Study of DNA-methylation patterns at chromosome 15q11-q13 in children born after ICSI reveals no imprinting defects

Comparison of clinical outcomes between conventional in vitro fertilization and intracytoplasmic sperm injection in poor responders with only single oocyte retrieved

OBJECTIVE

To compare the clinical outcomes between conventional insemination (IVF) and intracytoplasmic sperm injection (ICSI) in poor responders with only a single oocyte retrieved.

MATERIALS AND METHODS

This is a retrospective case-control study. Couples who were treated with assisted reproductive technology (ART) with a single oocyte retrieved in Mackay Memorial Hospital from 1996 to 2016 were recruited. All data were categorized into three groups, according to their fertilization method and semen quality: group A, conventional insemination with non-male factor (IVF-NMF, n = 115), group B, ICSI with male factor (ICSI-MF, n = 30), and group C, ICSI with non-male factor (ICSI-NMF, n = 49).

RESULTS

No statistically significant difference was observed between IVF and ICSI groups in pregnancy outcomes, including the chemical or clinical pregnancy rate, miscarriage rate, and live birth rate. Similar fertilization rates per oocyte obtained were observed in IVF and ICSI patients, but significantly lower per mature oocyte in the ICSI group (IVF: 91.5%, ICSI-MF: 75.0%, ICSI-NMF: 77.8%). Although there is no statistical significance, the lower live birth rate is observed in group C than others (A:11.5%, B:25%, C:5%, p = 0.187).

CONCLUSION

In this study, pregnancy outcomes of conventional in vitro fertilization and ICSI in poor responders with only a single oocyte retrieved were similar. However, the fertilization rate of matured oocytes in ICSI groups is significantly lower than that in the IVF group, indicating that ICSI procedures might cause oocyte damage. Therefore, the choice of fertilization method should be based on semen quality. A randomized controlled trial should be performed to confirm our findings.

DNA Methylation in Offspring Conceived after Assisted Reproductive Techniques: A Systematic Review and Meta-Analysis

Background: In the last 40 years, assisted reproductive techniques (ARTs) have emerged as potentially resolving procedures for couple infertility. This study aims to evaluate whether ART is associated with epigenetic dysregulation in the offspring. Methods. To accomplish this, we collected all available data on methylation patterns in offspring conceived after ART and in spontaneously conceived (SC) offspring. Results. We extracted 949 records. Of these, 50 were considered eligible; 12 were included in the quantitative synthesis. Methylation levels of H19 CCCTC-binding factor 3 (CTCF3) were significantly lower in the ART group compared to controls (SMD −0.81 (−1.53; −0.09), I² = 89%, p = 0.03). In contrast, H19 CCCTC-binding factor 6 (CTCF6), Potassium Voltage-Gated Channel Subfamily Q Member 1 (KCNQ1OT1), Paternally-expressed gene 3 (PEG3), and Small Nuclear Ribonucleoprotein Polypeptide N (SNRPN) were not differently methylated in ART vs. SC offspring. Conclusion: The methylation pattern of the offspring conceived after ART may be different compared to spontaneous conception. Due to the lack of studies and the heterogeneity of the data, further prospective and well-sized population studies are needed to evaluate the impact of ART on the epigenome of the offspring.

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.

Defining new genetic etiologies of male infertility: progress and future prospects

Male infertility is a common and complex disease, manifesting as a wide range of phenotypes, ranging from apparently normal semen parameters with an inexplicable inability to conceive, to the complete absence of sperm production. The diversity of male infertility phenotypes, coupled with the extreme complexity of spermatogenesis has significantly confounded the identification of the underlying genetic causes for these conditions, though incremental progress has been made, particularly in the past decade. In this review, we discuss the progress that has been made to date, tools and resources that have proven effective in accelerating discovery of novel genetic markers for male infertility, and areas in which we see the greatest potential for advancing the field in the coming years. These include the development and use of robust phenotyping tools, the continued development of in vitro and animal models for variant validation, increased utilization and refinement of whole genome approaches for discovery, and further expansion of consortia that assemble groups of clinicians and basic researchers with the unified goal of disentangling the complex genetic architecture of male infertility. As these resources mature, and funding agencies increasingly recognize the importance of these efforts for improving human health, the discovery of novel genetic markers for male infertility will certainly continue to accelerate.

ICSI Does Not Improve Live Birth Rates but Yields Higher Cancellation Rates Than Conventional IVF in Unexplained Infertility

Objectives: Unexplained infertility has been one of the indications for utilization of intracytoplasmic sperm injection (ICSI). However, whether ICSI should be preferred to IVF for patients with unexplained infertility remains an open question. This study aims to determine if ICSI improves the clinical outcomes over conventional in vitro fertilization (IVF) in couples with unexplained infertility.

Methods: This was a retrospective cohort study of 549 IVF and 241 ICSI cycles for patients with unexplained infertility at a fertility center of a university hospital from January 2016 and December 2018. The live birth rate and clinical pregnancy rate were compared between the two groups. Other outcome measures included the implantation rate, miscarriage rate, and fertilization rate.

Results: The live birth rate was 35.2% (172/488) in the IVF group and 33.3% (65/195) in ICSI group, P = 0.635. The two groups also had similar clinical pregnancy rates, implantation rates, and miscarriage rates. The fertilization rate of IVF group was significantly higher than that of ICSI group (53.8 vs. 45.7%, P = 0.000, respectively). Sixty-one and 46 patients did not transfer fresh embryos in IVF and ICSI cycles, respectively. Patients with IVF cycles had lower cancellation rates than those with ICSI (11.1 vs. 19.1%, P = 0.003, respectively).

Conclusion: ICSI does not improve live birth rates but yields higher cancellation rates than conventional IVF in the treatment of unexplained infertility.

ICSI does not improve reproductive outcomes in autologous ovarian response cycles with non-male factor subfertility

STUDY QUESTION

Does the method of fertilisation improve reproductive outcomes in poor ovarian response (POR) cycles when compared to all other ovarian response categories in the absence of male factor subfertility?

SUMMARY ANSWER

ICSI does not confer any benefit in improving the clinical pregnancy or live birth (LB) outcome in autologous ovarian response cycles in the absence of male factor subfertility when compared to IVF.

WHAT IS KNOWN ALREADY

ICSI is associated with an improved outcome when compared to IVF in patients with severe male factor subfertility.

