Simulated physiological oocyte maturation (SPOM): a novel in vitro maturation system that substantially improves embryo yield and pregnancy outcomes

BACKGROUND

Oocyte in vitro maturation (IVM) reduces the need for gonadotrophin-induced ovarian hyperstimulation and its associated health risks but the unacceptably low conception/pregnancy rates have limited its clinical uptake. We report the development of a novel in vitro simulated physiological oocyte maturation (SPOM) system.

METHODS AND RESULTS

Bovine or mouse cumulus-oocyte complexes (COCs) were treated with cAMP modulators for the first 1-2 h in vitro (pre-IVM), increasing COC cAMP levels ∼100-fold. To maintain oocyte cAMP levels and prevent precocious oocyte maturation, COCs were treated during IVM with an oocyte-specific phosphodiesterase inhibitor and simultaneously induced to mature with FSH. Using SPOM, the pre-IVM and IVM treatments synergized to increase bovine COC gap-junctional communication and slow meiotic progression (both P < 0.05 versus control), extending the normal IVM interval by 6 h in bovine and 4 h in mouse. FSH was required to complete maturation and this required epidermal growth factor signalling. These effects on COC had profound consequences for oocyte developmental potential. In serum-free conditions, SPOM increased bovine blastocyst yield (69 versus 27%) and improved blastocyst quality (184 versus 132 blastomeres; both P < 0.05 versus standard IVM). In mice, SPOM increased (all P < 0.05) blastocyst rate (86 versus 55%; SPOM versus control), implantation rate (53 versus 28%), fetal yield (26 versus 8%) and fetal weight (0.9 versus 0.5 g) to levels matching those of in vivo matured oocytes (conventional IVF).

CONCLUSIONS

SPOM is a new approach to IVM, mimicing some characteristics of oocyte maturation in vivo and substantially improving oocyte developmental outcomes. Adaption of SPOM for clinical application should have significant implications for infertility management and bring important benefits to patients.

Isolation and properties of cholesterol esterstorage granules from ovarian tissues

Cholesterol ester-storage granules were isolated from luteinized rat ovary and rabbit ovarian interstitial tissue by centrifugal flotation and were investigated with regard to their structure and function. Cholesterol ester, protein, phospholipid and unesterified cholesterol accounted for the dry weight of granules from luteinized rat ovary. The protein and the phospholipid were resistant to removal by washing. Substrate specificities of nucleotide phosphatase and specific radioactivities of lipid-soluble P (determined after administration of [(32)P]P(i)in vivo) were the same in granules and in a microsomal fraction from the same tissue. After administration of [(32)P]P(i)in vivo, luteinizing hormone increased the specific radioactivity of lipid-soluble P in granules, mitochondria and the microsomal fraction. Since granules did not swell in hypo-osmotic media, whereas microsomal particles did, it is suggested that adherent phospholipid and protein in granule suspensions is unlikely to result from contamination with endoplasmic reticulum. Luteinizing hormone administered in vivo increased the phospholipid and unesterified cholesterol contents of isolated granules relative to their cholesterol ester content, and also tended to raise their protein content. This treatment decreased the ability of isolated granules to act as a substrate for cholesterol esterase in vitro and increased the activity of cholesterol esterase. Cycloheximide in vivo also raised the unesterified cholesterol/cholesterol ester ratio of isolated granules, and when administered with luteinizing hormone acted synergistically to bring about a further increase. These results are considered compatible with evidence obtained by microscopy which suggests that granules may be surrounded by a membrane, that they arise by pinching off from the endoplasmic reticulum, and that they shrink on trophic stimulation of the tissue.

131. INDUCED OOCYTE IN VITRO MATURATION (IVM) SUBSTANTIALLY IMPROVES EMBRYO YIELD AND PREGNANCY OUTCOMES

Oocyte maturation in vivo is a highly orchestrated, induced process, whereby 3'-5'-cyclic adenosine monophosphate (cAMP)-mediated meiotic arrest is overridden by the gonadotrophin surge prior to ovulation. However, in vitro matured (IVM) oocytes resume maturation spontaneously hence compromising developmental competence. Hence we hypothesized that establishing an induced system in vitro would synchronise oocyte-somatic cell communication leading to improved oocyte quality. Bovine or mouse oocytes were treated for the first 1-2 h in vitro with the adenylate cyclase activator forskolin and a non-specific phosphodiesterase (PDE) inhibitor, IBMX, which substantially increased cumulus-oocyte complex (COC) cAMP (180 vs. 2 fmol/ COC , treated vs. control, P<0.001) to in vivo physiological levels. To maintain oocyte cAMP levels and prevent precocious oocyte maturation, oocytes were then cultured with an oocyte-specific (type 3) PDE inhibitor, cilostamide. The net effect of this system (“Induced IVM”) was to increase oocyte-somatic cell gap-junctional communication (bovine: 1000±148 vs. 340±73 units; treated vs. control, p<0.05) and to slow meiotic progression through prophase I to metaphase II, extending the normal IVM interval (bovine: 30 vs. 24h, mouse: 22 vs. 18 h; treated vs. control). These effects on oocyte and somatic cell functions had profound consequences for oocyte developmental potential. In bovine, Induced IVM more than doubled embryo yield (69% vs. 27%; treated vs. control, p<0.05). In mouse, Induced IVM increased blastocyst rate (86% vs. 55%; treated vs. control, p<0.05), implantation rate (51 vs. 25%), fetal survival rate (29% vs. 5%) and fetal weight (0.9g vs. 0.5g, p<0.01). All these developmental outcomes in mice were restored, by using Induced IVM, to levels obtained from in vivo matured control oocytes (conventional IVF). In conclusion, Induced IVM mimics some of the characteristics of oocyte maturation in vivo and substantially improves oocyte developmental outcomes. This should lead to an increase in the use of this technique in reproductive biotechnologies.

