The safety of transplanting cryopreserved ovarian tissue in cancer patients: a review of the literature

BACKGROUND

Transplantation of frozen/thawed ovarian tissue from patients with a malignant condition is associated with a risk of re-introduction of the disease as the tissue usually is removed before anti-cancer therapy and may thus contain malignant cells. We review studies investigating the presence of malignant cells in cryopreserved ovarian tissue from patients with malignant disease and based on the strength of the evidence, recommendations for transplantations are proposed.

MATERIALS AND METHODS

A systematic review of the literature. All peer reviewed studies evaluating the presence of malignant cells in cryopreserved human ovarian tissue were included. Data were searched in Pubmed and Embase with no language restrictions.

RESULTS

The majority of the reviewed papers were casuistic reports and few of the included papers were specifically designed to search for malignant cells. Ovarian tissue from 422 patients has been subject to testing for malignant cells by imaging, histology, immunohistochemistry, molecular biology, animal- or clinical transplantation. In 31 (7 %) of the cases the applied test raised suspicion of malignant cell infiltration. No transplantation-related relapse of cancer has been reported after 33 transplantations of frozen/thawed ovarian cortex.

CONCLUSION

The quality and strength of the evidence is generally low and prospective studies are needed. The risk of re-introducing a malignant condition when transplanting ovarian tissue depends on the particular disease. Based on the available data, the risk was estimated: Leukaemia: HIGH. Gastrointestinal cancers: MODERATE. Breast cancer, sarcomas of the bone and connective tissue, gynaecological cancers, Hodgkin's and Non-Hodgkin's Lymphoma: LOW.

FSH prevents depletion of the resting follicle pool by promoting follicular number and morphology in fresh and cryopreserved primate ovarian tissues following xenografting

BACKGROUND

Cryopreservation and transplantation of ovarian tissue is one option for re-establishing ovarian function, but optimal conditions for graft sustainment and follicular survival are still considered experimental. The present study aims to analyze the effect of FSH treatment on the resting follicle pool in fresh and cryopreserved primate ovarian tissues following xenografting.

METHODS

Ovarian tissues from adult marmosets were grafted freshly or following cryopreservation to ovarectomized nude mice treated with FSH 25 IU twice daily post transplantation or left untreated as controls. Grafts were retrieved 2 or 4 weeks after transplantation to evaluate the number and morphological appearance of follicles.

RESULTS

Early start of FSH treatment within 1 week following transplantation partly prevents primordial follicle loss in fresh and frozen-thawed tissues, whereas after a 3 weeks time interval this effect is present only in fresh tissues. A similar positive effect of early, but not later FSH treatment on primary follicles is seen in fresh tissues compared to only marginal effects in frozen-thawed tissues. The percentage of morphologically normal follicles is generally increased in FSH treated tissues, whereas the percentage of primary follicles over all primordial and primary follicles is increased by FSH only in freshly-grafted tissues.

CONCLUSIONS

FSH treatment alleviates depletion of the resting follicle pool and promotes normal follicular morphology both in freshly and frozen-thawed grafted tissues. In previously cryopreserved tissues, applying to most of the tissues intended for clinical use in fertility preservation attempts, its positive effect on primordial follicle numbers and potential graft sustainment is dependent on an early start of treatment within one week of transplantation.

Preservation of ovarian function and fertility despite gonadotoxic chemotherapy

The author aims to review the various strategies and avenues for fertility preservation despite gonadotoxic chemotherapy in young women. The recent increase in the survival of young patients has increased the worldwide attempts toward fertility preservation. The currently utilized methods are sperm cryopreservation and banking in male patients, and cryopreservation of embryos, unfertilized oocytes and ovarian tissue, as well as administration of gonadotropin-releasing hormone agonists (GnRH-a) before and during the gonadotoxic chemotherapy in young female patients. For those patients in whom pelvic irradiation is planned, ovariopexy is suggested. Since none of the suggested methods are ideal and none guarantees future fertility, a combination of several methods may optimize patients' chance of fertility preservation. GnRH-a co-treatment may reduce ovarian damage significantly in female patients treated with gonadotoxic chemotherapy. GnRH-a should be considered for women of reproductive age receiving gonadotoxic chemotherapy in addition to assisted reproduction and cryopreservation of embryos, oocytes and ovarian tissue.

