Potential consequences of clinical application of artificial gametes: a systematic review of stakeholder views

Micro/Nanorobotics in In Vitro Fertilization: A Paradigm Shift in Assisted Reproductive Technologies

In vitro fertilization (IVF) has transformed the sector of assisted reproductive technology (ART) by presenting hope to couples facing infertility challenges. However, conventional IVF strategies include their own set of problems such as success rates, invasive procedures, and ethical issues. The integration of micro/nanorobotics into IVF provides a prospect to address these challenging issues. This article provides an outline of the use of micro/nanorobotics in IVF specializing in advancing sperm manipulation, egg retrieval, embryo culture, and capacity future improvements in this swiftly evolving discipline. The article additionally explores the challenges and obstacles associated with the integration of micro/nanorobotics into IVF, in addition to the ethical concerns and regulatory elements related to the usage of advanced technologies in ART. A comprehensive discussion of the risk and safety considerations related to using micro/nanorobotics in IVF techniques is likewise presented. Through this exploration, we delve into the core principles, benefits, challenges, and potential impact of micro/nanorobotics in revolutionizing IVF procedures and enhancing affected person outcomes.

In vitro spermatogenesis: Why meiotic checkpoints matter

Successful in vitro spermatogenesis would generate functional haploid spermatids, and thus, form the basis for novel approaches to treat patients with impaired spermatogenesis or develop alternative strategies for male fertility preservation. Several culture strategies, including cell cultures using various stem cells and ex vivo cultures of testicular tissue, have been investigated to recapitulate spermatogenesis in vitro. Although some studies have described complete meiosis and subsequent generation of functional spermatids, key meiotic events, such as chromosome synapsis and homologous recombination required for successful meiosis and faithful in vitro-derived gametes, are often not reported. To guarantee the generation of in vitro-formed spermatids without persistent DNA double-strand breaks (DSBs) and chromosomal aberrations, criteria to evaluate whether all meiotic events are completely executed in vitro need to be established. In vivo, these meiotic events are strictly monitored by meiotic checkpoints that eliminate aberrant spermatocytes. To establish criteria to evaluate in vitro meiosis, we review the meiotic events and checkpoints that have been investigated by previous in vitro spermatogenesis studies. We found that, although major meiotic events such as initiation of DSBs and recombination, complete chromosome synapsis, and XY-body formation can be achieved in vitro, crossover formation, chiasmata frequency, and checkpoint mechanisms have been mostly ignored. In addition, complete spermiogenesis, during which round spermatids differentiate into elongated spermatids, has not been achieved in vitro by various cell culture strategies. Finally, we discuss the implications of meiotic checkpoints for in vitro spermatogenesis protocols and future clinical use.

Enthusiasm, concern and ambivalence in the Belgian public's attitude towards in-vitro gametogenesis

Given the controversial nature of research into in-vitro gametogenesis (IVG), this study set out to investigate the current attitudes towards IVG in the general Belgian population in order to anticipate potential future barriers and misunderstandings. A questionnaire was developed and incorporated into a web-based online survey and sent out to Belgians aged ≥ 18 years in September 2018 until a representative sample (by age, gender and region) of 1000 participants was reached. Respondents expressed an overall positive attitude towards IVG and its possible future applications, with the exception of the use of IVG in postmenopausal women. They were ambivalent about the importance of genetic parenthood and about the necessary experiments on animals and embryos to bring IVG to the clinic. While the willingness to accept greater risks for IVG than for other assisted reproductive technology treatments was low (17.5%), the use of spare in-vitro fertilization embryos to study those risks was acceptable for 55.8% of participants; embryo creation was acceptable for 38.1%; and experiments on mice and monkeys were acceptable for 45.3% and 30.4%, respectively. Finally, 85.6% of participants agreed that the Belgian Government should strictly regulate IVG. In conclusion, preclinical research into IVG and other reproductive technologies elicits a great diversity of attitudes towards the importance of genetic parenthood and the acceptability of embryo and animal research. There is a need for public dialogue on these topics.

In Vitro Meiosis of Male Germline Stem Cells

In vitro spermatogenesis has been achieved by culturing mouse embryonic stem cells (ESCs) together with a cell suspension of male juvenile gonad. However, for human fertility treatment or preservation, patient-specific ESCs or juvenile gonad is not available. We therefore aim to achieve in vitro spermatogenesis using male germline stem cells (GSCs) without the use of juvenile gonad. GSCs, when cultured on immortalized Sertoli cells, were able to enter meiosis, reach the meiotic metaphase stages, and sporadically form spermatid-like cells. However, the in vitro-formed pachytene-like spermatocytes did not display full chromosome synapsis and did not form meiotic crossovers. Despite this, the meiotic checkpoints that usually eliminate such cells to prevent genomic instabilities from being transmitted to the offspring were not activated, allowing the cells to proceed to the meiotic metaphase stages. In vitro-generated spermatid-like cells should thus be thoroughly investigated before being considered for clinical use.

