Maternal age, morphology, development and chromosome abnormalities in over 6000 cleavage-stage embryos

Successful haematopoietic stem cell transplantation in 44 children from healthy siblings conceived after preimplantation HLA matching

Haematopoietic stem cell transplantation (HSCT) remains the best therapeutic option for many acquired and inherited paediatric haematological disorders. Unfortunately, the probability of finding an HLA matched donor is limited. An alternative technique is PGD combined with HLA matching, which offers the possibility of selecting unaffected embryos that are HLA compatible with the sick child, with the aim of possible use of stem cells from the resulting baby in future. Since the first successful report for Fanconi anaemia a decade ago, the therapeutic success of this technique was reported in a few cases and for a limited number of disorders. Here, we report full recovery of 44 sick children who received HSCT from healthy infants conceived after pre-implantation HLA matching for the following 10 indications; beta-thalassaemia, Wiskott-Aldrich syndrome, Fanconi anaemia, sickle cell anaemia, acute myeloid leukaemia, acute lymphoblastic leukaemia, Glanzmann's thrombasthaenia, Diamond-Blackfan anaemia, X-linked adrenoleukodystrophy and mucopolysaccharidosis type I. No serious complications were observed among recipients and donors. Graft failure occurred in four children with beta-thalassaemia where a second HSCT was planned. Preimplantation HLA matching is a reliable technique and provides a realistic option for couples seeking treatment for an affected child when no HLA-matched donor is available.

The origin, mechanisms, incidence and clinical consequences of chromosomal mosaicism in humans

BACKGROUND

Chromosomal mosaicism, the presence of two or more distinct cell lines, is prevalent throughout human pre- and post-implantation development and can lead to genetic abnormalities, miscarriages, stillbirths or live births. Due to the prevalence and significance of mosaicism in the human species, it is important to understand the origins, mechanisms and incidence of mosaicism throughout development.

METHODS

Literature searches were conducted utilizing Pubmed, with emphasis on human pre- and post-implantation mosaicism.

RESULTS

Mosaicism persists in two separate forms: general and confined. General mosaicism is routine during human embryonic growth as detected by preimplantation genetic screening at either the cleavage or blastocyst stage, leading to mosaicism within both the placenta and fetus proper. Confined mosaicism has been reported in the brain, gonads and placenta, amongst other places. Mosaicism is derived from a variety of mechanisms including chromosome non-disjunction, anaphase lagging or endoreplication. Anaphase lagging has been implicated as the main process by which mosaicism arises in the preimplantation embryo. Furthermore, mosaicism can be caused by any one of numerous factors from paternal, maternal or exogenous factors such as culture media or possibly controlled ovarian hyperstimulation during in vitro fertilization (IVF). Mosaicism has been reported in as high as 70 and 90% of cleavage- and blastocyst-stage embryos derived from IVF, respectively.

CONCLUSIONS

The clinical consequences of mosaicism depend on which chromosome is involved, and when and where an error occurs. Mitotic rescue of a meiotic error or a very early mitotic error will typically lead to general mosaicism while a mitotic error at a specific cell lineage point typically leads to confined mosaicism. The clinical consequences of mosaicism are dependent on numerous aspects, with the consequences being unique for each event.

Morphological good-quality embryo has higher nucleus spreading rate/signal resolution rate in fluorescence in situ hybridization

PURPOSE

To evaluate the relationship between day 3 embryo quality and nucleus spreading rate/signal resolution rate in Fluorescence in situ hybridization (FISH) during the PGD procedure.

METHODS

This study was a retrospective data analysis. 367 day-3 embryos were classified based on morphological scoring: grade 1 to grade 4 were defined from worse to better embryo quality. Day 3 embryos were classified as good quality when the number of blastomeres was between 6 and 10 and grade better than 2'. Nucleus spreading rate, signal rate and the full signal rate were compared between embryos with different morphological scoring.

RESULTS

Nucleus spreading rate of blastomeres from morphological high-quality embryos was significantly higher (86.25 %) than from poor-quality embryos (76.53 %) (p < 0.05). The rate of blastomeres with full signals was significantly higher (79.32 %) in the morphological high-quality group than in poor-quality group (64.54 %) (p < 0.05). Similar results were found from day 3 embryos with cell number between 6 cells and 10 cells (nucleus spreading rate 86.01 vs. 76.34 %, p < 0.05; full signal rate 78.72 vs. 62.71 %, p < 0.05). Both have no significant difference in the signal rate (82.67 vs. 89.66 %; 83.10 vs. 89.95 %).

CONCLUSIONS

Blastomeres from day 3 embryos with better morphological quality had higher nucleus spreading rate and higher full signal rate during FISH. Through this study, we speculate on whether it should reconsider the necessity of FISH application in embryos with poor quality.

Genome analyses of single human oocytes

Single-cell genome analyses of human oocytes are important for meiosis research and preimplantation genomic screening. However, the nonuniformity of single-cell whole-genome amplification hindered its use. Here, we demonstrate genome analyses of single human oocytes using multiple annealing and looping-based amplification cycle (MALBAC)-based sequencing technology. By sequencing the triads of the first and second polar bodies (PB1 and PB2) and the oocyte pronuclei from same female egg donors, we phase the genomes of these donors with detected SNPs and determine the crossover maps of their oocytes. Our data exhibit an expected crossover interference and indicate a weak chromatid interference. Further, the genome of the oocyte pronucleus, including information regarding aneuploidy and SNPs in disease-associated alleles, can be accurately deduced from the genomes of PB1 and PB2. The MALBAC-based preimplantation genomic screening in in vitro fertilization (IVF) enables accurate and cost-effective selection of normal fertilized eggs for embryo transfer.

