The morphological and functional ultrastructure of cells in pre-implantation embryos

Cells of pre-implantation embryos are equipped with many morphological and functional systems through which they can synthesize specific proteins and effectively ensure the protection of early embryonic development. Here we present evidence for the existence of these systems in morphologically normal and abnormal bovine blastocyst stage embryos in vivo at the ultrastructural and actin cytoskeleton levels. The appearance of organelles in the trophectoderm (TE) and inner cell mass (ICM) cells, responsible for their synthetic activities and their role in the development of early bovine embryos are described. We point out the importance of endocytic processes and the participation of extracellular vesicles in the formation of intercellular contacts and homeostasis of the embryo microenvironment. Several changes in the ultrastructural morphology of embryos produced by different methods (ICSI, parthenogenetic AC/DC electrical activation, IVF with separated sperm) and freezing/thawed embryos are described. We also show alterations occurred in the organelles after viral contamination of embryos with BHV-1 and BVDV viruses, and in embryos from over-conditioned cows. Recorded changes in organelles and appearance of cellular autophagic structures (vesicles, multivesicular bodies and autophagolysosomes) may negatively affect embryo metabolism and lead to the emergence of pathological processes in TE and ICM cells of preimplantation embryos.

SA-Net: A scale-attention network for medical image segmentation

Semantic segmentation of medical images provides an important cornerstone for subsequent tasks of image analysis and understanding. With rapid advancements in deep learning methods, conventional U-Net segmentation networks have been applied in many fields. Based on exploratory experiments, features at multiple scales have been found to be of great importance for the segmentation of medical images. In this paper, we propose a scale-attention deep learning network (SA-Net), which extracts features of different scales in a residual module and uses an attention module to enforce the scale-attention capability. SA-Net can better learn the multi-scale features and achieve more accurate segmentation for different medical image. In addition, this work validates the proposed method across multiple datasets. The experiment results show SA-Net achieves excellent performances in the applications of vessel detection in retinal images, lung segmentation, artery/vein(A/V) classification in retinal images and blastocyst segmentation. To facilitate SA-Net utilization by the scientific community, the code implementation will be made publicly available.

Improved cryopreservation of in vitro produced bovine embryos using FGF2, LIF, and IGF1

In vitro embryo production systems are limited by their inability to consistently produce embryos with the competency to develop to the blastocyst stage, survive cryopreservation, and establish a pregnancy. Previous work identified a combination of three cytokines [fibroblast growth factor 2 (FGF2), leukemia inhibitory factor (LIF), and insulin-like growth factor 1 (IGF1)], called FLI, that we hypothesize improve preimplantation development of bovine embryos in vitro. To test this hypothesis, FLI was supplemented into oocyte maturation or embryo culture medium. Embryos were produced in vitro using abattoir-derived oocytes and fertilized with sperm from a single bull known to have high fertility. After an 18-20 h fertilization period, putative zygotes were cultured in synthetic oviductal fluid (SOF) for 8 days. The addition of FLI to the oocyte maturation medium increased (P < 0.05) the dissociation of transzonal projections at 12, 18, and 24 h of maturation, as well as, the proportion of oocytes that reached the metaphase II stage of meiosis. Additionally, lipid content was decreased (P < 0.05) in the blastocyst stage embryo. The addition of FLI during the culture period increased development to the blastocyst stage, cytoskeleton integrity, and survival following slow freezing, as well as, decreased post thaw cell apoptosis (P < 0.05). In conclusion, the supplementation of these cytokines in vitro has the potential to alleviate some of the challenges associated with the cryo-survival of in vitro produced bovine embryos through improving embryo development and embryo quality.

Selenoprotein I is essential for murine embryogenesis

Selenoprotein I (SELENOI) is an ethanolamine phosphotransferase that catalyzes the third reaction of the Kennedy pathway for the synthesis of phosphatidylethanolamine. Since the role of SELENOI in murine embryogenesis has not been investigated, SELENOI-/+ mating pairs were used to generate global KO offspring. Of 323 weanling pups, no homozygous KO genotypes were found. E6.5-E18.5 embryos (165 total) were genotyped, and only two E18.5 KO embryos were detected with no discernable anatomical defects. To screen embryos prior to uterine implantation that occurs ~ E6, blastocyst embryos (E3.5-E4.4) were flushed from uteruses of pregnant females and analyzed for morphology and genotype. KO embryos were detected in 5 of 6 pregnant females, and 7 of the 32 genotyped embryos were found to be SELENOI KO that exhibited no overt pathological features. Overall, these results demonstrate that, except for rare cases (2/490 = 0.4%), global SELENOI deletion leads to early embryonic lethality.

Individually cultured bovine embryos produce extracellular vesicles that have the potential to be used as non-invasive embryo quality markers

Extracellular vesicles (EVs) are membrane-bound biological nanoparticles (NPs) and have gained wide attention as potential biomarkers. We aimed to isolate and characterize EVs from media conditioned by individually cultured preimplantation bovine embryos and to assess their relationship with embryo quality. Presumptive zygotes were cultured individually in 60 μl droplets of culture media, and 50 μl of media were collected from the droplets either on day 2, 5 or 8 post-fertilization. After sampling, the embryo cultures were continued in the remaining media until day 8, and the embryo development was evaluated at day 2 (cleavage), day 5 (morula stage) and day 8 (blastocyst stage). EVs were isolated using qEVsingle® columns and characterized. Based on EV Array, EVs isolated from embryo conditioned media were strongly positive for EV-markers CD9 and CD81 and weakly positive for CD63 and Alix among others. They had a cup-like shape typical to EVs as analyzed by transmission electron microscopy and spherical shape in scanning electron microscopy, and hence regarded as EVs. However, the NPs isolated from control media were negative for EV markers. Based on nanoparticle tracking analysis, at day 2, the mean concentration of EVs isolated from media conditioned by embryos that degenerated after cleaving (8.25 × 10⁸/ml) was higher compared to that of embryos that prospectively developed to blastocysts (5.86 × 10⁸/ml, p < 0.05). Moreover, at day 8, the concentration of EVs isolated from media conditioned by degenerating embryos (7.17 × 10⁸/ml) was higher compared to that of blastocysts (5.68 × 10⁸/ml, p < 0.05). Furthermore, at day 8, the mean diameter of EVs isolated from media conditioned by degenerating embryos (153.7 nm) was smaller than EVs from media conditioned by blastocysts (163.5 nm, p < 0.05). In conclusion, individually cultured preimplantation bovine embryos secrete EVs in the culture media and their concentration and size are influenced by embryo quality and may indicate their prospective development potential.

Blastulation of a zygote to a hatched blastocyst without any clear cell division: an observational finding in a time-lapse system after in vitro fertilization

PURPOSE

To describe an interesting not previously described morphokinetic finding.

METHODS

Retrospective case report of a couple undergoing controlled ovarian stimulation (COS) followed by in vitro fertilization and blastocyst transfer.

RESULTS

We identified a unique finding of blastulation of a fertilized human zygote after conventional in vitro fertilization. The fertilized zygote did not show any clear cytokinesis until approximately 107 h post insemination, when it started dividing into a blastocyst. By 113 h post insemination, inner cell mass and trophectoderm cells could be clearly distinguished and the blastocyst was completely hatched by 136 h post insemination.

