Epigenetic risks related to assisted reproductive technologies: epigenetics, imprinting, ART and icebergs?

A DNA Methylation Perspective on Infertility

Infertility affects a significant number of couples worldwide and its incidence is increasing. While assisted reproductive technologies (ART) have revolutionized the treatment landscape of infertility, a significant number of couples present with an idiopathic cause for their infertility, hindering effective management. Profiling the genome and transcriptome of infertile men and women has revealed abnormal gene expression. Epigenetic modifications, which comprise dynamic processes that can transduce environmental signals into gene expression changes, may explain these findings. Indeed, aberrant DNA methylation has been widely characterized as a cause of abnormal sperm and oocyte gene expression with potentially deleterious consequences on fertilization and pregnancy outcomes. This review aims to provide a concise overview of male and female infertility through the lens of DNA methylation alterations.

Molecular characterisation of 36 multilocus imprinting disturbance (MLID) patients: a comprehensive approach

BACKGROUND

Imprinting disorders (ImpDis) comprise diseases which are caused by aberrant regulation of monoallelically and parent-of-origin-dependent expressed genes. A characteristic molecular change in ImpDis patients is aberrant methylation signatures at disease-specific loci, without an obvious DNA change at the specific differentially methylated region (DMR). However, there is a growing number of reports on multilocus imprinting disturbances (MLIDs), i.e. aberrant methylation at different DMRs in the same patient. These MLIDs account for a significant number of patients with specific ImpDis, and several reports indicate a central role of pathogenic maternal effect variants in their aetiology by affecting the maturation of the oocyte and the early embryo. Though several studies on the prevalence and the molecular causes of MLID have been conducted, homogeneous datasets comprising both genomic and methylation data are still lacking.

RESULTS

Based on a cohort of 36 MLID patients, we here present both methylation data obtained from next-generation sequencing (NGS, ImprintSeq) approaches and whole-exome sequencing (WES). The compilation of methylation data did not reveal a disease-specific MLID episignature, and a predisposition for the phenotypic modification was not obvious as well. In fact, this lack of epigenotype-phenotype correlation might be related to the mosaic distribution of imprinting defects and their functional relevance in specific tissues.

CONCLUSIONS

Due to the higher sensitivity of NGS-based approaches, we suggest that ImprintSeq might be offered at reference centres in case of ImpDis patients with unusual phenotypes but MLID negative by conventional tests. By WES, additional MLID causes than the already known maternal effect variants could not be identified, neither in the patients nor in the maternal exomes. In cases with negative WES results, it is currently unclear to what extent either environmental factors or undetected genetic variants contribute to MLID.

Metabolomic Profile of Children Conceived With Medically Assisted Technologies

CONTEXT

Assisted reproductive technologies (ART) and non-in vitro fertilization fertility treatments (NIFT) are treatments for infertility. These technologies may have long-term health effects in children such as increased hypertension, glucose intolerance, and hypertriglyceridemia. Few studies have compared children born following ART and NIFT to those conceived spontaneously by subfertile couples.

OBJECTIVE

This work aimed to describe metabolic differences in children conceived by ART and NIFT compared to children conceived spontaneously by infertile couples.

METHODS

Children conceived by parent(s) receiving infertility care at the University of California, San Francisco, between 2000 and 2017 were invited to participate in the Developmental Epidemiological Study of Children born through Reproductive Technology (DESCRT). Serum metabolomic analyses were conducted using samples from 143 enrolled children (age range 4-12 years, 43% female) conceived using NIFT or ART (with fresh or frozen embryos with and without intracytoplasmic sperm injection [ICSI]) and children conceived spontaneously by subfertile couples. Principal component analysis and multivariable regression were used to compare the distribution of metabolites between groups.

RESULTS

There was no separation in metabolites based on treatment or sex. NIFT-conceived children showed no differences compared to spontaneously conceived controls. Only spontaneously conceived children had different metabolomics profiles from children conceived from fresh ART, frozen ART, and all ICSI. Pantoate and propionylglycine levels were elevated in fresh ART compared to the spontaneous group (P < .001). Propionylglycine levels were elevated in the ICSI (both fresh and frozen) vs the spontaneous group (P < .001). Finally, 5-oxoproline levels were decreased in frozen ART compared to the spontaneous group (P < .001).

CONCLUSION

NIFT-conceived children did not show any metabolic differences compared with spontaneously conceived children. The metabolic differences between ART-conceived children and children conceived spontaneously were small but unlikely to be clinically significant but should be examined in future studies.

Primary cilia: The central role in the electromagnetic field induced bone healing

Primary cilia have emerged as the cellular “antenna” that can receive and transduce extracellular chemical/physical signals, thus playing an important role in regulating cellular activities. Although the electromagnetic field (EMF) is an effective treatment for bone fractures since 1978, however, the detailed mechanisms leading to such positive effects are still unclear. Primary cilia may play a central role in receiving EMF signals, translating physical signals into biochemical information, and initiating various signalingsignaling pathways to transduce signals into the nucleus. In this review, we elucidated the process of bone healing, the structure, and function of primary cilia, as well as the application and mechanism of EMF in treating fracture healing. To comprehensively understand the process of bone healing, we used bioinformatics to analyze the molecular change and associated the results with other studies. Moreover, this review summarizedsummarized some limitations in EMFs-related research and provides an outlook for ongoing studies. In conclusion, this review illustrated the primary cilia and related molecular mechanisms in the EMF-induced bone healing process, and it may shed light on future research.

Parental methylome reprogramming in human uniparental blastocysts reveals germline memory transition

Uniparental embryos derived from only the mother (gynogenetic [GG]) or the father (androgenetic [AG]) are unique models for studying genomic imprinting and parental contributions to embryonic development. Human parthenogenetic embryos can be obtained following artificial activation of unfertilized oocytes, but the production of AG embryos by injection of two sperm into one denucleated oocyte leads to an extra centriole, resulting in multipolar spindles, abnormal cell division, and developmental defects. Here, we improved androgenote production by transferring the male pronucleus from one zygote into another haploid androgenote to prevent extra centrioles and successfully generated human diploid AG embryos capable of developing into blastocysts with an identifiable inner cell mass (ICM) and trophectoderm (TE). The GG embryos were also generated. The zygotic genome was successfully activated in both the AG and GG embryos. DNA methylome analysis showed that the GG blastocysts partially retain the oocyte transcription-dependent methylation pattern, whereas the AG blastocyst methylome showed more extensive demethylation. The methylation states of most known imprinted differentially methylated regions (DMRs) were recapitulated in the AG and GG blastocysts. Novel candidate imprinted DMRs were also identified. The production of uniparental human embryos followed by transcriptome and methylome analysis is valuable for identifying parental contributions and epigenome memory transitions during early human development.

DNA methylation patterns within whole blood of adolescents born from assisted reproductive technology are not different from adolescents born from natural conception

STUDY QUESTION

Do the epigenome-wide DNA methylation profiles of adolescents born from ART differ from the epigenome of naturally conceived counterparts?

SUMMARY ANSWER

No significant differences in the DNA methylation profiles of adolescents born from ART [IVF or ICSI] were observed when compared to their naturally conceived, similar aged counterparts.

WHAT IS KNOWN ALREADY

Short-term and longer-term studies have investigated the general health outcomes of children born from IVF treatment, albeit without common agreement as to the cause and underlying mechanisms of these adverse health findings. Growing evidence suggests that the reported adverse health outcomes in IVF-born offspring might have underlying epigenetic mechanisms.

STUDY DESIGN, SIZE, DURATION

The Growing Up Healthy Study (GUHS) is a prospective study that recruited 303 adolescents and young adults, conceived through ART, to compare various long-term health outcomes and DNA methylation profiles with similar aged counterparts from Generation 2 from the Raine Study. GUHS assessments were conducted between 2013 and 2017. The effect of ART on DNA methylation levels of 231 adolescents mean age 15.96 ± 1.59 years (52.8% male) was compared to 1188 naturally conceived counterparts, 17.25 ± 0.58 years (50.9% male) from the Raine Study.

PARTICIPANTS/MATERIALS, SETTING, METHODS

DNA methylation profiles from a subset of 231 adolescents (13-19.9 years) from the GUHS, generated using the Infinium Methylation Epic Bead Chip (EPIC) array were compared to 1188 profiles from the Raine Study previously measured using the Illumina 450K array. We conducted epigenome-wide association approach (EWAS) and tested for an association between the cohorts applying Firth's bias reduced logistic regression against the outcome of ART versus naturally conceived offspring. Additionally, within the GUHS cohort, we investigated differences in methylation status in fresh versus frozen embryo transfers, cause of infertility as well as IVF versus ICSI conceived offspring. Following the EWAS analysis we investigated nominally significant probes using Gene Set Enrichment Analysis (GSEA) to identify enriched biological pathways. Finally, within GUHS we compared four estimates (Horvath, Hanuum, PhenoAge [Levine], and skin Horvath) of epigenetic age and their correlation with chronological age.

