Oocyte cryopreservation

Age-related fertility decline: is there a role for elective ovarian tissue cryopreservation?

Age-related fertility decline (ARFD) is a prevalent concern amongst western cultures due to the increasing age of first-time motherhood. Elective oocyte and embryo cryopreservation remain the most established methods of fertility preservation, providing women the opportunity of reproductive autonomy to preserve their fertility and extend their childbearing years to prevent involuntary childlessness. Whilst ovarian cortex cryopreservation has been used to preserve reproductive potential in women for medical reasons, such as in pre- or peripubertal girls undergoing gonadotoxic chemotherapy, it has not yet been considered in the context of ARFD. As artificial reproductive technology (ART) and surgical methods of fertility preservation continue to evolve, it is a judicious time to review current evidence and consider alternative options for women wishing to delay their fertility. This article critically appraises elective oocyte cryopreservation as an option for women who use it to mitigate the risk of ARFD and introduces the prospect of elective ovarian cortex cryopreservation as an alternative.

Natural Cryoprotective and Cytoprotective Agents in Cryopreservation: A Focus on Melatonin

Cryoprotective and cytoprotective agents (Cytoprotective Agents) are fundamental components of the cryopreservation process. This review presents the essentials of the cryopreservation process by examining its drawbacks and the role of cytoprotective agents in protecting cell physiology. Natural cryoprotective and cytoprotective agents, such as antifreeze proteins, sugars and natural deep eutectic systems, have been compared with synthetic ones, addressing their mechanisms of action and efficacy of protection. The final part of this article focuses melatonin, a hormonal substance with antioxidant properties, and its emerging role as a cytoprotective agent for somatic cells and gametes, including ovarian tissue, spermatozoa and spermatogonial stem cells.

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.

ICSI for non-male factor: do we practice what we preach?

Since its introduction in 1992, intracytoplasmic sperm injection (ICSI) has revolutionized the treatment of infertility due to severe male factor. Over the last three decades, the use of ICSI for non-male factor has increased dramatically, despite guidelines to the contrary from professional societies. Excessive utilization of ICSI is primarily due to an irrational fear of total fertilization failure, which is at odds with rational evidence to support its use.

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.

Comparison of GnRH agonist and hCG for priming in vitro maturation cycles in cancer patients undergoing urgent fertility preservation

In vitro maturation (IVM) of oocytes retrieved at germinal vesicle or Metaphase I stage, followed by vitrification of Metaphase II (MII) oocytes, has recently emerged as an option for urgent fertility preservation (FP). Priming is usually achieved with an injection of hCG, 10,000 IU, 36 hours before retrieval. This study aimed to assess a new method of priming, using GnRH agonists, and compare it to hCG, in cancer patients undergoing urgent FP. From 2009 to 2015, 373 cancer patients underwent MII oocyte cryopreservation after IVM cycles primed either with GnRHa (triptorelin 0.2 mg) (n = 138) or hCG (10,000 IU) (n = 235). Patients’ characteristics were comparable between the two groups. The number of COC retrieved was significantly higher in the GnRHa group (9.1 ± 6.8 versus 7.7 ± 5.5 oocytes, p = 0.04). However, the maturation rates (59 ±25% versus 64 ±26%, p = 0.07, respectively), and the total number of MII oocytes frozen (5.2 ±4.2 versus 4.9 ±4.0, p = 0.6, respectively) were similar between the GnRha and hCG groups. We did not find any difference between GnRHa and hCG priming for IVM. GnRHa priming is more physiological since it stimulates endogenous FSH and LH activity, and is well suited for FP in hormone-sensitive cancers and urgent cases.

