Microtubular Assessment of C6 Rat Glioma Cell Spheroids Developed in Transparent Liquid Marbles or Hanging Drops

Glioblastoma is a brain tumour frequently used as an experimental model to exploit innovative therapeutic approaches due to its high lethality and refractoriness to therapies. Part of these innovative anticancer therapies address cytoskeletal microtubules (MTs) since specific tubulin post-translational modifications (PTMs) are considered markers of tumour plasticity. In vitro studies, which traditionally employ two-dimensional (2D) culture systems, are now being replaced by three-dimensional (3D) systems that more closely mimic in vivo physiological conditions and allow a better understanding of the signalling between cells. In this work, we compared 2 liquid base 3D methods for the generation of spheroids from C6 rat glioma cells (RGCs) using 30 µL of liquid marble (LM) or the hanging drops (HDs), which contained 2 different cell numbers (5000 or 15,000). After 24 or 48 h of in vitro culture (IVC), the morphology of the spheroids was observed and the behaviour of the two main tubulin PTMs, tyrosinated α-tubulin (Tyr-T) and acetylated α-tubulin (Ac-T), was evaluated by fluorescence and Western blot (WB). RGCs spontaneously formed spherical agglomerates more rapidly in the LM than in the HD system. Cell density influenced the size of the spheroids, which reached a larger size (> of 300 µm Ø), with 15,000 cells compared to 5000 cells (150 µm Ø). Moreover, an increase in Tyr-T and Ac-T was observed in both the HD and LM system from 24 to 48 h, with the highest values shown in the 48 h/LM spheroids of 5000 cells (p < 0.05). In conclusion, by comparing the morphology and microtubular architecture of spheroids from C6 rat glioma cells developed by LM or HD methodology, our findings demonstrate that the use of a fumed silica microbioreactor boosts the induction and maintenance of a high plasticity state in glioma cells. RGCs cultured in LM express levels of tubulin PTMs that can be used to evaluate the efficacy of new anticancer therapies.

Oocyte aging: looking beyond chromosome segregation errors

The age-associated decline in female fertility is largely ascribable to a decrease in oocyte quality. This phenomenon is multifaceted and influenced by numerous interconnected maternal and environmental factors. An increase in the rate of meiotic errors is the major cause of the decline in oocyte developmental competence. However, abnormalities in the ooplasm accumulating with age - including altered metabolism, organelle dysfunction, and aberrant gene regulation - progressively undermine oocyte quality. Stockpiling of maternal macromolecules during folliculogenesis is crucial, as oocyte competence to achieve maturation, fertilization, and the earliest phases of embryo development occur in absence of transcription. At the same time, crucial remodeling of oocyte epigenetics during oogenesis is potentially exposed to interfering factors, such as assisted reproduction technologies (ARTs) or environmental changes, whose impact may be enhanced by reproductive aging. As the effects of maternal aging on molecular mechanisms governing the function of the human oocyte remain poorly understood, studies in animal models are essential to deepen current understanding, with translational implications for human ARTs. The present mini review aims at offering an updated and consistent view of cytoplasmic alterations occurring in oocytes during aging, focusing particularly on gene and epigenetic regulation. Appreciation of these mechanisms could inspire solutions to mitigate/control the phenomenon, and thus benefit modern ARTs.

Anthropogenic Drivers Leading to Population Decline and Genetic Preservation of the Eurasian Griffon Vulture (Gyps fulvus)

Human activities are having increasingly devastating effects on the health of marine and terrestrial ecosystems. Studying the adaptive responses of animal species to changes in their habitat can be useful in mitigating this impact. Vultures represent one of the most virtuous examples of adaptation to human-induced environmental changes. Once dependent on wild ungulate populations, these birds have adapted to the epochal change resulting from the birth of agriculture and livestock domestication, maintaining their essential role as ecological scavengers. In this review, we retrace the main splitting events characterising the vultures’ evolution, with particular emphasis on the Eurasian griffon Gyps fulvus. We summarise the main ecological and behavioural traits of this species, highlighting its vulnerability to elements introduced into the habitat by humans. We collected the genetic information available to date, underlining their importance for improving the management of this species, as an essential tool to support restocking practices and to protect the genetic integrity of G. fulvus. Finally, we examine the difficulties in implementing a coordination system that allows genetic information to be effectively transferred into management programs. Until a linking network is established between scientific research and management practices, the risk of losing important wildlife resources remains high.

The subcortical maternal complex: emerging roles and novel perspectives

Since its recent discovery, the subcortical maternal complex (SCMC) is emerging as a maternally inherited and crucial biological structure for the initial stages of embryogenesis in mammals. Uniquely expressed in oocytes and preimplantation embryos, where it localizes to the cell subcortex, this multiprotein complex is essential for early embryo development in the mouse and is functionally conserved across mammalian species, including humans. The complex has been linked to key processes leading the transition from oocyte to embryo, including meiotic spindle formation and positioning, regulation of translation, organelle redistribution, and epigenetic reprogramming. Yet, the underlying molecular mechanisms for these diverse functions are just beginning to be understood, hindered by unresolved interplay of SCMC components and variations in early lethal phenotypes. Here we review recent advances confirming involvement of the SCMC in human infertility, revealing an unexpected relationship with offspring health. Moreover, SCMC organization is being further revealed in terms of novel components and interactions with additional cell constituents. Collectively, this evidence prompts new avenues of investigation into possible roles during the process of oogenesis and the regulation of maternal transcript turnover during the oocyte to embryo transition.

Mitochondrial DNA Depletion in Granulosa Cell Derived Nuclear Transfer Tissues

Somatic cell nuclear transfer (SCNT) is a key technology with broad applications that range from production of cloned farm animals to derivation of patient-matched stem cells or production of humanized animal organs for xenotransplantation. However, effects of aberrant epigenetic reprogramming on gene expression compromise cell and organ phenotype, resulting in low success rate of SCNT. Standard SCNT procedures include enucleation of recipient oocytes before the nuclear donor cell is introduced. Enucleation removes not only the spindle apparatus and chromosomes of the oocyte but also the perinuclear, mitochondria rich, ooplasm. Here, we use a Bos taurus SCNT model with in vitro fertilized (IVF) and in vivo conceived controls to demonstrate a ∼50% reduction in mitochondrial DNA (mtDNA) in the liver and skeletal muscle, but not the brain, of SCNT fetuses at day 80 of gestation. In the muscle, we also observed significantly reduced transcript abundances of mtDNA-encoded subunits of the respiratory chain. Importantly, mtDNA content and mtDNA transcript abundances correlate with hepatomegaly and muscle hypertrophy of SCNT fetuses. Expression of selected nuclear-encoded genes pivotal for mtDNA replication was similar to controls, arguing against an indirect epigenetic nuclear reprogramming effect on mtDNA amount. We conclude that mtDNA depletion is a major signature of perturbations after SCNT. We further propose that mitochondrial perturbation in interaction with incomplete nuclear reprogramming drives abnormal epigenetic features and correlated phenotypes, a concept supported by previously reported effects of mtDNA depletion on the epigenome and the pleiotropic phenotypic effects of mtDNA depletion in humans. This provides a novel perspective on the reprogramming process and opens new avenues to improve SCNT protocols for healthy embryo and tissue development.

