Mosaic human preimplantation embryos and their developmental potential in a prospective, non-selection clinical trial.

Chromosome imbalance (aneuploidy) is the major cause of pregnancy loss and congenital disorders in humans. Analyses of small biopsies from human embryos suggest that aneuploidy commonly originates during early divisions, resulting in mosaicism. However, the developmental potential of mosaic embryos remains unclear. We followed the distribution of aneuploid chromosomes across 73 unselected preimplantation embryos and 365 biopsies, sampled from four multifocal trophectoderm (TE) samples and the inner cell mass (ICM). When mosaicism impacted fewer than 50% of cells in one TE biopsy (low-medium mosaicism), only 1% of aneuploidies affected other portions of the embryo. A double-blinded prospective non-selection trial (NCT03673592) showed equivalent live-birth rates and miscarriage rates across 484 euploid, 282 low-grade mosaic, and 131 medium-grade mosaic embryos. No instances of mosaicism or uniparental disomy were detected in the ensuing pregnancies or newborns, and obstetrical and neonatal outcomes were similar between the study groups. Thus, low-medium mosaicism in the trophectoderm mostly arises after TE and ICM differentiation, and such embryos have equivalent developmental potential as fully euploid ones.

Endometrial Receptivity Analysis (ERA): data versus opinions.

This article summarises and contextualises the accumulated basic and clinical data on the ERA test and addresses specific comments and opinions presented by the opponent as part of an invited debate. Progress in medicine depends on new technologies and concepts that translate to practice to solve long-standing problems. In a key example, combining RNA sequencing data (transcriptomics) with artificial intelligence (AI) led to a clinical revolution in personalising disease diagnosis and fostered the concept of precision medicine. The reproductive field is no exception. Translation of endometrial transcriptomics to the clinic yielded an objective definition of the limited time period during which the maternal endometrium is receptive to an embryo, known as the window of implantation (WOI). The WOI is induced by the presence of exogenous and/or endogenous progesterone (P) after proper oestradiol (E2) priming. The window lasts 30-36 hours and, depending on the patient, occurs between LH + 6 and LH + 9 in natural cycles or between P + 4 and P + 7 in hormonal replacement therapy (HRT) cycles. In approximately 30% of IVF cycles in which embryo transfer is performed blindly, the WOI is displaced and embryo-endometrial synchrony is not achieved. Extending this application of endometrial transcriptomics, the endometrial receptivity analysis (ERA) test couples next-generation sequencing (NGS) to a computational predictor to identify transcriptomic signatures for each endometrial stage: proliferative (PRO), pre-receptive (PRE), receptive (R) and post-receptive (POST). In this way, personalised embryo transfer (pET) may be possible by synchronising embryo transfer with each patient's WOI. Data are the only way to confront arguments sustained in opinions and/or misleading concepts; it is up to the reader to make their own conclusions regarding its clinical utility.

Analysis of a Preimplantation Genetic Test for Aneuploidies in Embryos from Colombian Couples: A Report of Cases.

BACKGROUND: Assisted reproduction techniques (ARTs) and the preimplantation genetic test for aneuploidies (PGT-A) help couples with fertility problems to achieve a healthy live birth around the world. The aim of this study was to determine the rate of whole chromosomal copy number variations in embryos from couples undergoing ART and PGT-A, associations of chromosomal variations with embryo morphological parameters, and their relationship to maternal age. METHODS: This study included a retrospective analysis of the number of whole chromosomal copies identified by aCGH in embryos from couples undergoing ART. RESULTS: Seventy-six embryos from 29 couples using their own gametes were analyzed, of which 25 (32.9%) were chromosomally normal, and 51 (67.1%) were abnormal. Eleven embryos were evaluated from the group of couples with donated gametes, of which 5 (45.4%) embryos were chromosomally normal, and 6 (54.5%) embryos were abnormal. The main aneuploidies observed were trisomy X (7.8%), trisomy 21 (5.9%), trisomy 9 (3.9%), monosomy 11 (3.9%), monosomy 13 (3.9%) and monosomy X (3.9%), and the principal chromosomes affected were 19, X and 13. A significant association was found between the quality of the embryo and the genetic condition: embryos with euploidy and aneuploidy (p=0.046). CONCLUSION: The rate of aneuploidies from couples with their own gametes was 67.1% (51/76) and from couples with donated eggs and/or sperm was 54.5% (6/11). The quality of the embryo determinated by the morphological parameters was not associated with the embryo genetic status, and also there was no association between maternal age and aneuploidy rate.

Errors at mitotic segregation early in oogenesis and at first meiotic division in oocytes from donor females: comparative genomic hybridization analyses in metaphase II oocytes and their first polar body.