260. Synergistic effects of cAMP modulating agents in pre-IVM and in IVM on bovine cumulus and oocyte functions

Cyclic AMP plays a crucial role in oocyte maturation. It has been shown that prolonging spontaneous maturation by modulating oocyte cAMP levels during in vitro maturation (IVM) improves developmental outcomes. This study sought to assess the effect of inclusion of cAMP modulators during a pre-IVM phase and during IVM on cumulus cell (CC) and oocyte function. Bovine cumulus-oocyte complexes (COCs) were precultured for 2 h in medium supplemented with/without cAMP modulators: 0.5 mM IBMX and 0.1 mM forskolin (FK). Cyclic AMP in control COCs dropped significantly from 15 ± 4 to 2 ± 1 fmol/COC within 30 min, whereas FK+IBMX during pre-IVM increased levels to 180 ± 19 fmol/COC, which had notable persistent effects on several COC functions throughout IVM. Cyclic AMP modulators delayed oocyte GV progression; after 2 h of pre-IVM, 67 ± 5% were at GVII stage compared (P < 0.0001) to 12 ± 3% in controls, 66 ± 5% of which had progressed to GVIII. This was associated with a significantly higher level of oocyte-CC gap junction mediated communication (1000 ± 148 v. 340 ± 73 units). We next assessed the interaction of cAMP modulators in pre-IVM and IVM (20uM cilostamide) phases. After 9 h of IVM, significantly more oocytes were arrested at GV stage when modulators were present in both pre-IVM and IVM phases, compared with in IVM alone (96 ± 1 v. 74 ± 2%, P < 0.05). Moreover, progression to MII was delayed by modulators in pre-IVM and IVM (24 ± 1, 75 ± 2, 92 ± 1% MII at 20, 24 and 28 h, respectively), compared with in IVM alone (78 ± 1, 95 ± 1, 98 ± 2% MII). After 24 h of IVM, intra-oocyte cAMP levels remained 15-fold higher (P < 0.05) with modulators in both phases compared with in IVM alone. These results show that the efficacy of cAMP modulators during IVM is substantially improved by management of COC cAMP levels during the pre-IVM phase. Such an approach has profound effects on CC and oocyte function, including increasing oocyte-CC communication and delaying meiotic resumption.

Effects of ovarian stimulation, with and without human chorionic gonadotrophin, on oocyte meiotic and developmental competence in the marmoset monkey (Callithrix jacchus)

A reliable ovarian stimulation protocol for marmosets is needed to enhance their use as a model for studying human and non-human primate oocyte biology. In this species, a standard dose of hCG did not effectively induce oocyte maturation in vivo. The objectives of this study were to characterize ovarian response to an FSH priming regimen in marmosets, given without or with a high dose of hCG, and to determine the meiotic and developmental competence of the oocytes isolated. Ovaries were removed from synchronized marmosets treated with FSH alone (50 IU/d for 6 d) or the same FSH treatment combined with a single injection of hCG (500 IU). Cumulus-oocyte complexes (COCs) were isolated from large (>1.5mm) and small (0.7-1.5mm) antral follicles. In vivo-matured oocytes were subsequently activated parthenogenetically or fertilized in vitro. Immature oocytes were subjected to in vitro maturation and then activated parthenogenetically. Treatment with FSH and hCG combined increased the number of expanded COCs from large antral follicles compared with FSH alone (23.5 +/- 9.3 versus 6.4 +/- 2.7, mean +/- S.E.M.). Approximately 90% of oocytes surrounded by expanded cumulus cells at the time of isolation were meiotically mature. A blastocyst formation rate of 47% was achieved following fertilization of in vivo-matured oocytes, whereas parthenogenetic activation failed to induce development to the blastocyst stage. The capacity of oocytes to complete meiosis in vitro and cleave was positively correlated with follicle diameter. A dramatic effect of follicle size on spindle formation was observed in oocytes that failed to complete meiosis in vitro. Using the combined FSH and hCG regimen described in this study, large numbers of in vivo matured marmoset oocytes could be reliably collected in a single cycle, making the marmoset a valuable model for studying oocyte maturation in human and non-human primates.

