Follicular growth after xenotransplantation of cryopreserved/thawed human ovarian tissue in SCID mice: dynamics and molecular aspects

Thawing fertility: a view of ovarian tissue cryopreservation processes and review of ovarian transplant research

Individuals with a disease or treatment that increases their risk of premature gonadal insufficiency may opt to undergo fertility preservation. Those who are postpubertal can often cryopreserve gametes, sperm, or eggs to expand their biologic family using assisted reproductive technologies. Ovarian tissue cryopreservation (OTC) and testicular tissue cryopreservation may be an option for individuals who are unable to use standard fertility preservation techniques. The development of OTC was critical for many patients, including prepubertal children with ovaries that do not yet produce eggs, adolescents who make few good-quality eggs, and adult women with ovaries who cannot undergo ovarian stimulation. The only option to restore fertility and hormone production after OTC is through ovarian tissue transplantation (OTT). Ovarian tissue cryopreservation and OTT have been successful for some patients. Although OTC is no longer considered experimental by the American Society for Reproductive Medicine, the process is far from standardized. Significant research needs to be done, especially at the point of OTT, to improve the success and longevity of ovarian tissue function. This article lists the main steps from surgical procurement of the ovarian tissue to transplantation and restoration of function. Our pediatric hospital program has had to decide which options in procurement, processing, cryopreservation, and warming will be used in our clinical laboratory. The options and limitations within the research and analyses are briefly discussed. Literature focusing on techniques to improve OTT effectiveness and longevity was reviewed. Ovarian tissue transplantation studies that performed xenograft experiments after pretreatment of the tissue graft by a ligand or drug, treatment of the host, or encapsulation of the ovarian tissue were identified. The intended effects of the treatments include increasing vascularization, reducing apoptosis, and directing activation or suppression of primordial follicles. Robust research in this area must continue with rigorous analyses to make strides in improving fertility preservation and restoration options for patients.

In Vitro Maturation, In Vitro Oogenesis, and Ovarian Longevity

This paper will review a remarkable new approach to in vitro maturation "IVM" of oocytes from ovarian tissue, based on our results with in vitro oogenesis from somatic cells. As an aside benefit we also have derived a better understanding of ovarian longevity from ovary transplant. We have found that primordial follicle recruitment is triggered by tissue pressure gradients. Increased pressure holds the follicle in meiotic arrest and prevents recruitment. Therefore recruitment occurs first in the least dense inner tissue of the cortico-medullary junction. Many oocytes can be obtained from human ovarian tissue and mature to metaphase 2 in vitro with no need for ovarian stimulation. Ovarian stimulation may only be necessary for removing the oocyte from the ovary, but this can also be accomplished by simple dissection at the time of ovary tissue cryopreservation. By using surgical dissection of the removed ovary, rather than a needle stick, we can obtain many oocytes from very small follicles not visible with ultrasound. A clearer understanding of ovarian function has come from in vitro oogenesis experiments, and that explains why IVM has now become so simple and robust. Tissue pressure (and just a few "core genes" in the mouse) direct primordial follicle recruitment and development to mature oocyte, and therefore also control ovarian longevity. There are three distinct phases to oocyte development both in vitro and in vivo: in vitro differentiation "IVD" which is not gonadotropin sensitive (the longest phase), in vitro gonadotropin sensitivity "IVG" which is the phase of gonadotropin stimulation to prepare for meiotic competence, and IVM to metaphase II. On any given day 35% of GVs in ovarian tissue have already undergone "IVD" and "IVG" in vivo, and therefore are ready for IVM.

Human ovarian cryopreservation: vitrification versus slow freezing from histology to gene expression

Cryopreservation of ovarian tissue is one of the strategies offered to girls and women needing gonadotoxic treatment to preserve their fertility. The reference method to cryopreserve is slow freezing; vitrification is an alternative method. The aim was to evaluate which of the two is the best method for human ovarian tissue cryopreservation. Each ovary was divided into three groups: (i) fresh; (ii) slow freezing; and (iii) vitrification. An evaluation of the follicular density, quality and the expression six genes (CYP11A, STAR, GDF9, ZP3, CDK2, CDKN1A) were performed. We observed no significant difference in follicular density within these three groups. Slow freezing altered the primordial follicles compared to the fresh tissue (31.8% vs 55.9%, p = 0.046). The expression of genes involved in steroidogenesis varied after cryopreservation compared to the fresh group; CYP11A was under-expressed in slow freezing group (p = 0.01), STAR was under-expressed in the vitrification group (p = 0.01). Regarding the expression of genes involved in cell cycle regulation, CDKN1A was significantly under-expressed in both freezing groups (slow freezing: p = 0.0008; vitrification: p = 0.03). Vitrification had no effect on the histological quality of the follicles at any stage of development compared to fresh tissue. There was no significant difference in gene expression between the two techniques.

Effects of erythropoietin on ischaemia-reperfusion when administered before and after ovarian tissue transplantation in mice

RESEARCH QUESTION

Is the optimal timing for administering erythropoietin to minimize ischaemic injury in ovarian tissue transplantation before ovary removal for cryopreservation and subsequent transplantation or after transplantation?

DESIGN

Thirty Swiss mice (nu/nu) were divided into three groups: treatment control group (n = 10); erythropoietin before harvesting group (EPO-BH) (n = 10) and erythropoietin after transplantation group (EPO-AT) (n = 10). Animals underwent bilateral ovariohysterectomy and their hemiovaries were cryopreserved by slow freezing. At the same time, previously cryopreserved hemiovaries were transplanted subcutaneously in the dorsal region. Erythropoietin (250 IU/kg) and sterile 0.9% saline solution were administered every 12/12 h over 5 consecutive days in the EPO-AT and EPO-BH groups, respectively.

