Embryo morphology and development are dependent on the chromosomal complement

Prediction of embryo euploidy and pregnancy outcome by blastocyst morphology and development speed for women receiving single embryo transfer

BACKGROUND

Selection of high-quality blastocysts is the most important factor determining the success of assisted reproductive technology. The objective of this study is to assess the values of blastocyst morphological quality and development speed for predicting euploidy and clinical pregnancy outcome.

METHODS

A total of 155 preimplantation genetic testing cycles including 959 blastocysts and 154 euploid blastocyst transfer cycles conducted between January 2018 and December 2019 were retrospectively analysed. The associations of blastocyst morphological quality and development speed (D) with chromosomal status, clinical pregnancy rate, early miscarriage rate, and ongoing pregnancy rate were evaluated by univariate and multivariate regression.

RESULTS

The euploidy rate of development speed D5 blastocysts was significantly greater than that of D6 blastocysts (61.4% vs. 38.1%, P < 0.001), and the euploid rate of morphologically high-grade blastocysts was significantly greater than that of non-high-grade blastocysts. Development speed D5 (OR = 1.6, 95% CI 1.2-2.2, P = 0.02) and high-grade morphology (OR = 2.1, 95% CI 1.5-2.9, P = 0.01) were independent predictors of euploidy. The ongoing pregnancy rate of D5 blastocysts was significantly higher than that of D6 blastocysts (62.3% vs. 43.8%, P = 0.04). Transfer of euploid blastocysts with high-grade morphology resulted in a greater ongoing pregnancy rate than transfer of non-high-grade euploid blastocysts (60.7% vs. 43.2%, P = 0.049). Alternatively, D6 development speed was an independent risk factor for early pregnancy loss after euploid blastocyst transfer. Multivariate regression analysis adjusting for confounding factors identified maternal age, blastocyst development speed, and blastocyst morphological grade as independent predictors of euploidy but not of clinical pregnancy.

CONCLUSION

The recommended sequence of embryo transfer based on the present study is D5 high-grade > D6 high-grade > D5 non-high-grade > D6 non-high-grade.

Effect of cytoplasmic fragmentation on embryo development, quality, and pregnancy outcome: a systematic review of the literature

The role of cytoplasmic fragmentation in human embryo development and reproductive potential is widely recognized, albeit without standard definition nor agreed upon implication. While fragmentation is best understood to be a natural process across species, the origin of fragmentation remains incompletely understood and likely multifactorial. Several factors including embryo culture condition, gamete quality, aneuploidy, and abnormal cytokinesis seem to have important role in the etiology of cytoplasmic fragmentation. Fragmentation reduces the volume of cytoplasm and depletes embryo of essential organelles and regulatory proteins, compromising the developmental potential of the embryo. While it has been shown that degree of fragmentation and embryo implantation potential are inversely proportional, the degree, pattern, and distribution of fragmentation as it relates to pregnancy outcome is debated in the literature. This review highlights some of the challenges in analysis of fragmentation, while revealing trends in our evolving knowledge of how fragmentation may relate to functional development of the human embryos, implantation, and pregnancy outcome.

The Association between Embryo Development and Chromosomal Results from PGT-A in Women of Advanced Age: A Prospective Cohort Study

Embryo morphology and morphokinetics have been studied for their association with euploid embryos. However, the results are controversial, especially in the advanced-aged women group, when the risk of aneuploidy increases significantly. This prospective cohort study evaluated the association between embryo development between day-3 cleavage and day-5 blastocyst stages and euploidy rates, determined using preimplantation genetic testing for aneuploidy (PGT-A). Embryos from women aged 35 years and above who underwent intracytoplasmic sperm injections and PGT-A were studied. Day-3 cleavage-stage embryos were evaluated for their cell number, and day-5 blastocyst-stage embryos were evaluated for their morphological grade. Embryo development from day 3 to day 5 was categorized as either good or poor development and evaluated for its association with the PGT-A results. We evaluated 325 embryos from 101 infertile couples. It was found that 55.17% of blastocysts with good development and 29.83% with poor development were euploid. A significant association was found between embryo development and euploidy rates in advanced-aged women (p < 0.001). Also, there were significantly higher rates of euploid embryos with good blastocyst morphological grades, especially blastocyst expansion grades and trophectoderm grades. In conclusion, embryo morphokinetics shows promising results in predicting euploidy in advanced female age.

The Effect of Wharton's Jelly-Derived Conditioned Medium on the In Vitro Maturation of Immature Oocytes, Embryo Development, and Genes Expression Involved in Apoptosis

Oocyte cytoplasmic maturation is a crucial process during in vitro maturation (IVM), and finding an appropriate IVM medium that promotes oocyte competence is very critical in assisted reproductive technology (ART). The aim of this study was to investigate the effects of umbilical cord Wharton's jelly (WJ-MSCs)-derived conditioned media on the maturation of immature oocytes and their developmental potential in humans after IVM, as well as apoptotic gene expression. A total of 392 germinal vesicle (GV) oocytes were collected from 207 women aged 25-35 years and divided into two IVM groups: (1) control group, which was cultured in CleavTM medium, and (2) experimental group, which was cultured in supernatants of umbilical cord Wharton's jelly as a conditioned medium (CM). First, WJ-MSCs were isolated, and their purity was analyzed. The immunophenotypes of WJ-MSCs were analyzed by flow cytometry. The quantitative expression of BCL2, BAX, and BAG1 in matured oocytes and embryos was evaluated through quantitative real-time polymerase chain reaction (qRT-PCR). Our findings showed that WJ-MSCs have a high proliferating capacity. The purity of the isolated cells was further validated by immunophenotyping, which revealed that their surface antigen expression had phenotypical properties similar to WJ-MSCs. When compared to CD34 and CD45 surface markers, the enlarged cells were positive for CD90, CD105, and CD44. There were significant differences in cytoplasmic maturation of oocytes and embryo quality between the two groups. The mRNA expression levels of BCL-2, BAG1, and BAX in matured oocytes and embryos were also significantly different between the two groups. Therefore, WJ-MSCs medium indicated potential efficacy in terms of ameliorating oocyte maturation and in promoting the development and genes expression of BAX, BCL-2, and BAG1.

OneGene PGT: comprehensive preimplantation genetic testing method utilizing next-generation sequencing

PURPOSE

Preimplantation genetic testing for monogenic disorders (PGT-M) allows early diagnosis in embryos conceived in vitro. PGT-M helps to prevent known genetic disorders in affected families and ensures that pathogenic variants in the male or female partner are not passed on to offspring. The trend in genetic testing of embryos is to provide a comprehensive platform that enables robust and reliable testing for the causal pathogenic variant(s), as well as chromosomal abnormalities that commonly occur in embryos. In this study, we describe PGT protocol that allows direct mutation testing, haplotyping, and aneuploidy screening.

METHODS

Described PGT protocol called OneGene PGT allows direct mutation testing, haplotyping, and aneuploidy screening using next-generation sequencing (NGS). Whole genome amplification product is combined with multiplex PCR used for SNP enrichment. Dedicated bioinformatic tool enables mapping, genotype calling, and haplotyping of informative SNP markers. A commercial software was used for aneuploidy calling.

RESULTS

OneGenePGT has been implemented for seven of the most common monogenic disorders, representing approximately 30% of all PGT-M indications at our IVF centre. The technique has been thoroughly validated, focusing on direct pathogenic variant testing, haplotype identification, and chromosome abnormality detection. Validation results show full concordance with Sanger sequencing and karyomapping, which were used as reference methods.

CONCLUSION

OneGene PGT is a comprehensive, robust, and cost-effective method that can be established for any gene of interest. The technique is particularly suitable for common monogenic diseases, which can be performed based on a universal laboratory protocol without the need for set-up or pre-testing.

Considerations for future modification of The Association for the Study of Reproductive Biology embryo grading system incorporating time-lapse observations

The Association for the Study of Reproductive Biology (ASEBIR) Interest Group in Embryology (in Spanish 'Grupo de Interés de Embriología') reviewed key morphokinetic parameters to assess the contribution of time-lapse technology (TLT) to the ASEBIR grading system. Embryo grading based on morphological characteristics is the most widely used method in human assisted reproduction laboratories. The introduction and implementation of TLT has provided a large amount of information that can be used as a complementary tool for morphological embryo evaluation and selection. As part of IVF treatments, embryologists grade embryos to decide which embryos to transfer or freeze. At the present, the embryo grading system developed by ASEBIR does not consider dynamic events observed through TLT. Laboratories that are using TLT consider those parameters as complementary data for embryo selection. The aim of this review was to evaluate review time-specific morphological changes during embryo development that are not included in the ASEBIR scoring system, and to consider them as candidates to add to the scoring system.

Equine in vitro produced blastocysts: relationship of embryo morphology, stage and speed of development to foaling rate

CONTEXT

Information on factors associated with developmental competence of equine in vitro -produced (IVP) blastocysts is lacking.

AIMS

To determine the relationships of stage, grade, day of development, and specific morphological parameters of equine IVP blastocysts, to pregnancy and foaling rates.

METHODS

Photomicrographs of 316 IVP embryos with known pregnancy outcomes were scrutinised individually by four observers. Inter-observer variation was assessed, and pregnancy outcome evaluated in relation to day of blastocyst development and assigned grade and stage. Individual component analysis was performed to determine the association of specific morphological parameters with foaling rate.

