Assessment of long-term function of heterotopic transplants of vitrified ovarian tissue in cynomolgus monkeys

Systematic review and meta-analysis on patented and non-patented vitrification processes to ovarian tissue reported between 2000 and 2021

Due to the great interest in ovarian cryopreservation and, consequently conservation and restoration of female fertility in the last decades, different vitrification procedures (vitrification devices or solutions) have been developed, patented, and used both for academic research purposes and for clinical use. Therefore, the present study aimed to provide a systematic review and meta-analysis of data obtained from the application of different patented and non-patented vitrification devices and solutions in different countries. For this purpose, relevant observational studies published between the years 2000 to 2021 were selected to verify the efficiency of ovarian vitrification processes on parameters such as morphology, viability, and apoptosis in preantral ovarian follicles after transplantation or in vitro culture. Our research revealed that, although several countries were considered in the study, the United States and Japan were the countries that registered the most processes, and 22 and 16 vitrification devices and solutions out of a total of 51, respectively were patented. Sixty-two non-patented processes were also considered in the study in all countries. We also observed that transplantation and in vitro ovarian culture were the techniques predominantly used to evaluate the efficiency of the devices and vitrification solutions, respectively. In conclusion, this review showed that patented or non-patented protocols available in the literature are able to successfully preserve preantral follicles present in ovarian tissue. Despite the satisfactory results reported so far, adjustments in ovarian vitrification protocols in order to minimize cryoinjuries to the follicles remain one of the goals of cryopreservation and preservation of the female reproductive function. We found that vitrification alters the morphology and viability, and offers risks leading in some cases to follicular apoptosis. However, adjustments to current protocols to develop an optimal procedure can minimize damage by not compromising follicular development after vitrification/warming.

Investigation of the optimal culture time for warmed bovine ovarian tissues before transplantation

Ovarian tissue cryopreservation by vitrification is an effective technique, but there are still many unresolved issues related to the procedure. The aim of this study was to investigate the optimal culture time of post-warmed ovarian tissues and their viability before ovarian tissue transplantation. The bovine ovarian tissues were used to evaluate the effect of post-warming culture periods (0, 0.25, 0.5, 1, 2, 5 and 24 hours) in the levels of residual cryoprotectant, LDH release, ROS generation, gene and protein abundance, and follicle viability and its mitochondrial membrane potential. Residual cryoprotectant (CPA) concentration decreased significantly after 1 hour of culture. The warmed ovarian tissues that underwent between 0 to 2 hours of culture time showed similar LDH and ROS levels compared to fresh non-frozen tissues. The AMH transcript abundance did not differ in any of the groups. No increase in the relative transcript abundance and protein level of Caspase 3 and Cleaved-Caspase 3, respectively, in the first 2 hours of culture after warming. On the other hand, an increased protein level of double stranded DNA breaks (gamma-H2AX) was observed in post-warmed tissues disregarding the length of culture time, and a temporary reduction in pan-AKT was detected in post-warming tissues between 0 to 0.25 hours of culture time. Prolonged culture time lowered the percentage of viable follicles in warmed tissues, but it did not seem to affect the follicular mitochondrial membrane potential. In conclusion, 1 to 2 hours of culture time would be optimal for vitrified-warmed tissues before transplantation.

Quantification of residual cryoprotectants and cytotoxicity in thawed bovine ovarian tissues after slow freezing or vitrification

STUDY QUESTION

How much residual cryoprotectant remains in thawed/warmed ovarian tissues after slow freezing or vitrification?

SUMMARY ANSWER

After thawing/warming, at least 60 min of diffusion washing in media was necessary to significantly reduce the residual cryoprotectants in ovarian tissues frozen by slow freezing or vitrification.

WHAT IS KNOWN ALREADY

Ovarian tissue cryopreservation (OTC) by slow freezing has been the conventional method; while the vitrification method has gained popularity for its practicality. The main concern about vitrification is how much potentially toxic residual cryoprotectant remains in the warmed tissues at the time of transplantation.

STUDY DESIGN, SIZE, DURATION

This was an animal study using the ovarian tissues from 20 bovine ovaries. The duration of this study was from 2018 to 2020.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Ovarian cortex tissues were prepared from 20 bovine ovaries and assigned randomly to groups of fresh (non-frozen) control, slow freezing with 1.5 M dimethyl sulfoxide (DMSO), 1.5 M 1,2-propanediol (PROH) and vitrification with 35% ethylene glycol (EG). The residual cryoprotectant concentrations in thawed/warmed tissues were measured by gas chromatography at the following time points: frozen (before thawing/warming), 0 min (immediately after thawing/warming), 30, 60 and 120 min after diffusion washing in media. Next, the ultrastructural changes of primordial follicles, granulosa cells, organelles and stromal cells in the ovarian tissues (1 mm × 1 mm × 1 mm) were examined in fresh (non-frozen) control, slow freezing with DMSO or PROH and vitrification with EG groups. Real-time quantitative PCR was carried out to examine the expressions of poly (ADP-ribose) polymerase-1 (PARP1), a DNA damage sensor and caspase-3 (CASP3), an apoptosis precursor, in thawed/warmed ovarian tissues that were washed for either 0 or 120 min and subsequently in tissues that were ex vivo cultured for 24 or 48 h. The same set of tissues were also used to analyze the protein expressions of gamma H2A histone family member X (γH2AX) for DNA double-strand breaks and activated caspase-3 (AC3) for apoptosis by immunohistochemistry.

