Assisted reproduction treatment and epigenetic inheritance

Bioengineered 3D ovarian model for long-term multiple development of preantral follicle: bridging the gap for poly(ε-caprolactone) (PCL)-based scaffold reproductive applications

BACKGROUND

Assisted Reproductive Technologies (ARTs) have been validated in human and animal to solve reproductive problems such as infertility, aging, genetic selection/amplification and diseases. The persistent gap in ART biomedical applications lies in recapitulating the early stage of ovarian folliculogenesis, thus providing protocols to drive the large reserve of immature follicles towards the gonadotropin-dependent phase. Tissue engineering is becoming a concrete solution to potentially recapitulate ovarian structure, mostly relying on the use of autologous early follicles on natural or synthetic scaffolds. Based on these premises, the present study has been designed to validate the use of the ovarian bioinspired patterned electrospun fibrous scaffolds fabricated with poly(ε-caprolactone) (PCL) for multiple preantral (PA) follicle development.

METHODS

PA follicles isolated from lamb ovaries were cultured on PCL scaffold adopting a validated single-follicle protocol (Ctrl) or simulating a multiple-follicle condition by reproducing an artificial ovary engrafted with 5 or 10 PA (AO5PA and AO10PA). The incubations were protracted for 14 and 18 days before assessing scaffold-based microenvironment suitability to assist in vitro folliculogenesis (ivF) and oogenesis at morphological and functional level.

RESULTS

The ivF outcomes demonstrated that PCL-scaffolds generate an appropriate biomimetic ovarian microenvironment supporting the transition of multiple PA follicles towards early antral (EA) stage by supporting follicle growth and steroidogenic activation. PCL-multiple bioengineering ivF (AO10PA) performed in long term generated, in addition, the greatest percentage of highly specialized gametes by enhancing meiotic competence, large chromatin remodeling and parthenogenetic developmental competence.

CONCLUSIONS

The study showcased the proof of concept for a next-generation ART use of PCL-patterned scaffold aimed to generate transplantable artificial ovary engrafted with autologous early-stage follicles or to advance ivF technologies holding a 3D bioinspired matrix promoting a physiological long-term multiple PA follicle protocol.

Body composition as an indicator of metabolic changes in mice obtained by in vitro fertilization

To identify body systems subject to epigenetic transformation during in vitro fertilization (IVF), comparative morphological and functional studies were performed on sexually mature offspring of outbred CD1 mice, specific-pathogen-free (SPF), obtained by IVF (experiment) and natural conception (control). The studies included assessment of age-related changes in body weight and composition, energy intake and expenditure, and glucose homeostasis. To level the effects caused by the different number of newborns in the control and in the experiment, the size of the fed litters was halved in the control females. Males obtained using the IVF procedure were superior in body weight compared to control males in all age groups. As was shown by analysis of variance with experiment/control factors, gender, age (7, 10 and 20 weeks), the IVF procedure had a statistically significant and unidirectional effect on body composition. At the same time, IVF offspring outperformed control individuals in relative fat content, but were behind in terms of lean mass. The effect of the interaction of factors was not statistically significant. IVF offspring of both sexes had higher fat to lean mass ratios (FLR). Since adipose tissue contributes significantly less to total energy intake compared to muscle, the main component of lean mass, it is not surprising that at the same level of IVF locomotor activity offspring consumed less food than controls. When converted to one gram of body weight, this difference reached 19 %. One of the consequences of reduced utilization of IVF energy substrates by offspring is a decrease in their tolerance to glucose loading. The integral criterion for the effectiveness of restoring the initial glucose level is the area under the curve (AUC), the value of which was 2.5 (males) and 3.2 (females) times higher in IVF offspring compared to the corresponding control. Thus, the totality of our original and literature data shows an increase in the risk of metabolic disorders in IVF offspring, which is confirmed by epidemiological studies of a relatively young cohort of people born using assisted reproductive technologies.

Pathomechanisms of Prenatally Programmed Adult Diseases

Based on epidemiological observations Barker et al. put forward the hypothesis/concept that an adverse intrauterine environment (involving an insufficient nutrient supply, chronic hypoxia, stress, and toxic substances) is an important risk factor for the development of chronic diseases later in life. The fetus responds to the unfavorable environment with adaptive reactions, which ensure survival in the short run, but at the expense of initiating pathological processes leading to adult diseases. In this review, the major mechanisms (including telomere dysfunction, epigenetic modifications, and cardiovascular-renal-endocrine-metabolic reactions) will be outlined, with a particular emphasis on the role of oxidative stress in the fetal origin of adult diseases.

Risk of genetic and epigenetic alteration in children conceived following ART: Is it time to return to nature whenever possible?

Assisted reproductive technology may influence epigenetic signature as the procedures coincide with the extensive epigenetic modification occurring from fertilization to embryo implantation. However, it is still unclear to what extent ART alters the embryo epigenome. In vivo fertilization occurs in the fallopian tube, where a specific and natural environment enables the embryo's healthy development. During this dynamic period, major waves of epigenetic reprogramming, crucial for the normal fate of the embryo, take place. Over the past decade, concerns relating to the raised incidence of epigenetic anomalies and imprinting following ART have been raised by several authors. Epigenetic reprogramming is particularly susceptible to environmental conditions during the periconceptional period; therefore, unphysiological conditions, including ovarian stimulation, in vitro fertilization, embryo culture, cryopreservation of gametes and embryos, parental lifestyle, and underlying infertility, have the potential to contribute to epigenetic dysregulation independently or collectively. This review critically appraises the evidence relating to the association between ART and genetic and epigenetic modifications that may be transmitted to the offspring.

How to improve the clinical outcome of round spermatid injection (ROSI) into the oocyte: Correction of epigenetic abnormalities

Background

First successful human round spermatid injection (ROSI) was conducted by Tesarik et al. in 1996 for the sole treatment of nonobstructive azoospermic men whose most advanced spermatogenic cells were elongating round spermatids. Nine offsprings from ROSI were reported between 1996 and 2000. No successful deliveries were reported for 15 years after that. Tanaka et al. reported 90 babies born after ROSI and their follow-up studies in 2015 and 2018 showed no significant differences in comparison with those born after natural conception in terms of physical and cognitive abilities. However, clinical outcomes remain low.

Method

Clinical and laboratory data of successful cases in the precursor ROSI groups and those of Tanaka et al. were reviewed.

Results

Differences were found between the two groups in terms of identification of characteristics of round spermatid and oocyte activation. Additionally, epigenetic abnormalities were identified as underlying causes for poor ROSI results, besides correct identification of round spermatid and adequate oocyte activation. Correction of epigenetic errors could lead to optimal embryonic development.

Conclusion

Correction of epigenetic abnormalities has a probability to improve the clinical outcome of ROSI.

Neurodevelopmental Disorders in Offspring Conceived via In Vitro Fertilization vs Intracytoplasmic Sperm Injection

IMPORTANCE

Intracytoplasmic sperm injection (ICSI), the most common type of assisted reproductive technology (ART), might damage the sperm or embryo. The implications of male infertility and ICSI for the neurodevelopmental health of offspring remain unknown.

OBJECTIVE

To analyze the risks of neurodevelopmental disorders in offspring of couples with male or female infertility with or without ICSI use.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study was conducted in Taiwan and used information collected from the national population registry data set, national birth data set, and national ART data set for all live singleton births from January 1, 2008, to December 31, 2016. The follow-up period started from the date of birth until the diagnosis of a disorder or December 31, 2018, whichever occurred first. Data were analyzed from July 1, 2021, to August 1, 2022.

EXPOSURES

Male or female infertility with or without ICSI.

MAIN OUTCOMES AND MEASURES

The outcome was the incidence of autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), and developmental delay in offspring with ART conception. Taiwan's national population registry data set was used to identify ASD, ADHD, and developmental delay diagnosed in outpatient clinic and hospitalization records.

RESULTS

The study included 1 575 971 singleton births (mean [SD] age, 5.87 [2.60] years; 819 389 boys [52.0%]), of whom 1 568 257 (99.5%) had natural conception, 2111 (0.1%) had ART conception with male infertility, and 5603 (0.4%) had ART conception with female infertility. The risks of ASD (adjusted hazard ratio, 2.49; 95% CI, 1.61-3.84; P < .001) and developmental delay (adjusted hazard ratio, 1.92; 95% CI, 1.54-2.39; P < .001) in offspring with ART conception and ICSI use were significantly higher than those in offspring with natural conception. The same results were found in offspring of couples with either male or female infertility and ICSI intervention.

CONCLUSIONS AND RELEVANCE

Results of this study suggest that male infertility was not associated with an increased risk of neurodevelopmental disorders in offspring. In both male and female infertility groups, ICSI had unfavorable implications for the neurodevelopmental health of offspring in terms of increased risks of ASD and developmental delay.

