The influence of early cleavage on embryo developmental potential and IVF/ICSI outcome

Comparative developmental competence of in vitro embryos recovered from Bali cattle with normal and poor sperm motility

Background and Aim

Fertility is crucial for enhancing the efficiency of livestock production, as it directly impacts the reproductive rates. A comprehensive understanding of the relationship between sperm quality and embryo development is key to optimizing reproductive outcomes and improving the quality of livestock. This study analyzed the developmental competence of in vitro embryos recovered from Bali cattle with normal or poor sperm motility.

Materials and Methods

Nine bulls with normal fresh semen (NFS) or poor fresh semen (PFS) motility were ejaculated for semen. Semen ejaculates, including volume, motility, and sperm concentration, were evaluated immediately after collection to measure the quality of the fresh semen. Frozen semen was evaluated using computer-assisted semen analysis (CASA) for motility, progressive sperm motility, distance curve path, distance curve linear, distance straight line, average path velocity, curvilinear velocity, linear velocity, straightness (STR), linearity of forward progression (LIN), wobble, and average lateral head displacement (ALH). Bull groups were used to determine in vitro embryo cleavage ability after fertilization of Bali cattle. Ovaries of Bali cattle were collected by slicing, and only cytoplasmic oocytes with compact cumulus cells were used in this study. The oocytes were matured, and in vitro fertilization was performed using fertilization media with a final sperm concentration of 1.5 × 106 spermatozoa/mL. After 48 h, the embryo cleavage ability of the cultured oocytes was evaluated.

Results

There were significant differences in motility values between the NFS and PFS groups; however, there were no significant differences in the volume or sperm concentration. There was a significant difference in the LIN value between the groups but no significant differences in other CASA parameters. There were no significant differences in the cleavage rate and morula between the groups, but a positive correlation was observed between the cleavage rate and the morula and between the morula and ALH. A significant negative correlation was observed between the cleavage rate and STR and between the morula and STR; no significant differences were observed for other variables.

Conclusion

Despite variations in sperm characteristics, both normal and poor sperm motility demonstrated comparable in vitro embryonic development competence. These findings provide important insights into the fertility potential of Bali bulls, providing valuable information that can enhance selection strategies to improve the quality of livestock production.

Does cleavage stage morphology increase the discriminatory power of prediction in blastocyst transfer outcome?

PURPOSE

To evaluate the contribution of the cleavage stage morphological parameters to the prediction of blastocyst transfer outcomes.

METHODS

A retrospective study was conducted on 8383 single-blastocyst transfer cycles including 2246 fresh and 6137 vitrified-warmed cycles. XGboost, LASSO, and GLM algorithms were employed to establish models for assessing the predictive value of the cleavage stage morphological parameters in transfer outcomes. Four models were developed using each algorithm: all-in model with or without day 3 morphology and embryo quality-only model with or without day 3 morphology.

RESULTS

The live birth rate was 48.04% in the overall cohort. The AUCs of the models with the algorithm of XGboost were 0.83, 0.82, 0.63, and 0.60; with LASSO were 0.66, 0.66, 0.61, and 0.60; and with GLM were 0.66, 0.66, 0.61, and 0.60 respectively. In models 1 and 2, female age, basal FSH, peak E2, endometrial thickness, and female BMI were the top five critical features for predicting live birth; In models 3 and 4, the most crucial factor was blastocyst formation on D5 rather than D6. In model 3, incorporating cleavage stage morphology, including early cleavage, D3 cell number, and fragmentation, was significantly associated with successful live birth. Additionally, the live birth rates for blastocysts derived from on-time, slow, and fast D3 embryos were 49.7%, 39.5%, and 52%, respectively.

CONCLUSIONS

The value of cleavage stage morphological parameters in predicting the live birth outcome of single blastocyst transfer is limited.