MAIN RESULTS AND THE ROLE OF CHANCE

The residual cryoprotectant concentrations decreased with the extension of diffusion washing time. After 60 min washing, the differences of residual cryoprotectant between DMSO, PROH and EG were negligible (P > 0.05). This washing did not affect the tissue integrity or significantly elevate the percentage of AC3 and γH2AX positive cells, indicating that tissues are safe and of good quality for transplantation.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Since the study was performed with ovarian tissues from bovines, generalizability to humans may be limited. Potential changes in ovarian tissue beyond 120 min were not investigated.

WIDER IMPLICATIONS OF THE FINDINGS

This study addresses concerns about the cytotoxicity of EG in warmed ovarian tissues and could provide insights when devising a standard vitrification protocol for OTC.

STUDY FUNDING/COMPETING INTEREST(S)

The study was funded by a Grant-in-Aid for Scientific Research (B) from the Japan Society for the Promotion of Science to N.S.

Current Understanding of the Etiology, Symptomatology, and Treatment Options in Premature Ovarian Insufficiency (POI)

Premature ovarian insufficiency (POI) occurs in at least 1% of all women and causes life-long health problems and psychological stress. Infertility caused by POI used to be considered absolute, with infertility treatment having little or no value. Generally, it has been thought that medicine can provide little service to these patients. The etiology of POI has been found to be genetic, chromosomal, and autoimmune. In addition, the increasing numbers of cancer survivors are candidates for iatrogenic POI, along with patients who have undergone ovarian surgery, especially laparoscopic surgery. Over 50 genes are known to be causally related to POI, and the disease course of some cases has been clarified, but in most cases, the genetic background remains unexplained, suggesting that more genes associated with the etiology of POI need to be discovered. Thus, in most cases, the genetic background of POI has not been clarified. Monosomy X is well known to manifest as Turner's syndrome and is associated with primary amenorrhea, but recent studies have shown that some women with numerical abnormalities of the X chromosome can have spontaneous menstruation up to their twenties and thirties, and some even conceive. Hormone replacement therapy (HRT) is recommended for women with POI from many perspectives. It alleviates vasomotor and genitourinary symptoms and prevents bone loss and cardiovascular disease. POI has been reported to reduce quality of life and life expectancy, and HRT may help improve both. Most of the problems that may occur with HRT in postmenopausal women do not apply to women with POI; thus, in POI, HRT should be considered physiological replacement of estrogen (+progesterone). This review describes some new approaches to infertility treatment in POI patients that may lead to new treatments for POI, along with the development of more sensitive markers of secondary/preantral follicles and genetic diagnosis.

Current state and future possibilities of ovarian tissue transplantation

BACKGROUND

As a result of recent developments in cancer treatment, cancer survivorship and survivors' quality of life have been emphasized. Although ovarian tissue cryopreservation (OTC) is an experimental technique, it would be the sole technique for fertility preservation treatment for girls with malignant disease. Indeed, OTC requires ovarian tissue transplantation (OTT) for conception. As for OTC, there is room to investigate OTT. The present review focused on the current state and progress of OTT.

METHOD

The literature regarding OTT, which is currently under development, was reviewed.

MAIN FINDINGS

To improve the outcome of OTT, both efficacy and safety are important. Good surgical technique and the optimal site are important surgical factors, with orthotopic transplantation increasing. Treatment of growth factors, gonadotropins, antioxidants, apoptosis suppression factors, and cell therapy may improve the efficacy of OTT by inducing neo-angiogenesis and preventing damage. Artificial ovaries, complete in vitro primordial follicle culture technique, and non-invasive ovarian imaging techniques, such as optical coherence tomography, to select the best ovarian tissue are future possibilities.

CONCLUSION

Improving neo-angiogenesis and preventing damage with optimization, as well as investigation of future techniques, may bring us to the next stage of a fertility preservation strategy.

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.

Oocyte retrieval after heterotopic transplantation of ovarian tissue cryopreserved by closed vitrification protocol

PURPOSE

A device for closed vitrification was designed to reduce the risk of contamination and investigated on its efficacy for ovarian function recovery after cryopreservation and heterotopic transplantation.

METHODS

Ovarian tissues from green fluorescence protein transgenic mice (10 GFP mice) were vitrified using the device, and warmed ovarian tissues were transplanted into the ovarian bursa region in wild-type female mice (6 mice). Fresh ovarian tissues were similarly transplanted as a control. After recovery of the estrous cycle, mice were mated with male mice. Ovarian tissues from six cynomolgus monkeys were vitrified and warmed with the device for autologous, heterotopic transplantation. Fresh tissue transplantation was not performed for the control. Ovarian function was examined by recovery of the hormonal cycle. Histological examination was conducted.