91 Effect of heat stress during mice germ-cell DNA methylation programming on oocyte developmental competence: A preliminary study

Heat stress (HS) is characterised by an elevation in body temperature that ultimately undermines organism physiology. Most livestock production occurs in tropical regions under potential HS conditions that diminish productive and reproductive potential. Despite extensive evidence of HS-mediated effects in cell function, stage-specific detrimental effects of HS during oogenesis remain elusive. Mouse models represent an attractive alternative for faster interrogation of stage-specific phenomena during oogenesis. Therefore, the aim of the study was to determine the effects of HS exposure during the major window of female mice germ-cell DNA methylation programming. CD1/Swiss female mice with litters (F0 progeny) at postnatal Day 10 (P10) were randomly allocated to HS (35°C/12-h light; 21°C/12-h dark) or control (CTL: 21°C/24h) for 11 days. The F0 progeny were weaned at P21 and superovulated after reaching puberty at P35. F0 females were superovulated by intraperitoneal injections with 5.0IU of equine chorionic gonadotrophin (PMSG) followed by 5.0IU of human chorionic gonadotrophin (hCG) within a 48-h interval. Pre-implantation embryos were harvested at Day E3.5 in M2 medium under a stereomicroscope. One F0 female per litter was randomly mated to control mice when it reached 6 weeks of age. Data were subjected to least-squares analysis of variance using the General Linear Models procedure of SAS (SAS Institute Inc.). The experiment was replicated twice (CTL: n=4 F0 females and HS: n=4 F0 females). Preliminary results are given as LSM±s.e.m. There was no effect of heat stress on the number of embryos collected per female (CTL: 9.75±4.87 vs. HS: 11.25±4.81) or the percentage of non-viable embryos (CTL: 25.0±0.23% vs. HS: 42.5±0.25%). However, heat stress tended (P=0.07) to reduce the percentage of embryos that reached the morula stage from 63.5±0.08% for CTL to 35.1±0.09% for HS. The percentage of blastocysts collected (CTL: 11.45±0.18% vs. HS: 22.32±0.19%) and litter size of F0 females (CTL: 7.47±1.76 vs. HS: 7.66±1.47) was not affected by treatment. In conclusion, exposure of female mice to 11-day HS during the major wave of de novo DNA methylation during oocyte growth tended to reduce subsequent pre-implantation embryonic development, although it did not affect full-term development after natural mating.

126 Subcortical maternal complex (SCMC) expression during folliculogenesis is affected by oocyte donor age in sheep

Age-associated decline in female fertility is largely attributable to decrease in oocyte quality. However, the molecular mechanisms that shape oocyte developmental competence, and that may be involved in reproductive aging, are yet to be elucidated. The subcortical maternal complex (SCMC) is a multiprotein complex located in the subcortex of oocytes that is essential for early embryogenesis and female fertility. It appears to be functionally conserved across mammals; aberrant expression of its members was observed in several animal models of differential competence, and mutations in human SCMC genes were associated with certain human reproductive disorders. At least seven proteins contribute to the complex: KH domain-containing 3 like (KHDC3/FILIA), NLR family pyrin domain-containing 2 (NLRP2), NLRP5 (MATER), oocyte expressed protein (OOEP), peptidyl arginine deiminase 6 (PADI6), transducin-like enhancer of split 6 (TLE6), and zinc finger BED-type-containing 3 (ZBED3), all encoded by maternal effect genes (MEGs). The aim of the present work was to evaluate expression dynamics of the SCMC components during folliculogenesis in relation to maternal age in sheep. Total RNA was isolated and reverse-transcribed from pools of denuded growing oocytes (GO) of different diameters (70-90μm (small, S), 90-110μm (medium, M), or 110-130μm (large, L)) derived from nonhormonally treated prepubertal (Pr, age 40 days), adult (Ad, age &lt;4 years), or aged (Aged, age &gt;6 years) animals (5 pools of 30 oocytes per experimental group). The SCMC expression was assessed by real-time PCR (PCR efficiency of 90-110% and correlation coefficient r2&gt;0.99). Data were normalized against oocyte number and an exogenous spike-in mRNA, Luciferase, as reference gene. Expression dynamics were analyzed within each age group (general linear model ANOVA). Strikingly, patterns specifically associated with donor age were observed during folliculogenesis for six of the seven SCMC components. The Pr group showed active transcription of all mRNA, except ZBED3, during the entire window of oocyte growth (P&lt;0.05). On the contrary, the similar abundance of NLRP2, NLRP5, PADI6, and ZBED3 in Ad S, M, and L GO suggests earlier storage during folliculogenesis; FILIA, OOEP, and TLE6 showed an increase between Ad S and M GO (P&lt;0.05), indicating that the synthesis of these transcripts is complete at this stage (M GOs). Notably, oocytes derived from Aged donors showed a completely inverse expression pattern, with a decrease in abundance of NLRP2, TLE6, FILIA, and PADI6 mRNAs during the last stage of oocyte growth (L GO; P&lt;0.05). Interestingly, MATER showed very high variability in expression (standard error (SE) ranging from 0.79 to 1.13 quantitation cycles (Cq)) in Aged GO, compared to Ad GO (SE 0.16-0.24 Cq) or Pr GO (SE 0.16-0.26 Cq), suggesting large inter-oocyte differences. In conclusion, age affects the storage of the MEGs encoding the SCMC during folliculogenesis. The observed depletion in SCMC transcripts in GO of aged donors is likely to be involved in the age-related decline in oocyte quality.

38 Vitrification of prepubertal lamb spermatogonia using a novel vitrification system

Vitrification is a method extensively used for preserving oocytes and embryos and is also gaining acceptance for preserving gonadal tissue. Cryopreservation of spermatogonial stem cells is an applicable method for young males seeking fertility preservation before starting a treatment or can be a tool for genetic preservation of rare or high-value animals. The aim of this work was to evaluate the cryopreservation of testicular tissue from young lambs by vitrification using a new device named E.Vit (FertileSafe, Ness Ziona, Israel) that permits all cryopreservation procedures to be performed in straw. The new device consists of a 0.3-mL straw (Cryo Bio System, IMV, L’Aigle, France) with a capsule containing 50-µm pores inserted at one end. Testicular tissue extracts were prepared from testes of slaughtered lambs (n=10, 40 days old), opened by sagittal sectioning with a microblade and collecting small pieces of testicular tissue (1mm3) from the middle part of the rete testis. Three pieces of gonadal tissue were inserted into each E.Vit device. Each straw was sequentially loaded vertically in two 1.5-mL microtubes, which contained the following solutions: first, the equilibrating solution (7.5% dimethyl sulfoxide+7.5% ethylene glycol+20% FCS in TCM-199) for 6min, followed by 90min in the vitrification solution (18% dimethyl sulfoxide+18% ethylene glycol+0.5M Trehalose+BSA in TCM-199). After exposure to the equilibrating solution and vitrification solution, the solutions were removed and the straws were directly loaded into LN2. The warming procedure consisted of placing the straws directly into 5-mL tubes containing 100, 50, and 25% warming solution (1M sucrose in TCM-199+20% FCS) at 38.6°C for 5min each before arrival into the holding medium. Samples were recovered from the straws incubated at 38.6°C in 5% CO2 in air in TCM 199+5% FCS and evaluated at 0 and 2h post-warming for viability using trypan blue staining. Expression of a panel of specific genes (SOD2, HSP90b, BAX, POUF5/OCT4, TERT, CIRBP, KIF11, AR, FSHR) was analysed by real-time PCR in cryopreserved tissue in vitro cultured for 2h post-warming (2hV), in fresh controls immediately after tissue dissection (0hF), and after 2h of in vitro culture (2hF). The majority of cells survived after vitrification, although viability immediately after warming (0hV: 56%±1.45) or after 2h of in vitro culture (IVC) (2hV: 54±7%) was significantly lower compared with non-cryopreserved fresh controls (0hF: 89%±1.45; ANOVA P&lt;0.05). Expression analysis showed specific patterns for the different genes. Notably, BAX transcript abundance was not affected by vitrification or IVC, indicating an acceptable level of stress for the cells. The genes HSP90b and CIRBP were down-regulated in 2hF but increased in 2hV, as expected. Expression of SOD1 and OCT4 was altered by vitrification but not by IVC. Conversely, expression of TERT, KIF11, and AR was affected by both IVC and cryopreservation (ANOVA P&lt;0.05). This novel protocol for testicular tissue cryopreservation of prepubertal animals may be a promising strategy for fertility preservation and can contribute as a new approach in the development of large-scale biodiversity programs.

Structure of preantral follicles, oxidative status and developmental competence of in vitro matured oocytes after ovary storage at 4 °C in the domestic cat model

BACKGROUND

Storage conditions during transportation of explanted ovaries are a critical step in setting up fertility preservation protocols in both animal and human fields. Here, we evaluated the effects of ovary storage at 4 °C on the preservation of preantral follicles and oocytes retrieved from antral follicles using the domestic cat as model.

METHODS

Ovaries were harvested from fifty-five healthy domestic queens during ovariectomy and stored at 4 °C for 0 (control), 24, 48, 72 and 96 h. In Experiment 1, the effects of the storage period at 4 °C on the morphology, cytoskeleton (α/β tubulin) and DNA integrity (phosphorylation of histone H2AX) of preantral follicles were investigated. In Experiment 2, oocytes recovered from antral follicles were matured and fertilized in vitro to evaluate their meiotic and developmental competence. Reactive oxygen species (ROS), glutathione (GSH) and lipid peroxidation were measured in matured oocytes.

