Preimplantation genetic testing for aneuploidies (abnormal number of chromosomes) in in vitro fertilisation.

BACKGROUND: In in vitro fertilisation (IVF) with or without intracytoplasmic sperm injection (ICSI), selection of the most competent embryo(s) for transfer is based on morphological criteria. However, many women do not achieve a pregnancy even after 'good quality' embryo transfer. One of the presumed causes is that such morphologically normal embryos have an abnormal number of chromosomes (aneuploidies). Preimplantation genetic testing for aneuploidies (PGT-A), formerly known as preimplantation genetic screening (PGS), was therefore developed as an alternative method to select embryos for transfer in IVF. In PGT-A, the polar body or one or a few cells of the embryo are obtained by biopsy and tested. Only polar bodies and embryos that show a normal number of chromosomes are transferred. The first generation of PGT-A, using cleavage-stage biopsy and fluorescence in situ hybridisation (FISH) for the genetic analysis, was demonstrated to be ineffective in improving live birth rates. Since then, new PGT-A methodologies have been developed that perform the biopsy procedure at other stages of development and use different methods for genetic analysis. Whether or not PGT-A improves IVF outcomes and is beneficial to patients has remained controversial. OBJECTIVES: To evaluate the effectiveness and safety of PGT-A in women undergoing an IVF treatment. SEARCH METHODS: We searched the Cochrane Gynaecology and Fertility (CGF) Group Trials Register, CENTRAL, MEDLINE, Embase, PsycINFO, CINAHL, and two trials registers in September 2019 and checked the references of appropriate papers. SELECTION CRITERIA: All randomised controlled trials (RCTs) reporting data on clinical outcomes in participants undergoing IVF with PGT-A versus IVF without PGT-A were eligible for inclusion. DATA COLLECTION AND ANALYSIS: Two review authors independently selected studies for inclusion, assessed risk of bias, and extracted study data. The primary outcome was the cumulative live birth rate (cLBR). Secondary outcomes were live birth rate (LBR) after the first embryo transfer, miscarriage rate, ongoing pregnancy rate, clinical pregnancy rate, multiple pregnancy rate, proportion of women reaching an embryo transfer, and mean number of embryos per transfer. MAIN RESULTS: We included 13 trials involving 2794 women. The quality of the evidence ranged from low to moderate. The main limitations were imprecision, inconsistency, and risk of publication bias. IVF with PGT-A versus IVF without PGT-A with the use of genome-wide analyses Polar body biopsy One trial used polar body biopsy with array comparative genomic hybridisation (aCGH). It is uncertain whether the addition of PGT-A by polar body biopsy increases the cLBR compared to IVF without PGT-A (odds ratio (OR) 1.05, 95% confidence interval (CI) 0.66 to 1.66, 1 RCT, N = 396, low-quality evidence). The evidence suggests that for the observed cLBR of 24% in the control group, the chance of live birth following the results of one IVF cycle with PGT-A is between 17% and 34%. It is uncertain whether the LBR after the first embryo transfer improves with PGT-A by polar body biopsy (OR 1.10, 95% CI 0.68 to 1.79, 1 RCT, N = 396, low-quality evidence). PGT-A with polar body biopsy may reduce miscarriage rate (OR 0.45, 95% CI 0.23 to 0.88, 1 RCT, N = 396, low-quality evidence). No data on ongoing pregnancy rate were available. The effect of PGT-A by polar body biopsy on improving clinical pregnancy rate is uncertain (OR 0.77, 95% CI 0.50 to 1.16, 1 RCT, N = 396, low-quality evidence). Blastocyst stage biopsy One trial used blastocyst stage biopsy with next-generation sequencing. It is uncertain whether IVF with the addition of PGT-A by blastocyst stage biopsy increases cLBR compared to IVF without PGT-A, since no data were available. It is uncertain if LBR after the first embryo transfer improves with PGT-A with blastocyst stage biopsy (OR 0.93, 95% CI 0.69 to 1.27, 1 RCT, N = 661, low-quality evidence). It is uncertain whether PGT-A with blastocyst stage biopsy reduces miscarriage rate (OR 0.89, 95% CI 0.52 to 1.54, 1 RCT, N = 661, low-quality evidence). No data on ongoing pregnancy rate or clinical pregnancy rate were available. IVF with PGT-A versus IVF without PGT-A with the use of FISH for the genetic analysis Eleven trials were included in this comparison. It is uncertain whether IVF with addition of PGT-A increases cLBR (OR 0.59, 95% CI 0.35 to 1.01, 1 RCT, N = 408, low-quality evidence). The evidence suggests that for the observed average cLBR of 29% in the control group, the chance of live birth following the results of one IVF cycle with PGT-A is between 12% and 29%. PGT-A performed with FISH probably reduces live births after the first transfer compared to the control group (OR 0.62, 95% CI 0.43 to 0.91, 10 RCTs, N = 1680, I² = 54%, moderate-quality evidence). The evidence suggests that for the observed average LBR per first transfer of 31% in the control group, the chance of live birth after the first embryo transfer with PGT-A is between 16% and 29%. There is probably little or no difference in miscarriage rate between PGT-A and the control group (OR 1.03, 95%, CI 0.75 to 1.41; 10 RCTs, N = 1680, I² = 16%; moderate-quality evidence). The addition of PGT-A may reduce ongoing pregnancy rate (OR 0.68, 95% CI 0.51 to 0.90, 5 RCTs, N = 1121, I² = 60%, low-quality evidence) and probably reduces clinical pregnancies (OR 0.60, 95% CI 0.45 to 0.81, 5 RCTs, N = 1131; I² = 0%, moderate-quality evidence). AUTHORS' CONCLUSIONS: There is insufficient good-quality evidence of a difference in cumulative live birth rate, live birth rate after the first embryo transfer, or miscarriage rate between IVF with and IVF without PGT-A as currently performed. No data were available on ongoing pregnancy rates. The effect of PGT-A on clinical pregnancy rate is uncertain. Women need to be aware that it is uncertain whether PGT-A with the use of genome-wide analyses is an effective addition to IVF, especially in view of the invasiveness and costs involved in PGT-A. PGT-A using FISH for the genetic analysis is probably harmful. The currently available evidence is insufficient to support PGT-A in routine clinical practice.