RESULTS

The number of live pups per recipient mouse was not significantly different after transplantation of fresh or vitrified-warmed ovarian tissue, although the pregnancy rate was reduced with vitrified tissues. The hormonal cycle was restored in 5/6 monkeys after heterotopic transplantation of vitrified-warmed ovarian tissue. Follicles were harvested at eight sites in the omentum and 13 sites in the mesosalpinx. In vitro maturation (IVM)/IVF produced embryo but did not develop.

CONCLUSIONS

Resumption of the hormonal cycles, follicle development, and oocyte retrieval from vitrified-warmed ovarian tissue transplants may indicate that the use of vitrification for ovarian tissue in a closed system has a potential of clinical application without the risk of contaminations. More detailed analyses of the effects of vitrification on ovarian tissue, such as gene expression patterns in oocytes and granulosa cells, may be needed for establishing a standard procedure for cryopreservation of ovarian tissues in human.

Effect of mouse ovarian tissue cryopreservation by vitrification with Rapid-i closed system

PURPOSE

Currently, open systems are mainly used for cryopreservation of ovarian tissue, oocytes, and embryos, but there is a potential risk of contamination. This study was performed to assess ovarian tissue cryopreservation by a closed vitrification system (Rapid-i vitrification system™), which is already used clinically for oocyte/embryo cryopreservation.

METHODS

Ovaries of C57BL/6J mice were frozen and thawed by using the Rapid-i vitrification system™ (Rapid-i) followed by implantation into recipient mice. Hematoxylin-eosin staining was performed for histological examination of the frozen-thawed ovaries to assess follicle grade. Fertility after implantation of the ovaries was assessed from the live birth rate and the number of live pups.

RESULTS

There was no significant difference in grade 1 primary follicles between fresh ovaries (control group, 94.2 ± 2.9%) and frozen-thawed ovaries (Rapid-i group, 87.1 ± 1.8%). However, there was a significant decrease in grade 1 early and late secondary follicles in the Rapid-i group compared with the control group. The live-birth rate was significantly lower in the Rapid-i group compared with the control group (29.2 vs. 83.3%, p < 0.05). On the other hand, there was no significant difference in the average number of live pups between the control group and the Rapid-i group (3 ± 0.4 vs. 2.7 ± 0.3).

CONCLUSIONS

The Rapid-i seems to be effective for cryopreservation of mouse ovarian tissue. Under appropriate conditions, the Rapid-i could be employed for ovarian tissue cryopreservation and preservation of fertility in humans.

Determination of Follicular Localization in Human Ovarian Cortex for Vitrification

PURPOSE

To determine the optimal follicle localization for ovarian vitrification in adolescent and young adult (AYA)-aged (between 15 and 39 years of age) patients with cancer or primary ovarian insufficiency (POI).

METHODS

In total, ovaries from 24 women were included in our study. These include women who received ovariectomy for fertility preservation before gonadotoxic treatments for cancer (n = 4), or for the treatment of POI by the in vitro activation method (n = 8), and other women and infants (0-3 years of age) whose ovaries were autopsied (n = 12). Before cryopreservation, a portion of the ovary sampled from cancer and POI patients was used for histological analysis. Depths of follicles from the surface of ovarian cortices were then measured by using digital imaging software. The locations of the follicles at different developmental stages in the ovarian cortex were noted.

RESULTS

The mean depth at which the primordial and primary follicles were located was 271 μm in infants. This was deeper in women in their twenties, thirties, and forties (501, 462, and 493 μm, respectively). The majority of secondary follicles were located <1000 μm from the ovarian surface (mean depth, 639 μm). In regard to patients with POI, the mean depth of primordial and primary follicles was 566 μm, whereas 70% of secondary follicles were located >1000 μm deep.

CONCLUSION(S)

These findings suggest that <1 mm is a potential optimum thickness of normal ovarian tissue for vitrification and a requirement that thicker ovarian cortices include secondary follicles in POI patients.

Expectations and limitations of ovarian tissue transplantation

Constant progress in the diagnosis and treatment of cancer disease has increased the number and prognosis of cancer survivors. However, the toxic effects of chemotherapy and radiotherapy on ovarian function have resulted in premature ovarian failure. Patients are, therefore, still expecting methods to be developed to preserve their fertility successfully. Several potential options are available to preserve fertility in patients who face premature ovarian failure, including immature or mature oocyte and embryo cryopreservation. However, for children or prepubertal women needing immediate chemotherapy, cryopreservation of ovarian tissue is the only alternative. The ultimate aim of this strategy is to implant ovarian tissue into the pelvic cavity (orthotopic site) or in a heterotopic site once oncological treatment is completed and the patient is disease free. Transplantation of ovarian tissue with sufficiently large numbers of follicles could potentially restore endocrine function and allow multiple cycles for conception. However, the success of ovarian tissue transplantation still has multiple challenges, such as the low number of follicles in the graft that may affect their longevity as well as the survival of the tissue during ex vivo processing and subsequent transplantation. Therefore, this review aims to summarize the achievements of ovary grafting and the potential techniques that have been developed to improve ovarian graft survival.

