Altered patterning of neural activity in a tauopathy mouse model

Alzheimer's disease (AD) is a complex neurodegenerative condition that manifests at multiple levels and involves a spectrum of abnormalities ranging from the cellular to cognitive. Here, we investigate the impact of AD-related tau-pathology on hippocampal circuits in mice engaged in spatial navigation, and study changes of neuronal firing and dynamics of extracellular fields. While most studies are based on analyzing instantaneous or time-averaged characteristics of neuronal activity, we focus on intermediate timescales-spike trains and waveforms of oscillatory potentials, which we consider as single entities. We find that, in healthy mice, spike arrangements and wave patterns (series of crests or troughs) are coupled to the animal's location, speed, and acceleration. In contrast, in tau-mice, neural activity is structurally disarrayed: brainwave cadence is detached from locomotion, spatial selectivity is lost, the spike flow is scrambled. Importantly, these alterations start early and accumulate with age, which exposes progressive disinvolvement the hippocampus circuit in spatial navigation. These features highlight qualitatively different neurodynamics than the ones provided by conventional analyses, and are more salient, thus revealing a new level of the hippocampal circuit disruptions.

Factors associated with embryo mosaicism: a systematic review and meta-analysis

PURPOSE

Evaluate which factors are involved in the increased rate of mosaicism in embryos.

METHODS

A systematic review and meta-analysis was performed. After an exhaustive search of the literature, a total of seven papers were included in the analysis. In addition, data collected from IVF cycles performed in our fertility clinic were also analysed. Day of biopsy, embryo quality, maternal and paternal age and seminal quality were the chosen factors to be studied.

RESULTS

The results of the meta-analysis show that neither embryo quality nor seminal quality were related to mosaic embryo rate (OR: 1.09; 95% CI: 0.94-1.28 and OR: 1.10; 95% CI: 0.87-1.37, respectively). A positive association was observed for the variable "biopsy day" with embryos biopsied at day 6 or 7 having the highest rate of mosaicism (OR: 1.06; 95% CI: 1.01-1.11). In opposite to what happens with aneuploidy rate, which increases with maternal age, embryo mosaicism is higher in younger women (<34 years) rather than in older ones (≥34 years) (OR: 0.95; 95% CI: 0.92-0.98). However, for the "paternal age" factor, no association with mosaicism was found (OR: 1.04; 95% CI: 0.90-1.21).

CONCLUSIONS

With the present study, we can conclude that the factors related to the presence of mosaicism in embryos are the embryo biopsy day and maternal age. The rest of the studied factors showed no significant relationship with mosaicism. These results are of great importance as knowing the possible causes leading to mosaicism helps to improve the clinical results of reproductive treatments.

Identification of novel candidate genes associated with meiotic aneuploidy in human embryos by whole-exome sequencing

PURPOSE

To identify novel genetic variants responsible for meiotic embryonic aneuploidy.

METHODS

A prospective observational cohort study that included 29 couples who underwent trophectoderm biopsies from 127 embryos and performed whole-exome sequencing (WES) between November 2019 and March 2022. Patients were divided into two groups according to the expected embryo aneuploidy rate based on maternal age.

RESULTS

After variant filtering in the WES analysis of 58 patients/donors, five heterozygous variants were identified in female partners from the study group that had an impact on embryo aneuploidy. Additionally, a slowdown in embryo development and a decrease in the number of blastocysts available for biopsy were observed in the study group embryos.

CONCLUSION

This study has identified new candidate genes and variants not previously associated with meiotic embryo aneuploidy, but which are involved in important biological processes related to cell division and chromosome segregation. WES may be an efficient tool to identify patients with a higher-than-expected risk of embryo aneuploidy based on maternal age and allow for individualized genetic counselling prior to treatment.

Ticks harbor and excrete chronic wasting disease prions

Chronic wasting disease (CWD) is a fatal neurodegenerative disease caused by infectious prions (PrP^CWD) affecting cervids. Circulating PrP^CWD in blood may pose a risk for indirect transmission by way of hematophagous ectoparasites acting as mechanical vectors. Cervids can carry high tick infestations and exhibit allogrooming, a common tick defense strategy between conspecifics. Ingestion of ticks during allogrooming may expose naïve animals to CWD, if ticks harbor PrP^CWD. This study investigates whether ticks can harbor transmission-relevant quantities of PrP^CWD by combining experimental tick feeding trials and evaluation of ticks from free-ranging white-tailed deer (Odocoileus virginianus). Using the real-time quaking-induced conversion (RT-QuIC) assay, we show that black-legged ticks (Ixodes scapularis) fed PrP^CWD-spiked blood using artificial membranes ingest and excrete PrP^CWD. Combining results of RT-QuIC and protein misfolding cyclic amplification, we detected seeding activity from 6 of 15 (40%) pooled tick samples collected from wild CWD-infected white-tailed deer. Seeding activities in ticks were analogous to 10-1000 ng of CWD-positive retropharyngeal lymph node collected from deer upon which they were feeding. Estimates revealed a median infectious dose range of 0.3-42.4 per tick, suggesting that ticks can take up transmission-relevant amounts of PrP^CWD and may pose a CWD risk to cervids.

