Distribution of prepubertal and adult goat oocyte cortical granules during meiotic maturation and fertilisation: ultrastructural and cytochemical study

Follicular fluid exosome-derived miR-339-5p enhances in vitro maturation of porcine oocytes via targeting SFPQ, a regulator of the ERK1/2 pathway

In this study, we aimed to investigate cytoplasmic maturation and miRNA expression of mature oocytes cultured in porcine follicular fluid exosomes. We also examined the effect of miR-339-5p on oocyte maturation. Twenty eight differentially expressed miRNAs were detected using miRNA-seq. We then transfected cumulus oocyte complexes with miR-339-5p mimics and inhibitor during culture. The results showed that exosomes increased endoplasmic reticulum levels and the amount of lipid droplets, and decreased ROS levels, lipid droplet size, and percentage of oocytes with abnormal cortical granule distribution. Overexpressing miR-339-5p significantly decreased cumulus expansion genes, oocyte maturation-related genes, target gene proline/glutamine-rich splicing factor (SFPQ), ERK1/2 phosphorylation levels, oocyte maturation rate, blastocyst rate, and lipid droplet number, but increased lipid droplet size and the ratio of oocytes with abnormal cortical granule distribution. Inhibiting miR-339-5p reversed the decrease observed during overexpression. Mitochondrial membrane potential and ROS levels did not differ significantly between groups. In summary, exosomes promote oocyte cytoplasmic maturation and miR-339-5p regulating ERK1/2 activity through SFPQ expression, thereby elevating oocyte maturation and blastocyst formation rate in vitro.

C-Phycocyanin improves the quality of goat oocytes after in vitro maturation and vitrification

In vitro maturation (IVM) and cryopreservation of goat oocytes are important for establishing a valuable genetic bank for domesticated female animals and improving livestock reproductive efficiency. C-Phycocyanin (PC) is a Spirulina extract with antioxidant, antiinflammatory, and radical scavenging properties. However, whether PC has positive effect on goat oocytes IVM or developmental competence after vitrification is still unknown. In this study, we found that first polar body extrusion (n = 293), cumulus expansion index (n = 269), and parthenogenetic blastocyst formation (n = 281) were facilitated by adding 30 μg/mL PC to the oocyte maturation medium when compared with the control groups and that supplemented with 3, 10, 100 or 300 μg/mL PC (P < 0.05). Although PC supplementation did not affect spindle formation or chromosome alignment (n = 115), it facilitated or improved cortical granules migration (n = 46, P < 0.05), mitochondria distribution (n = 39, P < 0.05), and mitochondrial membrane potential (n = 46, P < 10-4). Meanwhile, supplementation with 30 μg/mL PC in the maturation medium could significantly inhibit the reactive oxygen species accumulation (n = 65, P < 10-4), and cell apoptosis (n = 42, P < 0.05). In addition, PC increased the oocyte mRNA levels of GPX4 (P < 0.01), and decreased the mRNA and protein levels of BAX (P < 0.01). Next, we investigated the effect of PC supplementation in the vitrification solution on oocyte cryopreservation. When compared with the those equilibrate in the vitrification solution without PC, recovered oocytes in the 30 μg/mL PC group showed higher ratios of normal morphology (n = 85, P < 0.05), survival (n = 85, P < 0.05), first polar body extrusion (n = 62, P < 0.05), and parthenogenetic blastocyst formation (n = 107, P < 0.05). Meanwhile, PC supplementation of the vitrification solution increased oocyte mitochondrial membrane potential (n = 53, P < 0.05), decreased the reactive oxygen species accumulation (n = 73, P < 0.05), promoted mitochondria distribution (n = 58, P < 0.05), and inhibited apoptosis (n = 46, P < 10-3). Collectively, our findings suggest that PC improves goat oocyte IVM and vitrification by reducing oxidative stress and early apoptosis, which providing a novel strategy for livestock gamete preservation and utilization.

Ursolic acid alleviates meiotic abnormalities induced by 3-nitropropionic acid in mouse oocytes

3-nitropropionic acid (3-NPA), a toxic metabolite produced by mold, is mainly found in moldy sugarcane. 3-NPA inhibits the activity of succinate dehydrogenase that can induce oxidative stress injury in cells, reduce ATP production and induce oxidative stress in mouse ovaries to cause reproductive disorders. Ursolic acid (UA) has a variety of biological activities and is a pentacyclic triterpene compound found in many plants. This experiment aimed to investigate the cytotoxicity of 3-NPA during mouse oocyte in vitro maturation and the protective effects of UA on oocytes challenged with 3-NPA. The results showed that UA could alleviate 3-NPA-induced oocyte meiotic maturation failure. Specifically, 3-NPA induced a decrease in the first polar body extrusion rate of oocytes, abnormal distribution of cortical granules, and an increase in the proportion of spindle abnormalities. In addition, 3-NPA caused mitochondrial dysfunction and induced oxidative stress, including decreases in the GSH, mitochondrial membrane potential and ATP levels, and increases in the ROS levels, and these effects led to apoptosis and autophagy. The addition of UA could significantly improve the adverse effects caused by 3-NPA. In general, our data show that 3-NPA affects the normal development of oocytes during the in vitro culture, and the addition of UA can effectively repair the damage caused by 3-NPA to oocytes.

