Human Gametes Research Articles

'Gift without a price tag': altruism in anonymous semen donation

Commercialization of human gametes is now legally prohibited in Canada under the Assisted Human Reproduction Act 2004, making semen donation in Canada altruistic and anonymous by law. Donors must be altruistically motivated to donate gametes without receiving monetary rewards. Globally speaking, Canada is neither the first nor the only country in the world that has legislation to support altruistic gamete donation. Other countries have advocated similar systems either through legislative changes or implementation of best practice models. This paper is a review of literature assessing the differences in donation behaviours under paid and altruistic donation models. It provides contextual information of the current semen donation situation in Canada, while drawing upon relevant literature and research data from other countries as references. The author also attempts to re-conceptualize the meanings of altruism through exploring the complex interplay between psycho-social and institutional factors in influencing donors' behaviours. Although there is a substantial amount of research studying the impacts on donor recruitment when payment is withdrawn, very few research studies are found that focus on exploring altruistic donor recruitment strategies. It is unrealistic to expect the altruistic donation culture to emerge spontaneously in Canada without any multi-level efforts to coordinate the recruitment strategies. Research programmes are greatly needed to generate empirical knowledge that can guide the development of altruistic donor recruitment models geared to the current socio-cultural environment and legislative framework in Canada. The findings will be invaluable when the legislation comes up for parliamentary review in the near future.

Stringent regulation of oocyte donation in China

Currently in China, health regulations permit oocyte donation only from IVF/ICSI patients who have 20 or more mature oocytes retrieved from a single cycle, of which at least 15 must be kept for their own treatment. Oocyte donation from non-patients and commercial transaction of human gametes are strictly prohibited by law. Additionally, embryos derived from donated oocytes must be cryopreserved and cannot be transferred to prospective recipients, until donors have been screened to be free of communicable diseases after 6 months. Such overly stringent regulation has in turn led to a severe shortage of available donor oocytes in China. The situation is made worse by a cultural aversion to oocyte donation by the majority of patients, because biological kinship and blood relations are viewed as sacrosanct in traditional Chinese culture. The harsh social stigmatization of childlessness in Chinese society, increasing incidence of age-related female infertility in recent years and growing numbers of bereaved older women who have lost their only child to accidents, natural disasters and suicides would make it imperative to reconsider liberalizing the regulation of oocyte donation in China. In particular, the blanket ban on oocyte donation by non-patients should be lifted, as it is anticipated that there are many young healthy women in China who are generous and open-minded enough to consider altruistically donating their oocytes to childless couples.

Segregation analysis of paracentric inversions in human sperm: inverted segment size, low copy repeats (LCRs) and recombination hot spots have a story to tell

OBJECTIVE: Paracentric inversions (PAIs) are structural chromosomal rearrangements generally considered to be harmless. The objective of this study was to find out the correlation between the presence of LCRs, recombination hot spots around the breakpoints, inverted segment size and the formation of recombinants in human gametes.

In vitro culture under physiologic oxygen concentration improves blastocyst yield and quality: a prospective randomized survey on sibling oocytes

A prospective randomized study was carried on sibling oocytes in which human gametes and embryos were cultured at physiologic (6% CO(2) + 5% O(2) + 89% N(2)) condition from insemination to day 6 or at atmospheric (6% CO(2) in air) condition until day 3 and at physiologic environment afterward. The results showed that physiologic oxygen concentration throughout culture period improved total blastocyst yield and day 5 embryo quality.

Expression of epithelial cadherin in the human male reproductive tract and gametes and evidence of its participation in fertilization