CONCLUSION

Time-lapse systems offer more detailed observations of embryonic development. Here, we report an atypical development of an embryo that was not described previously. We hope to become an insightful discussion among peers and incentive the publication of such findings in the future.

Melatonin promotes human oocyte maturation and early embryo development by enhancing clathrin-mediated endocytosis

Embryo development potential and reproductive clinical outcomes are all deeply rooted in oocyte maturation. Melatonin has been reported to promote oocyte maturation as an antioxidant in nonprimate species. Its antioxidative functions also help reduce plasma membrane rigidity, which facilitates clathrin-mediated endocytosis (CME). Whether melatonin has effects on human oocyte maturation by regulating CME is worthy of exploration. In this study, we found that the optimal melatonin concentration for human oocyte maturation was 10^-11  M, and the maturation rate of this group was 71.9% (P = .03). The metaphase II (MII) stage oocytes obtained by in vitro maturation with 10^-11  M melatonin had a significantly higher fertilization rate (81.4% vs 61.4%, respectively, P = .017) and blastocyst rate (32.2% vs 15.8%, respectively, P = .039) compared to controls. During maturation, antioxidative melatonin greatly enhanced CME and decreased intra-oocyte cAMP level. The former was evidenced by the increasing numbers of coated pits and vesicles, and the upregulated expression of two major CME markers-clathrin and adaptor protein-2 (AP2). CME inhibitor dynasore increased intra-oocyte cAMP level and blocked oocyte maturation, and melatonin could partly rescue oocyte maturation and significantly elevate the expression of clathrin and AP2 in the presence of dynasore. Therefore, we conclude that melatonin could promote human oocyte maturation and early embryo development through enhancing CME.

Clinical outcomes after IVF or ICSI using human blastocysts derived from oocytes containing aggregates of smooth endoplasmic reticulum

In this study the clinical and neo-natal outcomes after transfer of blastocysts derived from oocytes containing aggregates of smooth endoplasmic reticulum (SER) were compared between IVF and intracytoplasmic sperm injection (ICSI) cycles. Clinical and neo-natal outcomes of blastocysts in cycles with at least one SER metaphase II oocyte (SER + MII; SER + cycles) did not significantly differ between the two insemination methods. When SER + MII were cultured to day 5/6, fertilization, embryo cleavage and blastocyst rates were not significantly different between IVF and ICSI cycles. In vitrified-warmed blastocyst transfer cycles, the clinical pregnancy rates from SER + MII in IVF and ICSI did not significantly differ. In this study, 52 blastocysts (27 IVF and 25 ICSI) derived from SER + MII were transferred, yielding 15 newborns (5 IVF and 10 ICSI) and no malformations. Moreover, 300 blastocysts (175 IVF and 125 ICSI) derived from SER-MII were transferred, yielding 55 newborns (24 IVF and 31 ICSI cycles). Thus, blastocysts derived from SER + cycles exhibited an acceptable ongoing pregnancy rate after IVF (n = 125) or ICSI (n = 117) cycles. In conclusion, blastocysts from SER + MII in both IVF and ICSI cycles yield adequate ongoing pregnancy rates with neo-natal outcomes that do not differ from SER-MII.

Topology of Chromosomes 18 and X in Human Blastomeres from 3- to 4-Day-old Embryos

The positions of chromosomes 18 and X fluorescence in situ hybridization signals were analyzed in blastomeres generated from human in vitro fertilization 3- to 4-day-old embryos after preimplantation screening of aneuploidy of chromosomes 13, 16, 18, 21, 22, X, and Y. Fluorescent signal localization compared with a three-dimensional sphere model of random signal distribution revealed significant differences, providing evidence of peripheral localization of chromosome 18 in aneuploid ( p=0.0013) and aneuploid/euploid blastomeres ( p=0.0011). No differences were found in localization of chromosome 18 in euploid and in chromosome X in euploid and aneuploid blastomeres.

Quantitative non-invasive cell characterisation and discrimination based on multispectral autofluorescence features

Automated and unbiased methods of non-invasive cell monitoring able to deal with complex biological heterogeneity are fundamentally important for biology and medicine. Label-free cell imaging provides information about endogenous autofluorescent metabolites, enzymes and cofactors in cells. However extracting high content information from autofluorescence imaging has been hitherto impossible. Here, we quantitatively characterise cell populations in different tissue types, live or fixed, by using novel image processing and a simple multispectral upgrade of a wide-field fluorescence microscope. Our optimal discrimination approach enables statistical hypothesis testing and intuitive visualisations where previously undetectable differences become clearly apparent. Label-free classifications are validated by the analysis of Classification Determinant (CD) antigen expression. The versatility of our method is illustrated by detecting genetic mutations in cancer, non-invasive monitoring of CD90 expression, label-free tracking of stem cell differentiation, identifying stem cell subpopulations with varying functional characteristics, tissue diagnostics in diabetes, and assessing the condition of preimplantation embryos.

Characterization of SCF-Complex during Bovine Preimplantation Development

The degradation of maternal proteins is one of the most important events during early development, and it is presumed to be essential for embryonic genome activation (EGA), but the precise mechanism is still not known. It is thought that a large proportion of the degradation of maternal proteins is mediated by the ubiquitin-proteolytic system. In this study we focused on the expression of the Skp1-Cullin1-F-box (SCF) complex, a modular RING-type E3 ubiquitin-ligase, during bovine preimplantation development. The complex consists of three invariable components—Cul1, Skp1, Rbx1 and F-box protein, which determines the substrate specificity. The protein level and mRNA expression of all three invariable members were determined. Cul1 and Skp1 mRNA synthesis was activated at early embryonic stages, at the 4c and early 8c stage, respectively, which suggests that these transcripts are necessary for preparing the embryo for EGA. CUL1 protein level increased from MII to the morula stage, with a significant difference between MII and L8c, and between MII and the morula. The CUL1 protein was localized primarily to nuclei and to a lesser extent to the cytoplasm, with a lower signal in the inner cell mass (ICM) compared to the trophectoderm (TE) at the blastocyst stage. The level of SKP1 protein significantly increased from MII oocytes to 4c embryos, but then significantly decreased again. The localization of the SKP1 protein was analysed throughout the cell and similarly to CUL1 at the blastocyst stage, the staining was less intensive in the ICM. There were no statistical differences in RBX1 protein level and localization. The active SCF-complex, which is determined by the interaction of Cul1 and Skp1, was found throughout the whole embryo during preimplantation development, but there was a difference at the blastocyst stage, which exhibits a much stronger signal in the TE than in the ICM. These results suggest that all these genes could play an important role during preimplantation development. This paper reveals comprehensive expression profile, the basic but important knowledge necessary for further studying.

Irregular cleavage of early preimplantation human embryos: characteristics of patients and pregnancy outcomes

PURPOSE

This is a retrospective analysis of the morphokinetics, prevalence, and implantation potential of embryos with irregular first and second cleavages as identified by time-lapse microscopy.