RESULTS

Administration of erythropoietin in the EPO-AT group improved the viability of ovarian follicles, reducing degeneration and increasing the number of morphologically normal growing follicles at 14 days after transplantation compared with the EPO-BH group (P = 0.002). This group also showed higher percentages of proliferative follicles at 7 days after transplantation (P ≤ 0.03), increased blood vessel count (P ≤ 0.03) and greater tissue area occupied by blood vessels at days 7 and 14 after transplantation (P ≤ 0.03), compared with hormone administration before cryopreservation (EPO-BH group) and the treatment control group. Additionally, treatment with erythropoietin before or after transplantation reduced fibrotic areas at 7 days after transplantation (P = 0.004).

CONCLUSION

Erythropoietin treatment after transplantation reduced ischaemic damage in transplanted ovarian tissue, increased angiogenesis, maintenance of ovarian follicle proliferation and reduced fibrosis areas in the grafted tissue.

The mTOR Inhibitor Rapamycin Counteracts Follicle Activation Induced by Ovarian Cryopreservation in Murine Transplantation Models

Background and Objectives: Ovarian tissue cryopreservation followed by autotransplantation (OTCTP) is currently the only fertility preservation option for prepubertal patients. Once in remission, the autotransplantation of frozen/thawed tissue is performed when patients want to conceive. A major issue of the procedure is follicular loss directly after grafting mainly due to follicle activation. To improve follicular survival during the OTCTP procedure, we inhibited the mTOR pathway involved in follicle activation using rapamycin, an mTOR inhibitor. Next, we compared two different in vivo models of transplantation: the recently described non-invasive heterotopic transplantation model between the skin layers of the ears, and the more conventional and invasive transplantation under the kidney capsule. Materials and Methods: To study the effects of adding rapamycin during cryopreservation, 4-week-old C57BL/6 mouse ovaries, either fresh, slow-frozen, or slow-frozen with rapamycin, were autotransplanted under the kidney capsule of mice and recovered three weeks later for immunohistochemical (IHC) analysis. To compare the ear with the kidney capsule transplantation model, fresh 4-week-old C57BL/6 mouse ovaries were autotransplanted to either site, followed by an injection of either LY294002, a PI3K inhibitor, vehicle control, or neither, and these were recovered three weeks later for IHC analysis. Results: Rapamycin counteracts cryopreservation-induced follicle proliferation, as well as AKT and mTOR pathway activation, in ovaries autotransplanted for three weeks under the kidney capsule of mice. Analyses of follicle proliferation, mTOR activation, and the effects of LY294002 treatment were similar in transplanted ovaries using either the ear or kidney capsule transplantation model. Conclusions: By adding rapamycin during the OTCTP procedure, we were able to transiently maintain primordial follicles in a quiescent state. This is a promising method for improving the longevity of the ovarian graft. Furthermore, both the ear and kidney capsule transplantation models were suitable for investigating follicle activation and proliferation and pharmacological strategies.

Ovarian tissue cryopreservation and transplantation for fertility preservation

Background: As the number of cancer survivors has increased with advancements in cancer treatment, fertility preservation has become a treatment goal. Ovarian tissue cryopreservation (OTC) and transplantation (OTT) has made great progress over the past few decades. It has become the treatment of choice for fertility preservation in adolescents or patients in urgent need of chemotherapy. However, it is considered to be experimental compared with oocyte or embryo cryopreservation in some countries. Nevertheless, OTC and OTT is regarded as the more ideal method for fertility preservation in that it can also restore hormonal functions.Current Concepts: Currently, over 200 live births have been reported worldwide after OTC and OTT, proving the excellence of the technology. However, before its application in clinical settings, some challenges, including cryoinjury, ischemic injury, and cancer cell reimplantation, should be overcome. For cryoinjury, studies are underway on protocol improvement with the addition of agents such as antifreeze protein during cryopreservation. For ischemic injury, various agents have been studied to promote angiogenesis or revascularization. Furthermore, studies are underway on artificial ovary or xenotransplantation for fertility preservation in an effort to avoid cancer cell metastasis.Discussion and Conclusion: OTC and OTT is a clinically applicable option for fertility preservation. To set OTC and OTT as an established method for fertility preservation, further research is necessary to overcome the current challenges.

In-vitro maturation and transplantation of cryopreserved ovary tissue: understanding ovarian longevity

RESEARCH QUESTION

Is it possible to use experience gained from 24 years of frozen ovarian transplantation, and from recent experience with in-vitro gametogenesis to accomplish simple and robust in-vitro maturation (IVM) of oocytes from human ovarian tissue?

DESIGN

A total of 119 female patients between age 2 and 35 years old underwent ovary cryopreservation (as well as in-vitro maturation of oocytes and IVM in the last 13 individuals) over a 24-year period. Up to 22 years later, 17 returned to have their ovary tissue thawed and transplanted back.

RESULTS

Every woman had a return of ovarian function 5 months after transplant, similar to previous observations. As observed before, anti-Müllerian hormone (AMH) concentration rose as FSH fell 4 months later. The grafts continued to work up to 8 years. Of the 17, 13 (76%) became pregnant with intercourse at least once, resulting in 19 healthy live births, including six live births from three women who had had leukaemia. Of the harvested germinal vesicle oocytes, 35% developed with simple culture media into mature metaphase II oocytes.

CONCLUSIONS

The authors concluded the following. First, ovary tissue cryopreservation is a robust method for preserving fertility even for women with leukaemia, without a need to delay cancer treatment. Second, many mature oocytes can often be obtained from ovary tissue with simple media and no need for ovarian stimulation. Third, ovarian stimulation only be necessary for removing the oocyte from the ovary, which can also be accomplished by simple dissection at the time of ovary freezing. Finally, pressure and just eight 'core genes' control primordial follicle recruitment and development.