Paternal effect does not affect in vitro embryo morphokinetics but modulates molecular profile

The use of different sires influences in vitro embryo production (IVP) outcome. Paternal effects are observed from the first cleavages until after embryonic genome activation (EGA). Little is known about the mechanisms that promote in vitro fertility differences, even less about the consequences on embryo development. Therefore, this study aimed to evaluate the paternal effect at fertilization, embryo developmental kinetics, gene expression and quality from high and low in vitro fertility bulls. A retrospective analysis for bull selection was performed using the In vitro Brazil company database from 2012 to 2015. The dataset was edited employing cleavage and blastocyst rates ranking a total of 140 bulls. Subsequently, the dataset was restricted by embryo development rate (blastocyst/cleaved rate) and ten bulls were selected as high (HF; n = 5) and low (LF; n = 5) in vitro fertility groups. IVP embryos derived from high and low fertility bulls were classified according to their stage of development (2 cells, 3-4 cells, 6 cells, 8-16 cells), at 24, 36, 48, 60, 72 hpi, respectively, to evaluate embryo kinetics. Pronuclei formation (24 hpi), cleavage rate (Day 3), development rate, and blastocyst morphology (Grade I and II - Day 7) were also assessed, as well as the abundance of 96 transcripts at 8-16 cell stage and blastocysts. There was no difference in early embryo kinetics (P > 0.05), and cleavage rate (HF = 86.7%; LF = 84.9%; P = 0.25). Nevertheless, the fertilization rate was higher on HF (72%) than LF (62%) and the polyspermy rate was lower on HF compared to LF (HF:16.2% LF:29.2%). As expected, blastocyst rate (HF = 29.4%; LF = 16.0%; P < 0.0001) and development rate (HF = 33.9% LF = 18.9%; P < 0.0001) were higher in HF than LF. At the 8-16 cell stage, 22 transcripts were differentially represented (P ≤ 0.05) between the two groups. Only PGK1 and TFAM levels were higher in HF while transcripts related to stress (6/22, ∼27%), cell proliferation (6/22, ∼27%), lipid metabolism genes (5/22, ∼23%), and other cellular functions (5/22, ∼23%) were higher on LF embryos. Blastocysts had 9 differentially represented transcripts (P ≤ 0.05); being only ACSL3 and ELOV1 higher in the HF group. Lipid metabolism genes (3/9, 33%) and other cellular functions (6/9, 67%) were higher in the LF group. In conclusion, the timing of the first cleavages is not affected by in vitro bull fertility. However, low in vitro fertility bulls presented higher polyspermy rates and produced 8-16 cells embryos with higher levels of transcripts related to apoptosis and cell damage pathways compared to high in vitro fertility ones. Evidence such as polyspermy and increase in apoptotic and oxidative stress genes at the EGA stage suggest that embryo development is impaired in the LF group leading to the reduction of blastocyst rate.

Alpha-lipoic acid improves the maturation and the developmental potential of goat oocytes in vitro

Oxidative stress inevitably occurs during oocyte maturation in vitro. α-lipoic acid (α-LA) has a strong antioxidant capacity, but the effect of α-LA on parthenogenetic activation of oocytes was rarely reported. This study aims to investigate the effect of supplementing α-LA to in vitro maturation medium on the subsequent developmental ability of goat parthenogenetic embryos during oocytes maturation. In the study, the goat cumulus-oocyte complex was divided into the experimental (with 25 μmol/L α-LA) and the control (without α-LA) groups. Oxidase expression was measured using RT-qPCR. After 18-22 hr of maturation, the oocytes were then parthenogenetic activated. The total antioxidant capacity of embryos was measured after 0, 24, 48, 72 and 96 hr of culture. Rates of oocyte maturation and the rates of development for parthenogenetic embryos in the α-LA group were significantly improved by 7.88% (p < .05) and 5.41% (p < .05) compared with those in the control group, respectively. After 24 hr, the difference in total antioxidant capacity was extremely significant in both groups. An evident decrease in the control group and a minor decrease in the α-LA group were observed (p < .01). The ratio of inner cell mass cells to the total cell number of blastocysts in the α-LA group increased compared with that in the control group (p < .05) on day 8. α-LA significantly promoted the expression of SOD and GPX4 of parthenogenetic blastocysts and maturated oocytes. α-LA (25 μmol/L) improved the maturation rate and the developmental competence of the parthenogenetic activation of oocytes, which might be mediated by maintaining the total antioxidant ability of oocytes during the culture period.