Deubiquitinating enzymes in oocyte maturation, fertilization and preimplantation embryo development

Post-translational modifications of cellular proteins by ubiquitin and ubiquitin-like protein modifiers are important regulatory events involved in diverse aspects of gamete and embryo physiology including oocyte maturation, fertilization and development of embryos to term. Deubiquitinating enzymes (DUBs) regulate proteolysis by reversing ubiquitination, which targets proteins to the 26S proteasome. The ubiquitin C-terminal hydrolases (UCHs) comprise are DUBs that play a role in the removal of multi-ubiquitin chains. We review here the roles of UCHs in oocytes maturation, fertilization and development in mouse, bovine, porcine and rhesus monkeys. Oocyte UCHs contributes to fertilization and embryogenesis by regulating the physiology of the oocyte and blastomere cortex as well as oocyte spindle. Lack of UCHs in embryos reduces fertilization, while mutant embryos fail to undergo compaction and blastocyst formation. In addition to advancing our understanding of reproductive process, research on the role of deubiquitinating enzymes will allow us to better understand and treat human infertility, and to optimize reproductive performance in agriculturally important livestock species.

Quality of embryos transferred and progesterone levels are the most important predictors of live birth after fresh embryo transfer: a retrospective cohort study

PURPOSE

To identify the independent predictors of live birth following IVF, and to assess the role of cohort-specific parameters, including antral follicle count (AFC), the number of oocytes retrieved, the total number of embryos, and the total number of good-quality embryos, in fresh IVF cycles.

METHODS

A retrospective cohort study of 2,525 infertile women undergoing IVF between 2002 and 2007. The hypothesis that the number and quality of embryos transferred capture the effects previously attributed to cohort-specific variables was examined using mediation analysis and spline analysis. Independent predictors were identified by a bootstrap algorithm. Multivariable logistic regression was performed and the proportion of explained variation was measured to compare the relative importance of transfer-specific vs. cohort-specific predictors.

RESULTS

The number of good-quality embryos transferred and progesterone level on the day of hCG administration ranked as the two most important predictors of live birth. Prospects of pregnancy started to decrease after progesterone level exceeded 0.6 ng/ml. The achievement of live birth in a fresh IVF cycle is primarily determined by the number and quality of embryos transferred, rather than by embryo cohort-specific variables.

CONCLUSIONS

The associations between cohort-specific variables and live birth in a fresh IVF cycle are completely mediated by the quality of embryos transferred. Progesterone level on the day of hCG administration is an independent predictor of pregnancy and merits further investigation.

Selection of euploid blastocysts for cryopreservation with array comparative genomic hybridization (aCGH) results in increased implantation rates in subsequent frozen and thawed embryo transfer cycles

BACKGROUND

In assisted reproductive treatments, embryos remaining after fresh embryo transfer are usually selected for cryopreservation based on traditional morphology assessment. Our previous report has demonstrated that array comparative genomic hybridization (aCGH) screening for IVF patients with good prognosis significantly improves clinical and ongoing pregnancy rates in fresh embryo transfer cycles. The current study further investigates the efficiency of applying aCGH in the selection of euploid embryos for cryopreservation as related to pregnancy and implantation outcomes in subsequent frozen embryo transfer (FET) cycles.

METHODS

First-time IVF patients with good prognosis undergoing fresh single embryo transfer and having at least one remaining blastocyst for cryopreservation were prospectively randomized into two groups: 1) Group A patients had embryos assessed by morphology first and then by aCGH screening of trophectoderm cells and 2) Group B patients had embryos evaluated by morphology alone. All patients had at least one blastocyst available for cryopreservation after fresh embryo transfer. There were 15 patients in Group A and 23 patients in Group B who failed to conceive after fresh embryo transfer and completed the FET cycles. Blastocyst survival and implantation rates were compared between the two groups.

RESULTS

There were no significant differences in blastocyst survival rates between Group A and Group B (90.9% vs. 91.3%, respectively; p >0.05). However, a significantly higher implantation rate was observed in the morphology assessment plus aCGH screening group compared to the morphology assessment alone group (65.0% vs. 33.3%, respectively; p = 0.038). There was no miscarriage observed in Group A while a 16.7% miscarriage rate was recorded in Group B (0% vs. 16.7%, respectively; p >0.05).

CONCLUSIONS

While aCGH screening has been recently applied to select euploid blastocysts for fresh transfer in young, low-risk IVF patients, this is the first prospective study on the impact of aCGH specifically on blastocyst survival and implantation outcomes in the subsequent FET cycles of IVF patients with good prognosis. The present study demonstrates that aCGH screening of blastocysts prior to cryopreservation significantly improves implantation rates and may reduce the risk of miscarriage in subsequent FET cycles. Further randomized clinical studies with a larger sample size are needed to validate these preliminary findings.