The role of maternal DNA methylation in pregnancies complicated by gestational diabetes

Diabetes in pregnancy is associated with adverse pregnancy outcomes and poses a serious threat to the health of mother and child. Although the pathophysiological mechanisms that underlie the association between maternal diabetes and pregnancy complications have not yet been elucidated, it has been suggested that the frequency and severity of pregnancy complications are linked to the degree of hyperglycemia. Epigenetic mechanisms reflect gene-environment interactions and have emerged as key players in metabolic adaptation to pregnancy and the development of complications. DNA methylation, the best characterized epigenetic mechanism, has been reported to be dysregulated during various pregnancy complications, including pre-eclampsia, hypertension, diabetes, early pregnancy loss and preterm birth. The identification of altered DNA methylation patterns may serve to elucidate the pathophysiological mechanisms that underlie the different types of maternal diabetes during pregnancy. This review aims to provide a summary of existing knowledge on DNA methylation patterns in pregnancies complicated by pregestational type 1 (T1DM) and type 2 diabetes mellitus (T2DM), and gestational diabetes mellitus (GDM). Four databases, CINAHL, Scopus, PubMed and Google Scholar, were searched for studies on DNA methylation profiling in pregnancies complicated with diabetes. A total of 1985 articles were identified, of which 32 met the inclusion criteria and are included in this review. All studies profiled DNA methylation during GDM or impaired glucose tolerance (IGT), while no studies investigated T1DM or T2DM. We highlight the increased methylation of two genes, Hypoxia‐inducible Factor‐3α (HIF3α) and Peroxisome Proliferator-activated Receptor Gamma-coactivator-Alpha (PGC1-α), and the decreased methylation of one gene, Peroxisome Proliferator Activated Receptor Alpha (PPARα), in women with GDM compared to pregnant women with normoglycemia that were consistently methylated across diverse populations with varying pregnancy durations, and using different diagnostic criteria, methodologies and biological sources. These findings support the candidacy of these three differentially methylated genes as biomarkers for GDM. Furthermore, these genes may provide insight into the pathways that are epigenetically influenced during maternal diabetes and which should be prioritized and replicated in longitudinal studies and in larger populations to ensure their clinical applicability. Finally, we discuss the challenges and limitations of DNA methylation analysis, and the need for DNA methylation profiling to be conducted in different types of maternal diabetes in pregnancy.

Assisted reproductive technology and childhood morbidity: a longitudinal cohort study

OBJECTIVE

To evaluate the association between assisted reproductive technology (ART) and offspring morbidity in the first decade of life.

DESIGN

Longitudinal cohort study.

SETTING

Provincial health registry in Quebec, Canada.

PATIENT(S)

A total of 797,654 singleton children born between 2008 and 2019, followed up to 2020.

INTERVENTION(S)

Retrospective, noninterventional study of any ART procedure vs. no ART.

MAIN OUTCOME MEASURE(S)

Childhood morbidity, including hospitalization for infectious, allergic, malignant, and other diseases, assessed using adjusted Cox proportional hazards regression to estimate hazard ratios (HRs) with 95% confidence intervals (CIs) for the association with ART. We controlled for unmeasured family-level confounders that were shared among siblings through stratified Cox regression. To do so, we restricted the analysis to 10,097 siblings with discordant exposure to ART and compared the risk of outcomes in exposed vs. unexposed siblings.

RESULT(S)

Compared with no ART, ART was associated with 1.23 times the risk of any hospitalization (95% CI 1.19-1.27), 1.25 times the risk of infectious disease hospitalization (95% CI 1.21-1.29), and 1.25 times the risk of allergy hospitalization (95% CI 1.14-1.38). When we used a sibling design to control for shared genetic and environmental confounders, ART was not associated with a greater risk of childhood hospitalization (HR 0.92, 95% CI 0.78-1.08).

CONCLUSION(S)

ART is associated with an elevated risk of hospitalization up to 11 years of age, but discordant sibling analysis suggests that the association may be due to genetic, environmental, or other shared familial confounders.

The Consequences of Assisted Reproduction Technologies on the Offspring Health Throughout Life: A Placental Contribution

The use of assisted reproductive technologies (ART) worldwide has led to the conception and birth of over eight million babies since being implemented in 1978. ART use is currently on the rise, given growing infertility and the increase in conception age among men and women in industrialized countries. Though obstetric and perinatal outcomes have improved over the years, pregnancies achieved by ART still bear increased risks for the mother and the unborn child. Moreover, given that the first generation of ART offspring is now only reaching their forties, the long-term effects of ART are currently unknown. This is important, as there is a wealth of data showing that life-long health can be predetermined by poor conditions during intrauterine development, including irregularities in the structure and functioning of the placenta. In the current review, we aim to summarize the latest available findings examining the effects of ART on the cardiometabolic, cognitive/neurodevelopmental, and behavioral outcomes in the perinatal period, childhood and adolescence/adulthood; and to examine placental intrinsic factors that may contribute to the developmental outcomes of ART offspring. Altogether, the latest knowledge about life outcomes beyond adolescence for those conceived by ART appears to suggest a better long-term outcome than previously predicted. There are also changes in placenta structure and functional capacity with ART. However, more work in this area is critically required, since the potential consequences of ART may still emerge as the offspring gets older. In addition, knowledge of the placenta may help to foresee and mitigate any adverse outcomes in the offspring.

Is there any effect on imprinted genes H19, PEG3, and SNRPN during AOA?

Assisted oocyte activation (AOA) has been proposed as an effective technique to overcome the problem of impaired fertilization after intracytoplasmic sperm injection (ICSI) but the safety of AOA remains a concern. We aimed to investigate if AOA induces imprinting effects on embryos. We used 13 cleavage embryos, nine blastocysts, and eight placentas from 15 patients. The subjects were divided into six groups by tissue type and with or without AOA. The methylation levels of imprinted genes (H19, paternally expressed gene [PEG3] and small nuclear ribonucleoprotein polypeptide N [SNRPN]) were tested by pyrosequencing. We observed different methylation levels among cleavage embryos. The variability was much more remarkable between cleavage embryos than blastocysts and placenta tissues. The methylation levels were especially higher in SNRPN and lower in the H19 gene in AOA embryos than those without AOA. No significant difference was found either among blastocysts or among placenta tissues regardless of AOA. The methylation levels of the three genes in blastocysts were very similar to those in the placenta. Compared to conventional ICSI, AOA changed imprinting methylation rates at H19 and SNRPN in cleavage embryos but not in the blastocyst stage and placenta. We recommend that blastocyst transfer should be considered for patients undergoing AOA during in vitro fertilization.

Reproductive fluids, added to the culture media, contribute to minimizing phenotypical differences between in vitro-derived and artificial insemination-derived piglets

The addition of reproductive fluids (RF) to the culture media has shown benefits in different embryonic traits but its long-term effects on the offspring phenotype are still unknown. We aimed to describe such effects in pigs. Blood samples and growth parameters were collected from piglets derived from in vitro-produced embryos (IVP) with or without RF added in the culture media versus those artificially inseminated (AI), from day 0 to month 6 of life. An oral glucose tolerance test was performed on day 45 of life. We show here the first comparative data of the growth of animals produced through different assisted reproductive techniques, demonstrating differences between groups. Overall, there was a tendency to have a larger size at birth and faster growth in animals derived from in vitro fertilization and embryo culture versus AI, although this trend was diminished by the addition of RFs to the culture media. Similarly, small differences in hematological indices and glucose tolerance between animals derived from AI and those derived from IVP, with a sex-dependent effect, tended to fade in the presence of RF. The addition of RF to the culture media could contribute to minimizing the phenotypical differences between the in vitro-derived and AI offspring, particularly in males.

Genome-Wide Analysis of DNA Methylation in Buccal Cells of Children Conceived through IVF and ICSI

Early life periconceptional exposures during assisted reproductive technology (ART) procedures could alter the DNA methylation profiles of ART children, notably in imprinted genes and repetitive elements. At the genome scale, DNA methylation differences have been reported in ART conceptions at birth, but it is still unclear if those differences remain at childhood. Here, we performed an epigenome-wide DNA methylation association study using Illumina InfiniumEPIC BeadChip to assess the effects of the mode of conception on the methylome of buccal cells from 7- to 8-year-old children (48 children conceived after ART or naturally (control, CTL)) and according to the embryo culture medium in which they were conceived. We identified 127 differentially methylated positions (DMPs) and 16 differentially methylated regions (DMRs) (FDR < 0.05) with low delta beta differences between the two groups (ART vs. CTL). DMPs were preferentially located inside promoter proximal regions and CpG islands and were mostly hypermethylated with ART. We highlighted that the use of distinct embryo culture medium was not associated with DNA methylation differences in childhood. Overall, we bring additional evidence that children conceived via ART display limited genome-wide DNA methylation variation compared with those conceived naturally.

Growth analysis and blood profile in piglets born by embryo transfer

Assisted reproductive technologies (ART), besides solving several reproductive problems, it has also been used as a tool to improve the animal productivity that is required for feeding the human population. One of these techniques, the embryo transfer (ET), has presented limitations in the porcine species, which could constrain its use in the porcine industry. To clarify the potential of this technique, we aimed to compare the impact of using ET or artificial insemination (AI) on the phenotype of the offspring during its first days of age, in terms of growth and blood parameters. At birth, the body weight was higher for ET-females than AI-females, but this difference was no longer observed at day 15. On day 3, it was observed a higher concentration of red blood cells, haemoglobin, and haematocrit in females-ET and a higher concentration of white blood cells in both ET-derived piglets (males and females) when compared to AI groups. On day 3, the biochemical analysis showed a higher level of albumin for ET-derived males, and a lower level of bilirubin for ET-females than AI controls. However, all values were within the normal ranges. Our results indicate that piglets derived from ET seem to be phenotypically similar to those born by AI, which provides preliminary evidence that the ET procedure is a safe technique, but additional studies beyond 15 days of life are requested to conclude its global impact. Furthermore, the presented reference values of blood parameters in this species are interesting data for the pig industry.

