Cryopreservation of oocytes from pre-antral follicles

Effects of resveratrol on HIF-1α/VEGF pathway and apoptosis in vitrified duck ovary transplantation

Preservation of ovarian tissues is an effective way to ensure genetic diversity of susceptible natural bird populations that are in danger of extinction. We examined whether the addition of the plant phenol resveratrol to vitrification solutions ameliorates the damaging effects of tissue hypoxia and reperfusion injury when the tissues are transplanted. Duck ovary tissues were frozen in the presence of varying concentrations of resveratrol in cryopreservation solutions and then transplanted under the renal capsules of 2-day-old Shelducks. Samples of the transplanted tissues were examined on days 3- and 9- post transplantation for activation of hypoxia-, antioxidant- and apoptosis-related gene expression and apoptosis. Resveratrol significantly increased expression of VEGF, HIF-1α, Nrf2, CAT and Bcl-2 mRNA and decreased BAX and Caspase-3 mRNA and reduced numbers of TUNEL-positive cells after vitrification and heterotopic ovarian transplantation. Resveratrol improved the antioxidant capacity, reduced apoptosis and activated the HIF-1α/VEGF pathway to promote angiogenesis 3- and 9-days following transplantation. These results indicated that the addition of resveratrol to vitrification solutions intended for long-term cryopreservation of ovary tissues improves survival in storage and the grafts following transplantation. This study provides a theoretical basis for the successful transplantation of avian ovarian tissue after vitrification.

Novel Approaches Used in Ovarian Tissue Transplantation for Fertility Preservation: Focus on Tissue Engineering Approaches and Angiogenesis Capacity

Due to the impact of the modern lifestyle, female infertility has been reduced because of different reasons. For example, in combined chemotherapeutic therapies, a small fraction of cancer survivors has faced different post-complications and side effects such as infertility. Besides, in modern society, delayed age of childbearing has also affected fertility. Nowadays, ovarian tissue cryopreservation and transplantation (OTC/T) is considered one of the appropriate strategies for the restoration of ovarian tissue and bioactivity in patients with the loss of reproductive function. In this regard, several procedures have been considered to improve the efficacy and safety of OTT. Among them, a surgical approach is used to transplant ovaries into the optimal sites, but the existence of ischemic changes and lack of appropriate revascularization can lead to bulk follicular atresia. Besides, the role of OTC/T is limited in women of advanced maternal age undergoing lifesaving chemo-radiation. As a correlate, the development of de novo approaches with efficacious regenerative outcomes is highly welcomed. Tissue engineering shows high therapeutic potentialities to restore fertility in males and females using the combination of biomaterials, cells, and growth factors. Unfortunately, most synthetic and natural materials are at the experimental stage and only the efficacy has been properly evaluated in limited cases. Along with these descriptions, strategies associated with the induction of angiogenesis in transplanted ovaries can diminish the injuries associated with ischemic changes. In this review, the authors tried to summarize recent techniques, especially tissue engineering approaches for improving ovarian function and fertility by focusing on angiogenesis and neovascularization.

Post-thaw viability of mouse preantral follicles after cryopreservation with cryotube freezing and OPS vitrification procedures

In the field of reproductive science, there is an increased interest in the application of ovarian preantral follicles. Since the ovary contains a great amount of preantral follicles (PAF), the cryopreservation and in vitro culture of such follicles support the fertility preservation of domestic animals with high genetic value, endangered or zoo animals, and women before anticancer therapy. To date, no standard freezing or vitrification protocol is available in human or animals. The aim of the present study was to examine the viability of preantral follicles cryopreserved using freezing or vitrification protocols: cryotube freezing or OPS vitrification.

Survival of isolated human preantral follicles after vitrification: Analyses of morphology and Fas ligand and caspase-3 mRNA expression

Objective

This study aimed to examine the effect of vitrification on apoptosis and survival in human preantral follicles after thawing.

Methods

This experimental study was conducted at an acute tertiary care hospital from March 2012 to April 2013. Ovaries were sliced into 5×5×1-mm pieces and divided into the following three groups: preantral follicle isolation, ovarian tissue vitrification-warming followed by follicle isolation, and immunohistochemistry of fresh ovarian tissue. For statistical analyses, the Student t-test, chi-square test, Kruskal-Wallis test, and Kaplan-Meier survival analysis were used.