Effect of Cytochalasin B Treatment on the Improvement of Survival Rate in Vitrified Pig Oocyte

To improve survival rates of vitrified pig oocytes, the treatment of cytoskeletal stabilizer on an appropriate time is one of the possible approaches. However, the exact treatment timing and effect of cytoskeletal stabilizer such as cytochalasin B (CB) is not well known during oocyte vitrification procedures. Thus, the present study was conducted to determine optimal treatment timing of CB during vitrification and warming procedures. In experiment 1, the survival rates of the post-warming pig oocytes were analyzed by fluorescein diacetate (FDA) assays with 4 classifications. In results, post-warming oocytes showed significantly (p<0.05) decreased number of alive oocytes (31.8% vs. 86.4%) compared to fresh control. In detail, the significant difference (p<0.05) was found only in strong fluorescence (18.2% vs. 70.5%) not in intermediate fluorescence groups (13.6% vs. 15.9%). In experiment 2, CB was treated before (CB-Vitri) and after (Vitri-CB) vitrification. In results, group of Vitri-CB showed significantly (p<0.05) higher (91.6%) survival rates compared to group of CB-Vitri (83.7%), significantly (p<0.05) and comparable with group of Vitri Control (88.7%) by morphological inspection. In FDA assay results, group of Vitri-CB showed significantly (p<0.05) higher (44.2%) survival rates compared to groups of CB-Vitri (36.7%) and Vitri Control (35.1%). In conclusion, the increased survival rates of post-warming pig oocyte treated with Vitri-CB method are firstly described here. The main finding of present study is that the CB treatment during recovery could be helpful to refresh the post-warming pig oocyte resulting its improved survival rates.

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

In vitro maturation of human immature oocytes for fertility preservation and research material

Aim

In recent years, the importance of fertility preservation (FP) has increased. In vitro maturation (IVM), an important technique in FP, has started to be used in the clinic, but controversies persist regarding this technique. Here, a survey of IVM for FP is provided.

Methods

Based on a literature review, the applications of FP, methods of FP, IVM of oocytes that had been collected in vivo and ex vivo, maturation of oocytes after IVM for FP, cryopreservation of oocytes for FP, explanation of the procedures to patients, and recent research on FP using IVM were investigated.

Results

Although IVM for FP remains controversial, the application of FP is expected to expand. Depending on the age and disease status of the patient, various methods of oocyte collection and ovarian stimulation, as well as various needle types and aspiration pressures, have been reported. The maturation rate of IVM in FP ranges widely and requires optimization in the future. In regard to cryopreservation for matured oocytes, the vitrification method is currently recommended.

Conclusion

Regarding FP for patients with cancer, the treatment of cancer is prioritized; thus, the time and use of medicines are often constrained. As several key points regarding IVM remain unclear, well‐designed and specific counseling for patients is necessary.

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.

Development of new method and protocol for cryopreservation related to embryo and oocytes freezing in terms of fertilization rate: A comparative study including review of literature

Background:

Cryopreservation is basically related to meritorious thin samples or small clumps of cells that are cooled quickly without loss. Our main objective is to establish and formulate an innovative method and protocol development for cryopreservation as a gold standard for clinical uses in laboratory practice and treatment. The knowledge regarding usefulness of cryopreservation in clinical practice is essential to carry forward the clinical practice and research.

Materials and Methods:

We are trying to compare different methods of cryopreservation (in two dozen of cells) at the same time we compare the embryo and oocyte freezing interms of fertilization rate according to the International standard protocol.

Results:

The combination of cryoprotectants and regimes of rapid cooling and rinsing during warming often allows successful cryopreservation of biological materials, particularly cell suspensions or thin tissue samples. Examples include semen, blood, tissue samples like tumors, histological cross-sections, human eggs and human embryos. Although presently many studies have reported that the children born from frozen embryos or “frosties,” show consistently positive results with no increase in birth defects or development abnormalities is quite good enough and similar to our study (50–85%).

Conclusions:

We ensure that cryopreservation technology provided useful cell survivability, tissue and organ preservation in a proper way. Although it varies according to different laboratory conditions, it is certainly beneficial for patient's treatment and research. Further studies are needed for standardization and development of new protocol.

Similar in vitro maturation rates of oocytes retrieved during the follicular or luteal phase offer flexible options for urgent fertility preservation in breast cancer patients

STUDY QUESTION

Are in vitro maturation (IVM) rates of cumulus-oocyte complexes (COCs), retrieved from breast cancer patients seeking urgent fertility preservation (FP) before neoadjuvant chemotherapy, different between those recovered in the follicular or in the luteal phase of the cycle?