STUDY DESIGN, SIZE, DURATION

A retrospective study involving 1 376 454 ART cycles, of which 569 605 (41.4%) cycles fulfilled the inclusion and exclusion criteria for all autologous ovarian response categories: 272 433 (47.8%) IVF cycles and 297 172 (52.2%) ICSI cycles. Of these, the POR cohort represented 62 641 stimulated fresh cycles (11.0%): 33 436 (53.4%) IVF cycles and 29 205 (46.6%) ICSI cycles.

PARTICIPANTS/MATERIALS, SETTING, METHOD

All cycles recorded on the anonymised Human Fertilisation and Embryology Authority (HFEA) registry database between 1991 and 2016 were analysed. All fresh cycles with normal sperm parameters, performed after 1998 were included: frozen cycles, donor oocyte and sperm usage, intrauterine insemination cycles, preimplantation genetic testing (PGT) for aneuploidies (PGT-A), PGT for monogenic/single gene defects (PGT-M), PGT for chromosomal structural arrangements (PGT-SR) cycles, where the reason for stimulation was for storage and unstimulated cycles were excluded.

MAIN RESULTS AND THE ROLE OF CHANCE

ICSI did not confer any benefit in improving the LB outcome when compared to conventional IVF per treatment cycle (PTC), when adjusted for female age, number of previous ART treatment cycles, number of previous live births through ART, oocyte yield, stage of transfer, method of fertilisation and number of embryos transferred in the POR cohort (adjusted odds ratio [a OR] 1.03, 99.5% confidence interval [CI] 0.96–1.11, P = 0.261) and all autologous ovarian response categories (aOR 1.00, 99.5% CI 0.98–1.02, P = 0.900). The mean fertilisation rate was statistically lower for IVF treatment cycles (64.7%) when compared to ICSI treatment cycles (67.2%) in the POR cohort (mean difference −2.5%, 99.5% CI −3.3 to −1.6, P &lt; 0.001). The failed fertilisation rate was marginally higher in IVF treatment cycles (17.3%, 95% binomial exact 16.9 to 17.7%) when compared to ICSI treatment cycles (17.0%, 95% binomial exact 16.6 to 17.4%); however, this did not reach statistical significance (P = 0.199). The results followed a similar trend when analysed for all autologous ovarian response categories with a higher rate of failed fertilisation in IVF treatment cycles (4.8%, 95% binomial exact 4.7 to 4.9%) when compared to ICSI treatment cycles (3.2%, 95% binomial exact 3.1 to 3.3%) (P &lt; 0.001).

LIMITATIONS, REASONS FOR CAUTION

The quality of data is reliant on the reporting system. Furthermore, success rates through ART have improved since 1991, with an increased number of blastocyst-stage embryo transfers. The inability to link the treatment cycle to the individual patient meant that we were unable to calculate the cumulative LB outcome per patient.

WIDER IMPLICATIONS OF THE FINDINGS

This is the largest study to date which evaluates the impact of method of fertilisation in the POR patient and compares this to all autologous ovarian response categories. The results demonstrate that ICSI does not confer any benefit in improving reproductive outcomes in the absence of male factor subfertility, with no improvement seen in the clinical pregnancy or LB outcomes following a fresh treatment cycle.

STUDY FUNDING/COMPETING INTEREST(S)

The study received no funding. C.M.B. is a member of the independent data monitoring group for a clinical endometriosis trial by ObsEva. He is on the scientific advisory board for Myovant and medical advisory board for Flo Health. He has received research grants from Bayer AG, MDNA Life Sciences, Volition Rx and Roche Diagnostics as well as from Wellbeing of Women, Medical Research Council UK, the NIH, the UK National Institute for Health Research and the European Union. He is the current Chair of the Endometriosis Guideline Development Group for ESHRE and was a co-opted member of the Endometriosis Guideline Group by the UK National Institute for Health and Care Excellence (NICE). I.G. has received research grants from Bayer AG, Wellbeing of Women, the European Union and Finox.

TRIAL REGISTRATION NUMBER

Not applicable.

Epigenetics, Assisted Reproduction, and Intracytoplasmic Sperm Injection: A Review of the Current Data

Since the birth of the first in vitro fertilisation baby in 1978, >5 million babies have been born worldwide using assisted reproductive technologies (ART). ART were initially considered safe, but, in recent years, concerns regarding the association between these procedures and the increasing incidence of imprinting diseases have developed. There are numerous steps involved in ART and there are many variables that must be considered; even parental infertility may play an important role in offspring epigenetic modifications. This review presents available data from the literature regarding the incidence of these epigenetic modifications after ART, with a primary focus on oocyte insemination methodology. The authors conclude that ART, especially intracytoplasmic sperm injection, may induce epigenetic changes that can be transmitted to the offspring, but additional data are necessary to evaluate the factors involved and to determine the safety of each ART step.

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.

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.

Impairment of sperm DNA methylation in male infertility: a meta-analytic study

Considering the widespread use of assisted reproductive techniques (ART), DNA methylation of specific genes involved in spermatogenesis achieves increasingly clinical relevance, representing a possible explanation of increased incidence of syndromes related to genomic imprinting in medically assisted pregnancies. Several trials suggested a relationship between male sub-fertility and sperm DNA methylation, although its weight on seminal parameters alteration is still a matter of debate. To evaluate whether aberrant sperm DNA methylation of imprinted genes is associated with impaired sperm parameters. Meta-analysis of controlled clinical trials evaluating imprinted genes sperm DNA methylation comparing men with idiopathic infertility to fertile controls. Twenty-four studies were included, allowing a meta-analytic evaluation for H19, MEST, SNRPN, and LINE-1. When a high heterogeneity of the results was demonstrated, the random effect model was used. H19 methylation levels resulted significantly lower in 879 infertile compared with 562 fertile men (7.53%, 95% CI: 5.14-9.93%, p < 0.001), suggesting a 9.91-fold higher risk ratio to show aberrant sperm DNA methylation (95% CI: 5.55-17.70, p < 0.001, I²  = 19%) in infertile men. The mean MEST methylation level was significantly higher in 846 infertile compared with 353 fertile men (3.35%, 95% CI: 1.41-5.29%, p < 0.001), as well as for SNRPN comparing 301 infertile men with 124 controls (3.23%, 95% CI: 0.75-5.72%, p < 0.001). LINE-1 methylation levels did not differ between 291 infertile men and 198 controls (0.44%, 95% CI: -2.04-1.16%, p = 0.63). The meta-analytic approach demonstrated that male infertility is associated with altered sperm methylation at H19, MEST, and SNRPN. Although its role in infertility remains unclear, sperm DNA methylation could be associated with the epigenetic risk in ART. In this setting, before proposing this analysis in clinical practice, an accurate identification of the most representative genes and a cost-effectiveness evaluation should be assessed in ad hoc prospective studies.