Novel Approaches in Addressing Ovarian Insufficiency in 2019: Are We There Yet?

Ovarian insufficiency is described as a multifaceted issue typically encountered in the field of assisted reproduction. The three main identified diagnoses of ovarian insufficiency include premature ovarian failure (POF), poor ovarian response (POR), and advanced maternal age (AMA). Patient heterogeneity in the era of individualized medicine drives research forward leading to the emergence of novel approaches. This plethora of innovative treatments in the service of adequately managing ovarian insufficiency is called to undertake the challenge of addressing infertile patients exploring their reproductive options. This review provides an all-inclusive presentation and critical analysis on novel treatments that have not achieved routine clinical practice status yet, but have recently emerged as promising. In light of the lack of randomized controlled trials conveying safety and efficiency, clinicians are left puzzled in addressing the "how" and "for whom" these approaches may be beneficial. From ovarian injection employing platelet-rich plasma (PRP) or stem cells to artificial gametes and ovaries, ovarian transplantation, and mitochondrial replacement therapy, this descriptive review provides insight toward assisting the practitioner in decision making regarding these cutting-edge treatments. Biological mechanisms, invasiveness levels, efficiency, as well as possible complications, the current status along with bioethical concerns are discussed in the context of identifying future optimal treatment.

The Impact of Third Party Reproduction on Family and Kinship

The development of in vitro fertilization (IVF) in the UK, in 1978, proved a major breakthrough in the process of human reproduction, which had remained constant in human history. The impact of IVF and the ensuing assisted reproductive technologies (ARTs) has not been limited in revolutionizing the "natural" practice of biological reproduction, but has reached out to and affected almost every institution in society. Family and kinship, as the social expression of reproduction and the institutions which are the most transparently structured realm of human life are those most profoundly affected by ARTs. Although literature on the implications of ARTs is in general abundant, this article presents new insights on their impact on family and kinship in Iran, which remains a unique case in the Muslim world. It explores the particular way ARTs, especially third-party donation, have been endorsed and practiced in Iran, and their consequences for the family, the infertile individuals, and their position vis-à-vis their kin and social group. The conclusion points to the lack of clarity concerning the initial rulings by the Islamic jurists, who allowed the practice of ARTs, and which has led to a number of unintended consequences regarding the legal, religious, cultural, and ethical issues, affecting the family, its structure and the relationship between the kin group. These consequences range, inter alia, from the question of the anonymity of third-party donor, to the permissibility of gamete donation between blood relatives, and to the absence of enforceable legislation.

Human Rights and Assisted Reproductive Technologies (ART): A Contractarian Approach

What are human rights? Do they exist? I propose to answer these questions by advancing a contractarian account of human rights. I focus on the human right to found a family and have children. I also show how the contractarian approach to human rights can explain the current relevance of reproductive rights in the human rights discourse, and how the emergence of ART (Assisted Reproductive Technologies) has contributed to this shift. The contractarian account of human rights asks, firstly, the following question: which basic needs and desires can be ascribed to any human being regardless of gender, nationality, sexual orientation, age, ethnicity etc.? Having an interest, for instance, in preserving one’s own bodily integrity, freedom, and private property qualifies as a basic human need or basic desire. But a basic human need or desire does not constitute in itself a human right. Secondly, the contractarian account of human rights asks, then, which basic human needs or basic desires individuals and states representatives would consider so important that they would agree to create institutional frameworks, both at the domestic and international level, in such a way as to enable individuals to pursue the fulfilment of their basic needs or desires without state interference. Human rights exist and can only be claimed in the context of these normative frameworks.

The Ethics of Genetic Cognitive Enhancement: Gene Editing or Embryo Selection?

Recent research with human embryos, in different parts of the world, has sparked a new debate on the ethics of genetic human enhancement. This debate, however, has mainly focused on gene-editing technologies, especially CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats). Less attention has been given to the prospect of pursuing genetic human enhancement by means of IVF (In Vitro Fertilisation) in conjunction with in vitro gametogenesis, genome-wide association studies, and embryo selection. This article examines the different ethical implications of the quest for cognitive enhancement by means of gene-editing on the one hand, and embryo selection on the other. The article focuses on the ethics of cognitive enhancement by means of embryo selection, as this technology is more likely to become commercially available before cognitive enhancement by means of gene-editing. This article argues that the philosophical debate on the ethics of enhancement should take into consideration public attitudes to research on human genomics and human enhancement technologies. The article discusses, then, some of the recent findings of the SIENNA Project, which in 2019 conducted a survey on public attitudes to human genomics and human enhancement technologies in 11 countries (France, Germany, Greece, the Netherlands, Poland, Spain, Sweden, Brazil, South Africa, South Korea, and United States).