Evaluation of an alternative heterotopic transplantation model for ovarian tissue to test pharmaceuticals improvements for fertility restoration

BACKGROUND

Ovarian tissue cryopreservation and transplantation (OTCTP) is currently the main option available to preserve fertility in prepubertal patients undergoing aggressive cancer therapy treatments. However, a major limitation of OTCTP is follicle loss after transplantation. The mouse is a model of choice for studying ovarian function and follicle development after ovarian tissue grafting in vivo. In these mouse models, ovarian tissue or ovaries can be transplanted to different sites. Our aim was to evaluate a new alternative to heterotopic transplantation models that could be useful to test pharmaceutical improvement for ovarian grafts after OTCTP.

METHODS

Slow frozen murine whole ovaries were transplanted into the mouse ears (between the external ear skin layer and the cartilage). Ovarian transplants were recovered after 3, 14 or 21 days. Grafts were analyzed by immunohistochemistry and follicle density analyses were performed.

RESULTS

An increase of ovarian vascularization (CD31 and Dextran-FITC positive staining), as well as cellular proliferation (Ki67 staining) were observed 3 weeks after transplantation in comparison to 3 days. Fibrosis density, evaluated after Van Gieson staining, decreased 3 weeks after transplantation. Furthermore, transplantation of cryopreserved ovaries into ovariectomized mice favored follicle activation compared to transplantation into non-ovariectomized mice.

CONCLUSION

The present study indicates that surgical tissue insertion in the highly vascularized murine ear is an effective model for ovarian grafting. This model could be helpful in research to test pharmaceutical strategies to improve the function and survival of cryopreserved and transplanted ovarian tissue.

Ovarian tissue features assessed in bovine fetuses after vitrification and xenotransplantation procedures

Cryopreservation and transplantation of ovarian tissue are proposed methods for the restoration of endocrine function and reproductive potential. Therefore, this study aimed to evaluate the effects of vitrification and xenotransplantation on follicle viability, activation, stromal cell integrity, vascularization, and micronuclei formation. Bovine fetal ovaries were fragmented and assigned to the following groups: Fresh control (FC), ovarian fragments immediately fixed; Vitrified control (VC), ovarian fragments vitrified; Vitrified xenotransplanted (VX), ovarian fragments vitrified and xenotransplanted; and Fresh xenotransplanted (FX), ovarian fragments xenotransplanted. Ovarian fragments were grafted in female BALB/c mice and recovered after 14 days. Follicular viability was preserved (P >  0.05) in VC group. The rate of developing follicles was greater (P <  0.05) in the FX group compared to other groups. Follicular density was higher (P <  0.05) in the VC group than the FC, VX, and FX groups. A decrease (P <  0.05) of stromal cell density was recorded after vitrification (VC vs. FX). Blood vessel density decreased in VC, VX, and FX groups compared with the FC group, and blood vessel density was correlated with follicular viability (positively; P =  0.07) and developing follicles (negatively; P <  0.001). Both vitrification and xenotransplantation groups (VC, VX, and FX) had a greater (P <  0.05) number of cells with one MN compared to the FC group. In summary, our findings showed that both vitrification and xenotransplantation modified blood vessel, follicular and stromal cell densities, follicular viability and activation, and micronuclei formation in ovarian tissue.

Post-thawing and culture comparison of three routine slow freezing methods for human ovarian tissue cryopreservation: Histological, molecular, and hormonal aspects

To find the gold standard out of three pre-established routine slow freezing (SF) methods, ovarian cortex tissues of nine transsexual individuals were cryopreserved and compared to each other, as well as the control (fresh) samples. Histological, genomic, and endocrinological effects of the SFs were assessed post-thawing and after a seven-day culture period. SF1 included 10% dimethyl-sulfoxide (Me2SO) in the base medium (BM), SF2 had 1.5 M/L ethylene-glycol (EG) and 0.1 M/L sucrose in the BM, and SF3 consisted of 6% Me2SO, 6% EG and 0.15 M/L sucrose in the BM. The cortical tissue strips went under a programmed cooling process and were stored in liquid nitrogen. Histological criteria (tissue damage and follicular quality), as well as gene expression levels, were assessed in the thawed and control tissues. Half of the thawed and control tissues were cultured for seven days and their histology, genetic profile, and hormonal status were examined as the reflection of the avascular tension effect. Post-thawing tissue damage was similar between all groups but significantly increased post-culture (P < 0.05). The percentages of high-quality follicles diminished in all SFs after thawing and culture (P < 0.05) except for the similarity of post-thawing SF3, compared to control. The genetic profile of the tissue after thawing and culture suggested quiescence/activation balance in SF1 and 2 and significant down-regulation in SF3, compared to the control specimens (P < 0.05). Post-thawing BAX:BCL2 was higher than control in SF1 and SF3 (P < 0.05), while this ratio in SF2 was similar to the control. However, after culture this ratio was similar to that of control in SF3 and diminished in SF1 and 2 (P < 0.05). The expression levels of gap-junction genes showed dramatic pre- and post-thawing fluctuations in all groups. After culture, estradiol in SF3 was significantly higher than SF1 and 2 (P < 0.05). In addition, progesterone in SF3 was similar to control but significantly lower in SF1 and 2 (P < 0.05). In conclusion, all SFs showed advantages and disadvantages, and the follicular quality and its function depend on the type of cryoprotectant and the speed of thawing. The effects of freezing/thawing continue to appear during the seven days of culture. According to the results of this study, SF3 seems to be more promising in keeping the follicles functional and safe from cell damage during culture.