Morphokinetic parameters as auxiliary criteria for selection of blastocysts cultivated in a time-lapse monitoring system

Objective:

To describe embryonic profile up to blastocyst stage in a time-lapse system.

Methods:

A retrospective, longitudinal, analytical study of patients submitted to in vitro fertilization. The embryos were grouped according to the degree of expansion, internal cell mass and trophectoderm classification, the morphokinetic parameters were associated with the time periods stated in each evolution phase.

Results:

The appearance of a second polar corpuscle (CPap) occurred earlier in the embryos classified as excellent (2.99h; p<0.05), in relation to the embryos classified as good (3.40h), average (3.48h) and poor (3.55h). The embryos classified as excellent took less time for the pronuclei to disappear (PNbd) (21.80h; p<0.05), when compared to the good embryos (22.96h), the average (23.21h) and the poor (23.47h). As for the morphokinetic parameter, the end of the two-cell division (T2) occurred first in the excellent blastocysts (24.38h; p<0.05), when compared to the other groups: good (25.57h), average (25.53h) and poor (25.78h). With respect to synchronization with the division of three to four cells (S2), the poor embryos presented longer times for such division to occur (3.67h; p<0.05). When compared to the embryos from the groups excellent (1.97h), good (2.70h) and average (2.09h). At the time point of the blastocoel formation (TB), the excellent embryos (104.04h) did not differ from the good embryos (104.10h). However, when compared to average (107.27h) and poor (106.86h) embryos, there was statistical significance (p<0.05).

Conclusions:

Embryos of better quality had a shorter time in some morphokinetic parameters when compared to the other groups, thus increasing the possibilities to establish new parameters for the classification and selection of embryos.

Trophoblast attachment to the endometrial epithelium elicits compartment-specific transcriptional waves in an in-vitro model

RESEARCH QUESTION

Which are the early compartment-specific transcriptional responses of the trophoblast and the endometrial epithelium throughout early attachment during implantation?

DESIGN

An endometrial epithelium proxy (cell line Ishikawa) was co-cultured with spheroids of a green fluorescent protein (GFP) expressing trophoblast cell line (JEG-3). After 0, 8 and 24 h of co-culture, the compartments were sorted by fluorescence-activated cell sorting; GFP+ (trophoblast), GFP- (epithelium) and non-co-cultured control populations were analysed (in triplicate) by RNA-seq and gene set enrichment analysis (GSEA).

RESULTS

Trophoblast challenge induced a wave of transcriptional changes in the epithelium that resulted in 295 differentially regulated genes involving epithelial to mesenchymal transition (EMT), cell movement, apoptosis, hypoxia, inflammation, allograft rejection, myogenesis and cell signalling at 8 h. Interestingly, many of the enriched pathways were subsequently de-enriched by 24 h (i.e. EMT, cell movement, allograft rejection, myogenesis and cell signalling). In the trophoblast, the co-culture induced more transcriptional changes and regulation of a variety of pathways. A total of 1247 and 481 genes were differentially expressed after 8 h and from 8 to 24 h, respectively. Angiogenesis and hypoxia were over-represented at both stages, while EMT and cell signalling only were at 8 h; from 8 to 24 h, inflammation and oestrogen response were enriched, while proliferation was under-represented.

CONCLUSIONS

Successful attachment produced a series of dynamic changes in gene expression, characterized by an overall early and transient transcriptional up-regulation in the receptive epithelium, in contrast to a more dynamic transcriptional response in the trophoblast.

