Birth of a healthy female after intracytoplasmic sperm injection of cryopreserved human oocytes

Oocyte and embryo cryopreservation in assisted reproductive technology: past achievements and current challenges

Cryopreservation has revolutionized the treatment of infertility and fertility preservation. This review summarizes the milestones that paved the way to the current routinary clinical implementation of this game-changing practice in assisted reproductive technology. Still, evidence to support "the best practice" in cryopreservation is controversial and several protocol adaptations exist that were described and compared here, such as cumulus-intact vs. cumulus-free oocyte cryopreservation, artificial collapse, assisted hatching, closed vs. open carriers, and others. A last matter of concern is whether cryostorage duration may impact oocyte/embryo competence, but the current body of evidence in this regard is reassuring. From social and clinical perspectives, oocyte and embryo cryopreservation has evolved from an afterthought when assisted reproduction was intended for immediate pregnancy with supernumerary embryos of secondary interest to its current purpose, which primarily is to preserve fertility long-term and more comprehensively allow for family planning. However, the initial consenting process, which still is geared to short-term fertility care, may no longer be relevant when the individuals that initially preserved the tissues have completed their reproductive journey. A more encompassing counseling model is required to address changing patient values over time.

A comprehensive review and update on human fertility cryopreservation methods and tools

The broad conceptualization of fertility preservation and restoration has become already a major concern in the modern western world since a large number of individuals often face it in the everyday life. Driven by different health conditions and/or social reasons, a variety of patients currently rely on routinely and non-routinely applied assisted reproductive technologies, and mostly on the possibility to cryopreserve gametes and/or gonadal tissues for expanding their reproductive lifespan. This review embraces the data present in human-focused literature regarding the up-to-date methodologies and tools contemporarily applied in IVF laboratories' clinical setting of the oocyte, sperm, and embryo cryopreservation and explores the latest news and issues related to the optimization of methods used in ovarian and testicular tissue cryopreservation.

Current Trends on Bioengineering Approaches for Ovarian Microenvironment Reconstruction

Ovarian tissue has a unique microarchitecture and a complex cellular and molecular dynamics that are essential for follicular survival and development. Due to this great complexity, several factors may lead to ovarian insufficiency, and therefore to systemic metabolic disorders and female infertility. Techniques currently used in the reproductive clinic such as oocyte cryopreservation or even ovarian tissue transplant, although effective, have several limitations, which impair their wide application. In this scenario, mimetic ovarian tissue reconstruction comes as an innovative alternative to develop new methodologies for germ cells preservation and ovarian functions restoration. The ovarian extracellular matrix (ECM) is crucial for oocyte viability maintenance, once it acts actively in folliculogenesis. One of the key components of ovarian bioengineering is biomaterials application that mimics ECM and provides conditions for cell anchorage, proliferation, and differentiation. Therefore, this review aims at describing ovarian tissue engineering approaches and listing the main limitations of current methods for preservation and reestablishment of ovarian fertility. In addition, we describe the main elements that structure this study field, highlighting the main advances and the challenges to overcome to develop innovative methodologies to be applied in reproductive medicine. Impact Statement This review presents the main advances in the application of tissue bioengineering in the ovarian tissue reconstruction to develop innovative solutions for ovarian fertility reestablishment.

Past, present and future of ICSI in livestock species

During the past 2 decades, intracytoplasmic sperm injection (ICSI) has become a routine technique for clinical applications in humans. The widespread use among domestic species, however, has been limited to horses. In horses, ICSI is used to reproduce elite individuals and, as well as in humans, to mitigate or even circumvent reproductive barriers. Failures in superovulation and conventional in vitro fertilization (IVF) have been the main reason for the use of this technology in horses. In pigs, ICSI has been successfully used to produce transgenic animals. A series of factors have resulted in implementation of ICSI in pigs: need to use zygotes for numerous technologies, complexity of collecting zygotes surgically, and problems of polyspermy when there is utilization of IVF procedures. Nevertheless, there have been very few additional reports confirming positive results with the use of ICSI in pigs. The ICSI procedure could be important for use in cattle of high genetic value by maximizing semen utilization, as well as for utilization of spermatozoa from prepubertal bulls, by providing the opportunity to shorten the generation interval. When attempting to utilize ICSI in ruminants, there are some biological limitations that need to be overcome if this procedure is going to be efficacious for making genetic improvements in livestock in the future. In this review article, there is an overview and projection of the methodologies and applications that are envisioned for ICSI utilization in these species in the future.

Oncofertility Perspectives for Girls with Cancer

Infertility is a serious early, as well as late, effect of childhood cancer treatment. If addressed in a timely manner at diagnosis, fertility preservation measures can be taken, preferably before the start of cancer treatment. However, pediatric oncologists might remain reluctant to offer counseling on fertility-preservation methods, although infrastructure to freeze ovarian tissue has become available and is currently considered standard care for pre- and postpubertal girls at high risk of gonadal damage. More importantly, risk factors have been identified for cancer treatment-related impairment of gonadal function, and the first successful pregnancies have been reported after autotransplanted ovarian tissue, which has been harvested from children. Additionally, great progress has been made in the field of ex vivo maturation of oocytes in frozen ovarian tissue, which provides opportunities for those at risk of ovarian micrometastasis. Hence, it is time to counsel girls at risk and make every effort to cryopreserve their ovarian tissue, now more than ever before.

