Report of four donor-recipient oocyte cryopreservation cycles resulting in high pregnancy and implantation rates

Women's reproductive choice and (elective) egg freezing: is an extension of the storage limit missing a bigger issue?

Egg freezing can allow women to preserve their eggs to avoid age-related infertility. The UK's recent extension of elective egg freezing storage has been welcomed as a way of enhancing the reproductive choices of young women who wish to delay having children. In this paper, I explore the issue of enhancing women's reproductive choices, questioning whether there is a more significant aspect overlooked in egg freezing. While increasing storage limits expands reproductive choices for some women, focus on this extension alone, I argue, misses a fundamental issue with egg preservation that often remains ignored; the importance of effective information on egg freezing and the effect this has on women's reproductive choices. Ultimately, I highlight the crucial role of balanced information in enhancing women's choices regarding egg freezing and argue that focusing on extending and increasing provision may obscure this real opportunity to empower women and their authentic reproductive choices.

Cryopreservation of oocytes and embryos for fertility preservation

Background: In recent years, the demand for fertility preservation for both oncologic and nononcologic reasons, as well as for personal reasons, has increased dramatically.Current Concepts: Currently, embryo and oocyte cryopreservation after ovarian stimulation are the mainstays of fertility preservation treatment in women. Embryo cryopreservation is an established and the most successful method of fertility preservation when sufficient time (approximately 2 weeks) is available to perform ovarian stimulation. Recent advances in freezing techniques (vitrification) have significantly improved the outcomes from oocyte cryopreservation that are comparable with those from embryo cryopreservation.Discussion and Conclusion: This review focuses on the indications for the two techniques of fertility preservation and their results. For women to receive timely opportunities to preserve fertility, it is necessary to raise awareness among all medical departments and the public.

Optimizing human oocyte cryopreservation for fertility preservation patients: should we mature then freeze or freeze then mature?

OBJECTIVE

To evaluate the maturation and post-thaw survival rates of immature oocytes to determine whether in vitro maturation (IVM) should be attempted prior to or after cryopreservation.

DESIGN

Nonrandomized observational study.

SETTING

Private academic and clinical reproductive center.

PATIENT(S)

Patients (n = 71) who donated immature unusable oocytes after vaginal oocyte retrieval (VOR) after undergoing controlled ovarian hyperstimulation using a standard GnRH antagonist protocol.

INTERVENTION(S)

Germinal vesicle (GV), metaphase I (MI), and metaphase II (MII) oocytes (n = 175) were obtained from consenting IVF patients for fresh IVM, post-thaw IVM, or control group. In the fresh IVM group, GV- and MI- stage oocytes (n = 69) were cultured for 24 hours, matured in vitro (IVM-MII), cryopreserved, thawed, and evaluated for survival. In the post-thaw IVM group, GV- and MI- stage oocytes (n = 27) were frozen on day 0, thawed, evaluated for survival, and cultured for 24-hour IVM. MII donor oocytes (n = 79) were cryopreserved and thawed as a control.

MAIN OUTCOME MEASURE(S)

Survival postfreeze and oocyte development to the MII stage was analyzed using a χ(2) analysis.

RESULT(S)

Fresh IVM had a significantly higher maturation rate than post-thaw IVM.

CONCLUSION(S)

Oocyte cryopreservation is important for patients at risk of ovarian cancer, elective fertility preservation, and, potentially, for ovum donation. The superior maturation rate of GV and MI oocytes in the fresh versus post-thaw groups provides strong evidence for maturing oocytes to the MII stage before cryopreservation.

A critical appraisal of cryopreservation (slow cooling versus vitrification) of human oocytes and embryos

BACKGROUND

Vitrification is now a commonly applied technique for cryopreservation in assisted reproductive technology (ART) replacing, in many cases, conventional slow cooling methodology. This review examines evidence relevant to comparison of the two approaches applied to human oocytes and embryos at different developmental stages.