SUMMARY ANSWER

The present investigation reveals no major difference in the number of COCs recovered or their IVM rates whatever the phase of the cycle at which egg retrieval is performed, suggesting that IVM is a promising tool for breast cancer patients seeking urgent oocyte cryopreservation.

WHAT IS KNOWN ALREADY

FP now represents a standard of care for young cancer patients having to undergo gonadotoxic treatment. Mature oocyte cryopreservation after IVM of COCs has been proposed for urgent FP, especially in women, who have no time to undergo ovarian stimulation, or when it is contraindicated.

STUDY DESIGN, SIZE, DURATION

From January 2011 to December 2014, we prospectively studied 248 breast cancer patients awaiting neoadjuvant chemotherapy, aged 18-40 years, candidates for oocyte vitrification following IVM, either at the follicular or the luteal phase of the cycle.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Serum anti-Müllerian hormone and progesterone levels and antral follicle count (AFC) were measured prior to oocyte retrieval. Patients were sorted into two groups according to the phase of the cycle during which eggs were harvested (Follicular phase group, n = 127 and Luteal phase group, n = 121). Number of COCs recovered, maturation rates after 48 h of culture and total number of oocytes cryopreserved were assessed. Moreover, the oocyte retrieval rate (ORR) was calculated by the number of COCs recovered ×100/AFC.

MAIN RESULTS AND THE ROLE OF CHANCE

In the Follicular and the Luteal phase groups, women were comparable in terms of age, BMI and markers of follicular ovarian status. There was no significant difference in the number of COCs recovered (mean ± SEM), 9.3 ± 0.7 versus 11.1 ± 0.8, and ORR (median (range)) 43.1 (1-100) versus 47.8 (7.7-100)%. Moreover, maturation rates after 48 h of culture (median (range)) were comparable in the follicular and luteal phase groups, 66.7 (20-100) versus 64.5 (0-100)%. Finally, the total number of oocytes cryopreserved (mean ± SEM) was similar in both groups (6.2 ± 0.4 versus 6.8 ± 0.5).

LIMITATIONS, REASONS FOR CAUTION

Despite the intact meiotic competence of immature oocytes recovered during the follicular or the luteal phase, there is a dramatic lack of data regarding the outcome of IVM oocytes cryopreserved in cancer patients.

WIDER IMPLICATIONS OF THE FINDINGS

IVM of oocytes may be an interesting method of FP in urgent situations. Improving the culture conditions will be needed to increase the maturation rates and the overall potential of in vitro matured oocytes.

STUDY FUNDING/COMPETING INTERESTS

None.

TRIAL REGISTRATION NUMBER

N/A.

Vitrification versus slow freezing for women undergoing oocyte cryopreservation

BACKGROUND

Oocyte cryopreservation is a technique with considerable potential in reproductive medicine, including  fertility preservation, as a way of delaying childbearing and as part of oocyte donation programs. Although the technique was relatively ineffective at first more recently numerous modifications have led to higher success rates.

OBJECTIVES

To compare the effectiveness and safety of vitrification and slow freezing as oocyte cryopreservation techniques for fertility outcomes in women undergoing assisted reproduction.

SEARCH METHODS

We searched electronic databases, trial registers and websites, including the Cochrane Menstrual Disorders and Subfertility Group Specialised Register of controlled trials, Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE and PsycINFO (date of search 3 March 2014).

SELECTION CRITERIA

Two review authors independently selected randomised controlled trials (RCTs) comparing vitrification and slow freezing for oocyte preservation in women undergoing assisted reproduction.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted the data from eligible studies and assessed their risk of bias. Any disagreements were resolved by discussion or by a third review author. Data extracted included study characteristics and outcome data. The overall quality of the evidence was assessed using GRADE methods.

MAIN RESULTS

Two RCTs were included in the review (106 participants). Neither study reported live birth rate. Vitrification was associated with an increased clinical pregnancy rate compared to slow freezing (RR 3.86, 95% CI 1.63 to 9.11, P = 0.002, 2 RCTs, 106 women, I(2) = 8%, moderate quality evidence). The effect of vitrification compared to slow freezing on ongoing pregnancy rates was only reported in one small study, with inconclusive findings (RR 6.07, 95% CI 0.86 to 43.04, P = 0.07, one RCT, 28 women, low quality evidence).No data were reported on adverse effects, nor were any other outcomes reported in the included trials. The evidence was limited by imprecision. We assessed the included studies as at low to unclear risk of bias as the methods were not well described.