History of fertility preservation

Background: Fertility preservation refers to a procedure performed to maintain the ability to become pregnant before receiving treatment with a risk of fertility loss, such as chemo- or radiation therapy. Examples of fertility-preserving procedures include freezing, sperm freezing, embryo freezing through in vitro fertilization, and ovarian tissue freezing.Current Concepts: Until the late 1990s, awareness of fertility preservation among clinicians and patients was relatively low, and the only way to preserve and restore fertility in women with cancer was the cryopreservation of embryos. However, as the survival rate of cancer patients increased and the treatment results of various diseases improved, interest in quality of life such as pregnancy and childbirth after treatment gradually increased, and became a driving force for the development of fertility preservation. In the 2000s, several centers began cryopreserving ovarian tissue, including primordial follicles from young patients before chemotherapy. Currently, ovarian tissue cryopreservation can be used in combination with in vitro maturation and egg vitrification techniques. Novel methods to improve follicle survival after transplantation are currently being investigated. Methods to improve follicle survival after transplantation and new ovarian protective agents to protect the ovaries from cytotoxic agents are currently being studied.Discussion and Conclusion: Advances in fertility-preserving technologies in the future will contribute to the delivery of healthy children by providing tailored treatments and more individualized fertility-preserving strategies to patients whose fertility is at risk.

Successful Pregnancies, Births, and Child Development Following Oocyte Cryostorage in Female Cancer Patients During 25 Years of Fertility Preservation

Simple Summary

The study goal is to demonstrate that oocyte cryopreservation is a feasible and efficient option for fertility preservation in cancer patients through the comparison of in vitro fertilization treatments in nononcological patients.

Abstract

The preservation of fertility in cancer patients is a crucial aspect of modern reproductive medicine. Amenorrhea and infertility often occur after cancer therapy, worsening the quality of life. Cryopreservation of oocytes in young cancer patients is a therapeutic option for preserving fertility. A prospective study was conducted on 508 cancer patients who underwent oocyte cryopreservation to preserve fertility between 1996 and 2021 including the COVID-19 pandemic period. Patients underwent ovarian stimulation, followed by egg retrieval, and oocytes were cryopreserved by slow freezing or vitrification. Sixty-four thawing/warming cycles were performed. Survival, fertilization, pregnancy, and birth rate over the thawing/warming cycles were obtained. The data were compared with those from a group of 1042 nononcological patients who cryopreserved supernumerary oocytes. An average of 8.8 ± 6.9 oocytes were retrieved per cycle, and 6.1 ± 4.2 oocytes were cryopreserved. With their own stored oocytes, 44 patients returned to attempt pregnancy. From a total of 194 thawed/warmed oocytes, 157 survived (80%). In total, 100 embryos were transferred in 57 transfer/cycles, and 18 pregnancies were achieved. The pregnancy rate per transfer and pregnancy rate per patient were 31% and 41%, respectively. No statistically significant differences were observed between oncological patients and nononcological patients. A total of 15 babies were born from oncological patients. Children born showed normal growth and development. One minor malformation was detected.

Current status of assisted reproductive technologies in buffaloes

Buffaloes are raised by small farm holders primarily as source of draft power owing to its resistance to hot climate, disease, and stress conditions. Over the years, transformation of these animals from draft to dairy was deliberately carried out through genetic improvement program leading to the development of buffalo-based enterprises. Buffalo production is now getting more attention and interest from buffalo raisers due to its socioeconomic impact as well as its contribution to propelling the livestock industry in many developing countries. Reproduction of buffaloes, however, is confronted with huge challenge and concern as being generally less efficient to reproduce compared with cattle due to both intrinsic and extrinsic factors such as poor estrus manifestation, silent heat, marked seasonal infertility, postpartum anestrus, long calving interval, delayed puberty, inherently low number of primordial follicles in their ovaries, high incidence of atresia, and apoptosis. Assisted reproductive technologies (ARTs) are major interventions for the efficient utilization of follicle reserve in buffaloes. The present review focuses on estrus and ovulation synchronization for fixed time artificial insemination, in vitro embryo production, intracytoplasmic sperm injection, cryopreservation of oocytes and embryos, somatic cell nuclear transfer, the factors affecting utilization in various ARTs, and future perspectives in buffaloes.

Cryopreservation of Gametes and Embryos and Their Molecular Changes

The process of freezing cells or tissues and depositing them in liquid nitrogen at -196 °C is called cryopreservation. Sub-zero temperature is not a physiological condition for cells and water ice crystals represent the main problem since they induce cell death, principally in large cells like oocytes, which have a meiotic spindle that degenerates during this process. Significantly, cryopreservation represents an option for fertility preservation in patients who develop gonadal failure for any condition and those who want to freeze their germ cells for later use. The possibility of freezing sperm, oocytes, and embryos has been available for a long time, and in 1983 the first birth with thawed oocytes was achieved. From the mid-2000s forward, the use of egg vitrification through intracytoplasmic sperm injection has improved pregnancy rates. Births using assisted reproductive technologies (ART) have some adverse conditions and events. These risks could be associated with ART procedures or related to infertility. Cryopreservation generates changes in the epigenome of gametes and embryos, given that ART occurs when the epigenome is most vulnerable. Furthermore, cryoprotective agents induce alterations in the integrity of germ cells and embryos. Notably, cryopreservation extensively affects cell viability, generates proteomic profile changes, compromises crucial cellular functions, and alters sperm motility. This technique has been widely employed since the 1980s and there is a lack of knowledge about molecular changes. The emerging view is that molecular changes are associated with cryopreservation, affecting metabolism, cytoarchitecture, calcium homeostasis, epigenetic state, and cell survival, which compromise the fertilization in ART.

A major increase in oocyte cryopreservation cycles in the USA, Australia and New Zealand since 2010 is highlighted by younger women but a need for standardized data collection

STUDY QUESTION

What are the cohort trends of women undergoing oocyte cryopreservation (OC)?

SUMMARY ANSWER

There has been a dramatic increase in OC cycles undertaken each year since 2010, and the demographics of women accessing OC has shifted to a younger age group, but so far very few women have returned to use their cryopreserved oocytes in treatments.

WHAT IS KNOWN ALREADY

Although OC, as a method of fertility preservation, is offered around the world, global data are lacking on who is accessing OC, who is returning to thaw oocytes and whether these trends are changing.