METHODS

Critical review of the published literature using PubMed with particular emphasis on studies which include data on survival and implantation rates, data from fresh control groups and evaluation of the two approaches in a single setting.

RESULTS

Slow cooling is associated with lower survival rates and compromised development relative to vitrification when applied to metaphase II (MII) oocytes, although the vitrification results have predominantly been obtained using direct contact with liquid nitrogen and there is some evidence that optimal protocols for slow cooling of MII oocytes are yet to be established. There are no prospective randomized controlled trials (RCTs) which support the use of either technique with pronuclear oocytes although vitrification has become the method of choice. Optimal slow cooling, using modifications of traditional methodology, and vitrification can result in high survival rates of early embryos, which implant at the same rate as equivalent fresh counterparts. Many studies report high survival and implantation rates following vitrification of blastocysts. Although slow cooling of blastocysts has been reported to be inferior in some studies, others comparing the two approaches in the same clinical setting have demonstrated comparable results. The variation in the extent of embryo selection applied in studies can lead to apparent differences in clinical efficiency, which may not be significant if expressed on a 'per oocyte used' basis.

CONCLUSIONS

Available evidence suggests that vitrification is the current method of choice when cryopreserving MII oocytes. Early cleavage stage embryos can be cryopreserved with equal success using slow cooling and vitrification. Successful blastocyst cryopreservation may be more consistently achieved with vitrification but optimal slow cooling can produce similar results. There are key limitations associated with the available evidence base, including a paucity of RCTs, limited reporting of live birth outcomes and limited reporting of detail which would allow assessment of the impact of differences in female age. While vitrification has a clear role in ART, we support continued research to establish optimal slow cooling methods which may assist in alleviating concerns over safety issues, such as storage, transport and the use of very high cryoprotectant concentrations.

Oocyte cryostorage to preserve fertility in oncological patients

Thanks to the progress in oncostatic treatments, young women affected by cancer have a fairly good chance of surviving the disease and leading a normal post-cancer life. Quite often, however, polychemiotherapy and/or radiotherapy can induce ovarian damage and significantly reduce the content of follicles and oocytes inside the ovary, thus predisposing the patient to menstrual disorders, infertility, and precocious menopause. Several techniques have been proposed to preserve fertility in these patients; among them oocyte collection and cryopreservation prior to the oncostatic treatment has been widely applied in the last decade. The proper indications, the permitting conditions, the available hormonal stimulation protocols, as well as the effectiveness and limits of this option will be discussed herein, with a comprehensive and up-to-date review of the two techniques commonly used to cryostore oocytes, the slow-freezing technique and the vitrification technique.

Implantation rates of embryos generated from slow cooled human oocytes from young women are comparable to those of fresh and frozen embryos from the same age group

Previous reports of slow cooling of human mature oocytes have shown a reduced clinical efficiency relative to fresh oocytes. This study reports that equivalent fertilization and implantation rates to those obtained using fresh oocytes and cryopreserved embryos can be achieved with human mature oocytes dehydrated in 1.5 M propanediol and 0.2 M sucrose at 37°C and cryopreserved using slow cooling rates.

Prevention of ovarian damage and infertility in young female cancer patients awaiting chemotherapy--clinical approach and unsolved issues

Great advances in the oncological therapy of childhood and adolescent cancer patients lead to an increase of young cancer survivors with a normal expectancy of life. The aggressive chemotherapy and/or radiation often compromises endocrine function with consecutive menopausal symptoms and sterility. Recently, new approaches were developed to preserve fertility with different methods to restore the ovarian function. The present review gives an overview of the current possibilities, which may be offered to these young cancer patients, as well as the chances of success and risks and the unsolved issues in special situations.