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.

Fertility considerations in young women with hematological malignancies

The need for practice guidelines for fertility preservation in young women with hematological malignancies has been increased. To develop recommendations, publications relevant to fertility preservation and hematological cancers were identified through a PubMed database search and reviewed systematically, focusing on the effects of oncological treatments on fertility as well as on the efficacy, feasibility and risks of existing fertility preservation methods.

Evaluation of the ovarian reserve in women transplanted with frozen and thawed ovarian cortical tissue

OBJECTIVE

To investigate ovarian reserve and ovarian function in women transplanted with frozen/thawed ovarian tissue.

DESIGN

Retrospective cohort study.

SETTING

University hospital.

PATIENT(S)

18 women transplanted with their own frozen/thawed ovarian tissue.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Levels of antimüllerian hormone (AMH), duration of function of the transplanted ovarian tissue, outcome of assisted reproduction.

RESULT(S)

Of the 18 women who received transplanted ovarian tissue, levels of AMH were measured in 12 women; AMH never exceed a concentration of 1 ng/mL, and in several cases they were below the detection limit of the assay in combination with regular menstrual cycles. Two women with AMH below the detection limit conceived spontaneously. The duration of function of the transplants was between 9 months and 7 years and still functioning. Twelve women received assisted reproduction therapy; in 72 cycles, 65 oocytes were retrieved. The pregnancy rate and live-birth rate per cycle were 6.9% (5 of 72) and 2.8% (2 of 72), respectively.

CONCLUSION(S)

The relatively poor outcome of assisted reproduction in women transplanted with frozen/thawed ovarian tissue may reflect reduced follicular selection rather than defective or aged oocytes. In normal women, reduced follicular selection with age may be part of explaining the decline in female fecundity with increasing age.

Effects of HMG on revascularization and follicular survival in heterotopic autotransplants of mouse ovarian tissue

Ovarian tissue transplantation is now considered as a procedure to preserve the fertility of young women patients undergoing cancer therapy. The present study investigated the effects and mechanism of human menopausal gonadotrophin (HMG) intervention on vascular remoulding in ovarian heterotopic autotransplantation. Ovaries of 8-week-old mice were cultured in vitro with different concentrations of HMG for 3h for measuring the expression of vascular endothelial growth factor (VEGF). The cultured ovaries were implanted under the kidney capsule and removed 24, 36, 48 h or 1 month after transplantation. Revascularization, fluid exudation and the number of surviving ovarian follicles were observed. The results showed that VEGF was increased 1.6-6.5 times in the HMG intervention groups. Revascularization appeared 24-36 h after transplantation and was earlier than that of the control. Fluid exudation increased incrementally with increasing HMG concentrations. The total number of surviving ovarian follicles was increased by 1.2-1.5 times in the HMG 0.15 IU/ml group as compared with the other groups 1 month after transplantation. It is concluded that intervention with HMG in vitro before transplantation could improve the blood supply reconstruction and survival of the autotransplanted ovarian follicles, which might be associated with increased VEGF expression.

Effect of cryopreservation and transplantation on the expression of kit ligand and anti-Mullerian hormone in human ovarian tissue

BACKGROUND

Although cryopreservation and transplantation of ovarian tissue represent a promising alternative to safeguard fertility in cancer patients, low recovery rates of oocytes aspirated from antral follicles and a significant number of empty follicles have been observed in women with transplanted frozen-thawed ovarian tissue. In order to understand how freezing and/or grafting may affect follicular development, the follicular expression of kit ligand (KL) and anti-Müllerian hormone (AMH), two key factors activating and inhibiting follicle growth, were assessed after long-term grafting in severe combined immunodeficient (SCID) mice.

METHODS

Ovarian biopsies from eight patients were used for fresh and frozen-thawed tissue xenografting in 13 SCID mice for a period of 28 weeks, including 2 weeks of gonadotrophin stimulation. KL, AMH and proliferating cell nuclear antigen (PCNA) immunostaining were quantified before and after grafting in the two treatment groups (fresh and frozen-thawed grafted ovarian tissue).