Cardiovascular disease, obesity, and type 2 diabetes in children born after assisted reproductive technology: A population-based cohort study

BACKGROUND

Some earlier studies have found indications of significant changes in cardiometabolic risk factors in children born after assisted reproductive technology (ART). Most of these studies are based on small cohorts with high risk of selection bias. In this study, we compared the risk of cardiovascular disease, obesity, and type 2 diabetes between singleton children born after ART and singleton children born after spontaneous conception (SC).

METHODS AND FINDINGS

This was a large population-based cohort study of individuals born in Norway, Sweden, Finland, and Denmark between 1984 and 2015. Data were obtained from national ART and medical birth registers and cross-linked with data from national patient registers and other population-based registers in the respective countries. In total, 122,429 children born after ART and 7,574,685 children born after SC were included. Mean (SD) maternal age was 33.9 (4.3) years for ART and 29.7 (5.2) for SC, 67.7% versus 41.8% were primiparous, and 45.2% versus 32.1% had more than 12 years of education. Preterm birth (<37 weeks 0 days) occurred in 7.9% of children born after ART and 4.8% in children born after SC, and 5.7% versus 3.3% had a low birth weight (<2,500 g). Mean (SD) follow-up time was 8.6 (6.2) years for children born after ART and 14.0 (8.6) years for children born after SC. In total, 135 (0.11%), 645 (0.65%), and 18 (0.01%) children born after ART were diagnosed with cardiovascular disease (ischemic heart disease, cardiomyopathy, heart failure, or cerebrovascular disease), obesity or type 2 diabetes, respectively. The corresponding values were 10,702 (0.14%), 30,308 (0.74%), and 2,919 (0.04%) for children born after SC. In the unadjusted analysis, children born after ART had a significantly higher risk of any cardiovascular disease (hazard ratio [HR] 1.24; 95% CI 1.04-1.48; p = 0.02), obesity (HR 1.13; 95% CI 1.05-1.23; p = 0.002), and type 2 diabetes (HR 1.71; 95% CI 1.08-2.73; p = 0.02). After adjustment, there was no significant difference between children born after ART and children born after SC for any cardiovascular disease (adjusted HR [aHR]1.02; 95% CI 0.86-1.22; p = 0.80) or type 2 diabetes (aHR 1.31; 95% CI 0.82-2.09; p = 0.25). For any cardiovascular disease, the 95% CI was reasonably narrow, excluding effects of a substantial magnitude, while the 95% CI for type 2 diabetes was wide, not excluding clinically meaningful effects. For obesity, there was a small but significant increased risk among children born after ART (aHR 1.14; 95% CI 1.06-1.23; p = 0.001). Important limitations of the study were the relatively short follow-up time, the limited number of events for some outcomes, and that the outcome obesity is often not considered as a disease and therefore not caught by registers, likely leading to an underestimation of obesity in both children born after ART and children born after SC.

CONCLUSIONS

In this study, we observed no difference in the risk of cardiovascular disease or type 2 diabetes between children born after ART and children born after SC. For obesity, there was a small but significant increased risk for children born after ART.

TRIAL REGISTRATION NUMBER

ISRCTN11780826.

Cohort profile: a national, population-based cohort of children born after assisted conception in the UK (1992-2009): methodology and birthweight analysis

PURPOSE

To generate a large cohort of children born after assisted reproductive technology (ART) in the UK between 1992 and 2009, their naturally conceived siblings (NCS) and matched naturally conceived population (NCP) controls and linking this with health outcome data to allow exploration of the effects of ART. The effects of fresh and frozen embryo transfer on birth weight (BW) were analysed to test the validity of the cohort.

PARTICIPANTS

Children recorded on the Human Fertilisation and Embryology Authority (HFEA) register as being born after ART between 1992 and 2009, their NCS and matched NCP controls linked to Office for National Statistics birth registration dataset (HFEA-ONS cohort). This cohort was further linked to the UK Hospital Episode Statistics database to allow monitoring of the child's post-natal health outcomes up to 2015 (HFEA-ONS-HES subcohort).

FINDINGS TO DATE

The HFEA-ONS cohort consisted of 75 348 children born after non-donor ART carried out in the UK between 1 April 1992 and 31 July 2009 and successfully linked to birth registration records, 14 763 NCS and 164 823 matched NCP controls. The HFEA-ONS-HES subcohort included 63 877 ART, 11 343 NCS and 127 544 matched NCP controls further linked to health outcome data. The exemplar analysis showed that children born after fresh embryo transfers were lighter (BW difference: -131 g, 95% CI: -140 to -123) and those born after frozen embryo transfers were heavier (BW difference: 35 g, 95% CI: 19 to 52) than the NCP controls. The within-sibling analyses were directionally consistent with the population control analyses, but attenuated markedly for the fresh versus natural conception (BW difference: -54 g; 95% CI: -72 to -36) and increased markedly for the frozen versus natural conception (BW difference: 152 g; 95% CI: 113 to 190) analyses.

FUTURE PLANS

To use this cohort to explore the relationship between ART conception and short-term and long-term health outcomes in offspring.

The association between in vitro fertilization and intracytoplasmic sperm injection treatment and the risk of congenital heart defects

OBJECTIVE

Assisted reproductive technology (ART), an effective treatment modality for infertility, is associated with a higher prevalence of congenital anomalies such as congenital heart defects (CHDs). The present study aimed to evaluate data linking CHDs in infants to pregnancies resulting from in vitro fertilization (IVF) and/or intracytoplasmic sperm injection (ICSI).

METHODS

In this study, we conducted a systematic literature search on CHDs in infants following IVF/ICSI in Google Scholar, Embase, Scopus, MEDLINE, and PubMed databases from inception to February 2020. The search strategy used combinations of search keywords that included assisted reproductive technology/ART, in vitro fertilization/IVF, intracytoplasmic sperm injection/ICSI, birth defect, congenital malformation, and congenital heart defects.

RESULTS

Fifty-six studies fulfilled the inclusion criteria and were selected in the current systematic review, which assessed the association between ART and the risk of CHDs.

CONCLUSION

Children conceived by IVF/ICSI manifested an increased risk of CHDs compared with spontaneously conceived children. Further studies are needed to assess the long-term cardiovascular safety of these techniques, which is important for the counseling of patients before the use of ART.

Association between childhood asthma and history of assisted reproduction techniques: a systematic review and meta-analysis

Genetic and environmental factors during early development may influence lung growth and impact lung function. We performed a meta-analysis of epidemiological studies examining the association between conception history of assisted reproduction techniques (ART) and childhood asthma. We searched PubMed and Embase up to November 2020 for relevant observational studies and synthesized data data under a fixed or random effects model as appropriate. Heterogeneity was assessed using the I² metric. We identified 13 individual studies including 3,226,386 participants. We did not observe a statistically significant association between ART and physician-diagnosed asthma (n = 9, random OR 1.16; 95% CI 0.94-1.43; I² 61%). We observed a statistically significant association between ART and prescription of asthma medications (n = 6, fixed OR 1.27; 95% CI 1.23-1.32; I² 0%). Wheezing was also associated with ART (n = 4, fixed OR 1.71; 95% CI 1.08-2.72; I² 0%). When we combined studies using any asthma definition, a statistically significant association was observed (random OR 1.19; 95% CI 1.05-1.34; I² 80%).Conclusion: The available observational evidence suggests that the risk of asthma is higher among children born after ART. The mechanism and potential sources of bias behind this association are under scrutiny, and further work is needed to establish causality. What is Known: • "Positive" epidemiological signals for the association between assisted reproduction techniques and asthma stemming from large studies were not replicated by subsequent research. • Any available research synthesis effort so far bears no quantitative aspect. What is New: • The available observational evidence suggests that the risk of asthma is higher among children born after ART. • The mechanism and potential sources of bias behind this association are under scrutiny.

Prediction of oocyte quality using mRNA transcripts screened by RNA sequencing of human granulosa cells

RESEARCH QUESTION

Can RNA transcripts of granulosa cells be used to assess oocyte quality? The possibility of predicting the developmental competence of oocytes by RNA sequencing analysis of granulosa cells was evaluated.

DESIGN

Granulosa cell samples were collected from 29 women undergoing assisted reproductive technology treatment and divided into two groups: 14 samples from the high blastocyst rate group and 15 from the low blastocyst rate group. Ten samples from each group were selected for RNA sequencing.

RESULTS

A total of 129 differentially expressed genes associated with high developmental competence of oocytes were identified. COL1A2, renin and COL1A1 were selected and further examined by quantitative real-time polymerase chain reaction (qRT-PCR). Expression levels of COL1A2 and renin by qRT-PCR were consistent with the results of RNA sequencing.