AUTHORS' CONCLUSIONS

Oocyte vitrification compared to slow freezing probably increases clinical pregnancy rates in women undergoing assisted reproduction. However, the total number of women and pregnancies were low and the imprecision is high which limits applicability. The effect on ongoing pregnancy is uncertain as data were sparse. No data were available on live births or adverse effects.

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.

Egg banking in the United States: current status of commercially available cryopreserved oocytes

OBJECTIVE

To estimate the current availability of donor cryopreserved oocytes and to describe the emerging phenomenon of commercial egg banks (CEBs) in the United States.

DESIGN

Cross-sectional survey of CEBs.

SETTING

E-mail, telephone, and fax survey of all CEB scientific directors, conducted April 2012.

PATIENT(S)

None.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Number and location of CEBs in the United States, years in existence, number of donors, number of available oocytes, level of donor anonymity, donor screening, cost of oocytes to recipients, freezing/thawing technique, pregnancy statistics.

RESULT(S)

Seven CEBs were identified and surveyed (response rate: 100%). The CEBs used three distinct operational models, had been in existence for a median of 2 years (range: 1 to 8 years), with a median 21.5 (range: 6 to 100) donors and 120 (range: 20 to 1,000) currently available oocytes. The median recommended minimum number of eggs to obtain was six (range: four to seven), at an estimated mean cost per oocyte of $2,225 (range: $1,500 to $2,500). An estimated 3,130 oocytes from 294 donors are currently stored for future use. Of these CEBs, 6 (86%) of 7 use vitrification as cryopreservation method. To date, 8,780 frozen donor oocytes from CEBs have been used for in vitro fertilization, resulting in 602 pregnancies. Pregnancy rates per oocyte, available for 5 (71%) of 7 CEBs, were 532 (7.5%) of 7,080 for CEBs using vitrification and 70 (10%) of 700 for the single CEB using slow freezing as cryopreservation method.

CONCLUSION(S)

Frozen donor eggs are currently widely available in the United States. Three different operational models are currently used, resulting in more than 600 pregnancies from oocytes obtained at CEBs. The majority of CEBs use vitrification as cryopreservation technique.

Mature oocyte cryopreservation: a guideline

There is good evidence that fertilization and pregnancy rates are similar to IVF/ICSI with fresh oocytes when vitrified/warmed oocytes are used as part of IVF/ICSI for young women. Although data are limited, no increase in chromosomal abnormalities, birth defects, and developmental deficits has been reported in the offspring born from cryopreserved oocytes when compared to pregnancies from conventional IVF/ICSI and the general population. Evidence indicates that oocyte vitrification and warming should no longer be considered experimental. This document replaces the document last published in 2008 titled, "Ovarian Tissue and Oocyte Cryopreservation," Fertil Steril 2008;90:S241-6.

[Oncofertility: a new focus in women health-care...]

Although treatment and survival are the primary focus of health-care patients, with cancer survivors living longer it is now appropriate to consider their quality of life after treatment, including the possibility of becoming parents. There are several options for fertility preservation in cancer patients. Even though most of them are still experimental and their efficacy and reliability have not been determined, especially in women. The most successful alternative for female survivors is embryo cryopreservation, an approach not suitable for many single or virgin women or even possible for prepubertal girls. Reports of live birth after transplantation of human ovarian tissue have reinforced the clinical potential of ovarian tissue banking for fertility preservation. Many exciting studies are underway to improve the efficacy and solve the problems with current fertility preservation strategies, especially for in vitro culture of cryopreserved tissue or follicles. Continuous efforts to improve current strategies and to develop new strategies will benefit many women and children who are facing premature ovarian failure and sterility.

Retrieval of immature oocytes after chemotherapy for Hodgkin's disease and prolonged ovarian down-regulation with gonadotropin-releasing hormone agonist

OBJECTIVE

To describe isolation and in vitro maturation of primary oocytes from the ovarian cortex in the presence of hypothalamic pituitary down-regulation.