Decrease in bovine in vitro embryo production efficiency during winter season in a warm-summer Mediterranean climate

Retrospective analysis of monthly embryo production from December 2011 to May 2015 and its correlation with meteorological data in our geographic zone was made. We had observed that in certain time of the year, in vitro blastocyst production decreases. Accordingly, was examined the association between blastocyst production and climatological parameters. Cleavage rates correlate positively with blastocyst rates (p < .05). Significant differences in cleavage rates between autumn and summer (79.8%; 71.5%), and between winter and autumn (71.8%; 79.8%), were found. Blastocyst production had lower efficiency in June (9 ± 12%) and July (4.9 ± 5.7%), which coincides with winter season. In contrast, higher embryo production was obtained in February (22.2 ± 9.7%), March (22.9 ± 14%) and September (25.2 ± 6.6%), which coincides with autumn and spring season. Similarly, embryo production correlates with meteorological parameters: blastocyst production positively correlates with sunshine hours, maximum temperature and average temperature. Similarly, blastocyst production inversely correlates with total precipitation and days >1 mm precipitation (p < .05). There is a significant decrease in bovine in vitro embryo production efficiency during winter season in our warm-summer Mediterranean climate zone. It remains to be investigated the direct effect of environmental factors on oocyte quality and its impact on in vitro production efficiency.

Timing of The First Zygotic Cleavage Affects Post-Vitrification Viability of Murine Embryos Produced In Vivo

Background

Timing of the first zygotic cleavage is an accurate predictor of embryo quality. Embryos that cleaved early (EC) have been shown to exhibit higher develop- mental viability compared to those that cleaved at a later period (LC). However, the vi- ability of EC embryos in comparison to LC embryos after vitrification is unknown. The present study aims to investigate the post-vitrification developmental viability of murine EC versus LC embryos.

Materials and Methods

In this experimental study, female ICR mice (6-8 weeks old) were superovulated and cohabited with fertile males for 24 hours. Afterwards, their ovi- ducts were excised and embryos harvested. Embryos at the 2-cell stage were catego- rized as EC embryos, while zygotes with two pronuclei were categorized as LC embryos. Embryos were cultured in M16 medium supplemented with 3% bovine serum albumin (BSA) in a humidified 5% CO₂atmosphere. Control embryos were cultured until the blastocyst stage without vitrification. Experimental embryos at the 2-cell stage were vitri- fied for one hour using 40% v/v ethylene glycol, 18% w/v Ficoll-70 and 0.5 M sucrose as the cryoprotectant. We recorded the numbers of surviving embryos from the control and experimental groups and their development until the blastocyst stage. Results were analyzed using the chi-square test.

Results

A significantly higher proportion of EC embryos (96.7%) from the control group developed to the blastocyst stage compared with LC embryos (57.5%, P<0.0001). Similarly, in the experimental group, a significantly higher percentage of vitrified EC embryos (69.4%) reached the blastocyst stage compared to vitrified LC embryos (27.1%, P<0.0001).

Conclusion

Vitrified EC embryos are more vitrification tolerant than LC embryos. Prese- lection of EC embryos may be used as a tool for selection of embryos that exhibit higher developmental competence after vitrification.

Morphometric analysis and developmental comparison of embryos from carriers with balanced chromosomal rearrangements in preimplantation genetic diagnosis cycles

The morphological parameters of embryos from 22 carriers with balanced chromosomal rearrangements (CRs) were quantified and evaluated to determine their possible link to chromosomal composition. The morphometric characteristics of 168 embryos diagnosed by fluorescence in situ hybridisation were measured using an imaging tool and then analysed retrospectively. The mean zygotic diameter of normal-balanced embryos was significantly smaller compared with that of abnormal embryos (P=0.015). In addition, the reduction in total cytoplasmic volume for Day-3 embryos was significantly lower in normal or balanced embryos than in abnormal embryos (P=0.027). Moreover, the pronuclear volumes of embryos that failed to reach the blastocyst stage were significantly smaller compared with those of blastocysts (P=0.016). These findings indicate that morphometric characteristics are correlated with developmental outcomes as well as with chromosomal composition in embryos from balanced CR carriers. However, an effective indicator of developmental outcomes may not accurately reflect chromosomal composition. Combining morphometric and traditional qualitative assessment may increase the precision and standardisation of embryo evaluation as well as contributing to improved efficiency of preimplantation genetic diagnosis by selecting embryos with high developmental potential and preferentially testing embryos predicted to have a low risk of chromosomal imbalance.