METHODS

The study included 253 women who underwent 387 assisted reproduction treatments with intracytoplasmic sperm injection (ICSI). Each patient was assigned to one of three groups based on embryo cleavage results. In group I, one to two embryos per cycle showed irregular cleavage; group II, at least three embryos with abnormal cleavage; and in group III (the control group), all embryos cleaved normally. The number of embryos that cleaved from 1 to ≥3 cells or from 2 to ≥5 cells for each patient was recorded. Their prevalence and association with women's characteristics and pregnancy outcome were evaluated.

RESULTS

The prevalence of irregular cleavage was 15.6 % among 1772 ICSI embryos. In 101 cycles, 1-2 embryos per cycle showed irregular cleavage (group I). In 32 cycles, at least 3 embryos showed abnormal cleavage (group II). In 254 cycles, all embryos cleaved normally (group III). The average age of the women in group II was significantly lower in comparison with groups I and III (32.5 ± 4.2 vs. 35.1 ± 4.9 and 35.5 ± 5.1, respectively, p < 0.02). In comparison of groups I and II, the odds ratio for ≥3 embryos with irregular cleavage in women younger than 35 was 3.48 (95 % CI, 1.28 to 9.46). Embryos with irregular cleavage were transferred in 16 women. Three live births were achieved following the transfer of single blastocysts derived from embryos with irregular cleavage from two to five cells.

CONCLUSIONS

Early embryos with irregular cleavage are significantly more prevalent in younger women. When these embryos develop to the blastocyst stage, they may have normal implantation potential, leading to the birth of healthy babies.

A SIMPLE AND EFFICIENT VITRIFICATION METHOD FOR IN-STRAW DILUTION AND DIRECT TRANSFER OF BOVINE EMBRYOS

BACKGROUND

An easy and user friendly protocol that produces consistent results will facilitate the commercial application of embryo vitrification technology in the field.

OBJECTIVE

This study was designed to develop a simple and efficient vitrification, in-straw dilution and direct transfer method for bovine embryos.

METHODS

After being vitrified and in-straw thawed, in vivo-derived and in vitro-produced bovine embryos were subjected to in vitro culture or embryo transplantation.

RESULTS

There were no significant differences (P > 0.05) in survival rates (100.0% vs. 93.9%) and expansion rates (93.8% vs. 87.5%) between in vivo-derived and in vitro-produced blastocysts after vitrification and in-straw dilution. And there was also no significant difference (P > 0.05) in conception rates (56.5% vs. 58.8%) after ET between cryopreserved and fresh in vivo-derived blastocysts.

CONCLUSION

Vitrification using EG-based vitrification solution and in-straw dilution with PBS-based diluent is a simple and efficient method for cryopreservation and direct transfer of bovine embryos.

MicroRNA in situ hybridization on whole-mount preimplantation embryos

Whole-mount in situ hybridization (WISH) using antisense probes is widely used to visualize RNA sequences in embryos and to determine the precise site of expression in the different cells or tissues. The target sequence is hybridized with an antisense RNA probe, followed by visual or fluorescence detection to measure the site and level of expression. However, the detection of short RNA molecules is hampered by the reduced stringency of the probes for short transcripts. Here, we describe a procedure for WISH detection of short RNA molecules, like miRNAs, in mammalian preimplantation embryos using LNA-modified probes with high sensitivity and specificity.

Nitric oxide modulates mitochondrial activity and apoptosis through protein S-nitrosylation for preimplantation embryo development

PURPOSE

Previous studies reported that patients with endometriosis had excess nitric oxide (NO) in the reproductive tract and poor embryo development in IVF cycles. This study aims to elucidate the effects of NO on early embryo development.

METHODS

Zygotes from superovulated B6CBF1 mice were cultured to blastocysts in a variety of media. Sodium nitroprusside (SNP) and N(G)-nitro-L-arginine (LNA) were added to the culture medium as a NO donor and a NO synthase inhibitor, respectively. The localization and fluorescence intensity of S-nitrosylated (SNO) proteins within 2-cell stage embryos were analyzed with confocal microscopy. Apoptosis and ATP production in the blastocysts were measured.

RESULT(S)

Subsequent to NO exposure, the SNO proteins mainly colocalized with the mitochondria and endoplasmic reticulum and the intensity of SNO proteins increased. The addition of a quanylate cyclase inhibitor and a cyclic GMP mimic agent induced nonsignificant changes in SNO proteins, whereas addition of a superoxide scavenger or a reduced form of glutathione rescued the embryos from the effects of NO. However, superoxide scavenger supplementation resulted in decreased blastocyst ATP production.

CONCLUSION(S)

Elevated NO exerts deleterious effects on embryo development, possibly through protein S-nitrosylation in the mitochondria and endoplasmic reticulum. Including glutathione as a component in the culture medium might counteract this effect.

Effects of partial or complete laser-assisted hatching on the hatching of mouse blastocysts and their cell numbers

BACKGROUND

It is still debatable whether a full-thickness assisted hatching (AH) is better than the partial zona thinning. In this research, we used a mouse model to study the effect of partial and complete laser-AH on the rate of completely hatched blastocyst and their cell numbers.

METHODS

In experiment 1, mouse morulae had 0, 1, 2 or 3 full-thickness openings of 10 microns created in the zona pellucida with an infrared laser beam. In the second experiment, 0, 1 and 2 openings of 20 microns were studied. In the third experiment, a full-thickness opening of 20 microns or quarter-thinning of the zonal circumference to a depth of 90% was compared with non-AH controls.

RESULTS

No difference in blastocyst formation was found in laser-treated groups and in the controls. In experiment 1, the rate of completely hatched blastocysts was significantly lower than the controls. In experiment 2 when the size of the opening was increased, blastocysts completely hatched at a significantly higher rate than that in the controls. In experiment 3, the rate of completely hatched blastocysts was the highest in the full-thickness group. Cell numbers in completely hatched blastocysts from both AH groups were significantly fewer than those in the controls.

CONCLUSIONS

Full-thickness opening resulted in a higher rate of completely hatched blastocysts than quarter zonal-thinning and controls, but the cell numbers were significantly decreased.

Label-free subcellular 3D live imaging of preimplantation mouse embryos with full-field optical coherence tomography

Early patterning and polarity is of fundamental interest in preimplantation embryonic development. Label-free subcellular 3D live imaging is very helpful to its related studies. We have developed a novel system of full-field optical coherence tomography (FF-OCT) for noninvasive 3D subcellular live imaging of preimplantation mouse embryos with no need of dye labeling. 3D digitized embryos can be obtained by image processing. Label-free 3D live imaging is demonstrated for the mouse embryos at various typical preimplantation stages with a spatial resolution of 0.7 [micro sign]m and imaging rate of 24 fps. Factors that relate to early patterning and polarity, such as pronuclei in zygote, shapes of zona pellucida, location of second polar body, cleavage planes, and the blastocyst axis, can be quantitatively measured. The angle between the two second cleavage planes is accurately measured to be 87 deg. It is shown that FF-OCT provides a potential breakthrough for early patterning, polarity formation, and many other preimplantation-related studies in mammalian developmental biology.