KEY RESULTS

Overall pregnancy rate was 76.9% and foaling rate was 56.3%. The day of embryo development did not affect pregnancy rate but significantly affected foaling rate. Embryo stage did not affect foaling rate. Embryo grade affected foaling rate only for Day-9 embryos. Some morphological features in the bovine grading system did not predict outcome in equine IVP embryos. Significant individual parameters differed between Stage 5 and Stage 6 equine blastocysts.

CONCLUSIONS

Day of blastocyst development is the major factor related to foaling rate for equine IVP embryos. Notably, there was no effect of embryo stage on foaling rate and no evidence that prolonging culture until embryos advance in stage increases foaling rate. The standard bovine grading system is not directly applicable to equine IVP embryos; equine-specific staging and grading systems are proposed.

IMPLICATIONS

This information will allow laboratories to identify embryos with the highest developmental competence. Use of the proposed systems will increase consistency in embryo assessment among laboratories.

Cleavage stage at compaction-a good predictor for IVF outcome

OBJECTIVE

To analyze whether cleavage stage at compaction, and not only kinetics, can serve as a reliable predictor for clinical outcome.

METHODS

A retrospective cohort study including 1194 embryos, classified by compaction initiation stage (Group 1: compaction at fewer than eight cells, Group 2: compaction at eight cells, Group 3: compaction at more than eight cells). Of these, 815 embryos were evaluated for morphokinetic preimplantation parameters, and 379 embryos were analyzed for clinical implantation following thawing and transfer of single blastocysts during the same period.

RESULTS

In total, 1194 embryos were analyzed. Embryos that underwent compaction from more than eight cells (Group 3) exhibited more synchronous cleavage compared with Groups 1 and 2 (at both S2 and S3; P < 0.001), and displayed a significantly lower fragmentation rate. The likelihood of obtaining top-quality blastocysts decreased by 73% and 44% when comparing Group 3 embryos with those of Groups 1 and 2, respectively, (P < 0.03). Clinical validation of the results shows that while compaction from fewer than eight cells barely produced blastocysts for transfer, compaction at eight or more cells is crucial for implantation and birth (birth rates 11.1% and 18.5% for Groups 2 and 3, respectively).

CONCLUSION

Cleavage stage at compaction has a direct effect on blastocyst quality and subsequent pregnancy, so can be included in newly developed deep learning models for embryo selection.

Morphological and morphokinetic associations with aneuploidy: a systematic review and meta-analysis

BACKGROUND

A time lapse system (TLS) is utilized in some fertility clinics with the aim of predicting embryo viability and chance of live birth during IVF. It has been hypothesized that aneuploid embryos display altered morphokinetics as a consequence of their abnormal chromosome complement. Since aneuploidy is one of the fundamental reasons for IVF failure and miscarriage, attention has focused on utilizing morphokinetics to develop models to non-invasively risk stratify embryos for ploidy status. This could avoid or reduce the costs associated with pre-implantation genetic testing for aneuploidy (PGT-A). Furthermore, TLS have provided an understanding of the true prevalence of other dysmorphisms. Hypothetically, the incorporation of morphological features into a model could act synergistically, improving a model's discriminative ability to predict ploidy status.

OBJECTIVE AND RATIONALE

The aim of this systematic review and meta-analysis was to investigate associations between ploidy status and morphokinetic or morphological features commonly denoted on a TLS. This will determine the feasibility of a prediction model for euploidy and summarize the most useful prognostic markers to be included in model development.

SEARCH METHODS

Five separate searches were conducted in Medline, Embase, PubMed and Cinahl from inception to 1 July 2021. Search terms and word variants included, among others, PGT-A, ploidy, morphokinetics and time lapse, and the latter were successively substituted for the following morphological parameters: fragmentation, multinucleation, abnormal cleavage and contraction. Studies were limited to human studies.

OUTCOMES

Overall, 58 studies were included incorporating over 40 000 embryos. All except one study had a moderate risk of bias in at least one domain when assessed by the quality in prognostic studies tool. Ten morphokinetic variables were significantly delayed in aneuploid embryos. When excluding studies using less reliable genetic technologies, the most notable variables were: time to eight cells (t8, 1.13 h, 95% CI: 0.21-2.05; three studies; n = 742; I2 = 0%), t9 (2.27 h, 95% CI: 0.5-4.03; two studies; n = 671; I2 = 33%), time to formation of a full blastocyst (tB, 1.99 h, 95% CI 0.15-3.81; four studies; n = 1640; I2 = 76%) and time to expanded blastocyst (tEB, 2.35 h, 95% CI: 0.06-4.63; four studies; n = 1640; I2 = 83%). There is potentially some prognostic potential in the degree of fragmentation, multinucleation persisting to the four-cell stage and frequency of embryo contractions. Reverse cleavage was associated with euploidy in this meta-analysis; however, this article argues that these are likely spurious results requiring further investigation. There was no association with direct unequal cleavage in an embryo that progressed to a blastocyst, or with multinucleation assessed on Day 2 or at the two-cell stage. However, owing to heterogeneous results and poor-quality evidence, associations between these morphological components needs to be investigated further before conclusions can be reliably drawn.

WIDER IMPLICATIONS

This first systematic review and meta-analysis of morphological and morphokinetic associations with ploidy status demonstrates the most useful morphokinetic variables, namely t8, t9 and tEB to be included in future model development. There is considerable variability within aneuploid and euploid embryos making definitively classifying them impossible; however, it is feasible that embryos could be prioritized for biopsy. Furthermore, these results support the mechanism by which algorithms for live birth may have predictive ability, suggesting aneuploidy causes delayed cytokinesis. We highlight significant heterogeneity in our results secondary to local conditions and diverse patient populations, therefore calling for future models to be robustly developed and tested in-house. If successful, such a model would constitute a meaningful breakthrough when accessing PGT-A is unsuitable for couples.

Increased blastomere number is associated with higher live birth rate in day 3 embryo transfer

Purpose

To study the relationship between blastomere number and pregnancy outcomes of day 3 embryo transfers.

Methods

This retrospective cohort study included 2237 fresh single day 3 embryo transfer cycles from October 2013 to November 2020. Patients were divided into six groups according to the blastomere number on day 3: ≤ 6-cell (n = 100), 7-cell (n = 207), 8-cell (n = 1522), 9-cell (n = 187), 10-cell (n = 91) and ≥ 11-cell (n = 130). Generalized estimating equation analysis based on multivariate logistic regression model was performed to adjust for potential confounders.

Results

The live birth rate (LBR) was 19.0%, 27.1%, 38.9%, 32.1%, 44.0% and 53.8% for the ≤ 6-cell, 7-cell, 8-cell, 9-cell, 10-cell and ≥ 11-cell groups, respectively (P < 0.001). Specifically, the ≤ 6-cell group was associated with reduced LBR compared with the 8-cell group (aOR 0.50, 95% CI 0.29–0.86; P = 0.013). Conversely, the odds of live birth were significantly increased in patients transferred with 10-cell embryos (aOR 1.62, 95% CI 1.03–2.53; P = 0.035) and ≥ 11-cell embryos (aOR 2.14, 95% CI 1.47–3.11; P < 0.001) when using the 8-cell embryo group as reference. Similar trends were also observed in the rates of positive hCG test and clinical pregnancy, while no significant differences were detected in miscarriage risk.

Conclusion

Increased blastomere number was associated with higher LBR in fresh single day 3 embryo transfer cycles. This finding questions the consensus on the reduced developmental potential of fast-cleaving embryos. Further large prospective studies are warranted for confirmation.

Protamines and DNA integrity as a biomarkers of sperm quality and assisted conception outcome

Present research aim was to identify functional tests in semen associated with DNA damage and chromatin maturity (protamination) which predict the outcome in assisted reproduction. Couples were grouped according to male partner semen parameters, into normozoospermia (NZs), severe male factor (SMF) and mild male factor (MMF). DNA fragmentation index (DFI) in spermatozoa was analysed by sperms chromatin dispersion (SCD), sperm chromatin structure assay (SCSA) and acridine orange testing (AOT). Chromomycin A3 (CMA3) and toluidine blue (TB) staining to measure sperm chromatin maturity (CM). DFI and chromatin decondensation were significantly lower in N compared to male factor categories (MMF and SMF). Aneuploidy embryos were significantly higher in couples with male factor infertility (MMF and SMF). A positive correlation was observed between fertilization rate (FR) and live birth rate (LBR) with sperm concentration, motility, vitality, normal sperm morphology and negative correlation between sperm DFI and sperm CM. No correlation was observed between embryo aneuploidy and sperm DFI or CM. Lower percentage of spermatozoa chromatin integrity are associated with low fertilization and live birth rate. Male factor infertility, due to impaired semen parameters and chromatin defects could be regarded in future as an indication of IVF/ICSI, and predictor of assisted reproductive techniques outcome.

Rate of Post-Fertilization Mitotic Activity Predicts Embryonic Competence via Next Generation Sequencing: An Analysis of 39,301 Cleavage Stage Embryos

Objective

To investigate the association between cleavage stage development, embryonic competence, and euploidy in patients undergoing in vitro fertilization (IVF) with subsequent next generation sequencing.

Methods

The retrospective cohort study included patients at an academic fertility center who underwent IVF with at least one cleavage stage embryo from 2016 to 2019. Embryos were analyzed as slow (<6 cells), intermediate (6-8 cells), or fast (>8 cells); day 3 cell count was also analyzed as a continuous variable. Primary outcomes were blastulation rate, biopsied blastocyst rate, and euploid rate. Odds of blastulation, biopsy, and euploidy were also calculated. Additionally, we modeled the predicted probability of an embryo reaching blastulation, biopsy, and euploidy based on cleavage stage development.