RESULTS

The results showed that: a) storage up to 24 h did not affect the morphology and the DNA integrity of preantral follicles; b) extended storage times caused progressive morphological abnormalities, disassembling of microtubules and DNA damage; c) storage up to 48 h did not influence in vitro meiotic maturation of oocytes nor cleavage after in vitro fertilization. However, only oocytes stored within the ovary for 24 h produced blastocysts in a percentage similar to control oocytes; d) GSH levels of in vitro matured oocytes did not change at any time during ovary storage; a progressive increase in ROS levels was detected from 48 h associated with elevated lipid peroxidation at 72 and 96 h of storage.

CONCLUSIONS

Storage of cat ovaries for up to 24 h caused minimal alteration of preantral follicles and oocytes. The extension of the storage period beyond 24 h progressively impaired the structure of follicles, and modified the oxidative status of in vitro matured oocytes and their developmental competence after in vitro fertilization. This information may help when setting up programs for fertility conservation, especially for wild feline species which die in geographic areas located far away from ARTs centers.

Delay in maternal transcript degradation in ovine embryos derived from low competence oocytes

Oocytes from prepubertal animals have a reduced ability to undergo embryo development and produce viable offspring. The present work used an ovine model consisting of oocytes derived from adult and prepubertal donors to assess the molecular status of oocytes and preimplantation embryos with different developmental competence. The lower potential of oocytes of young donors was confirmed in terms of in vitro developmental capabilities and kinetics. A panel of genes including maternal effect (DPPA3, GDF9, NMP2, ZAR1) and housekeeping genes (ACTB, RPL19, SDHA, YWHAZ, ATP1A1), genes involved in DNA methylation (DNMT1, DNMT3A, DNMT3B), genomic imprinting (IGF2R), pluripotency (NANOG, POU5F1) and cell cycle regulation (CCNB1, CDK1, MELK) was relatively quantified. Temporal analysis during oocyte maturation and preimplantation embryo development evidenced patterns associated with donor age. With a few gene-specific exceptions, the differential model showed a reduced transcript abundance in immature prepubertal oocytes that completely reversed trend after fertilization, when higher mRNA levels were consistently observed in early embryos, indicating a delay in maternal transcript degradation. We propose that the molecular shortage in the prepubertal oocyte may affect its developmental potential and impair the early pathways of maternal mRNA clearance in the embryo. While confirming the different potential of oocytes derived from adult and prepubertal donors, our work showed for the first time a consistent delay in maternal transcript degradation in embryos derived from low competence oocytes that interestingly recalls the delayed developmental kinetics. Such abnormal transcript persistence may hinder further development and represents a novel perspective on the complexity of developmental competence.

Insights on Cryopreserved Sheep Fibroblasts by Cryomicroscopy and Gene Expression Analysis

Cryopreservation includes a set of techniques aimed at storing biological samples and preserving their biochemical and functional features without any significant alterations. This study set out to investigate the effects induced by cryopreservation on cultured sheepskin fibroblasts (CSSF) through cryomicroscopy and gene expression analysis after subsequent in vitro culture. CSSF cells were cryopreserved in a cryomicroscope (CM) or in a straw programmable freezer (SPF) using a similar thermal profile (cooling rate -5°C/min to -120°C, then -150°C/min to -196°C). CSSF volume and intracellular ice formation (IIF) were monitored by a CM, while gene expression levels were investigated by real-time polymerase chain reaction in SPF-cryopreserved cells immediately after thawing (T0) and after 24 or 48 hours (T24, T48) of post-thaw in vitro culture. No significant difference in cell viability was observed at T0 between CM and SPF samples, while both CM and SPF groups showed lower viability (p < 0.05) compared to the untreated control group. Gene expression analysis of cryopreserved CSSF 24 and 48 hours post-thawing showed a significant upregulation of the genes involved in protein folding and antioxidant mechanisms (HPS90b and SOD1), while a transient increase (p < 0.05) in the expression levels of OCT4, BCL2, and GAPDH was detected 24 hours post-thawing. Overall, our data suggest that cryostored CSSF need at least 24 hours to activate specific networks to promote cell readaptation.

Methylation dynamics during folliculogenesis and early embryo development in sheep

Genome-wide DNA methylation reprogramming occurs during mammalian gametogenesis and early embryogenesis. Post-fertilization demethylation of paternal and maternal genomes is considered to occur by an active and passive mechanism respectively, in most mammals but sheep; in this species no loss of methylation was observed in either pronucleus. Post-fertilization reprogramming relies on methylating and demethylating enzymes and co-factors that are stored during oocyte growth, concurrently with the re-methylation of the oocyte itself. The crucial remodelling of the oocyte epigenetic baggage often overlaps with potential interfering events such as exposure to assisted reproduction technologies or environmental changes. Here, we report a temporal analysis of methylation dynamics during folliculogenesis and early embryo development in sheep. We characterized global DNA methylation and hydroxymethylation by immunofluorescence and relatively quantified the expression of the enzymes and co-factors mainly responsible for their remodelling (DNA methyltransferases (DNMTs), ten-eleven translocation (TET) proteins and methyl-CpG-binding domain (MBD) proteins). Our results illustrate for the first time the patterns of hydroxymethylation during oocyte growth. We observed different patterns of methylation and hydroxymethylation between the two parental pronuclei, suggesting that male pronucleus undergoes active demethylation also in sheep. Finally, we describe gene-specific accumulation dynamics for methylating and demethylating enzymes during oocyte growth and observe patterns of expression associated with developmental competence in a differential model of oocyte potential. Our work contributes to the understanding of the methylation dynamics during folliculogenesis and early embryo development and improves the overall picture of early rearrangements that will originate the embryo epigenome.

Cerium oxide nanoparticles (CeO2 NPs) improve the developmental competence of in vitro-matured prepubertal ovine oocytes

The present study investigated whether supplementation with different doses of cerium dioxide nanoparticles (CeO2 NPs) during in vitro maturation (IVM) of prepubertal ovine oocytes influenced their embryonic development in vitro. Cumulus–oocyte complexes derived from the ovaries of slaughtered prepubertal sheep underwent IVM with CeO2NPs (0, 44, 88 or 220 µg mL–1). Matured oocytes were fertilised in vitro and zygotes were cultured for 7 days. The results demonstrated that CeO2NPs were internalised in the cumulus cells and not in the oocyte. The treatment with CeO2NPs did not affect nuclear maturation or intracellular levels of reactive oxygen species of the oocytes. The percentage of oocytes with regular chromatin configuration and cytoskeleton structures when treated with 44 µg mL–1 CeO2NPs was similar to oocytes matured in the absence of CeO2NPs and significantly higher than those treated with 88 or 220 µg mL–1 CeO2NPs. The relative quantification of transcripts in the cumulus cells of oocytes matured with 44 µg mL–1 CeO2NPs showed a statistically lower mRNA abundance of BCL2-associated X protein (BAX), B-cell CLL/lymphoma 2 (BCL2) and superoxide dismutase 1 (SOD1) compared with the 0 µg mL–1 CeO2 NPs group. A concentration of 44 µg mL–1 CeO2NPs significantly increased the blastocyst yield and their total, inner cell mass and trophectoderm cell numbers, compared with the 0 and 220 µg mL–1 groups. A low concentration of CeO2NPs in the maturation medium enhanced in vitro embryo production of prepubertal ovine oocytes.

The subcortical maternal complex: multiple functions for one biological structure?

The subcortical maternal complex (SCMC) is a multiprotein complex uniquely expressed in mammalian oocytes and early embryos, essential for zygote progression beyond the first embryonic cell divisions. Similiar to other factors encoded by maternal effect genes, the physiological role of SCMC remains unclear, although recent evidence has provided important molecular insights into different possible functions. Its potential involvement in human fertility is attracting increasing attention; however, the complete story is far from being told. The present mini review provides an overview of recent findings related to the SCMC and discusses its potential physiological role/s with the aim of inspiring new directions for future research.