Effects of Alginic Acid on the Porcine Granulosa Cells and Maturation of Porcine Oocytes

SCOPE

Alginic acid (AA) from brown algae is a marine organic compound. There is extensive use of AA in the food industry and healthcare, suggesting a high probability of AA exposure. The present study investigates the effects of AA on porcine ovarian granulosa cells (GCs) and oocytes to explore its mechanism in female reproduction because of its adverse effects on reproduction.

METHODS AND RESULTS

The study adds 20 µM AA to the porcine primary ovarian GCs medium and porcine oocyte in vitro maturation (IVM) medium. Estrogen and progesterone levels are downregulated in GCs. Reactive oxygen species are excessive, and the antioxidant capacity declines. Then mitochondria-mediated apoptosis pathway is involved in GCs apoptosis. In addition, scores of autophagosomes are found in the experimental cells. Furthermore, AA significantly inhibits the proliferation of GCs around cumulus-oocyte complexes (COCs) accompanied by abnormal spindle assembly, chromosome arrangement disorder, and aberrant cortical granules distribution in oocytes, leading to a decreased oocyte maturation rate.

CONCLUSION

These findings suggest that 20 µM AA is toxic to sow reproduction by interfering with estrogen production, oxidative stress, mitochondria-mediated apoptosis, autophagy in GCs of sows, and oocyte maturation.

Granulosa Cells Improved Mare Oocyte Cytoplasmic Maturation by Providing Collagens

Assisted reproductive technology has important clinical applications and commercial values in the horse industry. However, this approach is limited largely by the low efficiency of oocyte in vitro maturation (IVM), especially cytoplasmic maturation. To improve the efficiency of mare oocyte IVM, we evaluated the effects of co-culture with cumulus–oocyte complexes (COCs) and granulosa cells (GCs) from follicles with small (&lt;15 mm) and large diameters (&gt;35 mm). Our results showed that oocyte nucleus maturation was not significantly improved by co-culturing with GCs. Interestingly, the cytoplasmic maturation of oocytes, defined by the distribution of cortical granules and mitochondria, as well as reactive oxygen species (ROS) levels, improved dramatically by co-culture with GCs, especially those derived from small follicles. Moreover, GCs promoted cumulus cell expansion by upregulating the expression of BMP15 in oocytes. To determine the mechanism underlying the effects of GCs, the transcriptomes of GCs from large and small follicles were compared. Expression levels of COL1A2, COL6A1, and COL6A2 were significantly higher in GCs from small follicles than in those from large follicles. These three genes were enriched in the extracellular matrix proteins-receptor interaction pathway and were involved in the regulation of collagens. Taken together, our results suggest that co-culture with GCs is beneficial to oocyte cytoplasmic maturation, and the increased expression of COL1A2, COL6A1, and COL6A2 improve the mare oocyte IVM system via the regulation of collagen.

Bioengineering Approaches to Improve In Vitro Performance of Prepubertal Lamb Oocytes

Juvenile in vitro embryo technology (JIVET) provides exciting opportunities in animal reproduction by reducing the generation intervals. Prepubertal oocytes are also relevant models for studies on oncofertility. However, current JIVET efficiency is still unpredictable, and further improvements are needed in order for it to be used on a large-scale level. This study applied bioengineering approaches to recreate: (1) the three-dimensional (3D) structure of the cumulus–oocyte complex (COC), by constructing—via bioprinting technologies—alginate-based microbeads (COC-microbeads) for 3D in vitro maturation (3D-IVM); (2) dynamic IVM conditions, by culturing the COC in a millifluidic bioreactor; and (3) an artificial follicular wall with basal membrane, by adding granulosa cells (GCs) and type I collagen (CI) during bioprinting. The results show that oocyte nuclear and cytoplasmic maturation, as well as blastocyst quality, were improved after 3D-IVM compared to 2D controls. The dynamic 3D-IVM did not enhance oocyte maturation, but it improved oocyte bioenergetics compared with static 3D-IVM. The computational model showed higher oxygen levels in the bioreactor with respect to the static well. Microbead enrichment with GCs and CI improved oocyte maturation and bioenergetics. In conclusion, this study demonstrated that bioengineering approaches that mimic the physiological follicle structure could be valuable tools to improve IVM and JIVET.