Results

When compared with intermediate and slow cohorts, fast cleaving embryos had significantly higher rates of blastulation (82.70% vs. 75.13 vs. 42.48%), biopsy (55.04% vs. 44.00% vs. 14.98%), and euploidy (50.65% vs. 47.93% vs. 48.05%). After adjustment for covariates, there was a significant association between cleavage stage development and odds of blastulation (OR 1.38, 95% CI 1.29-1.48), biopsy (OR 1.42, 95% CI 1.34-1.51), and euploidy (OR 1.08, 95% CI 1.01-1.17). Finally, we observed significant associations between cleavage stage development and predicted probability of reaching blastulation (OR 1.29, 95% CI 1.27-1.32), biopsy (OR 1.24, 95% CI 1.22-1.26), and euploidy (OR 1.02, 95% CI 1.01-1.04).

Conclusions

Cleavage stage embryos with greater mitotic activity perform as well as or better than intermediate or slower cleaving embryos. Rapidly cleaving embryos have high rates of euploidy and significant clinical potential.

Molecular Drivers of Developmental Arrest in the Human Preimplantation Embryo: A Systematic Review and Critical Analysis Leading to Mapping Future Research

Developmental arrest of the preimplantation embryo is a multifactorial condition, characterized by lack of cellular division for at least 24 hours, hindering the in vitro fertilization cycle outcome. This systematic review aims to present the molecular drivers of developmental arrest, focusing on embryonic and parental factors. A systematic search in PubMed/Medline, Embase and Cochrane-Central-Database was performed in January 2021. A total of 76 studies were included. The identified embryonic factors associated with arrest included gene variations, mitochondrial DNA copy number, methylation patterns, chromosomal abnormalities, metabolic profile and morphological features. Parental factors included, gene variation, protein expression levels and infertility etiology. A valuable conclusion emerging through critical analysis indicated that genetic origins of developmental arrest analyzed from the perspective of parental infertility etiology and the embryo itself, share common ground. This is a unique and long-overdue contribution to literature that for the first time presents an all-inclusive methodological report on the molecular drivers leading to preimplantation embryos’ arrested development. The variety and heterogeneity of developmental arrest drivers, along with their inevitable intertwining relationships does not allow for prioritization on the factors playing a more definitive role in arrested development. This systematic review provides the basis for further research in the field.

Development and frozen-thawed transfer of non-pronuclear zygotes-derived embryos in IVF cycles

OBJECTIVE

To explore the development and pregnancy potential of non-pronuclear (0PN) zygote-derived embryos in conventional in vitro fertilization (IVF) cycles.

STUDY DESIGN

Embryonic development in 1039 oocyte retrieval cycles and clinical outcomes of 659 frozen-thawed blastocyst transfer cycles were retrospectively studied.

RESULTS

Developmental potential of embryos with different blastomere numbers on day 3 were inconsistent in 0PN and 2PN groups. For 0PN-derived embryos, blastocyst rate of fast developing embryos (75.4%) was similar to that of intermediately developing embryos (72.9%), but good quality blastocyst rate of the former (49.2%) was significantly higher than that of the later (39.6%). In 2PN group, intermediately developing embryos had the highest blastocyst rate (77.9%) and good quality blastocyst rate (51.5%) (statistically significant). Comparison of frozen-thawed transfer was carried out between 0PN- and 2PN-derived blastocysts. For both single (SBT) and double blastocyst transfer (DBT) groups, no statistical differences existed between 0PN- and 2PN-derived blastocysts in clinical pregnancy rates (45.2% and 49.1% in SBT group, 64.7% and 66.4% in DBT group), implantation rates (45.2% and 49.1% in SBT group, 41.2% and 47.7% in DBT group) and live birth rates (35.5% and 36.8% in SBT group, 52.9% and 51.2% in DBT group).

CONCLUSION

The developmental characteristic of 0PN-derived embryos was different from that of 2PN-derived embryos in IVF cycles. 0PN-derived blastocysts could obtain acceptable clinical pregnancy and live birth, but more studies are needed to confirm the safety..

Nicotinamide Supplementation Improves Oocyte Quality and Offspring Development by Modulating Mitochondrial Function in an Aged Caenorhabditis elegans Model

Aging is associated with a decline in the quality of biological functions. Among the aging processes, reproductive aging is a critical process because of its intergenerational effects. However, the mechanisms underlying reproductive aging remain largely unknown. Female reproductive aging is the primary reason for limited fertility in mammals. Therefore, we attempted to investigate a modulator that can control female reproductive aging using a Caenorhabditis elegans model. In the present study, we examined the role of nicotinamide (NAM) in oocyte quality and offspring development. The levels of reactive oxygen species (ROS) and oxidative stress responses in aged oocytes, embryonic lethality, and developmental growth of the offspring were examined with maternal NAM supplementation. Supplementation with NAM improved oocyte quality, decreased embryonic lethality, and promoted germ cell apoptosis. Furthermore, NAM supplementation in aged mothers reduced ROS accumulation and improved mitochondrial function in oocytes. Consequently, the developmental growth and motility of offspring were improved. These findings suggest that NAM supplementation improves the health of the offspring produced by aged mothers through improved mitochondrial function. Taken together, our results imply that NAM supplementation in the aged mother improves oocyte quality and protects offspring by modulating mitochondrial function.

Clinical application of sequencing-based methods for parallel preimplantation genetic testing for mitochondrial DNA disease and aneuploidy

OBJECTIVE

To validate and apply a strategy permitting parallel preimplantation genetic testing (PGT) for mitochondrial DNA (mtDNA) disease and aneuploidy (PGT-A).

DESIGN

Preclinical test validation and case reports.

SETTING

Fertility centers. Diagnostics laboratory.

PATIENTS

Four patients at risk of transmitting mtDNA disease caused by m.8993T>G (Patients A and B), m.10191T>G (Patient C), and m.3243A>G (Patient D). Patients A, B, and C had affected children. Patients A and D displayed somatic heteroplasmy for mtDNA mutations.

INTERVENTIONS

Embryo biopsy, genetic testing, and uterine transfer of embryos predicted to be euploid and mutation-free.

MAIN OUTCOME MEASURES

Test accuracy, treatment outcomes, and mutation segregation.

RESULTS

Accuracy of mtDNA mutation quantification was confirmed. The test was compatible with PGT-A, and half of the embryos tested were shown to be aneuploid (16/33). Mutations were detected in approximately 40% of embryo biopsies from Patients A and D (10/24) but in none from Patients B and C (n = 29). Patients B and C had healthy children following PGT and natural conception, respectively. The m.8993T>G mutation displayed skewed segregation, whereas m.3243A>G mutation levels were relatively low and potentially impacted embryo development.

CONCLUSIONS

Considering the high aneuploidy rate, strategies providing a combination of PGT for mtDNA disease and aneuploidy may be advantageous compared with approaches that consider only mtDNA. Heteroplasmic women had a higher incidence of affected embryos than those with undetectable somatic mutant mtDNA but were still able to produce mutation-free embryos. While not conclusive, the results are consistent with the existence of mutation-specific segregation mechanisms occurring during oogenesis and possibly embryogenesis.

Competence of embryos showing transient developmental arrest during in vitro culture

PURPOSE

In vitro developing embryos may apparently show no developmental progress during 24 h and resume their development up to the blastocyst stage. The present study was conducted to assess their ability to implant and to give rise to a live birth when replaced at day 5 (fresh or vitrified/warmed) as compared to continuously developing embryos.

METHODS

Embryo development follow-up and grade were prospectively recorded in a photo database. The studied period was from April 2011 to July 2017. The studied embryos included transient arrested embryos (TAE) that showed the same developmental stage at two subsequent observations, i.e. between day 2 and day 3 (d2 and d3), between day 3 and day 4 (d3 and d4) and between day 4 and day 5 (d4 and d5). TAE were compared to continuously developing embryos (CDE). Elective day 5 embryo transfers were performed.

RESULTS

Woman age was higher in TAE (34.3±3.9) than in CDE (32.9±4.8) (p<0.01). TAE were more frequently (63.1%) observed after ICSI than after conventional IVF (55.9%) (p<0.01). Implantation rate was reduced in TAE as compared to CDE, after both fresh (10.0% vs 23.8% [p<0.01]) and vitrified/warmed (12.9% vs 19.0% [p<0.01]) embryo transfers. Delivery rate was also lower after the transfer of fresh (8.3% vs 19.4% [p<0.01]) and vitrified/warmed (8.5% vs 14.1% [p<0.01]) TAE as compared to CDE. Implantation and delivery rates were not statistically different whether embryo arrested between day 2 and day 3 (d2 and d3), between day 3 and day 4 (d3 and d4) or between day 4 and day 5 (d4 and d5).

CONCLUSION

TAE may be considered for transfer at a lower priority than CDE and associated with inferior prognosis than CDE.

Day 3 time lapse selection is beneficial for the patients with no good-quality embryos

We aimed to evaluate whether or not time lapse selection was beneficial for the cleavage-stage embryo transfers. The study included 838 infertile women with good ovarian reserve (obtaining more than 8 oocytes) from January 2018 to August 2019. Based on the transferred embryos with different grades (grade I, II and III), the patients were divided into day 3 selection with conventional morphology (CM) and day 3 selection with time lapse (TL) groups. For the grade I and II embryos, we observed that CM and TL had similar implantation, clinical pregnancy and ongoing pregnancy (p > .05) rates. For the grade III embryos, we observed that CM group showed slightly lower implantation (36.74 versus 41.03%, p = .261) and clinical pregnancy (56.82 versus 64.10%, p = .182) rates than TL group. CM group showed significantly lower ongoing pregnancy (47.35 versus 59.83%, p = .025) rate than TL group. And we observed that CM group had significantly higher blastulation (38.93 versus 26.61%, p = .019) rate than TL group. We concluded that TL selection was beneficial to the patients with no good-quality embryos in the first cleavage-stage embryo transfers.