MAIN RESULTS AND THE ROLE OF CHANCE

Between the two cohorts, we did not identify any DNA methylation probes that reached a Bonferroni corrected P-value < 1.24E-0.7. When comparing IVF versus ICSI conceived adolescents within the GUHS cohort, after adjustment for participant age, sex, maternal smoking, multiple births, and batch effect, three methylation probes (cg15016734, cg26744878 and cg20233073) reached a Bonferroni correction of 6.31E-08. After correcting for cell count heterogeneity, two of the aforementioned probes remained significant and an additional two probes (cg 0331628 and cg 20235051) were identified. A general trend towards hypomethylation in the ICSI offspring was observed. All four measures of epigenetic age were highly correlated with chronological age and showed no evidence of accelerated epigenetic aging within their whole blood.

LIMITATIONS, REASONS FOR CAUTION

The small sample size coupled with the use of whole blood, where epigenetic differences may occur in other tissue. This was corrected by the utilized statistical method that accounts for imbalanced sample size between groups and adjusting for cell count heterogeneity. Only a small portion of the methylome was analysed and rare individual differences may be missed.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings provide further reassurance that the effects of the ART manipulations occurring during early embryogenesis, existing in the neonatal period are indeed of a transient nature and do not persist into adolescence. However, we have not excluded that alternative epigenetic mechanisms may be at play.

STUDY FUNDING/COMPETING INTEREST(S)

This project was supported by NHMRC project Grant no. 1042269 and R.J.H. received funding support from Ferring Pharmaceuticals Pty Ltd. R.J.H. is the Medical Director of Fertility Specialists of Western Australia and a shareholder in Western IVF. He has received educational sponsorship from Merck Sharp & Dohme Corp.- Australia, Merck-Serono Australia Pty Ltd and Ferring Pharmaceuticals Pty Ltd. P.B. is the Scientific Director of Concept Fertility Centre, Subiaco, Western Australia. J.L.Y. is the Medical Director of PIVET Medical Centre, Perth, Western Australia. The remaining authors have no conflicts of interest.

Clinical and Molecular Diagnosis of Beckwith-Wiedemann Syndrome with Single- or Multi-Locus Imprinting Disturbance

Beckwith-Wiedemann syndrome (BWS) is a clinically and genetically heterogeneous overgrowth disease. BWS is caused by (epi)genetic defects at the 11p15 chromosomal region, which harbors two clusters of imprinted genes, IGF2/H19 and CDKN1C/KCNQ1OT1, regulated by differential methylation of imprinting control regions, H19/IGF2:IG DMR and KCNQ1OT1:TSS DMR, respectively. A subset of BWS patients show multi-locus imprinting disturbances (MLID), with methylation defects extended to other imprinted genes in addition to the disease-specific locus. Specific (epi)genotype-phenotype correlations have been defined in order to help clinicians in the classification of patients and referring them to a timely diagnosis and a tailored follow-up. However, specific phenotypic correlations have not been identified among MLID patients, thus causing a debate on the usefulness of multi-locus testing in clinical diagnosis. Finally, the high incidence of BWS monozygotic twins with discordant phenotypes, the high frequency of BWS among babies conceived by assisted reproductive technologies, and the female prevalence among BWS-MLID cases provide new insights into the timing of imprint establishment during embryo development. In this review, we provide an overview on the clinical and molecular diagnosis of single- and multi-locus BWS in pre- and post-natal settings, and a comprehensive analysis of the literature in order to define possible (epi)genotype-phenotype correlations in MLID patients.

Biophysical optimization of preimplantation embryo culture: what mechanics can offer ART

Owing to the rise of ART and mounting reports of epigenetic modification associated with them, an understanding of optimal embryo culture conditions and reliable indicators of embryo quality are highly sought after. There is a growing body of evidence that mechanical biomarkers can rival embryo morphology as an early indicator of developmental potential and that biomimetic mechanical cues can promote healthy development in preimplantation embryos. This review will summarize studies that investigate the role of mechanics as both indicators and promoters of mammalian preimplantation embryo development and evaluate their potential for improving future embryo culture systems.

Specific imprinted genes demethylation in association with oocyte donor's age and culture conditions in bovine embryos assessed at day 7 and 12 post insemination

The production of bovine embryos through in vitro maturation and fertilization is an important tool of the genomic revolution in dairy cattle. Gene expression analysis of these embryos revealed differences according to the culture conditions or oocyte donor's pubertal status compared to in vivo derived embryos. We hypothesized that some of the methylation patterns in oocytes are acquired in the last step of folliculogenesis and could be influenced by the environment created in the follicles containing these oocytes. These altered patterns may not be erased during the first week of embryonic development in culture or may be sensitive to the conditions during that time. To quantify the changes related to culture conditions, an in vivo control group consisting of embryos (Day 12 post fertilization for all groups) obtained from superovulated and artificially inseminated cows was compared to in vitro produced (IVP) embryos cultured with or without Fetal Bovine Serum (FBS). To measure the effect of the oocytes donor's age, we also compared a fourth group consisting of IVP embryos produced with oocytes collected following ovarian stimulation of pre-pubertal animals. Embryonic disk and trophoblast cells were processed separately and the methylation status of ten imprinted genes (H19, MEST, KCNQ1, SNRPN, PEG3, NNAT, GNASXL, IGF2R, PEG10, and PLAGL1) was assessed by pyrosequencing. Next, ten Day 7 blastocysts were produced following the same methodology as for the D12 embryos (four groups) to observe the most interesting genes (KCNQ1, SNRPN, IGF2R and PLAGL1) at an earlier developmental stage. For all samples, we observed overall lower methylation levels and greater variability in the three in vitro groups compared to the in vivo group. The individual embryo analysis indicated that some embryos were deviant from the others and some were not affected. We concluded that IGF2R, SNRPN, and PEG10 were particularly sensitive to culture conditions and the presence of FBS, while KCNQ1 and PLAGL1 were more affected in embryos derived from pre-pubertal donors. This work provides markers at the single imprinted control region (ICR) resolution to assess the culture environment required to minimize epigenetic perturbations in bovine embryos generated by assisted reproduction techniques, thus laying the groundwork for a better comprehension of the complex interplay between in vitro conditions and imprinted genes.

DNA methylation status of bovine blastocysts obtained from peripubertal oocyte donors

In the dairy industry, the high selection pressure combined with the increased efficiency of assisted reproduction technologies (ART) are leading toward the use of younger females for reproduction purposes, with the aim to reduce the interval between generations. This situation could impair embryo quality, decreasing the success rate of the ART procedures and the values of resulting offspring. Young Holstein heifers (n = 10) were subjected to ovarian stimulation and oocyte collection at 8, 11, and 14 months of age. All the oocytes were fertilized in vitro with semen from one adult bull, generating three pools of embryos per animal. Each animal was its own control for the evaluation of the effects of age. The EmbryoGENE platform was used to compare the DNA methylation status of blastocysts obtained from oocytes collected at 8 versus 14 and 11 versus 14 months of age. Age-related contrast analysis identified 5,787 and 3,658 differentially methylated regions (DMRs) in blastocysts from heifers at 8 versus 14 and 11 versus 14 months of age, respectively. For both contrasts, the DMRs were distributed nonrandomly in the different DNA regions. The DNA from embryos from 8-month-old donors was more hypermethylated, while the DNA from embryos from 11-month-old donors displayed an intermediate phenotype. According to Ingenuity Pathway Analysis, the upstream regulator genes cellular tumor antigen p53, transforming growth factor β1, tumor necrosis factor, and hepatocyte nuclear factor 4α are particularly associated with methylation sensitive targets, which were more hypermethylated in embryos from younger donors.

Metabolic profile of in vitro derived human embryos is not affected by the mode of fertilization

The pattern of metabolism by early embryos in vitro has been linked to a range of phenotypes, including viability. However, the extent to which metabolic function of embryos is modified by specific methods used during ART has yet to be fully described. This study has sought to determine if the mode of fertilization used to create embryos affects subsequent embryo metabolism of substrates. A metabolic profile, including consumption of key substrates and the endogenous triglyceride content of individual IVF and ICSI supernumerary embryos, was assessed and compared. Embryo development and quality was also recorded. All embryos were donated at a single clinical IVF center, on Day 5, from 36 patients aged 18-38 years, The data revealed that consumption of glucose and pyruvate, and production of lactate, did not differ between embryos created by IVF or ICSI. Similarly, the mode of insemination did not impact on the triglyceride content of embryos. However, ICSI-derived embryos displayed a more active turnover of amino acids (P = 0.023), compared to IVF embryos. The specific amino acids produced in higher quantities from ICSI compared to IVF embryos were aspartate (P = 0.016), asparagine (P = 0.04), histidine (P = 0.021) and threonine (P = 0.009) while leucine consumption was significantly lower (P = 0.04). However, importantly neither individual nor collective differences in amino acid metabolism were apparent for sibling oocytes subjected to either mode of fertilization. Embryo morphology (the number of top grade embryos) and development (proportion reaching the blastocyst stage) were comparable in patients undergoing IVF and ICSI. In conclusion, the microinjection of spermatozoa into oocytes does not appear to have an impact on subsequent metabolism and viability. Observed differences in amino acid metabolism may be attributed to male factor infertility of the patients rather than the ICSI procedure per se.