Early cleavage of handmade cloned buffalo (Bubalus bubalis) embryos is an indicator of their developmental competence and quality

Following IVF, embryos which cleave early have been shown to have higher developmental competence and quality than those that cleave relatively later across many species. We investigated the effect of time of cleavage on the developmental competence, quality, epigenetic status and gene expression in buffalo embryos produced by handmade cloning (HMC). Following classification of embryos as early cleaving (EC) or late cleaving (LC) based on whether they had cleaved or not at 24 h post in vitro culture, 54% (164/303) were found to be EC and the rest to be LC. The blastocyst rate (58.1 ± 3.4 vs 36.9 ± 1.6%, p < 0.01) and the total cell number (285.5 ± 41.9 vs 141.4 ± 36.1, p < 0.05) were higher, whereas the apoptotic index (3.6 ± 0.6 vs 12.2 ± 1.7, p < 0.01) and the global level of H3K9ac and H3K27me3 were lower (p < 0.05) in the blastocysts produced from EC than in those produced from LC embryos. The relative transcript level of CASPASE3, CASPASE7, DNMT1, DNMT3a and CDX2 was higher (p < 0.05) and that of SOX2 was lower (p < 0.05) in blastocysts produced from LC than in those produced from EC embryos, whereas the expression level of CASPASE6, P53, P21, HDAC1, OCT4 and NANOG was not significantly different between the two groups. These results show that (i) following HMC, blastocysts produced from embryos that cleave early differ from those produced from late cleaving embryos in terms of epigenetic status and expression level of many important apoptosis-, pluripotency-, trophectoderm- and epigenetics-related genes, and (ii) EC embryos are superior to LC embryos in view of their higher developmental competence and quality.

[How can we nowadays select the best embryo to transfer?]

Multiple pregnancies stand as the most common adverse outcome of assisted reproduction technologies (ART) and the dangers associated with those pregnancies have been reduced by doing elective single embryo transfers (e-SET). Many studies have shown that e-SET is compatible with a continuously high pregnancy rate per embryo transfer. Yet, it still becomes necessary to improve the selection process in order to define the quality of individual embryos - so that the ones we choose for transfer are more likely to implant. First, analysis of embryo morphology has greatly helped in this identification and remains the most relevant criterion for choosing the embryo. The introduction of time-lapse imaging provides new criteria predictive of implantation potential, but the real contribution of this system - including the benefit/cost ratio - seems to be not yet properly established. In this context, extended culture until blastocyst stage is an essential practice but it appears wise to keep it for a population showing a good prognosis. Then, the failure of aneuploid embryos to implant properly led to achieve preimplantation genetic screening (PGS) in order to increase pregnancy and delivery rates after ART. However, PGS by fluorescence in situ hybridization (FISH) at day 3 is a useless process - and may even be harmful. Another solution involves using comparative genomic hybridisation (CGH) and moving to blastocyst biopsy. Finally, it is envisaged that morphology will also be significantly aided by non-invasive analysis of biomarkers in the culture media that give a better reflection of whole-embryo physiology and function.

Case report: the use of annexin V coupled with magnetic activated cell sorting in cryopreserved spermatozoa from a male cancer survivor: healthy twin newborns after two previous ICSI failures

PURPOSE

The aim of the study is to report successful outcome (live births) after sperm sorting with annexin V-MACS on cryopreserved spermatozoa with high level of sperm DNA fragmentation from a cancer patient survivor.