Fertility preservation in women--a practical guide to preservation techniques and therapeutic strategies in breast cancer, Hodgkin's lymphoma and borderline ovarian tumours by the fertility preservation network FertiPROTEKT

PURPOSE

Fertility preservation methods are playing an increasing role in women up to the age of 40 years because of rising survival rates in those affected by cancer. However, balanced practical recommendations concerning all relevant fertility preservation, to support doctors in counselling and treating patients, are still rare.

METHODS

These recommendations were prepared by the network FertiPROTEKT ( http://www.fertiprotect.eu ), a collaboration of around 70 centres in Germany, Switzerland and Austria. The recommendations were developed by specialists in reproductive medicine, reproductive biology and oncology, which gave a comprehensive overview of all named techniques as well as their benefits and risks. Furthermore, practice-orientated recommendations for the individual use of fertility preservation methods for various indications such as breast cancer, Hodgkin's lymphoma and borderline ovarian tumours are given.

RESULTS

Various options such as ovarian stimulation and cryopreservation of unfertilised or fertilised oocytes, cryopreservation and transplantation of ovarian tissue, GnRH-agonist administration and transposition of the ovaries can be offered. All the techniques can be performed alone or in combination within a maximum of 2 weeks with low risk and different success rates.

CONCLUSIONS

Fertility preservation in women has become an option with realistic chances to become pregnant after cytotoxic therapies. The information provided allows a well balanced and realistic counselling and treatment.

Efficient derivation of embryonic stem cells from nuclear transfer and parthenogenetic embryos derived from cryopreserved oocytes

Deriving histocompatible embryonic stem (ES) cells by somatic cell nuclear transfer (SCNT) and parthenogenetic activation (PA) requires fresh oocytes, which prevents their applications in humans. Here, we evaluated the efficiency of deriving ES cells from mature metaphase II (MII) and immature metaphase I (MI) vitrified oocytes, by PA or SCNT, in a mouse model. We successfully generated ES cell lines from PA (MII and MI) and SCNT (MII and MI) blastocysts. These cell lines expressed genes and antigens characteristic of pluripotent ES cells and produced full-term pups upon tetraploid embryo complementation. This study established an animal model for efficient generation of patient-specific ES cell lines using cryopreserved oocytes. This is a major step forward in the application of therapeutic cloning and parthenogenetic technology in human regenerative medicine and will serve as an important alternative to the iPS cell technology in countries/regions where these technologies are permitted.

ASRM Practice Committee response to Rybak and Lieman: elective self-donation of oocytes

Oocyte cryopreservation has great promise for applications in oocyte donation and fertility preservation and for decreasing the number of unused cryopreserved embryos. The Practice Committee has and will continue to review the published medical literature relating to oocyte cryopreservation at regular intervals and is prepared to reconsider its position when evidence warrants.

The mammalian ovary from genesis to revelation

Two major functions of the mammalian ovary are the production of germ cells (oocytes), which allow continuation of the species, and the generation of bioactive molecules, primarily steroids (mainly estrogens and progestins) and peptide growth factors, which are critical for ovarian function, regulation of the hypothalamic-pituitary-ovarian axis, and development of secondary sex characteristics. The female germline is created during embryogenesis when the precursors of primordial germ cells differentiate from somatic lineages of the embryo and take a unique route to reach the urogenital ridge. This undifferentiated gonad will differentiate along a female pathway, and the newly formed oocytes will proliferate and subsequently enter meiosis. At this point, the oocyte has two alternative fates: die, a common destiny of millions of oocytes, or be fertilized, a fate of at most approximately 100 oocytes, depending on the species. At every step from germline development and ovary formation to oogenesis and ovarian development and differentiation, there are coordinated interactions of hundreds of proteins and small RNAs. These studies have helped reproductive biologists to understand not only the normal functioning of the ovary but also the pathophysiology and genetics of diseases such as infertility and ovarian cancer. Over the last two decades, parallel progress has been made in the assisted reproductive technology clinic including better hormonal preparations, prenatal genetic testing, and optimal oocyte and embryo analysis and cryopreservation. Clearly, we have learned much about the mammalian ovary and manipulating its most important cargo, the oocyte, since the birth of Louise Brown over 30 yr ago.