CONCLUSION

RNA sequencing data could provide novel marker genes for the non-invasive evaluation of oocyte quality and embryo developmental competence.

Do assisted reproductive technologies and in vitro embryo culture influence the epigenetic control of imprinted genes and transposable elements in children?

STUDY QUESTION

Do assisted reproductive technologies (ART) and in vitro embryo culture influence the epigenetic control of imprinted genes (IGs) and transposable elements (TEs) in children?

SUMMARY ANSWER

Significant differences in the DNA methylation of IGs or transposon families were reported between ART and naturally conceived children, but there was no difference between culture media.

WHAT IS KNOWN ALREADY

There is concern that ART may play a role in increasing the incidence of adverse health outcomes in children, probably through epigenetic mechanisms. It is crucial to assess epigenetic control, especially following non-optimal in vitro culture conditions and to compare epigenetic analyses from ART-conceived and naturally conceived children.

STUDY DESIGN, SIZE, DURATION

This follow-up study was based on an earlier randomized study comparing in vitro fertilization outcomes following the use of two distinct culture media. We compared the epigenetic profiles of children from the initial randomized study according to the mode of conception [i.e. ART singletons compared with those of a cohort of naturally conceived singleton children (CTL)], the type of embryo culture medium used [global medium (LifeGlobal) and single step medium (Irvine Scientific)] and the mode of in vitro fertilization (i.e. IVF versus ICSI).

PARTICIPANTS/MATERIALS, SETTING, METHODS

A total of 57 buccal smears were collected from 7- to 8-year-old children. The DNA methylation profiles of four differentially methylated regions (DMRs) of IGs (H19/IGF2: IG-DMR, KCNQ1OT1: TSS-DMR, SNURF: TSS-DMR, and PEG3: TSS-DMR) and two TEs (AluYa5 and LINE-1) were first assessed by pyrosequencing. We further explored IGs and TEs' methylation changes through methylation array (Human MethylationEPIC BeadChip referred as EPIC array, Illumina).

MAIN RESULTS AND THE ROLE OF CHANCE

Changes in the IGs' DNA methylation levels were found in ART children compared to controls. DNA methylation levels of H19/IGF2 DMR were significantly lower in ART children than in CTL children [52% versus 58%, P = 0.003, false discovery rate (FDR) P = 0.018] while a significantly higher methylation rate was observed for the PEG3 DMR (51% versus 48%, P = 0.007, FDR P = 0.021). However, no differences were found between the culture media. After observing these targeted modifications, analyses were performed at wider scale. Again, no differences were detected according to the culture media, but imprinted-related DMRs overlapping promoter region near the genes major for the development (MEG3, BLCAP, and DLX5) were detected between the ART and CTL children.

LIMITATIONS, REASONS FOR CAUTION

The sample size could seem relatively small, but the high consistency of our results was ensured by the homogeneity of the cohort from the initial randomized study, the standardized laboratory techniques and the robust statistical analyses accounting for multiple testing.

WIDER IMPLICATIONS OF THE FINDINGS

Although this study did not report DNA methylation differences depending on the culture medium, it sheds light on epigenetic changes that could be observed in some children conceived by ART as compared to CTL children. The clinical relevance of such differences remains largely unknown, and it is still unclear whether such changes are due to some specific ART procedures and/or to parental infertility.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by funding from the Agence Nationale pour la Recherche ('CARE'-ANR JCJC 2017). The authors have no conflicts of interest.

TRIAL REGISTRATION NUMBER

Not concerned.

Expression of mRNAs for pro-and anti-apoptotic factors in granulosa cells and follicular fluid of women undergoing in vitro fertilization. A pilot study

Background

This observational clinical study evaluated the expression levels and predictive values of some apoptosis-related genes in granulosa cells (GCs) and follicular fluid (FF) of women undergoing in vitro fertilization (IVF).

Methods

GCs and FF were obtained at oocyte retrieval from 31 consecutive patients with heterogeneous infertility diagnosis (age: 34.3 ± 5.8 years, body mass index: 24.02 ± 3.12 kg/m2, duration of infertility: 4.2 ± 2.1 years). mRNA expression of pro-apoptotic (BAX, CASP3, CASP8) and anti-apoptotic (BCL2, AMH, AMHR, FSHR, LHR, CYP19A1) factors was determined by quantitative RT-PCR using ROCHE LightCycler 480.

Results

No significant difference in GC or FF mRNA expression of pro- and anti-apoptotic factors could be demonstrated between IVF patients with (9 patients) or without (22 patients) clinical pregnancy. Each transcript investigated was detected in FF, but their levels were markedly reduced and independent of those in GCs. The number of retrieved oocytes was positively associated with GC AMHR (r = 0.393, p = 0.029), but the day of embryo transfer was negatively associated with GC LHR (r = − 0.414, p = 0.020) and GC FSHR transcripts (r = − 0.535, p = 0.002). When pregnancy positive group was analysed separately the impact of apoptosis- related gene expressions on some selected measures of IVF success could be observed. Strong positive relationship was found between gene expression levels of pro- and anti-apoptotic factors in GCs.

Conclusion

Our study provides only marginal evidences for the apoptosis dependence of IVF outcome and suggests that the apoptosis process induces adaptive increases of the anti-apoptotic gene expression to attenuate apoptosis and to protect cell survival.

Obstetric and neonatal outcomes after the transfer of vitrified-warmed blastocysts developing from nonpronuclear and monopronuclear zygotes: a retrospective cohort study

OBJECTIVE

To evaluate the obstetric and neonatal outcomes after the transfer of vitrified-warmed single blastocysts developing from nonpronuclear (0PN) and monopronuclear (1PN) zygotes.

DESIGN

Cohort study.

SETTING

Affiliated hospital.

PATIENT(S)

This study was a retrospective analysis of 435 0PN and 281 1PN vitrified-warmed single blastocyst transfers, and 151 0PN and 75 1PN singletons, compared with 13,167 two-pronuclear (2PN) vitrified-warmed single blastocyst transfers and 4,559 2PN singletons, respectively.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Pregnancy rate (PR), abortion rate (AR), live birth rate (LBR), and singleton birthweight were the primary outcome measures.

RESULT(S)

PR, AR, and LBR were similar when compared between the 0PN and 2PN groups after vitrified-warmed blastocyst transfer. However, the 0PN group had a higher birthweights, higher z scores, and a greater proportion of very large for gestational age newborns. When comparing the 1PN and 2PN groups, we found that the PR was similar whereas the AR was higher and the LBR was lower. No differences were detected in the other neonatal outcomes.

CONCLUSION(S)

The results of the present study show that the transfer of 2PN blastocysts should be prioritized because of a higher AR and a lower LBR after 1PN blastocyst transfers and a higher birthweight after 0PN blastocyst transfers when compared with 2PN blastocyst transfers. Our data indicate the need for concern about the safety of 1PN and 0PN embryo transfers.

In-utero stress and mode of conception: impact on regulation of imprinted genes, fetal development and future health

BACKGROUND

Genomic imprinting is an epigenetic gene regulatory mechanism; disruption of this process during early embryonic development can have major consequences on both fetal and placental development. The periconceptional period and intrauterine life are crucial for determining long-term susceptibility to diseases. Treatments and procedures in assisted reproductive technologies (ART) and adverse in-utero environments may modify the methylation levels of genomic imprinting regions, including insulin-like growth factor 2 (IGF2)/H19, mesoderm-specific transcript (MEST), and paternally expressed gene 10 (PEG10), affecting the development of the fetus. ART, maternal psychological stress, and gestational exposures to chemicals are common stressors suspected to alter global epigenetic patterns including imprinted genes.

OBJECTIVE AND RATIONALE

Our objective is to highlight the effect of conception mode and maternal psychological stress on fetal development. Specifically, we monitor fetal programming, regulation of imprinted genes, fetal growth, and long-term disease risk, using the imprinted genes IGF2/H19, MEST, and PEG10 as examples. The possible role of environmental chemicals in genomic imprinting is also discussed.

SEARCH METHODS

A PubMed search of articles published mostly from 2005 to 2019 was conducted using search terms IGF2/H19, MEST, PEG10, imprinted genes, DNA methylation, gene expression, and imprinting disorders (IDs). Studies focusing on maternal prenatal stress, psychological well-being, environmental chemicals, ART, and placental/fetal development were evaluated and included in this review.

OUTCOMES

IGF2/H19, MEST, and PEG10 imprinted genes have a broad developmental effect on fetal growth and birth weight variation. Their disruption is linked to pregnancy complications, metabolic disorders, cognitive impairment, and cancer. Adverse early environment has a major impact on the developing fetus, affecting mostly growth, the structure, and subsequent function of the hypothalamic-pituitary-adrenal axis and neurodevelopment. Extensive evidence suggests that the gestational environment has an impact on epigenetic patterns including imprinting, which can lead to adverse long-term outcomes in the offspring. Environmental stressors such as maternal prenatal psychological stress have been found to associate with altered DNA methylation patterns in placenta and to affect fetal development. Studies conducted during the past decades have suggested that ART pregnancies are at a higher risk for a number of complications such as birth defects and IDs. ART procedures involve multiple steps that are conducted during critical windows for imprinting establishment and maintenance, necessitating long-term evaluation of children conceived through ART. Exposure to environmental chemicals can affect placental imprinting and fetal growth both in humans and in experimental animals. Therefore, their role in imprinting should be better elucidated, considering the ubiquitous exposure to these chemicals.