STUDY DESIGN, SIZE, DURATION

A trinational retrospective cohort study was performed of 31 191 OC cycles and 972 oocyte thaw (OT) cycles undertaken in the USA (2010-2016) and 3673 OC and 517 OT cycles undertaken in Australia/New Zealand (Aus/NZ; 2010-2015).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Data were obtained from the USA Society for Assisted Reproductive Technology (SART) national registry and the Australian and New Zealand Assisted Reproduction Database (ANZARD). De-identified data were requested on all autologous oocyte freeze-all cycles and all cycles where autologous oocytes were thawed to be used in a treatment cycle for the time periods of interest.

MAIN RESULTS AND THE ROLE OF CHANCE

In both the USA and Aus/NZ, there has been a dramatic rise in the number of OC cycles performed each year (+880% in the USA from 2010 to 2016 and +311% in Aus/NZ from 2010 to 2015). Across both regions, most women undergoing OC were aged in their late 30s, but the average age decreased over time (USA: 36.7 years vs 34.7 years in 2010 and 2016, respectively). The number of women returning for thaw cycles was low (USA: 413 in 2016, Aus/NZ: 141 in 2015) and most thaw cycles (47%) across both regions involved oocytes that were frozen for <6 months. In the USA, a higher proportion of cycles resulted in a live birth when only thawed oocytes were used, compared to cycles that combined thawed oocytes with fresh oocytes (25% vs 11%, respectively; P < 0.001). Age at retrieval influenced live birth rate in the USA; 38% of thaw cycles started in women who stored oocytes when aged ≤35 years resulted in a live birth, whereas only 16% resulted in a live birth for women who stored oocytes when aged ≥36 years. Similar data were unobtainable from Aus/NZ.

LIMITATIONS, REASONS FOR CAUTION

There were limitations associated with both the SART and ANZARD data outputs received. The format in which the ANZARD data were provided, and the inconsistencies seen amongst cycle reporting in the SART dataset, restricted data interpretation. For example, both datasets did not provide a clear indication as to why women were undergoing OC and it was not possible to accurately calculate duration of storage for thaw cycles in the USA. We also did not obtain details on embryo quality from either database and acknowledge that embryo quality and subsequent outcome (embryo freezing or discard) would be of interest, especially when considering the efficacy of OC.

WIDER IMPLICATIONS OF THE FINDINGS

The data show that there is widespread demand for OC, and it is increasingly undertaken by younger women; however, the limitations encountered in the dataset support the need for a shift to a more uniform approach to data collection and presentation by large databases, worldwide.

STUDY FUNDING/COMPETING INTEREST(S)

This study received funding from the Fertility Society of Australia to support the ANZARD data extraction. M.J. is supported by an Australian Government Research Training Program Scholarship stipend. The authors declare no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Cryopreservation Protocols for Genetically Engineered Mice

Protocols for cryopreservation of mouse embryos and sperm are important for preserving genetically engineered mice (GEMs) used in research to study human development and diseases. Embryo cryopreservation is mainly carried out using either of two protocols: controlled gradual cooling or vitrification. Sperm cryopreservation protocols include two methodologies that are commonly referred to as JAX and CARD. Quality-control measures are necessary to ensure that GEMs are properly cryopreserved so that they can be retrieved for future use. An archiving system is also important in keeping proper records of frozen sperm and embryos. Frozen embryos and sperm are now preferred over live mice for shipping to distant locations. This article describes detailed protocols used in cryopreservation of mouse embryos and sperm, as well as their retrieval to live mice. © 2021 U.S. Government. Sperm cryopreservation Basic Protocol 1: JAX protocol for sperm cryopreservation Support Protocol 1: JAX protocol for making sperm cryopreservation medium Basic Protocol 2: JAX protocol for IVF of mouse sperm Alternate Protocol 1: Modified CARD protocol for sperm cryopreservation Support Protocol 2: CARD protocol for making sperm cryopreservation medium Alternate Protocol 2: CARD protocol for IVF of mouse sperm Embryo cryopreservation Basic Protocol 3: Cryopreserving and thawing 2-cell embryos Alternate Protocol 3: Cryopreserving and thawing 8-cell to morula-stage embryos Surgical transfer of embryos Basic Protocol 4: Infundibulum transfer of 2-cell to morula-stage embryos.

Live birth and clinical outcome of vitrification-warming donor oocyte programme: an experience of a single IVF unit

Medically assisted reproductive (MAR) treatments using donated oocytes are commonly applied in several countries to treat women who cannot conceive with their own gametes. Historically, in Italy, gamete donation has been prohibited but, in 2014, the law changed and gamete donation became allowed for couples undergoing MAR treatments. Consequently, in the last decade, there has been an increase in application of the oocyte donation programme. This study reports an egg-donation programme's clinical efficacy, based on importing donated vitrified oocytes from cryo-banks located in a foreign country. For this, we conducted a retrospective analysis of data from a single reproductive unit located in Italy (Donna Salus Women's Health and Fertility, Bozen). The study group consisted of 681 vitrified oocytes, which were warmed and culture to be replaced in 100 recipients. The survival rate after warming was 79.1% (n = 539/681), whereas the fertilization and blastulation rates were 90.2% (n = 486/539) and 47.9% (n = 233/486), respectively. Positive pregnancy test, clinical pregnancy rates, and live-birth rates per embryo transfer were 37.8%, 31.1% and 28.4%, respectively. The multiple pregnancy rate was 0.7%. This study is one of the first to report on the efficacy of a donor oocyte programme in Italy using imported vitrified oocytes. The above data may reassure women who are undertaking donation programmes using vitrified oocytes imported from commercial egg banks.

Thoughts on the popularity of ICSI

Purpose

Intracytoplasmic sperm injection (ICSI) is the most widely utilized assisted reproductive technique (ART) worldwide. In this feature, we review the early assisted fertilization attempts that eventually led to the development of ICSI, and discuss its current utilization in cases of male and non-male factor infertility.

Methods

We researched the literature related to the development, indications, and current use of ICSI, such as sperm structural abnormalities, male genetic indications, surgically retrieved sperm, high sperm chromatin fragmentation, oocyte dysmorphism, and preimplantation genetic testing (PGT). We also describe the potential future applications of ICSI.