The Female Response to Seminal Fluid

Seminal fluid is often assumed to have just one function in mammalian reproduction, delivering sperm to fertilize oocytes. But seminal fluid also transmits signaling agents that interact with female reproductive tissues to facilitate conception and .pregnancy. Upon seminal fluid contact, female tissues initiate a controlled inflammatory response that affects several aspects of reproductive function to ultimately maximize the chances of a male producing healthy offspring. This effect is best characterized in mice, where the female response involves several steps. Initially, seminal fluid factors cause leukocytes to infiltrate the female reproductive tract, and to selectively target and eliminate excess sperm. Other signals stimulate ovulation, induce an altered transcriptional program in female tract tissues that modulates embryo developmental programming, and initiate immune adaptations to promote receptivity to implantation and placental development. A key result is expansion of the pool of regulatory T cells that assist implantation by suppressing inflammation, mediating tolerance to male transplantation antigens, and promoting uterine vascular adaptation and placental development. Principal signaling agents in seminal fluid include prostaglandins and transforming growth factor-β. The balance of male signals affects the nature of the female response, providing a mechanism of ‟cryptic female choiceˮ that influences female reproductive investment. Male-female seminal fluid signaling is evident in all mammalian species investigated including human, and effects of seminal fluid in invertebrates indicate evolutionarily conserved mechanisms. Understanding the female response to seminal fluid will shed new light on infertility and pregnancy disorders and is critical to defining how events at conception influence offspring health.

DNA methylation and mRNA expression of imprinted genes in blastocysts derived from an improved in vitro maturation method for oocytes from small antral follicles in polycystic ovary syndrome patients

STUDY QUESTION

Does imprinted DNA methylation or imprinted gene expression differ between human blastocysts from conventional ovarian stimulation (COS) and an optimized two-step IVM method (CAPA-IVM) in age-matched polycystic ovary syndrome (PCOS) patients?

SUMMARY ANSWER

No significant differences in imprinted DNA methylation and gene expression were detected between COS and CAPA-IVM blastocysts.

WHAT IS KNOWN ALREADY

Animal models have revealed alterations in DNA methylation maintenance at imprinted germline differentially methylated regions (gDMRs) after use of ARTs. This effect increases as more ART interventions are applied to oocytes or embryos. IVM is a minimal-stimulation ART with reduced hormone-related side effects and risks for patients. CAPA-IVM is an improved IVM system that includes a pre-maturation step (CAPA), followed by an IVM step, both in the presence of physiological compounds that promote oocyte developmental capacity.

STUDY DESIGN, SIZE, DURATION

For DNA methylation analysis 20 CAPA-IVM blastocysts were compared to 12 COS blastocysts. For RNA-Seq analysis a separate set of 15 CAPA-IVM blastocysts were compared to 5 COS blastocysts.

PARTICIPANTS/MATERIALS, SETTING, METHODS

COS embryos originated from 12 patients with PCOS (according to Rotterdam criteria) who underwent conventional ovarian stimulation. For CAPA-IVM 23 women were treated for 3-5 days with highly purified hMG (HP-hMG) and no hCG trigger was given before oocyte retrieval. Oocytes were first cultured in pre-maturation medium (CAPA for 24 h containing C-type natriuretic peptide), followed by an IVM step (30 h) in medium containing FSH and Amphiregulin. After ICSI, Day 5 or 6 embryos in both groups were vitrified and used for post-bisulphite adaptor tagging (PBAT) DNA methylation analysis or RNA-seq gene expression analysis of individual embryos. Data from specific genes and gDMRs were extracted from the PABT and RNA-seq datasets.

MAIN RESULTS AND THE ROLE OF CHANCE

CAPA-IVM blastocysts showed similar rates of methylation and gene expression at gDMRs compared to COS embryos. In addition, expression of major epigenetic regulators was similar between the groups.

LIMITATIONS, REASONS FOR CAUTION

The embryos from the COS group were generated in a range of culture media. The CAPA-IVM embryos were all generated using the same sperm donor. The DNA methylation level of gDMRs in purely in vivo-derived human blastocysts is not known.

WIDER IMPLICATIONS OF THE FINDINGS

A follow-up of children born after CAPA-IVM is important as it is for other new ARTs, which are generally introduced into clinical practice without prior epigenetic safety studies on human blastocysts. CAPA-IVM opens new perspectives for patient-friendly ART in PCOS.

STUDY FUNDING/COMPETING INTEREST(S)

IVM research at the Vrije Universiteit Brussel has been supported by grants from the Institute for the Promotion of Innovation by Science and Technology in Flanders (Agentschap voor Innovatie door Wetenschap en Technologie-IWT, project 110680), the Fund for Research Flanders (Fonds voor Wetenschappelijk Onderzoek-Vlaanderen-FWO-AL 679 project, project G.0343.13), the Belgian Foundation Against Cancer (HOPE project, Dossier C69Ref Nr 2016-119) and the Vrije Universiteit Brussel (IOF Project 4R-ART Nr 2042). Work in G.K.'s laboratory is supported by the UK Biotechnology and Biological Sciences Research Council and Medical Research Council. The authors have no conflicts of interest.

DMSO induces drastic changes in human cellular processes and epigenetic landscape in vitro

Though clinical trials for medical applications of dimethyl sulfoxide (DMSO) reported toxicity in the 1960s, later, the FDA classified DMSO in the safest solvent category. DMSO became widely used in many biomedical fields and biological effects were overlooked. Meanwhile, biomedical science has evolved towards sensitive high-throughput techniques and new research areas, including epigenomics and microRNAs. Considering its wide use, especially for cryopreservation and in vitro assays, we evaluated biological effect of DMSO using these technological innovations. We exposed 3D cardiac and hepatic microtissues to medium with or without 0.1% DMSO and analyzed the transcriptome, proteome and DNA methylation profiles. In both tissue types, transcriptome analysis detected >2000 differentially expressed genes affecting similar biological processes, thereby indicating consistent cross-organ actions of DMSO. Furthermore, microRNA analysis revealed large-scale deregulations of cardiac microRNAs and smaller, though still massive, effects in hepatic microtissues. Genome-wide methylation patterns also revealed tissue-specificity. While hepatic microtissues demonstrated non-significant changes, findings from cardiac microtissues suggested disruption of DNA methylation mechanisms leading to genome-wide changes. The extreme changes in microRNAs and alterations in the epigenetic landscape indicate that DMSO is not inert. Its use should be reconsidered, especially for cryopreservation of embryos and oocytes, since it may impact embryonic development.

Academic performance in adolescents aged 15-16 years born after frozen embryo transfer compared with fresh embryo transfer: a nationwide registry-based cohort study

OBJECTIVE

To assess academic performance in singletons aged 15-16 years conceived after frozen embryo transfer (FET) compared with singletons born after fresh embryo transfer (ET) in Danish cohorts born from 1995 to 2001.

DESIGN

Danish national registry-based cohort study.

SETTING

Danish national registries.

POPULATION

All 6495 singletons conceived after assisted reproductive technology (ART) treatment in Denmark from 1995 to 2001 [FET (n) = 423; fresh ET (n) = 6072].

METHODS

Mean test scores on a national standardised and international comparable grading-scale. Comparisons of test score were first made in univariate analysis (Model 1) and secondly in a multivariate linear model (Model 2) adjusting for relevant reproductive and socio-demographic covariates such as the occupational and educational level of the parents. Sensitivity analyses on FET-IVF (in vitro fertilisation) versus fresh ET-IVF and FET-ICSI (intracytoplasmic sperm injection) versus fresh ET-ICSI were made. Linear mixed models were used to account for the correlation in test scores of siblings for continuous outcome.

MAIN OUTCOME MEASURES

Mean overall test score and test score in Danish, mathematics, English, and physics/chemistry.

RESULTS

Crude and adjusted mean test scores were similar for adolescents conceived after FET compared with fresh ET. The crude mean difference was +0.11 (95% CI -0.11; 0.34), and the adjusted mean difference was +0.12 (95% CI -0.09; 0.34).

