In-vitro maturation of oocytes recovered during cryopreservation of pre-pubertal girls undergoing fertility preservation

Restoring Ovarian Fertility and Hormone Function: Recent Advancements, Ongoing Efforts and Future Applications

The last 20 years have seen substantial improvements in fertility and hormone preservation and restoration technologies for a growing number of cancer survivors. However, further advancements are required to fill the gaps for those who cannot use current technologies or to improve the efficacy and longevity of current fertility and hormone restoration technologies. Ovarian tissue cryopreservation (OTC) followed by ovarian tissue transplantation (OTT) offers those unable to undergo ovarian stimulation for egg retrieval and cryopreservation an option that restores both fertility and hormone function. However, those with metastatic disease in their ovaries are unable to transplant this tissue. Therefore, new technologies to produce good-quality eggs and restore long-term cyclic ovarian function are being investigated and developed to expand options for a variety of patients. This mini-review describes current and near future technologies including in vitro maturation, in vitro follicle growth and maturation, bioprosthetic ovaries, and stem cell applications in fertility restoration research by their proximity to clinical application.

FGF2, LIF, and IGF1 (FLI) supplementation during human in vitro maturation enhances markers of gamete competence

STUDY QUESTION

Does a chemically defined maturation medium supplemented with FGF2, LIF, and IGF1 (FLI) improve in vitro maturation (IVM) of cumulus-oocyte complexes (COCs) obtained from children, adolescents, and young adults undergoing ovarian tissue cryopreservation (OTC)?

SUMMARY ANSWER

Although FLI supplementation did not increase the incidence of oocyte meiotic maturation during human IVM, it significantly improved quality outcomes, including increased cumulus cell expansion and mitogen-activated protein kinase (MAPK) expression as well as enhanced transzonal projection retraction.

WHAT IS KNOWN ALREADY

During OTC, COCs, and denuded oocytes from small antral follicles are released into the processing media. Recovery and IVM of these COCs is emerging as a complementary technique to maximize the fertility preservation potential of the tissue. However, the success of IVM is low, especially in the pediatric population. Supplementation of IVM medium with FLI quadruples the efficiency of pig production through improved oocyte maturation, but whether a similar benefit occurs in humans has not been investigated.

STUDY DESIGN, SIZE, DURATION

This study enrolled 75 participants between January 2018 and December 2021 undergoing clinical fertility preservation through the Fertility & Hormone Preservation & Restoration Program at the Ann & Robert H. Lurie Children's Hospital of Chicago. Participants donated OTC media, accumulated during tissue processing, for research.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Participants who underwent OTC and include a pediatric population that encompassed children, adolescents, and young adults ≤22 years old. All participant COCs and denuded oocytes were recovered from media following ovarian tissue processing. IVM was then performed in either a standard medium (oocyte maturation medium) or one supplemented with FLI (FGF2; 40 ng/ml, LIF; 20 ng/ml, and IGF1; 20 ng/ml). IVM outcomes included meiotic progression, cumulus cell expansion, transzonal projection retraction, and detection of MAPK protein expression.

MAIN RESULTS AND THE ROLE OF CHANCE

The median age of participants was 6.3 years, with 65% of them classified as prepubertal by Tanner staging. Approximately 60% of participants had been exposed to chemotherapy and/or radiation prior to OTC. On average 4.7 ± 1 COCs and/or denuded oocytes per participant were recovered from the OTC media. COCs (N = 41) and denuded oocytes (N = 29) were used for IVM (42 h) in a standard or FLI-supplemented maturation medium. The incidence of meiotic maturation was similar between cohorts (COCs: 25.0% vs 28.6% metaphase II arrested eggs in Control vs FLI; denuded oocytes: 0% vs 5.3% in Control vs FLI). However, cumulus cell expansion was 1.9-fold greater in COCs matured in FLI-containing medium relative to Controls and transzonal projection retraction was more pronounced (2.45 ± 0.50 vs 1.16 ± 0.78 projections in Control vs FLIat 16 h). Additionally, MAPK expression was significantly higher in cumulus cells obtained from COCs matured in FLI medium for 16-18 h (chemiluminescence corrected area 621,678 vs 2,019,575 a.u., P = 0.03).

LIMITATIONS, REASONS FOR CAUTION

Our samples are from human participants who exhibited heterogeneity with respect to age, diagnosis, and previous treatment history. Future studies with larger sample sizes, including adult participants, are warranted to determine the mechanism by which FLI induces MAPK expression and activation. Moreover, studies that evaluate the developmental competence of eggs derived from FLI treatment, including assessment of embryos as outcome measures, will be required prior to clinical translation.