Identification novel mutations in TUBB8 in female infertility and a novel phenotype of large polar body in oocytes with TUBB8 mutations.

PURPOSE: We aimed to identify novel variants in TUBB8 and corresponding new abnormal phenotypes in oocytes/fertilization/ embryonic development responsible for female infertility. METHODS: Sanger sequencing of TUBB8 was performed in infertile women with abnormalities in oocyte maturation or embryonic development. The effects of the variants were evaluated in patients' oocytes by morphological observations and immunofluorescence. RESULTS: We identified 34 novel variants of TUBB8 in 51 patients who were diagnosed with abnormalities in oocyte maturation or early embryonic development. We found a novel phenotype in which large polar bodies were present in three independent patients possibly associated with a recurrent variant. Moreover, we identified a novel type of TUBB8 variant consisting of an in-frame deletion-insertion, which has not been previously reported. CONCLUSIONS: Our present study identified 34 novel variants in TUBB8 in 51 patients. These patients show oocyte maturation arrest, oocytes with large polar body, fertilization failure, early embryonic arrest or embryonic implantation failure. These results expand the kinds of variants and phenotypic spectrum of TUBB8 variants with regard to female infertility.

Human oocytes harboring damaged DNA can complete meiosis I.

OBJECTIVE: To determine whether human oocytes possess a checkpoint to prevent completion of meiosis I when DNA is damaged. DESIGN: DNA damage is considered a major threat to the establishment of healthy eggs and embryos. Recent studies found that mouse oocytes with damaged DNA can resume meiosis and undergo germinal vesicle breakdown (GVBD), but then arrest in metaphase of meiosis I in a process involving spindle assembly checkpoint (SAC) signaling. Such a mechanism could help prevent the generation of metaphase II (MII) eggs with damaged DNA. Here, we compared the impact of DNA-damaging agents with nondamaged control samples in mouse and human oocytes. SETTING: University-affiliated clinic and research center. PATIENT(S): Patients undergoing ICSI cycles donated GV-stage oocytes after informed consent; 149 human oocytes were collected over 2 years (from 50 patients aged 27-44 years). INTERVENTIONS(S): Mice and human oocytes were treated with DNA-damaging drugs. MAIN OUTCOME MEASURE(S): Oocytes were monitored to evaluate GVBD and polar body extrusion (PBE), in addition to DNA damage assessment with the use of γH2AX antibodies and confocal microscopy. RESULT(S): Whereas DNA damage in mouse oocytes delays or prevents oocyte maturation, most human oocytes harboring experimentally induced DNA damage progress through meiosis I and subsequently form an MII egg, revealing the absence of a DNA damage-induced SAC response. Analysis of the resulting MII eggs revealed damaged DNA and chaotic spindle apparatus, despite the oocyte appearing morphologically normal. CONCLUSION(S): Our data indicate that experimentally induced DNA damage does not prevent PBE in human oocytes and can persist in morphologically normal looking MII eggs.