342 DISTINCT EFFECTS OF FOLLICULAR FLUID ON CUMULUS CELL APOPTOSIS AND PORCINE OOCYTE DEVELOPMENTAL COMPETENCE

Supplementing medium with follicular fluid (FF) during in vitro maturation (IVM) enhances the developmental competence of porcine oocytes, indicating that factors present in FF are beneficial to cytoplasmic maturation. Previous findings suggest that porcine FF contains high levels of superoxide dismutase activity and exerts a beneficial effect on cytoplasmic maturation by protecting oocytes from oxidative stress (Tatemoto et al. 2004 Biol. Reprod. 71, 1150–1157). Since oxidative stress is a potent inducer of apoptosis, the aim of the present study was to examine the temporal effects of FF during IVM on cumulus cell apoptosis and oocyte developmental competence. Ovaries of prepubertal pigs were collected from a local abattoir and antral follicles, 3 to 7 mm in diameter, were aspirated. Cumulus–oocyte complexes (COCs) with at least 3 uniform layers of compact cumulus cells (CCs) were recovered, washed, and transferred to maturation medium (MM) with or without 25% FF. At 22 h of IVM, COCs from each group were washed and transferred to fresh MM with or without 25% FF, forming 4 groups: -FF/-FF, -FF/+FF, +FF/-FF, and +FF/+FF. Cohorts of COCs were TUNEL stained at 22 and 44 h of IVM using the In Situ Cell Death Detection kit (Roche Diagnostics, Castle Hill, NSW, Australia) according to the manufacturer&apos;s instructions, and apoptotic CCs were visualized using confocal microscopy. Oocytes denuded at 44 h, that had a polar body, were treated with ionomycin and 6-dimethylaminopurine to induce parthenogenetic development, and were cultured for 7 days in NCSU-23 medium at 38.5&deg;C in 5&percnt; O2, 5&percnt; CO2, and 90&percnt; N2. Data were subjected to ANOVA and Tukey&apos;s post-hoc test. At 22 h of IVM, the presence of FF reduced the proportion of apoptotic CCs in COCs (2.1&percnt; vs. 4.6&percnt;). COCs matured with FF from 22 to 44 h of IVM had much lower proportions of apoptotic CCs (&plus;FF/&plus;FF: 0.9&percnt;; &minus;FF/&plus;FF: 2.6&percnt;) compared with those matured without FF (&plus;FF/&minus;FF: 10.3&percnt;; &minus;FF/&minus;FF: 17.8&percnt;). The rate of maturation to the metaphase-II stage was greater when oocytes were matured with FF from 0 to 22 h of IVM (&minus;FF/&minus;FF: 68.6&percnt;; &minus;FF/&plus;FF: 72.8&percnt;; &plus;FF/&minus;FF: 89.2&percnt;; &plus;FF/&plus;FF: 86.2&percnt;). Maturation without FF for the entire IVM interval reduced the proportion of activated oocytes that formed blastocysts compared with the other groups (&minus;FF/&minus;FF: 25.1&percnt;; &minus;FF/&plus;FF: 44.6&percnt;; &plus;FF/&minus;FF: 46.6&percnt;; &plus;FF/&plus;FF: 47.3&percnt;). Despite a 4-fold difference in the proportion of apoptotic CCs between COCs of the &plus;FF/&minus;FF and &minus;FF/&plus;FF groups, exposure to FF for the first or second half of IVM was as beneficial to oocyte developmental competence as exposure to FF for the entire IVM interval. This suggests that the protective effect of FF in reducing oxidative stress on oocytes during IVM is distinct from the effect on oocyte developmental competence.

Seminal plasma regulates ovarian progesterone production, leukocyte recruitment and follicular cell responses in the pig

Seminal plasma (SP) acts to influence the uterine endometrium after mating, activating synthesis of embryotrophic cytokines and inflammatory changes that condition the tract for embryo implantation and establishing pregnancy. The objective of this study was to investigate in pigs whether the ovary might also be responsive to SP exposure. Prepubertal gilts were synchronised with exogenous gonadotrophins and received transcervical treatment with pooled boar SP or PBS; then the ovarian tissue was recovered at 34 h (preovulation) and on days 5 and 9 after treatment. The ovarian response was assessed by measuring ovulation rate, number and size of corpora lutea, ovarian leukocyte populations, progesterone production in vivo, as well as responses of retrieved granulosa cells cultured in vitro. In SP-treated gilts, leukocyte recruitment into the ovarian tissues was increased fourfold at 34 h, with macrophages comprising the most abundant cell lineage. There was no effect of SP on the number of oocytes ovulated; however, the weight of corpora lutea was increased in SP-treated gilts. SP also induced an increase in plasma progesterone content seen from day 5 to at least day 9 after treatment. In addition, granulosa cells and thecal tissue retrieved from preovulatory follicles of SP-treated gilts were more responsive in vitro to growth factor- and gonadotrophin-stimulated cell proliferation and progesterone synthesis. These results suggest that uterine exposure to SP influences immune cell trafficking in the ovary and enhances steroidogenesis in early pregnancy. The effects of SP on ovarian function potentially contribute to reproductive success in the pig.

Adipokines: implications for female fertility and obesity

Obesity is associated with a diverse set of metabolic disorders, and has reproductive consequences that are complex and not well understood. The adipose tissue-produced leptin has dominated the literature with regards to female fertility complications, but it is pertinent to explore the likely role of other adipokines--adiponectin and resistin--as our understanding of their biological functions emerge. Leptin influences the developing embryo, the functioning of the ovary and the endometrium, interacts with the release and activity of gonadotrophins and the hormones that control their synthesis. In this review such biological actions and potential roles of the adipokines leptin, adiponectin and resistin are explored in relation to female fertility and the complexity of the obese metabolic state.