Translational Physiology of Anti-Müllerian Hormone: Clinical Applications in Female Fertility Preservation and Cancer Treatment

Background

Whilst the ability of AMH to induce the regression of the Müllerian ducts in the male fetus is well appreciated, AMH has additional biological actions in relation to steroid biosynthesis and ovarian follicle dynamics. An understanding of the physiology of AMH illuminates the potential therapeutic utility of AMH to protect the ovarian reserve during chemotherapy and in the treatment of female malignancies. The translation of the biological actions of AMH into clinical applications is an emerging focus of research, with promising preliminary results.

Objective and Rationale

Studies indicate AMH restrains primordial follicle development, thus administration of AMH during chemotherapy may protect the ovarian reserve by preventing the mass activation of primordial follicles. As AMH induces regression of tissues expressing the AMH receptor (AMHRII), administration of AMH may inhibit growth of malignancies expressing AMHR II. This review evaluates the biological actions of AMH in females and appraises human clinical applications.

Search Methods

A comprehensive search of the Medline and EMBASE databases seeking articles related to the physiological functions and therapeutic applications of AMH was conducted in July 2021. The search was limited to studies published in English.

Outcomes

AMH regulates primordial follicle recruitment and moderates sex steroid production through the inhibition of transcription of enzymes in the steroid biosynthetic pathway, primarily aromatase and 17α-hydroxylase/17,20-lyase. Preliminary data indicates that administration of AMH to mice during chemotherapy conveys a degree of protection to the ovarian reserve. Administration of AMH at the time of ovarian tissue grafting has the potential to restrain uncontrolled primordial follicle growth during revascularization. Numerous studies demonstrate AMH induced regression of AMHR II expressing malignancies. As this action occurs via a different mechanism to traditional chemotherapeutic agents, AMH has the capacity to inhibit proliferation of chemo-resistant ovarian cancer cells and cancer stem cells.

Wider Implications

To date, AMH has not been administered to humans. Data identified in this review suggests administration of AMH would be safe and well tolerated. Administration of AMH during chemotherapy may provide a synchronistic benefit to women with an AMHR II expressing malignancy, protecting the ovarian reserve whilst the cancer is treated by dual mechanisms.

Pharmacological inhibition of the PI3K/PTEN/Akt and mTOR signalling pathways limits follicle activation induced by ovarian cryopreservation and in vitro culture

BACKGROUND

Cryopreservation and transplantation of ovarian tissue (OTCTP) represent a promising fertility preservation technique for prepubertal patients or for patients requiring urgent oncological management. However, a major obstacle of this technique is follicle loss due to, among others, accelerated recruitment of primordial follicles during the transplantation process, leading to follicular reserve loss in the graft and thereby potentially reducing its lifespan. This study aimed to assess how cryopreservation itself impacts follicle activation.

RESULTS

Western blot analysis of the PI3K/PTEN/Akt and mTOR signalling pathways showed that they were activated in mature or juvenile slow-frozen murine ovaries compared to control fresh ovaries. The use of pharmacological inhibitors of follicle signalling pathways during the cryopreservation process decreased cryopreservation-induced follicle recruitment. The second aim of this study was to use in vitro organotypic culture of cryopreserved ovaries and to test pharmacological inhibitors of the PI3K/PTEN/Akt and mTOR pathways. In vitro organotypic culture-induced activation of the PI3K/PTEN/Akt pathway is counteracted by cryopreservation with rapamycin and in vitro culture in the presence of LY294002. These results were confirmed by follicle density quantifications. Indeed, follicle development is affected by in vitro organotypic culture, and PI3K/PTEN/Akt and mTOR pharmacological inhibitors preserve primordial follicle reserve.

CONCLUSIONS

Our findings support the hypothesis that inhibitors of mTOR and PI3K might be an attractive tool to delay primordial follicle activation induced by cryopreservation and culture, thus preserving the ovarian reserve while retaining follicles in a functionally integrated state.

Molecular Mechanism and Prevention Strategy of Chemotherapy- and Radiotherapy-Induced Ovarian Damage

Fertility preservation is an emerging discipline, which is of substantial clinical value in the care of young patients with cancer. Chemotherapy and radiation may induce ovarian damage in prepubertal girls and young women. Although many studies have explored the mechanisms implicated in ovarian toxicity during cancer treatment, its molecular pathophysiology is not fully understood. Chemotherapy may accelerate follicular apoptosis and follicle reservoir utilization and damage the ovarian stroma via multiple molecular reactions. Oxidative stress and the radiosensitivity of oocytes are the main causes of gonadal damage after radiation treatment. Fertility preservation options can be differentiated by patient age, desire for conception, treatment regimen, socioeconomic status, and treatment duration. This review will help highlight the importance of multidisciplinary oncofertility strategies for providing high-quality care to young female cancer patients.

Current and Future Perspectives for Improving Ovarian Tissue Cryopreservation and Transplantation Outcomes for Cancer Patients

Although advances in cancer treatment and early diagnosis have significantly improved cancer survival rates, cancer therapies can cause serious side effects, including ovarian failure and infertility, in women of reproductive age. Infertility following cancer treatment can have significant adverse effects on the quality of life. However, established methods for fertility preservation, including embryo or oocyte cryopreservation, are not always suitable for female cancer patients because of complicated individual conditions and treatment methods. Ovarian tissue cryopreservation and transplantation is a promising option for fertility preservation in pre-pubertal girls and adult patients with cancer who require immediate treatment, or who are not eligible to undergo ovarian stimulation. This review introduces various methods and strategies to improve ovarian tissue cryopreservation and transplantation outcomes, to help patients and clinicians choose the best option when considering the potential complexity of a patient's situation. Effective multidisciplinary oncofertility strategies, involving the inclusion of a highly skilled and experienced oncofertility team that considers cryopreservation methods, thawing processes and devices, surgical procedures for transplantation, and advances in technologies, are necessary to provide high-quality care to a cancer patient.