In vitro Developmental Competence of Adult Sheep Oocytes Treated with Roscovitine

The efficiency of in vitro sheep embryo production is still low compared to that observed in vivo and in other species. In this context, meiotic inhibition strategies emerged as a promising alternative to improve this biotechnology. So, this study aimed to evaluate, for the first time, the effects of roscovitine on in vitro maturation of sheep oocytes and their subsequent embryo development. For this, cumulus-oocyte complexes (COCs) were cultured for 6 h in the presence (Rosco) or absence (Control) of 75 μm roscovitine and, subsequently, in vitro matured (IVM) for 18 h with gonadotropins. At 0 (Immature), 6 and 24 h of culture, the nuclear status of oocytes was evaluated by Hoechst staining. Embryo cleavage and blastocyst formation were recorded 30 h after in vitro fertilization and on day 7 of culture, respectively. Blastocyst quality was evaluated by differential staining. At 6 h, the GV rate in the Rosco treatment (93.8%) was similar to that observed in the Immature oocytes (94.9%) and significantly higher compared to Control (41.3%). After IVM for 18 h, a high and similar proportion of oocytes from Rosco (93.6%) and Control (88.4%) reached the MII stage. In both treatments, approximately 70% of oocytes cleaved and 50% of them developed up to blastocyst. The mean percentage of blastocyst cells, embryoblast, trophoblast and pyknosis did also not differ between Control and Rosco. In conclusion, roscovitine, at the studied experimental conditions, was efficient to reversibly inhibit the meiosis of adult sheep oocytes without detrimental effect on development and quality of the in vitro produced embryos.

A novel technique for in vitro maturation of sheep oocytes in a liquid marble microbioreactor

PURPOSE

The aim of this work was to develop a microbioreactor using liquid marble (LM) as a novel system for oocyte in vitro maturation (IVM) in small volumes.

METHODS

Cumulus-oocyte complexes (COCs) obtained from slaughterhouse sheep ovaries were in vitro matured in a LM system prepared by placing a drop (30 μl containing 10 COCs) suspended in TCM 199 supplemented with 10 % (v/v) oestrus sheep serum (OSS) and 0.1 IU FSH and LH onto a polytetrafluoroethylene (PTFE) particle bed (LM group). As a control group (CTRL group), COCs were in vitro matured in standard volume and conditions (600 μl of IVM medium in a four-well dish). After 24-h culture at 38.5 °C in 5 % CO2 in air, COCs were released from LM and the following parameters were evaluated: (a) percentage of MII oocytes, (b) oocyte developmental competence following in vitro fertilization (IVF) or parthenogenetic activation (PA) and embryo culture for 8 days in synthetic oviductal fluid (SOF) medium at 38.5 °C in 5 % O2, 5 % CO2, and 90 % N2.

RESULTS

The results indicated similar percentage of MII oocytes in LM and CTRL groups (88.0 vs. 92.0 %). No differences were observed in blastocyst rate after IVF (LM 47.5 % vs. CTRL 50.2 %, P=0.637) or PA (LM 44.4 % vs. CTRL 48.3 %, P=0.426).

CONCLUSIONS

The results indicate that LM microbioreactor is a viable technique that provides a suitable microenvironment to induce oocyte in vitro maturation.

Lipid droplet distribution of immature canine oocytes in relation to their size and the reproductive stage

This study investigated the distribution of lipid droplets (LD) in immature canine oocytes in relation to their size and the reproductive stage. Oocytes were collected from the ovaries of bitches at different estrous stages, divided according to their size (110-120 µm; >120 µm), and stained with Nile Red to detect lipid droplet distribution. At the follicular phase most of the oocytes displayed a diffuse pattern of LD distribution, whereas at anestrus and luteal phase oocytes showed LD mainly in a peripheral/ perinuclear LD distribution. A significantly higher intensity of LD has been recorded in the oocytes > 120 µm compared to those of smaller size (110 - 120 µm) at all stages of the estrous cycle. At follicular phase, oocytes > 120 µm displayed LD intensity similar to that of oocytes > 120 µm at luteal phase and higher compared to the oocytes of the other groups.

210 DNA METHYLATION AND HYDROXYMETHYLATION ANALYSIS IN A MODEL OF OOCYTE DIFFERENTIAL DEVELOPMENTAL COMPETENCE IN SHEEP

DNA methylation is an important epigenetic mark that plays a role in gene regulation by the addition of a methyl group to CpG islands in the DNA. Despite being relatively stable in somatic cells, DNA methylation is subject to reprogramming during embryo development and gametogenesis. The aim of this work was to evaluate different aspects of DNA methylation in relation to oocyte quality in the ovine species. A model of differential developmental competence consisting in ovine oocytes and in vitro produced (IVP) blastocysts derived from adult (AD) and prepubertal (PR) donors, was used. The methylation was analysed in terms of: expression of a panel of genes involved in DNA methylation [DNA methyltransferases (DNMTs)] and demethylation [ten-eleven translocation dioxygenases (TET)] in oocytes and blastocysts; global methylation and hydroxymethylation by direct immunofluorescence; locus-specific methylation of 2 imprinted genes by pyrosequencing. Gene relative quantification was performed by RNA reverse transcription followed by real-time PCR. Pools of 10 immature (GV) and in vitro-matured (MII) oocytes and (IVP) blastocysts derived from AD and PR donors (4 replicates per class) were analysed. Lower expression of TET1, TET2, and TET3 was observed in PR GV oocytes (ANOVA; P < 0.05), while no significant differences were found for the enzymes involved in methylation (DNMT1, DNMT3A, DNMT3B; ANOVA; P > 0.05). The levels of all the genes studied showed no significant differences in embryos at blastocyst stage (ANOVA; P > 0.05). Methylation and hydroxymethylation immunostaining were performed in GV and MII oocytes using anti-5-methylcytosine mouse mAb and 5-hydroxymethylcytosine rabbit pAB. High levels of DNA methylation were observed in both AD and PR GV and MII oocytes, while hydroxymethylation immunopositivity was scattered evident throughout the gamete chromatin. Pyrosequencing of bisulfite converted DNA was used to determine the methylation status within differentially methylated regions (DMR) of maternally imprinted H19 (CTCF binding site IV; 11 CpG sites) and paternally imprinted IGF2R (17CpG sites within intron 2). No differences were observed between classes of oocytes for each gene (pools of 40 oocytes per replicate, 3 replicates per class; ANOVA; P > 0.05). Our work shows no differences in the expression of the enzymes involved in methylation, in accordance with the results of global and locus specific methylation analysis. Conversely, we observed lower expression of the TET genes in PR GV oocytes (ANOVA; P > 0.05). TET1, TET2, and TET3, whose expression has never been studied in ovine, generate 5-hydroxymethlcytosine (5hmC) by oxidation of 5-methylcytosine (5mC), and are involved in active DNA demethylation during early embryo development. Our observation of lower expression of the TET genes in lower competence PR GV oocytes suggests that epigenetic mechanisms may affect oocyte quality and paves the way to better understand methylation dynamics during sheep pre-implantation development.

Expression of maternally derived KHDC3, NLRP5, OOEP and TLE6 is associated with oocyte developmental competence in the ovine species

BACKGROUND

The sub-cortical maternal complex (SCMC), located in the subcortex of mouse oocytes and preimplantation embryos, is composed of at least four proteins encoded by maternal effect genes: OOEP, NLRP5/MATER, TLE6 and KHDC3/FILIA. The SCMC assembles during oocyte growth and was seen to be essential for murine zygote progression beyond the first embryonic cell divisions; although roles in chromatin reprogramming and embryonic genome activation were hypothesized, the full range of functions of the complex in preimplantation development remains largely unknown.

RESULTS

Here we report the expression of the SCMC genes in ovine oocytes and pre-implantation embryos, describing for the first time its expression in a large mammalian species. We report sheep-specific patterns of expression and a relationship with the oocyte developmental potential in terms of delayed degradation of maternal SCMC transcripts in pre-implantation embryos derived from developmentally incompetent oocytes. In addition, by determining OOEP full length cDNA by Rapid Amplification of cDNA Ends (RACE) we identified two different transcript variants (OOEP1 and OOEP2), both expressed in oocytes and early embryos, but with different somatic tissue distributions. In silico translation showed that 140 aminoacid peptide OOEP1 shares an identity with orthologous proteins ranging from 95% with the bovine to 45% with mouse. Conversely, OOEP2 contains a premature termination codon, thus representing an alternative noncoding transcript and supporting the existence of aberrant splicing during ovine oogenesis.

