Human Gametes Research Articles

Representative Aspects of Some Synthetic Gametes

With the development of new procedures in the production of synthetic human gametes it has become important to re-examine the manner in which reproductive cells, taking part in the generation of children, can be understood. Though this can be attempted from many different perspectives, the present study will examine the possibility of considering gametes as representing the persons from whom they originated. From this perspective, it is possible to suggest that, in procreation, the entirety of each human sperm cell may represent and reveal the man from whom it was produced and the entirety of each human egg cell may represent and reveal the woman from whom it was produced.The possible ethical consequences of using synthetic gametes for those who hold this perspective together with their understanding of relational identity will also be examined.

Artificial gametes: a systematic review of biological progress towards clinical application.

Recent progress in the formation of artificial gametes, i.e. gametes generated by manipulation of their progenitors or of somatic cells, has led to scientific and societal discussion about their use in medically assisted reproduction (MAR). Artificial gametes could potentially help infertile men and women but also post-menopausal women and gay couples conceive genetically related children. This systematic review aimed to provide insight in the progress of biological research towards clinical application of artificial gametes. The electronic database 'Medline/Pubmed' was systematically searched with medical subject heading (MesH) terms, and reference lists of eligible studies were hand searched. Studies in English between January 1970 and December 2013 were selected based on meeting a priori defined starting- and end-points of gamete development, including gamete formation, fertilization and the birth of offspring. For each biologically plausible method to form artificial gametes, data were extracted on the potential to generate artificial gametes that might be used to achieve fertilization and to result in the birth of offspring in animals and humans. The systematic search yielded 2424 articles, and 70 studies were included after screening. In animals, artificial sperm and artificial oocytes generated from germline stem cells (GSCs), embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) have resulted in the birth of viable offspring. Also in animals, artificial sperm and artificial oocytes have been generated from somatic cells directly, i.e. without documentation of intermediate stages of stem- or germ cell development or (epi)genetic status. Finally, although the subsequent embryos showed hampered development, haploidization by transplantation of a somatic cell nucleus into an enucleated donor oocyte has led to fertilized artificial oocytes. In humans, artificial sperm has been generated from ESCs and iPSCs. Artificial human oocytes have been generated from GSCs, ESCs and somatic cells (without documentation of intermediate stages of stem- or germ cell development). Fertilization of a human artificial oocyte after haploidization by transplantation of a somatic cell nucleus into an enucleated donor oocyte was also reported. Normal developmental potential, epigenetic and genetic stability and birth of children has not been reported following the use of human artificial gametes. In animals, artificial oocytes from a male have been created and fertilized and artificial sperm from a female has been fertilized and has resulted in the birth of viable offspring. In humans, artificial sperm has been generated from female iPSCs. To date, no study has reported the birth of human offspring from artificial gametes. Our systematic review of the literature indicated that in animals live births have already been achieved using artificial gametes of varying (cell type) sources. Although experimental biological research is progressing steadily towards future clinical application, data on functionality, safety and efficiency of (human) artificial gametes are still preliminary. Although defining artificial gametes by start- and end-points limited the number of included studies, the search resulted in a clear overview of the subject. Clinical use of artificial gametes would expand the treatment possibilities of MAR and would have implications for society. Before potential clinical use, the societal and ethical implications of artificial gametes should be reflected on.

Artificial gametes from stem cells.

The generation of artificial gametes is a real challenge for the scientific community today. In vitro development of human eggs and sperm will pave the way for the understanding of the complex process of human gametogenesis and will provide with human gametes for the study of infertility and the onset of some inherited disorders. However, the great promise of artificial gametes resides in their future application on reproductive treatments for all these people wishing to have genetically related children and for which gamete donation is now their unique option of parenthood. This is the case of infertile patients devoid of suitable gametes, same sex couples, singles and those fertile couples in a high risk of transmitting serious diseases to their progeny. In the search of the best method to obtain artificial gametes, many researchers have successfully obtained human germ cell-like cells from stem cells at different stages of differentiation. In the near future, this field will evolve to new methods providing not only viable but also functional and safe artificial germ cells. These artificial sperm and eggs should be able to recapitulate all the genetic and epigenetic processes needed for the correct gametogenesis, fertilization and embryogenesis leading to the birth of a healthy and fertile newborn.

