Achievements and future perspectives of embryo transfer technology in pigs.

Commercial embryo transfer (ET) has unprecedented productive and economic implications for the pig sector. However, pig ET has been considered utopian for decades mainly because of the requirements of surgical techniques for embryo collection and embryo deposition into recipients, alongside challenges to preserve embryos. This situation has drastically changed in the last decade since the current technology allows non-surgical ET and short- and long-term embryo preservation. Here, we provide a brief review of the improvements in porcine ET achieved by our laboratory in the past 20 years. This review includes several aspects of non-surgical ET technology and different issues affecting ET programmes and embryo preservation systems. The future perspectives of ET technology are also considered. We will refer only to embryos produced in vivo since they are the only type of embryos with possible short-term use in pig production.

Embryo donation and understanding of kinship: the impact of law and policy.

STUDY QUESTION: What is the impact of law and policy upon the experience of embryo donation for reproductive use? SUMMARY ANSWER: Access to, and experience of, embryo donation are influenced by a number of external factors including laws that impose embryo storage limits, those that frame counselling and approval requirements and allow for, or mandate, donor identity disclosure. WHAT IS KNOWN ALREADY: To date only three qualitative studies in Australia and New Zealand have been completed on the experience of embryo donation for reproductive purposes, each with a small cohort of interviewees and divergent findings. STUDY DESIGN, SIZE, DURATION: Embryo donors, recipients, and would-be donors were interviewed between July 2010 and July 2012, with three additional interviews between September 2015 and September 2016, on their experiences of embryo donation. The sampling protocol had the advantage of addressing donation practices across multiple clinical sites under distinct legal frameworks. PARTICIPANTS/MATERIALS, SETTINGS, METHODS: Participants were recruited from five Australian jurisdictions and across 11 clinical sites. Twenty-six participants were interviewed, comprising: 11 people who had donated embryos for the reproductive use of others (nine individuals and one couple), six recipients of donated embryos (four individuals and one couple) and nine individuals who had attempted to donate, or had a strong desire to donate, but had been prevented from doing so. In total, participants reported on 15 completed donation experiences; of which nine had resulted in offspring to the knowledge of the donor. MAIN RESULTS AND THE ROLE OF CHANCE: Donors positively desired donation and did not find the decision difficult. Neither donors nor recipients saw the donation process as akin to adoption . The process and practice of donation varied considerably across different jurisdictions and clinical sites. LIMITATIONS, REASONS FOR CAUTION: Because the pool of donors and recipients is small, caution must be exercised over drawing general conclusions. Saturation was not reached on themes of counselling models and future contact. WIDER IMPLICATIONS OF THE FINDINGS: The differences between our findings and those of a previous study are attributable to varied legal and counselling regimes. Therefore, law and policy governing embryo storage limits, counselling protocols and identity disclosure shape the donation experience and how it is described. STUDY FUNDING/COMPETING INTERESTS: This research was supported by Discovery Project Grants DP 0986213 and 15010157 from the Australian Research Council and additional funding from UTS: Law. There are no conflicts of interest to declare. TRIAL REGISTRATION NUMBER: Not applicable.

The association between embryo storage time and treatment success in women undergoing freeze-all embryo transfer.

OBJECTIVE: To investigate the relationship between the embryo frozen time and live birth rate (LBR) in women having a freeze-all cycle. DESIGN: Retrospective cohort study. SETTING: Academic hospital. PATIENT(S): Women who underwent their first vitrified-warmed cycles from January 2013 to December 2019. INTERVENTION(S): Embryo storage time. MAIN OUTCOME MEASURE(S): The primary outcome was the LBR. RESULT(S): A total of 14,928 women were eligible for the analysis. Women with the frozen time of transferred embryos for 2-5 months were associated with a higher LBR compared with other groups. The results were confirmed by an inverted U curve in the restricted cubic splines before as well as after adjustment for covariables, which suggested that an embryo storage time of 3-4 months was associated with the highest LBR. Subgroup analyses demonstrated that the inverted U curve relationship between embryo storage time and LBR was only observed in women with the high response. Sensitivity analyses in women with at least one good-quality embryo for transfer, in women aged <36 years at embryo transfer, or in women with double cleavage embryo transfer showed that the association remained valid. The association was weakened in women with single blastocyst transfer probably because of the small sample size in these women. CONCLUSION(S): An inverted U-shaped relationship was found between embryo storage time and treatment success in women with high ovarian response in freeze-all embryo transfer cycles. Prolonged storage time of >6 months was associated with reduced pregnancy rates.

Simple storage (CO2-free) of porcine morulae for up to three days maintains the in vitro viability and developmental competence.

The advancement of porcine embryo transfer (ET) technology is constrained by regulatory hurdles (liquid nitrogen transportation) or, more importantly, the technical obstacles of using vitrified embryos in combination with nonsurgical deep uterine ET technology. Maintaining embryos in culture during transport and prior ET collides with the need of CO2 gassing and the best choice of culture medium. In this work, we describe storage conditions for short-term embryo CO2-free storage that allowed for a majority of in vivo-derived porcine morulae to survive after 3 days of storage in a liquid state, and to develop to the blastocyst stage unhatched, a sanitary prerequisite for ET. The storage conditions included NCSU-23 medium supplemented with bovine serum albumin, where bicarbonate was partially replaced by HEPES to avoid the need for CO2 gassing, and a temperature of 37 °C. These conditions were able to maintain the functionality of the stored embryos (hatching capacity after exposure to conventional culture conditions) and their developmental competence after ET (normal fetuses by day 38 of pregnancy). Use of this strategy of CO2-free storage should allow the shipment of fresh embryos worldwide in the absence of liquid nitrogen.

Recent advances toward the practical application of embryo transfer in pigs.

Porcine embryo transfer (ET) technology has been in demand for decades because of its potential to provide considerable improvements in pig production with important sanitary, economic, and animal welfare benefits. Despite these advantages, the commercial use of ET is practically nonexistent. However, the two main obstacles hindering the commercial use of ET in pigs in the past several decades (i.e., surgical transfer and embryo preservation) have recently been overcome. A technique for nonsurgical deep-uterine (NsDU) ET of nonsedated gilts and sows, which was seemingly an impossible challenge just a few years ago, is a reality today. The improvements in embryo preservation that have been achieved in recent years and the excellent reproductive performance of the recipients after the NsDU-ET technique coupled with short-term and long-term-stored embryos represent essential progress for the international trade of porcine embryos and the practical use of ET by the pig industry. This review focuses, with an emphasis on our own findings, on the recent advances in embryo preservation and NsDU-ET technologies, which are starting to show potential for application under field conditions.

The use and disposal of stored embryos.

Claims that human embryos are "human beings" or "persons" cannot be agreed, because philosophies and approaches differ, awarding them statuses from full human to property. In 1984, the UK (Warnock) Committee of Inquiry into Human Fertilisation and Embryology made recommendations that still offer legal and ethical guidance. It is widely agreed, for instance, that embryos created through in vitro fertilization (IVF) should not be transferred for reproductive purposes without relevant consent, whether for gamete donors' or others' family-building. A consequence of courts enforcing parties' IVF agreements on stored embryo use or balancing parties' competing interests is that one party-usually the male-can veto the other's use of the embryo for reproduction on termination of a partnership. The extent to which surplus IVF embryos can be donated for research ranges from prohibition to infertility treatment and more, but wider needs for embryology research are appearing that, despite prevailing bans, may require embryos for study created to genetic specifications.