WIDER IMPLICATIONS

Dysregulation of imprinted genes is a plausible mechanism linking stressors such as maternal psychological stress, conception using ART, and chemical exposures with fetal growth. It is expected that a greater understanding of the role of imprinted genes and their regulation in fetal development will provide insights for clinical prevention and management of growth and IDs. In a broader context, evidence connecting impaired imprinted gene function to common diseases such as cancer is increasing. This implies early regulation of imprinting may enable control of long-term human health, reducing the burden of disease in the population in years to come.

Disturbed genomic imprinting and its relevance for human reproduction: causes and clinical consequences

BACKGROUND

Human reproductive issues affecting fetal and maternal health are caused by numerous exogenous and endogenous factors, of which the latter undoubtedly include genetic changes. Pathogenic variants in either maternal or offspring DNA are associated with effects on the offspring including clinical disorders and nonviable outcomes. Conversely, both fetal and maternal factors can affect maternal health during pregnancy. Recently, it has become evident that mammalian reproduction is influenced by genomic imprinting, an epigenetic phenomenon that regulates the expression of genes according to their parent from whom they are inherited. About 1% of human genes are normally expressed from only the maternally or paternally inherited gene copy. Since numerous imprinted genes are involved in (embryonic) growth and development, disturbance of their balanced expression can adversely affect these processes.

OBJECTIVE AND RATIONALE

This review summarises current our understanding of genomic imprinting in relation to human ontogenesis and pregnancy and its relevance for reproductive medicine.

SEARCH METHODS

Literature databases (Pubmed, Medline) were thoroughly searched for the role of imprinting in human reproductive failure. In particular, the terms ‘multilocus imprinting disturbances, SCMC, NLRP/NALP, imprinting and reproduction’ were used in various combinations.

OUTCOMES

A range of molecular changes to specific groups of imprinted genes are associated with imprinting disorders, i.e. syndromes with recognisable clinical features including distinctive prenatal features. Whereas the majority of affected individuals exhibit alterations at single imprinted loci, some have multi-locus imprinting disturbances (MLID) with less predictable clinical features. Imprinting disturbances are also seen in some nonviable pregnancy outcomes, such as (recurrent) hydatidiform moles, which can therefore be regarded as a severe form of imprinting disorders. There is growing evidence that MLID can be caused by variants in the maternal genome altering the imprinting status of the oocyte and the embryo, i.e. maternal effect mutations. Pregnancies of women carrying maternal affect mutations can have different courses, ranging from miscarriages to birth of children with clinical features of various imprinting disorders.

WIDER IMPLICATIONS

Increasing understanding of imprinting disturbances and their clinical consequences have significant impacts on diagnostics, counselling and management in the context of human reproduction. Defining criteria for identifying pregnancies complicated by imprinting disorders facilitates early diagnosis and personalised management of both the mother and offspring. Identifying the molecular lesions underlying imprinting disturbances (e.g. maternal effect mutations) allows targeted counselling of the family and focused medical care in further pregnancies.

Epigenetic Regulation of the Ontogenic Expression of the Dopamine Transporter

The dopamine transporter (DAT) is a plasma membrane transport protein responsible for regulating the duration and intensity of dopaminergic signaling. Altered expression of DAT is linked to neurodevelopmental disorders, including attention deficit hyperactivity disorder and autism spectrum disorder, and is shown to contribute to the response of psychotropic drugs and neurotoxicants. Although the postnatal levels of DAT have been characterized, there are few data regarding the mechanisms that regulate postnatal DAT expression. Here, we examine the ontogeny of DAT mRNA from postnatal days 0 to 182 in the rat brain and define a role for epigenetic mechanisms regulating DAT expression. DAT mRNA and protein significantly increased between PND 0 and 6 months in rat midbrain and striatum, respectively. The epigenetic modifiers Dnmt1, Dnmt3a, Dnmt3b, and Hdac2 demonstrated age associated decreases in mRNA expression whereas Hdac5 and Hdac8 showed increased mRNA expression with age. Chromatin immunoprecipitation studies revealed increased protein enrichment of acetylated histone 3 at lysines 9 and 14 and the dopaminergic transcription factors Nurr1 and Pitx3 within the DAT promoter in an age-related manner. Together these studies provide evidence for the role of epigenetic modifications in the regulation of DAT during development. The identification of these mechanisms may contribute to potential therapeutic interventions aimed at neurodevelopmental disorders of the dopaminergic system.

Alteration in the expression of the renin-angiotensin system in the myocardium of mice conceived by in vitro fertilization

Epidemiological studies have revealed that offspring conceived by in vitro fertilization (IVF) have an elevated risk of cardiovascular malformations at birth, and are more predisposed to cardiovascular diseases. The renin-angiotensin system (RAS) plays an essential role in both the pathogenesis of congenital heart disease in fetuses and cardiovascular dysfunction in adults. This study aimed to assess the relative expression levels of genes in the RAS pathway in mice conceived using IVF, compared to natural mating with superovulation. Results demonstrated that expression of the angiotensin II receptor type 1 (AGTR1), connective tissue growth factor (CTGF), and collagen 3 (COL3), in the myocardial tissue of IVF-conceived mice, was elevated at 3 weeks, 10 weeks, and 1.5 years of age, when compared to their non-IVF counterparts. These data were supported by microRNA microarray analysis of the myocardial tissue of aged IVF-conceived mice, where miR-100, miR-297, and miR-758, which interact with COL3, AGTR1, and COL1 respectively, were upregulated when compared to naturally mated mice of the same age. Interestingly, bisulfite sequencing data indicated that IVF-conceived mice exhibited decreased methylation of CpG sites in Col1. In support of our in vivo investigations, miR-297 overexpression was shown to upregulate AGTR1 and CTGF, and increased cell proliferation in cultured H9c2 cardiomyocytes. These findings indicate that the altered expression of RAS in myocardial tissue might contribute to cardiovascular malformation and/or dysfunction in IVF-conceived offspring. Furthermore, these cardiovascular abnormalities might be the result of altered DNA methylation and abnormal regulation of microRNAs.

Effects of TLR4 overexpression on sperm quality, seminal plasma biomarkers, sperm DNA methylation and pregnancy rate in sheep

Genetic modification provides a means to enhancing disease resistance in animals. In this study, the first generation of genetically modified (GM) sheep overexpressing TLR4 was produced by microinjection for better disease resistance. To compare semen characteristics including sperm quality, seminal plasma biochemical index, sperm DNA methylation and pregnancy rate of three-year old transgenic sheep with TLR4 overexpressed (toll like receptor 4, TLR4) and non-transgenic ram. Sixteen transgenic ram of F0 generation were produced by microinjection of the TLR4 plasmid into the pronucleus of fertilized ova. Seven transgenic sheep of F1 generation was produced by breeding F0 transgenic founders with non-transgenic sheep of the same breed. There were no significant differences between transgenic and control rams for all semen quality parameters, including semen volume, sperm concentration, sperm viability, and percentages of sperm with an intact plasma membrane, acrosomal integrity, and viable sperm with high mitochondrial membrane potential in both F0 and F1 generation. Furthermore, no significant differences were found for seminal plasma concentrations of zinc, neutral alpha-glucosidase, acid phosphatase or fructose, nor for levels of H19 and IGF2R methylation in sperm DNA. In addition, pregnancy rate was also similar between these two groups. In conclusion, there was no evidence that TLR4 overexpression altered the sperm quality, seminal plasma or sperm DNA of transgenic sheep.

Loss of methylation of H19-imprinted gene derived from assisted reproductive technologies can be mitigated by cleavage-stage embryo transfer in mice

PURPOSE

Studies on rodents have shown that assisted reproductive technologies (ARTs) are associated with perturbation of genomic imprinting in blastocyst-stage embryos. However, the vulnerable developmental window for ART influence on the genomic imprinting of embryos is still undetermined. The purpose of this study was to establish the specific embryonic development stage at which the loss of methylation of H19 imprinting control regions (ICRs) was caused by ART occurrence. Additionally, we explored protocols to safeguard against possible negative impacts of ART on embryo H19 imprinting.

METHODS

Mouse embryos were generated under four different experimental conditions, divided into four groups: control, in vitro culture (IVC), in vitro fertilization (IVF), and intracytoplasmic sperm injection (ICSI). The methylation levels of H19 ICR of the grouped or individual embryos were analyzed by bisulfite-sequencing PCR.

RESULTS

Our data showed that the loss of methylation of H19 ICR in mouse blastocysts was inflicted to a similar extent by IVC, IVF, and ICSI. Specifically, we observed a significant loss of methylation of H19 ICR between the mouse 8-cell and morula stages. In addition, we revealed that the transfer of mouse embryos generated by ARTs in the uterus at the 8-cell stage induced the occurrence of methylation patterns in the blastocysts closer to the in vivo ones.

CONCLUSIONS

Our findings indicate that the loss of methylation of H19 ICR caused by ARTs occurs between the 8-cell and the morula stages, and the transfer of cleavage embryos to the uterus mitigates the loss methylation of H19 derived by mice ARTs.