HDAC11 inhibition disrupts porcine oocyte meiosis via regulating α-tubulin acetylation and histone modifications

HDAC11, the sole member of HDAC class IV family, plays vital roles in activating mitosis and apoptosis of tumor cells, but its functions in meiosis are rarely investigated. In the present study, the effect of HDAC11 on meiosis during porcine oocytes maturation was fully studied. The results showed that HDAC11 inhibition by its specific inhibitor JB-3-22 dramatically decreased the porcine oocyte maturation rate by disturbing spindle organization and chromosomes alignment without affecting the cytoplasmic maturation. Further study indicated that HDAC11 inhibition significantly elevated the acetylation levels of α-tubulin and H4K16, which are crucial for spindle organization and chromosomes alignment. Moreover, immunofluorescence staining results showed that HDAC11 inhibition also disturbed other meiosis-related histone modifications, such as increased H3S10pho, H4K5ac and H4K12ac levels and reduced H3T3pho level. Furthermore, RNA-seq analysis results indicated that HDAC11 inhibition disturbed porcine oocytes transcriptome (157 up-regulation, 106 down-regulation). In addition, HDAC11 inhibition compromised oocytes quality and subsequent development after parthenogenetic activation, which may be caused by the aberrant nuclear maturation and transcriptome expression profile during oocytes maturation. Therefore, our results elucidate the function of HDAC11 in porcine oocytes maturation and embryos development through regulating α-tubulin acetylation, meiosis-related histone modifications and transcriptome.

The methylation status in GNAS clusters May Be an epigenetic marker for oocyte quality

During follicle growth, DNA methylation is gradually established, which is important for oocyte developmental competence. Due to the facts that oocytes from prepubertal individuals show reduced developmental outcomes when compared to those from sexually mature individuals, and the fact that oocytes derived from in vitro follicle culture have much lower developmental competence, it is worth exploring whether prepubertal superovulation and in vitro follicle culture will cause changes in DNA methylation imprinting status in oocytes. In this study, we found that the CpG island in maternally imprinted GNAS clusters was hypermethylated in the MII-stage oocytes from sexually mature mice, but was hypomethylated in oocytes from prepuberty individuals. The GNAS clusters in the MII-stage oocytes obtained by in vitro follicle culture showed heterogeneous methylation levels, indicating different qualities of oocytes, however, three other maternally imprinted genes, Peg1, Lot1 and Impact, were all hypermethylated in the MII-stage oocytes derived from both prepubertal superovulation and in vitro follicle culture. Taken together, the findings suggest that the methylation status in GNAS clusters may potentially represent a novel epigenetic marker for oocyte quality detection.

Small Ruminants: Prepubertal Oocyte Donors

In vitro embryo production using oocytes of prepubertal females is named JIVET (juvenile in vitro embryo technologies). The aim of the JIVET is to increase genetic gain by shortening the generation interval in breeding programs. In this chapter we describe the methodology currently used in our laboratory for producing in vitro embryos from prepubertal sheep (90-120 days old) and goats (30-45 days old).Briefly, we obtain cumulus-oocyte complexes (COCs) from slaughtered female ovaries. These COCs are in vitro matured in TCM199 with 10% (v/v) fetal bovine serum (FBS) at 38.5 °C in a humidified air atmosphere with 5% CO₂ for 24 h. The next day we collect ejaculates from males of proven fertility and select the most motile spermatozoa by density gradient. Following coincubation with mature COCs, presumptive zygotes and embryos are cultured in SOF for 8 days at 38.5 °C, 90% N₂, 5% CO₂, 5% O₂, and 100% humidity to obtain blastocysts.

Resveratrol supplementation during in vitro maturation improves embryo development of prepubertal goat oocytes selected by brilliant cresyl blue staining

This study aimed to investigate the effect of resveratrol supplementation in maturation medium on the developmental ability and bioenergetic\oxidative status of prepubertal goat oocytes selected by brilliant cresyl blue (BCB). Oocytes collected from slaughterhouse-derived ovaries were selected by 13 µM BCB staining and classified as grown BCB+ and growing BCB- oocytes. All oocytes were matured in vitro in our conventional maturation medium and supplemented with 1 µM (BCB+R and BCB-R) and without (Control groups: BCB+C and BCB-C) resveratrol. After 24 h, IVM-oocytes were fertilized with fresh semen and presumptive zygotes were in vitro cultured for 8 days. Oocytes were assessed for blastocyst development and quality, mitochondrial activity and distribution, and levels of GSH, ROS, and ATP. BCB+R (28.3%) oocytes matured with resveratrol presented significantly higher blastocyst development than BCB+C (13.0%) and BCB- groups (BCB-R: 8.3% and BCB-C: 4.7%). Resveratrol improved blastocyst development of BCB-R oocytes at the same rate as BCB+C oocytes. No differences were observed in blastocyst quality among groups. GSH levels were significantly higher in resveratrol groups (BCB+R: 36554.6; BCB-R: 34946.7 pixels/oocyte) than in control groups (BCB+C: 27624.0; BCB-C: 27655.4 pixels/oocyte). No differences were found in mitochondrial activity, ROS level, and ATP content among the groups. Resveratrol-treated oocytes had a higher proportion of clustered active mitochondria in both BCB groups (BCB+R: 73.07%; BCB-R: 79.16%) than control groups (BCB+C: 19.35%; BCB-C: 40%). In conclusion, resveratrol increased blastocyst production from oocytes of prepubertal goats, particularly in better quality oocytes (BCB+).