Genome-wide analysis of DNA methylation dynamics during early human development.

DNA methylation is globally reprogrammed during mammalian preimplantation development, which is critical for normal development. Recent reduced representation bisulfite sequencing (RRBS) studies suggest that the methylome dynamics are essentially conserved between human and mouse early embryos. RRBS is known to cover 5–10% of all genomic CpGs, favoring those contained within CpG-rich regions. To obtain an unbiased and more complete representation of the methylome during early human development, we performed whole genome bisulfite sequencing of human gametes and blastocysts that covered>70% of all genomic CpGs. We found that the maternal genome was demethylated to a much lesser extent in human blastocysts than in mouse blastocysts, which could contribute to an increased number of imprinted differentially methylated regions in the human genome. Global demethylation of the paternal genome was confirmed, but SINE-VNTR-Alu elements and some other tandem repeat-containing regions were found to be specifically protected from this global demethylation. Furthermore, centromeric satellite repeats were hypermethylated in human oocytes but not in mouse oocytes, which might be explained by differential expression of de novo DNA methyltransferases. These data highlight both conserved and species-specific regulation of DNA methylation during early mammalian development. Our work provides further information critical for understanding the epigenetic processes underlying differentiation and pluripotency during early human development.

Chromothripsis: potential origin in gametogenesis and preimplantation cell divisions. A review

To review the discovery of chromothripsis and analyze its impact on human reproduction. Database and literature analysis. University hospital. Carriers of massive and complex chromosomal rearrangements. Cytogenetic analysis and molecular testing (fluorescence in situ hybridization, microarray, whole-genome sequencing). Chromothripsis occurrence in human gametes and preimplantation embryos, with regard to the potential causative mechanisms described in literature. Databases were searched for the literature published up to March 2014. Chromothripsis is characterized by the shattering of one (or a few) chromosome segments followed by a haphazard reassembly of the fragments generated, arising through a single initial catastrophic event. Several mechanisms involving abortive apoptosis, telomere erosion, mitotic errors, micronuclei formation, and p53 inactivation might cause chromothripsis. The remarkable point is that all these plausible mechanisms have been identified in the field of human reproduction as causal factors for reproductive failures and the genesis of chromosomal abnormalities. Specific features of gametogenesis and early embryonic development such as the weakness of cell cycle and mitosis checkpoints and the rapid kinetics of division in germ cells and early cleavage embryos may contribute to the emergence of chromothripsis. The discovery of this new class of massive chromosomal rearrangement has deeply modified our understanding on the genesis of complex genomic rearrangements. Data presented in this review support the assumption that chromothripsis could operate in human germlines and during early embryonic development. Chromothripsis might arise more frequently than previously thought in both gametogenesis and early human embryogenesis.

DNA methylation dynamics of the human preimplantation embryo.

In mammals, cytosine methylation is predominantly restricted to CpG dinucleotides and stably distributed across the genome, with local, cell type-specific regulation directed by DNA binding factors1-3. This comparatively static landscape dramatically contrasts the events of fertilization, where the paternal genome is globally reprogrammed. Paternal genome demethylation includes the majority of CpGs, though methylation is maintained at several notable features4-7. While these dynamics have been extensively characterized in the mouse, only limited observations are available in other mammals, and direct measurements are required to understand the extent to which early embryonic landscapes are conserved8-10. We present genome-scale DNA methylation maps of human preimplantation development and embryonic stem cell (ESC) derivation, confirming a transient state of global hypomethylation that includes most CpGs, while sites of persistent maintenance are primarily restricted to gene bodies. While most features share similar dynamics to mouse, maternally contributed methylation is divergently targeted to species-specific sets of CpG island (CGI) promoters that extend beyond known Imprint Control Regions (ICRs). Retrotransposon regulation is also highly diverse and transitions from maternally to embryonically expressed, species-specific elements. Together, our data confirm that paternal genome demethylation is a general attribute of early mammalian development that is characterized by distinct modes of epigenetic regulation.