Influence of semen on inflammatory modulators of embryo implantation

Insemination transmits to the female reproductive tract constituents of seminal plasma that target uterine epithelial cells to activate a cascade of inflammatory and immunological changes. Experiments in rodents show seminal factor signalling acts to 'condition' the female immune response to tolerate the conceptus, and to organise molecular and cellular changes in the endometrium to facilitate embryo development and implantation. The active factors in seminal plasma are identified as members of the transforming growth factor-beta family, with the relative balance of active moieties influencing the precise character of the female tract response. Experiments in rodents show that disruption of seminal plasma priming causes foetal growth retardation and changes in placental structure, with long-term consequences for the growth of the neonate. Recent studies indicate a similar physiological function and molecular basis for seminal plasma actions in the pig. In gilts, seminal plasma elicits an endometrial response characterised by recruitment of inflammatory leukocytes and induction of several pro-inflammatory cytokines and cyclo-oxygenase-2. The consequences are evident throughout the pre-implantation period of early pregnancy with altered leukocyte populations and cytokine parameters seen for at least 9 days. Exposure to semen also alters the dynamics in pre-implantation embryo development with an increase in the number of embryos and in their viability. Furthermore seminal plasma influences the temporal kinetics of ovulation, corpus luteum development and steroid production in the ovary. Dissecting the actions of seminal plasma may facilitate development of strategies to ensure maximal fertility and reduce embryo mortality in the pig.

Androgens Augment the Mitogenic Effects of Oocyte-Secreted Factors and Growth Differentiation Factor 9 on Porcine Granulosa Cells1

In this study, we test the hypothesis that the growth-promoting action of androgens on granulosa cells requires paracrine signaling from the oocyte. Mural granulosa cells (MGCs) from small antral (1-3 mm) prepubertal pig follicles were cultured in the presence or absence of denuded oocytes (DO) from the same follicles to determine whether mitogenic and/or steroidogenic responses, to combinations of FSH, insulin-like growth factor 1 (IGF1), and dihydrotestosterone (DHT) were influenced by oocyte-secreted factors (OSFs). To further explore the identity of such factors we performed the same experiments, substituting growth differentiation factor 9 (GDF9), a known OSF, for the DO. OSFs and GDF9 both potently enhanced IGF1-stimulated proliferation, and inhibited FSH-stimulated progesterone secretion. Alone, DHT had little effect on DNA synthesis, but significantly enhanced the mitogenic effects of OSFs or GDF9 in the presence of IGF1. Denuded oocytes, GDF9, and DHT independently inhibited FSH-stimulated progesterone secretion, and androgen, together with DO or GDF9, caused the most potent steroidogenic inhibition. Focusing on mitogenic effects, we demonstrate that both natural androgen receptor (AR) agonists, testosterone and DHT, dose-dependently augmented the mitogenic activity of DO or GDF9. Antiandrogen (hydroxyflutamide) treatment, which is used to block androgen receptor activity, opposed the interaction between androgen and GDF9. In conclusion, androgens stimulate porcine MGC proliferation in vitro by potentiating the growth-promoting effects of oocytes or GDF9, via a mechanism that involves the AR. These signaling pathways are likely to be important regulators of folliculogenesis in vivo, and may contribute to the excess follicle growth that is observed in androgen-treated female animals.

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.

254. Effect of donor age and follicle size on oocyte developmental competence in the pig

Oocytes utilised for in vitro embryo production (IVP) are typically derived from 3–8 mm ovarian follicles of slaughtered pre-pubertal pigs. Following in vitro maturation (IVM), pre-pubertal oocytes display lower developmental competence (DC) than adult oocytes. The aim of this study was to determine the proportion of follicles 3, 4, and 5–8 mm in diameter on the surface of pre-pubertal and adult ovaries, and assess DC of corresponding oocytes. Oocytes were matured for 46 h in modified medium 199. Mature oocytes from the three follicle size cohorts were activated with calcium ionophore to assess blastocyst embryo formation rate. Data were subjected to arcsine transformation, ANOVA and the Tukey post-hoc test. Compared with adult ovaries, pre-pubertal ovaries contained a higher proportion of 3 mm follicles (46 ± 4 v. 72 ± 4%, P<0.01), but a lower proportion of 4 mm (33 ± 3 v. 22 ± 3%, P<0.01) and 5–8 mm follicles (21 ± 5 v. 6 ± 2%, P<0.01). Adult oocytes from the three follicle sizes displayed similar DC (41±2% to 47±3%). DC of pre-pubertal oocytes improved with increasing follicle size (3 mm < 4 mm < 5–8 mm; 12±4%, 27±8% and 50±8%, respectively; P < 0.05). In conclusion, the predominance of 3 mm follicles accounts for the low DC of oocytes from pre-pubertal donors compared with adult donors. Further research is required to understand DC acquisition in pre-pubertal pig oocytes from the smaller follicles <5mm in diameter.