CONCLUSIONS

These findings confirm the existence of the SCMC in sheep and its key role for the oocyte developmental potential, deepening our understanding on the molecular differences underlying cytoplasmic vs nuclear maturation of the oocytes. Describing differences and overlaps in transcriptome composition between model organisms advance our comprehension of the diversity/uniformity between mammalian species during early embryonic development and provide information on genes that play important regulatory roles in fertility in nonmurine models, including the human.

Effect of caffeine treatment before vitrification on MPF and MAPK activity and spontaneous parthenogenetic activation of in vitro matured ovine oocytes

BACKGROUND

Molecules that stabilize protein kinases may be useful in overcoming the deleterious effects of cryopreservation.

OBJECTIVE

To evaluate the effect of caffeine treatment before vitrification of in vitro matured ovine oocytes on the activity of MPF and MAPK as well as the spontaneous parthenogenetic activation after 24 h culture.

MATERIALS AND METHODS

Oocytes obtained from slaughterhouse sheep ovaries were in vitro matured for 21 h, incubated for 3 h with or without caffeine and then vitrified. After warming, oocytes were processed for the analysis of chromatin configuration and the evaluation of spontaneous parthenogenetic activation (24 h in vitro culture). Fresh in vitro matured oocytes were used as control.

RESULTS

Caffeine treatment before vitrification maintained the MPF activity at a level similar to that of fresh oocytes, and reduced the spontaneous parthenogenetic activation in comparison with oocytes that were not-treated with caffeine.

CONCLUSION

Caffeine treatment prolongs the meiotic arrest of vitrified MII oocytes, likely via its action of stabilizing the MPF level.

Tissue-specific and minor inter-individual variation in imprinting of IGF2R is a common feature of Bos taurus Concepti and not correlated with fetal weight

The insulin-like growth factor 2 receptor (IGF2R) is essential for prenatal growth regulation and shows gene dosage effects on fetal weight that can be affected by in-vitro embryo culture. Imprinted maternal expression of murine Igf2r is well documented for all fetal tissues excluding brain, but polymorphic imprinting and biallelic expression were reported for IGF2R in human. These differences have been attributed to evolutionary changes correlated with specific reproductive strategies. However, data from species suitable for testing this hypothesis are lacking. The domestic cow (Bos taurus) carries a single conceptus with a similar gestation length as human. We identified 12 heterozygous concepti informative for imprinting studies among 68 Bos taurus fetuses at Day 80 of gestation (28% term) and found predominantly maternal IGF2R expression in all fetal tissues but brain, which escapes imprinting. Inter-individual variation in allelic expression bias, i.e. expression of the repressed paternal allele relative to the maternal allele, ranged from 4.6−8.9% in heart, 4.3−10.2% in kidney, 6.1−11.2% in liver, 4.6−15.8% in lung and 3.2−12.2% in skeletal muscle. Allelic bias for mesodermal tissues (heart, skeletal muscle) differed significantly (P<0.05) from endodermal tissues (liver, lung). The placenta showed partial imprinting with allelic bias of 22.9−34.7% and differed significantly (P<0.001) from all other tissues. Four informative fetuses were generated by in-vitro fertilization (IVF) with embryo culture and two individuals displayed fetal overgrowth. However, there was no evidence for changes in imprinting or DNA methylation after IVF, or correlations between allelic bias and fetal weight. In conclusion, imprinting of Bos taurus IGF2R is similar to mouse except in placenta, which could indicate an effect of reproductive strategy. Common minor inter-individual variation in allelic bias and absence of imprinting abnormalities in IVF fetuses suggest changes in IGF2R expression in overgrown fetuses could be modulated through other mechanisms than changes in imprinting.

219 EXPRESSION PATTERN OF THE SUB-CORTICAL MATERNAL COMPLEX IN OVINE OOCYTES AND PRE-IMPLANTATION EMBRYOS

The sub-cortical maternal complex (SCMC) is a multi-protein complex located in the sub-cortex of the oocyte. In mouse, it assembles during oocyte growth and is essential for zygotes to progress beyond the first embryonic cell divisions (Li et al., 2008). At least 4 proteins contribute to the complex: oocyte expressed protein (OOEP), maternal antigen that embryo requires (MATER), transducin-like enhancer of split 6 (TLE6), and ES cell associated transcript 1 (ECAT1), all encoded by maternal effect genes. In mouse, the relative transcripts are degraded during meiotic maturation and ovulation, whereas the SCMC proteins persist in the early embryo. Whereas MATER expression has been studied in several species, the existence of the genes encoding the other components has been assessed in few mammalian species and their pattern of expression during pre-implantation development has been analysed only in mouse (Li et al. 2008 Dev. Cell 15, 416–425). In a previous work (Bebbere et al. 2008 Reprod. Fertil. Dev. 20, 908–915), we assessed MATER existence and pattern of expression in the ovine species. The aim of the present work was to assess the existence of OOEP, TLE6, and FILIA in the ovine species and to analyse the expression pattern of the 4 genes in the oocytes and during pre-implantation embryo development. Total RNA was isolated and reverse transcribed from pools of immature (GV) and in vitro matured (IVM) metaphase II (MII) oocytes, from in vitro fertilized and cultured (IVFC) embryos at the 2-, 4-, 8-, and 16-cell stage and from blastocysts. Three pools of 10 oocyte/embryos were analysed for each class. Primers were designed on the basis of the sequences conserved among orthologs and amplify intron-spanning regions. The PCR products were sequenced, and the alignment, performed with BLASTn, confirmed the homology with the orthologous genes present in public databases. Real-time PCR analysis revealed that all 4 transcripts are present at its highest level in the GV oocyte but decrease during embryo pre-implantation development with a gene-specific pattern. Conversely to the pattern of expression observed in mouse, all 4 transcripts persisted until the 8-cell stage embryo, disappearing only at the 16-cell stage. No transcripts were detected at the blastocyst stage. This study confirms the existence of transcripts related to SCMC also in the ovine species, but highlights species-specific patterns of expression in the 2 species, possibly related to the different time of activation of the embryo genome in mouse and in sheep. The observed expression patterns suggest an involvement of the protein complex in oocyte maturation and in the very first phases of life, possibly in the transition from the maternal to embryonic program of development.

Unveiling mRNA changes during meiotic progression and pre-implantation development: help from large animal models

Assisted reproductive technologies (ART) are successfully applied in several mammals, including humans, thanks to the ability of oocytes and embryos to face maturation, fertilization and first development in vitro. However, efficiency and safety of ART represent main issues. Mammalian oocytes and early embryos are transcriptionally inactive, and rely exclusively on maternal RNAs and proteins, deposited during oocyte growth, until embryonic genome activation (EGA). Such transcriptional quiescence needs complex post-transcriptional and post-translational mechanisms to coordinate meiotic maturation, fertilization, and reprogramming of the nascent genome. These events are the final outcome of complex, hormonally regulated biological processes that translate into specific molecular mechanisms, which are still far from being fully understood. A deep knowledge of these early phases of development is crucial to understand the core mechanisms of life onset, and to optimize the safety and efficiency of in vitro reproductive technologies. This work focuses on meiotic progression and pre-implantation development in mammals, underlining the importance of fundamental molecules stored during oocyte growth and selectively used during early embryogenic stages. Taking into account the species-specific behaviour of these pivotal molecules, this review describes the advantages of using large domestic animals for research in the reproductive field and proposes large domestic animals as models to improve human ART.