Mouse in vitro spermatogenesis on alginate-based 3D bioprinted scaffolds

In vitro spermatogenesis (IVS) has already been successfully achieved in rodents by organotypic and soft matrix culture systems. However, the former does not allow single cell input, and the latter presents as a simple thick layer in which all cells are embedded. We explored a new culture system using a mouse model by employing an alginate-based hydrogel and 3D bioprinting, to control scaffold design and cell deposition. We produced testicular constructs consisting of printed cell-free scaffolds (CFS) with prepubertal testicular cells (TC) in their easy-to-access macropores. Here, the pores represented the only cell compartment (TC/CFS). Double-cell compartment testicular constructs were achieved by culturing magnetic-activated cell sorting-enriched epithelial cells in the pores of interstitial cell-laden scaffolds (CD49f⁺/CLS). Cell spheres formed in the pores in the weeks following cell seeding on both CFS and CLS. Although restoration of the tubular architecture was not observed, patches of post-meiotic cells including elongated spermatids were found in 66% of TC/CFS. Differentiation up to the level of round spermatids and elongated spermatids was observed in all and 33% of CD49f⁺/CLS constructs, respectively. Organ culture served as the reference method for IVS, with complete spermatogenesis identified in 80% of cultivated prepubertal tissue fragments. So far, this is the first report applying a 3D bioprinting approach for IVS. Further optimization of the scaffold design and seeding parameters might be permissive for tubular architecture recreation and thereby increase the efficiency of IVS in printed testicular constructs. While it remains to be tested whether the gametes generated on the alginate-based scaffolds can support embryogenesis following IVF, this IVS approach might be useful for (patho)physiological studies and drug-screening applications.

The relative importance of genetic parenthood

RESEARCH QUESTION

How much do patients with severe infertility and their gynaecologists value genetic parenthood relative to other key treatment characteristics?

DESIGN

A discrete choice experiment included the following treatment characteristics: genetic parenthood, pregnancy rate, curing infertility, maternal health, child health and costs. The questionnaire was disseminated between 2015 and 2016 among Dutch and Belgian patients with severe infertility and their gynaecologists.

RESULTS

The questionnaire was completed by 173 patients and 111 gynaecologists. When choosing between treatments that varied in safety, effectiveness and costs, the treatment's ability to lead to genetic parenthood did not affect the treatment preference of patients with severe infertility (n = 173). Genetic parenthood affected the treatment preference of gynaecologists (n = 111) less than all other treatment characteristics. Patients indicated that they would switch to a treatment that did not enable genetic parenthood in return for a child health risk reduction of 3.6%, a cost reduction of €3500, an ovarian hyperstimulation risk reduction of 4.6%, a maternal cancer risk reduction of 2.7% or a pregnancy rate increase of 18%. Gynaecologists made similar trade-offs.

CONCLUSIONS

While awaiting replication of this study in larger populations, these findings challenge the presumed dominant importance of genetic parenthood. This raises questions about whether donor gametes could be presented as a worthy alternative earlier in treatment trajectories and whether investments in novel treatments enabling genetic parenthood, like in-vitro gametogenesis, are proportional to their future clinical effect.

Broad support for regulating the clinical implementation of future reproductive techniques

STUDY QUESTION

Do gynaecologists, infertile patients and the general public, consider that regulation of the clinical implementation of stem cell-based fertility treatments is required?

SUMMARY ANSWER

There is broad support from gynaecologists, patients and the general public for regulating the clinical implementation of future stem cell-based fertility treatments.

WHAT IS KNOWN ALREADY

There is debate on the need to regulate the clinical implementation of novel techniques. Regulation may hinder their swift adoption and delay benefits for patients, but may prevent the implementation of ineffective or harmful techniques. Stem cell-based fertility treatments, which involve creating oocytes or spermatozoa by manipulating stem cells, are likely to be implemented in clinical practice in the near future and will probably impact future generations as well as the current one.

STUDY DESIGN, SIZE, DURATION

A cross-sectional survey was conducted among gynaecologists working in fertility clinics (n = 179), patients with severe infertility (n = 348) and a representative sample of the general public (n = 1250). The questionnaire was disseminated in the Netherlands in the winter of 2015-2016.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The newly developed questionnaire was reviewed by experts and tested among the general public. The questionnaire assessed whether participants wanted each of nine potential negative consequences of the clinical implementation of stem cell-based fertility treatments to be regulated. In addition, the importance of all negative and positive potential consequences, the appropriate regulatory body and its need to consult with advisors from various backgrounds was questioned.