Analysis of bovine blastocysts indicates ovarian stimulation does not induce chromosome errors, nor discordance between inner-cell mass and trophectoderm lineages

Contemporary systems for oocyte retrieval and culture of both cattle and human embryos are suboptimal with respect to pregnancy outcomes following transfer. In humans, chromosome abnormalities are the leading cause of early pregnancy loss in assisted reproduction. Consequently, pre-implantation genetic testing for aneuploidy (PGT-A) is widespread and there is considerable interest in its application to identify suitable cattle IVP embryos for transfer. Here we report on the nature and extent of chromosomal abnormalities following transvaginal follicular aspiration (OPU) and IVP in cattle. Nine sexually mature Holstein heifers underwent nine sequential cycles of OPU-IVP (six non-stimulated and three stimulated cycles), generating 459 blastocysts from 783 oocytes. We adopted a SNP-array approach normally employed in genomic evaluations but reanalysed (Turner et al., 2019; Theriogenology125: 249) to detect levels of meiotic aneuploidy. Specifically, we asked whether ovarian stimulation increased the level of aneuploidy in either trophectoderm (TE) or inner-cell mass (ICM) lineages of blastocysts generated from OPU-IVP cycles. The proportion of Day 8 blastocysts of inseminated was greater (P < 0.001) for stimulated than non-stimulated cycles (0.712 ± 0.0288 vs. 0.466 ± 0.0360), but the overall proportion aneuploidy was similar for both groups (0.241 ± 0.0231). Most abnormalities consisted of meiotic trisomies. Twenty in vivo derived blastocysts recovered from the same donors were all euploid, thus indicating that 24 h of maturation is primarily responsible for aneuploidy induction. Chromosomal errors in OPU-IVP blastocysts decreased (P < 0.001) proportionately as stage/grade improved (from 0.373 for expanded Grade 2 to 0.128 for hatching Grade 1 blastocysts). Importantly, there was a high degree of concordance in the incidence of aneuploidy between TE and ICM lineages. Proportionately, 0.94 were "perfectly concordant" (i.e. identical result in both); 0.01 were imperfectly concordant (differing abnormalities detected); 0.05 were discordant; of which 0.03 detected a potentially lethal TE abnormality (false positives), leaving only 0.02 false negatives. These data support the use of TE biopsies for PGT-A in embryos undergoing genomic evaluation in cattle breeding. Finally, we report chromosome-specific errors and a high degree of variability in the incidence of aneuploidy between donors, suggesting a genetic contribution that merits further investigation.

Timing of cleavage divisions determined with time-lapse imaging is linked to blastocyst formation rates and quality of in vitro-produced ovine embryos

Time-lapse (TL) imaging provides a practical and safe tool to constantly monitor the development of in vitro-derived embryos. TL may help develop novel methods of predicting the timing of embryo cleavage that will lead to optimizing blastocyst cryopreservation or transfer. The primary objective of the present study was to employ TL imaging to examine associations among the division kinetics of ovine embryos, their quality and rates of development to the blastocyst stage. Oocytes were collected by ovary scarification from 78 Longwool ewes slaughtered in the breeding season (November-March). Cumulus oocyte complexes (COCs) were matured for 24 h in TCM 199 media containing 0.1 IU/mL LH/FSH and 10% FBS. In-vitro fertilization was carried out by co-incubation of semen and COCs for 19 h. Presumptive zygotes were placed in microwells, in droplets of Cult medium (Gynemed, Lensahn, Germany). Digital images of developing embryos were captured every 10 min by Primo Vision TL system (EVO+; Vitrolife, Göteburg, Sweden). The following time intervals were recorded: from IVF to the attainment of two-cell (t2), three-cells (t3) or four-cell (t4) stage, to morula detection (tM), blastulation (tSB) and blastocyst formation (tB). Lastly, the duration of the second cell cycle (cc2; t3-t2) and complete synchronous cell division (s2; t4-t3) were calculated, and the incidence of developmental anomalies noted. Out of 147 embryos selected for TL observations, 55 (37.4%) developed to the blastocyst stage (normally developing embryos, NE) and 92 (62.6%) failed to reach the blastocyst stage (arrested embryos, AE; P < 0.05). Mean t2, tM, s2 and cc2 were all less (P ≤ 0.02) in NE compared with AE. Approximately 61.9% of embryos exhibited developmental anomalies (35.5% in the NE group and 78.2% in the AE group; P < 0.05) and AE exceeded (P < 0.05) NE in the proportion of FRG (blastomeric fragmentation), IRR (blastomeres of irregular size after cleavage), DC (direct cleavage) and MA (multi-morphological aberrations). Of all NE, 63.6% were classified as good quality and 36.4% as poor quality blastocysts (P < 0.05). Good quality ovine blastocysts attained t2, t3, t4, tSB and tB stages earlier (P ≤ 0.03) than poor quality blastocysts and none of the poor quality blastocysts was seen to hatch. To recapitulate, the present results indicate that the kinetics of early ovine embryo development are significant predictors of their potential to develop to the blastocyst stage and the markers of blastocyst quality. Time-lapse imaging may serve as a useful technique for predicting the outcome and enhancing efficacy of in vitro embryo production in sheep.

The hare and the tortoise: extreme mitotic rates and how these affect live birth

RESEARCH QUESTION

Is live birth of patients with excessive slow (no blastocyst on day 5) and fast mitotic rate (full blastocyst development on day 4) comparable to a matched control standard (blastocyst formation on day 5)?

DESIGN

In this retrospective matched (age and anti-Müllerian hormone [AMH]) case-control study rates of fertilization, blastulation, implantation, clinical pregnancy and live birth were compared in couples with male factor indication, prolonged embryo culture and fresh single morula and blastocyst transfer.

RESULTS

The rates of implantation, clinical pregnancy and live birth in the slow-developing group were significantly (P < 0.001) lower (17.6%, 13.7%, and 11.8%, respectively) compared with the fast (58.5%, 52.5%, 47.5%) and normal growing counterparts (51.5%, 42.6%, 39.6%). No differences in neonatal outcome could be observed between the three groups. Sex ratio in the fast-growing group was not different from the other cohorts.

CONCLUSIONS

Extremely slow development, as assessed by the absence of blastulation on day 5, is a negative predictor of pregnancy and live birth. In contrast, the fear that extremely fast-growing embryos may represent an aneuploid cohort of embryos is unsubstantiated. Day-4 full blastocysts can preferentially be considered for transfer.

Selection based on morphological features of porcine embryos produced by in vitro fertilization: Timing of early cleavages and the effect of polyspermy

The aim of this study was to examine whether a morphological approach is efficient for selecting high‐quality porcine embryos produced by in vitro fertilization (IVF) under high polyspermy conditions. Frozen‐thawed Meishan epididymal spermatozoa showing moderate and high polyspermy were subjected to IVF (1 × 10⁵ sperms/ml). Under conditions of moderate polyspermy, 4‐cell embryos selected at 48 hr after IVF (single selection) and 8‐cell embryos selected at 79 hr after IVF from the collected 4‐cell embryos (double selection) showed high developmental competence. Likewise, 4‐ and 8‐cell embryos produced by IVF under high polyspermy conditions also showed high competence for development to blastocysts. However, blastocysts derived from high polyspermy conditions had significantly fewer cells than those produced under moderate polyspermy conditions. Furthermore, the frequency of nuclear and chromosomal abnormalities in 4‐ and 8‐cell embryos produced under conditions of high polyspermy was significantly (p < .05) higher in comparison to moderate polyspermy conditions. These findings suggest that although high polyspermy affects the frequency of nuclear and chromosomal anomalies in porcine IVF embryos, subsequent selection based on morphological features of 4‐ and 8‐cell embryos even under high polyspermy conditions, could be an alternative option for selecting porcine IVF embryos with high development ability.

Are morphokinetic parameters of embryo development associated with adverse perinatal outcomes following fresh blastocyst transfer?

RESEARCH QUESTION

Are obstetric and perinatal complications associated with morphokinetic parameters of embryo development?

DESIGN

This proof-of-concept pilot study included a retrospective analysis of embryo morphokinetic parameters of 85 live births following day 5 single blastocyst transfer. Kinetic variables included time interval (hours) from time of pronuclei fading (tPNf) to: time of 2 cells (tPNf-t2), 9 cells (tPNf-t9), morula (tPNf-tM), start of blastulation (tPNf-tSB), full blastocyst (tPNf-tB) and expanded blastocyst (tPNf-tEB). Multivariable logistic models were used to calculate the risk of perinatal complications after adjustment for confounders.

RESULTS

The mean interval of tPNf-tSB was significantly longer for newborns with congenital anomalies compared with healthy newborns (79.49 ± 5.78 versus 71.7 ± 6.3, respectively, P = 0.01) and for embryos of women who had gestational diabetes mellitus compared with normoglycemic women (76.56 ± 7.55 versus 71.5 ± 6.13, respectively, P = 0.015). The mean interval of tPNf-t9 was significantly longer for low-birthweight newborns compared with normal weight (49.25 ± 5.54 versus 45.47 ± 4.77, respectively, P = 0.01). Preterm delivery was associated with several longer intervals of cell divisions compared with delivery at term (tPNf-t5: 28.76 ± 3.13 versus 26.64 ± 2.40, respectively, P = 0.01; tPNf-t6: 30.10 ± 3.05 versus 27.68 ± 2.30, respectively, P < 0.001; tPNf-t7: 32.08 ± 4.11 versus 28.70 ± 2.67, respectively, P < 0.001; tPNf-t8: 34.75 ± 4.95 versus 30.70 ± 4.10, respectively, P < 0.001; tPNf-t9: 50.23 ± 5.87 versus 45.44 ± 4.67, respectively, P < 0.001). For each of the outcomes, the association remained significant after adjusting for confounders.