A single domain of the ZP2 zona pellucida protein mediates gamete recognition in mice and humans.

The extracellular zona pellucida surrounds ovulated eggs and mediates gamete recognition that is essential for mammalian fertilization. Zonae matrices contain three (mouse) or four (human) glycoproteins (ZP1-4), but which protein binds sperm remains controversial. A defining characteristic of an essential zona ligand is sterility after genetic ablation. We have established transgenic mice expressing human ZP4 that form zonae pellucidae in the absence of mouse or human ZP2. Neither mouse nor human sperm bound to these ovulated eggs, and these female mice were sterile after in vivo insemination or natural mating. The same phenotype was observed with truncated ZP2 that lacks a restricted domain within ZP2(51-149). Chimeric human/mouse ZP2 isoforms expressed in transgenic mice and recombinant peptide bead assays confirmed that this region accounts for the taxon specificity observed in human-mouse gamete recognition. These observations in transgenic mice document that the ZP2(51-149) sperm-binding domain is necessary for human and mouse gamete recognition and penetration through the zona pellucida.

REPRODUCTIVE TECHNOLOGY: A CRITICAL ANALYSIS OF THEOLOGICAL RESPONSES IN CHRISTIANITY AND ISLAM

AbstractReproductive medical technology has revolutionized the natural order of human procreation. Accordingly, some have celebrated its advent as a new and liberating determinant of kinship at the global level and advocate it as a right to reproductive health while others have frowned upon it as a vehicle for “guiltless exchange of sexual fluid” and commodification of human gametes. Religious voices from both Christianity and Islam range from unthinking adoption to restrictive use. While utilizing this technology to enable the married couple to have children through the use of their own sexual material is welcome, the use of third party, surrogacy, and reproductive cloning are not in keeping with the sacrosanct principles of kinship, procreation through licit sexual intercourse, and social cohesiveness for building a cohesive family as uphold by both Christianity and Islam. To examine such larger issues emanating from these new ways of human procreation, beyond the question of legality, is a point which legal scholars in both Christianity and Islam, when issuing religious decrees, have not anticipated sufficiently. The article proposes to be an attempt to that end through a qualitative critical content analysis of selected literature written on the subject.

Syncytin-1 and its receptor is present in human gametes

To determine whether the true fusogen Syncytin-1 and its receptor (ASCT-2) is present in human gametes using qRT-PCR, immunoblotting and immunofluorescence. Donated oocytes and spermatozoa, originating from a fertility center in tertiary referral university hospital, underwent qRT-PCR, immunoblotting and immunofluorescence analyzes. Quantitative RT-PCR of sperm samples from sperm donors showed that syncytin-1 is present in all samples, however, protein levels varied between donors. Syncytin-1 immunoreactivity predominates in the sperm head and around the equatorial segment. The receptor ASCT-2 is expressed in the acrosomal region and in the sperm tail. Moreover, ASCT-2, but not syncytin-1, is expressed in oocytes and the mRNA level increases with increasing maturity of the oocytes. Syncytin and its receptor are present in human gametes and localization and temporal appearance is consistent with a possible role in fusion between oocyte and sperm.

The making of an embryologist, then and now!

The making of an embryologist, then and now!

