Safety of assisted reproduction, assessed by risk of abnormalities in children born after use of in vitro fertilization techniques

Mechanisms of epigenetic remodelling during preimplantation development

Epigenetics involves mechanisms independent of modifications in the DNA sequence that result in changes in gene expression and are maintained through cell divisions. Because all cells in the organism contain the same genetic blueprint, epigenetics allows for cells to assume different phenotypes and maintain them upon cell replication. As such, during the life cycle, there are moments in which the epigenetic information needs to be reset for the initiation of a new organism. In mammals, the resetting of epigenetic marks occurs at two different moments, which both happen to be during gestation, and include primordial germ cells (PGCs) and early preimplantation embryos. Because epigenetic information is reversible and sensitive to environmental changes, it is probably no coincidence that both these extensive periods of epigenetic remodelling happen in the female reproductive tract, under a finely controlled maternal environment. It is becoming evident that perturbations during the extensive epigenetic remodelling in PGCs and embryos can lead to permanent and inheritable changes to the epigenome that can result in long-term changes to the offspring derived from them, as indicated by the Developmental Origins of Health and Disease (DOHaD) hypothesis and recent demonstration of inter- and trans-generational epigenetic alterations. In this context, an understanding of the mechanisms of epigenetic remodelling during early embryo development is important to assess the potential for gametic epigenetic mutations to contribute to the offspring and for new epimutations to be established during embryo manipulations that could affect a large number of cells in the offspring. It is of particular interest to understand whether and how epigenetic information can be passed on from the gametes to the embryo or offspring, and whether abnormalities in this process could lead to transgenerationally inheritable phenotypes. The aim of this review is to highlight recent progress made in understanding the nature and mechanisms of epigenetic remodelling that ensue after fertilisation.

Psychological adjustment in adolescents conceived by assisted reproduction techniques: a systematic review

BACKGROUND

Adolescence is a transitional time for identity formation and relationships with parents. While people born through assisted reproduction techniques (ART) appear to be well adjusted in childhood, it is unclear whether these findings carry into adolescence, and whether diverse ART have different psychological outcomes. This review summarizes what is known about the psychological adjustment and family relationships of the growing number of children born through ART who are reaching adolescence.

METHODS

The Pubmed, Web of Knowledge, PsycINFO and Scopus databases were searched systematically for peer reviewed papers focusing on adolescent psychological adjustment and parent-adolescent relationships in families created by ART. Key search inclusion criteria included all papers published in English relating to adolescents aged between 11 and 18 years.

RESULTS

Seventeen publications with varied methodologies were identified by this review. Only papers relating to in vitro fertilization (IVF), egg donation and donor insemination were identified. Results were categorized according to ART that used the parents' own gametes (IVF) and those that involved reproductive donation (egg donation, and donor insemination). Compared with naturally conceived adolescents and standardized normative samples, adolescents born through all ARTs seemed to be equally well adjusted, and to have positive parent-adolescent relationships. Some differences were however identified based on the type of ART used. In particular, the sex of the parent and child, along with age and process of disclosure of the adolescent's conception were identified as key mediators of parent-adolescent relationships in families created by donor insemination.

CONCLUSIONS

The studies in this review indicate that children born through ART have positive parent-adolescent relationships and are well adjusted, with some slight differences based on different ART. The generalizability of findings may be limited by the general low level of disclosure to adolescents in some of the publications, the small sample sizes of studies in the field, along with the large age range that encompasses adolescence. Findings should also be interpreted in light of the fact that many publications focus on singleton births. Future studies should also focus on egg donation, surrogacy and embryo donation, as well as the disclosure processes, and adolescents born into non-traditional families (same-sex or single parents) or those born using different types of donor (anonymous, identity-release or known).

Transcriptomic signature to oxidative stress exposure at the time of embryonic genome activation in bovine blastocysts

In order to understand how in vitro culture affects embryonic quality, we analyzed survival and global gene expression in bovine blastocysts after exposure to increased oxidative stress conditions. Two pro-oxidant agents, one that acts extracellularly by promoting reactive oxygen species (ROS) production (0.01 mM 2,2'-azobis (2-amidinopropane) dihydrochloride [AAPH]) or another that acts intracellularly by inhibiting glutathione synthesis (0.4 mM buthionine sulfoximine [BSO]) were added separately to in vitro culture media from Day 3 (8-16-cell stage) onward. Transcriptomic analysis was then performed on resulting Day-7 blastocysts. In the literature, these two pro-oxidant conditions were shown to induce delayed degeneration in a proportion of Day-8 blastocysts. In our experiment, no morphological difference was visible, but AAPH tended to decrease the blastocyst rate while BSO significantly reduced it, indicating a differential impact on the surviving population. At the transcriptomic level, blastocysts that survived either pro-oxidant exposure showed oxidative stress and an inflammatory response (ARRB2), although AAPH induced higher disturbances in cellular homeostasis (SERPINE1). Functional genomics of the BSO profile, however, identified differential expression of genes related to glycine metabolism and energy metabolism (TPI1). These differential features might be indicative of pre-degenerative blastocysts (IGFBP7) in the AAPH population whereas BSO exposure would select the most viable individuals (TKDP1). Together, these results illustrate how oxidative disruption of pre-attachment development is associated with systematic up-regulation of several metabolic markers. Moreover, it indicates that a better capacity to survive anti-oxidant depletion may allow for the survival of blastocysts with a quieter metabolism after compaction.