CONCLUSIONS

Adolescents conceived after FET had similar academic performance at 15-16 of years of age compared with children conceived after fresh ET.

TWEETABLE ABSTRACT

Using frozen embryos in fertility treatment does not affect school performance in Danish adolescents aged 15-16 years.

Genetic variation affecting DNA methylation and the human imprinting disorder, Beckwith-Wiedemann syndrome

Background

Beckwith-Wiedemann syndrome (BWS) is an imprinting disorder with a population frequency of approximately 1 in 10,000. The most common epigenetic defect in BWS is a loss of methylation (LOM) at the 11p15.5 imprinting centre, KCNQ1OT1 TSS-DMR, and affects 50% of cases. We hypothesised that genetic factors linked to folate metabolism may play a role in BWS predisposition via effects on methylation maintenance at KCNQ1OT1 TSS-DMR.

Results

Single nucleotide variants (SNVs) in the folate pathway affecting methylenetetrahydrofolate reductase (MTHFR), methionine synthase reductase (MTRR), 5-methyltetrahydrofolate-homocysteine S-methyltransferase (MTR), cystathionine beta-synthase (CBS) and methionine adenosyltransferase (MAT1A) were examined in 55 BWS patients with KCNQ1OT1 TSS-DMR LOM and in 100 unaffected cases. MTHFR rs1801133: C>T was more prevalent in BWS with KCNQ1OT1 TSS-DMR LOM (p < 0.017); however, the relationship was not significant when the Bonferroni correction for multiple testing was applied (significance, p = 0.0036). None of the remaining 13 SNVs were significantly different in the two populations tested. The DNMT1 locus was screened in 53 BWS cases, and three rare missense variants were identified in each of three patients: rs138841970: C>T, rs150331990: A>G and rs757460628: G>A encoding NP_001124295 p.Arg136Cys, p.His1118Arg and p.Arg1223His, respectively. These variants have population frequencies of less than 1 in 1000 and were absent from 100 control cases. Functional characterization using a hemimethylated DNA trapping assay revealed a reduced methyltransferase activity relative to wild-type DNMT1 for each variant ranging from 40 to 70% reduction in activity.

Conclusions

This study is the first to examine folate pathway genetics in BWS and to identify rare DNMT1 missense variants in affected individuals. Our data suggests that reduced DNMT1 activity could affect maintenance of methylation at KCNQ1OT1 TSS-DMR in some cases of BWS, possibly via a maternal effect in the early embryo. Larger cohort studies are warranted to further interrogate the relationship between impaired MTHFR enzymatic activity attributable to MTHFR rs1801133: C>T, dietary folate intake and BWS.

Electronic supplementary material

The online version of this article (10.1186/s13148-018-0546-4) contains supplementary material, which is available to authorized users.

The impact of specific fertility treatments on cognitive development in childhood and adolescence: a systematic review

STUDY QUESTION

Does fertility treatment influence cognitive ability in school aged children, and does the impact vary with the type of treatment?

SUMMARY ANSWER

The available high-quality evidence indicates that specific treatments may give rise to different effects on cognitive development, with certain treatments, including ICSI, associated with cognitive impairment.

WHAT IS KNOWN ALREADY

Previous reviews of the literature concerning cognitive outcomes among children conceived with medical assistance have concluded that study findings are generally 'reassuring', but limited attention has been paid to the quality of this research. In addition, no review has separately assessed the range of treatment modalities available, which vary in invasiveness, and thus, potentially, in their effects on developmental outcomes.

STUDY DESIGN, SIZE, DURATION

A systematic review was undertaken. We searched PubMed, PsycINFO and the Educational Resources Information Centre database to identify English-language studies published up until 21 November 2016.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Two authors independently reviewed identified articles, extracted data and assessed study quality. Studies were eligible if they assessed cognitive development from age 4 years or more, among children conceived with fertility treatment compared with either children conceived naturally or children born from a different type of fertility treatment. Where available, data were extracted and reported separately according to the various components of treatment (e.g. mode of fertilization, embryo freezing, etc.). Risk of bias was assessed using the Newcastle-Ottawa Scale, with a score ≥7/9 indicative of high quality.

MAIN RESULTS AND THE ROLE OF CHANCE

The search identified 861 articles, of which 35 were included. Of these, seven were rated high quality. Most studies (n = 22) were subject to selection bias, due to the exclusion of children at increased risk of cognitive impairment. Among high-quality studies, there was no difference in cognitive outcomes among children conceived with conventional IVF and those conceived naturally. Findings among high-quality studies of children conceived with ICSI were inconsistent: when compared with children conceived naturally, one study reported lower intelligence quotient (IQ; 5-7 points, on average) among ICSI children whereas the remaining two high-quality studies reported no difference between groups. Furthermore, among the three high-quality studies comparing children conceived with ICSI compared with conventional IVF, one reported a significant increase in the risk of mental retardation, one reported a small difference in IQ (3 points lower, on average) and one no difference at all. There were scant studies examining exposure to embryo freezing, or less invasive treatments such as ovulation induction without IVF/ICSI.

LIMITATION, REASONS FOR CAUTION

Most existing studies had methodological limitations including selection bias and/or failure to address confounding by family background. In addition, a meta-analysis could not be performed due to heterogeneity in the assessment of cognitive outcomes. These factors impeded our ability to synthesize the evidence and draw reliable conclusions.

WIDER IMPLICATIONS OF THE FINDINGS

The conflicting findings among studies of children conceived with ICSI require clarification, in light of the increasing use of this technique for reasons other than male-factor infertility. Further population-based studies are needed that utilize contemporary data to examine specific aspects of treatment and combinations of techniques (e.g. ICSI with frozen embryo cycles). Importantly, studies should include the complete group of children exposed to treatment.

STUDY FUNDING/COMPETING INTEREST(S)

A.R.R. is supported by a Career Development Fellowship from the National Health and Medical Research Council of Australia. L.J.M. is funded by a fellowship from the Heart Foundation of Australia. The authors declare there are no competing interests.

TRIAL REGISTRATION NUMBER

Not applicable.

Assisted Reproductive Technologies and imprinting disorders: Results of a study from a French congenital malformations registry

INTRODUCTION

Assisted Reproductive Technologies (ART) is increasingly used to help infertile couples to have children around the world. A number of studies have been published reporting an increased risk of major malformations in children born following ART, especially an increased incidence of epigenetic diseases (ED). This study aimed to assess the incidence of epigenetic diseases with affected imprinting genes in infants or children from pregnancies obtained through IVF/ICSI compared to infants or children from pregnancies obtained spontaneously.

PATIENT DATA

This is a monocentric retrospective epidemiological study based on data from a French congenital malformations registry called REMERA (Registre des Malformations en Rhône-Alpes) which exhaustively monitors all pregnancies in Rhone-Alpes region, whatever their nature of onset (spontaneous pregnancies or pregnancies from ART). This registry collects all malformations, except minor malformations (EUROCAT), and all polymalformative syndromes concerning all fetuses and children born alive or not, from 20 weeks of pregnancy (or 22 weeks of amenorrhea) and all medical termination of pregnancy whatever the term. Inclusion criteria are all diagnoses of epigenetic diseases (ED) related to parental imprinting recorded in the period January 2006 to December 2015.

METHODS

For each year, the total number of births (including stillbirths) was collected from the annual activity reports of the registry. The exhaustive number of cases of epigenetic diseases was known in the registry. Were collected the number of births resulting from ART pregnancies in the study population. This incidence of ED was compared between births from spontaneous pregnancies and those obtained through ART (IVF/ICSI) with a generalized linear model (GLM: binomial regression).

RESULTS

In total, 46 cases of epigenetic diseases were analyzed on the REMERA registry files from 2006 to 2015. 4 cases from the 46 analyzed cases were from pregnancies induced by ART. ART was a risk factor for epigenetic disease (OR = 2.9 [1.06-8.22] (p = .039)). In ART-pregnancies there were 2 diagnoses: Beckwith-Wiedemann syndrome (BWS) (3 cases out of 4) and Silver-Russell syndrome (SRS) (1 out of 4).

DISCUSSION

Infants and children obtained through IVF/ICSI appear to be related to a higher risk of epigenetic diseases compared to naturally conceived children. The perspectives of this study are to raise awareness about the creation of registries of congenital malformations and genetic and epigenetic syndromes with systematic and strict reports of all the cases on all the French territory and thus to widen this study with a bigger cohort.

Comprehensive meta-analysis reveals association between multiple imprinting disorders and conception by assisted reproductive technology

PURPOSE

To determine whether a history of conception by assisted reproductive technology (ART) is associated with occurrence of one or more imprinting disorders of either maternal or paternal origin.