Devolved Regulation as a Two-Stage Rocket to Public Acceptance of Experiments with Human Gametes and Embryos

Kazancigil endorses governance to the extent that it has a greater capacity to cope with policy making on complex issues in our differentiated societies. At the same time, he is skeptical of how governance excludes ‘politics’ from the process of policy-making. Policy fields that are highly dependent on scientific knowledge are considered by him to be especially vulnerable for ‘policy making without politics’. In this article, the case of UK policy making concerning the creation of human animal hybrid embryos will be analyzed to provide insights into the problems that can be connected to governance as form of managing public decision making. In this case, it is not so much the exclusion of ‘politics’ in the sense of ‘the representative democratic institutions and processes’ that appears to be the problem of governance but rather the downplaying of differences in societal views concerning the issue and the lack of real reconciliation of such views.

Multiplex parenting: IVG and the generations to come

Recent breakthroughs in stem cell differentiation and reprogramming suggest that functional human gametes could soon be created in vitro. While the ethical debate on the uses of in vitro generated...

Cryopreservation in ART and concerns with contamination during cryobanking.

The cryopreservation of gametes and embryos is vital to numerous fields of reproductive biology, including assisted human reproduction. With improved culture conditions, there are an increasing number of embryos to cryopreserve for potential use in subsequent cycles. Many of the gametes and embryos in human IVF are cryopreserved in open systems. Because liquid nitrogen is not sterile, concerns have been raised with regard to contamination from the liquid nitrogen and also cross-contamination between patients' germplasm. Human gamete and embryo cryopreservation are discussed, with recommendations on how to minimize and eliminate contamination, emphasizing the benefits of closed vitrification devices.

Human sperm anatomy and endocrinology in varicocele: role of androgen receptor

The study of androgens involved in male reproduction has been object of intense efforts, while their reported action on human male gametes is limited. We previously described the presence of androgen receptor (AR) in sperm with a role related to the modulation of the PI3K pathway. In the present study, we investigated the expression of AR and its ultrastructural location in normal sperm as well as in spermatozoa obtained from varicocele patients. We observed a reduced AR content in varicocele sperm with respect to healthy sperm by western blot analysis and transmission electron microscopy (TEM). The ultrastructural location of AR was detected mainly on the head membrane as well as in the nucleus, neck, and mitochondria. Influence of dihydrotestosterone (DHT) treatment on cholesterol efflux was increased in normal sperm, while it was reduced or absent in varicocele sperm. To better understand DHT/AR significance in human male gametes, we evaluated triglyceride content and lipase, acyl-CoA dehydrogenase, and glucose-6-phosphate dehydrogenase activities upon DHT treatment. The metabolic outcome glimpsed in normal sperm was an increased metabolic rate, while 'varicocele' sperm economized energy. Taken together, our results reveal DHT and AR as new players in sperm endocrinology, indicating that varicocele sperm may have difficulty in switching to the capacitated status. A decreased AR expression and a consequent reduced responsiveness to DHT in sperm may represent molecular mechanisms involved in the pathophysiology of varicocele leading to male infertility. This study revealed new detrimental effects of varicocele on sperm at the molecular level.

La science des cellules souches embryonnaires humaines en Iran : une expérience pionnière dans le monde musulman

La recherche sur les cellules souches embryonnaires humaines (CSEh) est un domaine qui a suscite un vif interet dans les milieux scientifiques mais aussi financiers. C’est aussi un champ d’investigation source de dilemmes ethiques et de developpements politiques encadrant le statut moral de l’embryon humain, les sources d’embryons ou de gametes humains destines a la recherche, le clonage ainsi que l’utilisation therapeutique des cellules souches. Dans le monde musulman, l’Iran, une nation pionniere de la recherche sur les SCEh, a reporte l’etablissement d’une nouvelle lignee de cellules souches des 2003. Ce pays a aussi etabli des recommandations ethiques nationales pour la recherche et la therapie utilisant les cellules souches. Le present manuscrit decrit le developpement de la science entourant les CSEh ainsi que d’autres accomplissements scientifiques et bioethiques connexes en Iran. Il explique aussi comment la recherche sur les CSEh est a la fois guidee et reglementee par les lois et principes ethiques issus de l’Islam, et montre comment l’experience d’un pays en developpement peut servir d’exemple a d’autres societes similaires. Cet article presente ensuite une breve revue de l’etat actuel de la recherche et de la reglementation de ce domaine dans certains pays musulmans du Moyen-Orient. En conclusion, on peut argumenter autour du fait que, bien que la science et la religion soient des facteurs cles dans les debats actuels autours des CSEh, d’autres facteurs influencent la maniere avec laquelle un nouveau savoir est aborde dans des pays ayant par ailleurs la meme obedience religieuse ou des interets scientifiques similaires.