Good manufacturing practice requirements for the production of tissue vitrification and warming and recovery kits for clinical research

Products that are manufactured for use in a clinical trial, with the intent of gaining US Food and Drug Administration (FDA) approval for clinical use, must be produced under an FDA approved investigational new drug (IND) application. We describe work done toward generating reliable methodology and materials for preserving ovarian cortical tissue through a vitrification kit and reviving this tissue through a warming and recovery kit. We have described the critical steps, procedures, and environments for manufacturing products with the intent of submitting an IND. The main objective was to establish an easy-to-use kit that would ensure standardized procedures for quality tissue preservation and recovery across the 117 Oncofertility Consortium sites around the globe. These kits were developed by breaking down the components and steps of a research protocol and recombining them in a way that considers component stability and use in a clinical setting. The kits were manufactured utilizing current good manufacturing practice (cGMP) requirements and environment, along with current good laboratory practices (cGLP) techniques. Components of the kit were tested for sterility and endotoxicity, and morphological endpoint release criteria were established. We worked with the intended down-stream users of these kits for development of the kit instructions. Our intention is to test these initial kits, developed and manufactured here, for submission of an IND and to begin clinical testing for preserving the ovarian tissue that may be used for future restoration of fertility and/or hormone function in women who have gonadal dysgenesis from gonadotoxic treatment regimens or disease.

Where are oncofertility and fertility preservation treatments heading in 2016?

An improvement in the survival rates of cancer patients and recent advancements in assisted reproductive technologies have led to remarkable progress in oncofertility and fertility preservation treatments. Although there are several available or emerging approaches for fertility preservation, the limited evidence for each strategy is the greatest concern. In this review, we discuss the concerns on currently available options, and propose new approaches for fertility preservation that may be available in the future.

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

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

Cryopreservation of ovaries from neonatal marmoset monkeys

The ovary of neonatal nonhuman primates contains the highest number of immature oocytes, but its cryopreservation has not yet been sufficiently investigated in all life stages. In the current study, we investigated cryodamage after vitrification/warming of neonatal ovaries from a nonhuman primate, the common marmoset (Callithrix jacchus). A Cryotop was used for cryopreservation of whole ovaries. The morphology of the vitrified/warmed ovaries was found to be equivalent to that of fresh ovaries. No significant difference in the number of oocytes retaining normal morphology per unit area in histological sections was found between the two groups. In an analysis of dispersed cells from the ovaries, however, the cell viability of the vitrified/warmed group tended to be decreased. The results of a comet assay showed no significant differences in DNA damage. These results show that cryopreservation of neonatal marmoset ovaries using vitrification may be useful as a storage system for whole ovaries.

Impact of the cryopreservation technique and vascular bed on ovarian tissue transplantation in cynomolgus monkeys

PURPOSE

The aim of this study was to determine the best combination in terms of cryopreservation techniques and vascular bed preparation before grafting in order to obtain functional ovarian tissue after transplantation.

METHODS

Five cynomolgus monkeys were used. Strips from 10 ovaries were cryopreserved, 5 by vitrification (V), and 5 by slow-freezing (SF). Pieces of fresh ovarian tissue were used for controls. After 1 month, the strips were autografted to two different vascular beds, healed (HB) or freshly decorticated (FDB), constituting four study groups: SF-HB, SF-FDB, V-HB, and V-FDB. These were compared to fresh tissue. After 6 months, the ovaries were removed and several parameters analyzed: follicle quality, stage, density, proliferation, apoptosis, functionality, vascularization, and fibrosis. Mixed effect linear regression models were built to assess the impact of cryopreservation and vascular bed preparation on ovarian tissue viability and functionality. p values were adjusted for multiple testing using the Benjamini-Hochberg method, and q values < 0.20 were considered significant in order to achieve a 20% false discovery rate.

RESULTS

Compared to fresh tissue, no difference was observed in the percentage of morphologically normal follicles, while a significant increase was noted in the follicle proliferation rate (41%, q = 0.19), percentage of antral follicles (12%, q = 0.14), and number of vessels per area (3.3 times, q = 0.07) in the V-FDB group.

CONCLUSIONS

Vitrification associated with FDB vascular bed preparation is the best combination to obtain functional autografted ovarian tissue. Further studies are nevertheless required, with confirmed pregnancies and live births before introducing the procedure into clinical practice.

Intraovarian control of early folliculogenesis

Although hormonal regulation of ovarian follicle development has been extensively investigated, most studies concentrate on the development of early antral follicles to the preovulatory stage, leading to the successful use of exogenous FSH for infertility treatment. Accumulating data indicate that preantral follicles are under stringent regulation by FSH and local intraovarian factors, thus providing the possibility to develop new therapeutic approaches. Granulosa cell-derived C-type natriuretic factor not only suppresses the final maturation of oocytes to undergo germinal vesicle breakdown before ovulation but also promotes preantral and antral follicle growth. In addition, several oocyte- and granulosa cell-derived factors stimulate preantral follicle growth by acting through wingless, receptor tyrosine kinase, receptor serine kinase, and other signaling pathways. In contrast, the ovarian Hippo signaling pathway constrains follicle growth and disruption of Hippo signaling promotes the secretion of downstream CCN growth factors capable of promoting follicle growth. Although the exact hormonal factors involved in primordial follicle activation has yet to be elucidated, the protein kinase B (AKT) and mammalian target of rapamycin signaling pathways are important for the activation of dormant primordial follicles. Hippo signaling disruption after ovarian fragmentation, combined with treating ovarian fragments with phosphatase and tensin homolog (PTEN) inhibitors and phosphoinositide-3-kinase stimulators to augment AKT signaling, promote the growth of preantral follicles in patients with primary ovarian insufficiency, leading to a new infertility intervention for such patients. Elucidation of intraovarian mechanisms underlying early folliculogenesis may allow the development of novel therapeutic strategies for patients diagnosed with primary ovarian insufficiency, polycystic ovary syndrome, and poor ovarian response to FSH stimulation, as well as for infertile women of advanced reproductive age.