High hydrostatic pressure treatment improves the quality of in vitro-produced ovine blastocysts

Exposure to sub-lethal hydrostatic pressure (HP) treatment is emerging as an approach to improve the general resistance of gametes and embryos to in vitro conditions. The present study was aimed to evaluate the effect of HP treatment on in vitro-produced ovine blastocysts. Experiment 1 was aimed to define optimal treatment parameters: two different HP treatments were applied to blastocysts and embryo survival was evaluated. In Experiment 2, HP parameters (40 MPa, 70 min, 38 °C) selected in Experiment 1 were used to treat blastocysts. Embryo quality was assessed and compared with untreated controls by counting total cell number, the inner cell mass (ICM) and trophectoderm (TE) cells and by evaluating nuclear picnosis. HP-treated blastocysts were processed for gene expression analysis (AQP3, ATP1A1, BAX, CDH1, HSP90β, NANOG, OCT4 and TP53) 1, 5h after the end of HP exposure. Results showed that the hatching rate of embryos treated at 40 MPa was significantly higher than that of the 60 MPa-treated group (P<0.01) and similar to untreated embryos. Blastocysts exposed at 40 MPa showed higher ICM (P<0.05) and TE (P<0.01) cell number and a lower percentage of picnotic nuclei (P<0.05) compared with the control group. Significantly lower abundance for BAX (P<0.01) and OCT4 (P<0.05) transcripts were observed in HP embryos than in the control group. In conclusion, treatment with HP improved the quality of in vitro-produced ovine blastocysts by increasing their cell number and reducing the proportion of nuclear picnosis.

124 EXPRESSION OF PLURIPOTENCY MARKERS IN GENITAL RIDGES OF OVINE FOETUSES

Fundamental problems of primordial germ cell (PGC) allocation, characterization, lineage restriction, and differentiation have been extensively studied in the mouse. Historically, these cells can be identified using criteria as alkaline phosphatase, but also by the expression of other pluripotency markers suchas OCT4, Nanog, cKIT, SSEA1, SSEA4. Much less is known about PGC inother mammals. The objective ofthis study wasto describe, for the first time, the expression of multiple pluripotency markers in the genital ridges of ovine fetuses evaluating the binding of antibodies for stem cell surface markers (SSEA-1 and EMA-1) and the expression of Oct4, Nanog, and Sox2 genes. Ovine fetuses (24 and 27 days) were collected from slaughtered ewes and transported in a PBS solution at 4°C, to be processed as follows: Immunohistochemistry: 4 foetuses for each age were frozen in OCT TissueTek freezing compound and stored at -80°C. Tissue blocks were cut in 6-μm sections, placed on slides, and immediately prepared for indirect immunofluorescent staining. Section were fixed in 4% paraformaldehyde (10 min) and incubated overnight with SSEA-1 (1:100) and EMA-1 (1:50) antibodies (Hybridoma bank). Antibodies were detected with fluorescently-labelled goat anti-mouse secondary antibodies (1:100 dilution; Sigma) in 15% goat serum in DPBS for 1 h at room temperature. After washing, slides were mounted using ProLong antifade mounting medium (Molecular Probes). Gene expression: total RNA was extracted from fetal genital ridge samples with Trizol™ (Invitrogen). Any contaminating DNA was removed with RNase-free DNase I (Invitrogen). First strand cDNA synthesis was performed with SuperScript™ III RNase H-Reverse Transcriptase (Invitrogen) in the presence of RNase inhibitor (Promega). Real Time PCR amplification was performed in a BioRad iCycler™, with Platinum SYBR Green qPCR Super Mix UDG (Invitrogen). The relative quantification of the target genes was calculated with the 2-ddCt method (Livak and Schmittgen 2001 Methods 25, 402-408), after normalization against β-actin expression levels. Fragment identity was confirmed by sequencing. Our results indicate that the cortical region of the genital ridges is positive to stem cell surface markers. A larger number of positive cells was recorded in Day 24 fetuses with respect to Day 27 ones. The SSEA-1 and EMA-1 showed identical expression patterns. Similar levels of Oct4 and Nanog mRNA were detected in the genital ridges at both stages, whereas Sox2 displayed a lower abundance at Day 27. In conclusion, ovine PGC can be recognized by stem cell surface antigens and by the expression of Oct4, Nanog, and Sox2 pluripotency markers, as in mouse. The combined biomolecular and immunohistochemical approach provides a useful tool to follow the ovine PGC during in vitro culture to derive pluripotent stem cells in this species.

In vitro production and cryotolerance of prepubertal and adult goat blastocysts obtained from oocytes collected by laparoscopic oocyte-pick-up (LOPU) after FSH treatment

This study compares the developmental capacity and cryotolerance of embryos produced from oocytes of stimulated prepubertal and adult Sarda goats. Twelve prepubertal and 13 adult goats were each given 110 and 175 IU FSH, respectively, and cumulus-oocyte complexes (COCs) were collected by laparoscopic oocyte-pick-up (LOPU). After in vitro maturation, fertilisation and culture (IVMFC), blastocysts were vitrified, warmed and blastocoel re-expansion and gene expression were evaluated. Prepubertal goats produced a higher COCs number than adults (mean +/- s.e.m., 89.67 +/- 5.74 and 26.69 +/- 3.66, respectively; P < 0.01). Lower developmental competence was demonstrated in the prepubertal oocytes as shown by a higher number of COCs discarded before IVM (21.1% and 14.7% for prepubertals and adults, respectively; P < 0.01) and IVF (23.4% v. 9.1%; P < 0.01) and by the lower cleavage (55.6% and 70.3%, respectively; P < 0.01) and blastocyst rates (24.2% and 33.9%, respectively; P < 0.05). Compared with the adult, prepubertal vitrified/warmed blastocysts showed significantly (P < 0.05) lower in vitro viability, as determined by the re-expansion rate (62.5% and 40.3%). No differences were observed in the time required for blastocoel re-expansion or in cyclin B1, E-cadherin, Na/K ATPase, HSP90beta and aquaporin 3 messenger RNA quantity. These results show that in vitro-produced embryos produced from prepubertal goat oocytes have a lower developmental rate and cryotolerance compared with their adult counterparts. However, we can assume that the quality of re-expanded embryos does not differ between the two groups.

Exogenous melatonin positively influences follicular dynamics, oocyte developmental competence and blastocyst output in a goat model

The role of melatonin in modulating mammalian reproduction is of particular interest; however, its effects on ovarian follicles and their oocytes still remain to be characterized. This study determined the influence of melatonin treatment on follicular growth patterns and on in vitro oocyte developmental competence. In a first experiment, the effects of melatonin supplementation on follicular dynamics were evaluated using daily transrectal ultrasonographies for 21 days, in 7 multiparous Sarda goats receiving a subcutaneous implant of 18 mg of melatonin and in 5 control untreated does. Melatonin caused more follicular waves (5.2 +/- 0.2 versus 4 +/- 0.3; P < 0.05) as the waves were shortened at around 2 days when compared with the non-melatonin treated control goats (P < 0.001). Oocyte developmental competence was evaluated in a second experiment by applying procedures for in vitro embryo production. There were no significant differences in the total number of oocytes obtained from 6 control (n = 192) and 7 melatonin-treated (n = 265) goats given follicle stimulating hormone to induce follicular development. Differences in oocyte developmental competence between the two groups became evident after in vitro fertilization and culture; melatonin increased the rate of cleaved oocytes in comparison with control animals (82.5 versus 63.4%; P < 0.001), advanced timing of embryo development and enhanced blastocyst output (31.5 versus 16.3%; P < 0.01). However, blastocyst quality, as evaluated by cryotolerance and gene expression analysis, was not found to be different between the groups. In conclusion, in vivo melatonin treatment is beneficial for increasing ovarian follicle turnover and improving oocyte developmental competence and kinetics of the blastocyst.

