Difficulties improving ovarian functional recovery by microvascular transplantation and whole ovary vitrification

Cryoprotective effect of antifreeze protein III on the rabbit ovary

CONTEXT

Ovarian tissue cryopreservation is effective in preserving fertility in cancer patients who have concerns about fertility loss due to cancer treatment. However, ischemia reduces the lifespan of grafts. Microvascular transplantation of cryopreserved whole ovary may allow immediate revascularisation, but the damage incurred during the cryopreservation procedure may cause follicular depletion; hence, preventing chilling injury would help maintain ovarian function.

AIM

This study was designed to investigate the beneficial effects of antifreeze protein III (AFP III) on rabbit ovary cryopreservation.

METHODS

Ovaries (n =25) obtained from 5-month-old female rabbits (n =13) were frozen by slow freezing and vitrification. Cryoprotectant media were supplemented with and without 1mg/mL of AFP III. The experiment was divided into five groups: fresh control group (F), slow freezing group (S), slow freezing group with AFP III (AFP III-S), vitrification group (V) and vitrification group with AFP III (AFP III-V). All groups of ovaries were examined by histological characteristics analysis, ultrastructural analysis, apoptosis detection and follicle viability test.

KEY RESULTS

With slow freezing, the normal rate of change in follicle morphology, density of stromal cells and the survival rate of follicles in the AFP III supplemented group were significantly higher than those in the non-supplemented group, and a lower oocyte apoptotic rate was shown in the AFP III supplemented group. In the vitrification groups, the normal rate of change in follicle morphology and density of stromal cells in the AFP III supplemented group were significantly higher than those in the non-supplemented group, and a lower oocyte apoptotic rate was found in the AFP III supplemented group. But there was no obvious difference in the survival rate of follicles between the two groups. There was also no significant difference in the normal rate of change in follicle morphology, the survival rate of follicles and the apoptotic rate of oocytes between the vitrification and slow freezing groups (P >0.05), but the density of stromal cells in the vitrification groups was statistically higher than that of the slow freezing group (P <0.05).

CONCLUSIONS

The addition of AFP III in slow freezing and vitrification could improve the cryoprotective effect of ovaries, which was more evident in slow freezing.

IMPLICATIONS

The findings of this study provide a foundation for further research on the effects of AFP III in human ovarian tissue.

Can frozen-thawed human ovary withstand refreezing-rethawing in the form of cortical strips?

PURPOSE

The aim of this study was to elucidate whether ovarian tissue is able to withstand a double freezing-thawing procedure.

METHODS

Human ovarian cortical biopsies from 4 thawed whole ovaries were divided into 4 experimental subgroups: (a) frozen-thawed non-grafted group, (b) frozen-thawed xenografted group, (c) refrozen-rethawed non-grafted group, and (d) refrozen-rethawed xenografted group. Xenografting was performed using 8 severe combined immunodeficient mice for a total duration of 21 days. The following analyses were conducted: classic hematoxylin and eosin staining, Ki67 immunolabeling, transmission electron microscopy, Masson's green trichrome, and double CD34 immunostaining.

RESULTS

Morphologically normal preantral follicles were detected in all groups. We observed a dramatic decline of more than 65% in early preantral follicle survival rates after grafting of both frozen-thawed (p < 0.0001) and refrozen-rethawed (p < 0.0001) ovarian tissue. However, mean follicle densities remained comparable between the frozen-thawed and refrozen-rethawed non-grafted groups, as well as both grafted groups. Equivalent proportions of proliferating early preantral follicles were identified in frozen-thawed and refrozen-rethawed samples, whether the tissue was grafted or not. Furthermore, we did not observe any significant difference in atretic follicle rates between any of the four groups, and the ultrastructural quality of follicles appeared unaffected by the refreezing procedure. Similar proportions of fibrosis were noted in the frozen-thawed and refrozen-rethawed groups, irrespective of grafting. Finally, no significant differences were witnessed in terms of vascularization.

CONCLUSION

We were able to demonstrate, for the first time, that refrozen-rethawed ovarian tissue has the same functional characteristics as frozen-thawed ovarian tissue.

Whole Ovary Cryopreservation and Transplantation: A Systematic Review of Challenges and Research Developments in Animal Experiments and Humans

Ovarian tissue cryopreservation and transplantation is the only fertility preservation option that enables both restoration of fertility and resumption of ovarian endocrine function, avoiding the morbidity associated with premature menopause. It is also the only technique available to prepubertal patients and those whose treatment cannot be delayed for life-threatening reasons. Ovarian tissue cryopreservation can be carried out in two different ways, either as ovarian cortical fragments or as a whole organ with its vascular pedicle. Although use of cortical strips is the only procedure that has been approved by the American Society for Reproductive Medicine, it is fraught with drawbacks, the major one being serious follicle loss occurring after avascular transplantation due to prolonged warm ischemia. Whole ovary cryopreservation involves vascular transplantation, which could theoretically counteract the latter phenomenon and markedly improve follicle survival. In theory, this technique should maintain endocrine and reproductive functions much longer than grafting of ovarian cortical fragments. However, this procedure includes a number of critical steps related to (A) the level of surgical expertise required to accomplish retrieval of a whole ovary with its vascular pedicle, (B) the choice of cryopreservation technique for freezing of the intact organ, and (C) successful execution of functional vascular reanastomosis upon thawing. The aim of this systematic review is to shed light on these challenges and summarize solutions that have been proposed so far in animal experiments and humans in the field of whole ovary cryopreservation and transplantation.

