day 17 and weaning, piglets suckling sows in the BESPW7 treatment had a higher average weight gain than piglets suckling sows with a full litter (3.5 ± 0.06 vs. 3.1 ± 0.05 kg; P < 0.05). In conclusion these data suggest that providing MP sows with BE is effective at stimulating a synchronous lactation estrus while PP sows require, in addition to BE, a reduction in suckled litter size to 7 piglets.

Oocyte maturation and embryo survival in nulliparous female pigs (gilts) is improved by feeding a lupin-based high-fibre diet.

Inclusion of high levels of the high-fibre ingredient sugar-beet pulp in pre-mating diets has been shown to increase gonadotrophin concentrations and improve oocyte quality in nulliparous pigs (gilts). This study evaluated the effects of two alternative fibre sources on reproductive performance in gilts. Gilts received one of three diets from 3 weeks before puberty stimulation until Day 19 of the first oestrous cycle: control (39 g kg⁻¹ fibre), bran (500 g kg⁻¹ wheat bran, 65 g kg⁻¹ fibre) or lupin (350 g kg⁻¹ lupin, 118 g kg⁻¹ crude fibre). Diet did not affect circulating LH concentrations or ovarian follicle size. However, a higher percentage of oocytes collected from lupin-supplemented gilts reached metaphase II in vitro compared with those collected from bran-fed or control gilts (89±5% versus 72±5% and 66±5%, respectively; P<0.05). Furthermore, in a second experiment, gilts fed the same lupin-based diet before mating had improved embryo survival (92±5%) on Day 28 after mating compared with control gilts (76±4%; P<0.05). Therefore, feeding a high-fibre diet before mating can improve oocyte quality in gilts without changes in circulating LH, but this effect is dependent on the fibre source.

Maternal low-dose porcine somatotropin treatment in late gestation increases progeny weight at birth and weaning in sows but not in gilts.

Birth weight positively predicts postnatal growth and performance in pigs and can be increased by sustained maternal porcine ST (pST) treatment from d 25 to 100 of pregnancy (term ∼115 d). The objective of this study was to test whether a shorter period of maternal pST treatment in late pregnancy (d 75 to 100) could also increase birth and weaning weights of progeny under commercial conditions. Gilts (parity 0) and sows (parities 2 and 3) were not injected (controls) or injected daily with pST (gilts: 2.5 mg•d(-1), sows: 4.0 mg•d(-1), both ∼13 to 14 µg•kg(-1)•d(-1)) from d 75 to 100 of pregnancy. Litter size and BW were recorded at birth and weaning, and dams were followed through the subsequent mating and pregnancy. Maternal pST injections from d 75 to 100 increased litter average progeny weight at birth (+96 g, P = 0.034) and weaning (+430 g, P = 0.038) in sows, but had no effect on progeny weight in gilts (each P > 0.5). Maternal pST treatment did not affect numbers of live-born piglets and increased numbers of stillborn piglets in sows only (+0.4 pigs/litter, P = 0.034). Maternal pST treatment did not affect subsequent reproduction of dams. Together with our previous data, these results suggest that sustained increases in maternal pST are required to increase fetal and postnatal growth in gilt progeny, but that increasing maternal pST in late pregnancy may only be an effective strategy to increase fetal and possibly postnatal growth in sow progeny.

Maternal responses to daily maternal porcine somatotropin injections during early-mid pregnancy or early-late pregnancy in sows and gilts.