177 EMBRYOS PRODUCED IN VITRO FROM PREPUBERTAL LAMB AND ADULT SHEEP OOCYTES DISPLAY DIFFERENT GENE EXPRESSION PATTERNS

Breeding from prepubertal females reduces the generation interval and increases the rate of genetic gain in animal breeding programs. Despite considerable interest in this technology, its efficiency remains too low. Reduced in vitro and in vivo developmental competence of oocytes derived from prepubertal animals have been reported in association with morphologic, metabolic, and biochemical differences. The objective of this study was to compare the relative transcript abundance of a panel of developmentally important genes in embryos produced in vitro from prepubertal lamb and adult sheep oocytes. Cumulus–oocyte complexes derived from ovaries of regularly slaughtered 1-month-old prepubertal and adult sheep were matured in vitro in TCM-199 with 10% heat-treated oestrus sheep serum (OSS), 10 μL mL–1 of FSH/LH and 100 μm cysteamine, in 5% CO2 in air at 38.5°C for 24 h. Matured oocytes were fertilized with frozen–thawed ram semen in SOF medium + 2% OSS for 22 h at 38.5°C and 5% CO2, 5% O2, and 90% N2 atmosphere. Zygotes were cultured in SOF + AA + 0.4% BSA in 5% CO2 and 5% O2 up to blastocyst stage. Three groups of 10 blastocysts for each class (4 replicates) were used to quantify the relative expression of 15 genes by reverse transcription followed by real-time PCR. The relative quantification of the transcripts was performed with the 2-ddCt method (Livak and Schmittgen 2001 Methods 25, 402–408), after normalization against the β-actin expression levels. The analysis of gene expression evidenced higher relative abundance for Aquaporin 3, P34Cdc2, cyclin B, Oct4, H2A.Z, and Nanog transcripts in sheep embryos than in prepubertal-derived ones (ANOVA; P < 0.05), while interferon τ and insulin-like growth factor (IGF) 2 mRNAs were significantly more abundant in lamb-derived embryos (ANOVA; P < 0.01). No differences were observed for the remaining analyzed transcripts (BAX, IGF2R, heat shock protein 90, NaKATPase, E-cadherin, PAP, and glyceraldehyde 3-phosphate dehydrogenase). Overall, results show that embryos produced in vitro from prepubertal and adult oocytes display different patterns of expression at the blastocyst stage. Such difference may be related to the generally observed reduced in vitro and in vivo developmental competence. Increased understanding of the gene expression status during pre-implantation development may provide valuable insights into the molecular basis underlying the very early stages of life and an opportunity for optimizing in vitro embryo production systems.

Expression pattern of zygote arrest 1 (ZAR1), maternal antigen that embryo requires (MATER), growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15) genes in ovine oocytes and in vitro-produced preimplantation embryos

The expression patterns of four maternal effect genes (MEG), namely zygote arrest 1 (ZAR1), maternal antigen that embryo requires (MATER), growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15), were determined in ovine oocytes and in vitro-produced preimplantation embryos. The existence of ZAR1 and MATER in ovine species has not been reported previously. Reverse transcription–polymerase chain reaction was performed on germinal vesicle and IVM MII oocytes, as well as in in vitro fertilised and cultured two-, four-, eight- and 12/16-cell embryos, morulae and blastocysts. Quantification of gene expression by real-time polymerase chain reaction showed the highest abundance of all transcripts analysed in the immature oocyte. During the following stages of preimplantation development, the mRNAs examined exhibited different patterns of expression, but often significant decreases were observed during maturation and maternal–embryonic transition. The transcription of the four genes did not resume with activation of the genome.

Effects of trehalose co-incubation on in vitro matured prepubertal ovine oocyte vitrification

Our aim was to evaluate if loading prepubertal ovine oocyte with trehalose would impact on their further developmental potential in vitro and if it would improve their survival to vitrification procedures. COCs matured in vitro with (TRH) or without (CTR) 100mM trehalose were tested for developmental potential after in vitro fertilization and culture. Trehalose uptake was measured by the antrone spectrophotometric assay. No differences were recorded between the two experimental groups in fertilization rates (91.1 CTR vs 92.5% TRH), cleavage rates calculated on fertilized oocytes (96.1 CTR vs 95.4% TRH), first cleavage kinetic (56.1 CTR vs 51% TRH), and blastocyst rates (14.3 CTR vs 13.0% TRH). Anthrone assay revealed that in TRH group trehalose concentration/oocyte was 2.6microM. MII oocytes were then vitrified using cryoloops in TCM 199 containing 20% FCS, sucrose 0.5M, 16.5% Me(2)SO, 16.5% EG and plunged in LN(2). After warming, oocytes from TRH and CTR groups were tested for membrane integrity using the propidium iodide (PI)/Hoechst differential staining, and for developmental ability after in vitro fertilization. Trehalose in maturation medium affected membrane resistance (P<0.01) to vitrification/warming but not fertilization and cleavage rates. The differential staining showed a lower number of PI positive cells in TRH group compared to CTR one (14.3 vs 24.7%, respectively). Fertilization rates and cleavage rates did not differ between the two groups (55.3 and 41% for TRH and 47.7 and 41.7% for CTR, respectively). In conclusion trehalose in maturation medium stabilizes cell membranes during vitrification/warming of prepubertal ovine oocytes but does not affect fertilization and cleavage rates after warming.

Effect of vitrification solutions and cooling upon in vitro matured prepubertal ovine oocytes

The vitrification procedure effects on molecular and cytoskeletal components and on developmental ability of in vitro matured prepubertal ovine oocytes were evaluated. MII oocytes were divided into three groups: (1) vitrified in cryoloops (VTR); (2) exposed to vitrification solutions and rehydrated without being plunged into liquid nitrogen (EXP); (3) without further treatment as a control (CTR). Two hours after treatment, membrane integrity, assessed by propidium iodide/Hoechst staining, was lower in VTR and EXP than in CTR (70.6%, 88.5% and 95.2%, respectively). Cleavage rate after fertilization was statistically different among all groups (21.4%, 45.4% and 82.8% for VTR, EXP and CTR groups respectively; P<0.01). Blastocyst rate in VTR (0.0%) and EXP (2.8%) groups was lower (P<0.01) than in CTR (22.8%). Maturation promoting factor activity was lower (P<0.01) in VTR and EXP groups compared with CTR at both 0 h (82.2%, 83.6% and 100%, respectively) and 2 h (60% and 53.9% and 100%, respectively) after warming. Immediately after warming VTR and EXP oocytes showed a lower rate of normal spindle and chromosome configuration compared to CTR (59.1%, 48.0% and 83.3%, respectively; P<0.01). After 2 h of culture in standard conditions the percentage of oocytes with normal spindle and chromosome organization decreased in both VTR and EXP groups compared to CTR (36.4%, 42.8% versus 87.5%, respectively). In conclusion the exposition to the tested cryoprotectant solution and the vitrification in cryoloops modified cytoskeletal components and alter biochemical pathways that compromise the developmental capacity of prepubertal in vitro matured ovine oocytes.

A Low Oxygen Atmosphere during IVF Accelerates the Kinetic of Formation of In Vitro Produced Ovine Blastocysts

Among the factors that affect in vitro embryo development, oxygen atmosphere is considered to be of great influence. In this study, we evaluated the influence of two different oxygen atmospheres during in vitro fertilization (IVF) of ovine oocytes on their developmental capacity and quality assessed by cryotolerance. Cumulus oocyte complexes derived from ovaries of slaughtered sheep were matured in vitro and subsequently fertilized under low (5%) or high (20%) oxygen atmospheres, and cultured in SOF + aa + 0.4% BSA in 5% CO2 and 5% O2 up to blastocyst stage. The cleavage rates obtained in the fertilization system at 20% O2 were significantly higher than those obtained in the 5% O2 fertilization system (61.2% vs 50.8%; p < 0.01). The distribution of cleaved oocytes at 22, 26 and 40 h of culture intervals was not different in the low or high O2 atmosphere (31.4%, 26.4% and 42.1% vs 28.0%, 29.3% and 42.7% respectively). Blastocysts output on the 6th day post-fertilization (dpf) was significantly higher when oocytes were fertilized under 5% O2 concentration (63.04% in 5% O2 vs 47.36% in 20% O2), while on the 7th dpf the higher number of blastocysts was obtained in the 20% O2 system (35.10%.in 20% O2 vs 26.09% in 5% O2). After vitrification no differences were observed between low or high oxygen atmosphere in the viability rates of blastocysts obtained on day 6 (93.6% vs 96.5%), on day 7 (46.3% vs 41.7%) and on day 8 (11.1% vs 6.6%). After differential staining, no significant differences were observed in the total cell number and inner cell mass and trophoblastic cells ratio of blastocysts produced on 6 dpf (189.6 +/- 51.3 and 0.260 +/- 0.07 vs 223.3 +/- 45.6 and 0.277 +/- 0.09), on 7 dpf (168.3 +/- 25.1 and 0.316 +/- 0.06 vs 172.1 +/- 33,6 and 0.320 +/- 0.06) and on 8 dpf (121.2 +/- 23,8 and 0.302 +/- 0.03 vs 117.0 +/- 35.1 and 0.313 +/- 0.04) under low or high oxygen atmosphere respectively). In conclusion, our data suggest that low oxygen atmosphere during IVF affects positively the production of high quality ovine blastocysts.