METHODS

We implemented a systematic review of scholarly literature followed by comprehensive meta-analysis to quantitatively synthesize data from reports relating to use of ART to occurrence of any imprinting disorder of humans, including Beckwith-Wiedemann (BWS), Angelman (AS), Prader-Willi (PWS), and Silver-Russell (SRS) syndromes, as well as transient neonatal diabetes mellitus (TNDB) and sporadic retinoblasoma (RB).

RESULTS

The systematic review identified 13 reports presenting unique data from 23 studies that related conception following ART to occurrence of imprinting disorders. Multiple studies of four disorder were identified, for which meta-analysis yielded the following summary estimates of associations with a history of ART: AS, summary odds ratio (sOR) = 4.7 (95% confidence interval (CI) 2.6-8.5, 4 studies); BWS, sOR = 5.8 (95% CI 3.1-11.1, 8 studies); PWS, sOR = 2.2 (95% CI 1.6-3.0, 6 studies); SRS, sOR = 11.3 (95% CI 4.5-28.5, 3 studies). Only one study reported on each of TNDB and RB.

CONCLUSION

Published data reveal positive associations between history of ART conception and each of four imprinting disorders. Reasons for these associations warrant further investigation.

Epigenetic changes in preimplantation embryos subjected to laser manipulation

The advantage of using laser for assisted hatching in routine assisted reproductive technology (ART) practice is debatable. Recently, it has been shown that laser-manipulated mouse embryos had compromised genetic integrity. However, the impact of laser-assisted hatching (LAH) on the epigenetic integrity of the preimplantation embryos is not elucidated so far. Since continuous thermal stress on embryos was found to lower mRNA levels of de novo (bovine) methyl transferases in embryos, we hypothesize that thermal energy induced during LAH may alter the epigenetic signature through abnormal de novo methyl transferases (Dnmts) levels. Thus, using mouse model, we made an attempt to look into the expression of Dnmt3a and Dnmt3b in laser-manipulated embryos and their effects on global methylation. This experimental prospective study used mouse embryos from varying developmental stages (2-cell, 6-8-cell, and blastocyst) which were subjected to LAH using a 1480-nm diode laser. Two pulses of 350 μs frequency were applied to breach the zona pellucida, and then, embryos were assessed for the expression of two de novo methyl transferases (Dnmt3a and Dnmt3b) and LINE-1 (long interspersed element-1) methylation when LAH embryos developed to blastocyst stage. Results from this study have shown that blastocysts subjected to LAH at two-cell stage had significantly lower mRNA transcripts of Dnmt3a (P < 0.01) and Dnmt3b (P < 0.05) whereas LAH at six- to eight-cell and blastocyst stages did not affect the mRNA level significantly. On the other hand, LINE-1 methylation did not change significantly between LAH and control group in all the stages studied. These results suggest that two-cell-stage laser manipulation of embryos changes the mRNA level of Dnmts without affecting the global DNA methylation.

The safety of intracytoplasmic sperm injection and long-term outcomes

The pioneering of intracytoplasmic sperm injection (ICSI) approximately 25 years ago revolutionized the treatment of infertile couples. Today, ICSI remains an indispensable part of assisted reproductive treatments (ART) and has resulted in the birth of millions of babies. The 25th anniversary of ICSI marks a chronologic landmark in its evolving history. This landmark also serves as an opportunity to thoroughly appraise the safety of ICSI and analyze the long-term outcomes of ICSI-conceived children. In this review, we collate and analyze salient data accrued over the past 25 years pertaining to the long-term safety of ICSI and ICSI conceptions. We also evaluate the effects of ICSI on the perinatal outcomes, congenital malformation rates, cognitive development and reproductive health of ICSI-conceived neonates, children, adolescents and adults, respectively. In doing so, we also highlight the existence of potential confounders and biases that frequently obscure the interpretation of clinical follow-up studies.

Assisted Reproductive Techniques and Risk of Beckwith-Wiedemann Syndrome

BACKGROUND AND OBJECTIVES

The emerging association of assisted reproductive techniques (ART) with imprinting disorders represents a major issue in the scientific debate on infertility treatment and human procreation. We studied the prevalence of Beckwith-Wiedemann syndrome (BWS) in children conceived through ART to define the specific associated relative risk.

METHODS

Patients with BWS born in Piemonte, Italy, were identified and matched with the general demographic data and corresponding regional ART registry.

RESULTS

Between 2005 and 2014, live births in Piemonte were 379 872, including 7884 from ART. Thirty-eight patients with BWS were born, 7 from ART and 31 naturally conceived. BWS birth prevalence in the ART group was significantly higher than that of the naturally conceived group (1:1126 vs 1:12 254, P < .001). The absolute live birth risk in the ART group was 887.9 per 1 000 000 vs 83.3 per 1 000 000 in the naturally conceived group, providing a relative risk of 10.7 (95% confidence interval 4.7-24.2). During the 1997-2014 period, 67 patients were diagnosed with BWS out of 663 834 newborns (1:9908 live births). Nine out of the 67 BWS patients were conceived through ART (13.4%), and 8 were molecularly tested, with 4 having an imprinting center 2 loss of methylation, 2 with 11p15.5 paternal uniparental disomy, and 2 negative results.

CONCLUSIONS

ART entails a 10-fold increased risk of BWS and could be implicated in the pathogenesis of genomic events besides methylation anomalies. These data highlight the need for awareness of ART-associated health risk.

Gene expression profiling of human blastocysts from in vivo and 'rescue IVM' with or without melatonin treatment

To evaluate the effect of melatonin supplementation in maturation medium for human 'rescue IVM' and investigate differences in transcriptomic profile of blastocysts developed from oocytes matured in vitro with/without melatonin treatment and in vivo, a total of 314 GV oocytes and 320 MI oocytes were collected from 200 patients younger than 35 years old undergoing ICSI cycle. The oocytes were randomly distributed in the control group (no melatonin) and four other groups of varying melatonin concentrations (10‑11, 10‑9, 10‑7, 10‑5 mol/l). Gene profiling was performed on blastocysts developed from in vivo maturation oocytes (in vivo group), and in vitro maturation (IVM) oocytes with an optimal concentration of melatonin treatment (IVM‑anti group) or without melatonin (IVM group). The ratio of high quality blastocysts was significantly higher in the groups treated with 10‑5 mol/l melatonin compared with others groups. The large‑scale analysis of the transcriptome revealed significant differences in mRNA expression levels. In each group, nine blastocysts were selected for gene expression profiling. The differentially expressed genes were involved in cysteine and methionine metabolism, regulation of apoptotic process, mineral absorption, steroid hormone biosynthesis, Wnt signaling, p53 signaling pathway and other functions. The findings indicated that the IVM procedure may potentially affect DNA methylation and the canonical Wnt signaling pathway. Exogenous melatonin positively influenced quality of blastocysts, which may be mediated via upregulation of p53 signaling and correcting DNA methylation changes caused by 'rescue IVM'. However, this study reflected what was generally referred to as 'rescue IVM' and was not a true reflection of clinical IVM techniques. Therefore, melatonin required further investigation as a promising supplement for use in IVM.

Impacts of and interactions between environmental stress and epigenetic programming during early embryo development

The processes of assisted reproductive technologies (ART) involve a variety of interventions that impact on the oocyte and embryo. Critically, these interventions cause considerable stress and coincide with important imprinting events throughout gametogenesis, fertilisation and early embryonic development. It is now accepted that the IVM and in vitro development of gametes and embryos can perturb the natural course of development to varying degrees of severity. Altered gene expression and, more recently, imprinting disorders relating to ART have become a focused area of research. Although various hypotheses have been put forward, most research has been observational, with little attempt to discover the mechanisms and periods of sensitivity during embryo development that are influenced by the culture conditions following fertilisation. The embryo possesses innate survival factor signalling pathways, yet when an embryo is placed in culture, this signalling in response to in vitro stress becomes critically important in mitigating the effects of stresses caused by the in vitro environment. It is apparent that not all embryos possess this ability to adequately adapt to the stresses experienced in vitro, most probably due to an inadequate oocyte. It is speculated that it is important that embryos use their survival signalling mechanisms to maintain normal epigenetic programming. The seeming redundancy in the function of various survival signalling pathways would support this notion. Any invasion into the natural, highly orchestrated and dynamic process of sexual reproduction could perturb the normal progression of epigenetic programming. Therefore the source of gametes and the subsequent culture conditions of gametes and embryos are critically important and require careful attention. It is the aim of this review to highlight avenues of research to elucidate the effects of stress and the relationship with epigenetic programming. The short- and long-term health and viability of human and animal embryos derived in vitro will also be discussed.