The Role of Oocyte Organelles in Determining Developmental Competence

The ability of an oocyte to undergo successful cytoplasmic and nuclear maturation, fertilization and embryo development is referred to as the oocyte’s quality or developmental competence. Quality is dependent on the accumulation of organelles, metabolites and maternal RNAs during the growth and maturation of the oocyte. Various models of good and poor oocyte quality have been used to understand the essential contributors to developmental success. This review covers the current knowledge of how oocyte organelle quantity, distribution and morphology differ between good and poor quality oocytes. The models of oocyte quality are also described and their usefulness for studying the intrinsic quality of an oocyte discussed. Understanding the key critical features of cytoplasmic organelles and metabolites driving oocyte quality will lead to methods for identifying high quality oocytes and improving oocyte competence, both in vitro and in vivo.

Current status of in vitro embryo production in sheep and goats

Sheep and goat production is an important economic activity in Spain with an increasing interest in milk production. Multiovulation and Embryo Transfer (MOET) and In vitro Embryo Production (IVEP) are assisted reproductive technologies aimed at increasing the genetic diffusion of females. In vitro embryo production is a multi-step methodology comprising the following procedures: (i) In vitro Maturation (IVM) of oocytes recovered directly from the follicles, (ii) In vitro Fertilization (IVF) or co-incubation of capacitated spermatozoa with in vitro matured oocytes and (iii) In vitro culture (IVC) of zygotes up to the blastocyst stage. In vitro embryo production from oocytes recovered from prepubertal females is called JIVET (Juvenile in vitro Embryo Transfer) and allows shortened generation intervals and increased genetic gain. Embryo production together with embryo cryoconservation would allow large-scale embryo marketing, a pathogen-free genetic movement and easier and cheaper germplasm commercial transactions. Commercial Embryo activity in small ruminants is low compared to cows in the European Union (data from the European Embryo Transfer Association) and in the world (data from the International Embryo Transfer Association). There is less IVEP research in small ruminants compared to other livestock species. The aim of this review was to provide an overview of the current status of IVEP of small ruminant with an emphasis on (i) description of the main methodologies currently used for IVM, IVF and IVC of embryos (ii) comparing procedures and outputs from JIVET and IVEP of adult females and (iii) the future research perspectives of this technology.

Pretreatment of in vitro matured bovine oocytes with docetaxel before vitrification: Effects on cytoskeleton integrity and developmental ability after warming

The stabilization of spindle fibersis important for successful vitrification of bovine oocytes because microtubules and other cytoskeleton fibers (CSF) can be damaged during vitrification, resulting in failure of fertilization after thawing. Docetaxel, a stabilizing agent, could potentially reduce CSF damage of bovine oocytes induced during vitrification. However, there have been no reports on the effects of docetaxel on their vitrification. Experiment 1 was conducted to investigate the effects of various doses of docetaxel (0.0, 0.05, 0.5, 5.0 and 50 μM) in preincubation medium of in vitro matured (IVM) bovine oocytes on their developmental ability after in vitro fertilization (IVF). The results show that 0.05 μM docetaxel had no adverse effect on embryo development, while docetaxel at a concentration of ⩾0.5 μM inhibited development. Experiments 2 and 3 were conducted to investigate the effects of preincubation of IVM bovine oocytes with 0.05 μM docetaxel for 30 min prior to vitrification-warming on CSF integrity (Experiment 2), and on oocyte survival and viability after IVF (Experiment 3). When preincubated with 0.05 μM docetaxel for 30 min before vitrification, post-thawed oocytes had less CSF damage and higher survival rates compared with those untreated with docetaxel before vitrification. Surviving oocytes also had higher rates of cleavage and development to the blastocyst stage after IVF. In conclusion, preincubation of IVM bovine oocytes with 0.05 μM docetaxel for 30 min before vitrification was effective at preventing CSF damage during vitrification, and improving oocyte viability after warming and subsequent cleavage and blastocyst formation after IVF.

In vitro maturation is slowed in prepubertal lamb oocytes: ultrastructural evidences

BACKGROUND

In vitro maturation (IVM) of immature oocytes retrieved from unstimulated ovaries may avoid side effects connected to hyperstimulation during IVF procedures, including the risk of cancer recurrence. In humans, the scarce availability of immature oocytes limits morphological studies. The monovular ovine may represent an experimental model for IVM studies.

METHODS

To assess if the scarce developmental competence of prepubertal oocytes (PO) is related to morphological changes we analyzed, by light and transmission electron microscopy, cumulus-oocyte-complexes (COCs) from lambs (30-40 days old) and sheep (4-6 years old) at sampling and after 7 h, 19 h, 24 h of IVM. Meiotic progression was determined at the same time points.