Results

A total of 161 preantral follicles (70% secondary) were collected from ovarian cortex tissue of six women between 30 and 37 years of age who underwent oophorectomy due to cervical cancer or breast cancer. There were no significant differences in the follicular morphology of fresh preantral follicles and vitrified follicles after thawing. The mean Fas ligand (FasL) mRNA expression level was 0.43±0.20 (relative to β-actin) in fresh preantral follicles versus 0.51±0.20 in vitrified follicles (p=0.22). The mean caspase-3 mRNA expression level in fresh preantral follicles was 0.56±0.49 vs. 0.27±0.21 in vitrified follicles (p=0.233). One vitrified-thawed secondary follicle grew and developed to an antral follicle within 6 days of culture.

Conclusion

Vitrification did not affect preantral follicle morphology or mRNA expression of the apoptosis markers FasL and caspase-3. Further studies are required to establish whether vitrification affects the outcomes of in vitro culture and the maturation of preantral follicles.

Is the pre-antral ovarian follicle the 'holy grail'for female fertility preservation?

Fertility preservation is not only a concern for humans with compromised fertility after cancer treatment. The preservation of genetic material from endangered animal species or animals with important genetic traits will also greatly benefit from the development of alternative fertility preservation strategies. In humans, embryo cryopreservation and mature-oocyte cryopreservation are currently the only approved methods for fertility preservation. Ovarian tissue cryopreservation is specifically indicated for prepubertal girls and women whose cancer treatment cannot be postponed. The cryopreservation of pre-antral follicles (PAFs) is a safer alternative for cancer patients who are at risk of the reintroduction of malignant cells. As PAFs account for the vast majority of follicles in the ovarian cortex, they represent an untapped potential, which could be cultivated for reproduction, preservation, or research purposes. Vitrification is being used more and more as it seems to yield better results compared to slow freezing, although protocols still need to be optimized for each specific cell type and species. Several methods can be used to assess follicle quality, ranging from simple viability stains to more complex xenografting procedures. In vitro development of PAFs to the pre-ovulatory stage has not yet been achieved in humans and larger animals. However, in vitro culture systems for PAFs are under development and are expected to become available in the near future. This review will focus on recent developments in (human) fertility preservation strategies, which are often accomplished by the use of in vitro animal models due to ethical considerations and the scarcity of human research material.

Cryopreservation of Human Ovarian Tissue: A Review

BACKGROUND

Cryopreservation of human ovarian tissue has been increasingly applied worldwide to safeguard fertility in cancer patients, notably in young girls and women who cannot delay the onset of their treatment. Moreover, it has been proposed to patients with benign pathologies with a risk of premature ovarian insufficiency. So far, more than 130 live births have been reported after transplantation of cryopreserved ovarian tissue, and almost all patients recovered their ovarian function after tissue reimplantation.

SUMMARY

This review aims to summarize the recent results described in the literature regarding human ovarian tissue cryopreservation in terms of methods and main results obtained so far. To cryopreserve human ovarian tissue, most studies describe a slow freezing/rapid thawing protocol, which is usually an adaptation of a protocol developed for sheep ovarian tissue. Since freezing has been shown to have a deleterious effect on ovarian stroma and granulosa cells, various research groups have been vitrifying ovarian tissue. Despite promising results, only 2 babies have been born after transplantation of vitrified/warmed ovarian tissue. Optimization of both cryopreservation strategies as well as thawing/warming protocols is therefore necessary to improve the survival of follicles in cryopreserved ovarian tissue.

KEY MESSAGES

Human ovarian tissue cryopreservation has been successfully applied worldwide to preserve fertility in patients with malignant or nonmalignant pathologies that have a detrimental effect on fertility. Human ovarian tissue cryopreservation could also be applied as an alternative to postpone pregnancy or menopause in healthy women. Slow freezing and vitrification procedures have been applied to cryopreserve human ovarian tissue, but both alternatives require optimization.

Cryostorage and retransplantation of ovarian tissue as an infertility treatment

While still considered an experimental procedure in most countries, ovarian tissue cryopreservation and transplantation has been increasingly applied worldwide to restore fertility in patients with malignant and non-malignant pathologies with risk of premature ovarian insufficiency. It has yielded more than 130 live births up to now and almost all transplanted patients recovered their ovarian function. This study summarizes ovarian tissue cryopreservation and transplantation indications, procedures, their efficacy and main results and proposes different strategies to improve this strategy. Although the main focus of this study is on ovarian tissue cryopreservation and transplantation as a strategy to restore fertility, we believe that it is also important to discuss other applications for this approach.