Chapter 19 Cryopreservation Effect on Genetic Function: Neonatal Outcomes

Cryopreservation is a well-established technique commonly used in clinical practice. It is used widely for the conservation of gametes and embryos that will be used later for insemination or in vitro fertilization. However, several studies have shown that this technique can produce changes in messenger RNA levels, in the epigenome and induce DNA damage. Although the embryo has potent mechanisms for DNA repair, and molecular changes in spermatozoa are not necessarily reflected in the embryo, it is important to explore new molecular tests and diagnostic tools to design optimal cryopreservation protocols and avoid undesirable molecular alterations. This chapter describes a protocol to quantify the lesions produced by cryopreservation using a protocol previously published by Rothfuss.

Impact of DNA mismatch repair system alterations on human fertility and related treatments

DNA mismatch repair (MMR) is one of the biological pathways, which plays a critical role in DNA homeostasis, primarily by repairing base-pair mismatches and insertion/deletion loops that occur during DNA replication. MMR also takes part in other metabolic pathways and regulates cell cycle arrest. Defects in MMR are associated with genomic instability, predisposition to certain types of cancers and resistance to certain therapeutic drugs. Moreover, genetic and epigenetic alterations in the MMR system demonstrate a significant relationship with human fertility and related treatments, which helps us to understand the etiology and susceptibility of human infertility. Alterations in the MMR system may also influence the health of offspring conceived by assisted reproductive technology in humans. However, further studies are needed to explore the specific mechanisms by which the MMR system may affect human infertility. This review addresses the physiological mechanisms of the MMR system and associations between alterations of the MMR system and human fertility and related treatments, and potential effects on the next generation.

Accuracy of self-reported survey data on assisted reproductive technology treatment parameters and reproductive history

BACKGROUND

It is unknown whether data obtained from maternal self-report for assisted reproductive technology treatment parameters and reproductive history are accurate for use in research studies.

OBJECTIVES

We evaluated the accuracy of self-reported in assisted reproductive technology treatment and reproductive history from the Upstate KIDS study in comparison with clinical data reported to the Society for Assisted Reproductive Technology Clinic Outcome Reporting System.

STUDY DESIGN

Upstate KIDS maternal questionnaire data from deliveries between 2008 and 2010 were linked to data reported to Society for Assisted Reproductive Technology Clinic Outcome Reporting System. The 617 index deliveries were compared as to treatment type (frozen embryo transfer and donor egg or sperm) and use of intracytoplasmic sperm injection and assisted hatching. Use of injectable medications, self-report for assisted reproductive technology, or frozen embryo transfer prior to the index deliveries were also compared. We report agreement in which both sources had yes or both no and sensitivity of maternal report using Society for Assisted Reproductive Technology Clinic Outcome Reporting System as the gold standard. Significance was determined using χ(2) at P < 0.05.

RESULTS

Universal agreement was not reached on any parameter but was best for treatment type of frozen embryo transfer (agreement, 96%; sensitivity, 93%) and use of donor eggs (agreement, 97%; sensitivity, 82%) or sperm (agreement, 98%; sensitivity, 82%). Use of intracytoplasmic sperm injection (agreement, 78%: sensitivity, 78%) and assisted hatching (agreement, 57%; sensitivity, 38%) agreed less well with self-reported use (P < .0001). In vitro fertilization (agreement, 82%) and frozen embryo transfer (agreement, 90%) prior to the index delivery were more consistently reported than was use of injectable medication (agreement, 76%) (P < .0001).

CONCLUSION

Women accurately report in vitro fertilization treatment but are less accurate about procedures handled in the laboratory (intracytoplasmic sperm injection or assisted hatching). Clinics might better communicate with patients on the use of these procedures, and researchers should use caution when using self-reported treatment data.

Causes and Consequences of Multi-Locus Imprinting Disturbances in Humans

Eight syndromes are associated with the loss of methylation at specific imprinted loci. There has been increasing evidence that these methylation defects in patients are not isolated events occurring at a given disease-associated locus but that some of these patients may have multi-locus imprinting disturbances (MLID) affecting additional imprinted regions. With the recent advances in technology, methylation profiling has revealed that imprinted loci represent only a small fraction of the methylation differences observed between the gametes. To figure out how imprinting anomalies occur at multiple imprinted domains, we have to understand the interplay between DNA methylation and histone modifications in the process of selective imprint protection during pre-implantation reprogramming, which, if disrupted, leads to these complex imprinting disorders (IDs).

How electromagnetic fields can influence adult stem cells: positive and negative impacts

The electromagnetic field (EMF) has a great impact on our body. It has been successfully used in physiotherapy for the treatment of bone disorders and osteoarthritis, as well as for cartilage regeneration or pain reduction. Recently, EMFs have also been applied in in vitro experiments on cell/stem cell cultures. Stem cells reside in almost all tissues within the human body, where they exhibit various potential. These cells are of great importance because they control homeostasis, regeneration, and healing. Nevertheless, stem cells when become cancer stem cells, may influence the pathological condition. In this article we review the current knowledge on the effects of EMFs on human adult stem cell biology, such as proliferation, the cell cycle, or differentiation. We present the characteristics of the EMFs used in miscellaneous assays. Most research has so far been performed during osteogenic and chondrogenic differentiation of mesenchymal stem cells. It has been demonstrated that the effects of EMF stimulation depend on the intensity and frequency of the EMF and the time of exposure to it. However, other factors may affect these processes, such as growth factors, reactive oxygen species, and so forth. Exploration of this research area may enhance the development of EMF-based technologies used in medical applications and thereby improve stem cell-based therapy and tissue engineering.

Regulation of Assisted Reproductive Technologies: Gains and Losses

Technology assessment and regulatory strategies have been proffered as ways of addressing concerns and problems arising from availability of certain medical technologies. Regulation especially is invoked as a remedy that can deliver several objectives—as a way of assuring quality care; as a way of preventing medical malpractice and negligence; as a remedy for market failure; as a way of improving performance and efficiency; and as a way of even achieving national health objectives or wider social goals such as equity and accountability. It is assumed that the key issues in regulation are its design and having proper monitoring and enforcement.

 The article reviews the regulations instituted to address issues arising from the use of reproductive technologies. Through such analysis, the article seeks to draw attention to the field of technology assessment and regulation in general as applicable to biomedical technologies, in a context of overall commercialisation of medical and health care.

High Frequency of Imprinted Methylation Errors in Human Preimplantation Embryos

Assisted reproductive technologies (ARTs) represent the best chance for infertile couples to conceive, although increased risks for morbidities exist, including imprinting disorders. This increased risk could arise from ARTs disrupting genomic imprints during gametogenesis or preimplantation. The few studies examining ART effects on genomic imprinting primarily assessed poor quality human embryos. Here, we examined day 3 and blastocyst stage, good to high quality, donated human embryos for imprinted SNRPN, KCNQ1OT1 and H19 methylation. Seventy-six percent day 3 embryos and 50% blastocysts exhibited perturbed imprinted methylation, demonstrating that extended culture did not pose greater risk for imprinting errors than short culture. Comparison of embryos with normal and abnormal methylation didn’t reveal any confounding factors. Notably, two embryos from male factor infertility patients using donor sperm harboured aberrant methylation, suggesting errors in these embryos cannot be explained by infertility alone. Overall, these results indicate that ART human preimplantation embryos possess a high frequency of imprinted methylation errors.

Oxidative DNA damage in mouse sperm chromosomes: Size matters

Normal embryo and foetal development as well as the health of the progeny are mostly dependent on gamete nuclear integrity. In the present study, in order to characterize more precisely oxidative DNA damage in mouse sperm we used two mouse models that display high levels of sperm oxidative DNA damage, a common alteration encountered both in in vivo and in vitro reproduction. Immunoprecipitation of oxidized sperm DNA coupled to deep sequencing showed that mouse chromosomes may be largely affected by oxidative alterations. We show that the vulnerability of chromosomes to oxidative attack inversely correlated with their size and was not linked to their GC richness. It was neither correlated with the chromosome content in persisting nucleosomes nor associated with methylated sequences. A strong correlation was found between oxidized sequences and sequences rich in short interspersed repeat elements (SINEs). Chromosome position in the sperm nucleus as revealed by fluorescent in situ hybridization appears to be a confounder. These data map for the first time fragile mouse sperm chromosomal regions when facing oxidative damage that may challenge the repair mechanisms of the oocyte post-fertilization.