WIDER IMPLICATIONS OF THE FINDINGS

FLI supplementation may have a conserved beneficial effect on IVM for children, adolescents, and young adults spanning the agricultural setting to clinical fertility preservation.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by Department of Obstetrics and Gynecology startup funds (F.E.D.), Department of Surgery Faculty Practice Plan Grant and the Fertility & Hormone Preservation & Restoration Program at the Ann & Robert H. Lurie Children's Hospital of Chicago (M.M.L. and E.E.R.). M.M.L. is a Gesualdo Foundation Research Scholar. Y.Y.'s research is supported by the internal research funds provided by Colorado Center of Reproductive Medicine. Y.Y., L.D.S., R.M.R., and R.S.P. have a patent pending for FLI. The remaining authors have no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

Prior exposure to chemotherapy does not reduce the in vitro maturation potential of oocytes obtained from ovarian cortex in cancer patients

STUDY QUESTION

Does chemotherapy exposure affect IVM potential of immature oocytes retrieved from the ovarian cortex following ovarian tissue cryopreservation (OTC) for fertility preservation?

SUMMARY ANSWER

The IVM potential of oocyte retrieved from ovarian cortex following OTC is not affected by prior exposure to chemotherapy but primarily dependent on patient's age, while successful retrieval of immature oocytes from the ovarian tissue is negatively affected by chemotherapy and its timing.

WHAT IS KNOWN ALREADY

The potential and feasibility of IVM in premenarche patients was previously demonstrated, in smaller studies. The scarce data that exist on the IVM potential of oocytes retrieved during OTC following chemotherapy support the feasibility of this process, however, this was not previously shown in the premenarche cancer patients population or in larger cohorts.

STUDY DESIGN, SIZE, DURATION

A retrospective cohort study evaluating 229 cancer patients aged 1-39 years with attempted retrieval of oocytes from the ovarian tissue and the medium following OTC in a university affiliated fertility preservation unit between 2002 and 2021.

PARTICIPANTS/MATERIALS, SETTING, METHODS

A total of 172 chemotherapy naïve and 57 chemotherapy exposed patients aged 1-39 years underwent OTC in university affiliated tertiary infertility and IVF center. OTC and IVM outcomes were compared between the chemotherapy naïve and exposed groups. The main outcome measure was mean IVM rate per patient in the chemotherapy naïve and exposed groups, with subgroup analysis of a 1:1 chemotherapy exposed group matched for age at OTC and type of malignancy. We additionally analyzed premenarche and postmenarche patients' outcomes separately and investigated the effect of time from chemotherapy to IVM, malignancy type and chemotherapy regimen on oocyte number and IVM outcomes in the chemotherapy exposed group.

MAIN RESULTS AND THE ROLE OF CHANCE

While the number of retrieved oocytes and percentage of patients with at least one oocyte retrieved was higher in the chemotherapy naïve group (8.7 ± 7.9 versus 4.9 ± 5.6 oocytes and 87.2% versus 73.7%, P < 0.001 and P = 0.016, respectively), IVM rate and number of mature oocytes were comparable between the groups (29.0 ± 25.0% versus 28. 9 ± 29.2% and 2.8 ± 3.1 versus 2.2 ± 2.8, P = 0.979 and P = 0.203, respectively). Similar findings were shown in subgroup analyses for premenarche and postmenarche groups. The only parameter found to be independently associated with IVM rate in a multivariable model was menarche status (F = 8.91, P = 0.004). Logistic regression models similarly showed that past chemotherapy exposure is negatively associated with successful retrieval of oocytes while older age and menarche are predictive of successful IVM. An age and the type of malignancy matched (1:1) chemotherapy naïve and exposed groups were created (25 patients in each group). This comparison demonstrated similar IVM rate (35.4 ± 30.1% versus 31.0 ± 25.2%, P = 0.533) and number of matured oocytes (2.7 ± 3.0. versus 3.0 ± 3.9 oocytes, P = 0.772). Type of malignancy and chemotherapy regimen including alkylating agents were not associated with IVM rate.

LIMITATIONS, REASONS FOR CAUTION

This study's inherited retrospective design and the long study period carries the possible technological advancement and differences. The chemotherapy exposed group was relatively small and included different age groups. We could only evaluate the potential of the oocytes to reach metaphase II in vitro but not their fertilization potential or clinical outcomes.