The aim of this work is to analyze, using the comparative genomic hybridization technique, the frequencies and the mechanisms involved in the production of aneuploidy events in donor oocytes. The results showed that 32.1% of them were aneuploid, with 51.7% of those originating from first meiotic division errors and 48.3% from the presence of aneuploid oogonium.

Meiotic segregation and interchromosomal effect in the sperm of a double translocation carrier: a case report.

BACKGROUND: Infertility is a natural mechanism of selection intended to prevent the delivery of a child with malformations or mental retardation. Male infertility is closely related to chromosomal abnormalities. This study was focused on the analysis of meiotic segregation involving a Robertsonian translocation, 45,XY,der(13;13) [56]/45,XY,der(13;14) [44] and the evaluation of possible interchromosomal effects. RESULTS: Hybridisation with LSI 13q14 and subtelomere 14q probes and WCP13 SpectrumGreen and WCP14 SpectrumOrange probes showed a high proportion of unbalanced gametes, corresponding to 71.2% of the spermatozoa. The disomic frequencies of the sexual chromosomes and chromosome 18 of the patient were higher (5.28% and 2.55%, respectively) than those of the control (0.6% and 0.59%, respectively). CONCLUSION: Meiotic segregation studies in sperm are an important tool for genetic counselling of chromosomal aberrations, allowing for a prediction of the risks and consequent implications for the reproductive life. The patient with this rare translocation exhibited meiotic segregation fidelity, and a high rate of unbalanced gametes with disomic spermatozoa.

Diagnóstico genético pré-implantacional / Pre-implantational genetic diagnosis

Background: The ranks of patients seeking preimplantation genetic diagnosis (PGD) to identify embryos with monogenic disorders like cystic fibrosis or thalassemia are growing rapidly. Even so, the most common indication for preimplantation embryo testing remains the risk of chromosomal imbalance. In most cases, the PGD strategy employed for chromosomal testing involves biopsying a single cell (blastomere) from each embryo at the 6 to 10-cell stage, 3 days after fertilization. The cell is placed on a microscope slide, fixed, and then subjected to cytogenetic analysis. While the biopsied cell is being analyzed, the rest of the embryo is maintained in culture. Most infertility clinics prefer to transfer the embryos no later than day-5 post fertilization. Consequently, PGD methods need to be extremely rapid, providing a result in less than 48 hours. Review: Most chromosomal PGD protocols employ fluorescence in situ hybridization (FISH). This approach involves the hybridization of chromosome specific DNA probes, labeled with different colors, to nuclei spread on a microscope slide. The method is rapid, performs equally well whether applied to interphase nuclei, and permits enumeration of up to 10 chromosomes per cell. Initially, the PGD for aneuploidy was envisioned that most of the patients seeking PGD for aneuploidy would be those who carry a chromosomal rearrangement. Couples in which one of the partners carries a chromosomal rearrangement frequently experience miscarriage or bear children due to chromosome imbalance. However, in recent years the vast majority of patients requesting PGD for aneuploidy have in fact been chromosomally normal individuals undergoing IVF. Early methods employed five FISH probes for PGD, focusing on the chromosomes most often found to be abnormal in prenatal samples (13, 18, 21, X, and Y). Aneuploidies for these chromosomes are sometimes compatible with survival to term, leading to aneuploid syndromes. This strategy was successful in reducing the number of such syndromes, but a statistically significant improvement in embryo implantation could not be shown. Later PGD studies expanded the number of chromosomes assessed to eight. This was achieved by performing two sequential rounds of FISH analysis, assessing five chromosomes in the first round and three more in the second. The three new chromosomes added to the PGD screen (15, 16, and 22) are frequently found to be aneuploid in miscarriages. The eight-chromosome PGD protocol led to a doubling of embryo implantation rates in two separate studies and reduced the number of spontaneous abortions. Although this problem can be partially overcome by performing sequential FISH experiments on the same cell, the accuracy of the method declines with each additional hybridization. The good news is that there is a method related to FISH­comparative genomic hybridization (CGH)­ that can detect aneuploidy that affects any chromosome within a sample. In addition to offering comprehensive detection, CGH can be used on interphase cells. Conclusion: In summary, the use of FISH for the purpose of PGD has already improved IVF outcome for several groups of infertile patients, including women aged 37 and above, those with recurrent miscarriages, women with a previous comprehensive screening for aneuploidy will likely further increase the benefit of PGD to these patients and maybe even a broader range of patients. The widespread availability of CGH for PGD is nearly at hand, but while we await final refinements and validation, PGD strategies can still be improved by making the best use of current methods and reassessing the chromosomes selected for screening.