Results

This review summarizes the early micromanipulation techniques that led to the inception of ICSI. We also explore its current indications, including non-male factor infertility, where its use is more controversial. Finally, we consider the benefits of future advancements in reproductive biology that may incorporate ICSI, such as in vitro spermatogenesis, neogametogenesis, and heritable genome editing.

Conclusion

The versatility, consistency, and reliability of ICSI have made it the most prevalently utilized ART procedure worldwide.

Cryopreservation of Mammalian Oocytes: Slow Cooling and Vitrification as Successful Methods for Cryogenic Storage

Two basic methods for the laboratory-focused cryopreservation of mammalian oocytes are described, based on work with murine oocytes. One method uses a relatively low concentration of the cryoprotectant propanediol plus sucrose and requires controlled rate cooling equipment to achieve a slow cooling rate. This method has also produced live births from cryopreserved human oocytes. The second method, which is described here, employs a high concentration of the cryoprotectant dimethyl sulfoxide plus a low concentration of polyethylene glycol. This is a vitrification method, which involves ultra-rapid cooling by plunging standard straws into liquid nitrogen vapor, hence avoiding the need for specialized equipment, but requires technical ability to manipulate the oocytes quickly in the highly concentrated cryoprotectant solutions. Murine oocytes that have been vitrified using this technique have resulted in live births. Vitrification using other cryoprotectant mixtures is now a popular clinically accepted method for cryobanking of human oocytes.

Fertility preservation for young adults, adolescents, and children with cancer

Options for fertility preservation (FP) through cryopreservation methods are currently available for young adults, adolescents, and children. Guidelines for FP have been provided by international clinical societies, and emergency procedures aimed at FP have been implemented into clinical practice worldwide. In this article, we review the current data on clinical standards of emergency FP in patients who are facing gonadotoxic effects of cancer treatment, and we also describe the methods that are still under development, usually denoted as experimental. In Sweden, programmes for FP have been established at large university hospitals, thus covering the whole country. The Swedish publicly financed health care covers both assisted reproduction for treatment of infertility and the cryopreservation of gametes or gonadal tissue when there is a medical indication, such as the risk to become infertile due to oncologic treatment; hence the access to FP is ensured for the whole population. At our centre at Karolinska University Hospital in Stockholm, methods for FP have been offered since 1988. In this article, we also review the oncologic indications for FP in our patient cohort of >3000 individuals during the period 1988-2018.

Cryopreservation of human embryos and oocytes for fertility preservation in cancer and non cancer patients: a mini review

The term 'cryopreservation' illustrates the process of freezing cells and storing at very low temperature in liquid nitrogen (-196 °C). Cooling is not a physiological condition for human cells especially due to the high concentration of water in the living matter, whose conversion to ice crystals may be associated with cell death. Human oocytes are particularly sensitive to the freezing process, primarily because of their large size and the presence of the meiotic spindle, which at low temperature can degenerate. In the last decade, the cryopreservation technology has become highly important as an option for fertility preservation (FP) in women with cancer. Anticancer therapy might promote premature ovarian failure and negatively affects the reproductive outcome. Over the years, scientists have proposed different cryopreservation strategies in the effort to maintain the physiological functions of oocytes and embryo. However, despite the first success obtained in the 1980s with frozen oocytes, it was not until recently that a new approach has been proposed: the 'Vitrification' which allowed a breakthrough in this procedure. FP is a major determinant for cancer survivor women in the reproductive age. This article describes the FP options currently available, focusing mainly on oocyte and embryo cryopreservation.

Postponing Pregnancy Through Oocyte Cryopreservation for Social Reasons: Considerations Regarding Clinical Practice and the Socio-Psychological and Bioethical Issues Involved

Oocyte freezing for 'social reasons' refers to women of reproductive age who are aiming to prolong, protect and secure their fertility. The term emerged to describe application of the highly promising technique, namely vitrification on oocytes retrieved through controlled ovarian stimulation (COS) from women intending to preserve their fertility for social reasons. These women opt to cryopreserve their oocytes at a point in their life when they need to postpone childbearing on the grounds of so called 'social' reasons. These reasons may include a highly driven career, absence of an adequate partner, financial instability, or personal reasons that make them feel unprepared for motherhood. This is a sensitive and multifaceted issue that entails medical, bioethical and socio-psychological components. The latest trend and the apparent increase noted on oocyte freezing for 'social reasons' has prompted our team of fertility specialists, embryologists, obstetricians, gynecologists and psychologists to proceed with a thorough, critical and all-inclusive comprehensive analysis. The wide range of findings of this analysis involve concerns of embryology and epigenetics that shape decisions made in the IVF laboratory, issues regarding obstetric and perinatal concerns on the pregnancy concluding from these oocytes and the respective delivery management and neonatal data, to the social and bioethical impact of this trend's application. This literature review refers to matters rising from the moment the 'idea' of this option is 'birthed' in a woman's thoughts, to proceeding and executing it clinically, up until the point of the pediatric follow up of the children born. We aim to shed light to the controversial issue of oocyte freezing, while objectively exhibit all aspects regarding this complex matter, as well as to respectfully approach how could the prospect of our future expectations be shaped from the impact of its application.

Development of ICSI

The first conception outside of the human body that led to the birth of Louise Brown was a tremendous accomplishment, which opened the door to the utilization of assisted reproductive techniques globally. This brought the understanding that accomplishing life in a dish required several steps, the most obvious being the timing and characteristics of fertilization. It soon became obvious in the 1980s that the most disappointing phenomenon was unexpected and complete fertilization failure. Among the approaches that were attempted to treat male factor infertility, ICSI surfaced as the technique that brought the ratio of the gametes to 1:1 and was also able to grant consistent fertilization and a higher pregnancy rate. ICSI has now been implemented for a quarter of a century, proving itself as the ultimate technique utilizing ejaculated spermatozoa independent of the semen parameters and is the sole insemination method to be used with surgically retrieved spermatozoa. There are currently various indications for ICSI that are widely adopted, rendering it the most popular insemination method worldwide. The reliability of ICSI ensures its employment in upcoming techniques involving in vitro spermatogenesis and neogametogenesis.