Preserving fertility in female patients with hematological malignancies: a multidisciplinary oncofertility approach

Oncofertility is a new interdisciplinary field at the intersection of oncology and reproductive medicine that expands fertility options for young cancer patients. The most common forms of hematological malignancies that occur in girls and young women and therefore necessitate oncofertility care are acute lymphocytic leukemia, acute myeloid leukemia, non-Hodgkin's lymphoma, and Hodgkin's lymphoma. Aggressive gonadotoxic anticancer regimens including alkylating chemotherapy and total body irradiation are used often in treating girls and young women with hematological malignancies. The risks of gonadotoxicity and subsequent iatrogenic premature ovarian insufficiency and fertility loss depend mainly on the type and stage of the disease, dose of anticancer therapy as well as the age of the patient at the beginning of treatment. To avoid or at least mitigate the devastating complications of anticancer therapy-induced gonadotoxicity, effective and comprehensive strategies that integrate different options for preserving and restoring fertility ranging from established to experimental strategies should be offered before, during, and after chemotherapy or radiotherapy. A multidisciplinary approach that involves strong coordination and collaboration between hemato-oncologists, gynecologists, reproductive biologists, research scientists, and patient navigators is essential to guarantee high standard of care.

The promise of organ and tissue preservation to transform medicine

The ability to replace organs and tissues on demand could save or improve millions of lives each year globally and create public health benefits on par with curing cancer. Unmet needs for organ and tissue preservation place enormous logistical limitations on transplantation, regenerative medicine, drug discovery, and a variety of rapidly advancing areas spanning biomedicine. A growing coalition of researchers, clinicians, advocacy organizations, academic institutions, and other stakeholders has assembled to address the unmet need for preservation advances, outlining remaining challenges and identifying areas of underinvestment and untapped opportunities. Meanwhile, recent discoveries provide proofs of principle for breakthroughs in a family of research areas surrounding biopreservation. These developments indicate that a new paradigm, integrating multiple existing preservation approaches and new technologies that have flourished in the past 10 years, could transform preservation research. Capitalizing on these opportunities will require engagement across many research areas and stakeholder groups. A coordinated effort is needed to expedite preservation advances that can transform several areas of medicine and medical science.

Safeguarding Fertility With Whole Ovary Cryopreservation and Microvascular Transplantation: Higher Follicular Survival With Vitrification Than With Slow Freezing in a Ewe Model

BACKGROUND

In young women, ovarian cortex cryopreservation before gonadotoxic chemotherapy and its avascular grafting after cancer healing permitted fertility restoration. However, ischemia reduced the grafts' lifespan. Microvascular transplantation of cryopreserved whole ovary may allow immediate revascularization, ensuring better fertility preservation, but the best cryopreservation method is unknown. We aimed to compare slow freezing and vitrification of whole ovary for fertility preservation purposes, in an ewe model.

METHODS

Twelve ewes were allocated at random to slow freezing (n = 6) or vitrification group (n = 6). Ewes' left ovary was removed and cryopreserved. Dimethyl sulfoxide 2 M was used as cryoprotector for slow freezing. Vitrification was obtained using increasing concentrations of a vitrification solution of the latest generation (VM3) and gradual temperature lowering to minimize toxicity. After a month, the right ovary was removed, the left ovary was thawed/warmed, and its vessels were anastomosed to the right pedicle. Fertility and ovarian function were assessed for 3 years. Ovarian follicles in native and transplanted ovaries were counted and compared at study completion.

RESULTS

Hormonal secretion resumed in all ewes of both groups. One ewe of the slow-freezing group delivered healthy twins 1 year 9 months and 12 days after transplantation. Estimated whole follicle survival was very low in both groups but significantly higher after vitrification than after slow freezing (0.3% ± 0.5% vs 0.017% ± 0.019%, respectively; p < 0.05).

CONCLUSIONS

Further progress is needed before whole-ovary cryopreservation can be considered an option for safeguarding fertility. Whole ovary vitrification provides better follicular survival compared to slow freezing and may be a valuable cryopreservation option.