Effects of progestagens on follicular growth and oocyte developmental competence in FSH-treated ewes

Previous research has reported evidence for negative effects of progestagens on follicular growth and oocyte competence. In the present study, negative effects of progestagens on follicular growth and oocyte developmental competence were assessed. During the breeding season, 20 Sarda ewes were treated with two doses of cloprostenol, 10 days apart, to assure the presence of a corpus luteum (CL). On day 5 after the second cloprostenol dose, 10 ewes were treated with a progestagen sponge while 10 females remained untreated. Starting on day 7 after the second cloprostenol dose, all the ewes were treated with 6 equal doses of 24 I.U. of FSH (Ovagen, ICP, NZ), every 12h. The number of follicles > or =2mm in diameter increased (P<0.0005) in all the ewes from 24 h before to 60 h after the first FSH dose (from 12.8+/-1.1 to 23.4+/-1.3 in treated and from 12+/-0.6 to 22+/-1.2 in untreated ewes, n.s.). There were no significant differences in follicle dynamics between groups, but concentrations of estradiol in control ewes were higher than in the progestagen group (P<0.05). Twelve hours after the last FSH dose, oocytes were collected by ovum pick-up. Recovery rates were lower for progestagen-treated ewes (71.1 versus 83%; P<0.001). After IVP procedure, cleavage rate was also lower in the progestagen group (39.1 versus 82.6%; P<0.001). Furthermore, blastocysts output revealed that oocyte developmental competence was lower in progestagen group (17.3 versus 30.4%; P=0.245), although differences were not significant. These results suggest deleterious effects from progestagen on oocyte developmental competence and set the basis for new protocols for in vitro embryo production.

199 EVIDENCE FOR A NOVEL PERTURBATION IN CLONED FETUSES: MITOCHONDRIAL DNA DEPLETION

The reported mtDNA turnover and plasticity of mtDNA copy number in mammalian zygotes and early embryos (McConnel and Petrie 2004 Reprod. Biomed. Online 9, 418–424) have revealed a potential for adverse effects of in vitro embryo techniques on mtDNA and mitochondrial function. We explored the effects of in vitro fertilization (IVF) and somatic cell nuclear transfer cloning (NT) on relative mtDNA amount and phenotype in viable bovine fetuses recovered 80 days after the initiation of embryonic development (Hiendleder et al. 2004 Biol. Reprod. 71, 217–223). We sampled brain, liver, and skeletal muscle to represent all 3 embryonic germ layers, and compared IVF-fetuses (n = 24), NT-fetuses (n = 23), and fetuses generated by in vivo insemination (controls, n = 24). This experimental approach allowed us to distinguish abnormalities specific to cloning from more general consequences of in vitro embryo manipulation. We analyzed relative mtDNA amounts by real-time quantitative PCR (qPCR) and amplified a segment of the mtDNA control region that was normalized against the nuclear gene complement C3. ANOVA (SPSS 13.0) of qPCR data and phenotypic parameters revealed significant effects of fetus group on mtDNA amount in liver (P &lt; 0.05) and muscle (P &lt; 0.01), and on fetus (P &lt; 0.001), heart (P &lt; 0.001), and liver (P &lt; 0.001) weights. The mtDNA amount in all tissues from IVF-fetuses was normal, but mtDNA levels in liver (-23%; P &lt; 0.05) and muscle (-24%; P &lt; 0.01) of NT-fetuses were significantly lower than in controls. Fetuses derived from IVF- or NT-embryos were similar in weight and displayed fetal overgrowth (+19% and +22%; P &lt; 0.001), but only the NT-fetuses were affected by disproportionate hepatomegaly and cardiomegaly with 31% and 49% increases (ANCOVA; P &lt; 0.001) in their respective organ weights. This further partitioned NT-fetuses from IVF-fetuses and identified symptoms that are also encountered in mitochondrial DNA depletion syndromes (MDDS): a phenotypically heterogeneous group of human disorders characterized by loss of mtDNA from various tissues during development and associated respiratory chain dysfunction. The MDDS phenotypes have mainly been classified into a hepatocerebral (MIM 251880) or myopathic (MIM 609560) form, and neonates and infants display a spectrum of abnormalities, including hepatomegaly and cardiomegaly, that are similar or identical to phenotypic abnormalities commonly encountered in cloned mammals. Reduced mtDNA amounts in NT-fetuses could stem from perturbation of mtDNA during the reported turnover period, or be a secondary effect of epigenetic change in nuclear-encoded genes involved in mtDNA replication and stability. Mitochondrial transcription factor A (TFAM) is regulated by CpG methylation in vitro, but our real-time RT-PCR quantification of TFAM transcript in liver and muscle of a subset of NT- and control fetuses failed to detect significant differences (P &gt; 0.10). In conclusion, our observed reduction of mtDNA amount in cloned fetuses provides the molecular basis for a mitochondrial perspective on pathological phenotypes of cloned mammals, and may explain similarities to mitochondrial disease in human.

261 PHENOTYPIC CHARACTERISTICS AND TISSUE-SPECIFIC IGF2R/IGF2 EXPRESSION PARTITION BOVINE FETAL OVERGROWTH ASSOCIATED WITH IN VITRO FERTILIZATION AND SOMATIC CELL NUCLEAR TRANSFER CLONING

Large offspring syndrome (LOS) in ruminants refers to various poorly defined organ pathologies that are associated with fetal overgrowth and are encountered after a range of embryo manipulations (Rhind et al. 2003 Nat. Rev. Genet. 4, 855–864). We have explored the effects of somatic cell nuclear transfer (NT) and in vitro fertilization (IVF) on phenotype and relative expression levels of 2 imprinted genes important for fetal growth, insulin-like growth factor 2 (IGF2) and its receptor (IGF2R). Viable bovine fetuses were recovered near the end of the first trimester of pregnancy, and skeletal muscle, liver, and lung were sampled for real-time RT-PCR analyses. We compared NT-fetuses (n = 23), IVF-fetuses (n = 24), and fetuses generated by artificial insemination (controls, n = 24) in order to separate abnormalities specific to cloning from effects of in vitro gamete and embryo manipulation. Nuclear transfer and IVF-fetuses, both derived from embryos cultured with 10% estrous cow serum, demonstrated significant fetal overgrowth. The increase in body weight relative to controls was similar for both groups (+22%, P &lt; 0.001, and +19%, P &lt; 0.001, respectively), but further analyses clearly separated the NT phenotype from the IVF phenotype. The NT-fetuses were characterized by a shorter crown-rump length but larger thorax circumference, which consequently produced a significantly reduced fetus length-to-thorax circumference ratio in comparison with IVF-fetuses and controls (-9% each, P &lt; 0.0001). Absolute liver weight was significantly increased in NT- and IVF-fetuses (+62%, P &lt; 0.0001, and +20%, P &lt; 0.0001, respectively), but relative liver weight was increased only in NT-fetuses (+30%, P &lt; 0.0001). Heart (P&lt; 0.0001) and kidney (P = 0.0003) mass also showed disproportionate organomegaly in NT-fetuses only, but relative lung weight (NT, P = 0.263; IVF, P = 0.317) was not affected by either embryo technique. Transcript abundance for IGF2 and IGF2R genes were strongly correlated in muscle (r = 0.835, P &lt; 0.0001), liver (r = 0.922, P &lt; 0.0001), and lung (r = 0.772, P &lt; 0.0001). The IGF2 and IGF2R transcript levels in muscle tissue from NT-fetuses were markedly reduced in comparison with both IVF-fetuses (-31%, P &lt; 0.0001, and -41%, P &lt; 0.0001, respectively) and controls (-31%, P &lt; 0.0001, and -41%, P &lt; 0.0001, respectively). In liver tissue, however, transcript levels for NT-fetuses were similar to those of controls, and IVF-fetuses showed markedly elevated, albeit non-significant, IGF2 (+86%, P = 0.0591) and IGF2R (+54%, P = 0.1305) mRNA levels relative to controls. Our data demonstrate that seemingly similar syndromes caused by NT or IVF procedures can be clearly partitioned with respect to phenotype and IGF2/IGF2R expression.