No. 356-Egg Freezing for Age-Related Fertility Decline

OBJECTIVE

To provide a comprehensive review and evidence based recommendations for Canadian fertility centres that offer social egg freezing.

OUTCOMES

In social egg freezing cycles we evaluated thawed oocyte survival rates, fertilization rates, embryo quality, pregnancy rates, and live birth rates. We also review how these outcomes are impacted by age, ovarian reserve, and the number of eggs cryopreserved. Finally, we discuss the risks of social egg freezing, the alternatives, the critical elements for counselling and informed consent, and future reporting of egg freezing outcome data.

EVIDENCE

Published literature was reviewed through searches of MEDLINE and CINAHL using appropriate vocabulary and using key words ("oocyte cryopreservation," "egg freezing," "egg vitrification," "social egg freezing," and "elective egg freezing"). Results included systematic reviews, randomized controlled trials, controlled clinical trials, and observational studies. Expert opinion based on clinical experience, descriptive studies, or reports of expert committees was also included to discuss aspects of egg freezing not currently rigorously studied.

VALUES

The evidence obtained was reviewed and evaluated by the Clinical Practice Guideline (CPG) Committees of the Canadian Fertility and Andrology Society (CFAS) under the leadership of the principal authors.

BENEFITS, HARMS, AND COSTS

Implementation of this guideline should assist the clinician to develop an optimal approach in providing counselling for egg freezing while minimizing harm and improving patient outcomes during treatment.

VALIDATION

These guidelines have been reviewed and approved by the membership of the CFAS and by the CPG Committees of CFAS and The Society of Obstetricians and Gynaecologists of Canada (SOGC).

SPONSORS

CFAS and SOGC.

RECOMMENDATIONS

Intracytoplasmic sperm injection: state of the art in humans

Among infertile couples, 25% involve both male and female factors, while male factor alone accounts for another 25% due to oligo-, astheno-, teratozoospermia, a combination of the three, or even a complete absence of sperm cells in the ejaculate and can lead to a poor prognosis even with the help of assisted reproductive technology (ART). Intracytoplasmic sperm injection (ICSI) has been with us now for a quarter of a century and in spite of the controversy generated since its inception, it remains in the forefront of the techniques utilized in ART. The development of ICSI in 1992 has drastically decreased the impact of male factor, resulting in millions of pregnancies worldwide for couples who, without ICSI, would have had little chance of having their own biological child. This review focuses on the state of the art of ICSI regarding utility of bioassays that evaluate male factor infertility beyond the standard semen analysis and describes the current application and advances in regard to ICSI, particularly the genetic and epigenetic characteristics of spermatozoa and their impact on reproductive outcome.

Gold Nanorod Induced Warming of Embryos from the Cryogenic State Enhances Viability

Zebrafish embryos can attain a stable cryogenic state by microinjection of cryoprotectants followed by rapid cooling, but the massive size of the embryo has consistently led to failure during the convective warming process. Here we address this zebrafish cryopreservation problem by using gold nanorods (GNRs) to assist in the warming process. Specifically, we microinjected the cryoprotectant propylene glycol into zebrafish embryos along with GNRs, and the samples were cooled at a rate of 90 000 °C/min in liquid nitrogen. We demonstrated the ability to unfreeze the zebrafish rapidly (1.4 × 10⁷ °C/min) by irradiating the sample with a 1064 nm laser pulse for 1 ms due to the excitation of GNRs. This rapid warming process led to the outrunning of ice formation, which can damage the embryos. The results from 14 trials (n = 223) demonstrated viable embryos with consistent structure at 1 h (31%) and continuing development at 3 h (17%) and movement at 24 h (10%) postwarming. This compares starkly with 0% viability, structure, or movement at all time points in convectively warmed controls (n = 50, p < 0.001, ANOVA). Our nanoparticle-based warming process could be applied to the storage of fish, and with proper modification, can potentially be used for other vertebrate embryos.

Recent advances in the field of ovarian tissue cryopreservation and opportunities for research

PURPOSE

The purpose of this study was to summarize the latest advances and successes in the field of ovarian tissue cryopreservation while identifying gaps in current knowledge that suggest opportunities for future research.

METHODS

A systematic review was performed according to PRISMA guidelines for all relevant full-text articles in PubMed published in English that reviewed or studied historical or current advancements in ovarian tissue cryopreservation and auto-transplantation techniques.

RESULTS

Ovarian tissue auto-transplantation in post-pubertal women is capable of restoring fertility with over 80 live births currently reported with a corresponding pregnancy rate of 23 to 37%. The recently reported successes of live births from transplants, both in orthotopic and heterotopic locations, as well as the emerging methods of in vitro maturation (IVM), in vitro culture of primordial follicles, and possibility of in vitro activation (IVA) suggest new fertility options for many women and girls. Vitrification, as an ovarian tissue cryopreservation technique, has also demonstrated successful live births and may be a more cost-effective method to freezing with less tissue injury. Further, transplantation via the artificial ovary with an extracellular tissue matrix (ECTM) scaffolding as well as the effects of sphingosine-1-phosphate (SIP) and fibrin modified with heparin-binding peptide (HBP), heparin, and a vascular endothelial growth factor (VEGF) have demonstrated important advancements in fertility preservation. As a fertility preservation method, ovarian tissue cryopreservation and auto-transplantation are currently considered experimental, but future research may pave the way for these modalities to become a standard of care for women facing the prospect of sterility from ovarian damage.

Chapter 3 Current Challenges in Immature Oocyte Cryopreservation

Current freezing technology, especially the vitrification method, has markedly improved oocyte survival rate after warming, and the pregnancy rate is comparable to that achieved with fresh oocytes. However, most groups report using oocytes matured in vivo for vitrification. Although immature oocytes can be vitrified successfully, clinical outcomes do not reach that of vitrification of matured oocytes. The current literature suggests that oocytes should be vitrified at mature metaphase II (M-II) stage following IVM rather than at the immature germinal vesicle (GV) stage, because the potential for oocyte maturation is reduced when vitrification is performed on immature oocytes at the GV stage.