CONCLUSION

This study indicates that there may be a possible association between adverse perinatal outcomes and morphokinetic parameters. Larger studies are needed to establish this association.

In vitro production of horse embryos predisposes to micronucleus formation, whereas time to blastocyst formation affects likelihood of pregnancy

Invitro embryo production is an increasingly popular means of breeding horses. However, success is limited by a high incidence of early embryo loss. Although there are various possible causes of pregnancy failure, chromosomal abnormalities, including aneuploidy, are important potential contributors. This study evaluated the frequency of micronucleus formation as a proxy for aneuploidy in invitro-produced (IVP) and invivo-derived horse blastocysts. Associations between IVP embryo morphology, frequency of nuclear abnormalities and the likelihood of pregnancy were investigated. IVP blastocysts exhibited a higher frequency of cells with micronuclei than invivo-derived embryos (10% vs 1% respectively; P=0.05). This indication of chromosomal instability may explain the higher incidence of pregnancy failure after transfer of IVP embryos. However, the frequency of micronuclei was not correlated with brightfield microscopic morphological characteristics. Nevertheless, IVP embryos reaching the blastocyst stage after Day 9 of invitro culture were less likely to yield a pregnancy than embryos that developed to blastocysts before Day 9 (27% vs 69%), and embryos that had expanded before transfer were more likely to undergo embryonic death than those that had not expanded (44% vs 10%). These findings indicate that current embryo culture conditions are suboptimal and that the speed of embryo development is correlated with pregnancy survival.

Morphology, developmental stages and quality parameters of in vitro-produced equine embryos

Intracytoplasmic sperm injection (ICSI) is used to produce equine embryos invitro. The speed of embryo development invitro is roughly equivalent to what has been described for embryos produced invivo. Morphological evaluations of ICSI-produced embryos are complicated by the presence of debris and the dark nature of equine embryo cytoplasm. Morulas and early blastocysts produced invitro appear similar to those produced invivo. However, with expansion of the blastocyst, distinct differences are observed compared with uterine embryos. In culture, embryos do not undergo full expansion and thinning of the zona pellucida (ZP) or capsule formation. Cells of the inner cell mass (ICM) are dispersed, in contrast with the differentiated trophoblast and ICM observed in embryos collected from uteri. As blastocysts expand invitro, embryo cells often escape the ZP as organised or disorganised extrusions of cells, probably through the hole incurred during ICSI. Quality assessment of invitro-produced early stage equine embryos is in its infancy, because limited information is available regarding the relationship between morphology and developmental competence. Early embryo development invivo is reviewed in this paper, with comparisons made to embryo development invitro and clinical assessments from a laboratory performing commercial ICSI for >15 years.

Strictly selected Mono- and non-pronuclear blastocysts could result in appreciable clinical outcomes in IVF cycles

The aim of the study was to examine the clinical value of blastocysts derived from mono-pronuclear (1PN) or non-pronuclear (0PN) zygotes with two polar bodies (2PB), which were selected by our criteria. We retrospectively analysed 610 frozen-thawed blastocyst transfer (FET) cycles and the corresponding oocyte retrieval cycles from 2014 to 2017. Developmental potential and clinical outcomes of embryos derived from zygotes with various numbers of pronuclei were analysed. Based on more detailed pre-selection settings, blastulation rates of 1PN/2PB and 0PN/2PB-derived embryos were 70.18% and 69.17%, respectively. Blastocyst FET results were not significantly different between 2PN/2PB, 1PN/2PB and 0PN/2PB groups in terms of clinical pregnancy rates (59.79%, 47.06% and 56.25%), implantation rates (47.24%, 40.00% and 47.62%), live birth rates (49.39%, 29.41% and 43.75%) or malformation rates (0%, 0% and 0%). In conclusion, after strict morphological selection and blastocyst culture, 1PN/2PB and 0PN/2PB-derived embryos in IVF cycles can have considerable clinical value. Blastocysts derived from 1PN/2PB or 0PN/2PB zygotes are worthwhile FET option for patients who have no available 2PN-derived embryos.

Association between mild stimulated IVF/M cycle and early embryo arrest in sub fertile women with/without PCOS

BACKGROUND

The in vitro maturation (IVM) technique has physical and financial benefits, but a lower efficiency and outcome that is still unclear whether it is related to polycystic ovary syndrome (PCOS) itself or the IVM procedure. In this study, we analyzed the clinical and laboratory outcomes of an optimized IVM protocol in patients with and without PCOS. We also discussed the possible reasons for early embryo arrest in the IVM cycle.

METHODS

This prospective study involved 58 PCOS patients and 56 non-PCOS patients who underwent mild stimulated IVF combined IVM (IVF/M) cycles. The clinical and laboratory outcomes were compared between the two groups. Also, metaphase II (MII) oocytes were obtained after IVM from the two groups, and in vivo MII oocytes randomly collected from IVF patients were examined for mitochondrial function using a laser scanning confocal microscope (LSCM). The aneuploidy rate for arrested cleavage embryos from IVM and IVF oocytes were screened using Next Generation Sequencing (NGS).

RESULTS

Mildly stimulated IVF/M resulted in cumulative clinical pregnancy and implantation rates (40.2, 28.7% in the PCOS group vs. 41.9, 36% in the non-PCOS group), respectively. The blastocyst formation rates were comparable (28% vs. 28.2%) in PCOS and non-PCOS groups, respectively. Using LSCM, there was a significant decrease in the mitochondrial membrane potential of IVM oocytes compared with the control IVF oocytes (P < 0.001), but no significant difference between the PCOS and non-PCOS groups. The NGS showed that the aneuploidy rates were comparable (75, 75, and 66.6%) in IVM-PCOS, IVM-non-PCOS, and control IVF arrested embryos, respectively.

CONCLUSIONS

The mildly stimulated IVF/M protocol produced acceptable clinical outcomes in PCOS and non-PCOS patients. IVM itself rather than the PCOS condition adversely affected the embryo development through its effect on mitochondrial function, which appeared to be a possible cause for the embryo arrest in the IVM cycles rather than chromosomal aneuploidy.

Preimplantation Genetic Testing for Aneuploidy: A Review

Importance

Preimplantation genetic testing for aneuploidy (PGT-A) has undergone many technical developments over recent years, including changes in biopsy timings, methodology, and genetic analysis techniques. The evidence surrounding the efficaciousness of PGT-A is sporadic and inconsistent; as such, significant doubt and concern remain regarding its widespread implementation.

Objective

This review seeks to describe the historical development of PGT-A and to analyze and summarize the current published literature.

Conclusions

At times during its infancy, PGT-A failed to display conclusive improvements in results; with newer technologies, PGT-A appears to yield superior outcomes, including reductions in miscarriages and multiple gestations. Clinicians and patients should assess the use of PGT-A on a case-by-case basis, with laboratories encouraged to utilize blastocyst biopsy and next-generation sequencing when conducting PGT-A. Further studies providing cumulative live birth rates and time to live birth are required if PGT-A is to be proven as producing superior outcomes.

Relevance

PGT-A has the potential ability to impact in vitro fertilization success rates, and as it is increasingly adopted worldwide, it is crucial that clinicians are aware of the evidence for its continued use.

Genetic testing on products of conception and its relationship with body mass index

PURPOSE

The study aimed to investigate the relationship between elevated maternal body mass index (BMI) and foetal chromosomal aberrations by performing single-nucleotide polymorphism (SNP) array-based genetic testing on products of conception (POC).

METHODS

We retrospectively reviewed the data for 1068 assisted reproductive technology (ART)-conceived POC originated from 1068 patients with early spontaneous miscarriage. First, all types of chromosomal abnormalities were defined. Then, the baseline characteristics, including maternal age, BMI, thyroid-stimulating hormone (TSH), gestational age, fertilization method, reasons for fertility treatment, embryo transfer (ET) cycle, stage of embryo development and the embryo morphology grade, were compared between chromosomally normal and abnormal POC groups. Finally, a multivariate logistic regression model was used to analyse various factors affecting the foetal chromosomal abnormality rate.

RESULTS

The SNP array results showed that 45.3% (484/1068) of POC were chromosomally normal and that 54.7% (584/1068) of POC presented chromosomal abnormalities. Of these 584 chromosomally abnormal POC, 388 (66.4%) were trisomy, 42 (7.2%) had a monosomy, 68 (11.6%) were found with segmental aneuploidy, 46 (7.9%) were mosaic, 28 (4.8%) were identified as polyploidy and 12 (2.1%) were euploid samples with uniparental disomy (UPD). Multivariate logistic regression results showed that the risk of miscarrying chromosomally abnormal POC increased 1.424-fold in women with normal BMI compared to women with an elevated BMI (≥ 25 kg/m²) (OR = 1.424, 95% CI = 1.074-1.888, p = 0.014).

CONCLUSION

Women with an elevated BMI (≥ 25 kg/m²) are more likely to miscarry chromosomally normal POC.