Informed consent and the use of gametes and embryos for research: a committee opinion

The ethical conduct of human gamete and embryo research depends upon conscientious application of principles of informed consent developed in the context of clinical research. This document explores these principles, which entail, for example, that investigations occur under Institutional Review Board oversight. This document also discusses the complexities in obtaining informed consent from the persons whose gametes or embryos are being used in research but were originally intended for reproductive purposes. This statement replaces the document of the same name last published in 2004 (Fertil Steril 2004;82:S251-252).

Commodifying Human Life: The Numerus Clausus Principle and Unconventional Property Rights

Throughout the common law world the notion that classes of property rights are closed in number is a prevailing concept across property regimes. This closed in number, or numerus clausus, principle has served property rights well. This principle has prevented messy property arrangements from arising – such as an agreement between two people where one owns a watch on Tuesdays and Thursdays, and the other owns it the rest of the week. However, as technology evolves, property is created in items that the legislature never contemplated. In this article we explore the seminal Canadian case of JCM v ANA and examine how numerus clausus and property no longer remain sufficient tools for delineating individual’s rights to tangible goods. Whether the sperm straws in question in JCM are property or not, and whether numerus clausus recognizes a category of property rights where human tissues or fluids capable of providing life or not, are contentious issues, not easily resolved. The argument is made that the numerus clausus principle is of marginal use considering such forms of unconventional property as human gametes. This is supported through a review of JCM, followed by an exploration of the optimal standardization. The second part of this work seeks to demonstrate the incompatibility of the numerus clausus principle, and the optimal standardization theory, with a critical analysis of JCM that underscores three central but overwhelming critical problems with such an application.

Non-meiotic chromosome instability in human immature oocytes

Aneuploidy has been a major issue in human gametes and is closely related to fertility problems, as it is known to be present in cleavage stage embryos and gestational losses. Pre-meiotic chromosome abnormalities in women have been previously described. The aim of this study is to assess the whole-chromosome complement in immature oocytes to find those abnormalities caused by mitotic instability. For this purpose, a total of 157 oocytes at the germinal vesicle or metaphase I stage, and discarded from IVF cycles, were analysed by CGH. Fifty-six women, between 18 and 45 years old (mean 32.5 years), including 32 IVF patients (25-45 years of age) and 24 IVF oocyte donors (18-33 years of age), were included in the study. A total of 25/157 (15.9%) of the oocytes analysed, obtained from three IVF clinics, contained chromosome abnormalities, including both aneuploidy (24/157) and structural aberrations (9/157). Independently of the maternal age, the incidence of abnormal oocytes which originated before meiosis is 15.9%, and these imbalances were found in 33.9% of the females studied. This work sheds light on the relevance of mitotic instability responsible for the generation of the abnormalities present in human oocytes.

In vitro eugenics

A series of recent scientific results suggest that, in the not-too-distant future, it will be possible to create viable human gametes from human stem cells. This paper discusses the potential...

Position Statement on the Provision and Procurement of Human Eggs for Stem Cell Research

The nature of compensation for women who donate eggs (oocytes) for research remains a contentious issue internationally. This position paper lays out the arguments for, and discusses the arrangements in which, a modest payment might be ethically justifiable.