Piglet neonatal survival and postnatal growth and efficiency are positively related to birth weight. In gilts, daily maternal porcine ST (pST) injections from d 25 to 100 (term approximately 115 d), but not d 25 to 50, of pregnancy increase progeny birth weight. Daily maternal pST injections from d 25 to 50 increase fetal weight at d 50 in gilts and sows. We therefore hypothesized that daily pST injections from d 25 to 100, but not d 25 to 50, of pregnancy would increase birth weight similarly in both parities. Landrace x Large White gilts and sows were uninjected (controls) or were injected daily with pST (gilts: 2.5 mg/d; sows: 4.0 mg/d, each approximately 15 microg of pST/kg per day) from d 25 to 50 or 100 of pregnancy. Litter size and BW were recorded at birth, midlactation, and weaning. Dams were followed through the subsequent mating and pregnancy. Maternal pST injections from d 25 to 100, but not d 25 to 50, increased mean piglet birth weight by 11.6% in sows (P 0.1) the weaning-remating interval, conception rate, or subsequent litter size. Greater pST-induced birth weight increases in sows than in gilts may mean that underlying metabolic or placental mechanisms for pST action are constrained by maternal competition for nutrients in rapidly growing gilts.

Beyond oxygen: complex regulation and activity of hypoxia inducible factors in pregnancy.

In the first trimester the extravillous cytotrophoblast cells occlude the uterine spiral arterioles creating a low oxygen environment early in pregnancy, which is essential for pregnancy success. Paradoxically, shallow trophoblast invasion and defective vascular remodelling of the uterine spiral arteries in the first trimester may result in impaired placental perfusion and chronic placental ischemia and hypoxia later in gestation leading to adverse pregnancy outcomes. The hypoxia inducible factors (HIFs) are key mediators of the response to low oxygen. We aimed to elucidate mechanisms of regulation of HIFs and the role these may play in the control of placental differentiation, growth and function in both normal and pathological pregnancies. The Pubmed database was consulted for identification of the most relevant published articles. Search terms used were oxygen, placenta, trophoblast, pregnancy, HIF and hypoxia. The HIFs are able to function throughout all aspects of normal and abnormal placental differentiation, growth and function; during the first trimester (physiologically low oxygen), during mid-late gestation (where there is adequate supply of blood and oxygen to the placenta) and in pathological pregnancies complicated by placental hypoxia/ischemia. During normal pregnancy HIFs may respond to complex alterations in oxygen, hormones, cytokines and growth factors to regulate placental invasion, differentiation, transport and vascularization. In the ever-changing environment created during pregnancy, the HIFs appear to act as key mediators of placental development and function and thereby are likely to be important contributors to both normal and adverse pregnancy outcomes.

Oxygen concentration during mouse oocyte in vitro maturation affects embryo and fetal development.

BACKGROUND: Little is known of how the oxygen environment in the ovarian follicle affects oocyte and embryo development, but this has an important impact on the conditions used for in vitro maturation (IVM) of oocytes. We investigated the effect of varying oxygen concentrations during IVM on subsequent pre and post-implantation development. METHODS: IVM of mouse cumulus-oocyte complexes (COCs) was performed under 2, 5, 10 or 20% O(2) (6% CO(2), balance N(2)). In vivo-matured COCs were collected post ovulation. Embryos were generated by IVF and culture. Blastocyst development, cell number and apoptosis were assessed, and fetal and placental outcomes analysed following embryo transfer at day 18 of pregnancy. RESULTS: Oxygen concentration during IVM did not affect oocyte maturation or subsequent fertilization, cleavage and blastocyst development rates. Maturation of oocytes under 2% O(2) increased blastocyst trophectoderm cell number compared with all groups and numbers at 5% were higher than 20% (both P < 0.05). Percentage of apoptotic cells was increased in blastocysts developed from 2% O(2)-matured oocytes, compared with maturation at 5% O(2) or in vivo (P < 0.05). Rates of embryo implantation and development into a viable fetus were not altered by IVM oxygen. However, fetal weight was reduced following oocyte maturation at 5% O(2) compared wiht 20% O(2) and maturation at 5% O(2) also reduced placental weight, when compared with in vivo-matured oocytes (both P < 0.05). CONCLUSIONS: Level of O(2) exposure during oocyte maturation can alter the cellular composition of blastocysts, but these changes in cell number do not correlate with the altered fetal and placental outcomes after transfer.