Successful fertility preservation following ovarian tissue vitrification in patients with primary ovarian insufficiency

STUDY QUESTION

Is ovarian tissue cryopreservation using vitrification followed by in vitro activation (IVA) of dormant follicles a potential approach for infertility treatment of patients with primary ovarian insufficiency (POI)?

SUMMARY ANSWER

Our vitrification approach followed by IVA treatment is a potential infertility therapy for POI patients whose ovaries contain residual follicles.

WHAT IS KNOWN ALREADY

Akt (protein kinase B) stimulators [PTEN (phosphatase with TENsin homology deleted in chromosome 10) inhibitor and phosphatidyinositol-3-kinase (PI3 kinase) stimulator] activate dormant primordial follicles in vitro and ovarian fragmentation disrupts the Hippo signaling pathway, leading to the promotion of follicle growth. We treated POI patients with a combination of ovarian vitrification, fragmentation and drug treatment, followed by auto-transplantation, and reported successful follicle growth and pregnancies.

STUDY DESIGN, SIZE, DURATION

Prospective clinical study of 37 infertile women with POI between 12 August 2011 and 1 November 2013. We enrolled 10 new patients since the previous publication.

PARTICIPANTS/MATERIALS, SETTING, METHODS

POI patients were originally selected based on a history of amenorrhea for more than 1 year and elevated serum FSH levels of >40 mIU/ml (n = 31) but this was later changed to >4 months, age <40 years and serum FSH levels of >35 mIU/ml (n = 6) (mean 71.8 ± 30.8, range 35.5-197.6) so as to include patients with a shorter duration of amenorrhea. Under laparoscopic surgery, ovariectomy was performed and ovarian cortices were dissected into strips for vitrification. Some pieces were examined histologically. After warming, two to three strips were fragmented into smaller cubes before culturing with Akt stimulators for 2 days. After washing, ovarian cubes were transplanted beneath the serosa of Fallopian tubes under laparoscopic surgery. Follicle growth was monitored by ultrasound and serum estrogen levels. After oocyte retrieval from mature follicles, IVF was performed.

MAIN RESULTS AND THE ROLE OF CHANCE

Among 37 patients, 54% had residual follicles based on histology. Among patients with follicles, 9 out of 20 showed follicle growth in auto-grafts with 24 oocytes retrieved from six patients. Following IVF and embryo transfer into four patients, three pregnancies were detected based on serum hCG, followed by one miscarriage and two successful deliveries. For predicting IVA success, we found that routine histological analyses of ovarian cortices and shorter duration from initial POI diagnosis to ovariectomy are valid parameters.

LIMITATIONS, REASONS FOR CAUTION

Although our findings suggest that the present vitrification protocol is effective for ovarian tissue cryopreservation, we have not compared the potential of vitrification and slow freezing in follicle growth after grafting. We chose the serosa of Fallopian tubes as the auto-grating site due to its high vascularity and the ease to monitor follicle growth. Future studies are needed to evaluate the best auto-grafting sites for ovarian tissues. Also, future studies are needed to identify biological markers to indicate the presence of residual follicles in POI to predict IVA treatment outcome.

WIDER IMPLICATIONS OF THE FINDINGS

In POI patients, ovarian reserve, namely the pool of residual follicles, continues to diminish with age. If one ovary is cryopreserved at an earlier stage of POI, patients could undergo additional non-invasive infertility treatments before the final decision for the IVA treatment. Furthermore, in the cases of unmarried POI patients, cryopreservation of ovarian tissues allows their fertility preservation until they desire to bear children.

STUDY FUNDING/COMPETING INTERESTS

This work was supported by Grant-In-Aid for Scientific Research (Research B: 24390376, Challenging Exploratory Research: 24659722, and Innovative Areas, Mechanisms regulating gamete formation in animals: 26114510) and by research funds from the Smoking Research Foundation, and the Takeda Science Foundation. None of the authors has a conflict of interest.

TRIAL REGISTRATION NUMBER

UMIN000010828.

The role of menstrual cycle phase and AMH levels in breast cancer patients whose ovarian tissue was cryopreserved for oncofertility treatment

Purpose

To determine the factors that affect oocyte extraction efficiency when using the “combined procedure”. In the present “combined procedure” ovarian tissue cryopreservation and oocyte extraction from an isolated ovary, later used in In Vitro Maturation (IVM), are performed concurrently.

Methods

Data were analyzed retrospectively and obtained from the clinical records of 27 young breast cancer patients referred for fertility preservation.