MAIN RESULTS AND THE ROLE OF CHANCE

In total, 958 respondents completed the questionnaire (response rate: 54%). A large majority of each participant group (>85%) wanted regulation, for at least one potential negative consequence of the clinical implementation of stem cell-based fertility treatments. The majority of all participant groups wanted regulation for serious health risks for intended parents, serious health risks for children and the disposal of human embryos. Regulation for out-of-pocket costs and the burden of treatment received little support. The majority of gynaecologists and the general public, but not the patients, requested regulation for the risk of minor congenital abnormalities, the success rates and the naturalness of treatments. Nevertheless, the majority of patients did consider the former two potential negative consequences important. The majority of all groups preferred a national bioethics committee as the regulatory body. This committee should consult with advisors from various backgrounds and should consider the broader context of potential consequences of the stem cell-based fertility treatments.

LIMITATIONS, REASONS FOR CAUTION

This empirical study focuses on only three stakeholder groups. This study reports on the perspective of the majority and this is not per definition the morally right perspective. The transferability of our findings to other cultures and other techniques remains unclear.

WIDER IMPLICATIONS OF THE FINDINGS

A national bioethics committee, consulting with advisors from various backgrounds, should regulate the clinical implementation of future stem cell-based fertility treatments. Whether this broad support for regulation applies to novel techniques from other fields of medicine should be examined.

STUDY FUNDING/COMPETING INTEREST(S)

The Young Academy of the Royal Netherlands Academy of Arts and Sciences. None of the authors has any conflict of interest to declare.

TRIAL REGISTRATION NUMBER

Not applicable.

The ethics of clinical applications of germline genome modification: a systematic review of reasons

STUDY QUESTION

What are the reasons for or against the future clinical application of germline genome modification (GGM)?

SUMMARY ANSWER

A total of 169 reasons were identified, including 90 reasons for and 79 reasons against future clinical application of GGM.

WHAT IS KNOWN ALREADY

GGM is still unsafe and insufficiently effective for clinical purposes. However, the progress made using Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)- CRISPR-associated system (Cas) has led scientists to expect to overcome the technical hurdles in the foreseeable future. This has invited a debate on the socio-ethical and legal implications and acceptability of clinical applications of GGM. However, an overview of the reasons presented in this debate is missing.

STUDY DESIGN, SIZE, DURATION

MEDLINE was systematically searched for articles published between January 2011 and June 2016. Articles covering reasons for or against clinical application of intentional modification of the nuclear DNA of the germline were included.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Two researchers independently extracted the reported reasons from the articles and grouped them into categories through content analysis.

MAIN RESULTS AND THE ROLE OF CHANCE

The systematic search yielded 1179 articles and 180 articles were included. Most papers were written by professionals in ethics, (science) journalism and biomedical sciences. Overall, 169 reasons were identified, including 90 reasons for, and 79 reasons against future clinical application of GGM. None of the included articles mentioned more than 60/169 reasons. The reasons could be categorized into: (i) quality of life of affected individuals; (ii) safety; (iii) effectiveness; (iv) existence of a clinical need or alternative; (v) costs; (vi) homo sapiens as a species (i.e. relating to effects on our species); (vii) social justice; (viii) potential for misuse; (ix) special interests exercising influence; (x) parental rights and duties; (xi) comparability to acceptable processes; (xii) rights of the unborn child; and (xiii) human life and dignity. Considerations relating to the implementation processes and regulation were reported.

LIMITATIONS, REASONS FOR CAUTION

We cannot ensure completeness as reasons may have been omitted in the reviewed literature and our search was limited to MEDLINE and a 5-year time period.

WIDER IMPLICATIONS OF THE FINDINGS

Besides needing (pre)clinical studies on safety and effectiveness, authors call for a sound pre-implementation process. This overview of reasons may assist a thorough evaluation of the responsible introduction of GGM.

STUDY FUNDING/COMPETING INTEREST(S)

University of Amsterdam, Alliance Grant of the Amsterdam Reproduction and Development Research Institute (I.D.), and Clinical Center, Department of Bioethics, National Institutes of Health Intramural Research Program (S.H.). There are no competing interests.

Ethics of stem cell-derived gametes made in a dish: fertility for everyone?

A timely and thoughtful discussion of the ethical challenges and societal impacts presented by the recent reports demonstrating the successful in vitro generation of functional gametes from somatic and pluripotent stem cells.

The acceptability of stem cell-based fertility treatments for different indications

STUDY QUESTION

What is the acceptability of using stem cell-based fertility treatments (SCFT) for different indications according to gynaecologists and the general public?