RESULTS

At sampling, the germinal vesicle (GV) of PO was round and centrally or slightly eccentrically located, whereas in adult oocytes (AO) it was irregularly shaped and flattened against the oolemma. PO, differently from AO, showed numerous trans-zonal projections. Organelles, including cortical granules (CGs), were more abundant in AO. After 7 h, the percentage of AO that underwent GVBD-MI transition increased significantly. In PO, the oolemma was juxtaposed to the ZP; in AO, it showed several spikes in correspondence of cumulus cells (CC) endings. In PO, organelles and isolated CGs were scattered in the ooplasm. In AO, groups of CGs were also present under the oolemma. After 19 h, PO underwent GVBD-MI transition; their oolemma showed several spikes, with CC projections retracted and detached from the ZP. AO underwent MI-MII transition; their oolemma regained a round shape. CGs were located beneath the plasmalemma, arranged in multiple, continuous layers, sometime discontinuous in PO. After 24 h, both groups reached the MII-stage, characterized by a regular oolemma and by expanded CCs. PO showed CGs distributed discontinuously beneath the oolemma, while AO showed a continuous monolayer of CGs.

CONCLUSIONS

Even if PO were able of reaching morphological maturation after 24 h of IVM, our ultrastructural analysis allowed detecting the presumptive sequence of cytoplasmic alterations connected with the delay of nuclear maturation, that might explain the reduced developmental competence of such oocytes. Data from the sheep model are of interest for zootechny, and provide an experimental basis for improving human IVM technology.

Fertilization capacity of cryopreserved Iberian ibex epididymal sperm in a heterologous in vitro fertilization assay

In vitro fertilization (IVF) can be used to assess the fertilization capacity of sperm. Heterologous IVF may be useful when assessing that of wild animals as it is often difficult to obtain adequate numbers of naturally corresponding oocytes. The aim of the present study was to assess the fertilization capacity of frozen–thawed ibex epididymal spermatozoa via heterologous IVF involving the oocytes of prepubertal domestic goats. The effect on fertilization and embryo development of adding oestrous sheep serum (ESS) to the fertilization medium was also examined. Cumulus–oocyte complexes (COCs) were matured in TCM-199 for 24–27 h at 38.5°C in a 5% CO2 in air atmosphere. Frozen–thawed epididymal spermatozoa were selected by density gradient centrifugation. After maturation, the oocytes were co-incubated with spermatozoa in synthetic oviductal fluid (SOF) with different concentrations of ESS: SOF-C (0%), SOF-2 (2%) and SOF-20 (20%). At 17 h post-insemination (hpi), zygotes with one female and one male pronucleus (2PN) were categorised as normal; zygotes with 3PN were recorded as polyspermic, and oocytes with 1PN as asynchronous. Cleavage and blastocyst development were assessed at 48 and 168 hpi respectively. The percentage of zygotes with 2PN was higher in the SOF-2 than in the SOF-20 treatment group (27.7% versus 2.9% P < 0.05). The percentage of blastocysts formed with the SOF-C, SOF-2 and SOF-20 treatments were 1.1%, 7.5% and 0% respectively. These results show that the presence of 2% ESS achieves better results than the use of no serum or the standard 20% concentration. Heterologous IVF may be an effective method for predicting the fertilization capacity of ibex spermatozoa, and therefore perhaps that of other wild mountain ungulates.

Developmental potential of prepubertal mouse oocytes is compromised due mainly to their impaired synthesis of glutathione

Although oocytes from prepubertal animals are found less competent than oocytes from adults, the underlying mechanisms are poorly understood. Using the mouse oocyte model, this paper has tested the hypothesis that the developmental potential of prepubertal oocytes is compromised due mainly to their impaired potential for glutathione synthesis. Oocytes from prepubertal and adult mice, primed with or without eCG, were matured in vitro and assessed for glutathione synthesis potential, oxidative stress, Ca²⁺ reserves, fertilization and in vitro development potential. In unprimed mice, abilities for glutathione synthesis, activation, male pronuclear formation, blastocyst formation, cortical granule migration and polyspermic block were all compromised significantly in prepubertal compared to adult oocytes. Cysteamine and cystine supplementation to maturation medium significantly promoted oocyte glutathione synthesis and blastocyst development but difference due to maternal age remained. Whereas reactive oxygen species (ROS) levels increased, Ca²⁺ storage decreased significantly in prepubertal oocytes. Levels of both catalytic and modifier subunits of the γ-glutamylcysteine ligase were significantly lower in prepubertal than in adult oocytes. Maternal eCG priming improved all the parameters and eliminated the age difference. Together, the results have confirmed our hypothesis by showing that prepubertal oocytes have a decreased ability to synthesize glutathione leading to an impaired potential to reduce ROS and to form male pronuclei and blastocysts. The resulting oxidative stress decreases the intracellular Ca²⁺ store resulting in impaired activation at fertilization, and damages the microfilament network, which affects cortical granule redistribution leading to polyspermy.