Changes in telomere length and senescence markers during human ovarian tissue cryopreservation

Ovarian tissue cryopreservation is considered as a useful option to preserve fertility for cancer patients. This study purposed to evaluate the change of telomere length and senescence markers during human ovarian tissue cryopreservation. Ovarian tissues were obtained from women who underwent benign ovarian surgery in the gynecology research unit of a university hospital with prior consent and IRB approval. DNA was extracted from the ovarian tissues using a DNeasy tissue kit and telomere lengths in the DNA samples were determined by real time PCR before and after cryopreservation. All tissues were stained with hematoxylin–eosin and subjected to immunohistochemistry and TUNEL assays. Other senescence markers, including p53, p16, p21, and phospho-pRb proteins, were evaluated using western blot analysis. Ovarian tissues were collected from ten patients and prepared for slow freezing with the same size of diameter 4 mm and 1 mm thickness. Mean age of patients was 26.7 ± 6.2 years (range, 16–34 years), and ovarian tissues were cryopreserved and thawed 4 weeks after cryopreservation. The mean telomere length was significantly decreased after cryopreservation (9.57 ± 1.47 bp vs. 8.34 ± 1.83 bp, p = 0.001). Western blot analysis revealed that p53, p16, and p21 proteins increased and phospho-pRb protein expression decreased after ovarian tissue cryopreservation. Ovarian tissue cryopreservation and transplantation is regarded as one of promising options for fertility preservation. However, clinicians and researchers should be aware of possible irreversible DNA changes such as shortening of telomere length and alterations of other senescence markers in human ovarian tissues.

Hormonal Stimulation of Human Ovarian Xenografts in Mice: Studying Folliculogenesis, Activation, and Oocyte Maturation

Ovarian tissue cryopreservation and banking provides a fertility preservation option for patients who cannot undergo oocyte retrieval; it is quickly becoming a critical component of assisted reproductive technology programs across the world. While the transplantation of cryopreserved ovarian tissue has resulted in over 130 live births, the field has ample room for technological improvements. Specifically, the functional timeline of grafted tissue and each patient's probability of achieving pregnancy is largely unpredictable due to patient-to-patient variability in ovarian reserve, lack of a reliable method for quantifying follicle numbers within tissue fragments, potential risk of reintroduction of cancer cells harbored in ovarian tissues, and an inability to control follicle activation rates. This review focuses on one of the most common physiological techniques used to study human ovarian tissue transplantation, xenotransplantation of human ovarian tissue to mice and endeavors to inform future studies by discussing the elements of the xenotransplantation model, challenges unique to the use of human ovarian tissue, and novel tissue engineering techniques currently under investigation.

Implications of Nonphysiological Ovarian Primordial Follicle Activation for Fertility Preservation

In recent years, ovarian tissue cryopreservation has rapidly developed as a successful method for preserving the fertility of girls and young women with cancer or benign conditions requiring gonadotoxic therapy, and is now becoming widely recognized as an effective alternative to oocyte and embryo freezing when not feasible. Primordial follicles are the most abundant population of follicles in the ovary, and their relatively quiescent metabolism makes them more resistant to cryoinjury. This dormant pool represents a key target for fertility preservation strategies as a resource for generating high-quality oocytes. However, development of mature, competent oocytes derived from primordial follicles is challenging, particularly in larger mammals. One of the main barriers is the substantial knowledge gap regarding the regulation of the balance between dormancy and activation of primordial follicles to initiate their growing phase. In addition, experimental and clinical factors also affect dormant follicle demise, while the mechanisms involved remain largely to be elucidated. Moreover, most of our basic knowledge of these processes comes from rodent studies and should be extrapolated to humans with caution, considering the differences between species in the reproductive field. Overcoming these obstacles is essential to improving both the quantity and the quality of mature oocytes available for further fertilization, and may have valuable biological and clinical applications, especially in fertility preservation procedures. This review provides an update on current knowledge of mammalian primordial follicle activation under both physiological and nonphysiological conditions, and discusses implications for fertility preservation and priorities for future research.

Ovarian tissue transportation: a systematic review

In recent years, some countries and fertility preservation networks have started adopting 24 h transportation for ovarian tissue, a practice that has the potential to spread very quickly due to the high costs and bureaucracy involved in the establishment of ovarian tissue cryobanks. While pregnancies and live births have been reported after such long periods of transportation, this, however, remains an empirical procedure. This review aims to prompt reflection on ovarian tissue transport, highlighting the lack of knowledge in humans by providing a counterpoint looking into more than 40 studies published in different animal models. By discussing these studies in animals, the findings of various models can be deciphered, and light shed on the patterns identified. Like the development of different assisted reproductive technology procedures, this is an important step in creating guidelines for future studies on human ovarian tissue transportation.

Optimizing ovarian tissue quality before cryopreservation: comparing outcomes of three decortication methods on stromal and follicular viability

OBJECTIVE

To evaluate whether specific ovarian decortication techniques vary in promoting ovarian cortex cryopreservation and transplant outcomes.

DESIGN

Experimental design.

SETTING

University hospital.

ANIMAL(S)

Nonobese diabetic (NOD)/severe combined immunodeficiency (SCID) female mice.