Assisted reproductive technologies are associated with limited epigenetic variation at birth that largely resolves by adulthood

More than 7 million individuals have been conceived by Assisted Reproductive Technologies (ART) and there is clear evidence that ART is associated with a range of adverse early life outcomes, including rare imprinting disorders. The periconception period and early embryogenesis are associated with widespread epigenetic remodeling, which can be influenced by ART, with effects on the developmental trajectory in utero, and potentially on health throughout life. Here we profile genome-wide DNA methylation in blood collected in the newborn period and in adulthood (age 22–35 years) from a unique longitudinal cohort of ART-conceived individuals, previously shown to have no differences in health outcomes in early adulthood compared with non-ART-conceived individuals. We show evidence for specific ART-associated variation in methylation around birth, most of which occurred independently of embryo culturing. Importantly, ART-associated epigenetic variation at birth largely resolves by adulthood with no direct evidence that it impacts on development and health.

Use of Assisted Reproductive Technologies (ART) is increasing globally but their impact on long term health remains unclear. Here the authors show that ART-conceived individuals show variation in epigenetic profile at birth that largely resolves by adulthood, with no evidence of an impact on long term outcomes.

Epigenetics in Neurodevelopment: Emerging Role of Circular RNA

Canonical epigenetic modifications, including DNA methylation, histone modification and chromatin remodeling, play a role in numerous life processes, particularly neurodevelopment. Epigenetics explains the development of cells in an organism with the same DNA sequence into different cell types with various functions. However, previous studies on epigenetics have only focused on the chromatin level. Recently, epigenetic modifications of RNA, which mainly include 6-methyladenosine (m⁶A), pseudouridine, 5-methylcytidine (m⁵C), inosine (I), 2′-O-ribosemethylation, and 1-methyladenosine (m¹A), have gained increasing attention. Circular RNAs (circRNAs), which are a type of non-coding RNA without a 5′ cap or 3′ poly (A) tail, are abundantly found in the brain and might respond to and regulate synaptic function. Also, circRNAs have various functions, such as microRNA sponge, regulation of gene transcription and interaction with RNA binding protein. In addition, circRNAs are methylated by N⁶-methyladenosine (m⁶A). In this review, we discuss the crucial roles of epigenetic modifications of circRNAs, such as m⁶A, in the genesis and development of neurons and in synaptic function and plasticity. Thus, this type of changes in circRNAs might be a therapeutic target in central nervous system (CNS) disorders and could aid the diagnosis and treatment of these disorders.

Aanat Knockdown and Melatonin Supplementation in Embryo Development: Involvement of Mitochondrial Function and DNA Methylation

Aims: In addition to pineal gland, many cells, tissues, and organs also synthesize melatonin (N-acetyl-5-methoxytryptamine). Embryos are a group of special cells and whether they can synthesize melatonin is still an open question. However, melatonin application promoted embryo development in many species in in vitro condition. The purpose of this study was to investigate whether embryos can synthesize melatonin; if it is so, what are the impacts of the endogenously produced melatonin on embryo development and the associated molecular mechanisms. These have never been reported previously. Results: Melatonin synthesis was observed at different stages of embryonic development. Aanat (aralkylamine N-acetyltransferase), a rate-limiting enzyme for melatonin production, was found to mostly localize in the mitochondria. Aanat knockdown significantly impeded embryonic development, and melatonin supplementation rescued it. The potential mechanisms might be that melatonin preserved mitochondrial intact and its function, thus providing sufficient adenosine 5'-triphosphate for the embryo development. In addition, melatonin scavenged intracellular reactive oxygen species (ROS) and reduced the DNA mutation induced by oxidative stress. In the molecular level, Aanat knockdown reduced tet methylcytosine dioxygenase 2 (Tet2) expression and DNA demethylation in blastocyst and melatonin supplementation rescued these processes. Innovation: This is the first report to show that embryos synthesize melatonin, and its synthetic enzyme Aanat was located in the mitochondria of embryos. An effect of melatonin is to maintain Tet2 expression and normal methylation status, and thereby promote embryonic development. Conclusion: Embryos can produce melatonin that reduces ROS production, preserves mitochondrial function, and maintains Tet2 expression and the normal DNA methylation.

One-Carbon Metabolism: Linking Nutritional Biochemistry to Epigenetic Programming of Long-Term Development

One-carbon (1C) metabolism comprises a series of interlinking metabolic pathways that include the methionine and folate cycles that are central to cellular function, providing 1C units (methyl groups) for the synthesis of DNA, polyamines, amino acids, creatine, and phospholipids. S-adenosylmethionine is a potent aminopropyl and methyl donor within these cycles and serves as the principal substrate for methylation of DNA, associated proteins, and RNA. We propose that 1C metabolism functions as a key biochemical conduit between parental environment and epigenetic regulation of early development and that interindividual and ethnic variability in epigenetic-gene regulation arises because of genetic variants within 1C genes, associated epigenetic regulators, and differentially methylated target DNA sequences. We present evidence to support these propositions, drawing upon studies undertaken in humans and animals. We conclude that future studies should assess the epigenetic effects of cumulative (multigenerational) dietary imbalances contemporaneously in both parents, as this better represents the human experience.

Considerations Regarding Embryo Culture Conditions: From Media to Epigenetics

There are numerous reports on embryo culture media and conditions in the laboratory, as the subject is multifaceted and complex, reflecting the variation in practice. In this scoping review, we attempt to approach the topic of culture media and conditions from the practitioners' perspective aiming to highlight, in a comprehensive fashion, important aspects regarding the options available, introduce points of debate and controversy, while maintaining the viewpoint of the practicing embryologist's concerns.

Analyzing the Transcriptome Profile of Human Cumulus Cells Related to Embryo Quality via RNA Sequencing

Selecting excellent oocytes is required to improve the outcomes of in vitro fertilization (IVF). Cumulus cells (CCs) are an integral part of the oocyte maturation process. Therefore, we sought to identify differentially expressed genes in CCs to assess oocyte quality and embryo development potential. We divided the participants' embryos into the high-quality embryo group and low-quality embryo group by the information including age, body mass index, and the levels of luteinizing hormone, follicle-stimulating hormone, estradiol, and progesterone. We analyzed a total of 7 CC samples after the quality control in RNA sequencing. We found that 2499 genes were unregulated and 5739 genes were downregulated in high-quality embryo group compared to the low-quality embryo group (Padj < 0.05). Interestingly, MSTN, CTGF, NDUFA1, VCAN, SCD5, and STAR were significantly associated with the quality of embryo. In accordance with the results of RNA sequencing, the association of the expression levels of MSTN, CTGF, NDUFA1, VCAN, SCD5, and STAR with the embryo quality was verified by quantitative reverse-transcription polymerase chain reaction (RT-qPCR) in 50 CC samples. Despite the small sample size and lack of validation in animal models, our study supports the fact that differential gene expression profile of human CCs, including MSTN, CTGF, NDUFA1, VCAN, SCD5, and STAR, can serve as potential indicator for embryo quality.

ART manipulation after controlled ovarian stimulation may not increase the risk of abnormal expression and DNA methylation at some CpG sites of H19,IGF2 and SNRPN in foetuses: a pilot study

BACKGROUND

To examine the effects of IVF, ICSI and FET, as well as in vitro culture, on the safety of offspring, this study was conducted from the perspective of genetic imprinting to investigate whether assisted reproductive technology would influence the parental and maternal imprinting genes.

METHODS

Eighteen foetuses were collected from multifoetal reduction and divided into 6 groups: multifoetal reduction after IVF fresh transferred D3 embryos (n = 3), multifoetal reduction after IVF frozen transferred D3 embryos (n = 3), multifoetal reduction after IVF frozen transferred D5 embryos (n = 3), multifoetal reduction after ICSI fresh transferred D3 embryos (n = 3), multifoetal reduction after ICSI frozen transferred D3 embryos (n = 3), and multifoetal reduction after controlled ovarian hyperstimulation (COH) (n = 3). The imprinted genes H19, IGF2 and SNRPN were selected for analysis. The expression and DNA methylation at some CpG sites of H19, IGF2, and SNRPN were examined using real-time quantitative polymerase chain reaction (PCR) and pyrosequencing.

RESULTS

There were no significant differences in the mRNA expression levels among the groups. The mean percentage of H19 methylation (eight CpG sites), IGF2 methylation (five CpG sites) and SNRPN methylation (nine CpG sites) did not differ significantly.

CONCLUSIONS

The results suggest that ARTs after controlled ovarian stimulation (IVF, ICSI, cryopreservation and duration of in vitro culture) may not increase the risk of abnormal expression and DNA methylation at some CpG sites of H19, IGF2 and SNRPN in foetuses. Further study with strict design, expanded sample size and CpG sites is essential.

DNA methylation signatures in cord blood of ICSI children

STUDY QUESTION

Does ICSI induce specific DNA methylation changes in the resulting offspring?

SUMMARY ANSWER

Although several thousand analyzed CpG sites (throughout the genome) displayed significant between-group methylation differences, both ICSI and spontaneously conceived children varied within the normal range of methylation variation.