New insights into placozoan sexual reproduction and development

Unraveling animal life cycles and embryonic development is basic to understanding animal biology and often sheds light on phylogenetic relationships. A key group for understanding the evolution of the Metazoa is the early branching phylum Placozoa, which has attracted rapidly increasing attention. Despite over a hundred years of placozoan research the life cycle of this enigmatic phylum remains unknown. Placozoa are a unique model system for which the nuclear genome was published before the basic biology (i.e. life cycle and development) has been unraveled. Four organismal studies have reported the development of oocytes and one genetic study has nourished the hypothesis of sexual reproduction in natural populations at least in the past. Here we report new observations on sexual reproduction and embryonic development in the Placozoa and support the hypothesis of current sexual reproduction. The regular observation of oocytes and expressed sperm markers provide support that placozoans reproduce sexually in the field. Using whole genome and EST sequences and additional cDNA cloning we identified five conserved sperm markers, characteristic for different stages in spermatogenesis. We also report details on the embryonic development up to a 128-cell stage and new ultrastructural features occurring during early development. These results suggest that sperm and oocyte generation and maturation occur in different placozoans and that clonal lineages reproduce bisexually in addition to the standard mode of vegetative reproduction. The sum of observations is best congruent with the hypothesis of a simple life cycle with an alternation of reproductive modes between bisexual and vegetative reproduction.

Dynamic modulation of cytoskeleton during in vitro maturation in human oocytes

OBJECTIVE

To investigate the role of cytoskeleton in several important dynamic events during in vitro maturation of human oocytes.

STUDY DESIGN

Human germinal vesicle stage oocytes were divided randomly into control and study groups. After cultured for 24 hours, chromatin state and position, spindle formation and migration, cortical granules, and mitochondria distribution were evaluated.

RESULTS

In colchicine group, spindles did not form. Cortical granules migrated to the cortex but mitochondria maintained the peripheral distribution pattern in most of the oocytes. In cytochalasin B group, the migration of spindle and chromosomes to the cortex was prohibited. Microfilaments disruption influenced cortical granules migration but not redistribution of mitochondria.

CONCLUSION

Meiosis progression could not go beyond metaphase I stage when microtubule or microfilament polymerization was prohibited in human oocytes. The migration of cortical granules to the cortex and redistribution of mitochondria to the inner cytoplasm were mediated by microfilaments and microtubules, respectively.

Identification and role of carbohydrates on the surface of gametes in the zebra mussel, Dreissena polymorpha

The objective of this study is to identify surface carbohydrates on zebra mussel, Dreissena polymorpha, eggs and sperm and to analyze their potential role in fertilization. The lectins WGA, Con A, LcH, LTA, SBA, PNA, and GSII were tested for affinity to both eggs and sperm. WGA, Con A, and LcH uniformly labeled eggs. LTA, SBA, PNA, and GSII did not. WGA labeled the entire sperm surface including the unreacted acrosome. Labeling by Con A, LcH, LTA, SBA, PNA, and GSII was restricted to the inner acrosomal region of acrosome-reacted sperm. GSII labeling suggests the presence of N-acetyl-d-glucosamine (GlcNAc) only in the inner acrosomal membrane and not on eggs. GlcNAc blocked sperm-egg binding. GSII labeling was associated with a ring-like structure at the site of sperm entry intimately associated with sperm-egg binding. Nonfertilizing sperm were detached from the egg surface along with the GSII basal ring about 15 min postinsemination in a process blocked by trypsin inhibitors.

Follicular, oocyte and embryo features related to metabolic status in primiparous lactating does fed with high-fibre rearing diets

Fertility of primiparous lactating does in the early postpartum (pp) period is very low mainly due to pronounced deficient energy intake, influencing oocyte and embryo developmental competence. The hypothesis used in this work was that high-lignin fibre diet supplied during the rearing period could increase feed intake and, consequently, improve the reproductive physiology and metabolic status of primiparous does in the early pp period. Diets with high-lignin [HL: 15.8% dry matter (DM)] or standard-lignin content (SL: 4.9% DM) were supplied until parturition time. No diet effects in serum oestradiol, progesterone concentrations and follicle categories were found in the histological study. Metaphase II rate of in vitro-matured oocytes was significantly higher in the SL vs the HL group (p < 0.001). Cytoplasmically degenerated oocytes (in terms of abnormal distribution of cortical granules) and follicular atresia rate were significantly lower in the SL group than in the HL group (p < 0.05 and p < 0.005 respectively). In addition, HL-fed does showed lower number of viable embryos and higher rate of retarded in vivo-recovered embryos compared with the SL group (p < 0.05). Neither in vitro embryo development of viable embryos nor conception rate was significantly different between groups. Feed intake increased during the first pregnancy in the HL group (p < 0.05), but not during early lactation. Serum protein, non-esterified fatty acid and leptin concentrations, as well as estimated body composition were similar in does fed with both diets. In conclusion, the enhancement of reproductive management by using highly lignified products in rearing diets does not seem to report physiological reproductive benefits affecting oocyte maturation rate and embryo viability in primiparous lactating does.

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.