[Immunofluorescent detection of nuclear actin in early mouse embryos]

In this work, preimplantation mouse embryos were used as a model to study the distribution of nuclear actin in a comparative aspect. To reveal actin, different polyclonal antibodies raised against the C-terminal domains of actin were applied. An antibody raised against the C-terminal marks nuclear actin more intensively as compared to the cytoplasm, especially in areas of condensed chromatin. The fluorescence of the nuclei was less apparent when an antibody against N-terminus is applied. This antibody revealed actin associated with low condensed chromatin. In 2-cell but not in elder embryos, some Cajal bodies were also stained with this antibody. However, the pattern of actin association with transcriptions sites does not depend on the type of anti-actin antibodies used in this study. We suggest that the distinctions of staining patterns revealed using different anti-actin antibodies may be explained by different capacity of the antibodies for staining, but not by their selective detection of different functional forms of nuclear actin in mouse embryos.

The relationship between meiotic spindle imaging and outcome of intracytoplasmic sperm injection: a retrospective study

Meiotic spindle analysis with a non-invasive technique, the PolScope, is used to protect the meiotic spindle from damage during microinjection. To evaluate the predictive feature of PolScope, we have designed a retrospective study to analyse the correlation between the meiotic spindle visualisation with regard to spindle location and outcomes of assisted reproductive technologies (ART), including patient age, previous cycles, the number of the collected oocytes, fertilisation rates (FR), pronuclear scoring (PNS) and embryo scoring of the days from two to five. All of the data belonging to 1496 oocytes from 190 patients were statistically analysed. We found that the oocytes having PolScope visualised spindle have higher FR, and also observed that when the spindle located at 0°-30° according to the first polar body, gave the highest FR. PNS gave higher scores in the spindle visualised group, but spindle angle did not affect PNS outcomes. Although a correlation was found between spindle visualisation and developed embryo qualities, particularly at day 2 and 3, spindle angles did not affect embryo quality. We conclude that PolScope microscopy has an efficiency to estimate FR, and cleavage stage embryo development.

Is pronuclear scoring a really good predictor for ICSI cycles?

BACKGROUND/AIMS

Since the assessments of the morphology of oocytes, zygotes and/or embryos are of crucial importance to select the best candidate for pregnancy, many morphological evaluation tools have been proposed. Although embryo scoring, particularly cleavage and blastocyst stages, is more convincing due to successful results, zygote scoring still have a bias as different outcomes. In the current study, we designed a prospective study to test the reliability of zygote scoring by focusing on zygote evaluation techniques and its relation with embryo development and embryo selection for transfer.

METHODS

A total of 1215 mature oocytes from 139 couples were evaluated for the study.

RESULTS

There is no correlation between published zygote scoring technique and embryo development.

CONCLUSIONS

We conclude that the inconsistency of data obtained from zygote scoring might be caused by the static nature of pronuclear stage embryos and thus pronuclear scoring seems to be unreliable evaluation technique for embryo selection.

Intra- and interobserver analysis in the morphological assessment of early stage embryos during an IVF procedure: a multicentre study

BACKGROUND

Quality control programs are necessary to maintain good clinical practice. Embryo grading has been described as one of the external quality assurance schemes. Although the evaluation of embryos is based on the assessment of morphological characteristics, considerable intra- and inter-observer variability has been described. In this multicentre study, the variability in the embryo evaluation has been evaluated using morphological characteristics on day 1, day 2 and day 3 of embryo development.

METHODS

Five embryologists of four different IVF centers participated in this study. Multilevel images of embryos were presented on a website at different time points to evaluate intra-and inter-observer agreement in the assessment of embryo morphology. The embryos were evaluated on day 1, day 2 and day 3 of their development and each embryologist had to decide if the embryo had to be transferred, cryopreserved or discarded.

RESULTS

Both intra-observer agreement and inter-observer agreement were good to excellent for the position of the pronuclei on day 1, the number of blastomeres on day 2 and day 3 and the clinical decision (transfer, cryopreservation, discard). For all other characteristics (size of pronuclei, presence of cytoplasomic halo, degree of fragmentation and size of blastomeres) the intra- and inter-observer agreement was moderate to very poor.

CONCLUSIONS

Mono- or multicentre quality control on embryo scoring by morphological assessment can easily be performed through the design of a simple website. In the future the website design can be adapted to generate statistical feedback upon scoring and can even include a training module.

Autophagy regulates embryonic survival during delayed implantation

Delayed implantation, considered a state of suspended animation, is widespread in mammals. Blastocysts under this condition remain dormant for an extended period but resume implantation competence upon favorable conditions. The underlying mechanism by which extended longevity of dormant blastocysts is maintained is not clearly understood. Using autophagy markers and the well-defined delayed implantation model in mice, we show that autophagy is important for the extended longevity of dormant blastocysts in utero during delayed implantation. However, prolonged dormancy leads to reduced developmental competency of blastocysts and cellular damage with compromised pregnancy outcome. Estrogen supplementation, which activates implantation of dormant blastocysts, induces the formation of multivesicular bodies in the trophectoderm in vivo. Collectively, our results suggest that autophagy is a critical cellular mechanism that is utilized for the prolonged survival of dormant blastocysts.

Characterization of human PGD blastocysts with unbalanced chromosomal translocations and human embryonic stem cell line derivation?

Novel embryonic stem cell lines derived from embryos carrying structural chromosomal abnormalities obtained after preimplantation genetic diagnosis (PGD) are of interest to study in terms of the influence of abnormalities on further development. A total of 22 unbalanced blastocysts obtained after PGD were analysed for structural chromosomal defects. Morphological description and chromosomal status of these blastocysts was established and they were used to derive human embryonic stem cell (ESC) lines. An outgrowth of cells was observed for six blastocysts (6/22; 27%). For two blastocysts, the exact morphology was unknown since they were at early stage, and for four blastocysts, the inner cell mass was clearly visible. Fifteen blastocysts carried an unbalanced chromosomal defect linked to a reciprocal translocation, resulting in a positive outgrowth of cells for five blastocysts. One human ESC line was obtained from a blastocyst carrying a partial chromosome-21 monosomy and a partial chromosome-1 trisomy. Six blastocysts carried an unbalanced chromosomal defect linked to a Robertsonian translocation, and one showed a positive outgrowth of cells. One blastocyst carried an unbalanced chromosomal defect linked to an insertion and no outgrowth was observed. The efficiency of deriving human ESC lines with constitutional chromosomal disorders was low and probably depends on the initial morphological aspect of the blastocysts and/or the type of the chromosomal disorders.