Genetic and epigenetic risks of assisted reproduction

Assisted reproductive technology (ART) is used primarily for infertility treatments to achieve pregnancy and involves procedures such as in vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI), and cryopreservation. Moreover, preimplantation genetic diagnosis (PGD) of ART is used in couples for genetic reasons. In ART treatments, gametes and zygotes are exposed to a series of non-physiological processes and culture media. Although the majority of children born with this treatment are healthy, some concerns remain regarding the safety of this technology. Animal studies and follow-up studies of ART-borne children suggested that ART was associated with an increased incidence of genetic, physical, or developmental abnormalities, although there are also observations that contradict these findings. As IVF, ICSI, frozen-thawed embryo transfer, and PGD manipulate gametes and embryo at a time that is important for reprogramming, they may affect epigenetic stability, leading to gamete/embryo origins of adult diseases. In fact, ART offspring have been reported to have an increased risk of gamete/embryo origins of adult diseases, such as early-onset diabetes, cardiovascular disease, and so on. In this review, we will discuss evidence related to genetic, especially epigenetic, risks of assisted reproduction.

[A survey of pubertal development in children born with assisted reproductive technology]

OBJECTIVE

To investigate the status of pubertal development in children born with assisted reproductive technology (ART).

METHODS

A retrospective analysis was performed on the pubertal development data of children born with ART in Peking University Third Hospital from 1994 to 2003 (ART group). The data in the cross-sectional study "Reports on the Physical Fitness and Health Research of Chinese School Students in 2010" were used as a control. The age at menarche and the age at spermarche were compared between the two groups. The status of pubertal development in the overweight and obese children in the ART group was evaluated to investigate the correlation between pubertal development and body mass index (BMI).

RESULTS

A total of 200 children born with ART were enrolled in this study, and 72 of them (41 males and 31 females) completed the survey (response rate=36.0%). In the ART group, the mean age at spermarche and the mean age at menarche were 13.9 years (95%CI: 13.7-14.3 years) and 12.2 years (95%CI: 11.8-12.6 years), respectively. There were no significant differences in the age at spermarche and the age at menarche between the ART and control groups (P>0.05). In the ART group, there were no significant differences in the age at spermarche and the age at menarche between the overweight and obese children and the normal weight children (P>0.05). There were also no significant differences in overweight rate and obesity rate between the children in the ART group and the adolescents in Beijing (P>0.05). In the ART group, there was no significant correlation between the age at spermarche or menarche and BMI (P>0.05).

CONCLUSIONS

No delayed or precocious puberty is observed in children born with ART. This is consistent with the normal control data. And there is no significant correlation between pubertal development and BMI in children born with ART.

Assisted reproductive technology alters deoxyribonucleic acid methylation profiles in bloodspots of newborn infants

OBJECTIVE

To evaluate the effect of infertility and intracytoplasmic sperm injection (ICSI) on DNA methylation of offspring.

DESIGN

Microarray analysis of DNA methylation in archived neonatal bloodspots of in vitro fertilization (IVF)/ICSI-conceived children compared with controls born to fertile and infertile parents.

SETTING

Academic research laboratory.

PATIENT(S)

Neonatal blood spots of 137 newborns conceived spontaneously, through intrauterine insemination (IUI), or through ICSI using fresh or cryopreserved (frozen) embryo transfer.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

The Illumina Infinium HumanMethylation450k BeadChip assay determined genome-wide DNA methylation. Methylation differences between conception groups were detected using a Bioconductor package, ChAMP, in conjunction with Adjacent Site Clustering (A-clustering).

RESULT(S)

The methylation profiles of assisted reproductive technology and IUI newborns were dramatically different from those of naturally (in vivo) conceived newborns. Interestingly, the profiles of ICSI-frozen (FET) and IUI infants were strikingly similar, suggesting that cryopreservation may temper some of the epigenetic aberrations induced by IVF or ICSI. The DNA methylation changes associated with IVF/ICSI culture conditions and/or parental infertility were detected at metastable epialleles, suggesting a lasting impact on a child's epigenome.

CONCLUSION(S)

Both infertility and ICSI alter DNA methylation at specific genomic loci, an effect that is mitigated to some extent by FET. The impact of assisted reproductive technology and/or fertility status on metastable epialleles in humans was uncovered. This study provides an expanded set of loci for future investigations on IVF populations.

The impact of assisted reproductive technologies on genomic imprinting and imprinting disorders

PURPOSE OF REVIEW

Genomic imprinting refers to preferential allele-specific gene expression. DNA methylation-based molecular mechanisms regulate establishment and maintenance of parental imprints during early embryo development and gametogenesis. Because of the coincident timing, a potential association between assisted reproductive technology (ART) procedures and imprinting defects has been investigated in various studies. In this review, we provide an overview of genomic imprinting and present a summary of the relevant clinical data.

RECENT FINDINGS

ART procedures affect DNA methylation pattern, parental imprinting status, and imprinted gene expression in the mouse embryo. In humans, several case series suggested an association between ART and imprinting disorders, with a three-fold to six-fold higher prevalence of ART use among children born with Beckwith-Wiedemann syndrome compared to the general population. However, more recent studies failed to support these findings and could not demonstrate an association between imprinting disorders and ARTs, independent of subfertility.

SUMMARY

ART procedures may affect methylation status of imprinted regions in the DNA, leading to imprinting disorders. Although the low prevalence of imprinting disorders makes it challenging to perform conclusive clinical trials, further studies in large registries are required to determine the real impact of ARTs on their occurrence.

In vitro maturation of oocytes is not associated with altered deoxyribonucleic acid methylation patterns in children from in vitro fertilization or intracytoplasmic sperm injection

OBJECTIVE

To study the possible transmission, to the next generation, of epigenetic defects associated with in vitro maturation (IVM) of human oocytes.

DESIGN

Case-control study using epigenetic data.

SETTING

Two collaborating university departments.

PATIENT(S)

Eleven IVM newborns and 19 controls, conceived by conventional assisted reproduction.

INTERVENTION(S)

Chorionic villus and cord-blood sampling.