RESULTS

Lower expression of KL was found in primordial and primary follicles after grafting of both fresh and frozen-thawed tissue. Consistent expression of AMH was found in most growing follicles at a similar rate in both graft types. In fresh and frozen-thawed grafts, 13-14% of primordial follicles were PCNA-positive, indicating a similar maintenance of quiescent follicles despite follicle activation.

CONCLUSIONS

Grafting and/or gonadotrophin stimulation appear to affect the follicular expression of KL, which may alter oocyte quality. AMH expression in growing follicles after ovarian tissue transplantation may be one of the factors contributing to the preservation of resting follicles in 28-week-old grafts.

Chemotherapy and fertility

The overall increase in cancer prevalence and the significant increase in long-term survival have generated worldwide interest in preserving fertility in young women exposed to gonadotoxic chemo- and radiotherapy. Infertility represents one of the main long-term consequences of combination chemotherapy given for lymphoma, leukaemia and other malignancies in young women. The gonadotoxic effect of various chemotherapeutic agents is diverse, may involve a variety of pathophysiologic mechanisms, and is not unequivocally understood. Proliferating cells, such as in tissues with high turnover (i.e. bone marrow, gastrointestinal tract and growing ovarian follicles) are more vulnerable to the toxic effect of alkylating agents. These agents may also be cytotoxic to cells at rest, as they are not cell-cycle specific. Alkylating agents, the most gonadotoxic chemotherapeutic medications, cause dose-dependent, direct destruction of oocytes and follicular depletion, and may bring about cortical fibrosis and ovarian blood-vessel damage. The reported rate of premature ovarian failure after various diseases and chemotherapeutic protocols differ enormously, and depend mainly on the chemotherapeutic protocol used and age range of the woman. Several options have been proposed for preserving female fertility, despite gonadotoxic chemotherapy: ovarian transposition, cryopreservation of embryos, unfertilised metaphase-II oocytes and ovarian tissue, and administration of gonadotropin-releasing hormone agonistic analogs in an attempt to decrease the gonadotoxic effects of chemotherapy by simulating a prepubertal hormonal milieu. None of these methods is ideal and none guarantees future fertility in all survivors; therefore, a combination of methods is recommended for maximising women's chances of future fertility.

Impact of freezing and thawing of human ovarian tissue on follicular growth after long-term xenotransplantation

PURPOSE

To assess follicular growth after xenografting in order to understand how freezing and/or grafting may affect follicular development.

METHODS

Human ovarian biopsies were used for fresh and frozen-thawed xenografting to SCID mice. After xenotransplantation, follicular morphology and proportion, oocyte and follicle diameter, and quantitative and qualitative parameters of antral follicles were analyzed.

RESULTS

The proportion of growing follicles was significantly higher in grafted than non-grafted ovarian tissue. Follicular growth to the antral stage was observed and there was no significant difference in oocyte or follicle diameter in fresh or frozen-thawed grafts. Although no significant difference was observed in antral area or zona pellucida thickness, the theca layer in antral follicles from frozen-thawed grafted tissue was found to be significantly thinner than in fresh grafts.

CONCLUSION

Antral follicles obtained after grafting of frozen-thawed human ovarian tissue showed a thinner theca cell layer compared to those from fresh grafts, which could affect follicular development and function. Further studies are nevertheless warranted to confirm the identity of theca cells and assess if they retain the ability to respond to luteinizing hormone and produce androgens.

Fertility preservation in girls and young women

There is increasing interest and experience in the options available to preserve fertility in those about to undergo potentially gonadotoxic chemotherapy or radiation therapy, usually related to treatment for cancer. Recent years have seen the development of methods for prepubertal girls, female adolescents and adult women, although these remain less established than sperm cryopreservation for men. At present, the options for prepubertal boys remain experimental. Embryo cryopreservation following ovarian stimulation and IVF is a routine procedure technically and its success in the management of infertility is established. However, there are no data on uptake or success rates in the context of fertility preservation in women with cancer. Oocyte cryopreservation is technically challenging and requires ovarian stimulation, thus potentially resulting in a delay in cancer treatment. Oocyte vitrification offers increased success rates in comparison with slow freezing; however, this approach is also limited by the number of oocytes that can be obtained. The third possibility, ovarian tissue cryopreservation, can be performed without significant delay and is the only option for prepubertal girls. Worldwide, a small number of children have been born following reimplantation of frozen/thawed ovarian tissue. It is clear that fertility preservation is important for some girls and young women facing treatments that will compromise their fertility, but the availability of all approaches varies widely. Effective approaches for prepubertal boys are also required.