The World Animal Health Information System as a tool to support decision-making and research in animal health

The World Animal Health Information System (WAHIS) collects and publishes a wealth of information gathered by individual countries' Veterinary Services, including detailed country-specific information on outbreaks of diseases listed by the World Organisation for Animal Health (WOAH, founded as OIE), including emerging diseases, in domestic animals and wildlife, and non-listed diseases in wildlife. The data set is one of the most comprehensive in the world, with 182 Members obliged to report this information to WOAH in a timely manner. As such, the data provide invaluable input for Veterinary Services, animal health researchers and stakeholders to gain insight into risk from infectious diseases, for example through the development of predictive models and risk assessments to address the risk from trade of animal products, globalisation, or movement of wildlife or vectors across country borders. This paper reviews previous analyses that have been conducted using WAHIS data and outlines ways in which these data can be used for preparedness and risk assessment.

Survival analysis of productive life in Florida dairy goats using a Cox proportional hazards model

Longevity is an economically important trait, since extending the functional life of a doe would allow us to keep the most productive females in the herd as long as possible, and this could result in the increased profitability of dairy farms. Thus, the objectives of this study were to determine the most important factors that influence the length of productive life (LPL) of female Florida goats and to estimate its genetic additive variance using a Cox proportional hazards model. The data consisted of 70,695 productive life records from 25,722 Florida females kidding between 2006 and 2020. A total of 19,495 does had completed their productive life while 6227 (24.2%) does had censored information. The pedigree contained information on 56,901 animals. The average censoring age and average failure age after first kidding for LPL were 36 and 47 months respectively. The model included, as time-independent effects, the age at first kidding and the interaction between herd, year and season of birth of the doe, and as time-dependent effects, the age at kidding, the interaction between herd, year and season of kidding, the within-herd class of milk production deviation, and the interaction between the lactation number and the stage of lactation. All fixed effects had a significant effect on LPL (p < 0.05). Does with older ages at the first kidding and an earlier age at kidding were at higher risk of being culled. A large difference among herds was observed in terms of culling risk, which highlighted the importance of adequate management practices. Also, high-producing does were less likely to be culled. The estimate of the additive genetic variance was 1.844 (in genetic standard deviation), with a heritability estimate of 0.58 ± 0.012. The results of this study are expected to contribute to the development of a genetic model for genetic evaluation of the length of the productive life of Spanish dairy goat breeds.

DETERMINATION OF CORNEAL POWER AFTER REFRACTIVE SURGERY WITH EXCIMER LASER: A CONCISE REVIEW

Refractive surgery with excimer laser has been a very common surgical procedure worldwide during the last decades. Currently, patients who underwent refractive surgery years ago are older, with a growing number of them now needing cataract surgery. To establish the power of the intraocular lens to be implanted in these patients, it is essential to define the true corneal power. However, since the refractive surgery modified the anterior, but not the posterior surface of the cornea, the determination of the corneal power in this group of patients is challenging. This article reviews the different sources of error in finding the true corneal power in these cases, and comments on several approaches, including the clinical history method as described originally by Holladay, and a modified version of it, as well as new alternatives based on corneal tomography, using devices that are able to measure the actual anterior and posterior corneal curvatures, which have emerged in recent years to address this issue.

Determination of Corneal Power after Refractive Surgery with Excimer Laser: A Concise Review

Refractive surgery with excimer laser has been a very common surgical procedure worldwide during the last decades. Currently, patients who underwent refractive surgery years ago are older, with a growing number of them now needing cataract surgery. To establish the power of the intraocular lens to be implanted in these patients, it is essential to define the true corneal power. However, since the refractive surgery modified the anterior, but not the posterior surface of the cornea, the determination of the corneal power in this group of patients is challenging. This article reviews the different sources of error in finding the true corneal power in these cases, and comments on several approaches, including the clinical history method as described originally by Holladay, and a modified version of it, as well as new alternatives based on corneal tomography, using devices that are able to measure the actual anterior and posterior corneal curvatures, which have emerged in recent years to address this issue.

DETERMINATION OF CORNEAL POWER AFTER REFRACTIVE SURGERY WITH EXCIMER LASER: A CONCISE REVIEW

Refractive surgery with excimer laser has been a very common surgical procedure worldwide during the last decades. Currently, patients who underwent refractive surgery years ago are older, with a growing number of them now needing cataract surgery. To establish the power of the intraocular lens to be implanted in these patients, it is essential to define the true corneal power. However, since the refractive surgery modified the anterior, but not the posterior surface of the cornea, the determination of the corneal power in this group of patients is challenging. This article reviews the different sources of error in finding the true corneal power in these cases, and comments on several approaches, including the clinical history method as described originally by Holladay, and a modified version of it, as well as new alternatives based on corneal tomography, using devices that are able to measure the actual anterior and posterior corneal curvatures, which have emerged in recent years to address this issue.