MAIN OUTCOME MEASURE(S)

Using bisulfite pyrosequencing, we have measured average methylation levels of 6 imprinted (LIT1, MEG, MEST, NESPas, PEG3, and SNRPN), 5 tumor-suppressor (APC, ATM, BRCA1, RAD51C, and TP53), 2 pluripotency (NANOG and OCT4), and 2 metabolic (LEP and NR3C1) genes, as well as 2 repetitive elements (ALU and LINE1) in 2 tissues of IVM and control neonates. Using deep bisulfite sequencing, we have determined methylation patterns of many individual DNA molecules to detect rare RAD51C epimutations (allele methylation errors).

RESULT(S)

No statistically significant impact was found of IVM on chorionic villus and cord-blood DNA methylation at the studied developmentally important genes and interspersed repeats. The RAD51C epimutation rate was low (0.5% ± 0.1%) in all analyzed samples.

CONCLUSION(S)

IVM-induced epigenetic changes in offspring, if any, are relatively small in magnitude and/or infrequent.

Abnormal DLK1/MEG3 imprinting correlates with decreased HERV-K methylation after assisted reproduction and preimplantation genetic diagnosis

Retrotransposons participate in cellular responses elicited by stress, and DNA methylation plays an important role in retrotransposon silencing and genomic imprinting during mammalian development. Assisted reproduction technologies (ARTs) may be associated with increased stress and risk of epigenetic changes in the conceptus. There are similarities in the nature and regulation of LTR retrotransposons and imprinted genes. Here, we investigated whether the methylation status of Human Endogenous Retroviruses (HERV)-K LTR retrotransposons and the imprinting signatures of the DLK1/MEG3. p57(KIP2) and IGF2/H19 gene loci are linked during early human embryogenesis by examining trophoblast samples from ART pregnancies and preimplantation genetic diagnosis (PGD) cases and matched naturally conceived controls. Methylation analysis revealed that HERV-Ks were totally methylated in the majority of controls while, in contrast, an altered pattern was detected in ART-PGD samples that were characterized by a hemi-methylated status. Importantly, DLK1/MEG3 demonstrated disturbed methylation in ART-PGD samples compared to controls and this was associated with altered HERV-K methylation. No differences were detected in p57(KIP2) and IGF2/H19 methylation patterns between ART-PGD and naturally conceived controls. Using bioinformatics, we found that while the genome surrounding the p57(KIP2) and IGF2/H19 genes differentially methylated regions had low coverage in transposable element (TE) sequences, the respective one of DLK1/MEG3 was characterized by an almost 2-fold higher coverage. Moreover, our analyses revealed the presence of KAP1-binding sites residing within retrotransposon sequences only in the DLK1/MEG3 locus. Our results demonstrate that altered HERV-K methylation in the ART-PGD conceptuses is correlated with abnormal imprinting of the DLK1/MEG3 locus and suggest that TEs may be affecting the establishment of genomic imprinting under stress conditions.

Stability of genomic imprinting and gestational-age dynamic methylation in complicated pregnancies conceived following assisted reproductive technologies

For the past three decades, assisted reproductive technologies (ART) have revolutionized infertility treatments. The use of ART is thought to be safe. However, early investigations suggested that children born as a result of ART had higher risk of diseases with epigenetic etiologies, including imprinting disorders caused by a lack of maternal methylation at imprinting control elements. In addition, large epidemiology studies have highlighted an increased risk of obstetric complications, including severe intrauterine growth restriction (IUGR) in babies conceived using ART. It is plausible that the increased frequency of IUGR may be due to abnormal imprinting because these transcripts are key for normal fetal growth and development. To address this, we have collected a large cohort of placenta and cord blood samples from ART conceptions and compared the imprinting status with appropriate non-ART population. Using a custom DNA methylation array that simultaneously quantifies 25 imprinted differentially methylated regions, we observed similar epigenetic profiles between groups. A multiplex Sequenom iPLEX allelic expression assay revealed monoallelic expression for 11 imprinted transcripts in our placenta cohort. We also observe appropriate gestational age-dependent methylation dynamics at retrotransposable elements and promoters associated with growth genes in ART placental biopsies. This study confirms that children conceived by ART do not show variability in imprinted regulation and that loss-of-imprinting is not commonly associated with nonsyndromic IUGR or prematurity.

Ovulation induction and epigenetic anomalies

In this systematic review of ovulation induction and epigenetic control, studies mainly done in the mouse model highlight how hormone treatments may be prejudicial to the epigenetic reprogramming of gametes as well as early embryos. Moreover, the hormone protocols used in assisted reproduction may also modify the physiologic environment of the uterus, a potential link to endometrial epigenetic disturbances. At present, the few available data in humans are insufficient to allow us to independently determine the impact of a woman's age and infertility problems and treatment protocols and hormone doses on such processes as genomic imprinting.

Meeting the methodological challenges in molecular mapping of the embryonic epigenome

The past decade of life sciences research has been driven by progress in genomics. Many voices are already proclaiming the post-genomics era, in which phenomena other than sequence polymorphism influence gene expression and also explain complex phenotypes. One of these burgeoning fields is the study of the epigenome. Although the mechanisms by which chromatin structure and reorganization as well as cytosine methylation influence gene expression are not fully understood, they are being invoked to explain the now-accepted long-term impact of the environment on gene expression, which appears to be a factor in the development of numerous diseases. Such studies are particularly relevant in early embryonic development, during which waves of epigenetic reprogramming are known to have profound impacts. Since gametes and zygotes are in the process of resetting the genome in order to create embryonic stem cells that will each differentiate to create one of many specific tissue types, this phase of life is now viewed as a window of susceptibility to epigenetic reprogramming errors. Epigenetics could explain the influence of factors such as the nutritional/metabolic status of the mother or the artificial environment of assisted reproductive technologies. However, the peculiar nature of early embryos in addition to their scarcity poses numerous technological challenges that are slowly being overcome. The principal subject of this article is to review the suitability of various current and emerging technological platforms to study oocytes and early embryonic epigenome with more emphasis on studying DNA methylation. Furthermore, the constraint of samples size, inherent to the study of preimplantation embryo development, was put in perspective with the various molecular platforms described.

Genomic imprints as a model for the analysis of epigenetic stability during assisted reproductive technologies

Gamete and early embryo development are important stages when genome-scale epigenetic transitions are orchestrated. The apparent lack of remodeling of differential imprinted DNA methylation during preimplantation development has lead to the argument that epigenetic disruption by assisted reproductive technologies (ARTs) is restricted to imprinted genes. We contend that aberrant imprinted methylation arising from assisted reproduction or infertility may be an indicator of more global epigenetic instability. Here, we review the current literature on the effects of ARTs, including ovarian stimulation,in vitrooocyte maturation, oocyte cryopreservation, IVF, ICSI, embryo culture, and infertility on genomic imprinting as a model for evaluating epigenetic stability. Undoubtedly, the relationship between impaired fertility, ARTs, and epigenetic stability is unquestionably complex. What is clear is that future studies need to be directed at determining the molecular and cellular mechanisms giving rise to epigenetic errors.