Complex interactions between hypoxia inducible factors, insulin-like growth factor-II and oxygen in early murine trophoblasts.

The human first trimester placenta experiences a low oxygen environment. The hypoxia inducible factors (HIFs) mediate the response to low oxygen, inducing genes such as insulin-like growth factor (IGF)-II. Interestingly, IGF-II has been shown to promote placental growth and function. Currently, the interaction between oxygen, IGF-II and HIFs in the regulation of trophoblast behaviour are unclear. Murine implantation sites from days 5.5-10.5 were collected for immunohistochemical analyses. Use of the hypoxia marker pimonidazole indicated that the early mouse implantation site is exposed to low oxygen levels similar to those seen in the early human placenta. HIF-1alpha protein immunostaining was also observed in the implantation site. Culturing murine ectoplacental cones in decreasing oxygen concentrations (20%, 5% and 1% O(2)), either with or without the addition of IGF-II, induced complex responses by trophoblasts in terms of their migration and differentiation. Following 3 days exposure to low oxygen there was reduced EPC outgrowth, reduced Igf2 and increased Tpbp mRNA levels, suggesting commitment to the spongiotrophoblast lineage. In addition, Hif-1alpha mRNA levels were decreased, whilst Hif-2alpha mRNA was unchanged. This decrease in Hif-1alpha may be due to the observed increase in antisense (as) Hif-1alpha mRNA levels in 1% cultures. Furthermore, expression of Hif-2alpha and the HIF target genes: asHif-1alpha, Vegf and Slc2a1 were reduced under low oxygen with the addition of IGF-II. In conclusion, Hif-1alpha and Hif-2alpha are differentially regulated by oxygen and IGF-II in cultured trophoblast cells and asHif-1alpha may mediate the response to prolonged hypoxia in murine trophoblasts.

Regulation of gene expression in bovine blastocysts in response to oxygen and the iron chelator desferrioxamine.

Low (2%) oxygen conditions during postcompaction culture of bovine blastocysts improve embryo quality and are associated with small increases in the expression of glucose transporter 1 (SLC2A1), anaphase promoting complex (ANAPC1), and myotrophin (MTPN), suggesting a role for oxygen in the regulation of embryo development, mediated through oxygen-sensitive gene expression. However, bovine embryos, to at least the blastocyst stage, lack detectable levels of the key regulator of oxygen-sensitive gene expression, hypoxia-inducible 1 alpha (HIF1A), while the less well-characterized HIF2 alpha protein is readily detectable. Here we report that other key HIF1 regulated genes are not significantly altered in their expression pattern in bovine blastocysts in response to reduced oxygen concentrations postcompaction-with the exception of lactate dehydrogenase A (LDHA), which was significantly increased following 2% oxygen culture. Antioxidant enzymes have been suggested as potential HIF2 target genes, but their expression was not altered following low-oxygen culture in the bovine blastocyst. The addition of desferrioxamine (an iron chelator and inducer of HIF-regulated gene expression) during postcompaction stages significantly increased SLC2A1, LDHA, inducible nitric oxide synthase (NOS2A), and MTPN gene expression in bovine blastocysts, although development to the blastocyst stage was not significantly affected. These results further suggest that expression of genes, known to be regulated by oxygen via HIF-1 in somatic cells, is not influenced by oxygen during preimplantation postcompaction bovine embryo development. Oxygen-regulated expression of LDHA and SLC2A1 in bovine blastocysts suggests that regulation of these genes may be mediated by HIF2. Furthermore, the effect of a reduced-oxygen environment on gene expression can be mimicked in vitro through the use of desferrioxamine. These results further support our data that the bovine blastocyst stage embryo is unique in its responsiveness to oxygen compared with somatic cells, in that the lack of HIF1-mediated gene expression reduces the overall response to low (physiological) oxygen environments, which appear to favor development.

Differential expression of oxygen-regulated genes in bovine blastocysts.