Kinetic markers of human embryo quality using time-lapse recordings of IVF/ICSI-fertilized oocytes

A time-lapse system was used to study the timing and coordination of events during early development from zygote to cleavage stage embryo. The aim was to identify markers linked to good-quality embryos and implantation. A total of 102 fertilized oocytes were followed for 20-24 h. Events such as appearance and disappearance of (pro)nuclei and timing and synchronization of cell cleavage were logged as time points after fertilization. Averages for these events and their synchrony were calculated and linked with fertilization method, embryo quality and implantation success. Fertilized oocytes that developed into > or =4-cell embryos had an earlier pronuclei disappearance and first cleavage than those that developed to 3- or 2-cell embryos. Intracytoplasmic sperm injection-fertilized 4-cell embryos spent a significantly shorter period as 2-cell compared with IVF-fertilized embryos (P = 0.0090). Development in the time-lapse system was similar to their siblings cultured in normal incubators, suggesting that the data from the time-lapse system can be extrapolated to the clinic's laboratory setting. Early disappearance of pronuclei and onset of first cleavage after fertilization was correlated with a higher number of blastomeres on day 2 after oocyte retrieval. In addition, synchrony in appearance of nuclei after the first cleavage was significantly associated with pregnancy success (P < 0.05).

Can a genetically-modified organism-containing diet influence embryo development? A preliminary study on pre-implantation mouse embryos

In eukaryotic cells, pre-mRNAs undergo several transformation steps to generate mature mRNAs. Recent studies have demonstrated that a diet containing a genetically modified (GM) soybean can induce modifications of nuclear constituents involved in RNA processing in some tissues of young, adult and old mice. On this basis, we have investigated the ultrastructural and immunocytochemical features of pre-implantation embryos from mice fed either GM or non- GM soybean in order to verify whether the parental diet can affect the morpho-functional development of the embryonic ribonucleoprotein structural constituents involved in pre-mRNA pathways. Morphological observations revealed that the general aspect of embryo nuclear components is similar in the two experimental groups. However, immunocytochemical and in situ hybridization results suggest a temporary decrease of pre-mRNA transcription and splicing in 2-cell embryos and a resumption in 4-8-cell embryos from mice fed GM soybean; moreover, pre-mRNA maturation seems to be less efficient in both 2-cell and 4-8-cell embryos from GM-fed mice than in controls. Although our results are still preliminary and limited to the pre-implantation phases, the results of this study encourage deepening on the effects of food components and/or contaminants on embryo development.

Molecular and cellular aspects of facultative delayed implantation in the mouse

Various aspects of RNA, DNA and protein synthesis, as well as cellular fine structure, were examined in mouse embryos during the developmental diapause associated with delayed implantation, and during the reactivation of the embryo either by hormonal administration or by culture in vitro. The findings from these studies demonstrate that a cessation of DNA synthesis and mitosis, and a marked decline in the level of protein synthesis, but not of RNA synthesis, accompany diapause. Reactivation of the blastocyst results in the resumption of DNA synthesis and cell division, as well as in quantitative and qualitative changes in protein synthesis. At the fine-structural level diapause is indicated by the accumulation of lipid-like vacuoles, microfilaments, a basal lamina coating trophectodermal cells and the disassembly of polysomes into ribosomes. Significantly, nucleolar morphology remains unaltered during diapause and cisternae of the rough-surfaced endoplasmic reticulum persist at least for the first five days of delay. Reactivation of diapausing blastocysts is associated with the reassembly of polysomes and the accumulation of large quantities of an amorphous material within the cisternae of the rough-surfaced endoplasmic reticulum. Studies of blastocyst growth and development in vitro suggest experimental approaches to the question of the regulation delayed implantation. Finally, the role of ionic balances and concentrations in the control of the onset, maintenance and termination of delayed implantation in the mouse is discussed.

Changes in the surface of the mouse blastocyst at implantation

Implantation is a critical event, and perhaps the earliest one, in the maternal recognition of pregnancy. Information transfer from conceptus to mother might occur during, and subsequent to, implantation at the level of cell surface interaction. Therefore, attempts have been made both to identify the phases of implantation during which changes in the blastocyst surface occur and to characterized such changes. In vitro, blastocysts have been found to go through a series of discrete steps which are analogous to implantation in utero, and these steps can be retarded or prevented by the use of either suboptimal culture media or an inappropriate substratum. Morphological surface changes are not apparent when the blastocyst becomes adherent to the substratum; however, marked differences in blastocyst surface structure are revealed by scanning electron microscopy at the onset of trophoblast outgrowth. Studies at the molecular level implicate collagen as having a role in blastocyst adhesiveness, but other cell surface components are also likely to be involved.

The temporal relationship between oocyte maturation and early fertilisation events in relation to the pre-ovulatory LH peak and preimplantation embryo development in red deer (Cervus elaphus)

The temporal relationships among oocyte maturation, gamete transport and fertilisation following the pre-ovulatory luteinsing hormone surge in red deer were established; and secondly, early preimplantation development to the blastocyst stage in relation to the onset of oestrus was determined for red deer. In the first series of observations, oestrus was synchronised in April (N=22), for the fixed time recovery of gametes from 0 to 36 h after the estimated pre-ovulatory LH peak. Matings were observed and the time of the LH peak was determined from the retrospective analysis of blood plasma collected at 3h intervals. Gametes were recovered surgically and the meiotic status of follicular and ovulated oocytes assessed. Spermatozoa were recovered from the oviduct and their motility analysed by videomicroscopy. Nineteen of 22 hinds exhibited a pre-ovulatory LH surge and were observed to mate. Oocyte metaphase I occurred between 11 and 18 h, and metaphase II was completed within the follicle between 20 and 25 h following the pre-ovulatory LH peak. Fertilised ova were recovered from 30 to 36 h in both the ampulla and isthmic portions of the oviduct. Motile spermatozoa were first recovered from the isthmus and the ampulla at 13 and 21 h, respectively, after the LH peak. Hyperactive spermatozoa were observed in both the isthmus and the ampulla flushings but only from the eight hinds that had ovulated. In the second series of observations, 16 mature hinds were synchronised and allocated to groups for embryo collection on days 3, 5 and 7 after oestrus. Eight embryos were recovered; an 8-cell at 90 h, 3 morulae at 137, 138 and 186 h, and 4 blastocysts at 180, 182 and 190 h post-mating. Blastocysts were only recovered from the uterine horns and the mean+/-S.E.M. number of nuclei per blastocyst was 93.5+/-10.0 with a range of 66-114 cells. The results of this study will improve the application of assisted reproductive technologies to red deer as they indicate that oocyte maturation, fertilisation and early embryonic development of the red deer is similar to other domestic ruminants with the exception that the red deer embryo enters the uterus at the blastocyst stage.

Mitochondria in stem cells

The current status of knowledge about mitochondrial properties in mouse, monkey and human embryonic, adult and precursor stem cells is discussed. Topics include mitochondrial localization patterns, oxygen consumption and ATP content in cells as they relate to the maintenance of stem cell properties and subsequent differentiation of stem cells into specific cell types. The significance of the perinuclear arrangement of mitochondria, which may be a characteristic feature of stem cells, as well as the expression of mitochondrial DNA regulatory proteins and mutations in the mitochondrial stem cell genome is also discussed.