Over 900 oocyte cryopreservation babies born with no apparent increase in congenital anomalies

Over the past decade, the number of reported live births resulting from oocyte cryopreservation has rapidly increased. To appreciate the true number of children born, verified live births were tabulated and assessed. A literature search was performed; authors were then contacted to verify birth outcomes and provide updates. A database including all verified live born infants was constructed. A total of 58 reports (1986-2008) were reviewed, which included 609 live born babies (308 from slow freezing, 289 from vitrification and 12 from both methods). Additionally, 327 other live births were verified. Of the total 936 live borns, 1.3% (12) were noted to have birth anomalies: three ventricular septal defects, one choanal and one biliary atresia, one Rubinstein-Taybi syndrome, one Arnold-Chiari syndrome, one cleft palate, three clubfoot and one skin haemangioma. Compared with congenital anomalies occurring in naturally conceived infants, no difference was noted. With more live born data accumulating, this procedure may become mainstream as a fertility preservation option, particularly for women diagnosed with malignancy requiring cytotoxic therapy. A registry would help to assure the safest, most expeditious development of this technology.

Factors affecting thawed oocyte viability suggest a customized policy of embryo transfer

OBJECTIVE

To identify factors that might affect the clinical outcome of oocyte slow freezing.

DESIGN

Retrospective study.

SETTING

Reproductive Medicine Unit, Italian Society for the Study of Reproductive Medicine, Bologna, Italy.

PATIENT(S)

Patients with spare metaphase II cryopreserved oocytes performing 371 thawing cycles.

INTERVENTION(S)

Oocytes were cryopreserved by slow freezing<40 hours after hCG administration (group A) and >or=40 hours after hCG administration (group B). Thawed oocytes were inseminated by intracytoplasmic sperm injection.

MAIN OUTCOME MEASURE(S)

Clinical pregnancy, implantation, abortion, and delivery rates.

RESULT(S)

Clinical pregnancy rate per thawed cycle (PR) and implantation rate (IR) were significantly higher in group A compared with group B both in young (PR: 25% vs. 9.6%; IR: 18.9% vs. 8.8%) and in older patients (PR: 25% vs. 10.1%; IR: 17.5% vs. 6.7%). In the young patient subgroup, clinical pregnancy and implantation rates with three transferred embryos were higher in group A vs. group B (PR: 72.7% vs. 25%, and IR: 36.4% vs. 12.5%, respectively). This difference was not found in the subgroup of older patients.

CONCLUSION(S)

The timing at which oocyte cryopreservation is performed and the number of transferred embryos play a key role in the clinical outcome. The suggested cut-off time for cryopreservation is between 39 and 40 hours after hCG administration.

Bibliography. Current world literature

This bibliography is compiled by clinicians from the journals listed at the end of this publication. It is based on literature entered into our database between 1 February 2008 and 31 January 2009 (articles are generally added to the database about two and a half months after publication). In addition, the bibliography contains every paper annotated by reviewers; these references were obtained from a variety of bibliographic databases and published between the beginning of the review period and the time of going to press. The bibliography has been grouped into topics that relate to the reviews in this issue.

Nuclear transfer and oocyte cryopreservation

Somatic cells can be reprogrammed to a totipotent state through nuclear transfer or cloning, because it has been demonstrated that the oocyte has the ability to reprogramme an adult nucleus into an embryonic state that can initiate the development of a new organism. Therapeutic cloning, whereby nuclear transfer is used to derive patient-specific embryonic stem cells, embraces an entire new opportunity for regenerative medicine. However, a key obstacle for human therapeutic cloning is that the source of fresh human oocytes is extremely limited. In the present review, we propose prospective sources of human oocytes by using oocyte cryopreservation, such as an oocyte bank and immature oocytes. We also address some potential issues associated with nuclear transfer when using cryopreserved oocytes. In the future, if the efficacy and efficiency of cryopreserved oocytes are comparable to those of fresh oocytes in human therapeutic cloning, the use of cryopreserved oocytes would be invaluable and generate a great impact to regenerative medicine.