Low oxygen conditions (2%) during post-compaction culture of bovine blastocysts improve embryo quality, which is associated with a small yet significant increase in the expression of glucose transporter 1 (GLUT-1), suggesting a role of oxygen in embryo development mediated through oxygen-sensitive gene expression. However, bovine embryos to at least the blastocyst stage lack a key regulator of oxygen-sensitive gene expression, hypoxia-inducible factor 1alpha (HIF1alpha). A second, less well-characterized protein (HIF2alpha) is, however, detectable from the 8-cell stage of development. Here we use differential display to determine additional gene targets in bovine embryos in response to low oxygen conditions. While development to the blastocyst stage was unaffected by the oxygen concentration used during post-compaction culture, differential display identified oxygen-regulation of myotrophin and anaphase promoting complex 1 expression, with significantly lower levels observed following culture under 20% oxygen than 2% oxygen. These results further support the hypothesis that the level of gene expression of specific transcripts by bovine embryos alters in response to changes in the oxygen environment post-compaction. Specifically, we have identified two oxygen-sensitive genes that are potentially regulated by HIF2 in the bovine blastocyst.

Late pregnancy increases hepatic expression of insulin-like growth factor-I in well nourished guinea pigs.

Blood IGF-I concentrations are persistently elevated throughout pregnancy in humans and guinea pigs and may regulate substrate partitioning between mother and conceptus. In the guinea pig, liver and adipose tissue have recently been suggested to contribute to the increased levels of circulating IGF-I in mid-pregnancy, but whether this persists in late pregnancy in undernutrition is not known. Therefore the effect of pregnancy and undernutrition on circulating IGF-I and hepatic expression of IGF-I in late gestation in the guinea pig was examined. Female guinea pigs (Cavia porcellus) were fed ad libitum throughout pregnancy or 70% of ad libitum intake for 28 days prior to and throughout pregnancy (term is 69 d). Non-pregnant animals were maintained for 88 days on the same diets. Plasma IGF-I was measured by RIA after molecular sieving chromatography at low pH. Abundances of IGF-I and beta-actin mRNA in maternal liver were quantified by digoxigenin-ELISA after RT PCR. Late pregnancy increased both the concentration of IGF-I protein (p<0.001) in plasma and the relative abundance of liver IGF-I mRNA (p<0.001) in ad libitum fed, but not in feed restricted pregnant guinea pigs. The concentration of IGF-I protein in plasma correlated positively with the relative abundance of IGF-I mRNA in liver overall (p<0.002), suggesting the liver as a major source of endocrine IGF-I in late pregnant guinea pigs. This study demonstrates that hepatic expression of IGF-I remains elevated during late pregnancy in the well fed guinea pig, which is in contrast to that observed in other non-human species.

Effects of recombinant human follicle-stimulating hormone on embryo development in mice.

We have developed a protocol using recombinant human follicle-stimulating hormone (rhFSH) to induce ovarian stimulation in the mouse to investigate its impact on preimplantation embryo development. Embryos were collected from adult female C57Bl/6 x CBA F1 mice treated with rhFSH (0, 2.5, 5.0, 10.0, or 20.0 IU) or 5 IU equine chorionic gonadotropin (eCG). Embryos were also recovered from nontreated control mice. Embryos were cultured in vitro for 88 h, and the stage of development was morphologically assessed. The allocation of cells to the inner cell mass or trophectoderm of blastocysts was determined by differential nuclear staining. The expression of insulin-like growth factor 2 (IGF-II), the insulin-like growth factor receptor (IGF-II receptor), and vascular endothelial growth factor (VEGF) in blastocysts was measured by real-time RT-PCR. Blastocyst development was reduced in the 10 (72.3 +/- 5.1%) and 20 (77.3 +/- 5.6%) IU rhFSH groups compared with control embryos (96.7 +/- 1.0%). The number of inner cell mass cells was reduced (P < 0.001) in the 5, 10, and 20 IU rhFSH groups and the eCG group compared with control embryos. We did not find any effect of rhFSH treatment on IGF-II, IGF-II receptor, or VEGF expression in blastocysts compared with the control group. eCG treatment, however, significantly increased the expression of IGF-II in blastocysts. These results indicate that ovarian stimulation with rhFSH impairs the in vitro development of preimplantation mouse embryos, and these results may have potential implications for clinical ovarian stimulation during infertility treatment and subsequent embryo quality.