Active caspase-3 and ultrastructural evidence of apoptosis in spontaneous and induced cell death in bovine in vitro produced pre-implantation embryos

In this study we investigated chronological onset and involvement of active caspase-3, apoptotic nuclear morphology, and TUNEL-labeling, as well as ultrastructural evidence of apoptosis, in both spontaneous and induced cell death during pre-implantation development of bovine in vitro produced embryos. Pre-implantation embryos (2-cell to Day 8 blastocysts) were cultured with either no supplementation (untreated) or with 10 microM staurosporine for 24 hr (treated). Embryos were subjected to immunohistochemical staining of active caspase-3, TUNEL-reaction for detection of DNA degradation and DAPI staining for detection of apoptotic nuclear morphology, and subjected to fluorescence microscopy. Additionally, treated and untreated blastocysts were fixed and processed for ultrastructural identification of apoptosis. Untreated embryos revealed no apoptotic features at 2- and 4-cell stages. However, active caspase-3 and apoptotic nuclear morphology were observed in an untreated 8-cell stage, and TUNEL-labeling was observed from the 16-cell stage. Blastomeres concurrently displaying all apoptotic features were present in a few embryos at 16-cell and morula stages and in all blastocysts. All three features were observed from the 8-cell stage in treated embryos, and blastomeres with apoptotic features appeared more numerous in treated than in untreated embryos. Ultrastructural evidence of apoptosis occurred with a comparable distribution pattern as apoptotic features detected by fluorescence microscopy in both treated and untreated blastocysts. Activation of caspase-3 is likely involved in both spontaneous and induced apoptosis in bovine pre-implantation embryos, and immunohistochemical staining of active caspase-3 may be used in combination with other markers to identify apoptosis in pre-implantation embryos.

Visualization of cartilage formation: insight into cellular properties of skeletal progenitors and chondrodysplasia syndromes

The cellular events underlying skeletal morphogenesis and the formation of cartilage templates are largely unknown. We generated an imaging system to dynamically visualize limb mesenchymal cells undergoing successive phases in cartilage formation and to delineate the cellular function of key regulators of chondrogenesis found mutated in chondrodysplasia syndromes. We uncovered an unsuspected role for Sox9 in control of cell morphology, independent from its major downstream target ColIIa, critically required for the mesenchyme-to-chondrocyte transition. In contrast, Bmp signaling regulates a cellular program we term "compaction" in which mesenchymal cells acquire a cohesive cell behavior required to delineate the boundaries and size of cartilage elements. Moreover, we visualized labeled progenitor cells from different regions of the limb bud and identified unique cellular properties that may direct their contribution toward specific skeletal elements such as the humerus or digits. These findings shed light on the cellular basis for chondrodysplasia syndromes and formation of the vertebrate skeleton.

Human embryos developing in vitro are susceptible to impaired epithelial junction biogenesis correlating with abnormal metabolic activity

BACKGROUND

Blastocyst biogenesis occurs over several cell cycles during the preimplantation period comprising the gradual expression and membrane assembly of junctional protein complexes which distinguish the outer epithelial trophectoderm (TE) cells from the inner cell mass (ICM). In the human, TE integrity and the formation of a junctional seal can often be impaired. Embryos likely to result in a successful pregnancy after transfer are mostly selected according to morphological criteria. Recent data suggest that non-invasive measurement of amino acid turnover may be useful to complement such morphological scores. Whether morphological and metabolic criteria can be linked to poor TE differentiation thereby underpinning developmental predictions mechanistically remains unknown.

METHODS

We examined TE intercellular junction formation in human embryos by immunofluorescence and confocal microscopy and correlated this process with morphological criteria and amino acid turnover during late cleavage.

RESULTS

Our results show that TE differentiation may be compromised by failure of membrane assembly of specific junction constituents. This abnormality relates more closely to metabolic profiles than morphological criteria.

CONCLUSION

Our data identify that amino acid turnover can predict TE differentiation. These findings are the first to link two mechanisms, metabolism and junction membrane assembly, which contribute to early embryo development.

Molecular dynamics of heterochromatin protein 1beta, HP1beta, during mouse preimplantation development

To elucidate the molecular dynamics of HP1beta in mouse preimplantation embryos, we examined the localization, dynamics, and mobility of HP1beta in the (pro)nucleus by live cell imaging. Time-lapse observation revealed that the chromatin association of HP1beta is regulated in a cell cycle-dependent manner. HP1beta was localized in the interphase nucleus and was dynamically dissociated from the nucleus during the metaphase stage. The HP1beta assembly and clustered heterochromatin structure were both found in the nuclei of 2-cell and later-stage embryos. Moreover, fluorescent recovery after photobleaching analysis implied that HP1beta is more freely mobile in the pronucleus of the 1-cell embryo than in the 4-cell nucleus. These results suggest that the chromatin configuration may be regulated by the stability and mobility of chromatin-associated proteins including HP1beta during early embryonic stages.

Eomes::GFP-a tool for live imaging cells of the trophoblast, primitive streak, and telencephalon in the mouse embryo

Expression of T-box family member Eomesodermin (Tbr2) is spatiotemporally restricted in the mouse embryo; initially expressed in extraembryonic lineages in the sequential progression from the trophectoderm of the blastocyst, its derivatives the extraembryonic ectoderm, and thereafter the chorion, in addition to the visceral endoderm and primitive streak at gastrula stages, and the telencephalon at later stages. We describe the spatiotemporal expression of GFP in embryos of a Tg(Eomes::GFP) BAC transgenic strain, and have compared it with the localization of endogenous Eomes transcripts and protein. Our analysis reveals the following: (1) robust easily visualized reporter expression in live hemizygous transgenic embryos, (2) increased levels of expression in live homozygous transgenic embryos that are compatible with embryo viability, and (3) a close correlation between endogenous Eomes and GFP reporter expression in BAC transgenic embryos. These features establish the Tg(Eomes::GFP) BAC transgenic strain as a novel reagent for both live imaging and the isolation of Eomes expressing cells from specific locations within the embryo.

The effect of osmotic stress on the cell volume, metaphase II spindle and developmental potential of in vitro matured porcine oocytes

Porcine animal models are used to advance our understanding of human physiology. Current research is also directed at methods to produce transgenic pigs. Cryobanking gametes and embryos can facilitate the preservation of valuable genotypes, yet cryopreserving oocytes from pigs has proven very challenging. The current study was designed to understand the effects of anisotonic solutions on in vitro matured porcine oocytes as a first step toward designing improved cryopreservation procedures. We hypothesized that the proportion of oocytes demonstrating a normal spindle apparatus and in vitro developmental potential would be proportional to the solution osmolality. Oocytes were incubated for 10 min at 38 degrees C in various hypo- or hypertonic solutions, and an isotonic control solution and then assessed for these two parameters. Our results support the hypothesis, with an increasing proportion of spindles showing a disrupted structure as the levels of anisotonic exposure diverge from isotonic. Only about half of the oocytes maintained developmental potential after exposure to anisotonic solutions compared to untreated controls. Oocyte volume displayed a linear response to anisotonic solutions as expected, with an estimated relative osmotically inactive cell volume of 0.178. The results from this study provide initial biophysical data to characterize porcine oocytes. The results from future experiments designed to determine the membrane permeability to various cryoprotectants will allow predictive modeling of optimal cryopreservation parameters and provide a basis for designing improved cryopreservation procedures.