253. Calcium ionophore induction of marmoset oocyte activation

The marmoset monkey (Callithrix jacchus) is a valuable model for developing assisted reproductive technologies in humans and endangered primate species. Calcium ionophore treatments have been used to induce parthenogenetic activation in a number of species, but the effectiveness of this reagent in initiating marmoset embryo development has not yet been reported. The aim of this study was to determine the developmental potential of in vitro matured (IVM) marmoset oocytes, following treatment with calcium ionophore. Immature oocytes from large (LA; >1.5 mm) and small (SA; 0.67–1.5 mm) antral follicles were isolated from the ovaries of FSH-primed animals and cultured in modified G2 medium for 26–30 h at 37.0°C in 6% CO2 in air. Meiotically mature oocytes were sequentially incubated with 5 μM ionomycin for 5 min and 2 mM 6-dimethylaminopurine for 3 h and cultured in G1/G2 sequential medium at 37.0°C in 5% O2, 6% CO2, 89% N2 for 10 days. Cumulus cell expansion associated with LA oocytes (n=118) was greater than that of SA oocytes (n=212), as determined using well established classification criteria (2.7±0.1 v. 1.8±0.2; P<0.01). A greater proportion of LA oocytes completed meiosis to the metaphase-II stage compared with SA oocytes (85±7% v. 63±7%; P<0.05). Pronuclear formation was induced at similar rates in mature oocytes of both groups, but the rate of cleavage was higher for LA oocytes compared with SA oocytes (93±6% v. 66±5%; P<0.05). The number of cells per embryo was not different between the groups.This is the first study to demonstrate that calcium ionophore effectively induces parthenogenetic activation in IVM marmoset oocytes. However, the development of parthenotes was limited beyond the 8-cell stage. Further studies are needed to determine the cause of the developmental block.

251. Growth differentiation factor 9 signalling systems regulate marmoset monkey granulosa cell proliferation

This study was conducted to characterize the receptor/signalling system utilized by the oocyte-secreted growth differentiation factor 9 (GDF9) to promote granulosa cell (GC) growth in the marmoset monkey. Seven adult female marmosets were primed with hFSH for 6 days, whole ovaries were removed on day 7, follicles manually excised, and GC collected from 3 size classes: periantral (PA; 0.42–0.66mm), small antral (SA; 0.66–1.5mm) and large antral (LA; >1.5mm). RNA was extracted from oocytes and GC and subjected to RT-PCR using human primers. In all follicle size classes oocytes expressed GDF9 mRNA and GC expressed mRNA for key GDF9 signalling molecules; bone morphogenetic protein receptor II, activin receptor-like kinase (ALK) 5 and Smad 3. To examine the intracellular response to GDF9, cultured GC from LA follicles were transfected with luciferase reporter constructs and treated with growth factors. CAGA-luciferase (Smad 3 pathway) in transfected GC was stimulated by TGFβ1 (18× above control), GDF9 and mouse oocytes (both ~5×), but not by BMP7. Conversely, neither TGFβ1, GDF9 nor oocytes activated BRE-luciferase (Smad 1/5/8 pathway), which was stimulated 30× by BMP7. 3H-thymidine incorporation was used to determine the effects of GDF9 on GC proliferation. Basal incorporation was highly dependent on follicle size, with PA follicles ~10× higher than SA and ~30× higher than LA follicles. GDF9 stimulated 3H-uptake in GC from all sized follicles, most potently in PA and SA cells. The mitogenic effect of GDF9 was amplified by IGF1; ~3× in SA GC and ~5× in LA GC. In contrast, in the presence of FSH or FSH+IGF1, GDF9 did not stimulate GC proliferation. Treatment of GC with an ALK4/5/7 kinase inhibitor, SB431542, antagonized both GDF9 and GDF9+IGF1 mitogenic effects, in a dose-dependent manner. Thus, GDF9 potently stimulates primate GC proliferation utilizing components of the TGFβ signalling system initially identified in rodents.

231. Mouse oocyte paracrine signalling to cumulus cells by TGF-β superfamily molecules is indispensable for cumulus expansion

Oocyte-secreted factors are required for expansion of the mouse cumulus-oocyte complex (COC), which is necessary for ovulation. Members of the transforming growth factor-β (TGF-β) superfamily are prime candidates for the mouse cumulus expansion-enabling factor (CEEF), and we have recently determined that growth differentiation factor 9 (GDF9) alone is not the CEEF. This study was conducted to examine TGF-β superfamily processes regulating cumulus expansion. COCs were collected from eCG-primed mice and the oocyte microsurgically removed to generate oocytectomised (OOX) complexes. An established scoring system was used to measure FSH-induced cumulus expansion; 0 (no expansion) to +4 (maximum expansion). OOX complexes treated with FSH alone failed to expand (score: 0), whereas expansion was significantly (P < 0.05) induced by either GDF9 (score: mean ± SEM, 3.7 ± 0.1), activin A (2.6 ± 0.1), or co-culture with oocytes (3.2 ± 0.2). The type-I receptors for GDF9 and activin are activin receptor-like kinase 5 (ALK5) and ALK4, respectively. We tested the ability of the ALK4/5/7 kinase inhibitor, SB431542, to neutralise cumulus expansion. SB431542 completely neutralised (P < 0.05) the response of OOX complexes to GDF9, activin and oocyte-induced cumulus expansion. SB431542 also neutralised (P < 0.05) COC expansion in a dose dependent manner. Follistatin, an activin antagonist was effective at neutralising the response of OOX complexes to activin (score: 0), but had no significant effect (P > 0.05) on the expansion of OOX complexes co-cultured with oocytes (score: 2.7 ± 0.2). This study provides evidence that activin is not the sole CEEF, but signalling through the ALK4/5/7 pathway is indispensable for mouse cumulus expansion.