INTERVENTION(S)

Human ovarian biopsy samples allocated to one of the following decortication procedures: scratching with scalpel blade (B), cutting with microsurgical scissors (M), separation with slicer (S), or no-separation (control, C). Parallel, in vivo experiment: decortication techniques combined with slow freezing (SF) and vitrification (VT) before xenograft into immunodeficient mice.

MAIN OUTCOME MEASURE(S)

Follicular counts, apoptosis, shear stress, Hippo pathway and inflammation. In vivo: recovered grafts analyzed for follicular counts, angiogenesis, proliferation, and fibrosis.

RESULT(S)

There were no differences in follicular density or number of damaged follicles between the decortication techniques in the in vitro study. Nevertheless, the M samples showed statistically significantly increased stromal damage compared with the controls and S samples, and up-regulation of Hsp60 shear stress gene expression. Decortication by both M and S inhibited the Hippo pathway, promoting gene expression changes. In the 21-day xenograft, total follicular density statistically significantly decreased compared with the nongrafted controls in all groups. Nevertheless, no differences were observed between the decortication techniques. Ovarian stroma vascularization was increased in the vitrified samples, but among the slow-freezing samples, the B samples had the lowest microvessel density. The M decorticated xenografts had increased fibrosis.

CONCLUSION(S)

Decortication with a slicer causes less damage to ovarian tissue than other commonly used methods although microsurgical scissors seem to preserve slightly increased follicular numbers. Nevertheless, blade decortication seems to be a reliable technique for maintaining acceptable follicular conditions without inducing serious stromal impairment.

Rescue of caprine fetal ovaries, vitrification and follicular development after xenotransplantation in two immunodeficient mice models

Domestic and wild goats are very susceptible animals to predation, specially when pregnancy occurs. This study aimed to evaluate the use of goat fetal ovarian tissue for vitrification followed by xenotransplantation and fresh xenotransplantation in two immunosuppressed mice models (C57BL/6 SCID and Balb-C NUDE). Goat fetus ovaries were collected in slaughterhouses, divided into small cortical pieces and were destined for fresh xenotransplantation (FX) and cryopreservation followed by xenotransplantation (CX). Five recipients from each lineage were used for FX and 10 animals from each lineage for CX. The mice were euthanized after 65 postoperative days, and the transplants were collected for microscopic assessment. The blood plasma was collected for estradiol measurement. Independently of mice strain, all recipients presented complete estrus cycle in FX and 80% after CX groups. Follicles were observed at all development stages without morphological changes. The volume density and total vessel surface observed in the transplants were different (p <0.01) between groups. The estradiol levels in the recipients did not differ (p <0.05) among the treatments. Thus, it is possible to activate the preantral follicles in the ovaries of fetuses by optimizing germplasm utilization and conservation of domestic and endangered wild goats that are in predatory situations, undesirable drowning or accidental death, since provided conditions for xenotransplantation are performed.

State of the Art in Fertility Preservation for Female Patients Prior to Oncologic Therapies

Quality of life improvement stands as one of the main goals of the medical sciences. Increasing cancer survival rates associated with better early detection and extended therapeutic options led to the specific modeling of patients’ choices, comprising aspects of reproductive life that correlated with the evolution of modern society, and requires better assessment. Of these, fertility preservation and ovarian function conservation for pre-menopause female oncologic patients pose a contemporary challenge due to procreation age advance in evolved societies and to the growing expectations regarding cancer treatment. Progress made in cell and tissue-freezing technologies brought hope and shed new light on the onco-fertility field. Additionally, crossing roads with general fertility and senescence studies proved highly beneficial due to the enlarged scope and better synergies and funding. We here strive to bring attention to this domain of care and to sensitize all medical specialties towards a more cohesive approach and to better communication among caregivers and patients.

Randomized study to prove the quality of human ovarian tissue cryopreservation by xenotransplantation into mice

Purpose

To study the quality of our human ovarian tissue cryopreservation technique as performed in the first official "International Fertility Protection Centre" in China in patients with certain cancer types using a mouse model, and to find the best site for tissue transplantation in the mouse.

Methods

Thirty-six BALB/C female nude mice were randomly divided into 3 groups, group 1: control group; group 2: ovariectomized group; group 3: ovarian tissue transplantation group. Seventy-two pieces obtained from six ovarian tissue samples from each of three cancer patients were transplanted into the ovarian bursa cavity (OBC), the subcutaneous thigh (TS) and the subcutaneous neck (NS) and removed after 1.5 and 2.5 months, respectively. Follicular growth rate (FGR), total follicle surviving rate (TFSR), tissue recovery rate (TRR), antral follicles (AF), follicle stimulating hormone (FSH), estradiol (E2) and anti-Mullerian hormone (AMH) levels were measured.

Results

No significant differences in FGR, OBC, NS (p > 0.05); TFSR was 100% in OBC, NS and TS. No significant differences in TRR (p > 0.05); AF were found only in OBC; TFSR was 100% after transplantation; significantly higher FGR in the 2.5 months compared to the 1.5 months-group (p  < 0.05). AMH- and E2-level in group 1 and 3 were significantly higher than in group 2 (p < 0.05); in contrast, FSH was significantly lower.

Conclusions

After transplantation in the mice, the thawed ovarian tissue survived and follicles developed. The ovarian fossa site was the best site for transplantation. Our animal experiments can verify that our human ovarian tissue cryopreservation technique can preserve the quality of ovarian tissue. This is the essential precondition for successful re-transplantation into the patients after performing chemo/radiotherapy to protect ovarian function and fertility.