WIDER IMPLICATIONS OF THE FINDINGS

IVM is feasible even after chemotherapy broadening the fertility preservation options of cancer patients. The use of IVM for fertility preservation, even after exposure to chemotherapy, should be further studied for optimal postchemotherapy timing safety and for the in vitro matured oocytes potential for fertilization.

STUDY FUNDING/COMPETING INTEREST(S)

No funding was received for this study by any of the authors. The authors report that no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

The Late Effects of Cancer Treatment on Female Fertility and the Current Status of Fertility Preservation-A Narrative Review

Fertility counseling should be offered to all individuals of young reproductive age early in the patient's trajectory following a cancer diagnosis. Systemic cancer treatment and radiotherapy often have an inherent gonadotoxic effect with the potential to induce permanent infertility and premature ovarian failure. For the best chances to preserve a patient's fertility potential and to improve future quality of life, fertility preservation methods should be applied before cancer treatment initiation, thus multidisciplinary team-work and timely referral to reproductive medicine centers specialized in fertility preservation is recommended. We aim to review the current clinical possibilities for fertility preservation and summarize how infertility, as a late effect of gonadotoxic treatment, affects the growing population of young female cancer survivors.

A Systematic Review of Ovarian Tissue Transplantation Outcomes by Ovarian Tissue Processing Size for Cryopreservation

Ovarian tissue cryopreservation (OTC) is the only pre-treatment option currently available to preserve fertility for prepubescent girls and patients who cannot undergo ovarian stimulation. Currently, there is no standardized method of processing ovarian tissue for cryopreservation, despite evidence that fragmentation of ovaries may trigger primordial follicle activation. Because fragmentation may influence ovarian transplant function, the purpose of this systematic review was (1) to identify the processing sizes and dimensions of ovarian tissue within sites around the world, and (2) to examine the reported outcomes of ovarian tissue transplantation including, reported duration of hormone restoration, pregnancy, and live birth. A total of 2,252 abstracts were screened against the inclusion criteria. In this systematic review, 103 studies were included for analysis of tissue processing size and 21 studies were included for analysis of ovarian transplantation outcomes. Only studies where ovarian tissue was cryopreserved (via slow freezing or vitrification) and transplanted orthotopically were included in the review. The size of cryopreserved ovarian tissue was categorized based on dimensions into strips, squares, and fragments. Of the 103 studies, 58 fertility preservation sites were identified that processed ovarian tissue into strips (62%), squares (25.8%), or fragments (31%). Ovarian tissue transplantation was performed in 92 participants that had ovarian tissue cryopreserved into strips (n = 51), squares (n = 37), and fragments (n = 4). All participants had ovarian tissue cryopreserved by slow freezing. The pregnancy rate was 81.3%, 45.5%, 66.7% in the strips, squares, fragment groups, respectively. The live birth rate was 56.3%, 18.2%, 66.7% in the strips, squares, fragment groups, respectively. The mean time from ovarian tissue transplantation to ovarian hormone restoration was 3.88 months, 3.56 months, and 3 months in the strips, squares, and fragments groups, respectively. There was no significant difference between the time of ovarian function' restoration and the size of ovarian tissue. Transplantation of ovarian tissue, regardless of its processing dimensions, restores ovarian hormone activity in the participants that were reported in the literature. More detailed information about the tissue processing size and outcomes post-transplant are required to identify a preferred or more successful processing method.

SYSTEMATIC REVIEW REGISTRATION

[https://www.crd.york.ac.uk], identifier [CRD42020189120].

Role of Stem Cells in the Ovarian Tissue Cryopreservation and Transplantation for Fertility Preservation

Although the cancer survival rate has increased, cancer treatments, including chemotherapy and radiotherapy, can cause ovarian failure and infertility in women of reproductive age. Preserving fertility throughout cancer treatment is critical for maintaining quality of life. Fertility experts should propose individualized fertility preservation methods based on the patient’s marital status, pubertal status, partner status, and the urgency of treatment. Widely practiced fertility preservation methods, including ovarian transposition and embryo and oocyte cryopreservation, are inappropriate for prepubertal girls or those needing urgent initiation of cancer treatment. Ovarian tissue cryopreservation and transplantation, an emerging new technology, may be a solution for these cancer patients. The use of stem cells in ovarian tissue cryopreservation and transplantation increases oxygenation, angiogenesis, and follicle survival rates. This review discusses the recent advances in ovarian tissue cryopreservation and transplantation with special focus on the use of stem cells to improve fertilization techniques.