Unusual Magnetic Hysteresis and Transition between Vortex and Double Pole States Arising from Interlayer Coupling in Diamond-Shaped Nanostructures

Controlling the magnetic ground states at the nanoscale is a long-standing basic research problem and an important issue in magnetic storage technologies. Here, we designed a nanostructured material that exhibits very unusual hysteresis loops due to a transition between vortex and double pole states. Arrays of 700 nm diamond-shaped nanodots consisting of Py(30 nm)/Ru(t_Ru)/Py(30 nm) (Py, permalloy (Ni₈₀Fe₂₀)) trilayers were fabricated by interference lithography and e-beam evaporation. We show that varying the Ru interlayer spacer thickness (t_Ru) governs the interaction between the Py layers. We found this interaction mainly mediated by two mechanisms: magnetostatic interaction that favors antiparallel (antiferromagnetic, AFM) alignment of the Py layers and exchange interaction that oscillates between ferromagnetic (FM) and AFM couplings. For a certain range of Ru thicknesses, FM coupling dominates and forms magnetic vortices in the upper and lower Py layers. For Ru thicknesses at which AFM coupling dominates, the magnetic state in remanence is a double pole structure. Our results showed that the interlayer exchange coupling interaction remains finite even at 4 nm Ru thickness. The magnetic states in remanence, observed by magnetic force microscopy (MFM), are in good agreement with corresponding hysteresis loops obtained by the magneto-optic Kerr effect (MOKE) and micromagnetic simulations.

Identification of new variants and candidate genes in women with familial premature ovarian insufficiency using whole-exome sequencing

PURPOSE

To identify candidate variants in genes possibly associated with premature ovarian insufficiency (POI).

METHODS

Fourteen women, from 7 families, affected by idiopathic POI were included. Additionally, 98 oocyte donors of the same ethnicity were enrolled as a control group. Whole-exome sequencing (WES) was performed in 14 women with POI to identify possibly pathogenic variants in genes potentially associated with the ovarian function. The candidate genes selected in POI patients were analysed within the exome results of oocyte donors.

RESULTS

After the variant filtering in the WES analysis of 7 POI families, 23 possibly damaging genetic variants were identified in 22 genes related to POI or linked to ovarian physiology. All variants were heterozygous and five of the seven families carried two or more variants in different genes. We have described genes that have never been associated to POI pathology; however, they are involved in important biological processes for ovarian function. In the 98 oocyte donors of the control group, we found no potentially pathogenic variants among the 22 candidate genes.

CONCLUSION

WES has previously shown as an efficient tool to identify causative genes for ovarian failure. Although some studies have focused on it, and many genes are identified, this study proposes new candidate genes and variants, having potentially moderate/strong functional effects, associated with POI, and argues for a polygenic etiology of POI in some cases.

Application of machine learning to predict aneuploidy and mosaicism in embryos from in vitro fertilization (IVF) cycles

BACKGROUND

OBJECTIVE

STUDY DESIGN

RESULTS

CONCLUSION

P-370 The vaginal microbiome in the first trimester of pregnancy is different in spontaneous versus IVF gestation

Study question

Are there differences in the vaginal microbiome of pregnant women who had a spontaneous pregnancy compared to those who required IVF?

Summary answer

The composition of the vaginal microbiome at 12 week's gestation is different in women who achieve the pregnancy spontaneously or by IVF.

What is known already

The vaginal microbiome plays an important role in women's reproductive health, finding associations between different microbiome patterns and the presence of infertility and embryo implantation failure in IVF. Additionally, recent studies show a correlation between obstetrics and perinatal outcomes and the composition of vaginal microbiota in pregnant women, as well as an increased risk of obstetrics complications in pregnant women after IVF.

Study design, size, duration

Observational, prospective and multicentre study. A total of 64 women were enrolled between January 2020 and June 2021. Spontaneous pregnancies n = 30; and IVF pregnancies n = 34.

Participants/materials, setting, methods

Vaginal swabs were obtained by speculum exam at 12 weeks of gestation in two public hospitals and a fertility private clinic in Spain, to evaluate the differences in vaginal microbiome between both cohorts. The microbiome composition was analyzed by sequencing the V3-V4 region of the 16S rRNA on the Illumina MiSeq platform.

Main results and the role of chance

There were no significant differences in socio-demographic characteristics between groups, except for an expected higher maternal age in the IVF cohort.

Lactobacillus was the most prevalent genus in both groups. When we compared the beta diversity of vaginal microbial by cohort a significant difference was obtained (p = 0.001).

Gardenella, Neisseria, Prevotella and Staphyloccocus were significantly enriched in the IVF group (p = 0.01).