Effect of vitrification of feline ovarian cortex on follicular and oocyte quality and competence

Cryopreservation of ovarian cortex has important implications in the preservation of fertility and biodiversity in animal species. Slow freezing of cat ovarian tissue resulted in the preservation of follicular morphology and in the follicular development after xenografting. Vitrification has been recently applied to ovarian tissues of different species, but no information is available on the effect of this method on feline ovarian cortex. Moreover, meiotic competence of fully grown oocytes isolated from cryopreserved tissue has not been reported. The aim of this study was to evaluate the effect of vitrification of feline ovarian cortex on follicular morphology and oocyte integrity, as well as meiotic competence. A total of 352 fragments (1.5-2 mm(3) ) were obtained from ovarian cortical tissues: 176 were vitrified and 176 were used fresh as control. Histological evaluation of fresh and vitrified fragments showed intact follicles after cryopreservation procedures with no statistically significant destructive effect from primordial to antral follicles. After IVM, oocytes collected from vitrified ovarian fragment showed a higher proportion of gametes arrested at germinal vesicle (GV) stage compared to those isolated from fresh control tissue (33.8% vs 2.9%; p < 0.001). However, oocytes isolated from vitrified tissues were able to resume meiosis, albeit at lower rate than those collected from fresh tissues (39.8% vs 85.9%; p < 0.00001). Vitrification induced changes in the organization of cytoskeletal elements (actin microfilaments and microtubules) of oocytes, but significantly only for actin network (p < 0.001). Finally, chromatin configuration within the GV was not affected by the cryopreservation procedure. Our study demonstrated that vitrification preserves the integrity of ovarian follicles and that oocytes retrieved from cryopreserved tissue maintain the capability of resuming meiosis. To our knowledge, this has not previously been reported in the cat.

Limited value of ovarian function markers following orthotopic transplantation of ovarian tissue after gonadotoxic treatment

CONTEXT

In young women, some treatments for cancer or other conditions (such as sickle cell anemia) may give rise to primary ovarian insufficiency. Ovarian transplantation is one of the available options for fertility preservation, with highly variable pregnancy rates.

OBJECTIVE

The objective of the study was to investigate markers of ovarian reserve and ovarian function in women up to 7 yr after orthotopic ovarian transplantation. Secondary objectives were to assess the relationship between markers of ovarian reserve and pregnancy rate along with the duration of ovarian function.

DESIGN

This was a prospective cohort study in 10 women, with a mean follow-up of 2.5 yr.

SETTING

The study was conducted at a university hospital in Brussels, Belgium.

PATIENTS

Patients included 10 women who were about to receive or had previously received gonadotoxic treatment. In seven women cryopreservation of ovarian tissue was performed before starting treatment. Subsequently autografts were orthotopically transplanted in these women. Three women, who had already developed primary ovarian insufficiency due to treatment, underwent orthotopic transplantation of ovarian allograft tissue originating from their human leukocyte antigen-compatible sisters.

MAIN OUTCOME MEASURES

Serum concentrations of FSH, LH, estradiol, inhibin B, and anti-Müllerian hormone (AMH) were measured.

RESULTS

On average, first menses took place after 4.7 months. Duration of graft functioning varied from 2 to more than 60 months. FSH concentrations remained elevated, whereas estradiol levels normalized and AMH was low to undetectable. Inhibin B varied among women and was not associated with the duration of ovarian function (hazard ratio 0.966, 95% confidence interval 0.881-1.059). Two spontaneous pregnancies occurred. Endocrine characteristics were not significantly different in these women.

CONCLUSIONS

Low AMH and inhibin B concentrations may suggest decreased ovarian reserve in women after ovarian transplantation. AMH and inhibin B levels may not be associated with the duration of ovarian graft function or probability to achieve a pregnancy.