Epithelial cadherin (E-cadherin) has been involved in several calcium-dependent cell-cell adhesion events; however, its participation in gamete interaction has not been fully investigated. Our results have demonstrated expression of E-cadherin mRNA in the human male reproductive tract showing higher levels in the caput, corpus and cauda epididymis than in the testis. The mature 122 kDa E-cadherin was detected in epididymal protein extracts and was localized in the epithelial cells from the three epididymal regions. Moreover, the 86 kDa E-cadherin ectodomain was found in cauda epididymal and seminal plasma. Western immunoblotting of human sperm protein extracts allowed the identification of four E-cadherin forms (122, 105, 97 and 86 kDa). The protein was localized in the acrosomal region of intact spermatozoa, remained associated with the head of acrosome-reacted cells and was also detected on the oocyte surface. A similar localization was determined for other proteins of the adhesion complex (beta-catenin and actin). Spermatozoa incubated with anti-E-cadherin antibodies showed impaired binding to homologous zona pellucida (ZP); in addition, presence of these antibodies inhibited the penetration of human spermatozoa to ZP-free hamster oocytes. The results presented here describe the expression of E-cadherin in the male reproductive tract and gametes and strongly suggest its involvement in adhesion events during human fertilization. The identification of proteins involved in gamete interaction will contribute to the understanding of the molecular basis of fertilization and help in the diagnosis and treatment of infertility.

Comprehensive molecular cytogenetic analysis of the human blastocyst stage

The high frequency of chromosomal abnormalities observed in human gametes and embryos is unlike that seen in other mammalian species and is of great clinical significance, leading to high rates of pregnancy loss, and live-born children with aneuploid syndromes. Although much is known concerning the aneuploidy rates of oocytes, cleavage stage embryos and fetuses during pregnancy, the chromosomal status of blastocysts has been relatively little investigated. A total of 158 good quality blastocysts were examined using micromanipulation, whole genome amplification and comparative genomic hybridization. From the obtained data, it was evident that the aneuploidy rate (38.8%) is significantly lower for blastocysts than for embryos at earlier stages (51%). However, in many cases, chromosome errors, including monosomy, imbalance affecting the larger chromosomes and complex aneuploidy persisted to this final stage of preimplantation development. This study represents the first attempt to gain a detailed insight into the extent and type of chromosome errors seen at the blastocyst stage, using a comprehensive molecular cytogenetic method. Our data suggest that the blastocyst stage does not represent an absolute selective barrier, and that the majority of aneuploid embryos are lost at the time of implantation or shortly thereafter.

Expression Analysis of the NLRP Gene Family Suggests a Role in Human Preimplantation Development

BackgroundThe NLRP (Nucleotide-binding oligomerization domain, Leucine rich Repeat and Pyrin domain containing) family, also referred to as NALP family, is well known for its roles in apoptosis and inflammation. Several NLRPs have been indicated as being involved in reproduction as well.MethodologyWe studied, using the unique human gametes and embryo materials, the expression of the NLRP family in human gametes and preimplantation embryos at different developmental stages, and compared the expression levels between normal and abnormal embryos using real-time PCR.Principal FindingsAmong 14 members of the NLRP family, twelve were detected in human oocytes and preimplantation embryos, whereas seven were detected in spermatozoa. Eight NLRPs (NLRP4, 5, 8, 9, 11, 12, 13, and 14) showed a similar expression pattern: their expression levels were high in oocytes and then decreased progressively in embryos, resulting in a very low level in day 5 embryos. However, NLRP2 and NLRP7 showed a different expression pattern: their expression decreased from oocytes to the lowest level by day 3, but increased again by day 5. The expression levels of NLRP5, 9, and 12 were lower in day 1 abnormal embryos but higher in day3 and day5 arrested embryos, when compared with normal embryos at the same stages. NLRP7 was down-regulated in day 1 and day 5 abnormal embryos but over-expressed in day3 arrested embryos.ConclusionsAccording to our results, different NLRPs possibly work in a stage-dependent manner during human preimplantation development.

Egg sharing: a practical and ethical option in IVF?

Egg sharing is a procedure in which a woman who is herself undergoing assisted-conception treatment receives subsidized treatment in exchange for sharing her eggs with another woman. It has become increasingly prevalent in the UK and is the major source of donor eggs in the UK; however, its practice is controversial. Available evidence concerning the outcomes of egg sharing is limited. To date, while this has failed to provide strong empirical support for concerns that have been raised regarding egg sharing, continuing significant gaps in information regarding clinical and psycho–social outcomes remain, which mean that an informed judgment on empirical grounds cannot yet be made. Ongoing key ethical controversies focus on the impact of egg sharing on the commodification of human gametes and whether women can genuinely consent to donating their eggs under an egg-sharing scheme.

Embryo cryopreservation: is vitrification ready to replace slow freezing?