An optimized controlled rate slow cooling protocol for bovine ovarian tissue cryopreservation by means of X-ray computed tomography

Cryopreservation and subsequent transplantation of ovarian tissue is the only option to preserve fertility in certain patients facing gonadotoxic treatment. So far, cryopreservation of ovarian tissue has been carried out mostly by a controlled rate slow cooling process, typically known as slow freezing. Even though there are still some concerns about the iatrogenic damage on the follicle population, this technique has been used in the more than 100 live births reported to date. It is well known that the control of the cryoprotectant loading in the tissue is crucial to in a cryopreservation procedure. We have used the technology of X-ray computed tomography to assess the concentration and distribution of dimethyl sulfoxide (one of the cryoprotectants most used in fertility preservation) inside pieces of bovine ovarian tissue after its cryopreservation. The low voltage used in our device (75 kV) and the high electronic density of this cryoprotectant makes the X-ray attenuation proportional to its concentration. By assessing and comparing the permeation and homogeneity of the cryoprotectant inside ovarian tissue fragments subjected to a controlled rate slow cooling process, we have characterized the effect of variations in the main parameters involved in the process, with the goal of achieving an optimized protocol with higher permeation of the cryoprotectant in the tissue. The most promissory results were obtained by increasing the initial concentration of dimethyl sulfoxide in the vehicle solution from 10 to 20%v/v.

Effects of vitrification on the viability of alginate encapsulated isolated bovine pre-antral follicles

PURPOSE

Individual follicle cryopreservation techniques, without hydrogel support, are labor-intensive and a substantial proportion of isolated follicles are lost during handling and after warming. Therefore, the viability and morphology of isolated bovine (as a model for human) pre-antral follicles after vitrification and warming, when encapsulated in alginate beads, were investigated.

METHODS

Bovine pre-antral follicles were mechanically isolated and divided into four different groups: (1) culture in 2% alginate beads (3D system) and vitrification in beads using mesh cups (3DVIT), (2) culture in 2% alginate beads (3DCUL), (3) culture in 96-well plates (2D system) and vitrification using High Security Vitrification straws® (2DVIT), (4) culture in a 2D system (2DCUL). The same vitrification and warming protocols were used for embedded (3DVIT) and non-embedded follicles (2DVIT).

RESULTS

No differences were observed in follicle viability between group 2DCUL and 3DCUL. Group 3DVIT showed the lowest viability (45.9%) according to calcein and neutral red staining among all groups. Group 2DVIT displayed the highest viability (87.5%) and largest percentage of follicles with a well-preserved morphology.

CONCLUSIONS

Our results show that, using a vitification protocol optimized for non-embedded follicles, 2D culture is more effective in vitrifying isolated follicles. However, embedding in alginate allow to handle follicles more efficiently, i.e., without excessive manipulation and thus less labor-intensive in combination with a reduced loss of follicles during the procedure. Based on the increased work efficiency, but lower viability and higher proportion of follicles showing impaired morphology, we consider it advantageous to optimize the protocol for the vitrification of embedded follicles to increase survival and maintain morphology after vitrification.

Ovarian tissue cryopreservation by stepped vitrification and monitored by X-ray computed tomography

Ovarian tissue cryopreservation is, in most cases, the only fertility preservation option available for female patients soon to undergo gonadotoxic treatment. To date, cryopreservation of ovarian tissue has been carried out by both traditional slow freezing method and vitrification, but even with the best techniques, there is still a considerable loss of follicle viability. In this report, we investigated a stepped cryopreservation procedure which combines features of slow cooling and vitrification (hereafter called stepped vitrification). Bovine ovarian tissue was used as a tissue model. Stepwise increments of the Me₂SO concentration coupled with stepwise drops-in temperature in a device specifically designed for this purpose and X-ray computed tomography were combined to investigate loading times at each step, by monitoring the attenuation of the radiation proportional to Me₂SO permeation. Viability analysis was performed in warmed tissues by immunohistochemistry. Although further viability tests should be conducted after transplantation, preliminary results are very promising. Four protocols were explored. Two of them showed a poor permeation of the vitrification solution (P1 and P2). The other two (P3 and P4), with higher permeation, were studied in deeper detail. Out of these two protocols, P4, with a longer permeation time at -40 °C, showed the same histological integrity after warming as fresh controls.