Vitamin C protects against defects induced by juglone during porcine oocyte maturation.

Juglone, a naphthoquinone isolated from many species of the Juglandaceae family, has been used in traditional Chinese medicine for centuries because of its antiviral, antibacterial, and antitumor activities. However, the toxicity of juglone has also been demonstrated. Here, we used porcine oocytes as a model to explore the effects of juglone on oocyte maturation and studied the impact of vitamin C (VC) administration on juglone exposure-induced meiosis defects. Exposure to juglone significantly restricted cumulus cell expansion and decreased the first polar body extrusion. In addition, juglone exposure disturbed spindle organization, actin assembly, and the distribution of mitochondria during oocyte meiosis, while the acetylation level of α-tubulin was also reduced. These defects were all ameliorated by VC administration. Our findings indicate that juglone exposure induced meiotic failure in porcine oocytes, while VC protected against these defects during porcine oocyte maturation by ameliorating the organization of the cytoskeleton and mitochondrial distribution.

Impact of polar body biopsy on embryo morphokinetics-back to the roots in preimplantation genetic testing?

PURPOSE: Polar body biopsy (PBB) is a common technique in preimplantation genetic testing (PGT) to assess the chromosomal status of the oocyte. Numerous studies have been implemented to investigate the impact of biopsies on embryo development; however, information on embryo morphokinetics is still lacking. Hence, we investigated the impact of PBB on morphokinetic parameters in early embryo development. METHODS: Four hundred four embryos (202 PBB, 202 control) were retrospectively analyzed. Patients were stimulated with a gonadotropin-releasing hormone antagonist ovarian hyperstimulation protocol. After fertilization check, embryos were incubated in a time-lapse incubator. The groups were matched for maternal age at time of oocyte retrieval. RESULTS: Mean group times for reaching specific developmental time points showed no significant difference comparing embryos with PBB conducted and without. Likewise, further subdivision of the PBB group in euploid and aneuploid embryos revealed no differences in the early embryo morphokinetic development compared to the control group. Aneuploidy testing revealed a high prevalence of chromosomal aberrations for chromosomes 21, 4, 16, and 19. CONCLUSIONS: In conclusion, PBB does not impact the morphokinetic parameters of the embryo development. PBB can be safely applied without the risk of impairing the reproductive potential of the embryo and can be highly recommended as safe and practicable PGT approach, especially in countries with prevailing restrictions regarding PGT analysis.

Toxic effects and possible mechanisms of hydrogen sulfide and/or ammonia on porcine oocyte maturation in vitro.

Previous studies suggest that hydrogen sulfide (H2S) and ammonia (NH3) are two major air pollutants which can cause damage to porcine health. However, the mechanisms underlying toxic effects of these compounds on porcine oocyte maturation are not clear. To clarify the mechanism, we evaluated the oocyte quality by detecting some events during oocytes maturation. In our study, porcine oocytes were cultured with different concentrations of Na2S and/or NH4Cl in vitro and the rate of the first polar body extrusion decreased significantly. Also, actin filament was seriously disrupted to damage the cytoskeleton which resulted in reduced rate of oocyte maturation. We explored the reactive oxygen species (ROS) generation and found that the ROS level was increased significantly after Na2S treatment but not after NH4Cl treatment. Moreover, early stage apoptosis rate was significantly increased and autophagy protein LC3 B expression level was higher in oocytes treated with Na2S and/or NH4Cl, which might be caused by ROS elevation. Additionally, exposure to Na2S and/or NH4Cl also caused ROS generation and early apoptosis in cumulus cells, which might further affect oocyte maturation in vitro. In summary, our data suggested that exposure to H2S and/or NH3 decreased porcine oocyte maturation in vitro, which might be caused by actin disruption, ROS generation, early apoptosis and autophagy.