The Influence of Delayed Blastocyst Development on the Outcome of Frozen-Thawed Transfer of Euploid and Untested Embryos

Objective

The primary objective is to compare live birth rates (LBRs) following frozen embryo transfer (FET) of euploid day 5 with day 6 blastocysts. We also compared LBRs following FET of untested blastocysts vitrified on day 5 and day 6 in self-oocyte and ovum donation (OD) cycles.

Design

This was a retrospective observational study.

Setting

Nova IVF Fertility, Ahmedabad.

Materials and Methods

Ninety-seven FET using self-oocytes following preimplantation genetic testing A (PGT-A), 464 FET following OD, and 907 FET using self-oocytes without PGT-A testing between January 2016 and December 2017 were included in this study.

Main Outcome Measures

LBR following FET in day 5 versus day 6 blastocysts in euploid embryos using self-oocytes and in untested embryos using both self and donor oocytes.

Results

In PGT-A cycles, no statistically significant difference was observed in LBRs following transfer of euploid blastocysts developed on day 5 or day 6 (D5: 53%; D6:40%, P = 0.83). However, the LBRs with day 5 blastocysts were higher compared with day 6 group in untested group using both self and donor oocytes (self D5: 52.7%; D6: 38.2%; P = 0.001 and OD D5: 44.7%; D6: 29.8%; P = 0.001). Miscarriage rates were comparable in both the groups.

Conclusions

The present study demonstrated comparable pregnancy outcomes following FET of euploid embryos vitrified on day 5 and day 6. However, higher LBRs were reported in day 5 group in untested embryos.

Preimplantation genetic testing in assisted reproduction technology

A significant proportion of clinically recognized pregnancies end in miscarriage. About 50 % of early pregnancy losses are due to chromosome abnormalities. In assisted reproduction technology (ART), a high proportion of top-quality embryos with morphological values are aneuploid whenever they have been evaluated in terms of genetic integrity in human preimplantation embryos either from in vitro or in vivo matured oocytes. It is plausible to think of preimplantation genetic testing (PGT) as a means of increasing pregnancy rates and minimizing the risk of fetal aneuploidy. It is believed that PGT will assume a prominent role in the field of ART, especially in a successful pregnancy, so it is embraced recently as a popular diagnostic technique. The PGT includes three sub-categories of PGT for aneuploidies (PGT-A), PGT for single gene / monogenic disorders (PGT-M), and PGT for chromosome structural rearrangements (PGT-SR). PGT-A is used to detect aneuploidies and previously it was known as PGS. PGT-M, formerly known as PGD, is intended to reduce monogenic defects. Previously known as PGS translocation, PGT-SR is PGT to identify structural chromosomal rearrangements. Since many of the old and new definitions for PGT are still vague and confusing for some researchers in the field of reproductive genetics, the main purpose of this study is to introduce all PGT classifications as well as elaborate on different aspects of this technology to improve ART outcomes.

Cell number considerations for blastocyst transfer in younger patients

OBJECTIVE

To investigate the role of the cell number at day 3 in blastocyst selection.

DESIGN

Observational, retrospective, single-center clinical study.

PATIENT(S)

In part 1, 1211 single vitrified-warmed blastocyst transfer (SVBT) cycles were identified and reviewed. All the cycles were conventional in vitro fertilization (IVF) cycles and the first embryo transfer cycles. Most of patients had a risk of ovarian hyperstimulation syndrome and were young. In part 2, 864 IVF-derived blastocysts from 292 infertile couples underwent trophectoderm (TE) biopsy for preimplantation genetic testing for aneuploidies (PGT-A).

INTERVENTION(S)

No patient intervention.

MAIN OUTCOME MEASURE(S)

The first part was an analysis of the correlation between the cell number at day 3 and live birth rate (LBR) after SVBT, and the second part was an analysis of the correlation between the cell number at day 3 and euploid rate (ER) of blastocysts.

RESULT(S)

In part 1, after correcting for the effects of other confounders, the cell number at day 3 had no significant effect on the LBR (OR 1.001, 95% CI 0.938-1.068). In part 2, after correcting for the effects of other confounders, the cell number at day 3 had no significant effect on the ER (OR 0.960, 95% CI 0.866-1.063).

CONCLUSION(S)

When the vitrified-warmed blastocysts obtained by conventional IVF are transferred into young patients, the cell number at day 3 is not a strong predictor of the LBR. In addition, the cell number at day 3 is not a strong predictor of ER of IVF-derived blastocysts too.

Deconstructing the myth of poor prognosis for fast-cleaving embryos on day 3. Is it time to change the consensus?

PURPOSE

To determine the developmental competence of fast-cleaving D3 embryos.

METHODS

Retrospective study including 4028 embryos from 513 PGT-A cycles performed between July 2014 and June 2017. Embryos were cultured in time-lapse incubators and biopsied at blastocyst stage. Embryos were classified in groups according to the number of cells on D3 (from 2-cell to ≥13 -cell and compacted). A generalized linear mixed model adjusted for confounding factors was performed to assess the chance to give rise to an euploid blastocyst in each group compared with the chance of 8-cell embryos. Implantation and live birth rates were also analyzed.

RESULTS

The statistical analysis showed that embryos with 9 to 11 cells had a slightly lower euploid blastocyst rate than 8-cell embryos (OR (95% CI) 0.77 (0.61-0.96)) while embryos with more than 11 cells were found to be just as likely to give rise to an euploid blastocyst as the 8-cell embryos (OR (95% CI) 1.20 (0.92-1.56)). Conversely, slow-cleaving embryos had a significantly lower euploid blastocyst rate than 8-cell embryos (OR (95% CI) 0.31 (0.24-0.39)). Moreover, euploid blastocysts derived from fast-cleaving embryos and from 8-cell embryos exhibit similar live birth rates. No significant differences were found in the chance to give rise a live birth between 8-cell and 9- to 11-cell embryos (OR (95% CI) 1.23 (0.70-2.15)) and > 11-cell embryos (OR (95% CI) 1.09 (0.57-2.09)).

CONCLUSIONS

Embryos with more than 11 cells exhibit similar developmental competence to 8-cell embryos. Their poor prognosis should be reconsidered.

Deconstructing the myth of poor prognosis for fast-cleaving embryos on day 3. Is it time to change the consensus?

PURPOSE

To determine the developmental competence of fast-cleaving D3 embryos.

METHODS

Retrospective study including 4028 embryos from 513 PGT-A cycles performed between July 2014 and June 2017. Embryos were cultured in time-lapse incubators and biopsied at blastocyst stage. Embryos were classified in groups according to the number of cells on D3 (from 2-cell to ≥13 -cell and compacted). A generalized linear mixed model adjusted for confounding factors was performed to assess the chance to give rise to an euploid blastocyst in each group compared with the chance of 8-cell embryos. Implantation and live birth rates were also analyzed.

RESULTS

The statistical analysis showed that embryos with 9 to 11 cells had a slightly lower euploid blastocyst rate than 8-cell embryos (OR (95% CI) 0.77 (0.61-0.96)) while embryos with more than 11 cells were found to be just as likely to give rise to an euploid blastocyst as the 8-cell embryos (OR (95% CI) 1.20 (0.92-1.56)). Conversely, slow-cleaving embryos had a significantly lower euploid blastocyst rate than 8-cell embryos (OR (95% CI) 0.31 (0.24-0.39)). Moreover, euploid blastocysts derived from fast-cleaving embryos and from 8-cell embryos exhibit similar live birth rates. No significant differences were found in the chance to give rise a live birth between 8-cell and 9- to 11-cell embryos (OR (95% CI) 1.23 (0.70-2.15)) and > 11-cell embryos (OR (95% CI) 1.09 (0.57-2.09)).

CONCLUSIONS

Embryos with more than 11 cells exhibit similar developmental competence to 8-cell embryos. Their poor prognosis should be reconsidered.

Clinical outcomes after the transfer of blastocysts characterized as mosaic by high resolution Next Generation Sequencing- further insights

OBJECTIVE

To determine the pregnancy outcome potential of euploid, mosaic and aneuploid embryos.

DESIGN

Retrospective study.

SETTING

Reference genetics laboratories.

PATIENT(S)

2654 PGT-A cycles with euploid characterized embryo transfers, 253 PGT-A cycles with transfer of embryos characterized as mosaic, and 10 PGT-A cycles with fully abnormal embryo transfers.

INTERVENTION(S)

Blastocysts were assessed by trophectoderm (TE) biopsy followed by PGT-A via array CGH or NGS.

MAIN OUTCOME MEASURE(S)

Implantation, miscarriage, ongoing implantation rates (OIR), and karyotype if available, were compared between different embryo groups, and between the two PGT-A techniques.

RESULTS

The Ongoing Pregnancy Rate (OPR)/transfer was significantly higher for NGS-classified euploid embryos (85%) than for aCGH ones (71%) (p < 0.001), but the OPR/cycle was similar (63% vs 59%). NGS-classified mosaic embryos resulted in 37% OPR/cycle (p < 0.001 compared to euploid). Mosaic aneuploid embryos with <40% abnormal cells in the TE sample had an OIR of 50% compared to 27% for mosaics with 40-80% abnormal cells in the TE, and 9% for complex mosaic embryos. All the karyotyped ongoing pregnancies (n = 29) were euploid. Transfers of embryos classified as aneuploid via aCGH (n = 10) led to one chromosomally abnormal pregnancy.

CONCLUSION(S)

NGS-classified euploid embryos yielded higher OIRs but similar OPRs/cycle compared to aCGH. NGS-classified mosaic embryos had reduced potential to reach term, compared to euploid embryos. If they did reach term, those with karyotype results available were euploid. Embryos carrying uniform aneuploidies affecting entire chromosomes were mostly unable to implant after transfer, and the one that implanted ended up in a chromosomally abnormal live birth.