Oxygen-regulated gene expression in bovine blastocysts.

Oxygen concentrations used during in vitro embryo culture can influence embryo development, cell numbers, and gene expression. Here we propose that the preimplantation bovine embryo possesses a molecular mechanism for the detection of, and response to, oxygen, mediated by a family of basic helix-loop-helix transcription factors, the hypoxia-inducible factors (HIFs). Day 5 compacting bovine embryos were cultured under different oxygen tensions (2%, 7%, 20%) and the effect on the expression of oxygen-regulated genes, development, and cell number allocation and HIFalpha protein localization were examined. Bovine in vitro-produced embryos responded to variations in oxygen concentration by altering gene expression. GLUT1 expression was higher following 2% oxygen culture compared with 7% and 20% cultured blastocysts. HIF mRNA expression (HIF1alpha, HIF2alpha) was unaltered by oxygen concentration. HIF2alpha protein was predominantly localized to the nucleus of blastocysts. In contrast, HIF1alpha protein was undetectable at any oxygen concentration or in the presence of the HIF protein stabilizer desferrioxamine (DFO), despite being detectable in cumulus cells following normal maturation conditions, acute anoxic culture, or in the presence of DFO. Oxygen concentration also significantly altered inner cell mass cell proportions at the blastocyst stage. These results suggest that oxygen can influence gene expression in the bovine embryo during postcompaction development and that these effects may be mediated by HIF2alpha.

Effect of the oxidative phosphorylation uncoupler 2,4-dinitrophenol on hypoxia-inducible factor-regulated gene expression in bovine blastocysts.

In cattle embryos, development to the blastocyst stage is improved in the presence of 10 micro;m 2,4-dinitrophenol (DNP), an uncoupler of oxidative phosphorylation, coincident with an increase in glycolytic activity following embryonic genome activation. The present study examined redox-sensitive gene expression and embryo development in response to the addition of DNP post-compaction. 2,4-Dinitrophenol increased the expression of hypoxia-inducible factor 1alpha and 2alpha (HIF1alpha, HIF2alpha) mRNA. Although HIF1alpha protein remained undetectable in bovine blastocysts, HIF2alpha protein was localised within the nucleus of trophectoderm and inner cell mass (ICM) cells of blastocysts cultured in the presence or absence of DNP, with a slight increase in staining evident within the ICM in blastocysts cultured in the presence of DNP. However, the expression of GLUT1 and VEGF mRNA, genes known to be regulated by HIFs, was unaffected by the addition of DNP to the culture. Although the development of Grade 1 and 2 blastocysts was unaltered by the addition of DNP post compaction in the present study, a significant increase in the proportion of ICM cells was observed. Results indicate that 10 microm DNP improves the quality of bovine embryos, coincident with increased HIF2alpha protein localisation within ICM cells and increased HIFalpha mRNA levels. Therefore, the results demonstrate redox-regulated expression of HIF2.

Influence of oocyte-secreted factors and culture duration on the metabolic activity of bovine cumulus cell complexes.