Shojaei Saadi H, Gad A, Schellander K, Tesfaye D. Genome-Wide DNA Methylation Patterns of Bovine Blastocysts Developed In Vivo from Embryos Completed Different Stages of Development In Vitro

Early embryonic loss and altered gene expression in in vitro produced blastocysts are believed to be partly caused by aberrant DNA methylation. However, specific embryonic stage which is sensitive to in vitro culture conditions to alter the DNA methylation profile of the resulting blastocysts remained unclear. Therefore, the aim of this study was to investigate the stage specific effect of in vitro culture environment on the DNA methylation response of the resulting blastocysts. For this, embryos cultured in vitro until zygote (ZY), 4-cell (4C) or 16-cell (16C) were transferred to recipients and the blastocysts were recovery at day 7 of the estrous cycle. Another embryo group was cultured in vitro until blastocyst stage (IVP). Genome-wide DNA methylation profiles of ZY, 4C, 16C and IVP blastocyst groups were then determined with reference to blastocysts developed completely under in vivo condition (VO) using EmbryoGENE DNA Methylation Array. To assess the contribution of methylation changes on gene expression patterns, the DNA methylation data was superimposed to the transcriptome profile data. The degree of DNA methylation dysregulation in the promoter and/or gene body regions of the resulting blastocysts was correlated with successive stages of development the embryos advanced under in vitro culture before transfer to the in vivo condition. Genomic enrichment analysis revealed that in 4C and 16C blastocyst groups, hypermethylated loci were outpacing the hypomethylated ones in intronic, exonic, promoter and proximal promoter regions, whereas the reverse was observed in ZY blastocyst group. However, in the IVP group, as much hypermethylated as hypomethylated probes were detected in gene body and promoter regions. In addition, gene ontology analysis indicated that differentially methylated regions were found to affected several biological functions including ATP binding in the ZY group, programmed cell death in the 4C, glycolysis in 16C and genetic imprinting and chromosome segregation in IVP blastocyst groups. Furthermore, 1.6, 3.4, 3.9 and 9.4% of the differentially methylated regions that were overlapped to the transcriptome profile data were negatively correlated with the gene expression patterns in ZY, 4C, 16C and IVP blastocyst groups, respectively. Therefore, this finding indicated that suboptimal culture condition during preimplantation embryo development induced changes in the DNA methylation landscape of the resulting blastocysts in a stage dependent manner and the altered DNA methylation pattern was only partly explained the observed aberrant gene expression patterns of the blastocysts.

Morphological assessment on day 4 and its prognostic power in selecting viable embryos for transfer

The aim of this study was to describe a system for embryo morphology scoring at the morula stage and to determine the efficiency of this model in selecting viable embryos for transfer. In total, 519 embryos from 122 patients undergoing intracytoplasmic sperm injection (ICSI) were scored retrospectively on day 4 according to the grading system proposed in this article. Two separate quality scores were assigned to each embryo in relation to the grade of compaction and fragmentation and their developmental fate was then observed on days 5 and 6. Secondly, the prediction value of this scoring system was compared with the prediction value of the traditional scoring system adopted on day 3. Morulas classified as grade A showed a significant higher blastocyst formation rate (87.2%) compared with grades B, C and D (63.8, 41.3 and 15.0%, respectively), (P < 0.001). Furthermore, the ability to form top quality blastocysts was significantly higher for grade A morulas with respect to grades B, and C and D (37.8% vs. 22.4% vs. 11.1%), (P < 0.001). Finally, the morula scoring system showed more prediction power with respect to the embryo scoring a value of 1 [Akaike information criterion (AIC) index 16.4 vs. 635.3 and Bayesian information criterion (BIC) index −68.8 vs. −30.0 for morulas and embryos respectively]. In conclusion, results demonstrated that the presented scoring system allows for the evaluation of eligible embryos for transfer as a significant correlation between the grade of morula, blastulation rate and blastocyst quality was observed. Furthermore, the morula scoring system was shown to be the best predictive model when compared with the traditional scoring system performed on day 3.

Genes and Conditions Controlling Mammalian Pre- and Post-implantation Embryo Development

Embryo quality during the in vitro developmental period is of great clinical importance. Experimental genetic studies during this period have demonstrated the association between specific gene expression profiles and the production of healthy blastocysts. Although the quality of the oocyte may play a major role in embryo development, it has been well established that the post - fertilization period also has an important and crucial role in the determination of blastocyst quality. A variety of genes (such as OCT, SOX2, NANOG) and their related signaling pathways as well as transcription molecules (such as TGF-β, BMP) have been implicated in the pre- and post-implantation period. Furthermore, DNA methylation has been lately characterized as an epigenetic mark since it is one of the most important processes involved in the maintenance of genome stability. Physiological embryo development appears to depend upon the correct DNA methylation pattern. Due to the fact that soon after fertilization the zygote undergoes several morphogenetic and developmental events including activation of embryonic genome through the transition of the maternal genome, a diverse gene expression pattern may lead to clinically important conditions, such as apoptosis or the production of a chromosomically abnormal embryo. The present review focused on genes and their role during pre-implantation embryo development, giving emphasis on the various parameters that may alter gene expression or DNA methylation patterns. The pre-implantation embryos derived from in vitro culture systems (in vitro fertilization) and the possible effects on gene expression after the prolonged culture conditions are also discussed.

Deoxyribonucleic acid methylation profiling of single human blastocysts by methylated CpG-island amplification coupled with CpG-island microarray

Objective

To study whether methylated CpG-island (CGI) amplification coupled with microarray (MCAM) can be used to generate DNA (deoxyribonucleic acid) methylation profiles from single human blastocysts.

Design

A pilot microarray study with methylated CpG-island amplification applied to human blastocyst genomic DNA and hybridized on CpG-island microarrays.

Setting

University research laboratory.

Patient(s)

Five cryopreserved sibling 2-pronuclear zygotes that were surplus to requirements for clinical treatment by in vitro fertilization were donated with informed consent from a patient attending Bourn Hall Clinic, Cambridge, United Kingdom.

Intervention(s)

None.

Main Outcome Measure(s)

Successful generation of genome-wide DNA methylation profiles at CpG islands from individual human blastocysts, with common genomic regions of DNA methylation identified between embryos.

Result(s)

Between 472 and 734 CpG islands were methylated in each blastocyst, with 121 CpG islands being commonly methylated in all 5 blastocysts. A further 159 CGIs were commonly methylated in 4 of the 5 tested blastocysts. Methylation was observed at a number of CGIs within imprinted-gene, differentially methylated regions (DMRs), including placental and preimplantation-specific DMRs.

Conclusion(s)

The MCAM method is capable of providing comprehensive DNA methylation data in individual human blastocysts.

Cardiovascular dysfunction in children conceived by assisted reproductive technologies

Epidemiological studies demonstrate a relationship between pathological events during foetal development and future cardiovascular risk and the term 'foetal programming of cardiovascular disease' has been coined to describe this phenomenon. The use of assisted reproductive technologies (ARTs) is growing exponentially and 2-5% of children are now born by this procedure. Emerging evidence indicates that ART represents a novel important example of foetal programming. Assisted reproductive technology may modify the cardiovascular phenotype in two ways: (i) ART involves manipulation of the early embryo which is exquisitely sensitive to environmental insults. In line with this concern, ART alters vascular and cardiac function in children and studies in mice show that ART alters the cardiovascular phenotype by epigenetic alterations related to suboptimal culture conditions. (ii) Assisted reproductive technology markedly increases the risk of foetal insults that augment cardiovascular risk in naturally conceived individuals and are expected to have similar consequences in the ART population. Given the young age of the ART population, it will take another 20-30 years before data on cardiovascular endpoints will be available. What is clear already, however, is that ART emerges as an important cardiovascular risk factor. This insight requires us to revise notions on ART's long-term safety and to engage on a debate on its future. There is an urgent need to better understand the mechanisms underpinning ART-induced alteration of the cardiovascular phenotype, improve the procedure and its long-term safety, and, while awaiting this aim, not to abandon medicine's fundamental principle of doing no harm (to future children) and use ART parsimoniously.

Seminal fluid and immune adaptation for pregnancy--comparative biology in mammalian species

Seminal fluid delivered to the female reproductive tract at coitus not only promotes the survival and fertilizing capacity of spermatozoa, but also contains potent signalling agents that influence female reproductive physiology to improve the chances of conception and reproductive success. Male to female seminal fluid signalling occurs in rodents, domestic and livestock animals, and all other mammals examined to date. Seminal plasma is instrumental in eliciting the female response, by provision of cytokines and prostaglandins synthesized in the male accessory glands. These agents bind to receptors on target cells in the cervix and uterus, activating changes in gene expression leading to functional adaptations in the female tissues. Sperm also interact with female tract cells, although the molecular basis of this interaction is not yet defined. The consequences are increased sperm survival and fertilization rates, conditioning of the female immune response to tolerate semen and the conceptus, and molecular and cellular changes in the endometrium that facilitate embryo development and implantation. Studies in porcine, equine, bovine, ovine and canine species all show evidence of male-female signalling function for seminal fluid. There are variations between species that relate to their different reproductive strategies and behaviours, particularly the site of seminal fluid deposition and female reproductive tract anatomy. Although the details of the molecular mechanisms require more study, the available data are consistent with both the sperm and plasma fractions of seminal fluid acting in a synergistic fashion to activate inflammation-like responses and downstream female tract changes in each of these species. Insight into the biological function and molecular basis of seminal fluid signalling in the female will inform new interventions and management practices to support optimal reproductive outcomes in domestic, livestock and endangered animal species.

