Cryopreservation of human ovarian tissue

Ethical, legal, social, and policy issues of ovarian tissue cryopreservation in prepubertal girls: a critical interpretive review

PURPOSE

Despite the increasing number of childhood cancer survivors, significant advances in ovarian tissue cryopreservation (OTC) technique and medical societies' recommendations, fertility preservation (FP) and FP discussions are not always offered as a standard of care in the pediatric context. The aim of this literature review is to understand what ethical, legal, social, and policy issues may influence the provision of FP by OTC in prepubertal girls with cancer.

METHODS

A critical interpretive review of peer-reviewed papers published between 2000 and January 2023 was conducted, guided by the McDougall's version of the critical interpretive synthesis (Dixon-Woods), to capture recurring concepts, principles, and arguments regarding FP by OTC for prepubertal girls.

RESULTS

Of 931 potentially relevant papers, 162 were included in our analysis. Data were grouped into seven thematic categories: (1) risks of the procedure, (2) unique decision-making issues in pediatric oncofertility, (3) counseling, (4) cultural and cost issues, and (5) disposition of cryopreserved reproductive tissue.

CONCLUSION

This first literature review focusing on ethical, legal, social, and policy issues surrounding OTC in prepubertal girls highlights concerns in the oncofertility debate. Although OTC is no longer experimental as of December 2019, these issues could limit its availability and the child's future reproductive autonomy. This review concludes that specific actions must be provided to enable the offer of FP, such as supporting families' decision-making in this unique and complex context, and providing pediatric patients universal and full access to free or highly subsidized OTC.

Cryopreservation of ovarian tissue after pretreatment with a gonadotropin-releasing hormone agonist

Purpose

The purpose of this study was to investigate whether slow-rate freezing or vitrification is better for cryopreservation of ovary tissues pretreated with gonadotropin-releasing hormone agonist.

Methods

In this nonclinical study performed in rats, leuprorelin acetate was administered to female Wistar rats, aged 6-8 weeks. After confirming arrest of the estrous cycle by examination of vaginal smears, ovarian tissue was cryopreserved by vitrification and slow-rate freezing prior to thawing and autotransplantation. The time required for estrous cycle recovery was assessed from vaginal smears in each group starting from day 1 of transplantation. Estradiol levels were also monitored after transplantation.

Results

The estrous cycle recovered after transplantation of ovarian tissue frozen by either method, but recovery was significantly faster after transplantation of vitrified tissue. The estradiol level also recovered by 10 days after transplantation.

Conclusions

Ovarian function was restored after transplantation of tissue preserved by either vitrification or slow-rate freezing after pretreatment with leuprorelin acetate. This method may be applicable for patients scheduled to undergo cryopreservation of ovarian tissue before chemotherapy.

At what age can human oocytes be obtained?

OBJECTIVE

To determine whether oocyte retrieval and in vitro maturation (IVM) is effective in girls undergoing fertility preservation before cancer treatment.

DESIGN

Cohort study.

SETTING

Tertiary university medical center.

PATIENT(S)

Patients <or=20 years old before gonadotoxic chemotherapy undergoing ovarian cortex cryopreservation.

INTERVENTION(S)

Before ovarian cortex cryopreservation, oocytes in all observed follicles were aspirated, matured in vitro, and cryopreserved.

MAIN OUTCOME MEASURE(S)

Maturation of oocytes.

RESULT(S)

One hundred seventy-nine oocytes were detected in 17/19 patients (89%) aged 5-20 years. We found 7, 8, and 17 oocytes in patients 5, 8, and 10 years old, respectively. The median number of oocytes per patient was 9 (0-37). Maturation rate was 45/133 oocytes (34%). In total, 81 oocytes were cryopreserved. We cryopreserved 4 of 12 detected, 4 of 9 detected, 1 of 8 detected, and 4 of 9 detected IVM oocytes for patients aged 5-10, 11-14, 15-17, and 18-20 years old, respectively.

CONCLUSION(S)

Patients undergoing ovarian cryopreservation could benefit from supplementary oocyte aspiration from the cortex. Surprisingly, oocytes were detected even in young premenarcheal girls. The number of oocytes detected, matured, and cryopreserved was not age dependent. Retrieved oocytes can be matured in vitro and cryopreserved. Because no pregnancy has yet resulted from this procedure it should be considered to be experimental. We describe the youngest patients to undergo ovum collection, IVM, and oocyte cryopreservation.

Feasibility of ovarian tissue cryopreservation for prepubertal females with cancer

BACKGROUND

Loss of fertility is one of the long-term adverse effects of high-dose chemotherapy or total body irradiation for cancer, even in children. Ovarian tissue cryopreservation (OTC) may make it possible for survivors of childhood cancer to have children. We evaluated the feasibility of this technique for prepubertal girls.

METHODS

Between September 2000 and February 2005, 49 prepubertal girls were referred to the Reproductive Biology Unit for OTC before sterilizing treatment.

RESULTS

One ovary each was collected from 47 patients, by laparoscopy in 24 patients and laporotomy in the others. In 16 cases, the ovary was harvested during laparotomy to resect a residual abdominal tumor. No complications occurred after operations. Ovarian tissue was frozen by a slow-cooling protocol, using DMSO and sucrose as cryoprotectants. An mean of 17.6 +/- 6.5 ovarian tissue fragments was cryopreserved per patient. Follicle concentration was evaluated histologically for 46 patients and a strong correlation was found between age and follicular density. None of the cases had visible ovarian tumor components. Ovarian cryopreservation was not carried out for two patients.