DESIGN

Case report.

SETTING

Tertiary care university-affiliated hospital.

PATIENT(S)

An 18-year-old patient was given treatment with the ABVD (Adriamycin, bleomycin, vinblastine, and dacarbazine) protocol for Hodgkin's disease. She underwent ovarian tissue cryopreservation while being cotreated with GnRH agonist because of disease relapse.

INTERVENTION(S)

Laparoscopic oophorectomy, ovarian tissue cryopreservation, and in vitro maturation of primary oocytes.

MAIN OUTCOME MEASURE(S)

Maturation of primary oocytes isolated from the medium used for preparation of ovarian tissue.

RESULT(S)

Twenty-one immature germinal vesicle-stage oocytes were isolated from the medium of dissection. All were incubated in in vitro maturation medium, and five were maturated and frozen.

CONCLUSION(S)

The fact that germinal vesicle-stage oocytes were present in our patient's medium despite hormonal down-regulation demonstrates that GnRH agonist does not completely inhibit antral follicle development.

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.

Fertility preservation in female cancer patients: current developments and future directions

OBJECTIVE

To review the current advances in fertility preservation strategies and to discuss future directions with an emphasis on ovarian tissue cryobanking.

DESIGN

The publications related to fertility preservation in cancer patients were identified through Medline and other bibliographic databases, focusing on the most recent developments.

CONCLUSION(S)

There are several options for fertility preservation in cancer patients. Even though most of them are still experimental and their efficacy and reliability have not been determined, the future of fertility preservation in women with cancer is promising. In particular, the recent report of a live birth after transplantation of human ovarian tissue has reinforced the clinical potential of ovarian tissue banking for fertility preservation. Many exciting studies are underway to improve the efficacy and solve the problems with current fertility preservation strategies. It is inevitable that we will see the emergence of more complex ethical problems with the application of new technologies to humans. However, continuous efforts to improve current strategies and to develop new strategies will benefit many women and children who are facing premature ovarian failure and sterility.

Cryopreservation of unfertilized human oocytes

Previous investigations revealed that choline-based freezing media developed in our laboratory were superior to conventional sodium-based media for storing mouse oocytes. This paper examines the ability of the choline-based medium CJ2 and a modified form of this medium, CJ3, to cryopreserve unfertilized human oocytes. Oocytes that were consented for research and matured overnight, as well as freshly collected, donor, mature metaphase II (MII) oocytes, were cryopreserved using choline-based media and an optimized slow-cooling protocol. The results showed higher survival and fertilization rates when CJ3 supplemented with 0.2 mmol/l sucrose was used as compared with CJ2 supplemented with either 0.1 mmol/l or 0.2 mmol/l sucrose. Freshly collected oocytes were more difficult to cryopreserve than those matured in vitro. Modification of the base medium proved to be one of the key factors in obtaining survival rates over 90%. Fertilization rates, embryo development, and genetic analysis of embryos resulting from control and frozen-thawed oocytes are provided. There appears to be a high correlation between chromosomal anomalies and abnormal morphology in embryos from thawed oocytes.

The social implications of embryo cryopreservation

OBJECTIVE

To summarize the existing literature regarding the social implications of embryo cryopreservation and outline areas in need of further study.

RESULT(S)

The potential social impact of oocyte cryopreservation has not been investigated. Embryo cryopreservation has been increasingly used to improve the cost-effectiveness of in vitro fertilization (IVF) and expand the options available to infertile couples, yet its widespread adoption has occurred more rapidly than our ability to study the social consequences for the couples and health professionals involved. For maintaining cryopreserved embryos, the existing literature is fragmented and incompletely explores the effects on an infertile couple's psychosocial health and personal relationships, their family planning strategies, or their preferences for the disposition of the embryos. Managing unclaimed embryos continues to create challenges for assisted reproduction professionals.

CONCLUSION(S)

We currently lack a thorough understanding of the numerous social implications of cryopreservation. Major areas for future research include the impact of stored embryos on couples' fertility intentions and psychosocial health, factors that affect couples' decisions about embryo disposition, strategies to minimize unclaimed embryos, and the consequences of oocyte/ovarian cryopreservation.