Bisphenol AF negatively affects oocyte maturation of mouse in vitro through increasing oxidative stress and DNA damage.

Bisphenol AF (BPAF) is commonly used in industry production as a substitute for Bisphenol A (BPA). Many studies showed that BPAF negatively affect some physiological processes in humans and animals. However, the effects of BPAF on oocyte maturation and its possible mechanisms are sparsely understood. In the present study, we found that 100 µM BPAF exposure affect oocyte maturation with a decreased first polar body extrusion (PBE) rate. Immunofluorescence study displayed that BPAF exposure disrupt the spindle morphology through affecting the function of microtubule organizing centers (MTOCs), which was confirmed by the dysfunction of γ-tubulin and phosphorylated mitogen-activated protein kinase (p-MAPK). As shown by reactive oxygen species (ROS) accumulation, BPAF exposure also induced oxidative stress. Moreover, DNA damage was significantly increased after BPAF exposure, which may be caused by oxidative stress. In addition, histone modification statuses were changed after BPAF exposure, as shown by western blot with decreased expression of H3K9me3 and H3K27ac. Collectively, our current work demonstrated the possibility of BPAF to negatively impact female fertility and revealed the mechanisms that BPAF disrupted mouse oocyte maturation by affecting cytoskeletal dynamics, inducing oxidative stress, increasing DNA damage, and changing the status of epigenetic modifications. This finding can help develop the potential therapies to alleviate oxidative damage to preserve fertility in people who are often exposed to BPAF environment.

Polar body transfer restores the developmental potential of oocytes to blastocyst stage in a case of repeated embryo fragmentation.

PURPOSE: We aimed to determine the developmental potential of human reconstructed oocytes after polar body genome transfer (PBT) and to report the case of a woman with multiple cycles of severe embryo fragmentation. METHODS: Fresh and cryopreserved first polar bodies (PB1s) were transferred to enucleated metaphase II oocytes (PB1T), while fresh PB2s were removed from fertilized oocytes and used instead of the female pronucleus in donor zygotes. Reconstructed oocytes underwent intracytoplasmic sperm injection (ICSI) and were cultured to blastocyst. Biopsied trophectoderm cells of PBT-derived blastocysts were screened for chromosomes by next-generation sequencing (NGS). Then, cryopreserved PB1T was carried out in one woman with a history of several cycles of extensive embryo fragmentation, and the blastocysts derived from PB1T were screened for aneuploidy but not transferred to the patient. RESULTS: There were no significant differences in the rates of normal fertilization and blastocyst formation between fresh and cryopreserved PB1T and control oocytes. Of the three fresh and three cryopreserved PB1T-derived blastocysts, two and one blastocysts exhibited normal diploidy respectively. In contrast, 17 PB2 transfers yielded 16 two pronuclei (2PN) zygotes with one normal and one small-sized pronucleus each and no blastocyst formation. In the female patient, 18 oocytes were inseminated by ICSI in the fourth cycle and the PB1s were biopsied. Although the embryos developed from the patient's own oocytes showed severe fragmentation, the oocytes reconstructed after PB1T produced three chromosomally normal blastocysts. CONCLUSIONS: Normal blastocysts can develop from human reconstructed oocytes after PB1T. The application of the first PB transfers may be beneficial to patients with a history of poor embryo development and excessive fragmentation.

Chronic Exposure to Diquat Causes Reproductive Toxicity in Female Mice.

Diquat is a bipyridyl herbicide that has been widely used as a model chemical for in vivo studies of oxidative stress due to its generation of superoxide anions, and cytotoxic effects. There is little information regarding the toxic effects of diquat on the female reproductive system, particularly ovarian function. Thus, we investigated the reproductive toxic effects of diquat on female mice. Chronic exposure to diquat reduced ovary weights, induced ovarian oxidative stress, resulted in granulosa cell apoptosis, and disrupted oocyte developmental competence, as shown by reactive oxygen species (ROS) accumulation, decreased polar body extrusion rates and increased apoptosis-related genes expression. Additionally, after diquat treatment, the numbers of fetal mice and litter sizes were significantly reduced compared to those of control mice. Thus, our results indicated that chronic exposure to diquat induced reproductive toxicity in female mice by promoting the ROS production of gruanousa cells and ooctyes, impairing follicle development, inducing apoptosis, and reducing oocyte quality. In conclusion, our findings indicate that diquat can be used as a potent and efficient chemical for in vivo studies of female reproductive toxicity induced by oxidative stress. Moreover, the findings from this study will further enlarge imitative research investigating the effect of ovarian damage induced by oxidative stress on reproductive performance and possible mechanisms of action in large domestic animals.