Micro-organ ovarian transplantation enables pregnancy: a case report

A 19-year-old thalassemic woman had tissue from one of her ovaries cryopreserved prior to bone marrow transplantation, total body irradiation and sterilizing chemotherapy. As expected, premature ovarian failure resulted from this treatment. Transplantation of her thawed ovarian tissue resulted in return of menstrual cycling and the patient then underwent several IVF cycles. The patient, however, had poor ovarian response to hyperstimulation. We thus considered an alternative approach based on the observation that very thin ovarian fragments that preserve the basic ovarian structure [ovarian micro-organs (MOs)] induce angiogenesis and remained viable after autologous transplantation in animals. We report that preparation of autologous tiny ovarian fragments (MO)s and reimplantation into our patient resulted in IVF pregnancy and delivery of a healthy baby.

Children born after autotransplantation of cryopreserved ovarian tissue. a review of 13 live births

INTRODUCTION. Premature ovarian failure (POF) can occur naturally at an early age or be due to iatrogenic agents. Indeed, ovaries are very sensitive to cytotoxic treatment, especially to radiation and alkylating agents. METHODS. Several options are currently available to preserve fertility in cancer patients and allow them to conceive when they have overcome their disease: embryo cryopreservation, oocyte cryopreservation, and ovarian tissue cryopreservation. Cryopreservation of ovarian tissue is the only option available for pre-pubertal girls and women who cannot delay the start of chemotherapy. FINDINGS. Since the first live birth after autotransplantation of cryopreserved ovarian tissue in humans was reported in 2004, orthotopic reimplantation has led to the birth of 13 healthy babies. Restoration of ovarian activity and prognostic factors are evaluated by comparison with 7 cases of fresh ovarian tissue transplantation. We report 13 live births after orthotopic transplantation of frozen-thawed ovarian tissue in cancer patients (n = 8) and in patients treated with high doses of chemotherapy for benign diseases (n = 2) (microscopic polyangiitis, sickle cell anemia). INTERPRETATION. Based on our review, we believe that ovarian cortex cryopreservation, associated or not with cryopreservation of immature oocytes, should be offered before gonadotoxic chemotherapy in all cases where there is a high risk of POF and where emergency IVF is not possible.

Reimplantation of cryopreserved ovarian tissue from patients with acute lymphoblastic leukemia is potentially unsafe

Ovarian tissue cryopreservation is currently proposed to young cancer patients to preserve their fertility before radiochemotherapy. The potential risk is that the tissue might harbor malignant cells that could induce disease recurrence. We therefore decided to evaluate the presence of leukemic cells in cryopreserved ovarian tissue from 18 leukemic patients: 6 with chronic myeloid leukemia (CML) and 12 with acute lymphoblastic leukemia (ALL). In each case, histology, quantitative reverse-transcribed polymerase chain reaction (RT-PCR) and long-term (6 months) xenografting to immunodeficient mice were used. Histology did not identify any malignant cells in the ovarian tissue. By quantitative RT-PCR, 2 of 6 CML patients were positive for BCR-ABL in their ovarian tissue. Among the 12 ALL patients, 7 of the 10 with available molecular markers showed positive leukemic markers in their ovarian tissue (translocations or rearrangement genes). Four mice grafted with ovarian tissue from ALL patients developed intraperitoneal leukemic masses. In conclusion, this study demonstrates, by quantitative RT-PCR, ovarian contamination by malignant cells in acute as well as chronic leukemia, whereas histology fails to do so. Moreover, chemotherapy before ovarian cryopreservation does not exclude malignant contamination. Finally, reimplantation of cryopreserved ovarian tissue from ALL and CML patients puts them at risk of disease recurrence.

Primary ovarian insufficiency

Primary ovarian insufficiency is a subclass of ovarian dysfunction in which the cause is within the ovary. In most cases, an unknown mechanism leads to premature exhaustion of the resting pool of primordial follicles. Primary ovarian insufficiency might also result from genetic defects, chemotherapy, radiotherapy, or surgery. The main symptom is absence of regular menstrual cycles, and the diagnosis is confirmed by detection of raised follicle-stimulating hormone and declined oestradiol concentrations in the serum, suggesting a primary ovarian defect. The disorder usually leads to sterility, and has a large effect on reproductive health when it arises at a young age. Fertility-preservation options can be offered to some patients with cancer and those at risk of early menopause, such as those with familial cases of primary ovarian insufficiency. Long-term deprivation of oestrogen has serious implications for female health in general; and for bone density, cardiovascular and neurological systems, wellbeing, and sexual health in particular.