Human oocyte cryopreservation in infertility and oncology

PURPOSE OF REVIEW

To evaluate the present state of research and clinical application of human oocyte cryopreservation in infertility and oncology.

RECENT FINDINGS

Recent literature documents have an increasing interest in cryopreserving human eggs. A number of studies report on different freezing protocols and various types of clinical application. Increasing attention is paid to vitrification as an alternative to slow cooling for oocyte cryopreservation. Several studies cover the modification of meiotic spindle during cryopreservation in order to assess the less damaging cryopreservation system. The first births with cryopreserved oocytes in cancer patients are reported.

SUMMARY

Egg freezing may circumvent the ethical and legal concerns regarding embryo cryopreservation, increase assisted reproduction flexibility and be a concrete option to save fertility in women with cancer. Recently, egg survival and pregnancy rates improved, with the birth of more than 500 children. The birth rate per thawed oocyte is around 5-6%. As regards safety, data on birth defects seems to be reassuring so far but must be monitored by an international registry. Comparative studies between slow freezing and vitrification in the same patient population are needed to elucidate pros and cons of each technique.

Clinical evaluation of the efficiency of an oocyte donation program using egg cryo-banking

OBJECTIVE

To evaluate the efficiency of oocyte donation cycles using egg "cryo-banking."

DESIGN

Study conditions for vitrified/warmed oocytes for 20 non-autologous recipients (from 10 donors) were set prospectively, and outcomes of it were later compared retrospectively to nine fresh donations cycles.

SETTING

Private assisted reproductive technology program.

PATIENT(S)

Ten donors and 20 infertile recipients.

INTERVENTION(S)

Oocytes were vitrified 3 to 4 hours after collection and cryo-stored. Intracytoplasmic sperm injection was performed 3 hours after warming, and embryos were in vitro cultured for 5 days. Two or three blastocysts were transferred per patient.

MAIN OUTCOME MEASURE(S)

Oocyte survival, fertilization, development, clinical pregnancy, and implantation rates.

RESULT(S)

A total of 153 oocytes were warmed and 134 survived. A total of 117 fertilized and 68% developed to blastocyst stage. A total of 47 embryos were transferred (2.35 embryos per recipient) and 26 implanted. Fifteen patients achieved ongoing pregnancies initially, and two additional pregnancies were obtained after transfer of supernumerary vitrified/warmed embryos. Nine of the 10 donors from the current study had previous fresh donations cycles from where seven clinical pregnancies were established in nine recipients, providing the base for comparison.

CONCLUSION(S)

Oocyte donation using vitrified/warmed oocytes can provide high pregnancy and implantation rates, and thus can be considered as efficient treatment procedure with additional benefits to recipients.

Human oocyte and ovarian tissue cryopreservation and its application

PURPOSE

To review the recent progress in human oocyte and ovarian tissue cryopreservation, and in the application of these two technologies for preserving female fertility of patients who are undergoing cancer treatment.

DESIGN

The literature on human oocyte and ovarian tissue freezing was searched with PubMed. The scientific background, current developments and potential future applications of these two methods were reviewed.

RESULTS

Chemotherapy and/or radiotherapy can induce premature ovarian failure in most of female cancer patients. Consequently, there has been a greater need for options to preserve the reproductive potential of these individuals. However, options are somewhat limited currently, particularly following aggressive chemotherapy and/or radiotherapy treatment protocols. In recent years, there have been considerable advances in the cryopreservation of human oocytes and ovarian tissue. For women facing upcoming cancer therapies, cryopreservation of ovarian tissue and oocytes is a technology that holds promise for banking reproductive potential for the future. Recent laboratory modifications have resulted in improved oocyte survival, oocyte fertilization, and pregnancy rates from frozen-thawed oocytes in IVF. This suggests potential for clinical application.