Cryopreservation of incomplete compacted morulae and preliminary biopsy of excluded fragments

The complexity of predicting embryo development potential at the cleavage stages and the emergence of epigenetic risks during prolonged in vitro culture of pre-implantation embryos made it more advantageous to transfer embryos at the morula stage to the uterine cavity. The criteria for estimating embryos at this stage that allow prediction of cryopreservation outcomes have been poorly described. All day 4 embryos (n = 224) were graded 1, 2, 3, 4 or 5 according to blastomere compaction degree (BCD = 100, 75, 50, 25 or 0%, respectively) and the survival and blastocyst formation rate of these morulae were studied after cryopreservation. An inverse dependence was found between survival rate and BCD. Excluded fragments were characterized by low osmotic reaction during exposure to cryoprotective medium and, after freeze-thawing, they were destroyed. As damaged necrotic areas of the embryo can affect their further development rate we proposed blastomeres and biopsy fragments of incomplete compacted morula be removed before embryo cryopreservation. This step led to significant increase in the post-thawing survival rate up to 93.1 ± 4.1%, 75 ± 8.8% and blastocyst formation rate up to 85.2 ± 10.4%, 59.4 ± 5.2% in grade 2 and grade 3 embryos, respectively. There was no significant difference in grade 4 embryos. Therefore the removal of blastomeres and biopsy fragments in incomplete compacted morulae can improve cryopreservation outcomes of grade 2 and grade 3 embryos with BCD.

Optimal timing for blastomere biopsy of 8-cell embryos for preimplantation genetic diagnosis

STUDY QUESTION

What is the optimal timing for blastomere biopsy during the 8-cell stage, at which embryos will have the best implantation potential?

SUMMARY ANSWER

Fast-cleaving embryos that are biopsied during the last quarter (Q4) of the 8-cell stage and are less affected by the biopsy procedure, and their implantation potential is better than that of embryos biopsied earlier during the 8-cell stage (Q1-Q3).

WHAT IS KNOWN ALREADY

Blastomer biopsy from cleavage-stage embryos is usually performed on the morning of Day 3 when the embryos are at the 6- to 8-cell stage and is still the preferred biopsy method for preimplantation genetic diagnosis (PGD) for monogentic disorders or chromosomal translocations. Human embryos usually remain at the 8-cell stage for a relatively long 'arrest phase' in which cells grow, duplicate their DNA and synthesize various proteins in preparation for the subsequent division.

STUDY DESIGN, SIZE, DURATION

This is a retrospective cohort study. The study group (195 embryos) included all 8-cell stage embryos that underwent blastomere biopsy for PGD for monogenetic disorders and chromosomal translocations in our unit between 2012-2014 and cultured in the EmbryoScope until transfer. The control group (115 embryos) included all embryos that underwent intracytoplasmic sperm injection without a biopsy during the same period.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The 8-cell stage was divided into four quarters: the first 5 h post-t8 (Q1), 5-10 h post-t8 (Q2), 10-15 h post-t8 (Q3) and at 15-20 h post-t8 (Q4). Non-biopsied control embryos were divided into four equivalent quarters. Embryos were evaluated for timing of developmental events following biopsy including timing of first cleavge after biopsy, timing of comapction (tM) and start of blastulation (tSB). Timing of these events were compared between PGD and control embryos, as well as with 56 PGD implanted embryos with Known Implantation Data (PGD-KID-positive embryos).

MAIN RESULTS AND THE ROLE OF CHANCE

Embryos that were biopsied during Q3 (10-15 h from entry into 8-cell stage) were delayed in all three subsequent developmental events, including first cleavage after biopsy, compaction and start of blastulation. In contrast, these events occurred exactly at the same time as in the control group, in embryos that were biopsied during Q1, Q2 or Q4 of the 8-cell stage. The results show also that embryos that were biopsied during Q1, Q2 or Q3 of the 8-cell stage demonstrated a significant delay from the biopsied implanted embryos already in t8 as well as in tM and tSB. However, embryos that were biopsied during Q4 demonstrated dynamics similar to those of the biopsied implanted embryos in t8 and tM, and a delay was noticed only in the last stage of tSB.

LIMITATIONS, REASONS FOR CAUTION

This is a retrospective study that is limited to the timing of biopsy that is routinely performed in the IVF lab. A prospective study in which biopsy will be performed at a desired timing is needed in order to differ between the effect of biopsy itself and the cleavage rate of the embryo.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings showed that blastomere biopsy can be less harmful to further development if it is carried out during a critical period of embryonic growth, i.e during Q4 of the 8-cell stage. They also demonstrated the added value of time-lapse microscopy for determining the optimal timing for blastomere biopsy.

STUDY FUNDING/COMPETING INTEREST(S)

The study was funded by the routine budget of our IVF unit.

TRIAL REGISTRATION NUMBER

N/A.

Preimplantation genetic diagnosis and screening (PGD/S) using a semiconductor sequencing platform

Background

Recent advances in semiconductor sequencing platform (SSP) have provided new methods for preimplantation genetic diagnosis/screening (PGD/S). The present study aimed to evaluate the applicability and efficiency of SSP in PGD/S.

Methods

The artificial positive single-cell-like DNAs and normal single-cell samples were chosen to test our semiconductor sequencing platform for preimplantation genetic diagnosis/screening (SSP-PGD/S) method with two widely used whole-genome amplification (WGA) kits. A total of 557 single blastomeres were collected from in vitro fertilization (IVF) couples, and their WGA products were processed and analyzed by our SSP-PGD/S method in comparison with array comparative genomic hybridization (array-CGH).

Results

Our SSP-PGD/S method indicated high compatibilities with two commercial WGA kits. For 557 single blastomeres, our method with four million reads in average could detect 24-chromosome aneuploidies as well as microdeletion/microduplication of the size over 4 Mb, providing 100% consistent conclusion with array-CGH method in the classification of whether it was transplantable.

Conclusions

Our studies suggested that SSP-PGD/S represents a valuable alternative to array-CGH and brought PGD/S into a new era of more rapid, accurate, and economic.

Electronic supplementary material

The online version of this article (10.1186/s40246-018-0187-x) contains supplementary material, which is available to authorized users.

Deoxyribonucleic acid detection in blastocoelic fluid: a new predictor of embryo ploidy and viable pregnancy

OBJECTIVE

To investigate blastocysts, defined as euploid and aneuploid by trophectoderm (TE) cell analysis, for the presence of DNA in the blastocoelic fluid (BF) detected by whole-genomic amplification (WGA); and to correlate the presence of DNA in BF with the clinical outcome after the transfer of TE-euploid blastocysts.

DESIGN

Retrospective study.

SETTING

In vitro fertilization unit.

PATIENT(S)

This study included 91 patients performing preimplantation genetic testing for aneuploidy on TE cells from January 2015 to December 2017. In the case of ET, only single blastocyst transfers were performed.

INTERVENTION(S)

Blastocoelic fluids and TE cells were retrieved from 256 blastocysts before vitrification. All blastocysts were diagnosed by array-comparative genomic hybridization (a-CGH) on TE cells. Amplification and a-CGH of DNA from BFs was performed at a later time after TE biopsy and ET.

MAIN OUTCOME MEASURE(S)

Whole-genomic amplification of BFs, evaluation of the chromosome condition in BFs and TE cells, and correlation of BF results with the clinical outcome of TE-euploid transferred blastocysts.

RESULT(S)

The incidence of amplification after WGA was significantly lower in BFs from TE-euploid blastocysts (n = 32, 45%) when compared with the aneuploid ones (n = 150, 81%), resulting in 182 BFs with successful DNA amplification. When submitted to a-CGH, informative results were obtained from 172 BFs. Comparison of these results with those from the corresponding TE cells gave a ploidy concordance of 93.6% and a mean number of aneuploid events per sample that was higher in BFs than in TE cells (2.0 vs. 1.4, respectively). After the transfer of 53 TE-euploid blastocysts, the clinical pregnancy rate was 77% in the group with BF-failed amplification, and 37% after BF-successful amplification. The same trend was found for the ongoing pregnancy rate (68% vs. 31.5%, respectively).

CONCLUSION(S)

The presence of DNA in BFs detected by WGA is correlated with the blastocyst ploidy condition defined by TE cell biopsy and with the implantation potential of TE-euploid blastocysts. These findings could have a clinical implication for the selection of the most viable embryo for transfer because, after submitting BFs to WGA, priority would be given to TE-euploid blastocysts with BF-failed amplification. Similarly, BF-failed amplification could be an additional selection criterion to prioritize embryos for transfer even in conventional IVF cycles with blastocysts that were vitrified after BF aspiration.

Prevalence and authenticity of de-novo segmental aneuploidy (>16 Mb) in human blastocysts as detected by next-generation sequencing

RESEARCH QUESTION

What is the prevalence and authenticity of de-novo segmental aneuploidies (>16 Mb) detected by next-generation sequencing (NGS) in human preimplantation blastocysts?

DESIGN

Between April 2013 and June 2016, 5735 blastocysts from 1854 couples (average age 33.11 ± 5.65 years) underwent preimplantation genetic testing for chromosomal structural rearrangement (PGT-SR) or for aneuploidy (PGT-A) using NGS on trophectoderm (TE) biopsy samples. The prevalence of de-novo segmental aneuploidy was calculated from these results. Forty blastocysts with de-novo segmental aneuploidy detected by NGS, which had been donated for research, were warmed for further fluorescence in-situ hybridization (FISH) analysis to confirm their authenticity.