Cryopreservation of human gametes, embryos and blastocysts has become an integral part of assisted reproduction. This approach may have several advantages for infertile patients. It provides an opportunity to limit the numbers of embryos transferred while supernumerary embryos will be used in subsequent treatment cycles, thereby increasing the cumulative pregnancy rate. Furthermore, the potential risk of hyperstimulation syndrome can be reduced. In addition, storage of embryos from a cycle allows the patient to space the timing of sibling pregnancies and improve their potential of achieving a pregnancy at an advanced maternal age. Therefore, a reliable procedure for the cryopreservation of supernumerary embryos is needed. Since the early 1980s, two common techniques have been used in cryopreservation: the conventional slow cooling method and the more recent rapid procedure, known as vitrification. The latter needs a much higher concentration of cryoprotectants and faster cooling rates. Vitrification is qu...

Meiotic errors in human oogenesis and spermatogenesis

Chromosome anomalies are extraordinarily common in human gametes, with approximately 21% of oocytes and 9% of spermatozoa abnormal. The types of abnormalities are quite different since most abnormal oocytes are aneuploid, whereas the majority of abnormalities in spermatozoa are structural. Chromosomes 21 and 22 (the smallest chromosomes) are over-represented in aneuploid gametes in both oocytes and sperm. Chromosome 16 is also frequently observed in aneuploid oocytes, whereas the sex chromosomes are particularly predisposed to non-disjunction in human sperm. Maternal age is clearly the most significant factor in the aetiology of aneuploidy; theories about the cause of the maternal age effect are discussed. Paternal age does not have a dramatic effect on the frequency of aneuploid sperm; there is some evidence for a modest increase in the frequency of sex chromosomal aneuploidy. Meiotic recombination has a significant effect on the genesis of aneuploidy in both females and males. New techniques, which allow the analysis of recombination along the synaptonemal complex, have yielded interesting new information in healthy and infertile individuals. There is a link between infertility and the genesis of chromosome abnormalities. Future studies will unravel more of the underlying causal factors.

Chromosomal mosaicism goes global

Intercellular differences of chromosomal content in the same individual are defined as chromosomal mosaicism (alias intercellular or somatic genomic variations or, in a number of publications, mosaic aneuploidy). It has long been suggested that this phenomenon poorly contributes both to intercellular (interindividual) diversity and to human disease. However, our views have recently become to change due to a series of communications demonstrated a higher incidence of chromosomal mosaicism in diseased individuals (major psychiatric disorders and autoimmune diseases) as well as depicted chromosomal mosaicism contribution to genetic diversity, the central nervous system development, and aging. The later has been produced by significant achievements in the field of molecular cytogenetics. Recently, Molecular Cytogenetics has published an article by Maj Hulten and colleagues that has provided evidences for chromosomal mosaicism to underlie formation of germline aneuploidy in human female gametes using trisomy 21 (Down syndrome) as a model. Since meiotic aneuploidy is suggested to be the leading genetic cause of human prenatal mortality and postnatal morbidity, these data together with previous findings define chromosomal mosaicism not as a casual finding during cytogenetic analyses but as a more significant biological phenomenon than previously recognized. Finally, the significance of chromosomal mosaicism can be drawn from the fact, that this phenomenon is involved in genetic diversity, normal and abnormal prenatal development, human diseases, aging, and meiotic aneuploidy, the intrinsic cause of which remains, as yet, unknown.

Aromatase and estrogens in man reproduction: a review and latest advances

The mammalian testis is a complex organ which produces spermatozoa and synthesizes steroids. The transformation of androgens into estrogens is catalyzed by aromatase, an enzymatic complex encoded by a single copy-gene (cyp19) which contains 18 exons, 9 of them being translated. In man besides Leydig cells, we have demonstrated the existence of a biologically active aromatase in immature germ cells and in ejaculated spermatozoa. In addition the presence of estrogen receptors (ERalpha and ERss) in immature germ cells and in spermatozoa has been reported. Concerning aromatase, a 30% decrease of the amount of mRNA is observed in immotile compared to motile sperm fraction from the same sample. In asthenoteratozoospermic, teratozoospermic and asthenozoospermic patients, the aromatase gene expression is decreased respectively by 67%, 52% and 44%, when compared to normospermic controls. Statistical analyses between the sperm morphology and the aromatase/GAPDH ratio have revealed a high degree of correlation (r=-0.64) between that ratio and the percentage of abnormal spermatozoa (especially microcephaly). In men genetically deficient in aromatase diminutions of sperm number and motility have been published. Therefore besides gonadotrophins and testosterone, estrogens are likely playing a relevant role in spermiogenesis and human male gamete maturation.