CONCLUSIONS

In the case of patients who are facing infertility due to cancer therapy, oocyte cryopreservation may be one of the few options available. Ovarian tissue cryopreservation can only be recommended as an experimental protocol in carefully selected patients. In ovarian tissue transplantation, more research is needed in order to enhance the revascularization process with the goal of reducing the follicular loss that takes place after tissue grafting. These technologies are still investigational, although tremendous progress has been made. The availability of such treatment will potentially lead to its demand not only from patients with cancer but also from healthy women who chose to postpone childbearing until later in life and therefore wish to retain their fertility.

Therapy Insight: fertility in women after cancer treatment

Cancer is the second-commonest cause of death in women under 40 years of age in Western Europe and the US. The survival of cancer patients has, nevertheless, improved during the past two decades. During this period, and especially during the last decade, there have been ground-breaking advances in the optimization of the quality of life of patients treated for cancer, in particular by the development of fertility-enhancing and fertility-preserving procedures in young patients treated for cancer. Surgery, chemotherapy and radiation therapy affect the fertility potential of women in different ways. Surgery to remove the uterus and ovaries has a direct impact on fertility. Radiation therapy (external or brachytherapy) can affect ovarian and also uterine function. Different drugs used in chemotherapy can directly influence ovarian function. Some markers have now been evaluated that are predictive of the potential toxic injury to the gonads and uterus. Various procedures have been proposed to preserve the fertility potential in women before anticancer treatment begins or after the tumor is treated; however, such optimization of management should only be undertaken if it does not have a deleterious effect on the survival of the patient.

Human oocyte cryopreservation

The clinical role of oocyte cryopreservation in assisted reproduction, as an adjunct to sperm and embryo cryopreservation, has been comparatively slow to evolve as a consequence of theoretical concerns related to efficacy and safety. Basic biological studies in the 1990's alleviated many of these concerns leading to more widespread adoption of the technology. While a number of babies were born from the approach validated in the 1990's, its perceived clinical inefficiency led to the search for improved methods. Introduction of elevated dehydrating sucrose concentrations during cryopreservation increased survival and fertilization rates, but there is no well-controlled evidence of improved clinical outcome. Similarly, the use of sodium-depleted cryopreservation media has not been demonstrated to increase clinical efficiency. More recently, and in the absence of basic biological studies addressing safety issues, the application of vitrification techniques to human oocytes has resulted in reports of a number of live births. The small number of babies born from clinical oocyte cryopreservation and the paucity of well-controlled studies currently preclude valid comparisons between approaches. Legal restrictions on the ability to select embryos from cryopreserved oocytes in Italy, where many of the available reports originate, also obscure attempts to assess oocyte cryopreservation objectively.

How should the clinical efficiency of oocyte cryopreservation be measured?

Clinical application of oocyte cryopreservation may be in the context of fertility preservation for women about to undergo cytotoxic therapies or may be as an alternative to embryo cryopreservation in routine assisted reproduction. The clinical efficiency of oocyte cryopreservation will be a consequence of the cumulative impact of pre-freeze oocyte quality, postthaw survival and subcellular effects of cryopreservation protocols, which impact on early embryo quality and post-transfer viability, together with the degree of selection which is applied to the available biological material. Any valid assessment must include reference to all the above aspects, particularly when comparing cryopreserved oocytes with non-frozen controls or cryopreserved embryos. Cumulative pregnancy rates from oocyte collections may provide the most relevant index of success. Survival of human oocytes cryopreserved using current methodology is similar to that achieved with early-cleavage-stage embryos. Although evidence suggests that developmental potential may be compromised when current oocyte cryopreservation protocols are applied, there is a paucity of rigorously controlled studies in the literature.