270. Androgens augment the mitogenic effects of oocyte-secreted factors and growth differentiation factor 9 on porcine granulosa cells

Androgens, acting directly through the androgen receptor (AR), are thought to promote granulosa cell (GC) growth in vivo, but generally inhibit growth and promote GC differentiation in vitro. We hypothesised that the growth-promoting action of androgens on GC requires paracrine signalling from the oocyte. To test this hypothesis, we cultured mural GC from small antral (1–3mm) pre-pubertal pig follicles in the presence or absence of denuded oocytes (DO) from the same follicles to examine whether mitogenic responses, determined by uptake of tritiated thymidine, to combinations of FSH, insulin like growth factor 1 (IGF1) and dihydrotestosterone (DHT; 500 nM), were influenced by oocyte-secreted factors (OSFs). To further explore the identity of such factors, we performed the same experiments, substituting recombinant mouse growth differentiation factor 9 (GDF9), a known OSF, for the DO. Alone, DHT induced a small (<2-fold), but consistent increase in IGF1-stimulated DNA synthesis. OSFs stimulated DNA synthesis in all experimental combinations, most significantly in the presence of IGF1 (P < 0.0001), and DHT enhanced (P<0.05) the stimulatory effect of OSFs in all instances. Like OSFs, GDF9 substantially increased IGF1-stimulated DNA synthesis (P < 0.0001), and again, DHT enhanced (P > 0.01) this effect. In further experiments, two AR agonists, testosterone (10-1000nM) and DHT (5–500 nM), dose-dependently augmented the mitogenic effect of OSFs or GDF9 in the presence of IGF1. Only the highest doses of androgen had an independent stimulatory effect; lower doses required the presence of an OSF(s). Antiandrogen (hydroxyflutamide) treatment, used to block AR activity, antagonized the androgen X GDF9 interaction. In conclusion, androgens, via activation of the AR, stimulate porcine GC proliferation in vitro by potentiating the growth-promoting effects of oocytes or GDF9. These signalling pathway interactions are likely to be important regulators of folliculogenesis in vivo and may cause the excess follicle growth that is observed in androgen-treated female animals.

Oocyte-somatic cell interactions during follicle development in mammals

Our current perspectives on the relationship between the oocyte and its surrounding somatic cells are changing as we gain a greater understanding of factors regulating folliculogenesis. It is now widely accepted that the oocyte plays a very active role in promoting follicle growth and directing granulosa cell differentiation. The oocyte achieves this, in part, by secreting soluble paracrine growth factors that act on its neighboring granulosa cells, which in turn regulate oocyte development. In preantral follicles, the oocyte directs granulosa cells to regulate oocyte growth, and oocytes may also directly drive follicle growth. In antral follicles, the oocyte governs the behaviour of cells in its immediate vicinity, thereby actively regulating its own microenvironment. As such, the oocyte establishes and maintains the distinct cumulus lineage of granulosa cells. This oocyte-cumulus cell interaction, in general, prevents luteinization of cumulus cells by promoting growth, regulating steroidogenesis and inhibin synthesis, and suppressing luteinizing hormone receptor expression. Conversely, mural granulosa cells in antral follicles, which have no direct physical contact with the oocyte and, presumably, experience a more diffuse concentration of oocyte-secreted factors, proceed to a different phenotype. In the ovulating follicle, oocyte-secreted factors also play vital roles in enabling cumulus cell expansion and regulating extracellular matrix stability, thus facilitating ovulation. The identities of these oocyte-secreted growth factors regulating such key ovarian functions remain unknown, although growth differentiation factor-9 (GDF-9), GDF-9B and/or bone morphogenetic protein-6 (BMP-6) are likely candidate molecules, probably forming complex local interactions with other related members of the transforming growth factor-beta (TGF-beta) superfamily. Elucidating the nature of oocyte-somatic cell interactions at the various stages of follicle development will have important implications for our understanding of factors regulating folliculogenesis, ovulation rate and fecundity.

Effect of Specific Phosphodiesterase Isoenzyme Inhibitors During In Vitro Maturation of Bovine Oocytes on Meiotic and Developmental Capacity1