Umbilical Cord Blood Mesenchymal Stem Cells as an Infertility Treatment for Chemotherapy Induced Premature Ovarian Insufficiency

Background: Premature ovarian insufficiency (POI) is a challenging disease, with limited treatment options at the moment. Umbilical cord blood mesenchymal stem cells (UCMSCs) have demonstrated promising regenerative abilities in several diseases including POI. Materials and Method: A pre-clinical murine case versus vehicle control randomized study. Two experiments ran in parallel in each of the three groups. The first was to prove the ability of UCMSCs in restoring ovarian functions. The second was to prove improved fertility. A total of 36 mice were randomly assigned; 6 mice into each of 3 groups for two experiments. Group 1 (control), group 2 (sham chemotherapy), group 3 (stem cells). Results: In the first experiment, post-UCMSCs treatment (group 3) showed signs of restored ovarian function in the form of increased ovarian weight and estrogen-dependent organs (liver, uterus), increased follicular number, and a significant decrease in FSH serum levels (p < 0.05) compared to group 2, and anti-Mullerian hormone (AMH) serum levels increased (p < 0.05) in group 3 versus group 2. Immuno-histochemistry analysis demonstrated a higher expression of AMH, follicle stimulating hormone receptor (FSHR) and Inhibin A in the growing follicles of group 3 versus group 2. In the second experiment, post-UCMSCs treatment (group 3) pregnancy rates were higher than group 2, however, they were still lower than group 1. Conclusion: We demonstrated the ability of UCMSCs to restore fertility in female cancer survivors with POI and as another source of stem cells with therapeutic potentials.

In vitro Activation Prior to Transplantation of Human Ovarian Tissue: Is It Truly Effective?

Research Question: What are the true benefits, if any, of disrupting the Hippo signaling pathway and stimulating the Akt pathway in xenotransplanted human ovarian tissue using an in vitro activation (IVA) approach? Design: Human ovarian tissue was retrieved from 18 young patients by laparoscopy and grafted to 54 severe combined immunodeficient mice. The experiment was conducted using fresh ovarian tissue (group I; n = 6 women), slow-frozen-thawed ovarian tissue (group II; n = 6 women), and vitrified-warmed ovarian tissue (group III; n = 6 women). Slow-freezing and vitrification procedures were performed according to Gosden's and Kawamura's protocols, respectively. The tissue (fresh, slow-frozen, and vitrified) was fragmented into small cubes (1 × 1 × 1 mm) to disrupt the Hippo signaling pathway and cultured or not in IVA medium for 48 h with Akt stimulators (PI3K stimulator and PTEN inhibitor), before being transplanted to the mice. All the grafts were maintained for 28 days. Results: (1) Follicular density: Follicular density decreased in all groups after transplantation, most significantly in the vitrification group. Culture with IVA had no impact. (2) Follicle activation: Addition of PI3K stimulator and PTEN inhibitor for 48 h prior to grafting did not significantly change the proportion of primordial follicles in any of the groups (fresh, slow-frozen, or vitrified tissue) compared to 48 h of control culture without these molecules. Particularly, vitrification and culture in IVA medium yielded no benefits in terms of growing follicle percentages or follicle proliferation rates. The large proportion of growing follicles in the vitrified tissue group after grafting may have been responsible for the higher rate of atresia. Conclusion: We were unable to demonstrate any significant benefits of cutting ovarian tissue into small cubes and applying IVA with Akt stimulators. The association of vitrification and transplantation was actually found to be the most deleterious combination with respect to the follicle reserve, and even worse when culture with Akt stimulators was performed.

Evaluation of Z-VAD-FMK as an anti-apoptotic drug to prevent granulosa cell apoptosis and follicular death after human ovarian tissue transplantation

PURPOSE

To evaluate the efficiency of ovarian tissue treatment with Z-VAD-FMK, a broad-spectrum caspase inhibitor, to prevent follicle loss induced by ischemia/reperfusion injury after transplantation.

METHODS

In vitro, granulosa cells were exposed to hypoxic conditions, reproducing early ischemia after ovarian tissue transplantation, and treated with Z-VAD-FMK (50 μM). In vivo, cryopreserved human ovarian fragments (n = 39) were embedded in a collagen matrix containing or not Z-VAD-FMK (50 μM) and xenotransplanted on SCID mice ovaries for 3 days or 3 weeks.

RESULTS

In vitro, Z-VAD-FMK maintained the metabolic activity of granulosa cells, reduced HGL5 cell death, and decreased PARP cleavage. In vivo, no improvement of follicular pool and global tissue preservation was observed with Z-VAD-FMK in ovarian tissue recovered 3-days post-grafting. Conversely, after 3 weeks of transplantation, the primary follicular density was higher in fragments treated with Z-VAD-FMK. This improvement was associated with a decreased percentage of apoptosis in the tissue.

CONCLUSIONS

In situ administration of Z-VAD-FMK slightly improves primary follicular preservation and reduces global apoptosis after 3 weeks of transplantation. Data presented herein will help to guide further researches towards a combined approach targeting multiple cell death pathways, angiogenesis stimulation, and follicular recruitment inhibition.

Recent advances in oncofertility care worldwide and in Japan

BACKGROUND

Oncofertility is a crucial facet of cancer supportive care. The publication of guidelines for the cryopreservation of oocytes and ovarian tissue is becoming increasingly prevalent in Japan and an updated overview is necessary.

METHODS

In order to provide an updated overview of oncofertility care, original research and review articles were searched from the PubMed database and compared in order to present clinical care in Japan.

RESULTS

In Western countries, various methods for ovarian stimulation, such as the combined use of aromatase inhibitors and random-start protocols, have been reported. Although ovarian tissue cryopreservation, mainly performed via the slow-freezing method, also has yielded >100 live births, the optimal indications and procedures for the auto-transplantation of cryopreserved tissue have been under investigation. In Japan, however, vitrification is prevalent for ovarian tissue cryopreservation, although its efficacy has not yet been established. The quality of network systems for providing oncofertility care in Japan varies greatly, based on the region.