Chapter 1 Historical Background on Gamete and Embryo Cryopreservation

This chapter describes the development of the science of cryopreservation of gametes and embryos of various species including human. It attempts to record in brief the main contributions of workers in their attempts to cryopreserve gametes and embryos. The initial difficulties faced and subsequent developments and triumphs leading to present-day state of the art are given in a concise manner. The main players and their contributions are mentioned and the authors' aim is to do justice to them. This work also attempts to ensure that credit is correctly attributed for significant advances in gamete and embryo cryopreservation. In general this chapter has tried to describe the historical development of the science of cryopreservation of gametes and embryos as accurately as possible without bias or partiality.

Evolution of human oocyte cryopreservation: slow freezing versus vitrification

PURPOSE OF REVIEW

The purpose is to determine the efficiency and efficacy of oocyte cryopreservation by slow freezing versus vitrification, recent data collected from the Italian National Assisted Reproductive Technology Register during the period 2009-2014 will be presented and reviewed. The data on oocyte cryopreservation were also compared with the results obtained with embryo cryopreservation and relative IVF with fresh oocytes.

RECENT FINDINGS

During the period 2009-2014 preservation of oocytes by vitrification had a significantly higher survival rate, implantation, and pregnancy rate than slow freezing; however, there are still large variations in success rates among centers in relation to the number of procedures performed.

SUMMARY

Vitrification has now become the method of choice for oocyte cryopreservation because of better results than slow freezing, but still requires a more standardized utilization. The transfer of fresh or cryopreserved embryo still shows a statistically significant better performance than transfers with embryos obtained with cryopreserved oocytes. Only in a few centers with much experience in cryopreservation are the results between transfers of frozen embryos or embryos obtained from oocyte cryopreservation comparable.

The state of "freeze-for-all" in human ARTs

The recent development of vitrification technologies and the good outcomes obtained in assisted reproduction technologies have supported new indications for freezing and segmentation of treatment. Beyond OHSS prevention and avoidance of embryo transfers in the setting of an adverse endocrinological profile or endometrial cavity, we have witnessed a trend to shift fresh embryo transfers to frozen embryo transfers in many programs. We critically review the available evidence and suggest that freeze-all is not "for all," but should be individualized.

Fertility Preservation: A Key Survivorship Issue for Young Women with Cancer

Fertility preservation in the young cancer survivor is recognized as a key survivorship issue by the American Society of Clinical Oncology and the American Society of Reproductive Medicine. Thus, health-care providers should inform women about the effects of cancer therapy on fertility and should discuss the different fertility preservation options available. It is also recommended to refer women expeditiously to a fertility specialist in order to improve counseling. Women’s age, diagnosis, presence of male partner, time available, and preferences regarding use of donor sperm influence the selection of the appropriate fertility preservation option. Embryo and oocyte cryopreservation are the standard techniques used while ovarian tissue cryopreservation is new, yet promising. Despite the importance of fertility preservation for cancer survivors’ quality of life, there are still communication and financial barriers faced by women who wish to pursue fertility preservation.

ART results with frozen oocytes: data from the Italian ART registry (2005-2013)

PURPOSE

This study is a retrospective collection of aggregated data from all the Italian ART centers reporting to the Italian National Register from cycles started between January 2005 and December 2013.

METHODS

Data from both slow freezing (SF) and vitrification (V) were assessed for the period 2007-2013, while during the years 2005-2006 cryopreservation was exclusively performed by SF.

RESULTS

In the study period, a total of 2,526,024 oocytes were retrieved (from 378,543 retrievals), of which 1,346,061 (53.3 %) were inseminated in fresh cycles and 214,481 (8.5 %) were cryopreserved. Cryopreserved oocytes were used in 24,173 cycles yielding 19,453 transfer cycles (80.5 % of the thawing/warming cycles) and 3043 clinical pregnancies (15.6 % per transfer). A significant difference in implantation (8.7 vs 12.9 % OR 1.30 CI 1.20-1.40) and pregnancy rates per transfer (12.2 vs 14.9 % OR 1.34 CI 1.23-1.46) was found between SF and V. Complete outcome data was available for 2708 pregnancies (89.8 %), leading to 1882 deliveries and 2152 live births. Neonatal major congenital anomalies were 0.9 % (20/2152).

CONCLUSIONS

A wide variation in pregnancy rates were found among different centers and lower rates were reported in donor cycles and in centers with more experience.

Improvement of the vitrification method suppressing the disturbance of meiotic spindle and chromosome systems in mature oocytes

Vitrification method is widely used in oocyte cryopreservation for IVF but the birth rates are lower than that of the fresh oocyte. One of the known main reasons is structural instability of meiotic spindle and chromosome systems of mature oocyte. To get the best way for keeping competence of matured oocytes, we studied the best conditions for vitrification focused on equilibration times. The mature oocytes were underwent vitrification with current popular method and analyzed the survival rates, microtubule stability and DNA integrity. The survival rates of recovered oocyte are almost same between groups and are more than 93%. The structural configuration of meiotic spindle was well kept in 10 min equilibration group and the stability rate was almost same with that of control. The chromosomal breakdown was observed in all experimental groups, but the chromosomal stability was higher in 10 min equilibration group than the other groups. The 10 min equilibration group showed best condition compared with the other groups. Based on these results, the equilibration time is one of the key factors in successful keeping for competence of mature oocyte. Although, more fine analysis about the effects of physical stress on oocyte during vitrification is needed to define the optimal condition, it is suggested that the optimal equilibration time to get competent oocyte in mouse is 10 min. Information acquired this study may provide insight into intracellular structural events occurring in human oocytes after vitrification and application for cryopreservation of human oocyte.

