Objective
Assisted oocyte activation (AOA) can restore fertilization rates after IVF/ICSI cycles with fertilization failure. AOA is an experimental technique, and its downstream effects remain poorly ...characterized. Clarifying the relationship between AOA and embryo, morphokinetics could offer complementary insights into the quality and viability of the embryos obtained with this technique. The aim of this study is to compare the preimplantation morphokinetic development of embryos derived from ICSI-AOA (experimental group) vs. ICSI cycles (control group).
Methods
A retrospective cohort study was carried out with 141 embryos from fresh oocyte donation cycles performed between 2013 and 2017; 41 embryos were derived from 7 ICSI-AOA cycles and 100 embryos from 18 ICSI cycles. Morphokinetic development of all embryos was followed using a time-lapse system.
Results
We show that embryos from both groups develop similarly for most milestones, with the exception of the time of second polar body extrusion (tPB2) and the time to second cell division (t3).
Conclusions
We conclude that ionomycin mediated AOA does not seem to affect the morphokinetic pattern of preimplantation embryo development, despite the alterations found in tPB2 and t3, which could directly reflect the use of a Ca
2+
ionophore as a transient and quick non-physiologic increase of free intracytoplasmic Ca
2+
.
STUDY QUESTION
How does vitrification affect oocyte viability?
SUMMARY ANSWER
Vitrification does not affect oocyte viability in oocyte donation cycles.
WHAT IS KNOWN ALREADY
Oocyte vitrification is ...performed routinely and successfully in IVF and oocyte donation programs.
STUDY DESIGN, SIZE, DURATION
This is a prospective study performed between June 2009 and February 2012 to compare ongoing pregnancy rates and other indices of viability between fresh and vitrified oocytes. A total of 99 donations with more than 16 oocytes (MII) in which oocytes were allocated both to a synchronous recipient (fresh oocytes) and to an asynchronous recipient (vitrified oocytes) were included.
PARTICIPANTS/MATERIALS, SETTING, METHODS
The participants were consenting couples (donors and recipients) from the oocyte donation program. On the day of retrieval, the oocytes allocated to the synchronous recipient were inseminated and those allocated for banking were denuded of cumulus and vitrified. Vitrified oocytes were microinjected with spermatozoa 2 h after warming. Embryo transfer was performed on Day 2 of development in both groups, and the remaining embryos were cryopreserved on Day 3. Clinical pregnancy was defined by a positive fetal heartbeat at 6 weeks.
MAIN RESULTS AND ROLE OF CHANCE
A total of 989 oocytes were warmed and 85.6% survived. No significant differences were observed between fresh and vitrified oocytes: fertilization rate (80.7 versus 78.2%), ongoing embryo rate (71.0 versus 68.2%) or good-quality embryo rate (54.1 versus 49.8%). The mean number of embryos transferred was similar in both groups (1.82 ± 0.44 versus 1.90 ± 0.34). The implantation rate (33.3 versus 34.0%) and the multiple pregnancy rate (27.7 versus 20.8) were also similar between both groups (P > 0.05). The live birth rate per cycle was 38.4% in the recipients of fresh oocytes and 43.4% in the recipients of vitrified oocytes (P > 0.05). Eighty five frozen embryo transfers were also evaluated. Comparing embryos from fresh and vitrified oocytes there were no significant differences in the embryo survival rate (70.1 versus 65.8%), clinical pregnancy rate (40.8 versus 33.3%) or implantation rate (21.8 versus 26.8%).
LIMITATIONS, REASONS FOR CAUTION
The oocytes were donated by healthy, young women (≤35 years) and these results cannot be extrapolated to other populations.
WIDER IMPLICATIONS OF THE FINDINGS
Outcomes obtained with vitrified oocytes are as good as with fresh oocytes and the use of vitrification can be extended to new applications, e.g. accumulation of oocytes from successive stimulations for preimplantation genetic diagnosis, for patients at risk of ovarian hyperstimulation syndrome or in patients needing to preserve their fertility.
STUDY FUNDING/COMPETING INTEREST(S)
This work was done under the auspices of the Càtedra d'Investigació en Obstetrícia i Ginecologia of the Universitat Autònoma de Barcelona.
Abstract
Study question
Does oocyte donation improve reproductive outcomes in recurrent pregnancy loss (RPL) patients?
Summary answer
Oocyte donation increases live birth and reduces miscarriage ...rates in RPL women older than 35, but it does not improve reproductive outcomes in younger patients.