Could time-lapse embryo imaging reduce the need for biopsy and PGS?

PURPOSE

To review relevant studies examining the relationship between embryo morpho-kinetics and aneuploidy.

METHODS

Search of Pubmed and Medline using relevant keywords pertaining to morphology, morphokinetics and embryonic aneuploidy, as well as examination of various reference lists and conference proceedings.

RESULTS

An abundance of publications, both preliminary and peer-reviewed, have emerged regarding the usefulness of time-lapse imaging in tracking embryo development and improving embryo selection. Recently, these publications have explored ability to not only predict blastocyst formation and implantation, but also the ability to detect embryonic chromosomal aneuploidy. Of the two peer-reviewed retrospective studies on morpho-kinetics and embryonic aneuploidy, one demonstrates that early cleavage timings can indicate chromosomal complement, while the other demonstrates that key events following the maternal-zygotic transition can be markers of aneuploidy. A recent paper also demonstrates improved outcomes following IVF using a selection algorithm to identify embryos at "low risk" of chromosomal abnormalities. However, the predictive nature of these events and timings is far from ideal. Additionally, results may be dependent upon the day of biopsy and method utilized for chromosomal assessment.

CONCLUSION

With continued effort, the combination of multiple morphologic endpoint assessments and developmental timings and refinement of modeling systems may improve the predictive ability to determine embryonic aneuploidy. This may help select a subset of embryos that are less likely to carry chromosomal abnormalities and improve assisted reproductive outcomes. However, embryo biopsy, followed by preimplantation genetic screening/comprehensive chromosomal screening still remains the most reliable method to assess chromosomal complement of preimplantation embryos.

Centrosome amplification and chromosomal instability in human and animal parthenogenetic cell lines

Parthenotes have been proposed as a source of embryonic stem cells but they lack the centriole which is inherited through the sperm in all mammalian species, except for rodents. We investigated the centrosome of parthenotes and parthenogenetic embryonic stem cells using parthenogenetic and biparental pig pre-implantation embryos, human and pig parthenogenetic and biparental embryonic stem cells, sheep fibroblasts derived from post implantation parthenogenetic and biparental embryos developed in vivo. We also determined the level of aneuploidy in parthenogenetic cells. Oocytes of all species were activated using ionomycin and 6-dimethylaminopurine (6-DMAP). Over 60% of parthenogenetic blastomeres were affected by an excessive number of centrioles. Centrosome amplification, was observed by microscopical and ultrastructural analysis also in parthenogenetic cell lines of all three species. Over expression of PLK2 and down regulation of CCNF, respectively involved in the stimulation and inhibition of centrosome duplication, were present in all species. We also detected down regulation of spindle assembly checkpoint components such as BUB1, CENPE and MAD2. Centrosome amplification was accompanied by multipolar mitotic spindles and all cell lines were affected by a high rate of aneuploidy. These observations indicate a link between centrosome amplification and the high incidence of aneuploidy and suggest that parthenogenetic stem cells may be a useful model to investigate how aneuploidy can be compatible with cell proliferation and differentiation.

Preimplantation genetic diagnosis for aneuploidy and translocations using array comparative genomic hybridization

At least 50% of human embryos are abnormal, and that increases to 80% in women 40 years or older. These abnormalities result in low implantation rates in embryos transferred during in vitro fertilization procedures, from 30% in women <35 years to 6% in women 40 years or older. Thus selecting normal embryos for transfer should improve pregnancy results. The genetic analysis of embryos is called Preimplantation Genetic Diagnosis (PGD) and for chromosome analysis it was first performed using FISH with up to 12 probes analyzed simultaneously on single cells. However, suboptimal utilization of the technique and the complexity of fixing single cells produced conflicting results. PGD has been invigorated by the introduction of microarray testing which allows for the analysis of all 24 chromosome types in one test, without the need of cell fixation, and with staggering redundancy, making the test much more robust and reliable. Recent data published and presented at scientific meetings has been suggestive of increased implantation rates and pregnancy rates following microarray testing, improvements in outcome that have been predicted for quite some time. By using markers that cover most of the genome, not only aneuploidy can be detected in single cells but also translocations. Our validation results indicate that array CGH has a 6Mb resolution in single cells, and thus the majority of translocations can be analyzed since this is also the limit of karyotyping. Even for translocations with smaller exchanged fragments, provided that three out of the four fragments are above 6Mb, the translocation can be detected.

Does the number of oocytes retrieved influence pregnancy after fresh embryo transfer?

Background

The nature of the association between the number of oocytes retrieved and in vitro fertilization (IVF) outcomes after fresh embryo transfer remains unclear because of conflicting results reported in the studies on this subject. In addition, the influence of the quality of the embryos transferred is usually neglected. The objective of this study is to assess the relationships of the number of oocytes retrieved, the number and quality of embryos transferred, and the prospects of pregnancy after fresh embryo transfer.

Methods

The data on 3131 infertile women undergoing their first IVF treatment cycle between January 2009 and December 2010 were collected retrospectively. Restricted cubic splines and stratified analyses were used to explore the relationships between the number of oocytes retrieved, the number and quality of embryos transferred, and the IVF outcomes.