Isolation and characterization of porcine visceral endoderm cell lines derived from in vivo 11-day blastocysts

Two porcine cell lines of yolk-sac visceral endoderm, designated as PE-1 and PE-2, were derived from in vivo 11-d porcine blastocysts that were either ovoid (PE-1) or at the early tubular stage of elongation (PE-2). Primary and secondary culture of the cell lines was done on STO feeder cells. The PE-1 and PE-2 cells morphologically resembled visceral endoderm previously cultured from in vivo-derived ovine and equine blastocysts and from in vitro-derived bovine blastocysts. Analysis of the PE-1- and PE-2-conditioned medium by 2D-gel electrophoresis and matrix-assisted laser desorption/ionization-time-of-flight-mass spectrometry demonstrated that they produced serum proteins. Reverse transcriptase polymerase chain reaction analysis showed that the cells expressed several genes typical for yolk-sac endoderm differentiation and function including GATA-6, DAB-2, REX-1, HNF-1, transthyretin, alpha-fetoprotein, and albumin. Unlike a porcine liver cell line, the PE-1 and PE-2 cell lines had relatively low inducible P-450 content and EROD activity, and, while they cleared ammonia from the cell culture medium, they did not produce urea. Transmission electron microscopy revealed that the cells were a polarized epithelium connected by complex junctions resembling tight junctions and by lateral desmosomes. Rough endoplasmic reticulum was prominent within the cells. Immunocytochemistry indicated that the PE-1 cells expressed cytokeratin 18 and had robust microtubule networks similar to those observed in in vivo porcine yolk-sac endoderm. Metaphase spreads prepared at passage 26 of the PE-1 cell line indicated a diploid porcine karyotype of 38 chromosomes. The cells have been grown for over 1 yr for multiple passages at 1:10 or 1:20 split ratios on STO feeder cells. The cell lines will be of interest as an in vitro model of the porcine preimplantation yolk-sac tissue.

The effectiveness of the stereomicroscopic evaluation of embryo quality in vitrified-warmed porcine blastocysts: an ultrastructural and cell death study

The objective of this study was to analyze the validity of the stereomicroscopic evaluation of vitrified-warmed (V-W) porcine blastocysts. Unhatched blastocysts were obtained from Large-white gilts (n=10). Blastocysts (n=156) were vitrified using the Open Pulled Straw technology. After warming, V-W blastocysts were cultured for 24h (V24). Then, their developmental progression was morphologically assessed by stereomicroscopy and classified as: V24 viable re-expanded blastocysts; V24 viable hatched blastocysts or V24 degenerated. Blastocysts which re-expanded or hatched after warming were considered viable. Some fresh blastocysts were not vitrified and were evaluated after 24h in culture (F24). By stereomicroscopic analysis all the fresh blastocysts were considered viable. Some F24, V24 re-expanded viable, V24 hatched viable and V24 degenerated blastocysts were processed for transmission electron microscopy (n=13, 19, 9 and 9, respectively) or assessed by TUNEL for cell-death evaluation (n=16, 21, 11 and 21, respectively). All V24 hatched blastocysts showed similar ultrastructure to fresh blastocysts. However, some V24 re-expanded blastocysts considered viable (6/19) revealed ultrastructural alterations. Degenerated V24 blastocysts showed ultrastructural disintegration. Hatched V24 blastocysts did not differ (p>0.05) from F24 hatched blastocysts with regard to the ratio of dead cells (2.8+/-0.5% versus 1.9+/-0.3%, respectively). However, V24 expanded blastocysts had higher (p<0.01) cell death levels (4.3+/-3.4%) than those observed in the F24 expanded blastocysts (1.1+/-0.3%). The degenerated blastocysts showed the highest cell-death index (19.4+/-6.3%). In summary, V-W blastocyst hatching during in vitro culture appears to coincide with good ultrastructure and low cell-death index, suggesting that the hatching rate assessed by stereomicroscopy is more appropriate than embryo re-expansion for an evaluation of V-W blastocyst quality.

Differential but beneficial effect of phytohemagglutinin on efficiency of in vitro porcine embryo production by somatic cell nuclear transfer or in vitro fertilization

In vitro production of porcine embryos has become routine in most laboratories but the yield and quality of the resultant blastocysts remains sub-optimal. Phytohemagglutinin (PHA) is an N-acetylgalactosamine/galactose sugar-specific lectin with a wide variety of biological activities including mitogenesis, mediation of cell recognition and agglutination of cells. This study was therefore, designed to investigate the effect of PHA on the preimplantation development and quality of parthenogenetic, somatic cell nuclear transferred (SCNT) and in vitro fertilized (IVF) porcine embryos cultured in the absence or presence of PHA. Analysis showed that, supplementation of PHA significantly improved the blastocyst rate of parthenogenetic (70.6 +/- 0.2 vs. 51.4 +/- 0.6%) and SCNT (27.7 +/- 1.7 vs. 12.5 +/- 0.3%) embryos but not IVF embryos (25.0 +/- 14.3 vs. 20.1 +/- 12.7%). Nonetheless, PHA-treated blastocysts had higher hatching ability and contained higher cell number than control blastocysts in all the groups (P < 0.05). TUNEL labeling revealed that blastocysts cultured in the presence of PHA were less predisposed to biochemical apoptosis and showed lower indices of TUNEL, fragmentation and total apoptosis than those cultured in the absence of PHA (P < 0.05). Real time qRT-PCR analysis of parthenogenetic blastocysts revealed that PHA decreased the expression ratio of BAX:BCL-xL transcripts. Therefore, our study suggests that PHA improves the blastocyst yield and quality by enhancing blastocyst expansion, hatching and total cell number and decreasing the apoptosis. However, PHA has a differential effect on development rate of IVF derived embryos. These results may represent an approach towards achieving better preimplantation development of porcine embryos in vitro.

Full developmental potential of mammalian preimplantation embryos is maintained after imaging using a spinning-disk confocal microscope

Fluorescent live imaging of cells and embryos at subcellular resolution poses significant challenges for biologists due to morbidity and mortality ensuing from phototoxicity. Here we report the use of a spinning-disk confocal microscope to image mouse and bovine preimplantation embryos without impairing their developmental potential. We also present data indicating that this imaging technique does not affect the functionality of subcellular components as assessed by reactive oxygen species (ROS) production, caspase activity, and DNA integrity. Spinning-disk confocal microscopy was also useful in determining cell number and allocation in transgenic bovine blastocysts. We conclude that this imaging method is suitable for monitoring preimplantation embryos.

The axis of polarity of the mouse blastocyst is specified before blastulation and independently of the zona pellucida

BACKGROUND

Rather than being prepatterned, orientation of the embryonic-abembryonic (Em-Ab) axis of the mouse blastocyst has been claimed to depend on the conceptus being constrained by its zona pellucida (ZP) during blastulation. This hypothesis merited closer scrutiny, because it seemed at variance with observations on living conceptuses.

METHODS

Two-cell conceptuses with an oil drop injected into the lesser diameter (LD) of the ZP at the first cleavage plane were cultured until shortly before blastulation when the blastomere underlying the drop was labelled with carbocyanine dye. After removing the ZP, conceptuses were re-cultured to the blastocyst stage for recording the position along the axis of the centres of the patches of labelled cells.