Fertility preservation through gonadal cryopreservation

Fertility preservation is an area of immense interest in today's society. The most effective and established means of fertility preservation is cryopreservation of gametes (sperm and oocytes) and embryos. Gonadal cryopreservation is yet another means for fertility preservation, especially if the gonadal function is threatened by premature menopause, gonadotoxic cancer treatment, surgical castration, or diseases. It can also aid in the preservation of germplasm of animals that die before attaining sexual maturity. This is especially of significance for valuable, rare, and endangered animals whose population is affected by high neonatal/juvenile mortality because of diseases, poor management practices, or inbreeding depression. Establishing genome resource banks to conserve the genetic status of wild animals will provide a critical interface between ex-situ and in-situ conservation strategies. Cryopreservation of gonads effectively lengthens the genetic lifespan of individuals in a breeding program even after their death and contributes towards germplasm conservation of prized animals. Although the studies on domestic animals are quite promising, there are limitations for developing cryopreservation strategies in wild animals. In this review, we discuss different options for gonadal tissue cryopreservation with respect to humans and to laboratory, domestic, and wild animals. This review also covers recent developments in gonadal tissue cryopreservation and transplantation, providing a systematic view and the advances in the field with the possibility for its application in fertility preservation and for the conservation of germplasm in domestic and wild species.

New advances in ovarian autotransplantation to restore fertility in cancer patients

Human ovary autotransplantation is a promising option for fertility preservation of young women and girls undergoing gonadotoxic treatments for cancer or some autoimmune diseases. Although experimental, it resulted in at least 42 healthy babies worldwide. According to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a systematic literature review was performed for all relevant full-text articles published in English from 1 January 2000 to 01 October 2015 in PubMed to explore the latest clinical and research advances of human ovary autotransplantation. Human ovary autotransplantation involves ovarian tissue extraction, freezing/thawing, and transplantation back into the same patient. Three major forms of human ovary autotransplantation exist including (a) transplantation of cortical ovarian tissue, (b) transplantation of whole ovary, and (c) transplantation of ovarian follicles (artificial ovary). According to the recent guidelines, human ovary autotransplantation is still considered experimental; however, it has unique advantages in comparison to other options of female fertility preservation. Human ovary autotransplantation (i) does not need prior ovarian stimulation, (ii) allows immediate initiation of cancer therapy, (iii) can restore both endocrine and reproductive ovarian functions, and (iv) may be the only fertility preservation option suitable for prepubertal girls or for young women with estrogen-sensitive malignancies. As any other fertility preservation option, human ovary autotransplantation has both advantages and disadvantages and may not be feasible for all cases. The major challenges facing this option are how to avoid the risk of reintroducing malignant cells and how to prolong the lifespan of ovarian transplant as well as how to improve artificial ovary results.

An ovarian bioreactor for in vitro culture of the whole bovine ovary: a preliminary report

Background

Improved cancer therapeutics and enhanced cancer survivorship have emphasized the severe long-term side effects of chemotherapy. Specifically, studies have linked many chemotherapy agents with primary ovarian insufficiency, although an exact insult model has not yet been determined. To investigate and ultimately solve this problem, a novel device for extended study of mammalian ovaries in vitro was developed.

Methods

A bioreactor was fabricated for bovine ovarian culture that provides intravascular delivery of media to the ovary through isolation and cannulation of a main ovarian artery branch. Whole ovaries were cultured in vitro using three methods: (1) continuously supplied fresh culture media, (2) recirculated culture media, or (3) continuously supplied fresh culture media supplemented with 500 nM doxorubicin for 24 or 48 h. TUNEL assay was used to assess apoptotic cell percentages in the three groups as compared to uncultured baseline ovaries.

Results

The ovary culture method was shown to maintain cell viability by effectively delivering nutrient-enriched pH-balanced media at a constant flow rate. Lower apoptosis observed in ovaries cultured in continuously supplied fresh culture media illustrates that this culture device and method are the first to sustain whole bovine ovary viability for 48 h. Meanwhile, the increase in the percentage of cell apoptosis with doxorubicin treatment indicates that the device can provide an alternative model for testing chemotherapy and chemoprotection treatments to prevent primary ovarian insufficiency in cancer patients.

Conclusions

An ovarian bioreactor with consistent culture media flow through an ovarian vasculature-assisted approach maintains short-term whole bovine ovary viability.

Electronic supplementary material

The online version of this article (doi:10.1186/s13048-016-0249-4) contains supplementary material, which is available to authorized users.

Cryopreservation of whole bovine ovaries: comparisons of different thawing protocols

OBJECTIVE

The aim of this study was to perform a comparative investigation of several different thawing protocols and to determine an appropriate protocol for thawing whole bovine frozen ovaries.

STUDY DESIGN

Bovine ovaries were slowly frozen and then thawed by applying different protocols. Ultrastructural change, follicle viability, and the hormone levels of culture supernatant were measured.

RESULTS

The percentage of morphologically normal primordial follicles and the hormone levels of culture supernatant in group D (two-step, thawing in water at 39°C) were significantly higher than those in any other group. Moreover, the ultrastructural alteration of oocyte in group D (two-step, thawing in water at 39°C) was slighter than those in any other group.

CONCLUSIONS

The two-step protocol involving short-term exposure to water at a moderately high temperature (39°C) proved to be a suitable for thawing bovine whole ovaries.