WHAT IS KNOWN ALREADY

Children conceived by ART have increased risks for medical problems at birth and to the extent of present knowledge also in later life (i.e. impaired metabolic and cardiovascular functions). One plausible mechanism mediating these ART effects are epigenetic changes originating in the germ cells and/or early embryos and persisting during further development.

STUDY DESIGN, SIZE, DURATION

We compared the cord blood methylomes and candidate gene methylation patterns of newborns conceived through ICSI or spontaneously.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Umbilical cord bloods were obtained from healthy newborn singletons conceived spontaneously (53 samples), through ICSI (89) or IVF (34). Bisulfite-converted DNA samples of 48 ICSI and 46 control pregnancies were used for genome-wide analyses with Illumina's 450K methylation arrays. Candidate genes from the methylation screen were analyzed in all three groups by bisulfite pyrosequencing.

MAIN RESULTS AND THE ROLE OF CHANCE

Altogether, 4730 (0.11%) of 428 227 analyzed CpG sites exhibited significant between-group methylation differences, but all with small (β < 10%) or very small (β < 1%) effect size. ICSI children showed a significantly decreased DNA methylation age at birth, lagging approximately half a week behind the controls. ART-susceptible CpGs were enriched in CpG islands with low methylation values (0-20%) and in imprinting control regions (ICRs). Eighteen promoter regions (six in microRNA and SNORD RNA genes), four CpG islands (three in genes including one long non-coding RNA), and two ICRs contained multiple significant sites. Three differentially methylated regions were studied in more detail by bisulfite pyrosequencing. ATG4C and SNORD114-9 could be validated in an independent ICSI group, following adjustment for maternal age and other confounding factors. ATG4C was also significant in the IVF group.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

The observed epigenetic effects are small and there are numerous potential confounding factors such as parental age and infertility. Although our study meets current standards for epigenetic screens, sample size is still two orders of magnitude below that of genome-wide association studies.

WIDER IMPLICATIONS OF THE FINDINGS

Our study suggests an impact of ICSI on the offspring's epigenome(s), which may contribute to phenotypic variation and disease susceptibility in ART children. Epigenetic regulation of gene expression by different classes of non-coding RNAs may be a key mechanism for developmental programming through ART.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by a research grant (no. 692185) from the European Union (ERA of ART). There are no competing interests.

Compromised oocyte quality and assisted reproduction contribute to sex-specific effects on offspring outcomes and epigenetic patterning

Clinical studies have revealed an increased incidence of growth and genomic imprinting disorders in children conceived using assisted reproductive technologies (ARTs), and aberrant DNA methylation has been implicated. We propose that compromised oocyte quality associated with female infertility may make embryos more susceptible to the induction of epigenetic defects by ART. DNA methylation patterns in the preimplantation embryo are dependent on the oocyte-specific DNA methyltransferase 1o (DNMT1o), levels of which are decreased in mature oocytes of aging females. Here, we assessed the effects of maternal deficiency in DNMT1o (Dnmt1Δ1o/+) in combination with superovulation and embryo transfer on offspring DNA methylation and development. We demonstrated a significant increase in the rates of morphological abnormalities in offspring collected from Dnmt1Δ1o/+  females only when combined with ART. Together, maternal oocyte DNMT1o deficiency and ART resulted in an accentuation of placental imprinting defects and the induction of genome-wide DNA methylation alterations, which were exacerbated in the placenta compared to the embryo. Significant sex-specific trends were also apparent, with a preponderance of DNA hypomethylation in females. Among genic regions affected, a significant enrichment for neurodevelopmental pathways was observed. Taken together, our results demonstrate that oocyte DNMT1o-deficiency exacerbates genome-wide DNA methylation abnormalities induced by ART in a sex-specific manner and plays a role in mediating poor embryonic outcome.

Recent developments in genetics and medically assisted reproduction: from research to clinical applications

Two leading European professional societies, the European Society of Human Genetics and the European Society for Human Reproduction and Embryology, have worked together since 2004 to evaluate the impact of fast research advances at the interface of assisted reproduction and genetics, including their application into clinical practice. In September 2016, the expert panel met for the third time. The topics discussed highlighted important issues covering the impacts of expanded carrier screening, direct-to-consumer genetic testing, voiding of the presumed anonymity of gamete donors by advanced genetic testing, advances in the research of genetic causes underlying male and female infertility, utilisation of massively parallel sequencing in preimplantation genetic testing and non-invasive prenatal screening, mitochondrial replacement in human oocytes, and additionally, issues related to cross-generational epigenetic inheritance following IVF and germline genome editing. The resulting paper represents a consensus of both professional societies involved.

Recent developments in genetics and medically-assisted reproduction: from research to clinical applications†‡

Two leading European professional societies, the European Society of Human Genetics and the European Society for Human Reproduction and Embryology, have worked together since 2004 to evaluate the impact of fast research advances at the interface of assisted reproduction and genetics, including their application into clinical practice. In September 2016, the expert panel met for the third time. The topics discussed highlighted important issues covering the impacts of expanded carrier screening, direct-to-consumer genetic testing, voiding of the presumed anonymity of gamete donors by advanced genetic testing, advances in the research of genetic causes underlying male and female infertility, utilisation of massively-parallel sequencing in preimplantation genetic testing and non-invasive prenatal screening, mitochondrial replacement in human oocytes, and additionally, issues related to cross-generational epigenetic inheritance following IVF and germline genome editing. The resulting paper represents a consensus of both professional societies involved.

Clinical review of 24-35 year olds conceived with and without in vitro fertilization: study protocol

Background

Children conceived by assisted reproductive technologies (ART) currently comprise 4% of Australian births. The manipulation of biological parameters related to fertilization and implantation are integral to successful ART but potentially pose a risk to the longer-term health of the offspring. There is consensus that many common adult health problems (particularly cardiovascular, metabolic and respiratory conditions) have their origins in early life, possibly before birth, and that risk trajectories track through childhood until clinical disease manifests in adulthood. Early life epigenetic variation may play a role in this process. However little is known about the long-term health of individuals conceived by ART. In a previous study, based on telephone-interviews, we found that young adults conceived by in vitro fertilization (IVF) had significantly more maternal reported atopic respiratory, endocrine, nutritional, and metabolic conditions than non-IVF conceived matched controls. Here we outline the protocol for a follow-up biomedical assessment of this cohort and a questionnaire to obtain information on potential confounders.

Methods

We are conducting a clinical review of an existing, well characterised cohort comprising 547 IVF-conceived adults and 549 matched controls. We are measuring cardiovascular intermediate phenotypes, metabolic parameters and respiratory function, complemented by epigenome-wide DNA methylation analysis. A pilot study demonstrated the feasibility of our proposed protocol and its acceptability to participants. Participants attend a 2–3 h clinical assessment and complete a study-specific online questionnaire. Measurements include: 1) cardiovascular phenotypes: carotid artery intima-media thickness and distensibility, retinal vascular calibre, resting blood pressure, pulse wave velocity and pulse wave analysis; 2) respiratory function: spirometry, plethysmography, multiple breath washout; 3) auxology: height, weight, waist circumference, bio-impedance. Blood is collected for 4) biomarkers of cardiometabolic profile including inflammatory markers and 5) epigenetic analysis.

Discussion

Recruitment for this clinical review is challenging as many of the participants have moved to regional, interstate or international locations. Additionally, many female participants are pregnant or breastfeeding, and are therefore ineligible. Nevertheless, comprehensive strategies have been developed to optimize recruitment. Given the increasing use of IVF and related technologies, the potential long-term consequences for risk of common adult diseases is an important clinical and public health issue.

Hypermethylation of the non-imprinted maternal MEG3 and paternal MEST alleles is highly variable among normal individuals

Imprinted genes show parent-specific activity (functional haploidy), which makes them particularly vulnerable to epigenetic dysregulation. Here we studied the methylation profiles of oppositely imprinted genes at single DNA molecule resolution by two independent parental allele-specific deep bisulfite sequencing (DBS) techniques. Using Roche (GSJunior) next generation sequencing technology, we analyzed the maternally imprinted MEST promoter and the paternally imprinted MEG3 intergenic (IG) differentially methylated region (DMR) in fetal cord blood, adult blood, and visceral adipose tissue. Epimutations were defined as paternal or maternal alleles with >50% aberrantly (de)methylated CpG sites, showing the wrong methylation imprint. The epimutation rates (range 2–66%) of the paternal MEST and the maternal MEG3 IG DMR allele, which should be completely unmethylated, were significantly higher than those (0–15%) of the maternal MEST and paternal MEG3 alleles, which are expected to be fully methylated. This hypermethylation of the non-imprinted allele (HNA) was independent of parental origin. Very low epimutation rates in sperm suggest that HNA occurred after fertilization. DBS with Illumina (MiSeq) technology confirmed HNA for the MEST promoter and the MEG3 IG DMR, and to a lesser extent, for the paternally imprinted secondary MEG3 promoter and the maternally imprinted PEG3 promoter. HNA leads to biallelic methylation of imprinted genes in a considerable proportion of normal body cells (somatic mosaicism) and is highly variable between individuals. We propose that during development and differentiation maintenance of differential methylation at most imprinting control regions may become to some extent redundant. The accumulation of stochastic and environmentally-induced methylation errors on the non-imprinted allele may increase epigenetic diversity between cells and individuals.