Expression analysis of TFIID in single human oocytes: new potential molecular markers of oocyte quality

Molecular characterization of human female gametes should make it easier to understand the basis of certain infertility disorders. Biologically significant mRNAs have been analysed in single oocytes to search for molecular biomarkers of oocyte quality. Initial analysis was focused on mRNA for proteins involved in cell growth and cycle control, specifically those encoding members of the general transcription apparatus such as the subunits of the general transcription factor TFIID. This heteromultimeric protein, comprising about 15 subunits, is the most important general transcription factor of the second class. These proteins are essential for the initiation of transcription of protein-coding genes, so they must be present in mature oocytes for mRNA synthesis during the first phases of embryonic development. Semi-quantitative reverse transcription-polymerase chain reaction was used to identify different TFIID subunits in single oocytes and to search for differences in expression as compared with control tissues. The data show that the mRNAs for most TFIID subunits are indeed synthesized in oocytes, but their expression profiles differ markedly. TATA box-binding protein associated factor 4B (TAF4B), TAF5 and TATA box-binding protein-like 2 (TBPL2) are expressed at higher levels in oocytes than in control tissues. It is suggested that they could be used as biomarkers of oocyte quality.

Can proteomics help to shape the future of human assisted conception?

Proteomics describes the changes in all proteins expressed and translated from a single genome. At present little is known regarding either the genome or proteome of human gametes or the preimplantation embryo. The unravelling of this information is fundamental to understanding the complexity of reproductive physiology, including the dialogue between the developing embryo and its maternal environment. To date, a lack of sensitivity has been the main reason behind the inability to introduce proteomics technology into assisted reproduction techniques. Proteomics alone involves several sophisticated techniques including imaging, mass spectrometry and bioinformatics to identify, quantify and characterize a proteome. The recent increased sensitivity of these techniques has allowed for the development of new protocols that are capable of not only profiling the proteome of individual human oocytes and embryos, but also the proteins produced by the embryo into the surrounding medium (the secretome). Hence, the identification of proteins that are involved in oocyte maturation, embryo development and implantation could lead to further improvements in assisted reproduction techniques as well as the development of new diagnostic tests. Furthermore, proteomics may contribute in the design of a non-invasive viability assay to assist in the selection of embryos for transfer in human assisted reproduction.

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.

Fusion in three easy steps

Mating is complicated for yeast. The nuclei of two cells have to get together, even though both nuclear membranes remain intact. Melloy et al. now nail down how many steps it takes for the cells to combine their nuclei. Figure 1 Electron tomography of two mating yeast nuclei reveals multiple steps to fusion. Before human gametes fuse, their nuclear membranes break down to allow the nuclear contents to mix. But when yeast mate, the inner and outer membranes of the two nuclei have to join, as do the spindle pole bodies (SPBs). Spanning the inner and outer membranes, SPBs anchor the microtubules that winch the nuclei together. Whether the components merge simultaneously or in three separate steps has been debated, due to the difficulty of catching nuclei in the act. Melloy et al. used electron tomography to capture 3D images of nuclei at different stages of fusion. They found that nuclei retained separate SPBs even after the inner and outer membranes had joined, indicating that the SPBs are the last to fuse. To determine which membranes linked up first, the team turned to light microscopy. They filled the nucleus with one marker and the lumen between the inner and outer membranes with another. The lumen marker started moving from one partner to the other about 30 seconds before the nuclear marker, indicating that the outer membranes merge first. Researchers suspect that outer membranes are drawn together by SNARE proteins. The mystery now is which proteins join the inner membranes. Reference: Melloy, P., et al. 2007. J. Cell Biol. 179:659–670. [PubMed]