Similar DNA methylation levels in specific imprinting control regions in children conceived with and without assisted reproductive technology: a cross-sectional study

Background

While a possible link between assisted reproductive technology (ART) and rare imprinting disorders has been found, it is not clear if this is indicative of subtler disruptions of epigenetic mechanisms. Results from previous studies have been mixed, but some methylation differences have been observed.

Methods

Children conceived through ART and children conceived spontaneously were recruited for this cross-sectional study. Information about reproductive history, demographic factors, birth characteristics, and infertility treatment was obtained from maternal interview and medical records. Peripheral blood lymphocytes and buccal cell samples were collected from participating children. Methylation analysis was performed on five loci using pyrosequencing. Statistical analysis of methylation differences was performed using linear regression with generalized estimating equations. Results are reported as differences with 95% confidence intervals (CI).

Results

A total of 67 ART children and 31 spontaneously conceived (SC) children participated. No significant difference in methylation in lymphocyte samples was observed between groups for any loci. Possible differences were found in buccal cell samples for IGF2 DMR0 (Difference: 2.07; 95% confidence interval (CI): -0.28, 4.42; p = 0.08) and IGF2R (Difference: -2.79; 95% CI: -5.74, 0.16; p = 0.06). Subgroup analysis indicated potential lower methylation in those whose parents used ART for unexplained infertility.

Conclusions

Observed differences in methylation between the ART and SC groups were small for all loci in the two sample types examined and no statistical differences were observed. It is still unclear whether or not small differences observed in several studies represent a real difference between groups and if this difference is biologically meaningful. Larger studies with long term follow-up are needed to fully answer these questions.

Assisted reproduction treatment and epigenetic inheritance

BACKGROUND

The subject of epigenetic risk of assisted reproduction treatment (ART), initiated by reports on an increase of children with the Beckwith–Wiedemann imprinting disorder, is very topical. Hence, there is a growing literature, including mouse studies.

METHODS

In order to gain information on transgenerational epigenetic inheritance and epigenetic effects induced by ART, literature databases were searched for papers on this topic using relevant keywords.

RESULTS

At the level of genomic imprinting involving CpG methylation, ART-induced epigenetic defects are convincingly observed in mice, especially for placenta, and seem more frequent than in humans. Data generally provide a warning as to the use of ovulation induction and in vitro culture. In human sperm from compromised spermatogenesis, sequence-specific DNA hypomethylation is observed repeatedly. Transmittance of sperm and oocyte DNA methylation defects is possible but, as deduced from the limited data available, largely prevented by selection of gametes for ART and/or non-viability of the resulting embryos. Some evidence indicates that subfertility itself is a risk factor for imprinting diseases. As in mouse, physiological effects from ART are observed in humans.

In the human, indications for a broader target for changes in CpG methylation than imprinted DNA sequences alone have been found. In the mouse, a broader range of CpG sequences has not yet been studied. Also, a multigeneration study of systematic ART on epigenetic parameters is lacking.

CONCLUSIONS

The field of epigenetic inheritance within the lifespan of an individual and between generations (via mitosis and meiosis, respectively) is growing, driven by the expansion of chromatin research. ART can induce epigenetic variation that might be transmitted to the next generation.

General imprinting status is stable in assisted reproduction-conceived offspring

OBJECTIVE

To evaluate whether the genomic imprinting status of assistant reproductive technology (ART)-conceived offspring is stable.

DESIGN

Prospective clinical observational study.

SETTING

In vitro fertilization (IVF) center, university-affiliated teaching hospital.

PATIENT(S)

Sixty ART-conceived babies (30 IVF and 30 intracytoplasmic sperm injection [ICSI]) and 60 naturally conceived babies.

INTERVENTION(S)

Collection of umbilical cord blood and peripheral blood samples.

MAIN OUTCOME MEASURE(S)

Expression profile was examined by microarray and real-time reverse-transcription polymerase chain reaction (PCR), allele-specific expression was studied by direct sequencing after PCR, and DNA methylation status was investigated by sodium bisulfite sequencing.

RESULT(S)

Hierarchic clustering demonstrated no obvious clustering between the ART- and naturally conceived offspring, suggesting similar genomic imprinting expression between the two groups. Three differentially expressed genes were identified in ART-conceived offspring, with PEG10 and L3MBTL up-regulated and PHLDA2 down-regulated. Allele-specific expression of the differentially expressed imprinted genes was maintained in the majority of the ART- and naturally conceived offspring. However, in one ICSI case, monoallelic expression of L3MBTL was disrupted and all CpGs were completely unmethylated. These were not inherited from the parents.

CONCLUSION(S)

The global profile of imprinting is stable in children conceived through ART. However, imprinting of a few specific imprinted genes may be vulnerable in a fraction of ART-conceived children.

Study of DNA methylation patterns of imprinted genes in children born after assisted reproductive technologies reveals no imprinting errors: A pilot study

Assisted reproductive technology (ART) including in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) have been shown to be associated with abnormal genomic imprinting, thus increasing the incidence of imprinting disorders such as Beckwith-Wiedemann syndrome (BWS) and Angelman syndrome (AS) in ART-conceived children. Furthermore, a recent study described abnormal DNA methylation in clinically normal children conceived by ART. However, data from different studies are conflicting or inconclusive. This study examined DNA methylation patterns of multiple imprinted genes in children born after ART to primarily evaluate the impact of ART on genomic imprinting. A total of 101 newborns conceived by ART (40 ICSI and 61 IVF) and 60 naturally conceived newborns were involved in our study. After obtaining the approval of the Institutional Ethics Committee, umbilical cord blood was collected from each infant. Genomic DNA was isolated from each blood sample and treated using sodium bisulfite. Subsequently, using methylation-specific PCR (MS-PCR), we analyzed six differentially methylated regions (DMRs) including KvDMR1, SNRPN, MEST, MEG3, TNDM and XIST. Meanwhile, information regarding twin pregnancies, gestational age, and birth weight of the neonates was documented. None of the cases presented with phenotypic abnormalities. Children conceived by ART were more likely to have low birth weight and to be born before term, compared with children conceived spontaneously. However, 7 months to 3 years of clinical follow-up showed that none of the children had clinical symptoms of any imprinting diseases. Furthermore, the MS-PCR results showed that all 161 children had normal DNA methylation patterns at six DMRs despite the different mode of conception. Our data did not indicate a higher risk of DNA-methylation defects in children born after ART. However, further studies using quantitative methods are needed to confirm these results.