Health and development of ART conceived young adults: a study protocol for the follow-up of a cohort

BACKGROUND

Use of assisted reproductive technologies (ART) continues to increase, yet little is known of the longer term health of ART conceived offspring. There are some adverse birth outcomes associated with ART conception but the subsequent developmental trajectory is unclear. Undertaking research in this area is challenging due the sensitive nature of the topic and the time elapsed since birth of the ART conceived young adults. The aim of this report is to describe a research protocol, including design and ethical considerations, used to compare the physical and psychosocial health outcomes of ART conceived young adults aged 18-28 years, with their spontaneously conceived peers.

DESIGN

This is a retrospective cohort study of mothers who conceived with ART in Victoria, Australia and gave birth to a singleton child between 1982 and 1992. A current address for each mother was located and a letter of invitation to participate in the study was sent by registered mail. Participation involved completing a telephone interview about her young adult offspring's health and development from birth to the present. Mothers were also asked for consent for the researcher to contact their son/daughter to invite them to complete a structured telephone interview about their physical and psychosocial health. A comparison group of women living in Victoria, Australia, who had given birth to a spontaneously conceived singleton child between 1982 and 1992 was recruited from the general population using random digit dialling. Data were collected from them and their young adult offspring in the same way. Regression analyses were used to evaluate relationships between ART exposure and health status, including birth defects, chronic health conditions, hospital admissions, growth and sexual development. Psychosocial wellbeing, parental relationships and educational achievement were also assessed. Factors associated with the age of disclosure of ART conception were explored with the ART group only.

DISCUSSION

The conceptualization and development of this large project posed a number of methodological, logistical and ethical challenges which we were able to overcome. The lessons we learnt can assist others who are investigating the long-term health implications for ART conceived offspring.

Fertile offspring derived from mouse spermatogonial stem cells cryopreserved for more than 14 years

BACKGROUND

Approximately 80% of childhood cancers can now be cured but a side effect of treatment results in about one-third of the surviving boys being infertile or severely subfertile when they reach reproductive age. Currently, more than 1 in 5000 men of reproductive age who are childhood cancer survivors suffer from this serious quality of life problem. It is possible to obtain a testicular biopsy before treatment to preserve the spermatogonial stem cells (SSCs) of the male by cryopreservation, but the results of long-term storage of SSCs on their subsequent functional ability to generate normal offspring has not been examined in any mammalian species. Moreover, it will be necessary to increase the number of these cryopreserved SSCs to remove any contaminating malignant cells and assure regeneration of spermatogenesis.

METHODS AND RESULTS

In this report, we demonstrate that long-term cryopreservation (>14 years) of testis cells from mouse, rat, rabbit and baboon safeguards SSC viability, and that these cells can colonize the seminiferous tubules of recipient testes. Moreover, mouse and rat SSCs can be cultured and re-establish complete spermatogenesis, and fertile mouse progeny without apparent genetic or epigenetic errors were generated by the sperm produced.

CONCLUSIONS

These findings provide a platform for fertility preservation in prepubertal boys undergoing gonadotoxic treatments.

Outcomes for offspring of men having ICSI for male factor infertility

Since the introduction of intracytoplasmic sperm injection (ICSI) using single sperm isolated from testicular tissue in men with obstructive and non-obstructive azoospermia, or using ejaculated sperm in those with poor semen quality, there have been concerns that this might have adverse effects on the offspring compared to conventional in vitro fertilisation (IVF) and natural conceptions. ICSI is done for reasons other than male factor infertility, and on the whole has not been shown to have any more negative effects than those seen with IVF. There have however, been very few studies of ICSI with a focus on, or large enough numbers to examine, the specific outcomes associated with male factor infertility. From the limited information available in relation to the source of the sperm and aetiology of infertility in the presence of ICSI, there appears to be no increased risk of congenital malformations. There is, however, a small increase in both de novo and inherited chromosome abnormalities. In terms of growth and neurodevelopment, there are very few studies, and so far, no adverse outcomes have been found in young children whose fathers have a sperm defect. The origin of the sperm used in ICSI does not have a major influence on the early life outcomes for the offspring, but transgenerational and epigenetic effects remain unknown. When the male factor infertility is known or thought to be due to a Y-chromosome deletion, this information should be given to the young male offspring at a time that will ensure his own reproductive health and plans are optimized.

Local signalling environments and human male infertility: what we can learn from mouse models

Infertility is one of the most prevalent public health problems facing young adult males in today's society. A clear, treatable cause of infertility cannot be determined in a large number of these patients, and a growing body of evidence suggests that infertility in many of these men may be due to genetic causes. Studies using mouse knockout technology have been integral for examination of normal spermatogenesis and to identify proteins essential for this process, which in turn are candidate genes for human male infertility. Successful spermatogenesis depends on a delicate balance of local signalling factors, and this review focuses on the genes that encode these factors. Normal functioning of all testicular cell types is essential for fertility and might also be crucial to prevent germ cell oncogenesis. Analysis of these signalling processes in spermatogenesis using mouse models has provided investigators with an invaluable tool to effectively translate basic science research to the research of human disease and infertility.

Bibliography. Current world literature

This bibliography is compiled by clinicians from the journals listed at the end of this publication. It is based on literature entered into our database between 1 February 2008 and 31 January 2009 (articles are generally added to the database about two and a half months after publication). In addition, the bibliography contains every paper annotated by reviewers; these references were obtained from a variety of bibliographic databases and published between the beginning of the review period and the time of going to press. The bibliography has been grouped into topics that relate to the reviews in this issue.