SUMMARY ANSWER

The majority of gynaecologists and the general public accept SCFT for the indications female or male infertility in young heterosexual couples, and female infertility in single women and same-sex couples.

WHAT IS KNOWN ALREADY

SCFT could result in genetic parenthood for intended parents with indications that cannot be treated using currently available methods, such as being in a same-sex relationship or female post-menopausal age. It is unclear whether the acceptability of SCFT differs between indications for treatment and whether gynaecologists and the general public differ in their assessments.

STUDY DESIGN SIZE, DURATION

In November 2015, a cross-sectional survey was disseminated among 179 gynaecologists and a panel of 1250 respondents comprising a representative sample of the Dutch general public.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The potential indications for future SCFT to achieve genetic parenthood were identified by literature review. A questionnaire was developed, reviewed by experts from different disciplines and tested among the general public. The questionnaire asked whether treating eight groups of intended parents with SCFT was acceptable or not. Regression analysis examined whether demographic characteristics influenced choices and whether the general public and gynaecologists differed in opinion.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 82 (46%) gynaecologists and 772 (62%) members of the general public completed the survey. The acceptability of using SCFT varied according to both gynaecologists and the general public between the eight groups of intended parents (P < 0.001). The majority of the Dutch general public accepts SCFT for six out of eight possible indications, namely female infertility in young heterosexual couples (94%), male infertility in young heterosexual couples (94%), unexplained infertility in young heterosexual couples (83%), female infertility in single women (69%), lesbian couples (68%) and gay couples (62%). The majority of gynaecologists also found treating these groups acceptable, except for the indication of unexplained infertility, which was only accepted by a minority of gynaecologists (43%). A minority of both the general public and gynaecologists accepted SCFT for fertile women who want a child that is genetically only her own (27 and 6%, respectively) and for female infertility in heterosexual couples in which the woman is over 50 years of age (17% and 26%, respectively). Attaching low importance to religion, having progressive political preferences, not having a university degree, having experienced infertility, being a woman, being older and not being of European ethnicity were positively associated with considering using SCFT acceptable for one or multiple indications.

LARGE SCALE DATA

N/A.

LIMITATIONS REASONS FOR CAUTION

The generalizability of our findings to future decades or other countries might be limited as opinions about novel technologies change over time and might vary across cultures. Support among gynaecologists and the general public is interesting but not proof of ethical acceptability.

WIDER IMPLICATIONS OF THE FINDINGS

Once proven safe and effective, fear of limited acceptability by the general public is unwarranted, and thus should not stop gynaecologists from offering SCFT to single infertile women and same-sex couples in addition to young infertile heterosexual couples.

STUDY FUNDING AND COMPETING INTEREST(S)

Funded by the Young Academy of the Royal Netherlands Academy of Arts and Sciences and the Universities of Amsterdam and Leuven. No conflict of interest to declare.

The importance of genetic parenthood for infertile men and women

STUDY QUESTION

Do men and women beginning to attend a fertility clinic prefer genetic over non-genetic parenthood?

SUMMARY ANSWER

Nearly, all infertile men and women prefer genetic parenthood.

WHAT IS KNOWN ALREADY

Clinicians assume that all infertile couples prefer genetic parenthood over non-genetic parenthood and, therefore, consider treatments with donor gametes an option of last resort. Previous studies of the desire for parenthood identified 30 motivations for genetic parenthood, and 51 motivations for which having a genetically related child is not strictly necessary but might be deemed required. The exact strength of the preference of infertile men and women for genetic parenthood remains unclear, as does the importance of the various motivations.

STUDY DESIGN, SIZE, DURATION

A questionnaire was developed based on a literature review. It was assessed by professionals and pilot tested among patients. The coded paper-pencil questionnaire was disseminated among both partners of 201 heterosexual infertile couples after their first consultation at one of two Belgian fertility clinics between October 2015 and May 2016.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The survey addressed: (i) the preference for genetic parenthood for themselves and for their partner, (ii) the importance of 30 motivations for genetic parenthood and (iii) the importance of 51 other motivations for parenthood and whether these motivations require being the genetic parent of their child to be fulfilled. To simplify presentation of the results, all 81 motivations were grouped into reliable categories of motivations using psychometric analyses.

MAIN RESULTS AND THE ROLE OF CHANCE

The survey was completed by 104 women and 91 men (response rate: 49%). Almost all respondents (98%) favored genetic over non-genetic parenthood for both their partner and themselves. One-third of the respondents stated they only wanted to parent their own genetically related child. Achieving genetic parenthood for their partner was considered significantly more important than achieving genetic parenthood for themselves. Within couples, men had a stronger preference for genetic parenthood (P = 0.004), but this was not significant after correction for educational level, which was significantly associated with the preference of both men and women. The 30 motivations for becoming a genetic parent clustered into 11 categories of which 'to experience a natural process' was deemed most important. The 51 motivations for becoming a parent for which having a genetically related child is not strictly necessary clustered into 14 categories of which 'to contribute to a child's well-being' and 'to experience the love of a child' were most important. Respondents deemed they would need to be the genetic parent of their child to fulfill nearly all their motivations for parenthood.