A further evaluation of the four most abundant Lactobacillus species showed that Lactobacillus iners was dominant in IVF pregnancies (15.2%) compared to spontaneous (9.8%) (p = 0.002). On the other hand, Lactobacillus  gasseri showed a lower abundance in vaginal microbiome from women belonged to IVF (9.2%) vs spontaneous pregnant group (13.8%) (p = 0.005).

These findings allowed us to create a model to identify a microbial signature. This model is able to discriminate between IVF and spontaneous pregnancies.

Limitations, reasons for caution

The main limitation of our study is the small sample size. Larger studies are needed to corroborate our findings and their relationship with important aspects such as obstetric and perinatal complications.

Wider implications of the findings

The microbiome composition is different between both cohorts. The microbiome found in our IVF cohort has been also associated with obstetric complications as preterm delivery in previous studies. This suggest that the microbiome composition could be a plausible etiology for a higher risk of adverse pregnancy outcomes in IVF patients.

Trial registration number

Not applicable

O-025 Factors affecting biochemical pregnancy: Machine learning-assisted identification

Study question

What variables in a PGT-A cycle can influence biochemical pregnancy loss?

Summary answer

There are paternal, maternal, ovarian stimulation, endometrial and embryo biopsy factors that are associated with the rate of biochemical pregnancy after the euploid embryo transfer.

What is known already

Biochemical miscarriage is an early termination in the development of pregnancy. Embryonic chromosomal alterations have been proposed to cause biochemical pregnancy. However, even though euploid embryos are transferred in PGT-A cycles, biochemical pregnancy rates do not seem to be modified, so there must be other factors associated with this type of miscarriage.

The classical-statistical methods used to establish the factors related to biochemical miscarriage have produced contradictory results and there is no unanimity in the literature. As an alternative to traditional methods, different artificial intelligence algorithms are being used for the analysis of biological data.

Study design, size, duration

The study design is observational and retrospective. A total of 5892 embryos from 1919 PGT-A cycles were considered (January-2017 to October-2021). Only transferred embryos were included in the study (n = 1161). The trophoectoderm biopsies on D5, D6 or D7 blastocysts were analysed by NGS using the Illumina platform (VeriSeq Illumina®, San Diego, CA, USA). The biopsied embryos were vitrified and transferred in a subsequent cycle.

Participants/materials, setting, methods

Indications for PGT-A were advanced maternal age, altered karyotype or sperm FISH, history of chromosomal abnormalities in the offspring, repeated miscarriages and recurrent implantation failures.

Clinical outcomes were recorded in a database including additional potential factors (n = 48) associated with biochemical pregnancy and related to progenitors, embryos and their biopsy, ovarian stimulation and adjuvant treatments.

The association between the different variables and biochemical pregnancy was analysed using SPSS (v20.0) and R (v. 4.0.5) statistical software.

Main results and the role of chance

In order to determine which factors might increase biochemical pregnancy rates in euploid embryos, a multivariate analysis using logistic regression was initially performed. In the best predictive model (AUC=0.659) with a lower AIC (Akaike information criterion) value, only 3 factors showed a statistically significant association: uterine alterations (OR = 4.88, 95% CI [1.65-12.64]), day of embryo biopsy (OR = 2.19, 95% CI [1.46-3.31]) and mosaicism (number of altered chromosomes: OR = 1.59, 95% CI [1.10-2.22]) which significantly increased the risk of biochemical pregnancy.

To identify other variables that might modify biochemical pregnancy rates and could be missed by classic statistical methods, different types of machine learning algorithms were used: unsupervised model (cluster analysis) and supervised predictive models (support vector machines (AUC=0.845), k-nearest neighbors (AUC=0.858), random forest (AUC=0.853), neural networks multilayer (AUC=0.719) and gradient boosting (AUC=0.825).

The variables that had the greatest predictive power in the different machine learning algorithms were the variables associated with the embryo biopsy (day, number of laser pulses and biopsied cells), endometrial thickness and variables related to the male factor (sperm aneuploidy and DNA fragmentation). These algorithms apply different methodologies, but all agree on the fundamental role of these variables.

Limitations, reasons for caution

To confirm that the new identified variables are associated with biochemical pregnancy, it would be necessary to carry out prospective studies.

Wider implications of the findings

Biochemical pregnancy is the least studied clinical outcome in IVF. Knowledge of the variables that could affect biochemical pregnancy may be relevant as it may be a target for new therapies to reduce biochemical pregnancy rates and thus increase success rates.

Trial registration number

Not Applicable

P-565 Pharmacogenetic (PGx) Gene-Drug Association in IVF: clinical relevance of a panel test for ovarian stimulation

Study question

Could the PGx approach be useful for increasing the number of mature oocytes after personalized COS?

Summary answer

There was an increase in the number of MII in the cycle after the PGx implementation compared to the previous cycle.