Results

The patients’ mean age was 33.7 (±3.8) years, mean serum anti-Müllerian hormone (AMH) concentration was 3.5 (±2.1) ng/ml, and mean number of extracted oocytes was 8.3 (±6.1). The phase of menstruation (follicular or luteal) did not affect either the number of oocytes extracted (P = 0.99) nor oocyte survival or maturation rates. Likewise, the number of oocytes that could be extracted was not affected by the type of laparoscopic procedure (multiple-port or single-incision laparoscopy; P = 0.94) or the molecular subtype of breast cancer (either Luminal A or B; P = 0.52). Analysis revealed that the number of extracted oocytes was well-correlated with the patient’s AMH serum level and age (coefficient of correlation: 0.60 and −0.48, respectively).

Conclusion

We conclude that the outcome of the “combined procedure” primarily depends upon the patient’s serum AMH level and age. Importantly, the “combined procedure” may be used during any phase of the menstrual cycle to preserve the fertility of breast cancer patients.

Mesenchymal Stem Cells Enhance Angiogenesis and Follicle Survival in Human Cryopreserved Ovarian Cortex Transplantation

Transplantation of cryopreserved ovarian tissue is a novel technique to restore endocrine function and fertility especially for cancer patients. However, the main obstacle of the technique is massive follicle loss as a result of ischemia in the process of transplantation. Mesenchymal stem cells (MSCs) have been acknowledged to play an important role in supporting angiogenesis and stabilizing long-lasting blood vessel networks through release of angiogenic factors and differentiation into pericytes and endothelial cells. This study is aimed to investigate whether MSCs could be applied to overcome the above obstacle to support the ovarian tissue survival in the transplantation. Here we show that human MSCs could enhance the expression level of VEGF, FGF2, and especially the level of angiogenin, significantly stimulate neovascularization, and increase blood perfusion of the grafts in the cryopreserved ovarian tissue transplantation. Further studies reveal that MSCs could notably reduce the apoptotic rates of primordial follicles and decrease follicle loss in the grafted ovarian tissues. In summary, our findings demonstrate a previously unrecognized function of MSCs in improving human ovarian tissue transplantation and provide a useful strategy to optimize fertility preservation and restoration.

Oxygen consumption rate of early pre-antral follicles from vitrified human ovarian cortical tissue

The study of human ovarian tissue transplantation and cryopreservation has advanced significantly. Autotransplantation of human pre-antral follicles isolated from cryopreserved cortical tissue is a promising option for the preservation of fertility in young cancer patients. The purpose of the present study was to reveal the effect of vitrification after low-temperature transportation of human pre-antral follicles by using the oxygen consumption rate (OCR). Cortical tissues from 9 ovaries of female-to-male transsexuals were vitrified after transportation (6 or 18 h). The follicles were enzymatically isolated from nonvitrified tissue (group I, 18 h of transportation), vitrified-warmed tissue (group II, 6 and 18 h of transportation) and vitrified-warmed tissue that had been incubated for 24 h (group III, 6 and 18 h of transportation). OCR measurement and the LIVE/DEAD viability assay were performed. Despite the ischemic condition, the isolated pre-antral follicles in group I consumed oxygen, and the mean OCRs increased with developmental stage. Neither the transportation time nor patient age seemed to affect the OCR in this group. Meanwhile, the mean OCR was significantly lower (P < 0.05) in group II but was comparable to that of group I after 24 h of incubation. The integrity of vitrified-warmed primordial and primary follicles was clearly corroborated by the LIVE/DEAD viability assay. These results demonstrate that the OCR can be used to directly estimate the effect of vitrification on the viability of primordial and primary follicles and to select the viable primordial and primary follicles from vitrified-warmed follicles.

Ovarian tissue cryopreservation in young cancer patients for fertility preservation

Several options are currently available to preserve fertility and give female cancer survivors a chance to have children at a later date, including the cryopreservation of embryos, oocytes, and ovarian tissue. Selection of the most suitable strategy to preserve fertility depends on the type and timing of anticancer therapy, the cancer, the patient's age, and the presence of the patient's partner. Several studies have shown that the ovarian tissue can be successfully frozen and later grafted in the human womb. To date, approximately 30 live births have been achieved after the transplantation of frozen-thawed ovarian tissue. At present, the standard procedure for cryopreservation of ovarian tissue is the slow-cooling method. The slow-cooling method uses an optimal cooling rate for the target cells, and relies on extracellular ice crystals to gradually dehydrate and equilibrate the tissue. Several groups reported that slow cooling is more efficient than vitrification for the cryopreservation of human ovarian tissue. However, vitrification can be performed under a variety of conditions, and therefore, the choice of methods is important. In addition, vitrification traps aqueous solutions in an amorphous, "vitreous" solid phase that prevents ice crystal formation in tissues. Vitrification methods that were developed using mice and monkey have recently been shown to improve the viability of vitrified ovarian tissues. In this review article, recent topics of ovarian tissue cryopreservation are described.

In vitro development of human primordial follicles to preantral stage after vitrification

PURPOSE

The aim was to culture primordial follicles in vitro to reach preantral stage in vitrified human ovarian tissue.

METHODS

Ovarian tissue samples were obtained from six women. Tissue strips were vitrified by infiltration with a cryoprotectant followed by mounting on a stainless steel carrier. After culturing for 7 days the morphology and developmental stages of follicles enclosed in fresh and vitrified groups were analyzed.