Results

When stratified by the number and quality of transferred embryos, no significant differences in the chances for clinical pregnancy and live birth were found in three groups of oocytes yielded (≤6, 7–14, or ≥15). The relationship between the number of oocytes retrieved and pregnancy is nearly a reflection of the pattern of the relationship between the number of oocytes retrieved and the probability of having two good-quality embryos transferred. The patients with the “optimal” number of oocytes were not only younger but also had the highest probability of having two good-quality embryos replaced.

Conclusions

Similarly aged patients have similar pregnancy prospects after fresh embryo transfer when the same number and quality of embryos are replaced, irrespective of their number of oocytes. Selecting the desired number of good-quality embryos for transfer is the key to IVF success. Thus, aiming at retrieving an optimal number of oocytes to maximize IVF outcomes in a fresh cycle could place undue stress on the patients and may not be the best medical decision.

Single thawed euploid embryo transfer improves IVF pregnancy, miscarriage, and multiple gestation outcomes and has similar implantation rates as egg donation

PURPOSE

The objective of our study was to determine if trophectoderm biopsy, vitrification, array-comparative genomic hybridization and single thawed euploid embryo transfer (STEET) can reduce multiple gestations and yield high pregnancy and low miscarriage rates.

METHODS

We performed a retrospective observational study comparing single thawed euploid embryo to routine age matched in vitro fertilization (IVF) patients that underwent blastocyst transfer from 2008 to 2011 and to our best prognosis group donor oocyte recipients (Donor). Our main outcome measures were implantation rate, clinical pregnancy rate, spontaneous abortion rate and multiple gestation rate.

RESULTS

The STEET group had a significantly higher implantation rate (58 %, 53/91) than the routine IVF group (39 %, 237/613) while the Donor group (57 %, 387/684) had a similar implantation rate. The clinical pregnancy rates were not statistically different between the STEET and IVF groups. However, the multiple gestation rate was significantly lower in the STEET group (STEET 2 % versus IVF 34 %, Donor 47 %).

CONCLUSIONS

STEET results in a high pregnancy rate, low multiple gestation rate and miscarriage rates. Despite the older age of STEET patients and transfer of twice as many embryos, the implantation rate for STEET was indistinguishable from that for egg donation. STEET offers an improvement to IVF, lowering risks without compromising pregnancy rate.

Molecular origin of female meiotic aneuploidies

Chromosome aneuploidy is a major cause of pregnancy loss, abnormal pregnancy and live births following both natural conception and in vitro fertilisation (IVF) and increases exponentially with maternal age in the decade preceding the menopause. Molecular genetic analysis has shown that these are predominantly maternal in origin and trisomies most frequently occur through errors in the first meiotic division. Analysis of chromosome copy number in the three products of female meiosis, the first and second polar bodies and the corresponding zygote by microarray comparative genomic hybridisation (array CGH), in women of advanced maternal age undergoing IVF, has recently revealed a pattern of frequent multiple meiotic errors, caused by premature predivision of sister chromatids in meiosis I and a high incidence of errors in meiosis II. This pattern is similar to those observed in various mouse models which implicate the gradual depletion of cohesins, which are essential for cohesion of sister chromatids, as the primary cause of age related aneuploidy in female meiosis. However, defects in other aspects of meiosis including the formation and stabilisation of chiasmata and the spindle assembly checkpoint (SAC) may also contribute. The challenge remains to explain the molecular basis of 'physiological' rather than 'chronological' female ageing and the contribution of multifactorial causes from the fetal to adult ovary. This article is part of a Special Issue entitled: Molecular Genetics of Human Reproductive Failure.

Array comparative genomic hybridization screening in IVF significantly reduces number of embryos available for cryopreservation

Objective

During IVF, non-transferred embryos are usually selected for cryopreservation on the basis of morphological criteria. This investigation evaluated an application for array comparative genomic hybridization (aCGH) in assessment of surplus embryos prior to cryopreservation.

Methods

First-time IVF patients undergoing elective single embryo transfer and having at least one extra non-transferred embryo suitable for cryopreservation were offered enrollment in the study. Patients were randomized into two groups: Patients in group A (n=55) had embryos assessed first by morphology and then by aCGH, performed on cells obtained from trophectoderm biopsy on post-fertilization day 5. Only euploid embryos were designated for cryopreservation. Patients in group B (n=48) had embryos assessed by morphology alone, with only good morphology embryos considered suitable for cryopreservation.

Results

Among biopsied embryos in group A (n=425), euploidy was confirmed in 226 (53.1%). After fresh single embryo transfer, 64 (28.3%) surplus euploid embryos were cryopreserved for 51 patients (92.7%). In group B, 389 good morphology blastocysts were identified and a single top quality blastocyst was selected for fresh transfer. All group B patients (48/48) had at least one blastocyst remaining for cryopreservation. A total of 157 (40.4%) blastocysts were frozen in this group, a significantly larger proportion than was cryopreserved in group A (p=0.017, by chi-squared analysis).

Conclusion

While aCGH and subsequent frozen embryo transfer are currently used to screen embryos, this is the first investigation to quantify the impact of aCGH specifically on embryo cryopreservation. Incorporation of aCGH screening significantly reduced the total number of cryopreserved blastocysts compared to when suitability for freezing was determined by morphology only. IVF patients should be counseled that the benefits of aCGH screening will likely come at the cost of sharply limiting the number of surplus embryos available for cryopreservation.