What is known already

Pharmacogenetics (PGx) is the study of variability in drug responses associated with genetic differences amongst individuals. There is a growing evidence-based indications for PGx testing, but the implications of PGx test results for individual patients poses the next challenge. An efficient controlled ovarian stimulation (COS) is essential for IVF, as its success is tightly related to the oocytes retrieved. PGx for COS may provide an alternative approach to predict ovarian response, as it may help to understand the unexpected response and design a personalized therapy. We evaluated the application and clinical impact of pharmacogenetic test for ovarian response to COS.

Study design, size, duration

We conducted an observational multicentric cohort study that evaluated the results of a PGx panel test and their implementation for personalized COS between June 2016 and November 2021. The primary outcome was the number of mature oocytes in the cycle after the PGx management compared with the previous cycle without PGx approach. PGx panel test includes the analysis of S680N in the FSHR gene and CAG repeats in exon 1 in AR gene.

Participants/materials, setting, methods

We included 228 patients who underwent PGx testing previous COS and a preceding COS without PGx approach. In total 549 cycles were included. For the cycle preceding to PGx test (C0-cycle), patients followed a COS protocol according to their clinical characteristic. For the cycle using PGx approach (C1-cycle) the gonadotrophin and doses were selected according to the polymorphism S680N in FSHR gene and an androgen pretreatment regarding to the number of repeats in AR gene.

Main results and the role of chance

Clinical characteristics of patients were measured. The median and IQR of age, AMH and number of antral follicle count of the patient included in the study were 39.1y [36.4-41.4], 0.72pmol/L [0.38-1.19] and 5 [4-8], respectively. These characteristics agree with the Bologna criteria for poor ovarian reserve. The mean duration of stimulation and total dose of gonadotrophins required were similar between C0 and C1 cycles (9.25 + 2.59 vs 9.15 + 3.68, p = 0.62; 2885 + 1383 vs 2645 + 1352, p = 0.16). Differences were shown in the female age 38.4 + 4.1y in C0 vs 39.1 + 4.1y in C1 (p &lt; 0.0001). Patients in C1 were older than their previous cycle C0. This difference is in favour of better ovarian stimulation outcome in the first cycle where patients were younger. Statistical differences were shown in MII yield (3.1 + 2.2 vs 4.2 + 3.2; p &lt; 0.001). Regarding the differences observed in the COS outcome among the different genotypes and PGx interventions, all the patients showed a clear benefit of PGx. On the other hand, for patients that carried a number of repeats lower than 22 and higher than 24 in AR gene and NN genotype for 680-FSHR, to which no PGx intervention has to be done according to the test result, no significances differences were reported (3.60 vs 4.22; p = 0.33).

Limitations, reasons for caution

A small sample size and the inherent limitations of an observational study. A clinical randomized trial will be necessary to draw firm conclusions. More research in the genes involved in ovarian function is warranted.

Wider implications of the findings

This project represents the first effort to investigate whether a PGx test could improve COS outcomes in POR cohort. Our results suggest that PGx test could benefit the process of controlled ovarian stimulation towards a true individualized approach in clinical practice.

Trial registration number

Not applicable

P-024 Identification of spermatogenic infertility phenotypes using next generation sequencing

Study question

Can next generation sequencing (NGS) contribute to diagnoses male idiopathic infertility?

Summary answer

A male factor gene panel identifies pathogenic variants associated to spermatogenic failure in oligozoospermia and cryptozoospermia patients.

What is known already

In 50% of cases, infertility is due to a male factor problem. Although the causes of male infertility are heterogeneous, genetic causes account for approximately 30% of cases. Some phenotypes have been associated with specific genetic disorders such as chromosomal abnormalities and chromosome Y microdeletions. However, current genetic studies explain only 4% of cases, whilst most cases of male factor infertility remain without a clear diagnosis. Therefore, new techniques that explain the cause of male infertility are needed. Advances in NGS allowed us to study a large number of genes involved in spermatogenesis process in patients with idiopathic infertility.

Study design, size, duration

A retrospective study was performed from July 2020 until May 2021. A total of 30 patients with abnormal seminal count parameters (oligozoospermic and cryptozoospermic) were included in the male factor gene panel study. Patients carrying Y-chromosome microdeletions or abnormal karyotype were excluded. The control group included 20 normozoospermic healthy donors selected on the basis of normal semen parameters according to the WHO criteria (2010).

Participants/materials, setting, methods

Genomic DNA extraction from blood-EDTA of the patients was performed using the commercial MagMax DNA MultiSample Ultra kit and the King-Fisher automated extractor (ThermoFisher®). Next Generation Sequencing (NGS) was done using a panel with 426 genes involved in the spermatogenesis process. Panel sequencing for identification of genetic variants was performed using Nextera Enrichment technology (Illumina®). FASTAQ data were processed using BWA and GATK algorithms. VCF files were analyzed using Variant Interpreter software.