Imprinting disorders and assisted reproductive technology

PURPOSE OF REVIEW

To summarize current evidence in the association of imprinting disorders and assisted reproductive technology.

RECENT FINDINGS

The worldwide usage of assisted reproductive technology (ART) has continued to increase since the first successful birth of a human after IVF. Since 2002, several reports have raised concerns that children conceived by ART are at increased risk of having imprinting disorders. The majority of published studies have examined DNA methylation in children conceived by ART, but results are conflicting. Beckwith-Wiedemann syndrome and Angelman syndrome are the most extensively studied imprinting disorders and multiple case series and reports have been published on ART-conceived children with these syndromes. Overall the majority of reports suggest that ART might be associated with Beckwith-Wiedermann syndrome and Angelman syndrome, but larger collaborative studies need to be performed.

SUMMARY

The current data suggest an association between imprinting disorders and ART although the absolute risk appears to be low. However, animal studies have established biologic plausibility and there is continuing concern about the possibility of epigenetic changes resulting from ART.

In vitro fertilization and embryo culture strongly impact the placental transcriptome in the mouse model

Background

Assisted Reproductive Technologies (ART) are increasingly used in humans; however, their impact is now questioned. At blastocyst stage, the trophectoderm is directly in contact with an artificial medium environment, which can impact placental development. This study was designed to carry out an in-depth analysis of the placental transcriptome after ART in mice.

Methodology/Principal Findings

Blastocysts were transferred either (1) after in vivo fertilization and development (control group) or (2) after in vitro fertilization and embryo culture. Placentas were then analyzed at E10.5. Six percent of transcripts were altered at the two-fold threshold in placentas of manipulated embryos, 2/3 of transcripts being down-regulated. Strikingly, the X-chromosome harbors 11% of altered genes, 2/3 being induced. Imprinted genes were modified similarly to the X. Promoter composition analysis indicates that FOXA transcription factors may be involved in the transcriptional deregulations.

Conclusions

For the first time, our study shows that in vitro fertilization associated with embryo culture strongly modify the placental expression profile, long after embryo manipulations, meaning that the stress of artificial environment is memorized after implantation. Expression of X and imprinted genes is also greatly modulated probably to adapt to adverse conditions. Our results highlight the importance of studying human placentas from ART.

Imprinting disorders and assisted reproductive technology

Worldwide use of assisted reproductive technology (ART) accounts for an estimated 1 to 3% of births. Since 2002, a series of reports have suggested an increased risk of imprinting disorders (Beckwith-Wiedemann syndrome and Angelman syndrome) in children conceived by ART. Definitive conclusions are difficult to substantiate due to the rarity of imprinting disorders and the variability in ART protocols. Despite these limitations, there is biological plausibility for alteration in nongenomic inheritance caused by ART. Animal studies have shown that ART procedures can alter normal imprinting, specifically DNA methylation patterns. Collectively, studies suggest an association between ART and loss of maternal methylation. More recent reports examined a possible association between ART and global hypomethylation of DNA. Three other imprinting disorders (Silver-Russell syndrome, maternal hypomethylation syndrome, and retinoblastoma) have also been implicated, but there is insufficient evidence to establish an association of these syndromes with ART. Based on current evidence, the absolute risk of imprinting disorders after ART remains small and does not warrant routine screening. Large prospective studies are needed to better understand the risks associated with imprinting disorders, imprinting defects, and ART.

ICSI: Hype or hazard?

Ever since its introduction in clinical practice more than 10 years ago, intracytoplasmic sperm injection (ICSI) has been the subject of ongoing debate regarding its indications and safety. ICSI is hyped because of its potential to give couples with severe male factor infertility a chance to conceive, and because of its apparently low fertilization failure rate compared with 'classic' in vitro fertilization (IVF). Concerns about ICSI are related to technical, biological and genetic hazards. ICSI has been branded 'the ultimate rape of the oocyte', as the oocyte membrane is mechanically pierced, appearing to bypass all biological and genetic selection. ICSI has been linked in a number of reports to an increased incidence of chromosomal anomalies, congenital abnormalities and perinatal hazards in offspring conceived with this technique. The etiology of the increased risk of chromosomal anomalies in ICSI offspring, especially sex-chromosome anomalies, is thought to be partly multifactorial, partly andrological, related to paternal karyotypic abnormalities and/or abnormal sperm. The majority of studies on ICSI and IVF offspring have, setting aside inconsistencies in methodology and classification, not shown significant differences between the two techniques in terms of congenital abnormalities, however, compared to naturally conceived offspring there does show an increased risk. This risk is attributed mainly to parental factors such as maternal age, poor sperm quality and infertility as an independent risk factor. Perinatal hazards may include low birth weight and perinatal mortality. Behavioural and psychological development is carefully monitored in ICSI and IVF children with no significant differences to the development of naturally conceived children, but many factors are involved including demographics. Follow-up studies are essential to the technique of ICSI. It is our duty to inform patients of the concerns and benefits to this treatment, based on the latest data available.

Imprinting disorders and assisted reproductive technology

OBJECTIVE

To review currently available literature on the association between imprinting disorders (Beckwith-Wiedemann syndrome [BWS], Angelman syndrome [AS] and retinoblastoma) and assisted reproductive technology (ART) in humans.

DESIGN

Publications related to imprinting/epigenetic disorders including BWS, AS, and retinoblastoma with ART, as well as articles publishing outcome of ART, including IVF and ICSI from July 1978 to February 2008, were identified using PubMed, Medline, and EMBASE.

RESULT(S)

Considerable evidence in animal studies has demonstrated alteration in gene imprinting of embryos cultured in vitro. Publications from Europe, the United States, and Australia have suggested an association between ART and BWS. Importantly, more than 90% of children with BWS that were born after ART had imprinting defects, compared with 40%-50% of children with BWS and conceived without ART. Moreover, there have been other reports suggesting an association between AS and ART. The majority of children with AS born after ART had an imprinting defect as the underlying etiology, specifically loss of methylation of the maternal allele. There was a single report suggesting an increased incidence of retinoblastoma in children conceived with ART.