RESULTS

High proportion of viable follicles in vitrified ovarian strips was obtained. After culturing for 7 days the percentage of secondary and preantral follicles increased significantly (P < 0.05) whereas primordial and transitory follicles showed a significant decrease (P < 0.05) compared to their respective counterparts at day 0 of culture.

CONCLUSIONS

Vitrification of ovarian strips with an improved carrier device and culturing of follicles in ovarian strips after warming yielded developed follicles with high viability and morphological integrity that may be suitable for use in fertility preservation among cancer patients.

Hippo signaling disruption and Akt stimulation of ovarian follicles for infertility treatment

Primary ovarian insufficiency (POI) and polycystic ovarian syndrome are ovarian diseases causing infertility. Although there is no effective treatment for POI, therapies for polycystic ovarian syndrome include ovarian wedge resection or laser drilling to induce follicle growth. Underlying mechanisms for these disruptive procedures are unclear. Here, we explored the role of the conserved Hippo signaling pathway that serves to maintain optimal size across organs and species. We found that fragmentation of murine ovaries promoted actin polymerization and disrupted ovarian Hippo signaling, leading to increased expression of downstream growth factors, promotion of follicle growth, and the generation of mature oocytes. In addition to elucidating mechanisms underlying follicle growth elicited by ovarian damage, we further demonstrated additive follicle growth when ovarian fragmentation was combined with Akt stimulator treatments. We then extended results to treatment of infertility in POI patients via disruption of Hippo signaling by fragmenting ovaries followed by Akt stimulator treatment and autografting. We successfully promoted follicle growth, retrieved mature oocytes, and performed in vitro fertilization. Following embryo transfer, a healthy baby was delivered. The ovarian fragmentation-in vitro activation approach is not only valuable for treating infertility of POI patients but could also be useful for middle-aged infertile women, cancer patients undergoing sterilizing treatments, and other conditions of diminished ovarian reserve.

Antiapoptotic agent sphingosine-1-phosphate protects vitrified murine ovarian grafts

Significant follicle loss from frozen ovarian grafts is unavoidable. The authors evaluated the protective effects of the antiapoptotic agent sphingosine-1-phosphate (S1P) on vitrified ovarian grafts. Three-week-old sexually immature female FVB mice were divided into 4 groups, fresh, control without S1P, 0.5 mmol/L S1P, and 2 mmol/L S1P. The ovaries were pretreated with S1P for 1 hour and then cryopreserved by modified vitrification. The frozen-thawed ovaries were autotransplanted under the back muscles of mice for 10 days. Expression of apoptosis-related genes encoding caspase 3 and c-Myc was analyzed in the vitrified ovaries and 10 days after transplantation using real-time quantitative polymerase chain reaction. To quantify the ovarian reserve, anti-Müllerian hormone (AMH) levels and follicles were measured in the 10-day vitrified ovarian grafts. Caspase 3 and c-Myc messenger RNA did not differ significantly in the 4 groups after vitrification but was significantly upregulated in the control group after transplantation. The AMH levels and primordial follicle pool were significantly higher in the S1P-treated groups than in the control group but lower than that in the fresh group. The S1P protects vitrified ovarian grafts from ischemic reperfusion injury rather than from vitrification-associated process.

Good thermally conducting material supports follicle morphologies of porcine ovaries cryopreserved with ultrarapid vitrification

Effects of supporting materials during vitrification procedure on the morphologies of preantral follicles of pig ovaries were assessed. Ovarian cortical sections of prepubertal pigs were randomly allocated to 5 groups. The sections were vitrified ultrarapidly with 5 different vitrification devices. The sections were put on 4 fine needles (Cryosupport), on a thin copper plate, or on a carbon graphite sheet or were sandwiched between copper plates or between carbon graphite sheets before cooling. The cooling and warming rates with the graphite sheets were significantly higher than those with the copper plates (P<0.05). A total of 3,064 follicles were analyzed following HE staining after vitrification with 5 different devices. The morphologies follicles vitrified on the Cryosupport or on the graphite sheet were well preserved compared with those vitrified on the copper plate or between copper plates (P<0.01). The morphologies of follicles vitrified between copper plates were mostly damaged (P<0.05). Taken together, good thermally conducting material supports follicle morphologies of ovaries cryopreserved with ultrarapid vitrification.

Morphological and functional preservation of pre-antral follicles after vitrification of macaque ovarian tissue in a closed system

STUDY QUESTION

What are the appropriate conditions to vitrify the macaque ovarian cortex in a large-volume, closed system that will preserve functional pre-antral follicles?

SUMMARY ANSWER

The combination of glycerol, ethylene glycol (EG) and polymers with cooling in liquid nitrogen (LN2) vapor and a two-step warming procedure was able to preserve tissue and follicle morphology as well as function of a small population of secondary follicles in the macaque ovarian cortex following vitrification in a closed system.