LIMITATIONS REASONS FOR CAUTION

We included couples that visited the fertility clinic for the first time, and the preference for genetic parenthood might change throughout a fertility treatment trajectory. Moreover, what prospective parents expect to be important for their future well-being might not really define parents' well-being.

WIDER IMPLICATIONS OF THE FINDINGS

The presumed preference of couples for genetic parenthood was confirmed. Resistance against using donor gametes is more likely among lower educated individuals. Researching whether non-genetic parents actually feel they cannot fulfill the 51 motivations for parenthood, could be a basis for developing patient information.

STUDY FUNDING/COMPETING INTEREST(S)

Funded by the Parkes Foundation, the University of Amsterdam and the Leuven University Hospital. No conflict of interest.

Using stem cell-derived gametes for same-sex reproduction: an alternative scenario

It has been suggested that future application of stem-cell derived gametes (SCD-gametes) might lead to the possibility for same-sex couples to have genetically related children. Still, for this to become possible, the technique of gamete derivation and techniques of reprogramming somatic cells to a pluripotent state (directly or via somatic cell nuclear transfer) would have to be perfected. Moreover, egg cells would have to be derived from male cells and sperm cells from female cells, which is believed to be particularly difficult, if not impossible. We suggest a more plausible scenario to provide same-sex couples with the possibility to parent a child who is genetically related to both parents. Although technical feasibility is an advantage (also in terms of safety), disadvantages are that cooperation of a donor of the opposite sex is still required and that the partners are genetically linked to the resulting child in a different degree. However, since in our scenario the donor's genetic contribution would not outweigh any of the parents' genetic contribution, this alternative route may ease the fear for a possible parental claim by the donor. Like many other applications in the field of infertility treatment, the goal to create SCD-gametes for reproductive purposes is largely based on the high value attributed to genetic parenthood. Although we believe that genetic relatedness is neither a necessary nor a sufficient condition for 'good' parenthood, we do believe that many people may consider our scenario a welcome alternative.

Balancing Ethical Pros and Cons of Stem Cell Derived Gametes

In this review we aim to provide an overview of the most important ethical pros and cons of stem cell derived gametes (SCD-gametes), as a contribution to the debate about reproductive tissue engineering. Derivation of gametes from stem cells holds promising applications both for research and for clinical use in assisted reproduction. We explore the ethical issues connected to gametes derived from embryonic stem cells (both patient specific and non-patient specific) as well as those related to gametes derived from induced pluripotent stem cells. The technology of SCD-gametes raises moral concerns of how reproductive autonomy relates to issues of embryo destruction, safety, access, and applications beyond clinical infertility.

Endogenous, very small embryonic-like stem cells: critical review, therapeutic potential and a look ahead

BACKGROUND

Both pluripotent very small embryonic-like stem cells (VSELs) and induced pluripotent stem (iPS) cells were reported in 2006. In 2012, a Nobel Prize was awarded for iPS technology whereas even today the very existence of VSELs is not well accepted. The underlying reason is that VSELs exist in low numbers, remain dormant under homeostatic conditions, are very small in size and do not pellet down at 250-280g. The VSELs maintain life-long tissue homeostasis, serve as a backup pool for adult stem cells and are mobilized under stress conditions. An imbalance in VSELs function (uncontrolled proliferation) may result in cancer.

SEARCH METHODS

The electronic database 'Medline/Pubmed' was systematically searched with the subject heading term 'very small embryonic-like stem cells'.

OBJECTIVE AND RATIONALE

The most primitive stem cells that undergo asymmetric cell divisions to self-renew and give rise to progenitors still remain elusive in the hematopoietic system and testes, while the presence of stem cells in ovary is still being debated. We propose to review the available literature on VSELs, the methods of their isolation and characterization, their ontogeny, how they compare with embryonic stem (ES) cells, primordial germ cells (PGCs) and iPS cells, and their role in maintaining tissue homeostasis. The review includes a look ahead on how VSELs will result in paradigm shifts in basic reproductive biology.