Female fertility preservation strategies: cryopreservation and ovarian tissue in vitro culture, current state of the art and future perspectives

In the present review, the main strategies of female fertility preservation are covered. Procedures of fertility preservation are necessary for women who suffer from diseases whose treatment requires the use of aggressive therapies, such as chemotherapy and radiotherapy. These kinds of therapy negatively influence the health of gametes and their progenitors. The most commonly used method of female fertility preservation is ovarian tissue cryopreservation, followed by the retransplantation of thawed tissue. Another approach to female fertility preservation that has been actively developed lately is the ovarian tissue in vitro culture. The principal methods, advantages and drawbacks of these two strategies are discussed in this article.

Fertility preservation in reproductive-age women facing gonadotoxic treatments

BACKGROUND

Advancements in the treatments for cancer and autoimmune and other hematologic conditions continue to improve survival and cure rates. Despite those changes, various gonadotoxic agents and other treatments can still compromise the future fertility of many women. Progress in medical and surgical reproductive technologies has helped to offset the reproductive consequences of the use of gonadotoxic therapies, and allows for future fertility and normal pregnancy.

METHODS

A review of the literature was performed to outline the pathophysiology of gonadotoxicity from various treatments. The success of fertility preservation, fertility sparing, and cryopreservation options are reviewed. Barriers and facilitators to referral and oncofertility treatment in Canada are also outlined.

RESULTS

According to the quality of the evidence, recommendations are made for fertility assessment, patient referral, cryopreservation, and other assisted reproductive technologies.

CONCLUSIONS

To ensure ongoing fertility in women undergoing gonadotoxic treatments, assisted reproductive technologies can be combined with a multidisciplinary approach to patient assessment and referral.

Preliminary observations on whole-ovary xenotransplantation as an experimental model for fertility preservation

Ovarian tissue preservation and retransplantation is a promising strategy to restore fertility in cancer survivors. Ischaemia accompanying ovarian tissue grafting, however, can lead to significant follicle loss. Transplantation of the whole ovary by vascular anastomosis has been considered as an alternative to prevent widespread ischaemic damage. In this study, the feasibility and function of transplanting whole ovary with intact vasculature were evaluated, with the goal of developing a xenograft model for studies using donated human ovaries. Whole-swine ovaries with vascular pedicles were perfused and transplanted as intact ovaries by anastomosis into irradiated ovariectomized nude rats (n = 10). The observation period was between 1 and 4 weeks. Fresh swine ovaries served as controls (n = 10). Ovarian stroma and follicle populations were assessed through histological examination in both transplanted and control ovaries. Most of the transplanted whole ovaries (n = 6) maintained stromal quality and all preantral follicle classes were represented, although follicle numbers decreased compared with fresh control. Four transplanted ovaries were fibrotic after 1-4 weeks within the nude rat. Our results demonstrate transplantation of whole-pig ovary into nude rats is possible and support development of this xenograft model system for human studies.

Good preservation of stromal cells and no apoptosis in human ovarian tissue after vitrification

The aim of this study was to develop a vitrification procedure for human ovarian tissue cryopreservation in order to better preserve the ovarian tissue. Large size samples of ovarian tissue retrieved from 15 female-to-male transgender subjects (18–38 years) were vitrified using two solutions (containing propylene glycol, ethylene glycol, and sucrose at different concentrations) in an open system. Light microscopy, transmission electron microscopy, and TUNEL assay were applied to evaluate the efficiency of the vitrification protocol. After vitrification/warming, light microscopy showed oocyte nucleus with slightly thickened chromatin and irregular shape, while granulosa and stromal cells appeared well preserved. Transmission electron microscopy showed oocytes with slightly irregular nuclear shape and finely dispersed chromatin. Clear vacuoles and alterations in cellular organelles were seen in the oocyte cytoplasm. Stromal cells had a moderately dispersed chromatin and homogeneous cytoplasm with slight vacuolization. TUNEL assay revealed the lack of apoptosis induction by vitrification in all ovarian cell types. In conclusion after vitrification/warming the stromal compartment maintained morphological and ultrastructural features similar to fresh tissue, while the oocyte cytoplasm was slightly damaged. Although these data are encouraging, further studies are necessary and essential to optimize vitrification procedure.

Ovarian tissue cryopreservation: a committee opinion

Ovarian tissue cryopreservation is an option to preserve reproductive potential in patients who must urgently undergo aggressive chemotherapy and/or radiotherapy or who have other medical conditions requiring treatment that may threaten ovarian function and subsequent fertility. Ovarian tissue cryopreservation may be the only option available to prepubertal girls undergoing such treatments. However, these techniques are still considered to be experimental. This document outlines the current technology, clinical outcomes, and risks of ovarian tissue cryopreservation and recommendations for clinical applications. This document and the document "Mature Oocyte Cryopreservation: A Guideline" published in 2013 (Fertil Steril 2013;99:37-43) replace the document "Ovarian Tissue and Oocyte Cryopreservation" last published in 2008 (Fertil Steril 2008;90:S241-6).