Main results and the role of chance

After data analysis, we observed that eight of the thirty patients studied were carriers of mutations in least one of the genes included in the panel (8/30, 26.7%). We identified the following pathogenic variants: a missense mutation (Phe1052Val) and a deletion (Phe508del) of CFTR gene (2/30, 6.6%), two frameshifts (Asp128GlufsTer34 and Lys1299Ter) of CEP290 (2/30, 6.6%), a missense mutation (Tyr284Cys) of GNRHR gene (1/30, 3.3%), a missense mutation (Tyr416Cys) of SCN5A gene (1/30, 3.3%), a deletion (Ser83del) of NANOS1 gene (1/30, 3.3%), a stop gained in splice region Arg341Ter of TEX14 gene (1/30, 3.3%), a splicing donor c.362 + 2T&gt;C of ESR2 gene (1/30, 3.3%) and a missense mutation (Ser321Leu) of DNAH5 gene (1/30, 3.3%), which are related to spermatogenesis failure. Additionally, some variants classified as benign have been identified, which are not associated with pathogenicity. All the variants identified are related with male infertility, affecting spermatogenesis process, such as congenital bilateral absence of the vas deferens (CFTR), reproductive system syndrome (CEP190), endocrine disorder (GNRHR, hypogonadotropic hypogonadism), testis expressed (SCN5A), spermatogenic failure (NANOS1, TEX14 and ESR2) and syndromic infertility (DNAH5). Nevertheless, no pathogenic mutations associated to spermatogenic failure were observed in the control group.

Limitations, reasons for caution

The main limitation of this study is the small number of patients included. Further studies including a higher number of males with idiopathic infertility are warranted to confidently link the genetic variants included in our gene panel to spermatogenic failure.

Wider implications of the findings

The gene list included in our panel represents a step-forward in the diagnosis screening of males with altered sperm parameters. Our results may add in the knowledge of male factor infertility in order to provide etiologic factors towards a personalized treatment and adequate genetic counselling.

Trial registration number

Not applicable

P-532 Embryo aneuploidy risk is increased in couples with unexplained infertility

Study question

Are chromosomal abnormalities (aneuploidy and mosaicism) increased in couples with unexplained infertility?

Summary answer

Couples with unexplained infertility show higher rates of embryo aneuploidy compared to IVF with donor sperm cycles.

What is known already

Aneuploidy is the most common genetic abnormality found in early embryos. Although there is strong evidence about the correlation between oocyte age and aneuploidy rates, the potential contribution of additional female and male factor warrants further elucidation.

Unexplained infertility is a diagnosed of exclusion affecting ∼30% of couples seeking infertility care. Recent medical evidence suggests that these couples have lower odds of having a live birth compared to their counterparts using donor sperm. Therefore, the aim of this study was to elucidate whether chromosomal abnormalities (aneuploidy and mosaicism) were increased in couples with unexplained infertility.

Study design, size, duration

Retrospective analysis of the chromosomic evaluation of 700 embryos coming from 220 IVF/PGT-A cycles (March 2017 - September 2021) performed in a private fertility center. The comprehensive chromosome screening included testing for aneuploidy and mosaicism. In addition, whole and segmental chromosomal alterations were also identified and reported.

Participants/materials, setting, methods

Participants were divided into two groups: couples with unexplained infertility (study group) and women undergoing IVF using donated sperm (control group). Only normospermic and normal sperm FISH samples were included. The Veriseq NGS (Illumina) platform was employed for PGT-A testing.

An SPSSv20.0 logistic regression analysis was performed for aneuploidy and mosaicism rate. The resulted odds ratio was then adjusted to account for: female/male age, previous implantation failure, recurrent pregnancy loss, previous chromosomopathies and embryo quality.

Main results and the role of chance

A total of 220 PGT-A cycles were included in the analysis (study group n = 94 vs control group n = 126) comprising 700 embryos (study group n = 313 vs control group n = 387). The female age was 38.17 ± 3.6 vs 40.08 ± 2.4 and the male age was 40.57 ± 5.0 and 25.37 ± 3.8, in the study vs control groups, respectively.

Unexplained infertility couples showed a higher risk for generating aneuploid embryos compared to IVF with donor sperm cycles [OR = 2.33 IC 95% (1.11-5.00)]. In addition, whole chromosomal alterations [OR = 2.11 IC 95% (1.00-4.44)] as well as segmental chromosomal alterations rate [OR = 1.38 IC 95% (0.49-3.86)], were higher in unexplained infertility couples, but without reaching statistical significance.

Regarding to mosaicism rate, no significant differences were found between groups: overall [OR = 0.74 IC 95% (0.30-1.83)], whole chromosome [OR = 0.92 IC 95% (0.35-2.46)] and segmental chromosomal [OR = 0.36 IC95% (0.10-1.34)] mosaicism.

Limitations, reasons for caution

The inherent limitations of a retrospective analysis. Additional studies are warranted to clarify the potential factors explaining the higher embryo aneuploidy risk in this sub-set of patients.