Strategies for Fertility Preservation in Female and Male Cancer Survivors

Improved survival rates and quality of life following modern cancer treatment have resulted in a growing number of patients requesting maintenance of reproductive capacity, both before and after completion of treatment. Several established options are currently available. In men, sperm banking should be offered as soon as the diagnosis of any malignant disease is established, irrespective of the expected cryosurvival rate. In such cases, conception can be achieved with frozen-thawed spermatozoa following either intrauterine insemination (IUI) or intracytoplasmic sperm injection (ICSI). In women, depending on the type of cancer, the presence of an adequate ovarian reserve, and time to delay cancer treatment, in vitro fertilization (IVF) with embryo cryopreservation constitutes a valid alternative. On the other hand, cryopreservation of mature oocytes following IVF/ICSI offers some advantages, but it is still limited by its low success rate. Emerging and exciting techniques of germ cell/gonadal tissue cryopreservation (banking) followed by autotransplantation have been clinically explored, particularly in women. Novel cryotechnologies of ovarian and testicular tissue have proven efficacious and new transplantation strategies promise improved results. However, only one live birth following autotransplanted frozen-thawed ovarian tissue has been established and there are still no pregnancies reported from autotransplanted cryopreserved testicular tissue in the human. Efficiency and safety of these techniques needs to be demonstrated. Methods for gamete in vitro maturation also need further development. Gonadal tissue cryopreservation and transplantation should be considered experimental in humans for the present time until greater evidence regarding efficacy and safety is accrued.

The Nuclear Maturation and Embryo Development of Mice Germinal Vesicle Oocytes with and without Cumulus Cell after Vitrification

BACKGROUND

Cryobiology is an essential tool in assisted reproductive technology. Research in this area focuses on the possibility of restoring fertility in women with reproductive problems or after cancer treatments.

AIM

The purpose of this study was to evaluate viability of oocytes, In vitro maturation and embryo development in vitrified germinal vesicle oocytes with and without cumulus cell after single and stepwise vitrification procedure.

MATERIALS AND METHODS

Germinal vesicle oocytes with or without cumulus cells were obtained from 4 weeks old female mice 48h after intraperitoneal injection of 7.5 IU pregnant mare serum gonadotropin (PMSG). For vitrification collected oocytes vitrification were exposed to cryoprotectant, which was composed of 30% (v/v) ethylene glycol, 18% (w/v) Ficoll-70, and 0.3 M sucrose, either by single step or in a step-wise way. After exposure to cryoprotectant and immerged in liquid nitrogen, the oocytes were thawed and washed in medium TCM199 two times. Then the oocytes transferred to IVM medium for maturation and embryo development to blastocyst.

RESULTS

The oocytes survival rates after vitrifying-warming, maturation rate, the capacity of fertilization and embryonic development to blastocyst were examined in vitro. The oocytes survival, maturation to MII, fertilization developmental rate in the step-wise exposure and with cumulus cell was significantly higher (p<0.05) as compared with corresponding rate in the single step procedure without cumulus cell.

CONCLUSION

The results of present study indicated that oocytes vitrified with cumulus cells and stepwise procedure had positive effect on maturation and developmental rate to blastocyst than oocytes without cumulus cell and single step procedure.

Effects of neutral red assisted viability assessment on the cryotolerance of isolated bovine preantral follicles

PURPOSE

Fertility preservation strategies warrant non-invasive viability assessment of preantral follicles (PAF) such as staining with Neutral Red (NR) that is incorporated by viable follicles. To optimize the procedure, we firstly determined the lowest concentration and shortest exposure time needed for optimal viability screening of isolated bovine PAF. Secondly, we combined this protocol to a vitrification procedure to assess cryotolerance of the stained follicles.

METHODS

Isolated PAF (900, divided over 6 replicates) were cultured in DMEM/Ham's F12 (Culture Medium - Cm) for 4 days (38.5 °C, 5% CO2). On D0, D2 and D4, follicles were stained, by adding NR medium (NRm = Cm with different concentrations NR) after which viability was assessed by counting stained/non-stained PAF every 30 min for a period of 2 h.

RESULTS

Following a binary logistic regression analysis with staining as a result (yes/no) versus log-concentration, a probability model could be fitted, indicating that the proportion of stained follicles remained stable after 30 min when 15 μg/ml NR was used, without compromising follicular health and viability. Consequently, using this protocol, no significant effect of staining prior to vitrification, was found on PAF viability immediately after warming or following 4 days of culture.

CONCLUSIONS

In conclusion, we propose NR staining as a non-invasive, non-detrimental viability assessment tool for PAF, when applied at 15 μg/ml for 30 min, being perfectly compatible with PAF vitrification.