Optimal polar bodies angle for higher subsequent embryo viability: a pilot study.

OBJECTIVE: To determine the optimal polar bodies (PB) angle for higher subsequent embryo implantation potential. DESIGN: Prospective study. SETTING: Academic fertility center. PATIENT(S): From January to July 2015, 116 patients were recruited in their first IVF-ET cycles. INTERVENTION(S): At the pronuclear stage, PB angle was measured with the use of E-ruler 1.1. MAIN OUTCOME MEASURE(S): The primary outcome measure was good-quality embryo rate. Secondary measures were clinical pregnancy rate (CPR) and embryo implantation rate (IR). RESULT(S): A total of 1,103 oocytes were retrieved. PB angle was measured in 454 zygotes, and 164 of their subsequent embryos were transferred into the uterus. All-or-none implantation took place in 129 embryos, and 89 patients accepted fresh embryo(s) transfer with known PB angle. By means of receiver operating characteristic analysis, the optimal PB angle for subsequent embryo implantation was 24.25°. Based on this cutoff value, 454 zygotes were divided into two groups: small-angle and large-angle. A higher percentage of small-angle zygotes developed into good-quality embryos (70.97% vs. 58.58%). CPR and IR both decreased progressively from purely small-angle embryos to mixed embryos to purely large-angle embryos (CPR: 72.41% vs. 38.46% vs. 26.47%, respectively; IR: 63.27% vs. 26.92% vs. 16.67%, respectively). CONCLUSION(S): Noninvasive assessment of PB angle is a viable technique for zygote selection and should be included in embryo selection parameters. CLINICAL TRIAL REGISTRATION NUMBER: ChiCTR-OOC-15005882.

Preimplantation genetic testing: polar bodies, blastomeres, trophectoderm cells, or blastocoelic fluid?

OBJECTIVE: To investigate the blastocoelic fluid (BF) for the presence of DNA that could be amplified and analyzed; the extent to which its chromosomal status corresponds to that found in trophectoderm (TE) cells, polar bodies (PBs), or blastomeres; and the identification of segmental abnormalities. DESIGN: Longitudinal cohort study. SETTING: In vitro fertilization unit. PATIENT(S): Fifty-one couples undergoing preimplantation genetic screening or preimplantation genetic diagnosis for translocations by array-comparative genomic hybridization on PBs (n = 21) or blastomeres (n = 30). INTERVENTION(S): BFs and TE cells were retrieved from 116 blastocysts, whose chromosome status had already been established by PB or blastomere assessment. Separate chromosome analysis was performed in 70 BFs. MAIN OUTCOME MEASURE(S): Presence of DNA in BFs, evaluation of the chromosome condition, and comparison with the diagnosis made in TE cells and at earlier stage biopsies. RESULT(S): DNA detection was 82%, with a net improvement after refinement of the procedure. In 97.1% of BFs, the ploidy condition corresponded to that found in TE cells, with one false positive and one false negative. The rate of concordance per single chromosome was 98.4%. Ploidy and chromosome concordance with PBs were 94% and 97.9%, respectively; with blastomeres, the concordances were 95% and 97.7%, respectively. Segmental abnormalities, which were detected in PBs or blastomeres of 16 blastocysts, were also identified in the corresponding BFs. CONCLUSION(S): BF represents to a good extent the blastocyst ploidy condition and chromosome status when compared with TE cells. If the proportion of clinically useful BFs is improved, blastocentesis could become the preferred source of DNA for chromosomal testing.

Karyomapping identifies second polar body DNA persisting to the blastocyst stage: implications for embryo biopsy.