WHAT IS KNOWN ALREADY

For prepubertal cancer patients or those who require immediate cancer therapy, ovarian tissue cryopreservation offers the only hope for future fertility. However, the efficacy of live birth from the transplantation of cryopreserved ovarian tissue is still unclear. In addition, live birth from cryopreserved ovarian tissue has only been demonstrated after tissue autotransplantation, which poses the risk of transmitting metastatic cancer cells back to the cancer survivor in certain cancers.

STUDY DESIGN, SIZE, DURATION

Non-human primate model, n = 4, randomized, control versus treatment. End-points were collected from tissue histology, tissue culture (48 h) and isolated secondary follicle culture (6 weeks).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Two vitrification solutions (VSs) containing EG + glycerol (VEG) and EG + dimethylsulfoxide (VED) were examined for vitrification, devitrification and thermodynamic properties. Once the optimal VS was determined, macaque ovarian cortical pieces (3 × 3 × 0.5 mm(3)) were divided into fresh and two vitrified groups (VEG and VED). For the vitrification groups, tissues were exposed to 1/4, 1/2 and 1× VS for 5 min/step as well as 1× VS + polymers for 1 min at 37°C, loaded into high-security straws with 1 ml of VS + polymers, heat sealed and cooled in LN2 vapor. Samples were warmed in a 40°C water bath and cryoprotective agents were diluted with 1, 0.5, 0.25 and 0 M sucrose. Tissues were fixed for histological analysis and cultured with bromodeoxyuridine (BrdU). Secondary follicles from VEG tissues were encapsulated and cultured (n = 24/treatment/animal). Follicle health, diameter and steroid [progesterone, androstenedione (A4), estradiol (E2)] production were analyzed weekly.

MAIN RESULTS AND THE ROLE OF CHANCE

Dense stroma and intact pre-antral follicles were observed using VS containing 27% glycerol, 27% EG and 0.8% polymers with cooling in LN2 vapor and a two-step warming. Higher cooling and warming rates led to fracturing. BrdU uptake was evident in granulosa cells of growing follicles in fresh and vitrified tissues. Secondary follicles from fresh tissues (70 ± 12%) and tissues vitrified with VEG (52 ± 2%) showed similar survival rates (all data: mean ± SEM; P > 0.05). For both groups, the initial follicle diameter was similar and increased (P < 0.05) by Week 3, but diameters in vitrified follicles were smaller (P < 0.05) by Week 6 (566 ± 27 µm) than those of the fresh follicles (757 ± 26 µm). Antrum formation rates were lower (P < 0.05) for vitrified (37 ± 6%) relative to fresh (64 ± 8%) follicles. There was no significant change in levels in culture media of E2, P4 and A4 between fresh and VEG groups at any time point during culture.

LIMITATIONS, REASONS FOR CAUTION

Only in vitro studies are reported. Future in vivo tissue transplantation studies will be needed to confirm long-term function and fertility potential of vitrified ovarian tissues.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first demonstration of antral follicle development during 3D culture following ovarian tissue vitrification in a closed system using primate ovarian tissue. While diminished antrum formation and slower growth in vitro reflect residual cryodamage, continued development of ovarian tissue vitrification based on cryobiology principles using a non-human primate model will identify safe, practical and efficient protocols for eventual clinical use. Tissue function following heterotopic transplantation is currently being examined.

STUDY FUNDING/COMPETING INTEREST(S)

National Institutes of Health (NIH) Oncofertility Consortium UL1 RR024926 (1RL1-HD058293, HD058295, PL1 EB008542), the Eunice Kennedy Shriver NICHD/NIH (U54 HD018185) and ONPRC 8P51OD011092-53. G.M.F. works for the company that makes the polymers used in the current study.

Autologous and allogeneic ovarian orthotopic transplantation: morphologic, endocrinologic and natural pregnancy assessment

PURPOSE

To assess pregnancy of rabbits submitted to bilateral ovariectomy and orthotopic allogeneic or autologous intact and sliced ovarian transplantation without a vascular pedicle and to determine the morphofunctional aspects of the transplanted ovaries.

METHODS

Fifty-six female rabbits were studied. The ovaries were removed and orthotopically transplanted or replaced without vascular anastomoses: Group 1 (n=8), only laparotomy and laparorrhaphy, Group 2A (n=8) intact ovaries were transplanted on both sides, Group 2B (n=8) both ovaries were sliced and orthotopically transplanted, Group 2C (n=8), an intact ovary was transplanted on one side and a sliced ovary on the other side. In Group 3 the ovaries were reimplanted according to the procedure and subgroups described for Group 2. Three months later, the animals were paired with males for copulation. Estradiol, progesterone, FSH and LH hormone levels were assessed. A histologic study was carried out, and the number of pregnancies and litters were also determined. Chi-square test compared the number of pregnancies and litters. One-way ANOVA and the Tukey-Kramer tests compared the hormonal dosages.

RESULTS

Pregnancies occurred in seven (87.5%) rabbits of Group 1, in three rabbits (37.5%) of Groups 2A and 3A, in four rabbits (50%) of groups 2B, 3B and 3C, and in five (62.5%) of group 2C. Normal hormone serum levels and histology confirmed the vitality of all ovaries.

CONCLUSION

Orthotopic allogeneic and autologous ovarian transplantation without a vascular pedicle is viable in rabbits, and preserves their hormonal levels and fertile functions.