CONCLUSION

There remain many issues in the optimization of oncofertility care in Japan. Along with the regional oncofertility networks, the creation of "oncofertility navigators" from healthcare providers who are familiar with oncofertility, such as nurses, psychologists, and embryologists, could be useful for supplementing oncofertility care coordination, overcoming the issues in individual regions.

Cryopreservation and transplantation of ovarian tissue: results from one center in the USA

Purpose

To report the results of cryopreserved ovary tissue transplantation for leukemia and other cancers, in a single US center.

Methods

One hundred eight females between age 6 and (median age 24) 35 were referred for possible ovary tissue cryopreservation over a 20-year period, with either slow freeze or vitrification. Thus far 13 patients returned up to 18 years later to have their tissue transplanted back.

Results

All 13 patients had return of ovarian function 5 months post transplant with regular menstrual cycling. AMH rose to very high levels as the FSH declined to normal. Four months later, the AMH again declined to very low levels. Nonetheless, the grafts remained functional for up to 5 years or longer. Ten of the 13 (77%) became spontaneously pregnant at least once, resulting in 13 healthy babies. A total of 24 healthy babies have been born 11 from fresh transplanted ovarian tissue and 13 from cryopreserved transplanted ovarian tissue.

Conclusions

(1) Ovary tissue cryopreservation is a robust method for preserving a woman’s fertility. (2) Cortical tissue pressure may be a key regulator of primordial follicle arrest, recruitment, and ovarian longevity. (3) This is the only such series yet reported in the USA.

Evaluation of vitrification protocol of mouse ovarian tissue by effect of DNA methyltransferase-1 and paternal imprinted growth factor receptor-binding protein 10 on signaling pathways

Transplantation of cryopreserved ovarian tissue has been considered as a promising way of fertility preservation for women. however, this cryopreservation method is prone to post-resuscitation follicle proliferation and oocyte development stagnation, affecting late transplant survival. To evaluate current vitrification works, we investigated the critical pathway alternations in vitrified-warmed juvenile 10-day-old mouse ovary. We showed a significant decrease of protein kinase B (Akt) and Mitogen-activated protein kinase (Mapk) phosphorylation, during which serine/threonine kinases play central roles in coordinating follicle and oocyte development and stress response. Inhibition of Akt and Mapk activity were associated with one of the imprinted insulin pathway negative regulatory genes, Growth factor receptor-binding protein 10 (Grb10) which remarkably increased in vitrified-warmed juvenile mouse ovary than that of fresh group (p < 0.05). RNAi-induced Grb10 down-regulation reversed the decrease in Akt and Mapk phosphorylation. The increase of Grb10 expression was partially caused by the hyper-methylation of the promoter region, associated with the decrease of follicular DNA methyltransferase (Dnmt) 1 protein in different stages of vitrified-warmed group, compared to fresh group (p < 0.05). The mRNA and protein expression of Dnmt1 in ovary of vitrified-warmed juvenile mouse were remarkably lower than those in fresh group (p < 0.05). Dnmt1 overexpression dramatically reversed Grb10 up-regulation and Akt and Mapk phosphorylation reduction. Taken together, our findings suggest that Grb10 expression might be helpful in evaluation of effectiveness of vitrification, and considered as a potential target for further vitrification protocols improvement in the future.

Ovarian tissue cryopreservation and transplantation: scientific implications

After fresh or frozen ovary transplantation, FSH levels return to normal, and menstrual cycles resume by 150 days, coincident with anti-Müllerian hormone rising to higher than normal levels. AMH then returns to well below normal levels by 240 days, remaining as such for many years with nonetheless normal ovulation and fertility. To date, 20 babies have been born in our program from 11 fresh and 13 cryopreserved ovary transplant recipients with a live baby rate of over 70 % (11 babies from fresh and 9 from frozen). Globally, over 70 live births have been reported for both fresh and frozen ovary transplants with an approximate 30 % live birth rate. Given the rapid rise of AMH after the fall of FSH, with a subsequent AMH decrease with retention of ovarian function, it is tempting to speculate the existence of a shared mechanism controlling primordial follicle recruitment, fetal oocyte meiotic arrest, and recruitment in the adult ovary. With the massive recruitment of primordial follicles observed after human ovarian cortical tissue transplantation, which subsides to an extremely low recruitment rate, we will discuss how this phenomenon suggests a unifying theory implicating ovarian cortical tissue rigidity in the regulation of both fetal oocyte arrest and recruitment of follicles in the adult ovary. As the paper by Winkler-Crepaz et al. in this issue demonstrates, our in vivo results are consistent with the in vitro demonstration that primordial follicles in the fetal cortex are "locked" in development, resulting in meiotic arrest, which spares the oocytes from being rapidly lost all at once (Winkler-Crepaz et al., J Assist Reprod Genet, 1). Winkler-Crepaz et al. demonstrate that follicle loss after ovarian cortex transplantation is unlikely due to ischemic apoptosis, but rather from a "burst" of primordial follicle recruitment. In vivo, primordial follicles are normally resistant to further development or activation to prevent oocyte depletion. The dense fibrous ovarian cortex, through as yet unresolved mechanisms, arrests the further continuation of meiosis and also prevents a sudden depletion of all resting follicles in the adult ovary. Intrinsic tissue pressure is released after cortical tissue transplantation, temporarily resulting in a rapid follicle depletion. These results are consistent with the observation that once the ovarian reserve is reduced in the graft, the rate of recruitment diminishes and the ovarian tissue exhibits a relatively long duration of function.