Strategies for fertility preservation in young patients with cancer: a comprehensive approach

As a result of treatment innovations, the survival rates of young people with cancer have increased substantially. The cancers most frequently diagnosed in adults aged 25-49 years include breast, colorectal and cervical cancer and malignant melanoma (Cancer Research UK, 2009). The 5-year survival rates of over 90 % for many malignancies are now reported in young people. But the diagnosis and treatment of cancer often poses a threat to fertility. Methods of fertility preservation are evolving quickly and awareness needs to grow in the medical community regarding these methods. Studies suggest that the ability to have biological children is of great importance to many people. The possible future effects of chemotherapy or radiotherapy on fertility should be discussed with all cancer patients who have reproductive potential. Moreover, fertility preservation should be considered for all young people undergoing potentially gonadotoxic treatment. This article covers the various methods of fertility preserving options in young men and women with respect to the various treatment modalities that they may be subjected to. Sperm banking is a simple and low cost intervention. Embryo cryopreservation is the only established method of female fertility preservation. Oocyte cryopreservation offers a useful option for women without a male partner. Emergency ovarian stimulation and cryopreservation of ovarian tissue (followed by tissue transplantation or in-vitro maturation of oocytes) are experimental techniques for women who require urgent cancer treatment. Large, well-controlled studies are also required to identify any unexpected long-term sequelae of cryopreservation of oocytes and ovarian tissue.

Whole ovine ovaries as a model for human: perfusion with cryoprotectants in vivo and in vitro

These experiments were performed to test the perfusion of ovine as a model for human ovaries by cryoprotectants in vivo at high temperature when the permeability of capillaries is high and when blood is insensibly replaced by the solution of cryoprotectants. By our hypothetical supposition, ovaries could be saturated by cryoprotectants before their surgical removal. The objective was to examine the effectiveness of perfusion of ovine ovaries with vascular pedicle in vivo and in vitro. Arteria ovarica was cannuled and ovaries were perfused by Leibovitz L-15 medium + 100 IU/mL heparin + 5% bovine calf serum + 6% dimethyl sulfoxide + 6% ethylene glycol + 0.15 M sucrose + Indian ink in vivo and in vitro. In the first and second cycle of experiments, ovaries (n = 13 and n = 23) were perfused in vivo and in vitro, respectively, during 60 min with the rate of perfusion 50 mL/h (0.8 mL/min). It was established with in vivo perfusion that only about 10% of ovarian tissues were perfused due to an appearance of multiple anastomoses when the perfusion medium goes from arteria ovarica to arteria uterina without inflow into the ovaries. It was concluded that in vitro perfusion of ovine intact ovaries with vascular pedicle by freezing medium is more effective than this manipulation performed in vivo.

Direct comparative analysis of conventional and directional freezing for the cryopreservation of whole ovaries

OBJECTIVE

To compare conventional slow equilibrium cooling and directional freezing for cryopreservation of whole ovaries.

DESIGN

Experimental animal study.

SETTING

Academic research environment.

ANIMAL(S)

Adult ewes.

INTERVENTION(S)

Eighty-one ovaries were randomly assigned to fresh control, conventional freezing (CF), and directional freezing (DF) group. Ovaries of CF and DF groups were perfused via the ovarian artery with Leibovitz L-15 medium, 10% fetal bovine serum, and 1.5 M dimethyl sulfoxide for 5 minutes. Each ovary was inserted into a glass test tube containing 10 mL of the same solution and cooled to -100°C or -70°C, respectively. Ovaries were stored in liquid nitrogen for a minimum of 2 weeks.

MAIN OUTCOME MEASURE(S)

Structural integrity of cortical and medulla regions, vascular integrity, follicle in vitro development, cell proliferation, and DNA damage and repair.

RESULT(S)

All examined parameters indicate that the structure of DF ovaries remains largely intact and comparable to fresh controls, whereas significant damages were observed in CF ovaries.

CONCLUSION(S)

Directional freezing allows good preservation of whole ovaries, with most of the parameters taken into consideration almost identical to those recorded in fresh control samples. This encourages a reconsideration of the possible use of whole-ovary cryopreservation as a viable alternative to cortical fragments.

Ovarian function is restored after grafting of cryopreserved immature ovary in ewes

As a result of advances in medical treatment, almost 80% of children who are diagnosed with cancer survive long-term. The adverse consequences of cancer treatments include impaired puberty and fertility. In prepubertal girls, the only therapeutic option is the cryopreservation of an ovary. To date, a dozen births have been reported after reimplantation of cryopreserved mature ovaries. To analyze ovarian function after immature grafts, we performed ovarian grafting in a ewe model. Fresh or cryopreserved ovaries from immature ewes were autografted in prepubertal or adult ewes. Cyclic hormonal activity was recovered 3 mo after grafting. Histological analysis demonstrated the presence of all follicle populations and corpora lutea not affected by cryopreservation. After 3 reproductive seasons, births had been observed in all groups, and the follicle-stimulating hormone status was under the limit, which indicated an exhausted ovary. As an indicator of potential imprinting default, the methylation status of the Igf2r gene was analyzed and did not show significant alteration compared with that of nonmanipulated animals. Taken together, these results demonstrate that immature ovarian grafting is able to restore spontaneous puberty and fertility and could guide the reimplantation of immature cortex in women.