OUTCOMES

Adult tissue-specific stem cells including hematopoietic, spermatogonial, ovarian and mesenchymal stem cells have good proliferation potential and are indeed committed progenitors (with cytoplasmic OCT-4), which arise by asymmetric cell divisions of pluripotent VSELs (with nuclear OCT-4). VSELs are the most primitive stem cells and postulated to be an overlapping population with the PGCs. Rather than migrating only to the gonads, PGCs migrate and survive in various adult body organs throughout life as VSELs. VSELs express both pluripotent and PGC-specific markers and are epigenetically and developmentally more mature compared with ES cells obtained from the inner cell mass of a blastocyst-stage embryo. As a result, VSELs readily differentiate into three embryonic germ layers and spontaneously give rise to both sperm and oocytes in vitro. Like PGCs, VSELs do not divide readily in culture, nor produce teratoma or integrate in the developing embryo. But this property of being relatively quiescent allows endogenous VSELs to survive various kinds of toxic insults. VSELs that survive oncotherapy can be targeted to induce endogenous regeneration of non-functional gonads. Transplanting healthy niche (mesenchymal) cells have resulted in improved gonadal function and live births.

WIDER IMPLICATIONS

Being quiescent, VSELs possibly do not accumulate genomic (nuclear or mitochondrial) mutations and thus may be ideal endogenous, pluripotent stem cell candidates for regenerative and reproductive medicine. The presence of VSELs in adult gonads and the fact that they survive oncotherapy may obviate the need to bank gonadal tissue for fertility preservation prior to oncotherapy. VSELs and their ability to undergo spermatogenesis/neo-oogenesis in the presence of a healthy niche will help identify newer strategies toward fertility restoration in cancer survivors, delaying menopause and also enabling aged mothers to have better quality eggs.

Gamete activation: basic knowledge and clinical applications

Background

The first clues to the process of gamete activation date back to nearly 60 years ago. The mutual activation of gametes is a crucial event during fertilization. In the testis and ovaries, spermatozoa and oocytes are in a state of meiotic and metabolic quiescence and require reciprocal signals in order to undergo functional changes that lead to competence for fertilization. First, the oocyte activates sperm by triggering motility, chemoattraction, binding and the acrosome reaction, culminating with the fusion of the two plasma membranes. At the end of this cascade of events, collectively known as sperm capacitation, sperm-induced oocyte activation occurs, generating electrical, morphological and metabolic modifications in the oocyte.

Objective and rationale

The aim of this review is to provide the current state of knowledge regarding the entire process of gamete activation in selected specific animal models that have contributed to our understanding of fertilization in mammals, including humans. Here we describe in detail the reciprocal induction of the two activation processes, the molecules involved and the mechanisms of cell interaction and signal transduction that ultimately result in successful embryo development and creation of a new individual.

Search methods

We carried out a literature survey with no restrictions on publication date (from the early 1950s to March 2016) using PubMed/Medline, Google Scholar and Web of Knowledge by utilizing common keywords applied in the field of fertilization and embryo development. We also screened the complete list of references published in the most recent research articles and relevant reviews published in English (both animal and human studies) on the topics investigated.

Outcomes

Literature on the principal animal models demonstrates that gamete activation is a pre-requisite for successful fertilization, and is a process common to all species studied to date. We provide a detailed description of the dramatic changes in gamete morphology and behavior, the regulatory molecules triggering gamete activation and the intracellular ions and second messengers involved in active metabolic pathways in different species. Recent scientific advances suggest that artificial gamete activation may represent a novel technique to improve human IVF outcomes, but this approach requires caution.

Wider implications

Although controversial, manipulation of gamete activation represents a promising tool for ameliorating the fertilization rate in assisted reproductive technologies. A better knowledge of mechanisms that transform the quiescent oocyte into a pluripotent cell may also provide new insights for the clinical use of stem cells.

Couples with non-obstructive azoospermia are interested in future treatments with artificial gametes

STUDY QUESTION

Would couples diagnosed with non-obstructive azoospermia (NOA) consider two future treatments with artificial gametes (AGs) as alternatives for testicular sperm extraction followed by ICSI (TESE-ICSI)?

SUMMARY ANSWER

Most couples with NOA (89%) would opt for treatment with AGs before attempting TESE-ICSI and/or after failed TESE-ICSI.

WHAT IS KNOWN ALREADY

Couples with NOA who undergo TESE-ICSI have a 25% chance of conceiving a child. Two future treatments that are being developed are 'ICSI with artificial sperm formed from somatic cells' (ICSI with AGs) and 'natural conception after autotransplantation of in vitro proliferated spermatogonial stem cells' (natural conception with AGs). It is unknown what treatment preferences patients have.