RESULTS

The frequency of de-novo segmental aneuploidies in blastocysts was 10.13% (581/5735); the phenomenon was not related to maternal age and occurred on all chromosomes. Of the 40 donated blastocysts, 39 were successfully warmed and fixed for FISH analysis at the single-cell level. The de-novo segmental aneuploidies identified by NGS were confirmed by FISH in all 39 blastocysts. However, the de-novo segmental aneuploidies in these blastocysts were not all pure patterns, with 66.67% (26/39) of blastocysts exhibiting mosaic patterns varying from 8.30% to 92.86% of cells with de-novo segmental aneuploidy. The concordance rate between NGS and FISH in TE and inner cell mass (ICM) samples was 47.69% (31/65).

CONCLUSIONS

De-novo segmental aneuploidy above 16 Mb occurred in blastocysts and could be detected by NGS, while some aneuploidies existed as mosaics in both TE and ICM.

Live Birth from the Transfer of a Severely Fragmented Embryo Observed by Morphokinetics

We report a live birth from a heavily fragmented embryo which continued cleavage to a fully expanded blastocyst. A 32-year-old patient underwent 2 IVF cycles without achieving pregnancy. In the first cycle, 2 embryos with fragmentation were transferred; in the second, all embryos were fragmented and no embryo transfer was performed. In a third cycle, 12 oocytes were retrieved and 11 of them were fertilized. On day 2, all 11 embryos started to unwind to fragments. By careful annotation, using the time-lapse EmbryoScope, we observed that one embryo continued division as expected, discarding all fragments aside. On day 5, this embryo showed promising annotation according to our lab model. The embryo was transferred into the uterus and resulted in the birth of a healthy baby at term. To our knowledge, this is the first case report assisted by EmbryoScope where a healthy baby was delivered from a fragmented embryo.

Do patients who achieve pregnancy using IVF-PGS do the recommended genetic diagnostic testing in pregnancy?

PURPOSE

Patients undergoing in-vitro fertilization (IVF) with preimplantation genetic screening (PGS) are counseled about the limitations of this technique. As part of the consent process for PGS, physicians recommend diagnostic genetic testing performed in early pregnancy to definitively rule out chromosomal abnormalities. We have noted anecdotally, however, that few patients undergo the recommended diagnostic testing. In this study, we are examining if women who conceived using IVF-PGS did early pregnancy chromosomal testing, and if they did, what type of testing they had.

METHODS

This study was performed from 2015 to 2017 in the Division of Reproductive Endocrinology and Infertility at Northwestern University. We included patients who became pregnant after IVF-PGS who were seen by the Division of Reproductive Genetics and non-PGS control group.

RESULTS

Sixty-eight patients were included. A total of 50 patients (73.5%) opted for non-invasive prenatal screening; 5 (7.4%) had invasive testing (4 had chorionic villus sampling and 1 had amniocentesis). A total of 13 patients (19%) declined further genetic testing. When comparing demographic data, the mean age was significantly higher in the group of patients who pursued non-invasive testing than in the group who declined further testing (37.15 vs 34.05 years old, p < 0.05). Control group declined invasive diagnostic testing.

CONCLUSIONS

Most patients who conceive using IVF-PGS do not pursue diagnostic prenatal chromosomal testing. Future studies focusing on decision making in this patient group are warranted to further elucidate why a small percentage of patients opt for diagnostic testing, even when adequately counseled about the inherent limitations of PGS.

Euploidy in relation to blastocyst sex and morphology

PURPOSE

The objective of our study is to assess the relationship of embryo ploidy status in relation to embryo sex, morphological characteristics, and transfer parameters.

METHODS

This is a retrospective cohort study at an academic medical center of patients who underwent in vitro fertilization with preimplantation genetic screening (PGS) from 2010 to 2015. Embryos were screened with 24-chromosome preimplantation genetic screening with day 5/6 trophectoderm biopsy. We investigated embryo euploidy in relation to morphology (expansion, inner cell mass, trophectoderm), embryo sex, biopsy day, and blastocyst cohort size. We used multivariate logistic regression to calculate odds ratios of euploidy in relation to these parameters.

RESULTS

A total of 1559 embryos from 316 cycles and 233 patients (mean maternal age = 37.8 ± 4.2 years) were included in the analysis. Six hundred and twenty-eight blastocysts (40.3%) were found to be euploid. Expansion (p < 0.001), inner cell mass (ICM) (p < 0.01), and trophectoderm grade (p < 0.001) were significantly associated with embryo ploidy in bivariate models controlling for maternal age, while embryo sex, biopsy day, and blastocyst cohort size were not associated with embryo ploidy. In a multivariate model, we found that maternal age (p < 0.001), higher grade of expansion (p < 0.01), and better quality trophectoderm (p < 0.001 for A compared to C grade) remained significantly associated with increased embryo euploidy, but ICM grade was no longer significant. Embryo sex was not associated with ploidy status, though male embryos were found to be associated with higher trophectoderm scores (p < 0.02).

CONCLUSIONS

This is the largest study to date to investigate PGS-tested embryo sex and ploidy status. While maternal age and some morphological parameters (expansion, trophectoderm grade) are associated with euploidy in our cohort, other parameters such as embryo sex, biopsy day, and cohort size are not. Though embryo sex was not associated with euploidy, male embryos were found to be associated with higher trophectoderm grades. Additional investigation in larger studies is warranted.

Mesenchymal Stem Cell-Conditioned Medium Modulates Apoptotic and Stress-Related Gene Expression, Ameliorates Maturation and Allows for the Development of Immature Human Oocytes after Artificial Activation

The aim of the present study was to determine whether mesenchymal stem cell-conditioned medium (MSC-CM) modulates apoptotic and stress-related gene expression, and ameliorates maturation and developmental potential of immature human oocytes after artificial activation. A total of 247 surplus immature germinal vesicle (GV) oocytes obtained from infertile women were allocated into two in vitro maturation (IVM) groups: 1: GV oocytes (n = 116) matured in vitro (fIVM), and 2: GV oocytes (n = 131) that were vitrified, then in vitro matured (vIVM). Also, two maturation media were used: Alpha-minimum essential medium (α-MEM) and human umbilical cord-derived MSCs (hUCM). After 36 h of incubation, the IVM oocytes were examined for nuclear maturation. In IVM-matured oocytes, cytoplasmic maturation was evaluated after artificial activation through Ionomycin. Moreover, the quantitative expressions of B-cell CLL/lymphoma 2 (BCL2), BCL2-associated X protein (BAX), superoxide dismutase (SOD), and Heat shock proteins (HSP70) in matured oocytes were assessed by quantitative Real-time polymerase chain reaction (qRT-PCR) and compared with fresh and vitrified in vivo matured oocytes, which were used as fIVM and vIVM controls, respectively. The highest maturation rate was found in hUCM in fIVM, and the lowest maturation rate was found using α-MEM in vIVM (85.18% and 71.42%, respectively). The cleavage rate in fIVM was higher than that in vIVM (83.4% vs. 72.0%). In addition, the cleavage rate in α-MEM was lower than that in the hUCM (66.0% vs. 89.4%). Furthermore, the difference between parthenote embryo arrested in 4-8 cells (p < 0.04) and the quality of embryo arrested in 8-cell (p < 0.007) were significant. The developmental stages of parthenote embryos in hUCM versus α-MEM were as follows: 2-4 cell (89.45% vs. 66.00%, respectively), 4-8 cell (44.31% vs. 29.11%, respectively), morula (12.27% vs. 2.63%, respectively), and blastocysts (2.5% vs. 0%, respectively). The messenger RNA (mRNA) expression levels of BCL2, BAX and SOD were significantly different (p < 0.05) between the matured IVM oocytes. Overall, hUCM showed potential efficacy in terms of ameliorating oocyte maturation and in promoting the development and mRNA expression of BAX, BCL2, and SOD.

SV40 Large T Antigen Disrupts Embryogenesis of Canine and Porcine Somatic Cell Nuclear Transfer Embryo

Background

Somatic cell nuclear transfer (SCNT) is a useful biotechnological tool for transgenic animal production using genetically modified somatic cells (GMSCs). However, there are several limitations preventing successful transgenic animal generation by SCNT, such as obtaining proper somatic donor cells with a sufficiently long life span and proliferative capacity for generating GMSCs. Here, we established simian virus 40 large T antigen (SV40LT)-mediated lifespan-extended canine fibroblast cells (SV40LT-K9 cells) and evaluated their potential as nuclei donors for SCNT, based on cellular integrity and SCNT embryo development.

Results

SV40LT did not cause canine cell transformation, based on cell morphology and proliferation rate. No anchorage-independent growth in vitro and tumorigenicity in vivo were observed. After SCNT with SV40LT-K9 cells, embryos were transferred into surrogate dogs. All dogs failed to become pregnant. Most embryos did not proceed past the 8-cell stage and only one surrogate showed an implantation trace in its oviduct, indicating that the cells rarely developed into blastocysts. Because of the absence of an in vitro maturation method for canine embryos, we performed identical experiments using porcine fibroblast cells. Similarly, SV40LT did not transform porcine fibroblast cells (SV40LT-Pig cells). During in vitro development of SV40LT-Pig cell-driven SCNT embryos, their blastocyst formation rate was clearly lower than those of normal cells. Karyotyping analysis revealed that both SV40LT-K9 and SV40LT-Pig cells had aberrant chromosomal statuses.

Conclusions

Although lifespan-extended canine and porcine cells via SV40LT exhibit no apparent transforming changes, they are inappropriate for use as nuclei donors for SCNT because of their aneuploidy.