Blastocyst biopsy is now widely used for both preimplantation genetic screening (PGS) and preimplantation genetic diagnosis (PGD). Although this approach yields good results, variable embryo quality and rates of development remain a challenge. Here, a case is reported in which a blastocyst was biopsied for PGS by array comparative genomic hybridization on day 6 after insemination, having hatched completely. In addition to a small trophectoderm sample, excluded cell fragments from the subzonal space from this embryo were also sampled. Unexpectedly, the array comparative genomic hybridization results from the fragments and trophectoderm sample were non-concordant: 47,XX,+19 and 46,XY, respectively. DNA fingerprinting by short tandem repeat and amelogenin analysis confirmed the sex chromosome difference but seemed to show that the two samples were related but non-identical. Genome-wide single nucleotide polymorphism genotyping and karyomapping identified that the origin of the DNA amplified from the fragments was that of the second polar body corresponding to the oocyte from which the biopsied embryo developed. The fact that polar body DNA can persist to the blastocyst stage provides evidence that excluded cell fragments should not be used for diagnostic purposes and should be avoided when performing embryo biopsies as there is a risk of diagnostic errors.

Live birth after PGD with confirmation by a comprehensive approach (karyomapping) for simultaneous detection of monogenic and chromosomal disorders.

Preimplantation genetic diagnosis (PGD) for monogenic disorders has the drawback of time and cost associated with tailoring a specific test for each couple, disorder, or both. The inability of any single assay to detect the monogenic disorder in question and simultaneously the chromosomal complement of the embryo also limits its application as separate tests may need to be carried out on the amplified material. The first clinical use of a novel approach ('karyomapping') was designed to circumvent this problem. In this example, karyomapping was used to confirm the results of an existing PGD case detecting both chromosomal abnormalities and a monogenic disorder (Smith-Lemli-Opitz [SLO] syndrome) simultaneously. The family underwent IVF, ICSI and PGD, and both polar body and cleavage stage biopsy were carried out. Following whole genome amplification, array comparative genomic hybridisation of the polar bodies and minisequencing and STR analysis of single blastomeres were used to diagnose maternal aneuploidies and SLO status, respectively. This was confirmed, by karyomapping. Unlike standard PGD, karyomapping required no a-priori test development. A singleton pregnancy and live birth, unaffected with SLO syndrome and with no chromosome abnormality, ensued. Karyomapping is potentially capable of detecting a wide spectrum of monogenic and chromosome disorders and, in this context, can be considered a comprehensive approach to PGD.

Triphenyltin chloride induces spindle microtubule depolymerisation and inhibits meiotic maturation in mouse oocytes.

Meiosis produces haploid gametes for sexual reproduction. Triphenyltin chloride (TPTCL) is a highly bioaccumulated and toxic environmental oestrogen; however, its effect on oocyte meiosis remains unknown. We examined the effect of TPTCL on mouse oocyte meiotic maturation in vitro and in vivo. In vitro, TPTCL inhibited germinal vesicle breakdown (GVBD) and first polar body extrusion (PBE) in a dose-dependent manner. The spindle microtubules completely disassembled and the chromosomes condensed after oocytes were exposed to 5 or 10µgmL(-1) TPTCL. γ-Tubulin protein was abnormally localised near chromosomes rather than on the spindle poles. In vivo, mice received TPTCL by oral gavage for 10 days. The general condition of the mice deteriorated and the ovary coefficient was reduced (P<0.05). The number of secondary and mature ovarian follicles was significantly reduced by 10mgkg(-1) TPTCL (P<0.05). GVBD decreased in a non-significant, dose-dependent manner (P>0.05). PBE was inhibited with 10mgkg(-1) TPTCL (P<0.05). The spindles of in vitro and in vivo metaphase II oocytes were disassembled with 10mgkg(-1) TPTCL. These results suggest that TPTCL seriously affects meiotic maturation by disturbing cell-cycle progression, disturbing the microtubule cytoskeleton and inhibiting follicle development in mouse oocytes.

[Aneuploidies in oocytes used in IVF programs].