What is known already
Recurrent pregnancy loss (RPL) is defined as 2 or more pregnancy losses prior to 20-24 weeks of gestation and has an incidence of approximately 1 to 2% in couples trying to conceive. Known risk factors for RPL are embryo aneuploidy, advanced maternal age (AMA), previous miscarriages, uterine abnormalities, parental chromosomal abnormalities, antiphospholipid syndrome, endocrine factors, such as thyroid function or obesity, and thrombophilia. However, 50-70% of patients suffering from RPL do not present any known risk factor, making the management of idiopathic RPL patients particularly challenging for ART clinicians.
Study design, size, duration
This is a cohort retrospective study involving 2 centers. Charts from 18,273 women undergoing IVF treatment between 2011 and 2020 were reviewed. A total of 912 patients (5%) met the definition of RPL and were classified into study groups based on their age and oocyte origin: ≤35 years old receiving oocyte donation (n = 39) or using their own oocytes (n = 35), and AMA women using donor eggs (n = 716) or their own (n = 122).
Participants/materials, setting, methods
Demographic variables analysed included known risk factors, number of transferred embryos, day of embryo transfer (3 vs 5) and sperm origin (partner/donor). Differences in biochemical, clinical, ongoing pregnancy, miscarriage and live birth rates were assessed by Pearson’s Chi-squared or Fisher’s exact test. P-values <0.05 were considered significant.
Main results and the role of chance
RPL patients had 2.77±1.27 pregnancy losses overall (2.76±1.37 in women ≤35 and 2.77±1.26 in patients >35). Most RPL patients (91.9%) were of AMA. Other RPL-associated risk factors, including uterine malformations, previous pregnancy losses, chromosomal abnormalities and thrombophilia were identified in 207/912 patients (22.7%). Interestingly, these were more frequent in patients <35 (37.8% vs 21%, p = 0.001). Young RPL women presented higher rates of karyotype abnormalities than older patients (17.6% vs 3.8%, p < 1x10-04), while showing a similar incidence of uterine abnormalities (14.9% vs 12.9%, p > 0.63) and thrombophilia (4.1% vs 4.7%, p > 0.81).
RPL patients >35 preferentially underwent oocyte donation (85.4% vs 52.7%, p < 1x10-04), which led to significantly higher biochemical (52.5% vs 17.1%, p < 1x10-04), clinical (42.4% vs. 8.5% p < 1x10-04), ongoing pregnancy (37.9% vs 5.1%, p < 1x10-04), live birth (32% vs 4%, p < 1x10-04) and lower miscarriage rates (10.5% vs 40%, p = 0.0186) than in autologous cycles. In contrast, RPL patients <35 had similar reproductive outcomes: biochemical (41% vs. 52.9), clinical (28.2% vs. 37.1%), ongoing pregnancy (25.6% vs 29.4%), live birth (25.6% vs 26.4%) and miscarriage rates (9% vs 23%), regardless of oocyte origin (donated vs own, p > 0.05 for all cases). Importantly, this was also true for a small subgroup of idiopathic young RPL patients (n = 13).
Limitations, reasons for caution
The main limitation of this study is its retrospective nature, which does not allow for full elucidation of all potential confounders. The number of young RPL patients undergoing oocyte donation may be too low to draw significant conclusions.
Wider implications of the findings
RPL can be resolved in AMA patients by using donor oocytes, which points to key roles of oocyte quality and aneuploidy underlying RPL aetiology. However, RPL is not ameliorated by oocyte donation in young women, suggesting an endometrial/systemic origin and highlighting the need to further study mechanisms driving this disorder.
Trial registration number
Not applicable
BACKGROUND: Routine oocyte cryopreservation remains an elusive technique in the wide range of assisted reproductive technologies available. This study examines the effect of a cryopreservation ...protocol on the spindle and chromosome configurations of human oocytes cryopreserved at the germinal vesicle (GV) and metaphase II (MII) stage. METHODS: GV oocytes were randomly assigned to one of three groups: (i) control oocytes matured in vitro to MII stage (n = 156); (ii) oocytes cryopreserved at the GV stage and then matured in vitro (n = 90); (iii) oocytes cryopreserved at the MII stage (n = 147). Following cryopreservation and in-vitro maturation, immunostaining of tubulin and chromatin was performed, before visualization using confocal microscopy. RESULTS: A statistically significant increase was observed in the survival rate in group 2 (73.3%, 66/90) compared to group 3 (55.7%, 82/147) (P < 0.007). Exposure of oocytes to the cryoprotective solutions without freezing had no effect on the structure of their second meiotic spindle. However, statistically significant differences were observed on both spindle and chromosome configurations of oocytes from group 2 (5.2 and 5.2% respectively) and group 3 (16.2 and 18.8% respectively) compared with group 1 oocytes (71.6 and 82.0% respectively) (P < 0.001 in all cases). CONCLUSIONS: The protocol followed results in high rates of survival and potential for in-vitro maturation, but has a deleterious effect on the organization of the meiotic spindle of human oocytes cryopreserved at both the GV and MII stages.