STUDY DESIGN, SIZE, DURATION

A cross-sectional survey conducted in 2012-2013, addressing all 921 couples diagnosed with NOA and treated with TESE-ICSI in Dutch fertility clinics between 2007 and 2012. The coded questionnaires were sent by mail and followed up with two reminders.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We developed the questionnaire based on a literature review and previous qualitative interviews, and included treatment preference and the valuation of nine treatment characteristics. We assessed reliability of the questionnaires and calculated mean importance scores (MISs: 0-10) of each treatment characteristic. We assessed which patient and treatment characteristics were associated with a couple's hypothetical treatment preference using binominal regression.

MAIN RESULTS AND THE ROLE OF CHANCE

The vast majority (89%) of the 494 responding couples (response rate: 54%) would potentially opt for AGs as a first and/or a last resort treatment option. More specifically, as a first treatment couples were likely (67%) to prefer natural conception with AGs over TESE-ICSI and less likely to prefer ICSI with AGs over TESE-ICSI (34%). After failed TESE-ICSI, the majority of couples (75%) would want to attempt ICSI with AGs as a last resort option. The most important characteristics of treatment were safety for children (MIS: 8.2), pregnancy rates (MIS: 7.7) and curing infertility (MIS: 6.8). Costs, burden, naturalness and technological sophistication were of about equal importance (MIS: 3.1-4.0). The majority of patients rated conception at home and moral acceptability as not important (MIS: 1.7 and 0.8, respectively), but the importance attributed to these variables did still affect patients' likeliness to opt for AGs.

LIMITATIONS AND REASONS FOR CAUTION

Couples with NOA not opting for TESE-ICSI were not included and might have other perspectives. Couples' hypothetical choices for AGs might differ from their actual choices once data on the costs, safety and pregnancy rates become available from these new treatment options.

WIDER IMPLICATIONS OF THE FINDINGS

The interest of couples with NOA in potential future treatments with AGs encourages further pre-clinical research. Priority setting for research and future decision-making on clinical application of AGs should take all characteristics important to patients into account.

STUDY FUNDING/COMPETING INTERESTS

The authors report no financial or other conflict of interest relevant to the subject of this article.

A Review of New Technologies that may Become Useful for in vitro Production of Boar Sperm

Making sperm cells outside the original testicular environment in a culture dish has been considered for a long time as impossible due to the very complicated process of spermatogenesis and sperm maturation, which altogether, encompasses a 2-month period. However, new approaches in complex three-dimensional co-cell cultures, micro-perfusion and micro-fluidics technologies, new knowledge in the functioning, culturing and differentiation of spermatogonial stem cells (SSC) and their precursor cells have revolutionized this field. Furthermore, the use of better molecular markers as well as stimulatory factors has led to successful in vitro culture of stem cells either derived from germ line stem cells, from induced pluripotent stem cells (iPSC) or from embryonic stem cells (ESC). These stem cells when placed into small seminiferous tubule fragments are able to become SSC. The SSC beyond self-renewal can also be induced into haploid sperm-like cells under in vitro conditions. In mouse, this in vitro produced sperm can be injected into a mature oocyte and allow post-fertilization development into an early embryo in vitro. After transferring such obtained embryos into the uterus of a recipient mouse, they can further develop into healthy offspring. Recently, a similar approach has been performed with combining selected cells from testicular cell suspensions followed by a complete in vitro culture of seminiferous cords producing sperm-like cells. However, most of the techniques developed are laborious, time-consuming and have low efficiency, placing questionable that it will become useful used for setting up an efficient in vitro sperm production system for the boar. The benefits and drawbacks as well as the likeliness of in vitro pig sperm production to become applied in assisted technologies for swine reproduction are critically discussed. In this contribution, also the process of sperm production in the testis and sperm maturation is reviewed.

Cell-specific ablation in the testis: what have we learned?

Testicular development and function is the culmination of a complex process of autocrine, paracrine and endocrine interactions between multiple cell types. Dissecting this has classically involved the use of systemic treatments to perturb endocrine function, or more recently, transgenic models to knockout individual genes. However, targeting genes one at a time does not capture the more wide‐ranging role of each cell type in its entirety. An often overlooked, but extremely powerful approach to elucidate cellular function is the use of cell ablation strategies, specifically removing one cellular population and examining the resultant impacts on development and function. Cell ablation studies reveal a more holistic overview of cell–cell interactions. This not only identifies important roles for the ablated cell type, which warrant further downstream study, but also, and importantly, reveals functions within the tissue that occur completely independently of the ablated cell type. To date, cell ablation studies in the testis have specifically removed germ cells, Leydig cells, macrophages and recently Sertoli cells. These studies have provided great leaps in understanding not possible via other approaches; as such, cell ablation represents an essential component in the researchers’ tool‐kit, and should be viewed as a complement to the more mainstream approaches to advancing our understanding of testis biology. In this review, we summarise the cell ablation models used in the testis, and discuss what each of these have taught us about testis development and function.