Compared with oocytes matured in vivo, in vitro-matured oocytes are compromised in their capacity to support early embryo development. Delaying spontaneous in vitro meiotic maturation using specific phosphodiesterase (PDE) isoenzyme inhibitors may permit more complete oocyte cytoplasmic maturation, possibly by prolonging cumulus cell (CC)-oocyte gap junctional communication during meiotic resumption. This study aimed to investigate the effect of the isoenzyme 3- (oocyte) and isoenzyme 4- (granulosa cell) specific PDE inhibitors on the kinetics of in vitro maturation and on subsequent oocyte developmental competence. Cumulus-oocyte complexes from antral bovine follicles were isolated and cultured in the presence of the specific PDE inhibitors milrinone (type 3) or rolipram (type 4) (100 microM). In the presence of FSH, both PDE inhibitors only slightly extended CC-oocyte gap junctional communication over the first 9 h, but they completely blocked meiotic resumption during this period (P < 0.001). The indefinite inhibitory effect of milrinone on meiotic resumption (30% at germinal vesicle stage after 48 h) was overridden by 24 h when treated with FSH, but not with hCG, suggesting a form of induced meiotic resumption. Oocytes treated with FSH with or without either PDE inhibitor were inseminated at either 24, 26, or 28 h. Treated with either the type 3 or type 4 PDE inhibitor significantly (P < 0.05) increased embryo development to the blastocyst stage by 33%-39% (to an average of 52% blastocysts) compared with control oocytes (38%) after insemination at 28 h, and significantly (P < 0.05) increased blastocyst cell numbers when inseminated at 24 h. These results suggest that delayed spontaneous meiotic maturation, coupled with extended gap junctional communication between the CCs and the oocyte has a positive effect on oocyte cytoplasmic maturation, thereby improving oocyte developmental potential.

Changes in ovarian, follicular, and oocyte morphology immediately after the onset of puberty are not accompanied by an increase in oocyte developmental competence in the pig

This study was conducted to determine whether ovarian morphology and developmental competence of in vitro-matured (IVM) oocytes is immediately affected by the onset of puberty in the pig. Ovaries of peri-pubertal pigs were sorted into two groups according to the presence or absence of corpora lutea presence (CL and NCL, respectively. Ovary dimensions, follicle diameter and number, and oocyte diameter (with and without zona pellucidae) were determined. The developmental competence of in vitro-matured oocytes from these two groups was evaluated following parthenogenetic activation and culture in vitro. CL ovaries were significantly (P<0.01) larger than NCL ovaries (width: 22.3+/-0.9 mm versus 15.9+/-0.4 mm, length: 33.2+/-1 mm versus 24.1+/-0.4 mm). Although CL ovaries had fewer antral follicles in total compared with NCL ovaries (21.1+/-1.8 mm versus 46.8+/-2.2 mm), they had a similar number of follicles 3-8mm in diameter. The mean diameter of follicles that were aspirated was greater for CL ovaries than for NCL ovaries (4.5+/-0.1 mm versus 3.3+/-0.02 mm). Oocytes from CL ovaries were greater in diameter compared with those from NCL ovaries (zona retained: 159+/-1.3 microm versus 146.1+/-1.5 microm, zona free: 124.7+/-1.8 microm versus 113.1+/-1.6 microm). No differences were found between oocytes from CL and NCL ovaries for rates of meiotic maturation (91.6+/-3.2% versus 92.4+/-3.2%), cleavage (88.4+/-11% versus 90.7+/-2.6%) and blastocyst formation (21.0+/-3.7% versus 23.7+/-5.7%). Therefore, the onset of puberty coincides with immediate changes in ovarian morphology, increased ovary size, follicle and oocyte diameter, but not with improved oocyte developmental competence. This suggests that the higher developmental competence usually observed in adult oocytes is acquired gradually and requires exposure to multiple estrus cycles.

Seminal plasma regulates endometrial cytokine expression, leukocyte recruitment and embryo development in the pig

In pigs, uterine exposure to the constituents of semen is known to increase litter size but the underlying physiological mechanisms remain undefined. Studies in rodents and humans implicate immune modulating moieties in seminal plasma as likely candidates, acting through enhancing the receptivity of the female tract. In this study, the acute and longer term effects of seminal plasma on cytokine expression and leukocyte abundance in the pig endometrium during early pregnancy have been characterised. The reproductive tracts of gonadotrophin-primed pre-pubertal gilts treated with intrauterine infusions of either pooled seminal plasma or phosphate-buffered saline (PBS) were retrieved at 34 h, or on day 5 and day 9 after treatment. Seminal plasma elicited an endometrial inflammatory infiltrate comprised of predominantly macrophages and major histocompatibility complex class II+-activated macrophages and dendritic cells. The abundance of these cells was greatest at the pre-ovulatory (34 h) time-point and their increase relative to PBS-treated tissues was maintained until day 9 after seminal plasma treatment. Seminal plasma induced the expression of the cytokines, granulocyte macrophage colony-stimulating factor, interleukin-6 and monocyte chemoattractant protein-1, and the eicosanoid-synthesising enzyme cyclo-oxygenase-2. Expression was maximal 34 h after treatment but altered expression patterns as a consequence of seminal plasma induction persisted through early pregnancy. These changes were accompanied by altered dynamics in pre-implantation embryo development with an increase in the number of embryos and in their viability after seminal plasma treatment. Together, these findings implicate factors in seminal plasma in programming the trajectory of uterine cytokine expression and leukocyte trafficking during early pregnancy and in regulating pre-implantation embryo development in the pig.