Cryoloop vitrification of rabbit oocytes

BACKGROUND

Vitrification is assumed to be a promising method to cryopreserve human oocytes but still needs optimization. In this study, rabbit oocytes (fertilized by ICSI) were vitrified with cryoloops, and the effect of three different cryopreservation protocols on spindle configuration and embryo quality was assessed.

METHODS

Metaphase II rabbit oocytes were randomly assigned to one of four groups: (i) control; (ii) E40 [40% ethylene glycol (EG)]; (iii) ED20 [20% EG + 20% dimethylsulphoxide (DMSO)]; and (iv) ED20 + M (20% EG + 20% DMSO + vitrification machine). After warming, one part of each group was fertilized by ICSI to examine the fertilization and embryo cleavage ability, and the others were immunostained for tubulin and chromatin before visualization using confocal microscopy.

RESULTS

The survival rates after warming were 79.1, 83.1 and 82.3%, respectively. In protocols E40 and ED20, the spindles were severely injured and the embryo quality not good compared with those in the ED20 + M group.

CONCLUSIONS

The fastest cooling rate in combination with EG and DMSO as cryoprotectants had the fewest adverse effects on the spindle configuration of rabbit oocytes and embryo development.

An overview of oocyte cryopreservation

The ability to cryopreserve human oocytes and store them indefinitely would be beneficial for cancer patients at risk of becoming sterile after therapy, allow women to delay reproduction, and alleviate religious concerns associated with embryo storage. In 1986, Chen was the first to report a pregnancy originating from a frozen-thawed human oocyte. Although over 100 babies have been born from oocyte storage since then, pregnancy rates remain unacceptably low. Adapting embryo cryopreservation techniques to oocyte storage has had limited success and new reproducible methods are needed. Problem areas other than intracellular ice formation and osmotic effects need to be identified. A broad approach of critical analysis should be conducted regarding the entire cryopreservation process from pre-equilibration and cooling, to thawing and stepout. All established facets deserve reanalysis in order to assess which aspects can be optimized or changed so that cellular demise can be avoided and cellular viability enhanced. New methods, including the use of choline-based media and vitrification have proven useful in increasing survival and pregnancy rates in some clinics. Other methods yet untested, such as injection of complex carbohydrates into the oocyte, deserve further studies. Vitrification research has led to the formulation of new ideas and has demonstrated the flexibility of cells to survive cryopreservation. Although successful, vitrification protocols are potentially harmful and technically challenging, due to elevated cryoprotectant concentrations and rapid cooling rates. Bovine embryo vitrification methods have been used to store human oocytes and embryos, particularly blastocysts with some success. Vitrification solutions containing high molecular weight polymers have also proved beneficial by reducing solution toxicity. In general, further advances are needed to improve human oocyte storage before widespread routine clinical use.

Vitrificação de ovócitos imaturos de bovinos utilizando etilenoglicol associado à trehalose e polivinilpirrolidona

Avaliaram-se os efeitos da vitrificação de ovócitos imaturos de bovinos utilizando o etilenoglicol (EG) associado à trehalose e à polivinilpirrolidona (PVP). Utilizaram-se ovócitos provenientes de ovários de vacas abatidas em matadouro, distribuídos aleatoriamente em três tratamentos (T). TI - ovócitos não desnudados e não congelados, TII - ovócitos vitrificados com cumulus oophorus e TIII - ovócitos desnudados vitrificados. A percentagem de ovócitos recuperados e ovócitos com morfologia normal após a vitrificação foi diferente entre TII e TIII (92,2 e 72,6%; 79,0 e 63,6%, respectivamente). Os ovócitos normais foram cultivados à 38,5ºC em atmosfera de 5% de CO2 por 24 horas. Após o cultivo, os ovócitos foram fecundados e os embriões cultivados in vitro por sete dias. Foram encontradas diferenças entre tratamentos quanto às taxas de maturação nuclear, fecundação e clivagem (83,9, 70,0 e 44,0%; 17,5, 23,7 e 5,1%; 0,0, 0,0 e 0,0% para os tratamentos I, II e III, respectivamente). Apenas no TI foram obtidas mórulas e blastocistos (21,4%). Os procedimentos de vitrificação, segundo os protocolos utilizados, não são indicados para a criopreservação de ovócitos imaturos de bovinos.