Human aneuploidy: mechanisms and new insights into an age-old problem

Trisomic and monosomic (aneuploid) embryos account for at least 10% of human pregnancies and, for women nearing the end of their reproductive lifespan, the incidence may exceed 50%. The errors that lead to aneuploidy almost always occur in the oocyte but, despite intensive investigation, the underlying molecular basis has remained elusive. Recent studies of humans and model organisms have shed new light on the complexity of meiotic defects, providing evidence that the age-related increase in errors in the human female is not attributable to a single factor but to an interplay between unique features of oogenesis and a host of endogenous and exogenous factors.

Selection of single blastocysts for fresh transfer via standard morphology assessment alone and with array CGH for good prognosis IVF patients: results from a randomized pilot study

BACKGROUND

Single embryo transfer (SET) remains underutilized as a strategy to reduce multiple gestation risk in IVF, and its overall lower pregnancy rate underscores the need for improved techniques to select one embryo for fresh transfer. This study explored use of comprehensive chromosomal screening by array CGH (aCGH) to provide this advantage and improve pregnancy rate from SET.

METHODS

First-time IVF patients with a good prognosis (age <35, no prior miscarriage) and normal karyotype seeking elective SET were prospectively randomized into two groups: In Group A, embryos were selected on the basis of morphology and comprehensive chromosomal screening via aCGH (from d5 trophectoderm biopsy) while Group B embryos were assessed by morphology only. All patients had a single fresh blastocyst transferred on d6. Laboratory parameters and clinical pregnancy rates were compared between the two groups.

RESULTS

For patients in Group A (n = 55), 425 blastocysts were biopsied and analyzed via aCGH (7.7 blastocysts/patient). Aneuploidy was detected in 191/425 (44.9%) of blastocysts in this group. For patients in Group B (n = 48), 389 blastocysts were microscopically examined (8.1 blastocysts/patient). Clinical pregnancy rate was significantly higher in the morphology + aCGH group compared to the morphology-only group (70.9 and 45.8%, respectively; p = 0.017); ongoing pregnancy rate for Groups A and B were 69.1 vs. 41.7%, respectively (p = 0.009). There were no twin pregnancies.

CONCLUSION

Although aCGH followed by frozen embryo transfer has been used to screen at risk embryos (e.g., known parental chromosomal translocation or history of recurrent pregnancy loss), this is the first description of aCGH fully integrated with a clinical IVF program to select single blastocysts for fresh SET in good prognosis patients. The observed aneuploidy rate (44.9%) among biopsied blastocysts highlights the inherent imprecision of SET when conventional morphology is used alone. Embryos randomized to the aCGH group implanted with greater efficiency, resulted in clinical pregnancy more often, and yielded a lower miscarriage rate than those selected without aCGH. Additional studies are needed to verify our pilot data and confirm a role for on-site, rapid aCGH for IVF patients contemplating fresh SET.

Intra-age, intercenter, and intercycle differences in chromosome abnormalities in oocytes

OBJECTIVE

To determine the extent of intra-age and intercycle variations in the frequency of first polar body aneuploidy in two consecutive cycles of oocyte retrieval undertaken by the same patient within 1 year.

DESIGN

Retrospective study.

SETTING

Fertility centers.

PATIENT(S)

Infertile couples undergoing IVF.

INTERVENTION(S)

Patients underwent two consecutive cycles of preimplantation genetic screening through first polar body biopsy within 1 year.

MAIN OUTCOME MEASURE(S)

Meiosis I aneuploidy.

RESULT(S)

A total of 226 patients underwent 452 cycles of preimplantation genetic screening. Differences within age groups were wide, with 0-100% of oocytes being chromosomally normal in all age groups. Euploidy rates between centers were significantly different (48% vs. 25%). Intercycle differences for the same patient were also wide (0-100%), but with 68.5% of patients having less than ±2 euploid eggs of difference between cycles.

CONCLUSION(S)

Although euploidy rate decreased on average with advancing maternal age, the high intra-age and intercenter variation in oocyte chromosome abnormalities emphasize the difficulty in estimating how many euploid oocytes a specific woman will have. This may have repercussions for fertility preservation where a defined number of eggs are currently frozen just based on maternal age.

Chromosomal disorders and male infertility

Infertility in humans is surprisingly common occurring in approximately 15% of the population wishing to start a family. Despite this, the molecular and genetic factors underlying the cause of infertility remain largely undiscovered. Nevertheless, more and more genetic factors associated with infertility are being identified. This review will focus on our current understanding of the chromosomal basis of male infertility specifically: chromosomal aneuploidy, structural and numerical karyotype abnormalities and Y chromosomal microdeletions. Chromosomal aneuploidy is the leading cause of pregnancy loss and developmental disabilities in humans. Aneuploidy is predominantly maternal in origin, but concerns have been raised regarding the safety of intracytoplasmic sperm injection as infertile men have significantly higher levels of sperm aneuploidy compared to their fertile counterparts. Males with numerical or structural karyotype abnormalities are also at an increased risk of producing aneuploid sperm. Our current understanding of how sperm aneuploidy translates to embryo aneuploidy will be reviewed, as well as the application of preimplantation genetic diagnosis (PGD) in such cases. Clinical recommendations where possible will be made, as well as discussion of the use of emerging array technology in PGD and its potential applications in male infertility.