Autotransplantation of cryopreserved ovarian tissue in 12 women with chemotherapy-induced premature ovarian failure: the Danish experience

OBJECTIVE

To describe a cohort of 12 Danish women who received autotransplantation of frozen-thawed cryopreserved ovarian tissue because of premature ovarian failure after cancer treatment.

DESIGN

Retrospective study.

SETTING

University hospitals.

PATIENT(S)

Twelve women with autotransplanted frozen-thawed ovarian tissue.

INTERVENTION(S)

Monitoring of hormonal parameters and results of 56 IVF cycles in 10 women.

MAIN OUTCOME MEASURE(S)

Levels of gonadotropins and sex steroids, functional life span of the grafts, and results of IVF.

RESULT(S)

All 12 women regained ovarian function between 8 and 26 weeks (mean 19 weeks) after transplantation. Ten women underwent a total of 56 IVF cycles, 76 follicles developed, 49 oocytes were aspirated, 18 were fertilized, and 16 embryos were transferred resulting in six pregnancies: two biochemical, one clinical that miscarried in week 7, and two ongoing resulting in the delivery of two healthy infants born at term to two women. One of these women subsequently conceived spontaneously and delivered another healthy infant. The life span of the transplanted tissue has been between 6 months and still functioning after 54 months.

CONCLUSION(S)

Autotransplantation consistently leads to recovery of ovarian function after treatment-induced ovarian failure. Four women became pregnant, after IVF or spontaneously, resulting in the delivery of three healthy infants.

Premature ovarian failure from current perspective

Premature ovarian failure (POF) is a syndrome characterised by amenorrhoea, hypoestrogenism and hypergonadotropinism before the age of 40. It is a disorder affecting approximately 1% of women <40 years, 1/1,000 women by the age of 30 and 1/10,000 women by the age of 20. POF is not merely an early menopause. Up to 50% of the patients with POF will have intermittent and unpredictable ovarian function which may persist for some years. Heterogeneity of POF is also reflected by the variety of possible causes, including autoimmunity, toxics, drugs, radiation, infectious as well as genetic defects. HRT remains the cornerstone of treatment and the only proven method of achieving pregnancy in these patients is by ovum donation.

Immunohistochemical localization of growth factors after cryopreservation and 3 weeks' xenotransplantation of human ovarian tissue

OBJECTIVE

To compare early follicular growth after fresh and frozen-thawed human ovarian tissue xenografting and to investigate whether expression of c-kit, kit ligand (KL), and growth differentiation factor-9 (GDF-9) is maintained after freezing and xenografting of human ovarian tissue.

DESIGN

Prospective experimental study.

SETTING

Gynecology research unit in a university hospital.

ANIMAL(S)

Ten nude (Swiss nu/nu) 6-week-old female mice.

INTERVENTION(S)

The ovarian biopsy samples were obtained from six women, aged 20 to 30 years. Fresh and frozen-thawed ovarian fragments intraperitoneally grafted into nude mice for 3 weeks.

MAIN OUTCOME MEASURE(S)

Histologic analysis and immunohistochemical evaluation of c-kit, KL, and GDF-9 expression before and after grafting.

RESULT(S)

The integrity and proportion of growing follicles increased similarly in both fresh (64%) and frozen-thawed (59%) xenografts compared with non-grafted tissue (fresh: 40%; frozen-thawed: 21%). Both C-kit and KL staining were detected in the oocytes and granulosa cells of preantral follicles, and GDF-9 expression was observed in the oocytes of preantral follicles in all groups.

CONCLUSION(S)

Freezing does not appear to have a major impact on early follicular growth after transplantation. This study shows, for the first time, expression of c-kit, KL, and GDF-9 in human preantral follicles after ovarian tissue cryopreservation and xenotransplantation.