Wider implications of the findings

Our data suggest an increased risk for embryo aneuploidy in unexplained infertility couples undergoing ART. Since the treatment for these couples is largely empirical, our results emphasize the importance of PGT-A analysis as a potential strategy for unexplained infertility patients.

Trial registration number

Not applicable

P-520 Factors associated with embryonic mosaicism: a systematic review and meta-analysis

Study question

What factors are involved in chromosomal mosaicism in human blastocysts?

Summary answer

Progenitors’ age and embryo biopsy day are associated with mosaicism rate.

What is known already

Chromosomal abnormalities are common in embryos analyzed in preimplantation genetic testing for aneuploidy (PGT-A) cycles. Mosaicism is a usual event in embryos derived from IVF cycles.

With the development of Next-Generation Sequencing (NGS) techniques, the ability to detect mosaicism in embryos has been improved.

Several studies show that mosaic embryos have reduced potential to reach term compared to euploid. Furthermore, the existing scientific evidence regarding the cause of embryonic mosaicism is scarce with conclusions generating considerable controversy.

Study design, size, duration

A systematic review and meta-analysis were conducted following the PRISMA guidelines on Medline and Google Scholar (January 2016 to December 2021).

Studies addressing factors associated with embryo mosaicism were comprehensively analyzed. As inclusion criteria: mosaicism should have been detected from a blastocyst trophectoderm biopsy on day 5,6 o 7 and analyzed by NGS.

Embryo quality, maternal and paternal age, day of biopsy and seminal quality were the outcomes variables included for analysis.

Participants/materials, setting, methods

A comprehensive database search resulted in 195 articles, 18 of which were included for abstract reading. Search, screen, and data extraction were performed by two reviewers independently based on inclusion criteria.

The study by meta-analysis of the effect of the different factors associated with embryonic mosaicism was carried out using the inverse variance method. Depending on the existence of heterogeneity between studies, the fixed effects method or the random effects method were used.

Main results and the role of chance

After critically and thoroughly reading the selected papers, 10 of them were included in the meta-analysis. Data from our reproductive clinic were also enclosed in the analysis (2513 cycles, 7242 embryos).

The results of the meta-analysis show that neither embryo quality nor seminal quality (male factor) were related to mosaic embryo rate (OR: 1.15; 95%CI: 0.98-1.35 and OR: 1.01; 95%CI: 0.80-1.27, respectively).

In contrast, a positive association with embryo mosaicism was observed for the variable “biopsy day” (OR: 1.06; 95% CI: 1.01-1.11): in embryos biopsied on day 6 or 7 of embryonic development, a small increase in the mosaicism rate was observed, in comparison with day 5. A significative positive association was also observed when we studied “paternal age” factor (OR: 1.13; 95% CI: 1.02-1.26): embryo mosaicism increases with paternal age.

On the other hand, maternal age showed a negative association with mosaicism (OR: 0.84; 95% CI: 0.74-0.95). Interestingly, in opposite to what happens with the aneuploidy rate, embryo mosaicism is higher in young women.

Limitations, reasons for caution

The main limitation is the low number of papers analyzed in the meta-analysis. Limitations also include the retrospective design and heterogeneity of studies, limiting comparison and pooling of data. Nonetheless, our conclusions were based on studies with low risk of bias.

Wider implications of the findings

Our result, combined with the body of medical evidence available suggest that embryo mosaicism rate is influenced by trophectoderm biopsy day and maternal and paternal age. This information will add in the knowledge for elucidating the uncertainties surrounding the factors by which mosaicism is generated in embryos.

Trial registration number

Not applicable

Identification of vaginal microbiome associated with IVF pregnancy

The factors that cause a preterm birth (PTB) are not completely understood up to date. Moreover, PTB is more common in pregnancies achieved by in-vitro fertilization (IVF) than in spontaneous pregnancies. Our aim was to compare the composition of vaginal microbiome at 12 weeks of gestation between women who conceived naturally or through IVF in order to study whether IVF PTB-risk could be related to vaginal microbiome composition. We performed an observational, prospective and multicentre study among two public hospitals and a fertility private clinic in Spain. Vaginal swabs from 64 pregnant women at 12 weeks of gestation were collected to analyse the microbiome composition by sequencing the V3-V4 region of the 16S rRNA. Our results showed that the vaginal microbiome signature at 12 weeks of pregnancy was different from women who conceived naturally or through IVF. The beta diversity and the genus composition were different between both cohorts. Gardnerella, Neisseria, Prevotella, and Staphylococcus genus were enriched genus in the vaginal microbiome from the IVF group, allowing us to create a balance model to predict both cohorts. Moreover, at species level the L. iners abundance was higher and L. gasseri was lower in the IVF group. As a conclusion, our findings were consistent with a proposed framework in which IVF pregnancy are related to risk for preterm birth (PTB) suggesting vaginal microbiome could be the reason to the relation between IVF pregnancy and risk for PTB.