Prematuration of bovine oocytes with butyrolactone I: Effects on meiosis progression, cytoskeleton, organelle distribution and embryo development

The effects of prematuration (PM) of bovine oocytes with butyrolactone I (BLI) for 24h on meiosis progression, cell structures and embryo development were assessed. Germinal vesicle (GV) rates decreased (97.4-65.1%, P<0.05) with decreasing BLI concentrations (100-25microM). Without BSA in PM medium, GV rates were similar (98.7-97.2, P>0.05) with low BLI (10-25microM). After in vitro maturation (IVM) for 24h, metaphase II (MII) rates for controls (IVM only) were similar (91.1%, P>0.05) to PM with 10microM BLI in BSA-free medium (B10=91.5%) and 100microM BLI in medium with BSA (B100=92.4%). Meiosis resumption occurred earlier in treated oocytes (71.4-74.3% in GV for B10 and B100, respectively, after 6h IVM compared with 97.3% in controls, P<0.05). By 18h of IVM, most oocytes reached MII (72.0-78.9%, P>0.05). Microtubules and microfilaments were unaffected by BLI. Cortical granules (CG) migration was reversibly blocked by BLI. Mitochondria translocation was partially blocked by PM culture and after IVM more oocytes in B10 and B100 (95.2 and 98.2%, respectively) had mitochondria translocated to a mature pattern (all cytoplasm) than controls (81.5%, P<0.05). Cleavage rates were similar (81-87%, P>0.05), but blastocysts (day 7) decreased in B100 (33.0%, P<0.05) compared with controls and B10 (38.3 and 41.6%, respectively). Day 8 hatching rates (11.0-19.2%) and mean total cell numbers (136-150) were similar (P>0.05). PM did not improve oocyte competence but also did not cause major structural alterations, suggesting that PM may be improved and used to study the mechanisms involved in oocyte differentiation.

Effect of 2-mercaptoethanol and cysteine supplementation during in vitro maturation on the developmental competence of oocytes from hormone-stimulated lambs

The objective was to determine the effect of 2-mercaptoethanol and cysteine on in vitro developmental competence of oocytes from lambs (4-8-week old) stimulated with eCG and pFSH. Oocytes were matured in medium (TCM199) with no supplement (Control group) or with 100 microM 2-mercaptoethanol and 600 microM cysteine (GSH group). Oocytes from adult sheep were also included (Adult group). The addition of 2-mercaptoethanol and cysteine did not improve nuclear maturation or microtubule configuration 12, 15, 18, or 24 h after placement in maturation medium. Sperm head decondensation and male pronucleus formation were evaluated at 6, 12, and 18 h after commencement of IVF; sperm decondensation appeared earlier in the GSH group (6h after the start of IVF). There were differences (P<0.05) between the Control group and the GSH and Adult groups for: fertilization rate at both 12 h (55.4, 77.0, and 80.6%, respectively) and 18 h (67.9, 86.9, and 88.7%); parthenogenesis rate at both 12 h (25.0, 10.8, and 5.6%) and 18 h (28.3, 9.8, and 4.5%); and polyspermy rate at 18 h (26.4, 4.9, and 5.7%). Blastocyst rate at 7d was higher in the GSH group than the Control group (23.9% vs. 14.9%, P<0.05), but both were lower (P<0.05) than the Adult group (38.3%). The addition of 2-mercaptoethanol and cysteine improved sperm decondensation and rates of fertilization and the blastocyst development to 7d, with no effect on blastocyst rate at 9 d.

Total RNA and protein content, Cyclin B1 expression and developmental competence of prepubertal goat oocytes

The aim of this study was to examine the relationship between the developmental competence of oocytes and their total RNA and protein contents, and the level of Cyclin B1 transcription. Ovaries from prepubertal goats were collected from a slaughterhouse. Oocytes were recovered by slicing and those with two or more layers of cumulus cells and homogenous cytoplasm were matured in vitro (20-25 oocytes per drop) for 27 h. Both before and after IVM, samples of oocytes were denuded and categorised into four group treatments by diameter (<110 microm, 110-125 microm, 125-135 microm; >135 microm), separated into sub-groups of 10 oocytes per treatment-replicate and stored in liquid nitrogen until total RNA content analysis by spectophotometry, total protein content analysis by a colorimetric assay and Cyclin B1 transcription analysis by RT-PCR. For the study of developmental competence, the rest of the matured oocytes were fertilised in vitro in groups of 20-25 for 24 h. Presumptive zygotes were denuded, sorted into the four categories of diameter noted above, and placed into culture drops in groups of 18-25 for in vitro culture. Cleavage rate was evaluated at 48 hpi and embryo development at 8 d post-insemination. There were four replicates of each treatment for each assay or evaluation point of the experiment. There were no significant differences between the size categories of oocytes at collection in total RNA content, total protein content and Cyclin B1 mRNA. There were significant differences (P<0.05) in the expression of Cyclin B1 before IVM with oocytes in the >135 mm diameter category having the highest value for this variant. There were no significant differences in these characteristics between the categories of oocyte diameter after IVM except in respect of total RNA content, which was lower for the largest size of oocytes (>135 microm; mean+/-S.D.=12.3+/-1.84 ng/oocyte) than the other three size groups (19.2+/-1.38-22.1+/-4.44 ng/oocyte; P<0.05). Significant differences (P<0.05) in cleavage rate were observed between the different oocyte size categories (<110 microm, 3.0%; 110-125 microm, 32%; 125-135 microm, 50%; >135 microm, 73%). Only oocytes >125 microm diameter developed to the blastocyst stage (125-135 microm, 7%; >135 microm, 10%). This study showed that the RNA content and the Cyclin B1 RNA expression of prepubertal goat oocytes, and their development to embryos varied between the different size categories of the oocytes.