Transgenerational epigenetics and environmental justice

Human transmission to offspring and future generations of acquired epigenetic modifications has not been definitively established, although there are several environmental exposures with suggestive evidence. This article uses three examples of hazardous substances with greater exposures in vulnerable populations: pesticides, lead, and diesel exhaust. It then considers whether, if there were scientific evidence of transgenerational epigenetic inheritance, there would be greater attention given to concerns about environmental justice in environmental laws, regulations, and policies at all levels of government. To provide a broader perspective on environmental justice the article discusses two of the most commonly cited approaches to environmental justice. John Rawls's theory of justice as fairness, a form of egalitarianism, is frequently invoked for the principle that differential treatment of individuals is justified only if actions are designed to benefit those with the greatest need. Another theory, the capabilities approach of Amartya Sen and Martha Nussbaum, focuses on whether essential capabilities of society, such as life and health, are made available to all individuals. In applying principles of environmental justice the article considers whether there is a heightened societal obligation to protect the most vulnerable individuals from hazardous exposures that could adversely affect their offspring through epigenetic mechanisms. It concludes that unless there were compelling evidence of transgenerational epigenetic harms, it is unlikely that there would be a significant impetus to adopt new policies to prevent epigenetic harms by invoking principles of environmental justice.

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.

Environmental risk factors for autism: an evidence-based review of systematic reviews and meta-analyses

BACKGROUND

According to recent evidence, up to 40-50% of variance in autism spectrum disorder (ASD) liability might be determined by environmental factors. In the present paper, we conducted a review of systematic reviews and meta-analyses of environmental risk factors for ASD. We assessed each review for quality of evidence and provided a brief overview of putative mechanisms of environmental risk factors for ASD.

FINDINGS

Current evidence suggests that several environmental factors including vaccination, maternal smoking, thimerosal exposure, and most likely assisted reproductive technologies are unrelated to risk of ASD. On the contrary, advanced parental age is associated with higher risk of ASD. Birth complications that are associated with trauma or ischemia and hypoxia have also shown strong links to ASD, whereas other pregnancy-related factors such as maternal obesity, maternal diabetes, and caesarian section have shown a less strong (but significant) association with risk of ASD. The reviews on nutritional elements have been inconclusive about the detrimental effects of deficiency in folic acid and omega 3, but vitamin D seems to be deficient in patients with ASD. The studies on toxic elements have been largely limited by their design, but there is enough evidence for the association between some heavy metals (most important inorganic mercury and lead) and ASD that warrants further investigation. Mechanisms of the association between environmental factors and ASD are debated but might include non-causative association (including confounding), gene-related effect, oxidative stress, inflammation, hypoxia/ischemia, endocrine disruption, neurotransmitter alterations, and interference with signaling pathways.

CONCLUSIONS

Compared to genetic studies of ASD, studies of environmental risk factors are in their infancy and have significant methodological limitations. Future studies of ASD risk factors would benefit from a developmental psychopathology approach, prospective design, precise exposure measurement, reliable timing of exposure in relation to critical developmental periods and should take into account the dynamic interplay between gene and environment by using genetically informed designs.

The influence of in vitro fertilization and embryo culture on the embryo epigenetic constituents and the possible consequences in the bovine model

Medically assisted reproductive technologies, such as in vitro embryo production, are increasingly being used to palliate infertility. Eggs are produced following a hormonal regimen that stimulates the ovaries to produce a large number of oocytes. Collected oocytes are then fertilized in vitro and allowed to develop in vitro until they are either frozen or transferred to mothers. There are controversial reports on the adverse impacts of these technologies on early embryos and their potential long-term effects. Using newly developed technological platforms that enable global gene expression and global DNA methylation profiling, we evaluated gene perturbations caused by such artificial procedures. We know that cells in the early embryo produce all cells in the body and are able to respond to their in vitro environment. However, it is not known whether gene perturbations are part of a normal response to the environment or are due to distress and will have long-term impacts. While the mouse is an established genetic model used for quality control of culture media in clinics, the bovine is a large mono-ovulating mammal with similar embryonic kinetics as humans during the studied developmental window. These model systems are critical to understand the effects of assisted reproduction without the confounding impact of infertility and without the limitations imposed by the scarcity of donated human samples and ethical issues. The data presented in this review come mostly from our own experimentation, publications, and collaborations. Together they demonstrate that the in vitro environment has a significant impact on embryos at the transcriptomic level and at the DNA methylation level.

Factors associated with aberrant imprint methylation and oligozoospermia

Disturbingly, the number of patients with oligozoospermia (low sperm count) has been gradually increasing in industrialized countries. Epigenetic alterations are believed to be involved in this condition. Recent studies have clarified that intrinsic and extrinsic factors can induce epigenetic transgenerational phenotypes through apparent reprogramming of the male germ line. Here we examined DNA methylation levels of 22 human imprinted loci in a total of 221 purified sperm samples from infertile couples and found methylation alterations in 24.8% of the patients. Structural equation model suggested that the cause of imprint methylation errors in sperm might have been environmental factors. More specifically, aberrant methylation and a particular lifestyle (current smoking, excess consumption of carbonated drinks) were associated with severe oligozoospermia, while aging probably affected this pathology indirectly through the accumulation of PCB in the patients. Next we examined the pregnancy outcomes for patients when the sperm had abnormal imprint methylation. The live-birth rate decreased and the miscarriage rate increased with the methylation errors. Our research will be useful for the prevention of methylation errors in sperm from infertile men, and sperm with normal imprint methylation might increase the safety of assisted reproduction technology (ART) by reducing methylation-induced diseases of children conceived via ART.

DNA methyltransferase 3A promoter polymorphism is associated with the risk of human spontaneous abortion after assisted reproduction techniques and natural conception

PURPOSE

The aim of this study was to explore the association of the DNA-methyltransferase (DNMT)-3A and DNMT3B promoter polymorphisms with the risk of human spontaneous abortion after assisted reproduction techniques (ARTs) and natural conception.

METHODS

We collected tissues from women who underwent abortion procedures: (a) chorionic villus samples (CVS) and muscle samples (MS) from spontaneous abortions conceived by ART and natural cycle (study group), n = 152; and (b) CVS and MS from normal early pregnancy and second trimester (control group), n = 155. The single-nucleotide polymorphism (SNP) -448A > G in the DNMT3A promoter region and -149C/T polymorphism of DNMT3B were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and confirmed by sequencing.

RESULTS

The allele frequency of -448A among pregnancy loss group and control group was 34.2 % vs. 16.5 %, respectively. Compared with GG carriers, the DNMT3A -448AA homozygotes had an about 16-fold increased risk of spontaneous abortion [odds ratio (OR) = 16.130, 95 % confidence interval (CI), 3.665-70.984], and AG heterozygotes had an OR of 2.027 (95 % CI, 1.247-3.293). However, the distribution of -448A > G in individuals derived from ART pregnancies was not statistically significantly compared with those derived from spontaneous pregnancies (P = 0.661). For DNMT3B, we observed genotype frequencies of 100 % (TT) in the study group and the control group.

CONCLUSIONS

The DNMT3A -448A > G polymorphism may be a novel functional SNP and contribute to its genetic susceptibility to spontaneous abortion in Chinese women, and ART may not affect the distribution of -448A > G in pregnancy loss and normal pregnancy. The observed TT genotype of DMNT3B suggests that this is the predominant genotype of this population. The findings provide new insights into the etiology of human spontaneous abortion.

Cardiovascular and metabolic profiles of offspring conceived by assisted reproductive technologies: a systematic review and meta-analysis

OBJECTIVE

To evaluate cardiovascular and metabolic features of offspring conceived by in vitro fertilization/intracytoplasmic sperm injection (IVF-ICSI).

DESIGN

Literature review and meta-analysis.

SETTING

Not applicable.

PATIENT(S)

Offspring from IVF-ICSI versus natural conception.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Systolic and diastolic blood pressure (SBP and DBP), cardiovascular function, body mass index (BMI), and lipid and glucose profiles.

RESULT(S)

We included 19 studies that had recruited 2,112 IVF-ICSI and 4,096 naturally conceived offspring, ranging from childhood to early adulthood. The blood pressure levels of IVF-ICSI offspring were statistically significantly higher than those of naturally conceived offspring (weighted mean differences and confidence intervals: 1.88 mm Hg [95% CI, 0.27, 3.49] for SBP and 1.51 mm Hg [95% CI, 0.33, 2.70] for DBP). In addition, cardiac diastolic function was suboptimal and vessel thickness was higher among IVF-ICSI offspring. Compared with the metabolism of naturally conceived offspring, IVF-ICSI offspring displayed comparable BMI, lower low-density lipoprotein cholesterol levels, and higher fasting insulin levels.

CONCLUSION(S)

Children conceived by IVF-ICSI manifested a minor yet statistically significant increase in blood pressure without the clustering of increased BMI or impaired lipid metabolism by early adulthood. Our findings indicate a risk of cardiovascular disease among IVF-ICSI offspring, which calls for longer-term follow-ups and further investigation.