Oocyte vitrification modifies nucleolar remodeling and zygote kinetics-a sibling study

Purpose

Oocyte vitrification does not affect embryo quality after oocyte warming, making this method effective in the preservation of female fertility. Morphokinetic parameters can be used to predict the competence of an embryo produced from fresh oocytes. Our aim was to study the effect of oocyte vitrification on zygote-embryo kinetics (pl).

Methods

The embryo-kinetics of fresh and sibling vitrified/warmed oocytes were compared to determine the consequences of oocyte preservation on the timing of embryo development. A 44-hours time-lapse analysis, from the time of ICSI (t0), of 179 fertilized fresh oocytes was compared to 168 fertilized sibling vitrified/warmed oocytes.

Results

Oocyte vitrification accelerated pronuclear disappearance, one-cell stage timing and modified nucleoli activity by increasing their number and decreasing their diameter at the zygote stage. In contrast, embryo kinetics during cleavage were similar to those observed for fresh sibling oocytes based on the parameters examined in this study.

Conclusions

At the zygote stage, oocyte vitrification induces changes in pronuclei stability, probably due to pronuclei envelop instability as well as modifications in nucleoli functionality. Therefore, the predictive morphokinetic parameters on embryo competence found from fresh oocytes must be revised when applied on embryos from vitrified/warmed oocytes.

General principles of cryopreservation

Cryopreservation quickly became a cornerstone technology in assisted reproduction because the banking of gametes, embryos, and gonadal tissues has increased the effectiveness of assisted reproductive technology cycles for infertility treatment as well as fertility preservation for patients at risk of premature sterilization. Cryopreservation protocols, both slow/equilibrium cooling and vitrification methods, have evolved empirically and still depend heavily on operator skill, but further automation promises to improve reproducibility and uniformity of results.

Fine morphological assessment of quality of human mature oocytes after slow freezing or vitrification with a closed device: a comparative analysis

BACKGROUND

Human mature oocytes are very susceptible to cryodamage. Several reports demonstrated that vitrification might preserve oocyte better than slow freezing. However, this is still controversial. Thus, larger clinical, biological and experimental trials to confirm this concept are necessary. The aim of the study was to evaluate and compare fine morphological features in human mature oocytes cryopreserved with either slow freezing or vitrification.

METHODS

We used 47 supernumerary human mature (metaphase II) oocytes donated by consenting patients, aged 27-32 years, enrolled in an IVF program. Thirtyfive oocytes were cryopreserved using slow freezing with 1.5 M propanediol +0.2 M sucrose concentration (20 oocytes) or a closed vitrification system (CryoTip Irvine Scientific CA) (15 oocytes). Twelve fresh oocytes were used as controls. All samples were prepared for light and transmission electron microscopy evaluation.

RESULTS

Control, slow frozen/thawed and vitrified/warmed oocytes (CO, SFO and VO, respectively) were rounded, 90-100 μm in diameter, with normal ooplasm showing uniform distribution of organelles. Mitochondria-smooth endoplasmic reticulum (M-SER) aggregates and small mitochondria-vesicle (MV) complexes were the most numerous structures found in all CO, SFO and VO cultured for 3-4 hours. M-SER aggregates decreased, and large MV complexes increased in those SFO and VO maintained in culture for a prolonged period of time (8-9 hours). A slight to moderate vacuolization was present in the cytoplasm of SFO. Only a slight vacuolization was present in VO, whereas vacuoles were almost completely absent in CO. Amount and density of cortical granules (CG) appeared abnormally reduced in SFO and VO, irrespective of the protocol applied.

CONCLUSIONS

Even though, both slow freezing and vitrification ensured a good overall preservation of the oocyte, we found that: 1) prolonged culture activates an intracellular membrane "recycling" that causes the abnormal transformation of the membranes of the small MV complexes and of SER into larger rounded vesicles; 2) vacuolization appears as a recurrent form of cell damage during slow freezing and, at a lesser extent, during vitrification using a closed device; 3) premature CG exocytosis was present in both SFO and VO and may cause zona pellucida hardening.

Chemotherapy for gynaecological malignancies and fertility preservation

Infertility is an increasingly important issue for patients surviving cancer. Significant improvements in cancer management have led to greater numbers of patients living healthy and fulfilling lives for many years after a diagnosis of cancer, and the ability to bear children is a major component of well-being. Infertility is particularly challenging in gynaecological cancer, where multiple treatment modalities are often employed. Surgery may involve the removal of reproductive organs and subsequent chemotherapy may also lead to infertility. Mitigation of this through the use of cryopreservation of embryos, oocytes or ovarian tissue before chemotherapy may enable subsequent pregnancy in the patient or a surrogate mother. Suppression of ovarian function during chemotherapy is less well established, but promises a reduction in infertility without the risks associated with surgery. Similarly, evolving chemotherapy regimens with replacement of alkylating agents will reduce the incidence of infertility. With a combination of these techniques, an increasing proportion of patients may be able to conceive after completion of treatment, and there is no evidence of an increase in congenital abnormalities. This review discusses chemotherapy-induced infertility, interventions and success rates, and demonstrates that individualisation of management is required for optimum outcome.

Recent progress in cryopreservation of bovine oocytes

Principle of oocyte cryoinjury is first overviewed and then research history of cryopreservation using bovine oocytes is summarized for the last two decades with a few special references to recent progresses. Various types of cryodevices have been developed to accelerate the cooling rate and applied to the oocytes from large domestic species enriched with cytoplasmic lipid droplets. Two recent approaches include the qualitative improvement of IVM oocytes prior to the vitrification and the short-term recovery culture of vitrified-warmed oocytes prior to the subsequent IVF. Supplementation of L-carnitine to IVM medium of bovine oocytes has been reported to reduce the amount of cytoplasmic lipid droplets and improve the cryotolerance of the oocytes, but it is still controversial whether the positive effect of L-carnitine is reproducible. Incidence of multiple aster formation, a possible cause for low developmental potential of vitrified-warmed bovine oocytes, was inhibited by a short-term culture of the postwarm oocytes in the presence of Rho-associated coiled-coil kinase (ROCK) inhibitor. Use of an antioxidant α-tocopherol, instead of the ROCK inhibitor, also supported the revivability of the postwarm bovine oocytes. Further improvements of the vitrification procedure, combined with pre- and postvitrification chemical treatment, would overcome the high sensitivity of bovine oocytes to cryopreservation.