Factors related to unstained areas in whole ewe ovaries perfused with a metabolic marker

STUDY QUESTION

What factors are associated with the presence of areas unexposed to the perfusate after whole ovary perfusion?

SUMMARY ANSWER

Over half the ovaries perfused with the metabolic marker methylthiazolyl blue tetrazolium (MTT) were incompletely stained. Incomplete staining was statistically significantly associated with a small ovarian slice surface area, inexperience of the experimenter, and the presence of a corpus luteum.

WHAT IS KNOWN ALREADY

Whole ovary cryopreservation followed by vascular auto-transplantation has provided poor outcomes as an alternative way to safeguard fertility. Perfusion, commonly used to expose the ovaries to cryoprotectants, may miss areas excluded from the vascular network, explaining subsequent poor ovarian functionality.

STUDY DESIGN, SIZE, DURATION

An observational study of 360 ewe ovaries stained by in vitro perfusion with MTT as a qualitative marker of tissue blood supply was performed. A logistic regression model was built to identify factors associated with incomplete ovary staining.

MATERIALS, SETTING, METHODS

Whole ewe ovaries with their vascular pedicles were perfused at 0.35 ml/min with 1 g/l MTT for 2 h at 39°C under 19 experimental conditions. The pedicles were removed and the ovaries cut in half sagittally and photographed. The unstained area of the slice surface was measured. Times from ovary collection to ovary rinsing and to MTT perfusion initiation, ovary weight and slice surface area, presence of a corpus luteum and operator experience (number of ovaries previously perfused) were recorded. Pedicle MTT staining was quantified at 564 nm after solubilization in alcohol.

MAIN RESULTS AND THE ROLE OF CHANCE

Unstained areas were observed in 64.4% of the ovaries. Multivariate analysis found that incomplete ovary staining was independently associated with lower experimenter experience (P < 0.02), smaller ovary slice surface area (P < 0.0001) and presence of a corpus luteum (P < 0.01). The presence of unstained areas was independent from experimental conditions. The rate of incomplete ovary staining decreased from 83 to 60% beyond the 80th perfused ovary (P < 0.0001).

LIMITATIONS, REASONS FOR CAUTION

Descriptive study.

WIDER IMPLICATIONS OF THE FINDINGS

Blood-supply impairments that result in incomplete perfusion might adversely affect outcomes after whole ovary cryopreservation. Improved perfusion techniques should enhance success.

Female fertility loss and preservation: threats and opportunities

BACKGROUND

Ovarian aging and cytotoxic treatments are the most common causes for fertility loss in women. With increasing numbers of young female survivors following cytotoxic cancer treatments, the issue of fertility preservation has assumed greater importance.

METHODS

We review the literature on the causes of female fertility loss as well as the recent advances in fertility preservation options and strategies that might be of interest to oncologists. Currently, several methods and techniques exist for fertility preservation of female patients with cancer including embryo freezing, ovarian protection techniques, oocyte cryopreservation, ovarian tissue cryopreservation followed by autotransplantation, and recently in vitro culture of ovarian tissue, follicles, and oocytes. Each method or technique has advantages and disadvantages related to current success rate, required delay in cancer treatment, sperm requirement, and risk of reintroducing cancer cells.

RESULTS

To date, embryo freezing is the only established method successfully and widely used for fertility preservation of female patients with cancer. The other methods are promising but still considered experimental.

CONCLUSION

Patient awareness, physician knowledge, early counseling, costs management, international registry, interdisciplinary networks, and research development are necessary to improve the current care in the field of female fertility preservation.

Optimizing cryoprotectant perfusion conditions for intact ovary: a bovine model

PURPOSE

The aim of this study was to detect the effects of different perfusion pressure and different length of perfusion period on whole ovarian cryopreservation

METHODS

Bovine whole ovaries were vitrified-warmed. The ovaries were divided into the experimental groups according to different perfusion pressure and different length of perfusion period. Follicular viability was assessed using the trypan blue test; the percentage of morphologically normal primordial follicles and the 17-β estradiol level in the culture supernatants were measured.

RESULTS

When perfusion pressure was 100 mmHg, and the length of perfusion period was 40 min, the viability of ovarian tissues in bovine whole ovarian cryopreservation were higher than other protocols.

CONCLUSION

Protocol IIb (the perfusion pressure was 100 mmHg, and the length of perfusion period was 40 min) was appropriate for bovine whole ovarian cryopreservation.

Ovarian tissue and follicle transplantation as an option for fertility preservation

OBJECTIVE

To review and summarize data from the scientific literature on ovarian tissue and follicle transplantation as an option for fertility preservation.

DESIGN

Review of pertinent literature.

SETTING

University hospital.

PATIENT(S)

Women having undergone ovarian tissue transplantation.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Review of the literature.