Are morphokinetic measurements of time lapse-videos of human embryos comparable among operators?
There is little variation among morphokinetic measurements taken by different operators when analyzing ...the same time lapse-videos of human embryos.
Morphokinetic analysis of preimplantation embryo development is a complementary method of embryo assessment increasingly used in IVF laboratories. Time-lapse videos of embryo development are normally viewed by trained embryologists and annotated with the times when specific developmental events occur. Such annotations form the basis of embryo selection algorithms, used to rank the embryos for transfer. It is unknown whether the reliability of morphokinetic annotations is related to the morphological characteristics of the analyzed embryo or to the ability of the embryologists performing the annotation. One study so far reported the reliability of morphokinetic annotations among three embryologists using the time-lapse system (TLS), but larger studies with different setups are needed to address this issue further.
A prospective study was carried out between October 2015 and June 2016. Six embryologists with various degrees of experience in static, morphology-based evaluation, individually annotated the same 93 videos of preimplantation development, corresponding to 18 IVF/ICSI cycles, recorded with a TLS.
Times of second polar body extrusion, appearance and disappearance of pronuclei, and embryo cleavages (times from 2-cell to 5-cell stage: t2, t3, t4, t5) were annotated. Each embryologist was blinded to the annotations of the others. Intra- and inter-observer agreement was evaluated by computing intra-class correlation coefficients (ICCs).
In the inter-observer analysis, most ICCs obtained were higher than 0.80, indicating a high level of agreement: t2: 0.93; t3: 0.80; t4: 0.89; t5: 0.89; disappearance of two pronuclei: 0.98. However, the ICCs obtained for second polar body extrusion and the appearance of two pronuclei annotations was lower: 0.51 and 0.63, respectively, indicating an average level of agreement. The ICCs obtained from the intra-observer analysis were also higher than 0.80 (t2: 0.96; t3: 0.89; t4: 0.88; t5: 0.86; disappearance of two pronuclei: 0.96). The ICCs obtained from second polar body extrusion and the appearance of two pronuclei annotations were 0.77 and 0.66, respectively. These results indicate that developmental timings, annotated in time-lapse videos, are highly reliable both within and among observers.
The events at the developmental stages from 6-cells to blastocyst were not evaluated; since some morphokinetic algorithms use times past the 6-cell stage in their calculations, further studies should be carried out to understand the variations among observers in these cases.
Time-lapse measurement should be as objective as possible, especially for the first embryo cleavages, because they are often measured to define algorithms to assess the embryonic implantation potential. Our results show that measurements using this particular TLS are consistent and reliable both within and among operators.
None.
Not applicable.
Does a preferential X chromosome inactivation (XCI) pattern exist in female human pluripotent stem cells (hPSCs) and does the pattern change during long-term culture or upon differentiation?
We ...identified two independent phenomena that lead to aberrant XCI patterns in female hPSC: a rapid loss of histone H3 lysine 27 trimethylation (H3K27me3) and long non-coding X-inactive specific transcript (XIST) expression during culture, often accompanied by erosion of XCI-specific methylation, and a frequent loss of random XCI in the cultures.
Variable XCI patterns have been reported in female hPSC, not only between different hPSC lines, but also between sub-passages of the same cell line, however the reasons for this variability remain unknown. Moreover, while non-random XCI-linked DNA methylation patterns have been previously reported, their origin and extent have not been investigated.
We investigated the XCI patterns in 23 human pluripotent stem cell (hPSC) lines, during long-term culture and after differentiation, by gene expression analysis, histone modification assessment and study of DNA methylation. The presence and location of H3K27me3 was studied by immunofluorescence, XIST expression by real-time PCR, and mono- or bi-allelic expression of X-linked genes was studied by sequencing of cDNA. XCI-specific DNA methylation was analysed using methylation-sensitive restriction and PCR, and more in depth by massive parallel bisulphite sequencing.