Case report: two cases of mature oocytes found in prepubertal girls during ovarian tissue cryopreservation

Objective

To report two cases of mature oocytes found in prepubertal girls undergoing ovarian tissue cryopreservation (OTC).

Design

Case report.

Setting

Large tertiary care children’s hospital and a private fertility clinic.

Patient(s)

An 8-year-old prepubertal girl with β-thalassemia and a 2-year-old girl with sickle cell disease who both underwent OTC before bone marrow transplantations.

Intervention(s)

Laparoscopic right oophorectomy was performed in each patient. The ovarian cortical tissue was processed for slow freezing and long-term storage, and all oocytes were subsequently vitrified.

Main Outcome Measure(s)

Oocytes found at the time of OTC processing for fertility preservation.

Result(s)

After a complete right oophorectomy, one mature metaphase II oocyte was discovered on tissue processing for OTC in each patient. Neither patient has yet returned for use of tissue or oocytes.

Conclusion(s)

To our knowledge, this is the first report of mature oocytes found during prepubertal OTC processing. These findings may indicate the need for increased research regarding prepubertal oocyte development and suggest that the technique of examining the media for both mature and immature oocytes at the time of OTC should become more widespread and perhaps recommended in prepubertal patients to optimize fertility preservation methods.

Restricted access to assisted reproductive technology and fertility preservation: legal and ethical issues

Access to assisted reproductive technology (ART) and fertility preservation remains restricted in middle and low income countries. We sought to review the status of ART and fertility preservation in Brazil, considering social indicators and legislative issues that may hinder the universal access to these services. Although the Brazilian Constitution expressly provides the right to health, and ordinary law ensures the state is obliged to support family planning, access to services related to ART and fertility preservation is neither easy nor egalitarian in Brazil. Only a handful of public hospitals provide free ART, and their capacity far from meets demand. Health insurance does not cover ART, and the cost of private care is unaffordable to most people. Brazilian law supports, but does not command, the state provision of ART and fertility preservation to guarantee the right to family planning; therefore, the availability of state-funded treatments is still scarce, reinforcing social disparities. Economic projections suggest that including ART in the Brazilian health system is affordable and may actually become profitable to the state in the long term, not to mention the ethical imperative of recognizing infertility as a disease, with no reason to be excluded from a health system that claims to be 'universal'.

Age-Dependent in vitro Maturation Efficacy of Human Oocytes - Is There an Optimal Age?

In vitro maturation of oocytes from antral follicles seen during tissue harvesting is a fertility preservation technique with potential advantages over ovarian tissue cryopreservation (OTC), as mature frozen and later thawed oocyte used for fertilization poses decreased risk of malignant cells re-seeding, as compared to ovarian tissue implantation. We previously demonstrated that in vitro maturation (IVM) performed following OTC in fertility preservation patients, even in pre-menarche girls, yields a fair amount of oocytes available for IVM and freezing for future use. We conducted a retrospective cohort study, evaluating IVM outcomes in chemotherapy naïve patients referred for fertility preservation by OTC that had oocyte collected from the medium with attempted IVM. A total of 133 chemotherapy naïve patients aged 1-35 years were included in the study. The primary outcome was IVM rate in the different age groups - pre-menarche (1-5 and ≥6 years), post-menarche (menarche-17 years), young adults (18-24 years) and adults (25-29 and 30-35 years). We demonstrate a gradual increase in mean IVM rate in the age groups from 1 to 25 years [4.6% (1-5 years), 23.8% (6 years to menarche), and 28.4% (menarche to 17 years)], with a peak of 38.3% in the 18-24 years group, followed by a decrease in the 25-29 years group (19.3%), down to a very low IVM rate (8.9%) in the 30-35 years group. A significant difference in IVM rates was noted between the age extremes - the very young (1-5 years) and the oldest (30-35 years) groups, as compared with the 18-24-year group (p < 0.001). Importantly, number of oocytes matured, percent of patients with matured oocytes, and overall maturation rate differed significantly (p < 0.001). Our finding of extremely low success rates in those very young (under 6 years) and older (≥30 years) patients suggests that oocytes retrieved during OTC prior to chemotherapy have an optimal window of age that shows higher success rates, suggesting that oocytes may have an inherent tendency toward better maturation in those age groups.