Origins and rates of aneuploidy in human blastomeres

OBJECTIVE

To characterize chromosomal error types and parental origin of aneuploidy in cleavage-stage embryos using an informatics-based technique that enables the elucidation of aneuploidy-causing mechanisms.

DESIGN

Analysis of blastomeres biopsied from cleavage-stage embryos for preimplantation genetic screening during IVF.

SETTING

Laboratory.

PATIENT(S)

Couples undergoing IVF treatment.

INTERVENTION(S)

Two hundred seventy-four blastomeres were subjected to array-based genotyping and informatics-based techniques to characterize chromosomal error types and parental origin of aneuploidy across all 24 chromosomes.

MAIN OUTCOME MEASURE(S)

Chromosomal error types (monosomy vs. trisomy; mitotic vs. meiotic) and parental origin (maternal vs. paternal).

RESULT(S)

The rate of maternal meiotic trisomy rose significantly with age, whereas other types of trisomy showed no correlation with age. Trisomies were mostly maternal in origin, whereas paternal and maternal monosomies were roughly equal in frequency. No examples of paternal meiotic trisomy were observed. Segmental error rates were found to be independent of maternal age.

CONCLUSION(S)

All types of aneuploidy that rose with increasing maternal age can be attributed to disjunction errors during meiosis of the oocyte. Chromosome gains were predominantly maternal in origin and occurred during meiosis, whereas chromosome losses were not biased in terms of parental origin of the chromosome. The ability to determine the parental origin for each chromosome, as well as being able to detect whether multiple homologs from a single parent were present, allowed greater insights into the origin of aneuploidy.

Preimplantation genetic screening: does it help or hinder IVF treatment and what is the role of the embryo?

Despite an ongoing debate over its efficacy, preimplantation genetic screening (PGS) is increasingly being used to detect numerical chromosomal abnormalities in embryos to improve implantation rates after IVF. The main indications for the use of PGS in IVF treatments include advanced maternal age, repeated implantation failure, and recurrent pregnancy loss. The success of PGS is highly dependent on technical competence, embryo culture quality, and the presence of mosaicism in preimplantation embryos. Today, cleavage stage biopsy is the most commonly used method for screening preimplantation embryos for aneuploidy. However, blastocyst biopsy is rapidly becoming the more preferred method due to a decreased likelihood of mosaicism and an increase in the amount of DNA available for testing. Instead of using 9 to 12 chromosome FISH, a 24 chromosome detection by aCGH or SNP microarray will be used. Thus, it is advised that before attempting to perform PGS and expecting any benefit, extended embryo culture towards day 5/6 should be established and proven and the clinical staff should demonstrate competence with routine competency assessments. A properly designed randomized control trial is needed to test the potential benefits of these new developments.

PGS-FISH in reproductive medicine and perspective directions for improvement: a systematic review

INTRODUCTION

Embryo selection can be carried out via morphological criteria or by using genetic studies based on Preimplantation Genetic Screening. In the present study, we evaluate the clinical validity of Preimplantation Genetic Screening with fluorescence in situ hybridization (PGS-FISH) compared with morphological embryo criteria.

MATERIAL AND METHODS

A systematic review was made of the bibliography, with the following goals: firstly, to determine the prevalence of embryo chromosome alteration in clinical situations in which the PGS-FISH technique has been used; secondly, to calculate the statistics of diagnostic efficiency (negative Likelihood Ratio), using 2 × 2 tables, derived from PGS-FISH. The results obtained were compared with those obtained from embryo morphology. We calculated the probability of transferring at least one chromosome-normal embryo when it was selected using either morphological criteria or PGS-FISH, and considered what diagnostic performance should be expected of an embryo selection test with respect to achieving greater clinical validity than that obtained from embryo morphology.

RESULTS

After an embryo morphology selection that produced a negative result (normal morphology), the likelihood of embryo aneuploidies was found to range from a pre-test value of 65% (prevalence of embryo chromosome alteration registered in all the study groups) to a post-test value of 55% (Confidence interval: 50-61), while after PGS-FISH with a negative result (euploid), the post-test probability was 42% (Confidence interval: 35-49) (p < 0.05). The probability of transferring at least one euploid embryo was the same whether 3 embryos were selected according to morphological criteria or whether 2, selected by PGS-FISH, were transferred. Any embryo selection test, if it is to provide greater clinical validity than embryo morphology, must present a LR-value of 0.40 (Confidence interval: 0.32-0.51) in single embryo transfer, and 0.06 (CI: 0.05-0.07) in double embryo transfer.

DISCUSSION

With currently available technology, and taking into account the number of embryos to be transferred, the clinical validity of PGS-FISH, although superior to that of morphological criteria, does not appear to be clinically relevant.

The Istanbul consensus workshop on embryo assessment: proceedings of an expert meeting

BACKGROUND

Many variations in oocyte and embryo grading make inter-laboratory comparisons extremely difficult. This paper reports the proceedings of an international consensus meeting on oocyte and embryo morphology assessment.

METHODS

Background presentations about current practice were given.

RESULTS

The expert panel developed a set of consensus points to define the minimum criteria for oocyte and embryo morphology assessment.