CONCLUSION

The cryopreservation of ovarian tissue could be systematically offered even to prepubertal girls at risk of sterility due to gonadotoxic treatment.

Gynaecologic concerns for young women exposed to gonadotoxic chemotherapy

PURPOSE OF REVIEW

Due to the improved long-term survival of adolescents and young women with systemic malignancies such as lymphomas and leukaemia undergoing gonadotoxic chemotherapy, preservation of future fertility has been the focus of recent ubiquitous interest. This review summarizes, in brief, the recent progress in the various attempts to prevent premature ovarian failure in these young women with unconsumed fertility potential.

RECENT FINDINGS

The investigational endeavours of ovarian cryopreservation await the clinical experience of auto- or xenotransplantation, or in-vitro maturation of thawed primordial follicles, and in-vitro fertilization. Although promising, this procedure is not available yet. Moreover, the risk of possible reimplantation of malignant stem cells with the thawed cryopreserved ovary has been highlighted following experimental animal observations. The gonadotropin-releasing hormone agonist has been efficient in primates in a prospective study, and in young women in several nonrandomized series. The disruption of the acid sphingomyelinase gene, or sphingosine-1-phosphate, in rodents can prevent follicle destruction by ionizing radiation, possibly indicating in-vivo protection in cancer patients at risk of iatrogenic sterilization.

SUMMARY

The recent enormous scientific advance lends hope that the future may hold answers to the questions regarding safety and efficiency of oocyte, follicle, or ovarian tissue cryopreservation, and the most efficient means of using the thawed tissue - auto-, hetero-, or xenotransplantation versus IVM on the one hand, and in-vivo pharmacological attempts to minimize follicle depletion by gonadotropin-releasing hormone agonist or other modalities on the other hand. Until then, a combination of all the clinically available modalities should be offered to these young women with unconsumed fertility potential who face gonadotoxic therapy.

Fertility of mice following receipt of ovaries slow cooled in dimethyl sulphoxide or ethylene glycol is largely independent of cryopreservation equilibration time and temperature

Cryopreservation procedures generally depend on both the cryoprotectant used and the equilibration conditions to which the material is exposed. The aim of the present study was to examine the effect of cryoprotectants (dimethyl sulphoxide (DMSO) and ethylene glycol (EG)) and equilibration conditions (0, 30 or 120 min at 0°C or 120 min at room temperature) on the fertility of mice receiving cryopreserved mouse ovaries. The study compared the fertility of cryopreserved Day 14 mouse pup ovaries following grafting to adult recipient mice for 4 months. There was no effect of the cryoprotectant or equilibration condition used on the interval to the first plugging/mating or on the interval to the birth of the first litter, the size of litters, the number of litters produced or the total number of offspring produced. Despite this, when compared with control females (untreated, sham and fresh transplant) the cryopreservation and transplantation procedures delayed fertility. However, the size of litters was equivalent for all cryopreserved and control groups (P > 0.05). The results show that, for the equilibration conditions examined, DMSO and EG are equally efficient cryoprotective agents for mouse ovarian tissue.

Fertility after treatment for Hodgkin's disease

BACKGROUND

The investigational endeavors of ovarian cryopreservation await the clinical experience of auto- or xenotransplantation, in vitro maturation of thawed primordial follicles, their in vitro fertilization and embryo transfer. Although promising, this experience is not yet available. Moreover, the risk of possible reimplantation of malignant stem cells with the thawed cryoperserved ovary has been raised following experimental animal observations. Therefore, until these innovative endeavors prove successful, we have attempted to minimize the gonadotoxic effect of chemotherapy by the co-treatment with a gonadotropin-releasing hormone agonistic analog (GnRH-a) to induce a temporary prepubertal milieu. The immunoreactive inhibin-A and -B in these patients was measured before, during and following the gonadotoxic chemotherapy.

METHODS

A prospective clinical protocol was undertaken in 60 women aged 15-40 years with lymphoma, 10 with leukemia and 10 undergoing chemotherapeutic treatments for non-malignant diseases such as systemic lupus erythematosus or other autoimmune diseases. A monthly injection of depot D-TRP(6)-GnRH-a was administered from before starting the chemotherapy until its conclusion, up to a maximum of 6 months. Hormonal profile [follicle-stimulating hormone (FSH), luteinizing hormone (LH), E2, T, P4, insulin-like growth factor (IGF)-1, IGF-BP3 and prolactin) was taken before starting the GnRH-a/chemotherapy co-treatment, and monthly thereafter until resumtion of spontaneous ovulation. This group was compared with a control group of 60 women who have been treated with similar chemotherapy.

RESULTS

Whereas all but three (40, 36 and 34 year old) of the surviving patients within the GnRH-a/ chemotherapy co-treatment group resumed spontaneous ovulation and menses within 12 months, less than half of the patients in the 'control' group (chemotherapy without GnRH-a co-treatment) resumed ovarian function and regular cyclic activity (P <0.05). The remaining 55% experienced premature ovarian failure (POF). Temporarily increased FSH concentrations were experienced by about one-third of the patients resuming cyclic ovarian function, suggesting reversible ovarian damage in a larger proportion of women than those experiencing POF. Inhibin-A and -B decreased during the GnRH-a/ chemotherapy co-treatment but increased to normal levels in patients who resumed regular ovarian cyclicity, and/or spontaneously conceived, as compared with low levels in those who developed POF.

CONCLUSIONS

If these preliminary data are consisent in a larger group of patients, GnRH-a co-treatment should be considered in every woman of reproductive age receiving chemotherapy, in addition to assisted reproductive technologies and the investigation into ovarian cryopreservation for future in vitro maturation, autotransplantation or xenotransplantation.