The effect of cytotoxic chemotherapy on female fertility

Nurses are now primarily responsible for the provision of patient information, and the administration of an escalating number of cytotoxic agents. This paper aims to provide nurses with key information concerning the adverse effects of cytotoxic chemotherapy on the reproductive system of women of childbearing age. The provision of information on gonadal function and fertility is vital, particularly with the increase in the survival of women treated for cancer, and the trend towards women starting a family later in life. Gonadal toxicity of the various cytotoxic agents, disruption of the menstrual cycle, premature menopause, avoidance of pregnancy, chemotherapy in pregnancy, and fertility prospects post-chemotherapy are addressed in this paper.

Recent progress in oocyte and ovarian tissue cryopreservation and transplantation

Ovarian tissue cryopreservation and transplantation is an experimental technique that has been developed to sustain the reproductive function of women and children who are faced with sterilizing chemotherapy, radiotherapy, or radical reproductive surgery. Oocyte cryopreservation, on the other hand, is less feasible in the context of cancer because there is usually inadequate time to complete an ovarian stimulation cycle. The main promise of oocyte cryopreservation is that it offers an alternative when embryo freezing is not possible for technical, regulatory, or religious reasons. Oocyte freezing is more suitable for a single woman when the concern is age-related decline in fecundity. There have been significant scientific advances in the field of cryopreservation of ovarian tissue and oocytes, especially within the past few years. Ovarian function has been reported after the first cases of ovarian transplantation, and the number of pregnancies from cryopreserved oocytes has grown. Ovarian tissue and oocyte freezing can now be recommended in a carefully selected group of patients, provided that these options are offered under protocols that are approved by an institutional review board.

Effects of chilling to 0 degrees C on the morphology of meiotic spindles in human metaphase II oocytes

OBJECTIVE

To determine the effects of chilling to 0 degrees C on the meiotic spindle of human metaphase II oocytes, as observed by optical sectioning microscopy.

DESIGN

Laboratory study.

SETTING

Academic research laboratory in a medical school.

PATIENT(S)

Seventy-two women undergoing infertility treatment donated a total of 108 oocytes.

INTERVENTION(S)

Metaphase II oocytes were stripped of their cumulus cells, cooled directly to 0 degrees C, and held for periods of 1 to 10 minutes. They were then fixed at 37 degrees C, stained for immunofluorescence, and examined microscopically.

MAIN OUTCOME MEASURE(S)

Morphology of the meiotic spindle in chilled and control oocytes.

RESULT(S)

Microscopic evaluations of 46 chilled oocytes revealed various time-dependent changes in microtubules compared to 9 control oocytes. After 1 minute at 0 degrees C, spindle damage was negligible, but in oocytes cooled for 2 or 3 minutes, there was obvious shortening of the spindle and loss of polarity. Cooling to 0 degrees C for 4 to 9 minutes resulted in increasingly more drastic changes; by 10 minutes the spindles had totally disappeared. Despite depolymerization of microtubular tubulin at 0 degrees C, the chromosomes did not become dispersed, but remained anchored even in the absence of spindles.

CONCLUSION(S)

Even brief exposure of human oocytes to temperatures near 0 degrees C causes profound alterations of the meiotic spindle.

Micromanipulation of cryopreserved embryos and cryopreservation of micromanipulated embryos in PGD

The possibility to employ cryopreservation in Preimplantation Genetic Diagnosis (PGD) should enlarge the opportunities for research and clinical activity. For these purposes, we tried three kinds of approaches on human abnormal embryos: (1) cryopreservation of biopsied embryos; (2) biopsy of thawed embryos; and (3) biopsy of embryos derived from thawed oocytes. Our preliminary results show that: (1) biopsy of thawed embryos is feasible and FISH analysis is possible on both survived and lysed cells; (2) Optimization of freezing/thawing procedures are necessary to obtain better survival rate after thawing of biopsied embryos; (3) Biopsy and FISH are feasible on embryos derived from thawed oocytes and they could be a good way to study the chromosomal arrangement of these poorly investigated embryos.