Epigenetic consequences of artificial reproductive technologies to the bovine imprinted genes SNRPN, H19/IGF2, and IGF2R

Animal breeders have made widespread use of assisted reproductive technologies to accelerate genetic improvement programs aimed at obtaining more, better and cheaper food products. Selection approaches have traditionally focused on Mendel’s laws of inheritance using parental phenotypic characteristics and quantitative genetics approaches to choose the best parents for the next generation, regardless of their gender. However, apart from contributing DNA sequence variants, male and female gametes carry parental-specific epigenetic marks that play key roles during pre- and post-natal development and growth of the offspring. We herein review the epigenetic anomalies that are associated with artificial reproductive technologies in current use in animal breeding programs. For instance, we demonstrate that bovine embryos and fetuses derived by in vitro culture and somatic cell nuclear transfer show epigenetic anomalies in the differentially methylated regions controlling the expression of some imprinted genes. Although these genomic imprinting errors are undetected in the somatic tissues after birth, further research is warranted to examine potential germ cell transmission of epimutations and the potential risks of reproducing cattle using artificial reproductive technologies.

Female tract cytokines and developmental programming in embryos

In the physiological situation, cytokines are pivotal mediators of communication between the maternal tract and the embryo. Compelling evidence shows that cytokines emanating from the oviduct and uterus confer a sophisticated mechanism for 'fine-tuning' of embryo development, influencing a range of cellular events from cell survival and metabolism, through division and differentiation, and potentially exerting long-term impact through epigenetic remodelling. The balance between survival agents, including GM-CSF, CSF1, LIF, HB-EGF and IGFII, against apoptosis-inducing factors such as TNFα, TRAIL and IFNg, influence the course of preimplantation development, causing embryos to develop normally, adapt to varying maternal environments, or in some cases to arrest and undergo demise. Maternal cytokine-mediated pathways help mediate the biological effects of embryo programming, embryo plasticity and adaptation, and maternal tract quality control. Thus maternal cytokines exert influence not only on fertility and pregnancy progression but on the developmental trajectory and health of offspring. Defining a clear understanding of the biology of cytokine networks influencing the embryo is essential to support optimal outcomes in natural and assisted conception.

Seminal Fluid Signalling in the Female Reproductive Tract: Implications for Reproductive Success and Offspring Health

Carriage of sperm is not the only function of seminal fluid in mammals. Studies in mice show that at conception, seminal fluid interacts with the female reproductive tract to induce responses which influence whether or not pregnancy will occur, and to set in train effects that help shape subsequent fetal development. In particular, seminal fluid initiates female immune adaptation processes required to tolerate male transplantation antigens present in seminal fluid and inherited by the conceptus. A tolerogenic immune environment to facilitate pregnancy depends on regulatory T cells (Treg cells), which recognise male antigens and function to suppress inflammation and immune rejection responses. The female response to seminal fluid stimulates the generation of Treg cells that protect the conceptus from inflammatory damage, to support implantation and placental development. Seminal fluid also elicits molecular and cellular changes in the oviduct and endometrium that directly promote embryo development and implantation competence. The plasma fraction of seminal fluid plays a key role in this process with soluble factors, including TGFB, prostaglandin-E, and TLR4 ligands, demonstrated to contribute to the peri-conception immune environment. Recent studies show that conception in the absence of seminal plasma in mice impairs embryo development and alters fetal development to impact the phenotype of offspring, with adverse effects on adult metabolic function particularly in males. This review summarises our current understanding of the molecular responses to seminal fluid and how this contributes to the establishment of pregnancy, generation of an immune-regulatory environment and programming long-term offspring health.

The frequency of clinical pregnancy and implantation rate after cultivation of embryos in a medium with granulocyte macrophage colony-stimulating factor (GM-CSF) in patients with preceding failed attempts of ART

The application in IVF practice of modern techniques can improve positive outcome of each cycle in the assisted reproductive technology (ART) programs and the effectiveness of treatment as a whole. There are embryos in the female reproductive tract in physiological medium which contain various cytokines and growth factors. It plays an important role in the regulation of normal embryonic development, improve implantation and subsequently optimizing the development of the fetus and the placenta. Granulocyte macrophage colony-stimulating factor (GM-CSF is one of the cytokines playing an important role in reproductive function. Addition of recombinant GM-CSF to the culture medium can makes closer human embryos culture to in vivo conditions and improve the efficacy ART cycles. The analysis of culture embryos in EmbryoGen medium has shown that fertilization rate embryo culture and transfer to patients with previous unsuccessful attempts increases clinical pregnancy rate compared to the control group 39.1 versus 27.8%, respectively. It is noted that the implantation rate (on 7 weeks' gestation) and progressive clinical pregnancy rate (on 12 weeks' gestation) were significantly higher in group embryos culture in EmbryoGen medium compared to standard combination of medium (ISM1+VA), and were 20.4 and 17.4% versus 11.6 and 9.1%, respectively.

Dynamic regulation of DNA methyltransferases in human oocytes and preimplantation embryos after assisted reproductive technologies

DNA methylation is a key epigenetic modification which is essential for normal embryonic development. Major epigenetic reprogramming takes place during gametogenesis and in the early embryo; the complex DNA methylation patterns are established and maintained by DNA methyltransferases (DNMTs). However, the influence of assisted reproductive technologies (ART) on DNA methylation reprogramming enzymes has predominantly been studied in mice and less so in human oocytes and embryos. The expression and localization patterns of the four known DNMTs were analysed in human oocytes and IVF/ICSI embryos by immunocytochemistry and compared between a reference group of good quality fresh embryos and groups of abnormally developing embryos or embryo groups after cryopreservation. In humans, DNMT1o rather than DNMT1s seems to be the key player for maintaining methylation in early embryos. DNMT3b, rather than DNMT3a and DNMT3L, appears to ensure global DNA remethylation in the blastocysts before implantation. DNMT3L, an important regulator of maternal imprint methylation in mouse, was not detected in human oocytes (GV, MI and MII stage). Our study confirms the existence of species differences for mammalian DNA methylation enzymes. In poor quality fresh embryos, the switch towards nuclear DNMT3b expression was delayed and nuclear DNMT1, DNMT1s and DNMT3b expression was less common. Compared with the reference embryos, a smaller number of cryopreserved embryos showed nuclear DNMT1, while a delayed switch to nuclear DNMT3b and an extended DNMT1s temporal expression pattern were also observed. The spatial and temporal expression patterns of DNMTs seem to be disturbed in abnormally developing embryos and in embryos that have been cryopreserved. Further research must be performed in order to understand whether the potentially disturbed embryonic DNMT expression after cryopreservation has any long-term developmental consequences.

Effects of pulsed electromagnetic field on differentiation of HUES-17 human embryonic stem cell line

Electromagnetic fields are considered to potentially affect embryonic development, but the mechanism is still unknown. In this study, human embryonic stem cell (hESC) line HUES-17 was applied to explore the mechanism of exposure on embryonic development to pulsed electromagnetic field (PEMF) for 400 pulses at different electric field intensities and the differentiation of HUES-17 cells was observed after PEMF exposure. The expression of alkaline phosphatase (AP), stage-specific embryonic antigen-3 (SSEA-3), SSEA-4 and the mRNA level and protein level of Oct4, Sox2 and Nanog in HUES-17 cells remained unchanged after PEMF exposure at the electric field intensities of 50, 100, 200 or 400 kV/m. Four hundred pulses PEMF exposure at the electric field intensities of 50, 100, 200 or 400 kV/m did not affect the differentiation of HUES-17 cells. The reason why electromagnetic fields affect embryonic development may be due to other mechanisms rather than affecting the differentiation of embryonic stem cells.

Imprinting methylation errors in ART

There has been an increase in incidence reports of rare imprinting disorders associated with assisted reproductive technology (ART). ART, including in vitro fertilization and intracytoplasmic sperm injections, is an important treatment for infertile people of reproductive age and increasingly produces children. The identification of epigenetic changes at imprinted loci in ART infants has led to the suggestion that ART techniques themselves may predispose embryos to acquire imprinting errors and diseases. In this review, we note that the particular steps of ART may be prone to induction of imprinting methylation errors during gametogenesis, fertilization and early embryonic development. In addition, we explain imprint-associated diseases and their causes. Moreover, from a Japanese nationwide epidemiological study of imprint-associated diseases, we determine their associations with ART. Epigenetic studies will be required to understand the pathogenesis, ART-related risk factor(s) and what precautions can be taken to prevent the occurrence of input methylation errors. We hope that the constitution of children born after each ART procedure will reveal the safest and most ethical approach to use, which will be invaluable for the future development of standard ART.