CONCLUSION(S)

Because the absolute incidence of imprinting disorders is small (<1:12,000 births), routine screening for imprinting disorders in children conceived by ART is not recommended. Additional large cohort studies of children born after ART are needed to determine whether there is a genuine association between ART and imprinting disorders.

Epigenetic consequences of assisted reproduction and infertility on the human preimplantation embryo

Epigenetic information, which is essential for normal mammalian development, is acquired during gametogenesis and further regulated during preimplantation development. The epigenetic consequences of assisted reproductive technologies (ARTs) and infertility on the health and quality of the human preimplantation embryo are considered in this review. In the zygote, the epigenetic information that is inherited from the sperm and the oocyte intersects and must be appropriately recognized, regulated and then propagated during preimplantation development so as to regulate gene expression in an appropriate manner. A growing body of evidence suggests that ARTs and/or infertility itself may affect these complex processes leading to epigenetic diseases that include disorders of genomic imprinting. The epigenetic safety of human gametes and embryos is of paramount importance. Unfortunately, morphological methods of assessing embryo quality are incapable of detecting epigenetic errors. Further research is therefore critical to resolve these issues.

Promoter hypermethylation of the MEG3 (DLK1/MEG3) imprinted gene in multiple myeloma

BACKGROUND

Methylation represents the most studied epigenetic modification and results in the silencing of genes involved in various processes such as differentiation and cell-cycle regulation. MEG3 represents an imprinted gene maternally expressed in humans that encodes a nontranslated product. In this survey, we studied the methylation status of the specific gene in multiple myeloma (MM).

PATIENTS AND METHODS

Twenty-one patients with MM (17 with immunoglobulin [Ig] G, 3 with IgA, and 1 with IgM) were evaluated using methylation-specific polymerase chain reaction (after DNA bisulphite modification).

RESULTS

Promoter hypermethylation was observed in 12 (57.14%) bone marrow samples and in 9 of 14 (64.28%) available peripheral blood samples. A correlation with disease stage was also observed and also with the disease subtype (IgG, 64.7%; IgA, 0; IgM, 100%).

CONCLUSION

We conclude that promoter hypermethylation of the differentially methylated region of the MEG3 imprinted gene is observed in patients with MM.

Multiple orofacial malformations in a boy who was conceived by intracytoplasmic sperm injection

Intracytoplasmic sperm injection (ICSI) and other assisted reproductive technologies (ART) are effective treatments for infertility and are widely used at infertility clinics. Although ICSI is generally considered safe, some studies have suggested an excess occurrence of major birth defects resulting from the procedure. Here, we present a rare case of a boy with multiple orofacial malformations who was conceived by ICSI. We suggest therefore that the risk of genetics abnormalities should be discussed in detail with the parents and sufficient informed consent should be obtained before starting ICSI procedures.

The risk of malformation following assisted reproduction

INTRODUCTION

Intracytoplasmatic sperm injection (ICSI) is currently the most frequently used human reproductive technology in Germany. ICSI was introduced as routine, insurance-funded medical care in 2002 by the Federal Joint Committee. A re-evaluation of published literature on malformation rates in children born of ICSI pregnancies within a period of three years formed part of the committee's decision. The analysis investigated whether ICSI increases the risk of malformation in the offspring, compared to in vitro fertilization (IVF) and natural conception.

METHODS

Systematic literature review.

RESULTS

929 studies were identified. Three meta-analyses, 15 studies investigating malformations, and 12 studies analyzing imprinting disorders were included. The risk of malformation was not significantly different in nine studies comparing ICSI versus IVF. Two meta-analyses and three of eight cohort studies and retrospective analysis showed significantly more severe malformations after assisted reproduction than after natural conception. The remaining five studies displayed no significant results. Current evidence does not show a higher risk of major malformations in the offspring resulting from the use of ICSI compared to IVF. However, there is evidence that both techniques increase the risk for major malformations considerably, compared to natural conception, and further research is needed. The validity of the results is low since the studies were heterogeneous and the cohorts used in the studies had limited comparability.

In vitro spermatogenesis as a method to bypass pre-meiotic or post-meiotic barriers blocking the spermatogenetic process: genetic and epigenetic implications in assisted reproductive technology

Pregnancies achieved by assisted reproduction technologies and particularly by ooplasmic injections of either in vivo or in vitro generated immature male germ cells are susceptible to genetic risks inherent to the male population treated with assisted reproduction and additional risks inherent to these innovative procedures. The documented, as well as the theoretical risks, are discussed in this review. These risks represent mainly the consequences of genetic abnormalities underlying male infertility and may become stimulators for the development of novel approaches and applications in the treatment of infertility. Recent data suggest that techniques employed for in vitro spermatogenesis, male somatic cell haploidization, stem cell differentiation in vitro and assisted reproductive technology may also affect the epigenetic characteristics of the male gamete, the female gamete, or may have an impact on early embryogenesis. They may be also associated with an increased risk for genomic imprinting abnormalities. Production of haploid male gametes in vitro may not allow the male gamete to undergo all the genetic and epigenetic alterations that the male gamete normally undergoes during in vivo spermatogenesis.

Epigenetics in assisted reproductive technology

It has been reported that the rates of epigenetic disorders such as Angelman syndrome (AS) and Beckwith-Wiedemann syndrome (BWS) are high in offspring conceived by assisted reproductive technology (ART). Angelman Syndrome is characterized by intellectual disability and BWS is known as large offspring syndrome (LOS). Weight abnormalities have also been reported in cloned animals. Possible factors underlying these findings include inherent gamete characteristics, influence of in vitro culture and peculiarity of ART methods. It is important to conclusively determine whether such epigenetic abnormalities are present in children conceived by ART, so as to consider the health of next generations.

Epigenetics in reproductive medicine

Imprinted genes comprise a small subset of the genome whose epigenetic reprogramming in the germ line is necessary for subsequent normal embryonic development. This reprogramming and resetting of the imprints, through an erasure/acquisition/maintenance cycle, is a subtle and tightly orchestrated phenomenon, involving specific genomic regions and methylation enzymes. Dysregulation of imprinted genes has indeed been shown to lead to several human disorders as well as to affect placental and fetal growth. There have been numerous and conflicting studies assessing the possible association of imprinting disorders with assisted reproductive techniques. This work analyzes all relevant and available reports with regard to the association between assisted reproductive techniques and imprinting disorders. It also discusses whether this possibly increased risk of imprinting disorders may be linked to specific steps of these reproductive techniques or already present in the gametes of infertile patients. A better understanding of epigenetic reprogramming in the germ line is absolutely necessary both to assess the safety of these methods and of the use of impaired spermatogenesis gametes for assisted reproduction.