RESULT(S)

Over the last decade, the field of ovarian transplantation and cryopreservation has significantly progressed, becoming applicable in humans. Indeed, fresh and frozen cortical ovarian tissue transplantations have been successfully reported worldwide, resulting in around 28 healthy babies. Although ovarian-tissue harvesting seems to be safe, the risk of reimplantation of cancer from ovarian cortical transplants cannot be estimated at this time. As a consequence, auto-transplantation of ovarian tissue in women having suffered from systemic hematological malignancies is not recommended. In these situations, reimplantation of isolated ovarian follicles might represent an interesting option in the future.

CONCLUSION(S)

Although the clinical experience is limited, the robust results obtained open new perspectives for the management of premature ovarian failure resulting or not from gonadotoxic treatments.

Recent advances in oocyte and ovarian tissue cryopreservation and transplantation

Options for preserving fertility in women include well-established methods such as fertility-sparing surgery, shielding to reduce radiation damage to reproductive organs, and emergency in-vitro fertilisation after controlled ovarian stimulation, with the aim of freezing embryos. The practice of transfering frozen or thawed embryos has been in place for over 25 years, and today is a routine clinical treatment in fertility clinics. Oocytes may also be frozen unfertilised for later thawing and fertilisation by intracytoplasmic sperm injection in vitro. In recent years, oocyte cryopreservation methods have further developed, reaching promising standards. More than 1000 children are born worldwide after fertilisation of frozen and thawed oocytes. Nevertheless, this technique is still considered experimental. In this chapter, we focus on options for fertility preservation still in development that can be offered to women. These include freezing of oocytes and ovarian cortex and the transplantation of ovarian tissue.

Validation of a new metabolic marker to assess the vascular viability of vitrified whole sheep ovaries

BACKGROUND

Whole ovary cryopreservation has been suggested as a means to preserve fertility. In animal models, autologous cryopreserved ovary transplants frequently undergo thrombosis and a method to assess the vascular viability of cryopreserved ovaries would be valuable. We developed a staining method using methylthiazolyl blue tetrazolium (MTT, a metabolic marker) to assess the pedicle metabolism of whole ovaries vitrified using cryoprotectant called 'VS4'.

METHODS

Whole sheep ovaries were perfused with MTT (1 g/l). In one group, ovarian tissue lesions were induced by immersing the ovarian pedicle in medium at 53°C or 65°C or in liquid nitrogen prior to MTT perfusion. In the second group, several metabolic substrates (d-glucose, l-glucose and pyruvic acid) and inhibitors [2-deoxy-d-glucose for d-glucose metabolism, azide for mitochondrial respiration and diphenyleneiodonium (DPI) for NADPH oxidase (an effector of the pentose phosphate pathway)] were added to the MTT stain. The third group was subjected to VS4 ± vitrification/warming prior to MTT perfusion. Pedicle MTT staining was assessed qualitatively by histological examination of frozen sections or quantified at 564 nm after solubilization in alcohol.

RESULTS

MTT strongly and reproducibly stained the vascular smooth muscle. Heating at 53°C or 65°C or cooling in liquid nitrogen significantly diminished MTT staining by 48% (P = 0.001, n = 10), 94% (P = 0.0002, n = 10) and 94% (P = 0.0002, n = 10), respectively. MTT staining was affected by d-glucose metabolism: absence of d-glucose, substitution of unmetabolized l-glucose for d-glucose or addition of 2-deoxy-d-glucose significantly decreased MTT staining by 44% (P < 0.01, n = 10), 45% (P < 0.01, n = 10) and 29% (P < 0.01, n = 10), respectively. Pyruvic acid failed to correct the MTT staining decrease induced by d-glucose deprivation and azide did not decrease MTT staining, suggesting that MTT staining could be independent of mitochondrial metabolism. Adding DPI significantly inhibited MTT staining by 25% (P < 0.001, n = 10), suggesting involvement of the pentose phosphate pathway's effectors. Compared with controls, VS4-vitrified/warmed pedicles showed significantly less MTT staining (-30%, P < 0.005, n = 10), with unstained foci, whereas unvitrified VS4-exposed pedicles showed no difference.

CONCLUSIONS

MTT can serve as a qualitative and quantitative vascular viability marker.VS4 vitrification caused alterations in ovarian vascular metabolism. MTT staining should allow accurate comparisons of whole-organ cryoprotection protocols.

Slow-controlled freezing versus speed-cooling for cryopreservation of whole guinea pig ovaries

The objective of this study was to evaluate the feasibility of whole-ovary perfusion, and to compare the effects of speed-cooling and slow-controlled freezing of whole guinea pig ovaries. Slow-freezing and speed-cooling procedures were performed after perfusion of guinea pig ovaries with cryoprotectants. Ink perfused via the vascular pedicles was present in the microvessels around various follicles at various stages of development in the cortical and medullar regions, thereby confirming that perfusion was effective. Vascular damage was essentially confined to the cannulated artery. Based on histological examination, there were (mean ± SEM) 93.1 ± 4.2, 79.0 ± 2.0, and 54.7 ± 8.5% healthy follicles in the fresh, slow-freezing and speed-cooling groups, respectively (each group differed from the other two, P < 0.05). Trypan blue staining of isolated follicles confirmed that cellular damage was greater following speed-cooling than slow-freezing (58.6 vs 29.2%, P < 0.05). Based on a TUNEL assay, speed-cooling caused more apoptotic granulosa and theca cells in antral follicles than slow-freezing. In conclusion, the present study provided evidence that guinea pig whole ovaries could be perfused with cryoprotectant and cryopreserved in vitro. Furthermore, the slow-freezing protocol resulted in less cellular damage in thawed tissues than speed-cooling.