CONCLUSIONS

It is expected that the definition of common terminology and standardization of laboratory practice related to embryo morphology assessment will result in more effective comparisons of treatment outcomes. This document is intended to be referenced as a global consensus to allow standardized reporting of the minimum data set required for the accurate description of embryo development.

Derivation of two new human embryonic stem cell lines from nonviable human embryos

We report the derivation and characterization of two new human embryonic stem cells (hESC) lines (CU1 and CU2) from embryos with an irreversible loss of integrated organismic function. In addition, we analyzed retrospective data of morphological progression from embryonic day (ED) 5 to ED6 for 2480 embryos not suitable for clinical use to assess grading criteria indicative of loss of viability on ED5. Our analysis indicated that a large proportion of in vitro fertilization (IVF) embryos not suitable for clinical use could be used for hESC derivation. Based on these combined findings, we propose that criteria commonly used in IVF clinics to determine optimal embryos for uterine transfer can be employed to predict the potential for hESC derivation from poor quality embryos without the destruction of vital human embryos.

Istanbul consensus workshop on embryo assessment: proceedings of an expert meeting

This paper reports the proceedings of an international consensus meeting on oocyte and embryo morphology assessment. Following background presentations about current practice, the expert panel developed a set of consensus points to define the minimum criteria for oocyte and embryo morphology assessment. It is expected that the definition of common terminology and standardization of laboratory practice related to embryo morphology assessment will result in more effective comparisons of treatment outcomes. This document is intended to be referenced as a global consensus to allow standardized reporting of the minimum dataset required for the accurate description of embryo development. This paper reports the proceedings and outcomes of an international consensus meeting on human oocyte and embryo morphology assessment. An expert panel developed a series of consensus points to define the minimum criteria for such assessments. The definition of common terminology, and standardization of laboratory practices related to these morphological assessments, will permit more effective comparisons of treatment outcomes around the world. This report is intended to be referenced as a global consensus to allow standardized reporting of the minimum descriptive criteria required for routine clinical evaluations of human embryo development in vitro.

Comparison of three embryo culture methods for derivation of human embryonic stem cells from discarded embryos

Human embryonic stem cells (hESC) are self-renewing and pluripotent cells that hold great promise. Our objective was to compare the effect of three different embryo culture methods for derivation of human embryonic stem cells from discarded embryos. A prospective and randomized trial was conducted using 381 discarded human embryos at days 2-3 postfertilization in Beijing Obstetrics and Gynecology Hospital IVF center. After removal of the zona pellucida, discarded human embryos were cultured by three different methods as multiple embryo aggregates, single embryo, and blastomeres. Outgrowth of embryos and hESC derivation were observed. The outgrowth rate of embryos cultured as multiple embryo aggregates was higher than that of those cultured as single embryos or blastomeres (p < 0.05). Three propagating hESC lines were derived from poor quality day 2-3 postfertilization nonblastocyst embryos cultured as multiple embryo aggregates. Derived hESC lines expressed hESC-specific markers of pluripotency and had normal diploid karyotype. The cells were able to form derivatives of all three germ layers in vivo as teratomas. Our results demonstrate that culturing these discarded embryos as multiple embryo aggregates was more profitable for outgrowth and derivation of ESC line than culturing these as single embryo or blastomeres.

Female meiosis: coming unglued with age

Chromosome abnormalities in humans are strikingly associated with increasing maternal age. Studies in mice implicate loss of chromosome cohesion as an important cause of age-related meiotic errors in the oocyte.

First successful pregnancy following PGD for chromosome translocation on embryos generated from in-vitro matured oocytes: a case report

As far as is known, this is the first report of a successful pregnancy outcome following preimplantation genetic diagnosis for a chromosome translocation in embryos generated from in-vitro matured oocytes. A couple presented to the study clinic where the female partner was a carrier of the reciprocal chromosome translocation 46,XX,t(1;20)(p36.1;p12.2) with three consecutive pregnancy terminations due to either fetal abnormality or unbalanced translocation products detected in the conceptus. Under routine ultrasound investigation she was diagnosed with polycystic ovaries. The patient underwent an in-vitro maturation/preimplantation genetic diagnosis cycle where the immature oocytes were matured in vitro and fertilized by intracytoplasmic sperm injection. Day-3 embryos were screened for the chromosome abnormality by fluorescent in-situ hybridization. A single embryo diagnosed as chromosomally normal/balanced was transferred on day 5 and resulted in the birth of a healthy child.

Testicular sperm from patients with obstructive and nonobstructive azoospermia: aneuploidy risk and reproductive prognosis using testicular sperm from fertile donors as control samples

OBJECTIVE

To establish a baseline incidence of chromosomal abnormalities in testicular sperm of fertile men and to determine the best control sample for comparisons with azoospermic males to estimate their reproductive prognosis.

DESIGN

Prospective study.

SETTING

Infertility clinic.

PATIENT(S)

Sixteen obstructive azoospermic (OA) and 19 nonobstructive azoospermic patients (NOA). Control samples were ejaculated sperm from ten fertile donors and testicular sperm from ten other fertile donors.

INTERVENTION(S)

Fluorescence in situ hybridization (FISH) in sperm.