Intracellular communication between the cumulus cell complex and the oocyte is essential for numerous processes during oocyte maturation. The aim of this study was to determine the interaction between oocyte-secreted factors and the metabolic activity of bovine cumulus cell complexes during in vitro maturation (IVM). Cumulus-oocyte complexes (COCs) were aspirated from ovaries derived from an abattoir and divided into four treatment groups: (i) intact COCs, (ii) oocytectomized complexes (OOX), in which the ooplasm was microsurgically removed, (iii) OOX co-cultured with denuded oocytes (OOX+DO) and (iv) DO. The complexes were cultured individually in IVM media. After 0-4, 10-14 and 20-24 h of culture, the utilization of oxygen, glucose, pyruvate and L-lactate by the complexes was measured. The metabolic activity of the DO was undetectable. There were no significant differences in metabolic measurement among any of the treatment groups, indicating that the metabolism of the cumulus complex is not affected by the presence of the oocyte. When metabolic activity for the complexes was analysed relative to time in culture, there was an approximate twofold increase in the consumption of oxygen, glucose and pyruvate over the 24 h period (P<0.05), although production of L-lactate remained constant. The relationship between total glucose uptake and L-lactate production indicated that the majority of glucose consumed at the start of culture was being utilized via glycolysis, but by the cessation of the maturation period, there was significant utilization of glucose elsewhere, possibly for the formation of cumulus extracellular matrix. These results indicate that metabolism of COC does not reflect biochemical activity of the oocyte. Nevertheless, the metabolic requirements of the COC increase throughout maturation.

Circulating insulin-like growth factor (IGF)-I and IGF binding proteins -1 and -3 and placental development in the guinea-pig.

Restricting maternal nutrition before and throughout pregnancy in the guinea-pig restricts foetal growth in part by altering placental structural determinants of substrate transfer function. The insulin-like growth factors have been implicated in mediating these changes. To assess the role of IGF-I in placental adaptation to maternal undernutrition, we examined the associations of circulating IGF-I and IGF binding proteins -1, -3 and -4 in the mother with placental structural development. In both mid- and late pregnancy, maternal food restriction reduced maternal plasma IGF-I by 56 per cent (P<0.0005) and 50 per cent (P<0.0005) respectively, and plasma IGFBP-3 by 47 per cent (P=0.03) and 55 per cent (P=0.002), respectively. Maternal plasma IGFBP-4 was reduced by 45 per cent (P=0.041) in food restricted guinea-pigs in mid-pregnancy but not late in pregnancy, while IGFBP-1 was unaltered at both stages. Late in pregnancy, food restriction reduced the ratio of maternal circulating IGF-I to IGFBP-1 by 52 per cent (P=0.011) and increased the ratio of IGF-I to IGFBP-3 in maternal plasma by 10 per cent (P=0.011). The relationships between the maternal IGF axis and structural correlates of placental function were assessed using pooled data from both ad libitum fed and food restricted animals. In mid-pregnancy, the volume density of the maternal blood space in the placental labyrinth correlated positively with both maternal plasma IGF-I and IGFBP-3, while maternal blood space volume correlated negatively with maternal plasma IGFBP-1. In late pregnancy, placental weight correlated positively with both maternal plasma IGF-I and IGFBP-4, while the surface area of syncytiotrophoblast and weight of trophoblast correlated positively, and mean syncytiotrophoblast thickness negatively, with maternal plasma IGF-I. Late in pregnancy, the volume density and weight of syncytiotrophoblast, the surface density and total surface area of trophoblast and the volume of the maternal blood space each correlated positively, and syncytiotrophoblast thickness correlated negatively with maternal plasma IGFBP-3. Concomitantly, placental weight, placental diameter, placental volume, volume density and weight of syncytiotrophoblast, weight of foetal capillaries, syncytiotrophoblast surface density and total syncytiotrophoblast surface area in the placental labyrinth, each correlated positively with the ratio of IGF-I to IGFBP-1 in maternal plasma, while syncytiotrophoblast thickness correlated negatively with this ratio. In late pregnancy therefore, increased trophoblast abundance and placental vascularity, and a reduced barrier to diffusion between maternal and foetal blood, occurs in association with increased abundance of IGF-I and its major carrier, IGFBP-3, and a reduction in that of IGFBP-1 in maternal blood in the guinea-pig. This suggests that systemic IGF-I and modulation of its bioavailability by IGFBPs -1 and -3 within the mother may influence placental growth and differentiation in an endocrine fashion, particularly when nutrition is limited.