Oocyte vitrification: advances, progress and future goals

BACKGROUND

Recent advances in vitrification technology have markedly improved the efficacy of oocyte cryopreservation in terms of oocyte survival and pregnancy, as well as live birth rates. However, there still remains room for improvement in terms of vitrification techniques.

OBJECTIVE

The remaining challenges include the development of a less cytotoxic vitrification solution and of a safe vitrification device in order to have vitrification techniques considered as a standard clinical laboratory procedure.

METHODS

A systematic electronic literature search strategy has been conducted using PubMed (Medline) databases with the use of the following key words: oocyte, vitrification, cryoprotectant, preservation, pregnancy, and live birth. A list of published papers focused on the improvement of vitrification techniques to have the vitrification protocol standardized have been evaluated in full text for this review. Only key references were cited.

CONCLUSIONS

Vitrification technology has made significant advancements and holds great promise, but many issues remains to be addressed before it becomes a standardized procedure in clinical laboratories such as the fact that oocyte vitrification may not require a high concentration of cryoprotectant in the vitrification solution when it has a suitable cooling and warming rate. There is also no consistent evidence that indicates the absence of risk to the vitrified oocytes when they are stored for a prolonged period of time in direct-contact with liquid nitrogen. The long-term development of infants born as a result of this technology equally remains to be evaluated.

The effect of minimal concentration of ethylene glycol (EG) combined with polyvinylpyrrolidone (PVP) on mouse oocyte survival and subsequent embryonic development following vitrification

PURPOSE

Vitrification techniques employ a relatively high concentration of cryoprotectant in vitrification solutions. Exposure of oocytes to high concentrations of cryoprotectant is known to damage the oocytes via both cytotoxic and osmotic effects. Therefore, the key to successful vitrification of oocytes is to strike a balance between the usage of minimal concentration of cryoprotectant without compromising their cryoprotective actions.

METHODS

The minimal concentration of ethylene glycol (EG) on mouse oocyte survival and subsequent embryonic development was evaluated following vitrification-warming and parthenogenetic activation. Polyvinylpyrrolidone (PVP) combined with EG on mouse oocyte survival and subsequent embryonic development as well as morphology of the spindle and chromosome alignment were also evaluated. Vitrification system was adapted with JY Straw and the cooling rate was approximately 442-500 °C/min. In contrast, the warming rate was approximately 2,210-2,652 °C/min.

RESULTS

Survival rate of oocytes increased significantly when 15 % EG was combined with 2 % PVP in vitrification solution (VS). The effect of combination of EG and PVP was not significant when the concentration of EG was 20 % and higher. Although there were no significant differences in embryonic development, the percentage of abnormal spindle and chromosome alignment was significantly higher in the oocytes without 2 % PVP in VS.

CONCLUSIONS

Our data provide a proof of principle for oocyte vitrification that may not require a high concentration of cryoprotectant. There are synergic effects of EG combined with PVP for oocyte vitrification, which may provide important information to the field in developing less cytotoxic VS.

Optimization of cryoprotectant loading into murine and human oocytes

Loading of cryoprotectants into oocytes is an important step of the cryopreservation process, in which the cells are exposed to potentially damaging osmotic stresses and chemical toxicity. Thus, we investigated the use of physics-based mathematical optimization to guide design of cryoprotectant loading methods for mouse and human oocytes. We first examined loading of 1.5 M dimethyl sulfoxide (Me(2)SO) into mouse oocytes at 23°C. Conventional one-step loading resulted in rates of fertilization (34%) and embryonic development (60%) that were significantly lower than those of untreated controls (95% and 94%, respectively). In contrast, the mathematically optimized two-step method yielded much higher rates of fertilization (85%) and development (87%). To examine the causes for oocyte damage, we performed experiments to separate the effects of cell shrinkage and Me(2)SO exposure time, revealing that neither shrinkage nor Me(2)SO exposure single-handedly impairs the fertilization and development rates. Thus, damage during one-step Me(2)SO addition appears to result from interactions between the effects of Me(2)SO toxicity and osmotic stress. We also investigated Me(2)SO loading into mouse oocytes at 30°C. At this temperature, fertilization rates were again lower after one-step loading (8%) in comparison to mathematically optimized two-step loading (86%) and untreated controls (96%). Furthermore, our computer algorithm generated an effective strategy for reducing Me(2)SO exposure time, using hypotonic diluents for cryoprotectant solutions. With this technique, 1.5 M Me(2)SO was successfully loaded in only 2.5 min, with 92% fertilizability. Based on these promising results, we propose new methods to load cryoprotectants into human oocytes, designed using our mathematical optimization approach.

The current challenges to efficient immature oocyte cryopreservation

Oocyte cryopreservation represents an important tool for assisted reproductive technology. It offers the opportunity to preserve fertility in women at risk of loss of the ovarian function for various pathologies. It also represents a treatment alternative for couples that cannot benefit from embryo cryopreservation because of moral, religious, or legal constrains. On the other hand, in vitro oocyte maturation has a range of applications. It can be applied in patients with a contraindication to ovarian stimulation to prevent ovarian hyperstimulation syndrome or to eliminate the risk of stimulation of hormone-sensitive tumours in cancer patients. However, while mature oocyte cryopreservation has found wide-spread application and oocyte in vitro maturation has a place for the treatment of specific clinical conditions, data on the efficiency of freezing of immature or in vitro matured oocytes are poorer. In this review we will focus on the combination of oocyte in vitro maturation with oocyte cryopreservation with particular emphasis on the biological implications of the cryopreservation of immature or in vitro matured oocytes. The two cryopreservation approaches, slow freezing and vitrification, will be discussed in relation to possible cryodamage occurring to subcellular structures of the oocyte and the functional interaction between oocyte and cumulus cells.