The aim of the study was to investigate with FISH the frequency of aneuploidies of the first and second polar bodies (PB-I and PB-II) of oocytes in women participating in IVF programs. The study included 93 women, 82 of them were after controlled ovulation stimulation (COS), 11 in natural cycles. FISH in 238 PB-I and PB-II was done. Revealed that the frequency of aneuploidies in oocytes after COS was higher than in the natural cycle, and also was higher after COS in women with infertility compared to women stimulated because of male infertility and donors of oocytes. Aneuploidies of oocytes after COS are more common in patients after 35 years old. Thus, the study of aneuplodies of PB-I and PB-II by FISH is an informative tool of pregestation genetic diagnosis.

Polar body biopsy.

Polar body biopsy combined with array comparative genomic hybridization allows detection of maternal chromosomal aberrations. Although it has limitations, it can be seen as an alternative to blastomere and trophectoderm biopsy.

Polar body analysis by array comparative genomic hybridization accurately predicts aneuploidies of maternal meiotic origin in cleavage stage embryos of women of advanced maternal age.

STUDY QUESTION: How accurate is array comparative genomic hybridization (array CGH) analysis of the first polar body (PB1) and second polar body (PB2) in predicting aneuploidies of maternal meiotic origin in the cleavage stage embryos of women of advanced maternal age? SUMMARY ANSWER: Almost all of the aneuploidies detected in cleavage stage embryos were associated with copy number changes in the polar bodies (93%) and all but one (98.5%) were predicted to be aneuploid. A minority of copy number changes (17%), mainly in PB1, did not result in the predicted changes in the embryo, but many of these were small copy number changes, which are likely to be artefacts. WHAT IS KNOWN ALREADY: Chromosome aneuploidy is a major cause of pregnancy failure and loss, abnormal pregnancy and live births. Most aneuploidy is of maternal meiotic origin and increases exponentially in the decade preceding the menopause. A pilot study demonstrated a high rate of concordance between the chromosomal status predicted by polar body analysis and the corresponding zygotes in women of advanced maternal age. STUDY DESIGN, SIZE AND DURATION: Polar body biopsy and array CGH analysis of mature oocytes, which fertilized normally, to identify segregation errors in meiosis, followed by the analysis of the corresponding cleavage stage embryos (n = 34), in a consecutive series of stimulated and natural IVF cycles in women of advanced maternal age. MATERIALS, SETTING AND METHODS: Twenty couples requesting aneuploidy screening (mean ± SD of maternal age 39 ± 3 years) had 16 controlled ovarian hyperstimulation and 7 natural IVF cycles. PB1 and PB2 were biopsied from mature oocytes, prior to intracytoplasmic sperm injection (ICSI) and following confirmation of normal fertilization, respectively. Array CGH was used to detect chromosome copy number changes and to predict aneuploidy in the corresponding embryos. Embryos with normal copy number in both polar bodies were transferred but, 34 cleavage stage embryos, most of which were predicted to have one or more aneuploidies of maternal meiotic origin, were analysed in whole after removal of the zona by array CGH, on Day 3 post-ICSI. MAIN RESULTS AND THE ROLE OF CHANCE: Thirty cleavage stage embryos, predicted to have one or more aneuploidies, were all confirmed to be aneuploid (100% concordant). Seventy four aneuploidies were detected in these embryos. Sixty-nine (93%) aneuploidies were associated with copy number changes in the polar bodies and 68 (98.5%) of these had been predicted to be aneuploid. Also, 19 of 20 (95%) balanced combinations of chromatid gain/loss in PB1/PB2 accurately predicted normal copy number in the corresponding embryos. However, 17 (12%) copy number changes in the polar bodies did not result in the expected outcome, including 12 false positive predictions of aneuploidy. Most of these involved copy number changes that were smaller than would be expected for whole chromosome or chromatid imbalance and occurred significantly more often in PB1 than PB2 (P < 0.0005). Three other embryos with only small copy number changes and one embryo with a partial chromosome loss in PB2, were all confirmed to be euploid. LIMITATIONS, REASONS FOR CAUTION: Accurate false positive and negative rates will require follow-up of both euploid and aneuploid embryos, ideally using molecular genetic markers to detect aneuploidy independently and to identify their origin. WIDER IMPLICATIONS OF THE FINDINGS: Polar body biopsy and array CGH analysis is efficient and accurately predicts most aneuploidies in cleavage stage embryos. However, the size of the ratio shifts, particularly in PB1, should always be compared with the X chromosome shift before it can be concluded that there is a real copy number change. STUDY FUNDING/COMPETING INTEREST(S): Study funded by Embryogenesis, Athens. P.S. and A.H.H. are employed full time and part time, respectively, by BlueGnome Ltd, Cambridge, UK.