RESULTS

These centres showed significant bias towards the equatorial (Eq) region of the axis compared with those resulting from labelling a blastomere at random, even following softening of the ZP at the 2-cell stage. This was also true if conceptuses were denuded at the 2-cell stage and the blastomere underlying an intact second polar body (PB) labelled in morulae.

CONCLUSIONS

These findings further support the view that the Em-Ab axis of the mouse blastocyst is normally prepatterned and provide no evidence of a role for the ZP in its specification.

Ultrastructure of preimplantation genetic diagnosis-derived human blastocysts grown in a coculture system after vitrification

OBJECTIVE

To evaluate ultrastructural features of preimplantation genetic diagnosis (PGD) blastocysts before and after vitrification.

DESIGN

Descriptive study of both vitrified and fresh hatching blastocysts.

SETTING

PGD program at the Instituto Universitario, Instituto Valenciano de Infertilidad.

PATIENT(S)

Patients undergoing PGD donated their abnormal embryos for research (n = 26).

INTERVENTION(S)

Biopsied embryos were cultured in the presence of human endometrial cells until day 6. Sixteen blastocysts were vitrified. A total of 11 high-scored hatching blastocysts, 6 warmed and 5 fresh, were fixed for ultrastructure.

MAIN OUTCOME MEASURE(S)

The cytoskeleton structure, type of intercellular junctions, and basic intracellular organelles in trophoectoderm cells and the inner cell mass were analyzed.

RESULT(S)

Ten of 16 blastocysts (62%) survived the warming process. Six of these showed no signs of cell degeneration and light microscopy revealed similar ultrastructural characteristics to those of controls. However, in trophoectoderm cells from both fresh and cryopreserved blastocysts, a reduced number of tight junctions and the presence of degradation bodies were detected.

CONCLUSION(S)

The particular ultrastructural features observed in PGD-derived blastocysts could be related to embryo manipulation and culture conditions. Vitrification does not seem to alter blastocysts, as those that survive hatching do not display detectable cellular alterations when observed through electron microscopy.

Marsupial Hypoblast: Formation and Differentiation of the Bilaminar Blastocyst in Sminthopsis macroura

Hypoblast formation in Sminthopsis macroura starts in blastocysts with a size between 1.0 and 1.4 mm, in which cells appear to be similar to each other, and finishes at the complete 2.6- or 2.7-mm bilaminar blastocyst, which is fully lined with hypoblast cells. When hypoblast cells begin allocation, the pluriblast region progressively differentiates from the trophoblast. Some pluriblast cells, which are otherwise undistinguished, lying on one side near the boundary of the circular pluriblast, move to the inside as hypoblast cells by mitosis or migration. They initially line the pluriblast and then the trophoblast. Hypoblast cells continue to leave the pluriblast/epiblast and intercalate into the underlying hypoblast layer until the advanced stages of bilaminar blastocysts. Associated with the origin of the hypoblast cells, the residual surface epiblast cells become less flatted and more cuboidal or rounded in shape. Characteristics are increased density of ribosomes, granular endoplasmic reticulum and a marked apical-basal polarity related to apical microvilli and endocytosis and more vesicles with flocculent content and a loss of the crystalloid deposits that were typical for earlier stages. Trophoblast cells become flat and elongated with only few vesicles, and they transform into extra-embryonic ectoderm cells, which are broader, rather square and with a higher density of ribosomes. Hypoblast cells are characterized by a relatively high level of ribosomes and endoplasmic reticulum, fewer small vesicles and no noticeable endocytotic processes and initially form a reticulum because the cells preferentially migrate along cell-cell boundaries by extension of long filopodia. Once hypoblast cells reach the boundary of the embryonic area and extend to line the trophoblast, they progressively consolidate into a squamous epithelium. It is suggested that the origin of the hypoblast from one side of the pluriblast and its invasion under the trophoblast from proliferating centres at the edge of the embryonic area provide mechanisms for patterning epiblast, hypoblast, trophoblast and extra-embryonic ectoderm.

Mitochondrial activity, distribution and segregation in bovine oocytes and in embryos produced in vitro

Contents Bovine oocytes and embryos produced in vitro were studied to determine the mitochondrial pattern of distribution, segregation and activity using DIOC 6 and Jc-1 fluorescence. The highest fluorescence level observed in mature oocytes was taken as 100% activity and six activity levels were estimated as follows: (1) 0%, (2) 1-15%, (3) 16-30%, (4) 31-50%, (5) 51-75% and (6) 76-100%. Three patterns of mitochondrial distribution were found: (1) diffused throughout the cytoplasm in oocytes and embryos, (2) pericytoplasmic in oocytes and embryos, and (3) perinuclear only in embryos. The segregation of mitochondria in blastomeres showed two distinct patterns: (1) symmetrical with an even mitochondrial population, and (2) asymmetrical with different numbers of mitochondria in each blastomere. In immature oocytes, mitochondrial activity was very low and the distribution was diffuse or negligible, while in mature oocytes the activity was high and the distribution was diffuse or pericytoplasmic. Competent embryos up to the 16-cell stage showed intermediate levels of activity (16-50%) but activity decreased thereafter up to the blastocyst stage. Non-competent embryos showed low levels of activity (1-15%) at all stages. These results suggest that mitochondria might play an important role during early development and that a minimum threshold of activity regulates the potential competence for reaching the blastocyst stage.

Tetraploid embryonic stem cells contribute to the inner cell mass of mouse blastocysts

The demonstration that mouse somatic cells can be reprogrammed following fusion with embryonic stem (ES) cells may provide an alternative to somatic cell nuclear transfer (therapeutic cloning) to generate autologous stem cells. In an attempt to produce cells with an increased pool of reprogramming factors, tetraploid ES cells were produced by polyethylene glycol mediated fusion of two ES cell lines transfected with plasmids carrying puromycin or neomycin resistance cassettes, respectively, followed by double antibiotic selection. Tetraploid ES cells retain properties characteristic of diploid ES cells, including the expression of pluripotent gene markers Oct4 and Rex1. On injection into the testis capsule of severe combined immunodeficient (SCID) mice, tetraploid ES cells are able to form teratomas containing cells representative of all three germ layers. Further, these cells demonstrated the ability to integrate into the inner cell mass of blastocysts. This study indicates that tetraploid ES cells are promising candidates as cytoplasm donors for reprogramming studies.

Nuclear and cytoplasmic localization of interferon-tau in in vitro-produced bovine blastocysts

Experiments were conducted to detect interferon-tau in bovine in vitro-derived blastocysts by transmission electron (TEM) and confocal microscopy. TEM showed the presence of IFN-tau in the cytoplasm and the nuclei of expanded blastocysts. Confocal microscopy similarly confirmed the presence of IFN-tau in the trophectoderm of blastocysts. The distribution of IFN-tau appeared variable with some cells showing strong labeling while others appeared to be devoid of the protein.

Randomized comparison of two different blastocyst grading systems

A more detailed blastocyst grading system provides a better selection of blastocysts with the highest implantation potential. Grading systems will help to decrease the number of blastocysts to be transferred without compromising high implantation and pregnancy rates.