Effects of pre-treating in vitro-matured bovine oocytes with the cytoskeleton stabilizing agent taxol prior to vitrification

The purpose of this study was to determine the efficacy of pre-treating mature bovine oocytes with Taxol before vitrification by the open pulled Straw method (OPS). We evaluated the effects of pre-treating the oocytes with 1 microM Taxol on chromosome organization, spindle morphology, cortical granule distribution and the ability of fertilized oocytes to develop to the blastocyst stage. After calf or cow oocyte vitrification without Taxol, significantly higher proportions of spindle abnormalities in the form of abnormal spindle structures or dispersed or decondensed chromosomes were observed compared to fresh control oocytes. In contrast, when we compared calf oocytes pre-treated with Taxol before vitrification with control calf oocytes, similar percentages of oocytes showing a normal spindle morphology were observed. The percentages of oocytes with a peripheral cortical granule (CG) distribution increased when the oocytes were pretreated with Taxol and vitrified, while oocytes vitrified without Taxol pre-treatment gave rise to higher cortical distribution percentages. Cleavage and blastocyst rates were significantly lower for vitrified versus untreated oocytes, both in cow and calf oocytes. Significantly higher cleavage rates were obtained when calf and cow oocytes were vitrified with Taxol. Pre-treatment with Taxol before cow oocyte vitrification yielded significantly higher blastocyst rates. Calf oocytes, however, were unable to develop to the blastocyst stage, irrespective of previous Taxol treatment. These results indicate that the pre-treatment of oocytes with Taxol before vitrification helps to reduce the damage induced by the cryopreservation process, and potentially improves the subsequent development of vitrified bovine oocytes. Summary sentence: Pre-treatment of oocytes with Taxol before vitrification helps to reduce the damage induced by vitrification and potentially improves the development of vitrified bovine oocytes.

Effects of in vitro maturation of monkey oocytes on their developmental capacity

The study of in vitro maturation (IVM) of rhesus monkey oocytes has important implications for biomedical research and human infertility treatment. In vitro-matured rhesus monkey oocytes show much less developmental potential than IVM oocytes of other species. Since about 1980 when rhesus monkey IVM, in vitro fertilization (IVF) and in vitro embryo culture (IVC) systems were established, numerous efforts have been made to improve the developmental competence of oocytes and to understand the mechanisms regulating oocyte maturation. This review describes recent progress in this area, particularly the effects of factors such as steroid hormones, energy substrates, amino acids, ovarian follicle status, maternal age and breeding season on the developmental competence, gene expression patterns and genome integrity of rhesus IVM oocytes.

Cortical granules behave differently in mouse oocytes matured under different conditions

BACKGROUND

To better understand the differences between in vivo (IVO) and in vitro (IVM) matured oocytes, we studied the chronological changes in cortical granule (CG) distribution and nuclear progression during maturation, and the competence of CG release and embryo development of mouse oocytes matured under different conditions.

METHODS

Oocytes matured in vivo or in different culture media were used and CG distribution and release were assessed by fluorescein isothiocyanate-labelled Lens culinaris agglutinin and laser confocal microscopy.

RESULTS

Tempos of nuclear maturation and CG redistribution were slower, and competence for CG exocytosis, cleavage and blastulation were lower in the IVM oocytes than in the IVO oocytes. These parameters also differed among oocytes matured in different culture media. Hypoxanthine (HX, 4 mM) blocked germinal vesicle breakdown (GVBD), postponed CG migration and prevented CG-free domain (CGFD) formation. Cycloheximide (CHX) facilitated both GVBD and CG migration, but inhibited CGFD formation. The presence of serum in maturation media enhanced CG release after aging or activation of oocytes. Maintenance of germinal vesicle intact for some time by a trace amount (0.18 mM) of HX was beneficial to oocyte cytoplasmic maturation.

CONCLUSION

CGs behaved differently in mouse oocytes matured under different conditions, and cytoplasmic maturity was not fully achieved in the IVM oocytes.

Update on reproductive biotechnologies in small ruminants and camelids

Recent advances in reproductive biotechnologies in small ruminants include improvement of methods for in vitro production of embryos and attempts at spermatogonial stem cell transplantation. In vitro production of embryos by IVM/IVF, intra-cytoplasmic sperm injection (ICSI), or nuclear transfer (NT) has been made possible by improvements in oocyte collection and maturation techniques, and early embryo culture systems. However, in vitro embryo production still is not very efficient due to several limiting factors affecting the outcome of each step of the process. This paper discusses factors affecting in vitro embryo production in small ruminants and camelids, as well as preliminary results with the technique of spermatogonial stem cell transplantation.