Comparison of mice born after intracytoplasmic sperm injection with in vitro fertilization and natural mating

The procedures of in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) are routinely used in modern medicine to overcome infertility and, in animal husbandry, to propagate lines with compromised fertility. However, there remains concern that manual selection and injection of whole sperm into oocytes could contribute to pre- and postnatal developmental defects. To address this, we have used gene expression profiling and immunophenotyping to characterize offspring generated by these procedures. We used gametes from glutathione peroxidase 1 knockout (Gpx1-/-) mice as a sensitized screen responsive to oxidative stress from artificial reproduction technologies (ART). There were no differences between IVF and ICSI derived offspring in gene expression patterns, and minor differences in hematopoietic parameters. Furthermore there were only minor differences between these IVF and ICSI pups and those derived from natural mating. These data demonstrate for the first time in that there is no significant phenotypic affects of ICSI when compared to IVF and we identified a relatively minor influence of the artificial fertilization methods on phenotype of offspring compared with natural mating. These observations would support the use of ICSI for derivation of mutant mouse lines and may be of some importance for the use of this technique in human ART.

Increased frequency of severe major anomalies in children conceived by intracytoplasmic sperm injection

The neurodevelopmental outcome of children born after intracytoplasmic sperm injection (ICSI) is controversial. We compared the medical and developmental outcome of 34 singletons born after ICSI (20 males, 14 females; mean ages of 18 mo and 40 mo [SD 9 mo]; range 2 y 10 mo-4 y 8 mo) with 39 case control studies (21 males, 18 females; mean ages of 18 mo and 40 mo [SD 4 mo]; range 3 y-4 y 1 mo). Each child was assessed physically and tested in three development domains (fine motor, gross motor, and language). Five children born after ICSI versus two control children (p=0.2) had major congenital anomalies (MaCAs). Four children born after ICSI versus no control children had severe MaCAs (p=0.04). These were defined as having a significant impact on development or causing chronic disease: Angelman syndrome (n=1), lissencephaly (n=1), Hanhart syndrome (n=1), and persistent hyperinsulinemic hypoglycaemia of infancy (n=1). Karyotyping in 23 children born after ICSI revealed no abnormalities. An imprinting defect was found in the child with Angelman syndrome. Results of developmental assessment were in all cases normal at the age of 18 months except for the three children with Angelman and Hanhart syndromes, and lissencephaly. At the second assessment, five more children born after ICSI and four control children showed abnormalities in one or more developmental domains. We conclude that there seems to be a higher frequency of severe major anomalies in children born after ICSI. An increased risk for imprinting defects cannot be excluded. If we exclude children with severe MaCAs, the incidence of an abnormal somatic or neurodevelopmental outcome in the fourth year of life in children born after ICSI is similar to that of spontaneously conceived children.

Genetic and epigenetic risks of intracytoplasmic sperm injection method

Pregnancies achieved by assisted reproduction technologies, particularly by intracytoplasmic sperm injection (ICSI) procedures, are susceptible to genetic risks inherent to the male population treated with ICSI and additional risks inherent to this innovative procedure. The documented, as well as the theoretical, risks are discussed in the present review study. These risks mainly represent that consequences of the genetic abnormalities underlying male subfertility (or infertility) and might become stimulators for the development of novel approaches and applications in the treatment of infertility. In addition, risks with a polygenic background appearing at birth as congenital anomalies and other theoretical or stochastic risks are discussed. Recent data suggest that assisted reproductive technology might also affect epigenetic characteristics of the male gamete, the female gamete, or might have an impact on early embryogenesis. It might be also associated with an increased risk for genomic imprinting abnormalities.

Methylation status of the SNRPN and HUMARA genes in testicular biopsy samples

OBJECTIVE

To analyze the methylation status of two differentially inherited and methylated loci (the human androgen receptor [HUMARA] and the small nuclear ribonucleoprotein-associated polypeptide N [SNRPN] gene) in testicular biopsy samples, and to compare the results with microscopic evaluation.

DESIGN

Retrospective study.

SETTING

Infertility clinics and genetics laboratories.

PATIENT(S)

Twelve obstructive and 74 nonobstructive azoospermic men.

INTERVENTION(S)

Deoxyribonucleic acid samples from testicular biopsies and peripheral blood were modified with sodium bisulfite and amplified by methylation-specific polymerase chain reaction assay. Polymerase chain reaction primers specific for the methylated regions of the HUMARA locus and for the methylated and unmethylated CpG islands of the SNRPN gene were used.

MAIN OUTCOME MEASURE

Polymerase chain reaction product bands specific for methylated and unmethylated alleles.

RESULT(S)

Obstructive azoospermia patients were positive for spermatozoa and germ cells by all approaches (microscopic, HUMARA, and SNRPN analysis) with absolute consistency. In contrast, for the nonobstructive men, microscopy was consistent with SNRPN analysis as regards the presence of germ cells in 82% of the testicular tissues tested. Nonobstructive patients with maturation arrest were positive for the presence of germ cells only by HUMARA analysis, with 84% sensitivity.

CONCLUSION(S)

Methylation analysis of testicular tissue is consistent with microscopic analysis, in terms of the prevalence of germ cells and the stage of spermatogenic arrest in biopsy samples.

A prospective randomized trial of conventional in vitro fertilization versus intracytoplasmic sperm injection in unexplained infertility

PURPOSE

To compare outcomes in patients with unexplained infertility undergoing conventional in vitro fertilization (IVF) versus intracytoplasmic sperm injection (ICSI).

METHODS

Sixty women with unexplained infertility in a Canadian tertiary-level clinic were randomized to IVF or ICSI. Subjects underwent downregulation with gonadotropin-releasing hormone agonist prior to initiation of recombinant human follicle-stimulating hormone. The primary outcome measure was fertilization rate. Secondary outcomes included implantation rate, embryo quality, clinical pregnancy rate, and live birth rate.

RESULTS

There was no statistically significant difference in fertilization rate (77.2% IVF vs. 82.4% ICSI), implantation rate (38.2% IVF vs. 44.4% ICSI), clinical pregnancy rate (50% in each group), or live birth rate (46.7% IVF vs. 50% ICSI). There were two cases of failed fertilization in the IVF group. There was no significant difference in embryo quality between groups.

CONCLUSIONS

There were no differences in clinical outcomes associated with IVF versus ICSI in the treatment of unexplained infertility.