All hPSC lines showed XCI, but we found a rapid loss of XCI marks during the early stages of in vitro culture. While this loss of XCI marks was accompanied in several cases by an extensive erosion of XCI-specific methylation, it did not result in X chromosome reactivation. Moreover, lines without strong erosion of methylation frequently displayed non-random DNA methylation, which occurred independently from the loss of XCI marks. This bias in X chromosome DNA methylation did not appear as a passenger event driven by clonal culture take-over of chromosome abnormalities and was independent of the parental origin of the X chromosome. Therefore, we suggest that a culture advantage conferred by alleles on the X chromosome or by XCI-related mechanisms may be at the basis of this phenomenon. Finally, differentiated populations inherited the aberrant XCI patterns from the undifferentiated cells they were derived from.
All hPSC lines in this study were cultured in highly similar conditions. Our results may therefore be specific for these conditions and alternative culture conditions might lead to different findings. Our findings are only a first step towards elucidating the molecular events leading to the phenomena we observed.
Our results highlight the significant extent of aberrant XCI in female hPSC. The fact that these aberrations are inherited by the differentiated progeny may have a significant impact on downstream research and clinical uses of hPSC. In order to achieve the full potential of hPSC, more insight into the XCI status and its stability in hPSC and its effect on the properties of the differentiated progeny is needed.
Not applicable.
Our research is supported by grants from the Research Foundation - Flanders (FWO-Vlaanderen, grant 1502512N), Generalitat de Catalunya (2014SGR-005214) and the Methusalem grant of the Research Council of the Vrije Universiteit Brussel, on name of K.S. L.V.H. is funded by EMBO (ALTF 701-2013). The authors declare no potential conflict of interest.
Our purpose was to detect aneuploidy for chromosomes 13, 16, 18, 21, 22, X, and Y in preimplantation embryos from patients with a history of unexplained recurrent miscarriage.
Three patients with a ...history of unexplained recurrent spontaneous abortion were included in this study. Embryos were biopsied at the eight-cell stage, individually fixed on slides, and processed for fluorescent in situ hybridization (FISH). A multiple FISH protocol for seven chromosomes pairs (13, 16, 18, 21, 22, X, and Y) has been developed.
A total of 39 embryos was studied with the multiple FISH protocol developed. Successful analysis of the biopsied embryos was achieved within the time limits usually allowed in a preimplantation diagnosis program. Analysis of the blastomeres showed that 17 embryos were chromosomally normal for the probes used, 16 embryos were aneuploid, and in 6 embryos no informative results were obtained.
In the patients studied, a large proportion of embryos (41%) exhibited chromosomal abnormalities for the probes used. Preimplantation diagnosis to screen for chromosome abnormalities could be a feasible approach to improve the possibility of successful pregnancy in these couples.
A new methodology for blastocyst biopsy that uses a 1.48 microm diode laser is described. Trophectoderm cells are biopsied after laster zona drilling and culture, fixed and processed for fluorescent ...in situ hybridisation (FISH) analysis. Preliminary results on the efficiency of the procedure and blastocyst recovery rate are promising. Blastocyst laser biopsy is a useful tool in preimplantation genetic diagnosis (PGD) as it allows a more reliable diagnosis and widens the diagnostic possibilities on account of the higher number of cells obtained in the biopsy.
Indications and candidates for preimplantation genetic diagnosis (PGD) have increased in recent years. This study evaluates whether IVF–intracytoplasmic sperm injection (ICSI) results could be ...improved by selecting embryos through PGD–AS (aneuploidy screening) in couples in whom the male partner presents meiotic abnormalities. Two hundred and fifty-six embryos were biopsied and 183 were suitable for analysis (73.2%). Ninety-two embryos showed normal chromosomal analysis (50.3% of the analysed embryos and 57.5% of the diagnosed embryos). Pregnancy, abortion and implantation rates were compared with 66 IVF–ICSI cycles performed in 44 patients with meiotic abnormalities without PGD (control group). No statistically significant differences in the pregnancy rate (52 versus 43.9%), implantation rate (32.1 versus 23.5%) and miscarriage rate (15.4 versus 10.3%) were observed between the groups. Although the embryos obtained from men with meiotic abnormalities showed a high frequency of chromosome abnormalities, no improvements in pregnancy and implantation rates were obtained after PGD–AS in the series analysed.
Zygotes morphologically classified as tripronuclear (3PN) after intracytoplasmic sperm injection (ICSI), which are thought to be digynic in their origin, were studied by fluorescent in-situ ...hybridization (FISH). FISH results allowed us to assess the suspected ploidy after morphological evaluation of the zygote and to determine the origin of the third pronuclei. Our results show that, firstly, 36% of those zygotes classified as 3PN following their morphological evaluation were, in fact, diploid, and secondly, the main cause for triploidy after ICSI is the non-extrusion of the second polar body.
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