Current achievements and future research directions in ovarian tissue culture, in vitro follicle development and transplantation: implications for fertility preservation

BACKGROUND Female cancer patients are offered 'banking' of gametes before starting fertility-threatening cancer therapy. Transplants of fresh and frozen ovarian tissue between healthy fertile and infertile women have demonstrated the utility of the tissue banked for restoration of endocrine and fertility function. Additional methods, like follicle culture and isolated follicle transplantation, are in development. METHODS Specialist reproductive medicine scientists and clinicians with complementary expertise in ovarian tissue culture and transplantation presented relevant published literature in their field of expertise and also unpublished promising data for discussion. As the major aims were to identify the current gaps prohibiting advancement, to share technical experience and to orient new research, contributors were allowed to provide their opinioned expert views on future research. RESULTS Normal healthy children have been born in cancer survivors after orthotopic transplantation of their cryopreserved ovarian tissue. Longevity of the graft might be optimized by using new vitrification techniques and by promoting rapid revascularization of the graft. For the in vitro culture of follicles, a successive battery of culture methods including the use of defined media, growth factors and three-dimensional extracellular matrix support might overcome growth arrest of the follicles. Molecular methods and immunoassay can evaluate stage of maturation and guide adequate differentiation. Large animals, including non-human primates, are essential working models. CONCLUSIONS Experiments on ovarian tissue from non-human primate models and from consenting fertile and infertile patients benefit from a multidisciplinary approach. The new discipline of oncofertility requires professionalization, multidisciplinarity and mobilization of funding for basic and translational research.

Markers of growth and development in primate primordial follicles are preserved after slow cryopreservation

OBJECTIVE

To investigate the effect of slow cryopreservation on the morphology and function of primate primordial follicles within ovarian tissue slices.

DESIGN

Fresh monkey ovarian tissue was frozen by slow cryopreservation and thawed for analysis of morphologic and functional parameters.

SETTING

University-affiliated laboratory.

ANIMALS

Rhesus monkey ovarian tissue.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Histologic analysis, follicle counting, assessment of protein abundance and localization.

RESULT(S)

After freezing and thawing, 89% of the primordial follicles maintained their laminar-based architecture, with sizes close to those of fresh fixed follicles. Molecular markers of early follicle health (activin subunits and the phosphorylated form of the signaling protein Smad2 [pSmad2]) were present in fresh and frozen-thawed primordial follicles. Stroma cells, but not follicles, had a higher level of TUNEL staining. Granulosa cells within the follicles of frozen-thawed ovarian tissue cultured for 48 hours had the capacity to proliferate and sustained expression of the activin subunits and nuclear pSmad2.

CONCLUSION(S)

This study provides evidence that markers of early follicle growth and development are preserved after slow cryopreservation and thaw, with little effect on follicle morphology and function.

Fertility preservation in girls during childhood: is it feasible, efficient and safe and to whom should it be proposed?

BACKGROUND

In prepubertal and adolescent girls, fertility may be impaired by gonadotoxic treatments, repeat ovarian surgery or genetic disorders. Cryopreservation of ovarian cortex is an existing option to preserve fertility in these young girls at risk of premature ovarian failure (POF). The efficacy, feasibility and risks of ovarian cryopreservation in children must be assessed in order to validate the technique.

METHODS

Here, we conducted a review of ovarian cryopreservation in adults and, more specifically, in children using the PubMed databases. In addition, our own experience with ovarian cryopreservation in children was evaluated and compared with the literature.

RESULTS

Analysis of the literature and six published series on ovarian cryopreservation in children, as well as our own series of 58 cases, show that there is no reason to doubt its efficacy in this young population. However, no consensus has yet been reached on the indications for the technique. Indeed, with existing models, the real risk of POF may be over- or underestimated.

CONCLUSION

Our review suggests that ovarian cortex cryopreservation is feasible and as safe as comparable operative procedures in children. Although no births have yet resulted from freeze-thawing of prepubertal ovarian cortex, the results of this approach in adults are encouraging. However, the absence of consensus on the indications for fertility preservation, as well as the optimal timing and quantity of ovarian cortex for cryopreservation, should be taken into consideration when discussing fertility issues with girls at risk of POF and their parents.