Detection and quantification of maternal-effect gene transcripts in mouse second polar bodies: potential markers of embryo developmental competence.

OBJECTIVE: To test the hypothesis that quantification of messenger RNAs originating from the second polar body (PB(2)) provides a noninvasive tool for assessing embryo quality. DESIGN: Prospective study. SETTING: Hospital-based academic research laboratory. ANIMAL(S): CD1 female mice. INTERVENTION(S): Metaphase II oocytes obtained from 7- to 8-week-old mice after pregnant mare's serum gonadotropin and hCG priming. After in vitro fertilization, the PB(2) was biopsied from zygote, followed by reverse transcription. Real-time polymerase chain reaction was performed to quantify gene expression levels in single PB(2). The sibling zygotes were continuously cultured to blastocyst stage. MAIN OUTCOME MEASURE(S): Embryo developmental competence and six maternal-effect gene (Dnmt1, Mater, Nobox, Npm2, Tcl1, and Zar1) transcripts in the PB(2). RESULT(S): Second polar body messenger RNA was detected in all candidate genes. Transcripts that were present in greater abundance in the zygote were more likely to be detected in quantitative polymerase chain reaction replicates from single PB(2). Four candidate genes (Dnmt1, Nobox, Npm2, and Tcl1) expression levels in PB(2) between two groups (two-cell embryo vs. blastocyts) approached statistical significance. CONCLUSION(S): Second polar bodies may contain a representative transcript profile to that of the zygote after fertilization. Differences in gene expression in PB(2) may be potential biomarkers of embryo quality.

Preimplantation genetic diagnosis to improve pregnancy outcomes in subfertility.

Pre-implantation genetic diagnosis provides prenatal genetic diagnosis before implantation, thus allowing detection of chromosomal abnormalities and their exclusion from embryo transfer in assisted reproductive technologies. Polar body, blastomere or trophectoderm can each be used to obtain requisite genetic or embryonic DNA. Pre-implantation genetic diagnosis for excluding unbalanced translocations is well accepted, and pre-implantation genetic diagnosis aneuploidy testing to avoid repeated pregnancy losses in couples having recurrent aneuploidy is efficacious in reducing miscarriages. Controversy remains about whether pre-implantation genetic diagnosis aneuploidy testing improves take home pregnancy rates, for which reason adherence to specific indications is recommended while the issue is being adjudicated. Current recommendations are for obligatory 24 chromosome testing, most readily using array comparative genome hybridisation.

New perspectives on embryo biopsy: not how, but when and why?

During the past 2 decades, biopsy for preimplantation genetic diagnosis at three stages, that is, before conception (the first polar body), after fertilization (the second polar body), and early cleavage (D3 blastomeres) or blastocyst stage (D5/D6 trophectoderm biopsy), have been optimized and performed clinically in hundreds of in vitro fertilization centers around the world. Although opening the zona pellucida by mechanical or chemical means is still effectively in use, noncontact laser has become the indispensable instrument. Overall, the invasive nature of biopsy at any given stage is recognized. It is believed that removal of the polar bodies from M-II oocytes and fertilized zygotes may have the least detrimental effects on subsequent embryonic development; hence increasing applications of polar body biopsy are anticipated. Although D3 biopsy is currently the most frequently used method, the effectiveness of D3 cleavage-stage biopsy is unsettling because of the mosaicism in early cleavage human embryos. Controversies exist in several areas; particularly, the efficacy of preimplantation genetic screening based on one cell removed from a D3 embryo remains to be confirmed. With new genetic testing technology, there may be no need to biopsy two cells because accuracy from one cell is high and the risk of misdiagnosis is very low when sufficient markers are used for chromosome copy number assessment or for mutation detection of single-gene disorders. And finally, it appears that limited harm is caused by biopsy at the blastocyst stage and mosaicism seems to be less common as compared with earlier stages. Therefore, use of the blastocyst-stage biopsy combined with cryopreservation protocol can be effectively used for several indications. Furthermore, faster genetic analytical methods that can be completed within several hours will make this strategy more practical and attractive as fresh embryo transfer is possible.