Interactions Between Androgen and Growth Factors in Granulosa Cell Subtypes of Porcine Antral Follicles1

Androgens acting via the androgen receptor (AR) have been implicated in regulation of folliculogenesis in many animal species. These effects are possibly mediated via enhancement of FSH and/or insulin-like growth factor (IGF)-I activity in granulosa cells, which contain high levels of AR protein. We examined the in vitro effect of dihydrotestosterone (DHT) on DNA synthesis and progesterone secretion by follicular cells in response to FSH and IGF-I, alone or in combination. Cells from separate pools of 1- to 3-mm and 3- to 5-mm antral follicles were aspirated from gilt ovaries and fractioned into mural granulosa cells (MGCs) and cumulus-oocyte complexes (COCs) for subsequent cell culture. Androgen alone or with any combination of mitogen had minimal effect on proliferative and no effect on steroidogenic responses of MGCs from 3- to 5-mm antral follicles. Conversely, in MGCs from 1- to 3-mm follicles, DHT significantly enhanced IFG-I-stimulated proliferation and had variable influence on progesterone secretion. The effects of DHT on proliferative responses of COCs were also dependent on follicle size: DHT significantly augmented either IGF-I-stimulated proliferation (1- to 3-mm follicles) or FSH-stimulated proliferation (3- to 5-mm follicles). However, the steroidogenic responses of all COCs were identical, whereby DHT significantly suppressed progesterone secretion, predominantly in the presence of FSH. Addition of an AR antagonist, hydroxyflutamide, generally reversed the proliferative responses invoked by DHT but not the steroidogenic responses. We conclude that androgen-receptor-mediated activity in granulosa cells of antral follicles is dependent on follicle size, is influenced by proximity of cells to the oocyte, and possibly involves both classic and nonclassic steroid mechanisms.

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.

230.Novel immune modulation to improve reproductive outcomes in pigs

Early embryonic mortality is a major factor limiting litter size and profitability in the pig industry. Pregnancy success requires an immunologically receptive reproductive tract, generated in response to exposure to immune modulating factors in the seminal plasma (SP). Both the short-term pro-inflammatory response of the endometrium to SP and to a novel immune-modulating product, mycobacterial cell wall extract (MCWE; 'Equimune', Bioniche Animal Health) and the reproductive outcomes from a large-scale farrowing trial are described. In the first experiment, 15 Large White gilts (24 weeks of age) were randomly allocated to three intrauterine treatments administered at onset of gonadotrophin-induced oestrus: (1) 80 mL PBS (control); (2) 80 mL SP; or (3) 80 mL PBS containing 500 �g MCWE. Gilts were slaughtered 32–34 h later and reproductive tracts retrieved. Luminal fluid leukocytes were assessed following fixation using DIFF-Quik stain, and indicated the proportion of lymphocytes increased with SP and MCWE treatment compared to the control group (14.0% and 17.0% v. 9.3%; P < 0.05), and the proportion of monocytes decreased (12.3% and 15.0% v. 25.0%; P < 0.05). In the second experiment, Large White or Large White/Landrace crossbred females (n�=�161) were artificially inseminated twice, following standard industry practice, after detection of standing oestrus. Stratified for parity and breed, each was allocated to a treatment group: (a) Control: standard AI dose 1st and 2nd insemination; (b) 500 μg MCWE added to 2nd insemination; or (c) 500 μg MCWE included in the 1st and 2nd insemination. The overall pregnancy rate was 91%, with no significant effect of treatment on litter size, average piglet bodyweight at birth or litter variability. Although the use of MCWE at the time of AI did not improve reproductive outcome, significant potential remains in utilising its immune stimulating properties in 'priming' the reproductive tract, followed by mating at the next oestrus. This approach may improve gilt farrowing rates, thus increase overall herd productivity and efficiency.

Comparison of oocyte factors and transforming growth factor-beta in the regulation of DNA synthesis in bovine granulosa cells

Oocytes are powerful local modulators of follicular cell functions and many of the activities of oocytes are attributed to members of the transforming growth factor-beta (TGF-beta) superfamily. Whilst in the mouse it is known that members of this family are able to mimic many of the effects of oocytes on follicular cells, the relative importance of any of these factors is unknown in bovine follicles. The objectives of this study were to determine if bovine oocytes express and secrete TGF-beta and to compare oocyte-secreted factor(s) to TGF-beta in terms of their capacities to stimulate mural granulosa cell (MGC) DNA synthesis. Bovine ovaries were collected from an abattoir and RNA was extracted from isolated MGC, cumulus cells, cumulus-oocyte complexes and denuded oocytes (DO). Using RT-PCR, all cell types were found to express TGF-beta1 and TGF-beta2 mRNA transcripts. However, no TGF-beta bioactivity could be detected from DO using a sensitive (40 pg/ml) and specific mink lung fibroblast cell bioassay. MGC were cultured with various combinations and doses of TGF-beta2 and DO for 18 h, followed by a 6-h pulse of [3H]-thymidine as an indicator of cellular DNA synthesis. MGC DNA synthesis was stimulated by both TGF-beta2 and DO. However in response to increasing doses of TGF-beta2, [3H]-thymidine levels plateaued at <2-fold above control levels, whereas levels continued to increase over the dose range of DO tested (up to 3.4-fold). Addition of a TGF-beta pan-specific neutralising antibody to MGC cultures eliminated the TGF-beta2-stimulatory effects on DNA synthesis and the TGF-beta2-suppressive effects on progesterone production, but the antibody was unable to neutralise the same responses when induced by DO. These results support a role for TGF-beta1, TGF-beta2 and DO in paracrine/autocrine regulation of bovine granulosa cell function, but indicate that neither TGF-beta1 nor TGF-beta2 can account for the actions of bovine oocytes on granulosa cells.