MAIN OUTCOME MEASURE(S)

Sperm numerical abnormalities for chromosomes 13, 18, 21, X, and Y; ongoing implantation and pregnancy rates in intracytoplasmic sperm injection (ICSI) cycles.

RESULT(S)

In control samples, testicular sperm showed higher incidences of diploidy (0.27% vs. 0.10%) and disomy for chromosomes 13 (0.16% vs. 0.07%), 21 (0.25% vs. 0.12%), and sex chromosomes (0.34% vs. 0.21%) than ejaculated sperm. Comparisons with ejaculated control samples showed 12.5% OA and 68.4% NOA patients having significantly higher incidence of sperm chromosomal abnormalities. Compared with testicular control subjects, fewer OA (6.3%) and NOA (42.1%) patients had chromosomally abnormal sperm. NOA patients had lower ongoing implantation and pregnancy rates than OA patients, particularly those with abnormal FISH compared with testicular control samples.

CONCLUSION(S)

Sperm FISH analysis using testicular sperm control samples better identifies NOA patients with a lower likelihood of reproductive success.

Embryo and uterine influences on IVF outcomes: an analysis of a UK multi-centre cohort

BACKGROUND

In order to optimize IVF strategies, particularly with the use of single embryo transfer, good predictive models are required. Here, we develop a model to allow such prediction, and the structure of the models point to more general conclusions about the mode of action of prognostic factors.

METHODS

Anonymized data from consecutive embryo transfers in five IVF centres in the UK for the 2000-2005 period were extracted and the morphological grade based on common scoring criteria was included. There were 16 096 (12 487 fresh and 3609 frozen) transfers, for 8775 couples, available for analysis. Live birth data were fitted to a model with separate sub-models for embryo and recipient effects [the 'Embryo-Uterus' (EU) model]. All covariates were included, with sub-model selection using Akaike's information criterion.

RESULTS

Age, number of embryos created, attempt number, previous history of pregnancy, duration of infertility, day of transfer and tubal diagnosis were all identified as significant prognostic factors, along with embryo grade and growth rate. Frozen transfers were substantially less likely to lead to a live birth with odds ratios of 1/3 to 1/2 compared with fresh transfers, with no evidence of differential loss for any particular patient group. Age acts predominantly through the embryo component with only a weak effect on the uterus. The embryo number, attempt number, previous pregnancies and duration of infertility act predominantly through the uterine environment. Both sub-models show significant heterogeneity between centres.

CONCLUSIONS

The EU modelling framework has generated a model for predicting outcomes of embryo-transfer procedures, subject to the limitations of routinely collected data. With this large data set, the model allows identification of factors that act specifically on embryo viability or maternal receptivity. Variability in the two components between centres with similar overall outcomes suggests scope for further optimization of IVF treatment.

Validation of microarray comparative genomic hybridization for comprehensive chromosome analysis of embryos

OBJECTIVE

To validate and determine the best array-comparative genomic hybridization (aCGH; array-CGH) protocols for preimplantation genetic screening (PGS).

DESIGN

Embryos had one cell removed as a biopsy specimen and analyzed by one of two array-CGH protocols. Abnormal embryos were reanalyzed by fluorescence in situ hybridization (FISH).

SETTING

Reference laboratory.

PATIENT(S)

Patients donating embryos or undergoing PGS.

INTERVENTION(S)

Embryo biopsy, array-CGH, FISH reanalysis.

MAIN OUTCOME MEASURE(S)

Diagnosis, no result rate and error rate.

RESULT(S)

Method one produced 11.2% of embryos with no results and a 9.1% error rate compared with 3% and 1.9% for method two, respectively. Thereafter, only method two was used clinically. The aneuploidy rate for cleavage-stage embryos was 63.2%, significantly increasing with maternal age. The chromosomes most involved in aneuploidy were 16, 22, 21, and 15. We report the first live births after array-CGH combined with single blastomere biopsy.

CONCLUSION(S)

Array-CGH is proved to be highly robust (2.9% no results) and specific (1.9% error rate) when applied to rapid (24-hour) analysis of single cells biopsied from cleavage-stage embryos. This comprehensive chromosome analysis technique is the first to be validated by reanalyzing the same embryos with another technique (e.g., FISH). Unlike some alternative techniques for comprehensive chromosome screening, array-CGH does not require prior testing of parental DNA and thus advance planning and careful scheduling are unnecessary.

The utility of embryo banking in order to increase the number of embryos available for preimplantation genetic screening in advanced maternal age patients

PURPOSE

to determine if embryo banking with PGS is more optimal than proceeding with PGS regardless of embryo number.

METHODS

patients were divided into 2 groups, group 1 were those that banked embryos and proceeded through another round of IVF prior to PGS, and group 2 underwent PGS regardless of embryo number. Group 2 was divided into group 2A (patients with >10 embryos) and group 2B (patients who had <10 embryos).

RESULTS

there was no difference in embryos biopsied, normal embryos, number transferred, and pregnancy rate between group 1 and 2. A significant number of patients did not have a transfer in group 2B (6/11) compared to group 1 (3/19) (P = 0.0419). There was no significance between pregnancy rates per transfer between group 1 (6/16) and group 2B (2/5).

CONCLUSION

our data suggests that banking will increase the odds of going to transfer but there was no increase in pregnancy rates.