METHODS

Cryopreserved spermatozoa were sorted with annexin V-MACS prior to ICSI. Sperm DNA fragmentation was evaluated by SCSA(®) and TUNEL.

RESULTS

The couple had two previous IVF/ICSI cycles failures using sperm cryopreserved before cancer treatment. On third ICSI cycle attempt results were as follow: pre-annexin V-MACS sperm quality: 10 × 10(6)/ml, 3.3 % progressive motility, 1 % normal forms, TUNEL: 72.5 % positive cells, SCSA(®): 76.6 % DFI. Post-annexin V-MACS sperm quality: 2.8 × 10(6)/ml, 10 % progressive motility, TUNEL: 58.8 % positive cells. Eight metaphase II oocytes were collected, 4 fertilized, 2 embryos were transferred on day 3 and healthy twins were born (1 boy, 1 girl).

CONCLUSIONS

Annexin V-MACS technique could be a potential tool to improve sperm quality on cryopreserved spermatozoa of cancer patient and improve ICSI outcome.

Embryo developmental capability and pregnancy outcome are related to the mitochondrial DNA copy number and ooplasmic volume

PURPOSE

To investigate the correlation between the ooplasmic volume and the number of mitochondrial DNA (mtDNA) copies in embryos and how they may affect fecundity.

METHOD

Using real-time PCR, mtDNA quantification was analyzed in unfertilized oocytes and uncleaved embryos. The size of the ovum was also assessed by calculating the ooplasmic volume at the time of granulosa cell removal for IVF or ICSI. Quantification analysis of the mtDNA in blastomeres was performed by real-time PCR at the 7-8 cell stage of the cleaved embryos at 72 h after oocyte retrieval. We calculated the cytoplasmic volume of the blastomeres.

RESULT

Our studies showed a significantly lower mtDNA copy number in unfertilized oocytes and uncleaved embryos in women who were older than 40 years of age (p < 0.05). The larger ooplasmic volume was also associated with earlier and more rapid cleavage (p < 0.05). The ooplasmic volume was also significantly larger in the group achieving pregnancy. We found a significant positive correlation between blastomere volume and the number of mtDNA copies (r = 0.76, p < 0.01, from Pearson product-moment correlation coefficient).

CONCLUSIONS

We have shown that blastomere volume is directly proportional to the number of mtDNA copies. Therefore, larger cytoplasmic volume, with earlier cleavage speed, implies more mtDNA copies. Evaluation of mtDNA quantification and the measurement of ooplasmic and blastomere volume may be useful for selection of high quality embryo and pregnancy outcome.

Matrix metalloproteinases in serum and the follicular fluid of women treated by in vitro fertilization

PURPOSE

To assess levels of matrix metalloproteinases 2 and 9 (MMP-2 and MMP-9) in follicular fluids and sera of female patients undergoing in vitro fertilization (IVF) treatment, and discover the role of MMPs in IVF outcome prediction.

METHODS

Sera and follicular fluids were obtained from 58 female patients treated for infertility by IVF. Twenty-nine of them became pregnant after the embryo-transfer; another 29 were not successful in IVF and did not conceive. Forty female non-pregnant blood donors and 38 healthy pregnant patients in the first trimester after the physiological conception were examined as control groups. MMP-2 and MMP-9 were quantitively assessed using enzyme-linked immunosorbent assay.

RESULTS

IVF females successfully conceiving after the IVF have shown the highest MMP-9 concentrations in sera (833.5 {686.0;958.7} ng/mL) and follicular fluids (9.6 {6.0; 17.0} ng/mL) compared to all other examined cohorts. Different behavior of MMP-2 and MMP-9 during the artificial ovulation was confirmed, because only MMP-9 has shown a vast difference between serum and follicular concentrations.

CONCLUSIONS

MMP-9 could be a good predictor of the successful IVF outcome (pregnancy), which was proven for serum as well as follicular MMP-9 levels.