Effects of cooling rates and ice-seeding temperatures on the cryopreservation of whole ovaries

PURPOSE

The aim of this study was to detect the effects of different cooling rates and different ice-seeding temperatures on the cryopreservation of whole ovaries.

METHODS

Cow whole ovaries were slowly frozen using different protocols with different cooling rates and different ice-seeding temperatures. Follicular viability was assessed using the trypan blue test; the percentage of morphologically normal primordial follicles and the follicular densities of grafts were measured.

RESULTS

Protocol IIb was most effective protocol. Protocol Ib was more effective than protocol Ia and protocol Ic, and protocol IIIb was more effective than protocol IIIa and protocol IIIc.

CONCLUSIONS

Protocol IIb (the cooling rate was 0.2°C/min, and the ice-seeding temperature was -5°C) was appropriate for slow freezing of cow whole ovaries.

Cryopreservation of whole ovaries with vascular pedicles: vitrification or conventional freezing?

PURPOSE

To compare the efficacy of vitrification and conventional freezing of whole ovaries.

METHODS

Ovaries obtained from 5-year-old female bovines were cryopreserved by conventional freezing, rapid freezing and vitrification. The ovarian cortical strips were cryopreserved by conventional freezing. Follicular viability was assessed using the trypan blue test; the percentage of morphologically normal primordial follicles, hormones concentrations in the culture supernatants, and lactate dehyrogenase levels were measured.

RESULTS

The efficacy of cryopreservation of whole ovaries by vitrification was higher than those by conventional freezing and rapid freezing. Conventional freezing of ovarian cortical strips was more effective than cryopreservation of whole ovaries by conventional freezing, rapid freezing, and vitrification.

CONCLUSIONS

Vitrification seems to be more suitable than conventional freezing for cryopreservation of whole ovaries. However, further studies are required to improve the efficacy of vitrifying whole ovaries.

[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.

Time to re-think: ovarian tissue transplantation versus whole ovary transplantation

Transplantation of cryobanked ovarian tissue is a promising strategy to restore fertility in cancer patients. However, ischaemia following ovarian tissue grafting can lead to significant follicular loss. Transplantation of the whole ovary by vascular anastomosis has been considered as a method of preventing ischaemic damage that occurs with avascular transplantation of ovarian tissue. Even so, the unavailability of the cryotechnology for whole organs can be a major barrier to whole ovary transplantation. Severe cryoinjury will cause not only follicular death but also irreversible damage to the vascular system of the ovary. Damaged ovarian vasculatures can induce thromboembolism after transplantation which leads to severe tissue ischaemia and follicular loss. As a consequence, follicular loss after the frozen-thawed whole ovary was transplanted with microsurgical vascular anastomosis has been shown to be as severe as that which occurred after ovarian tissue was grafted. In addition, the risk of cancer cell reintroduction can be potentially higher with whole ovary transplantation with vascular anastomosis. The safety and efficacy of the new procedure should be proven before any further clinical applications take place. Nevertheless, research on whole ovary cryopreservation should not be discouraged.

Orthotopic and heterotopic ovarian tissue transplantation

BACKGROUND

Transplantation of ovarian tissue is, at present, the only clinical option available to restore fertility using cryopreserved ovarian tissue. More than 30 transplantations of cryopreserved tissue have been reported, and six babies have been born, worldwide, following this procedure. Despite these encouraging results, it is essential to optimize the procedure by improving the follicular survival, confirming safety and developing alternatives. Here, we review the different factors affecting follicular survival and growth after grafting.

METHODS

Relevant studies were identified by searching Pubmed up to January 2009 with English language limitation. The following key words were used: (ovarian tissue or whole ovary) AND (transplantation) AND (cryopreservation or pregnancy). Using the literature and personal experience, we examined relevant data on the different exogenous and clinical factors affecting follicular development after grafting.

RESULTS

Clinical factors such as the patient's age and the transplantation sites influenced the lifespan of the graft. A heterotopic transplantation site is not optimal but offers some advantages and it may also promote the hormonal environment after a combined heterotopic and orthotopic transplantation. Exogenous factors such as antioxidants, growth factors or hormones were tested to improve follicular survival; however, their efficiency regarding further follicular development and fertility potential remains to be established.

CONCLUSION

Additional evidence is required to define optimal conditions for ovarian tissue transplantation. Alternatives such as whole ovary or isolated follicles transplantations require further investigation but are likely to be successful in humans in the future.