The effect of the Robertsonian translocation 1/29 on the fertility of beef cattle reared under extensive conditions: a 30 years retrospective study

The Robertsonian translocation 1/29 (rob(1;29)) is the most worldwide widespread chromosomal abnormality in domestic animals. Previous studies have demonstrated its negative effect on fertility in dairy herds, but not in beef cattle extensively bred. In this study, we analyzed the effect of rob(1;29) in a Retinta cattle breed dataset gathered during the last 30 years. The data presented herein includes rob(1;29) analysis of 11,505 cows from 251 herds, pedigree information of 24,790 animals, and 67,457 calving records. Fertility was evaluated using estimated breeding values for the reproductive efficiency (Re), calculated as the percentage ratio between the number of calvings of an individual with the number expected in an optimal situation. Our results showed that cows carrying the heterozygote genotype showed a significant decrease in their Re (-5.10%, p<0.001). No decrease was detected in free rob(1;29) animals and homozygous carriers. In addition, the incidence of rob(1;29) in the breed fertility was decreased to very low values after 30 years of avoiding selection bulls carrier as stallions. The effect of rob(1;29) in cattle fertility is only significant when the prevalence of carrier individuals is high. Selecting against the disease only by the paternal side reduced the incidence to negligible values.

O-203 Application of machine learning to predict aneuploidy and mosaicism in embryos from in vitro fertilization (IVF) cycles

Study question

Is it possible to predict the likelihood of an IVF embryo being aneuploid and/or mosaic using a machine learning algorithm?

Summary answer

There are paternal, maternal, embryonic and IVF-cycle factors that are associated with embryonic chromosomal status that can be used as predictors in machine learning models.

What is known already

The factors associated with embryonic aneuploidy have been extensively studied. Mostly maternal age and to a lesser extent male factor and ovarian stimulation have been related to the occurrence of chromosomal alterations in the embryo.

On the other hand, the main factors that may increase the incidence of embryo mosaicism have not yet been established.

The models obtained using classical statistical methods to predict embryonic aneuploidy and mosaicism are not of high reliability. As an alternative to traditional methods, different machine and deep learning algorithms are being used to generate predictive models in different areas of medicine, including human reproduction.

Study design, size, duration

The study design is observational and retrospective. A total of 4654 embryos from 1558 PGT-A cycles were included (January-2017 to December-2020). The trophoectoderm biopsies on D5, D6 or D7 blastocysts were analysed by NGS. Embryos with ≤25% aneuploid cells were considered euploid, between 25-50% were classified as mosaic and aneuploid with &gt;50%.

The variables of the PGT-A were recorded in a database from which predictive models of embryonic aneuploidy and mosaicism were developed.

Participants/materials, setting, methods

The main indications for PGT-A were advanced maternal age, abnormal sperm FISH and recurrent miscarriage or implantation failure. Embryo analysis were performed using Veriseq-NGS (Illumina).

The software used to carry out all the analysis was R (RStudio). The library used to implement the different algorithms was caret. In the machine learning models, 22 predictor variables were introduced, which can be classified into 4 categories: maternal, paternal, embryonic and those specific to the IVF cycle.

Main results and the role of chance

The different couple, embryo and stimulation cycle variables were recorded in a database (22 predictor variables). Two different predictive models were performed, one for aneuploidy and the other for mosaicism. The predictor variable was of multi-class type since it included the segmental and whole chromosome alteration categories.

The dataframe were first preprocessed and the different classes to be predicted were balanced. A 80% of the data were used for training the model and 20% were reserved for further testing. The classification algorithms applied include multinomial regression, neural networks, support vector machines, neighborhood-based methods, classification trees, gradient boosting, ensemble methods, Bayesian and discriminant analysis-based methods. The algorithms were optimized by minimizing the Log_Loss that measures accuracy but penalizing misclassifications.

The best predictive models were achieved with the XG-Boost and random forest algorithms. The AUC of the predictive model

for aneuploidy was 80.8% (Log_Loss

1.028) and for mosaicism 84.1% (Log_Loss: 0.929). The best predictor variables of the models were maternal age, embryo quality, day of biopsy and whether or not the couple had a history of pregnancies with chromosomopathies. The male factor only played a relevant role in the mosaicism model but not in the aneuploidy model.

Limitations, reasons for caution

Although the predictive models obtained can be very useful to know the probabilities of achieving euploid embryos in an IVF cycle, increasing the sample size and including additional variables could improve the models and thus increase their predictive capacity.

Wider implications of the findings

Machine learning can be a very useful tool in reproductive medicine since it can allow the determination of factors associated with embryonic aneuploidies and mosaicism in order to establish a predictive model for both. To identify couples at risk of embryo aneuploidy/mosaicism could benefit them of the use of PGT-A.

Trial registration number

Not Applicable