Embriones híbridos como fuente de células troncales embrionarias

The HFEA (Human Fertilisations & Embryology Authority) recently accepted to perform research in hybrid embryos generated by transferring human somatic cell nucleus to cow enucleated oocytes, named cytoplasmatic hybrids. The aim is to obtain a source of embryonic stem cells without the use of human oocytes. The arguments for the approval are to avoid the risk of obtaining human oocytes and that these embryos will not be transferred to a female's womb for its development. Those who oppose the technique argue that it is a manipulation of the beginning of life and a disrespect to the dignity of human life because of the destruction of embryos. Nevertheless, the real nature of this new entity has not been established. Biologically it is an embryo with 99% of human genome and animal's cytoplasm, not generated from human gametes, it is not a new genome and it will be used only to cultivate stem cells. It does not seem possible to define its nature beyond any doubts. If it were considered as a human embryo it should be respected and protected as every human being. Once more, scientific progress opens new ethical and legal questions that we cannot answer in a definitive way. Researchers are exploring new roads to obtain pluripotential stem cells which should favor the development of innovative therapies. The main objection is the unavoidable destruction of human embryos, although in this case its origin and nature are not clear.

Hybrid embryos as a source of embryonic stem cells

The HFEA (Human Fertilisations & Embryology Authority) recently accepted to perform research in hybrid embryos generated by transferring human somatic cell nucleus to cow enucleated oocytes, named cytoplasmatic hybrids. The aim is to obtain a source of embryonic stem cells without the use of human oocytes. The arguments for the approval are to avoid the risk of obtaining human oocytes and that these embryos will not be transferred to a female's womb for its development. Those who oppose the technique argue that it is a manipulation of the beginning of life and a disrespect to the dignity of human life because of the destruction of embryos. Nevertheless, the real nature of this new entity has not been established. Biologically it is an embryo with 99% of human genome and animal's cytoplasm, not generated from human gametes, it is not a new genome and it will be used only to cultivate stem cells. It does not seem possible to define its nature beyond any doubts. If it were considered as a human embryo it should be respected and protected as every human being. Once more, scientific progress opens new ethical and legal questions that we cannot answer in a definitive way. Researchers are exploring new roads to obtain pluripotential stem cells which should favor the development of innovative therapies. The main objection is the unavoidable destruction of human embryos, although in this case its origin and nature are not clear.

Relationship between chromatin organization, mRNAs profile and human male gamete quality

Spermiogenesis is a complex process leading to the formation of motile spermatozoa characterized by a highly stable chromatin compaction that transfers the paternal genome into the oocyte. It is commonly held that these haploid cells are devoid of transcriptional and translational activities and that the transcripts represent remnants of stored mRNAs. Recently, the chromatin organization of mature spermatozoa has been revisited as a double nucleoprotamine-nucleohistone structure possessing less-condensed regions sensitive to nuclease activity, which could be implicated in the expression of genes involved in the early embryo development. The existence of a complex population of mRNAs in human sperm is well-documented, but their role is not yet elucidated. Evidence for a latent transcriptional capacity and/or a potential de novo translation in mature spermatozoa from fertile men are essential for understanding the last steps of sperm maturation, such as capacitation and acrosome reaction. As such, we have documented the relationship between sperm quality and the distribution of sperm RNAs by showing divergent levels of transcripts encoding for proteins involved in either nuclear condensation (protamines 1 and 2) or in capacitation (eNOS and nNOS, c-myc) or in motility and sperm survival (aromatase) between low and high motile sperm issued from the same sample. Therefore, analyzing the profile of mRNAs could be helpful either as a diagnostic tool for evaluating male fertility after spermatogenesis or for prognosis use for fertilization.

Law, globalisation and the NHS

The regulation of medical work in the UK has been shaped by the post-war settlement, which lead to the creation of the National Health Service in 1948. The removal of clinical care from the market was supported over the following decades by prohibitions of the sale of human organs and gametes. That settlement is now being dismantled, with the increasing privatisation of NHS facilities. The recommodification of medicine in Britain is achieved as part of broader patterns of neoliberal globalisation. Cross-border markets in health services are realized in law through international (e.g. the General Agreement on Trade in Services) and regional trade law (e.g. European Community law).