Vitrification of mouse preantral follicles versus slow freezing: Morphological and apoptosis evaluation

The aim of this study was evaluation of survivability, maturation rate and apoptotic gene expression of preantral follicles after vitrification and slow freezing technique. Normal mouse preantral follicles were randomly divided into three experimental groups. In the control group, follicles were cultured immediately; in the vitrification and slow freezing groups, follicles were cultured after vitrification-warming and slow freezing-thawing procedures. Follicular viability was assessed by using 0.4% trypan blue, and molecular evaluation of messenger RNA levels of apoptosis-related genes was performed by the semi-quantitative RT-PCR method after 3 h of culture. Oocyte maturation rates were also evaluated on day 14 of culture. Survival and maturation rate in the slow freezing group were significantly lower than those in control and vitrification groups (P ≤ 0.05). Although there was no difference in Survivin expression among the three experimental groups, Bcl-2 expression was significantly lower in the slow freezing group compared to the other groups (P ≤ 0.05). The expression of Bax, P53, Fas and Bax/Bcl-2 ratio in the slow freezing group was significantly higher than control and vitrification groups (P ≤ 0.05). Preantral follicle vitrification seems to be better than slow freezing as seen in the survival, maturation and expression rates of apoptotic gene variants.

Optimal vitrification protocol for mouse ovarian tissue cryopreservation: effect of cryoprotective agents and in vitro culture on vitrified-warmed ovarian tissue survival

STUDY QUESTION

What is the optimal vitrification protocol according to the cryoprotective agent (CPA) for ovarian tissue (OT) cryopreservation?

SUMMARY ANSWER

The two-step protocol with 7.5% ethylene glycol (EG) and 7.5% dimethyl sulfoxide (DMSO) for 10 min then 20% EG, 20% DMSO and 0.5 M sucrose for 5 min showed the best results in mouse OT vitrification.

WHAT IS KNOWN ALREADY

Establishing the optimal cryopreservation protocol is one of the most important steps to improve OT survival. However, only a few studies have compared vitrification protocols with different CPAs and investigated the effect of in vitro culture (IVC) on vitrified-warmed OT survival. Some recent papers proposed that a combination of CPAs has less toxicity than one type of CPA. However, the efficacy of different types and concentrations of CPA are not yet well documented.

STUDY DESIGN, SIZE, DURATION

A total of 644 ovaries were collected from 4-week-old BDF1 mice, of which 571 ovaries were randomly assigned to 8 groups and vitrified using different protocols according to CPA composition and the remaining 73 ovaries were used as controls. After warming, each of the eight groups of ovaries was further randomly divided into four subgroups and in vitro cultured for 0, 0.5, 2 and 4 h, respectively. Ovaries of the best two groups among the eight groups were autotransplanted after IVC.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The CPA solutions for the eight groups were composed of EDS, ES, ED, EPS, EF, EFS, E and EP, respectively (E, EG; D, DMSO; P, propanediol; S, sucrose; F, Ficoll). The IVC medium was composed of α-minimal essential medium, 10% fetal bovine serum and 10 mIU/ml follicle-stimulating hormone (FSH). Autotransplantation of vitrified-warmed OTs after IVC (0 to 4 h) using the EDS or ES protocol was performed, and the grafts were recovered after 3 weeks. Ovarian follicles were assessed for morphology, apoptosis, proliferation and FSH level.

MAIN RESULTS AND THE ROLE OF CHANCE

The percentages of the morphologically intact (G1) and apoptotic follicles in each group at 0, 0.5, 2 and 4 h of IVC were compared. For G1 follicles at 0 and 4 h of IVC, the EDS group showed the best results at 63.8 and 46.6%, respectively, whereas the EP group showed the worst results at 42.2 and 12.8%, respectively. The apoptotic follicle ratio was lowest in the EDS group at 0 h (8.1%) and 0.5 h (12.7%) of IVC. All of the eight groups showed significant decreases in G1 follicles and increases in apoptotic follicles as IVC duration progressed. After autotransplantation, the EDS 0 h group showed a significantly higher G1 percentage (84.9%) than did the other groups (42.4-58.8%), while only the ES 4 h group showed a significant decrease in the number of proliferative cells (80.6%, 87.6-92.9%). However, no significant differences in apoptotic rates and FSH levels were observed between the groups after autotransplantation.

LIMITATIONS, REASONS FOR CAUTION

The limitation of this study was the absence of in vitro fertilization using oocytes obtained from OT grafts, which should be performed to confirm the outcomes of ovarian cryopreservation and transplantation.

WIDER IMPLICATIONS OF THE FINDINGS

We compared eight vitrification protocols according to CPA composition and found the EDS protocol to be the optimal method among them. The data presented herein will help improve OT cryopreservation protocols for humans or other animals.

Successful in vitro culture of pre-antral follicles derived from vitrified murine ovarian tissue: oocyte maturation, fertilization, and live births

Cryopreservation of ovarian tissue is an important option for preserving the fertility of cancer patients undergoing chemotherapy and radiotherapy. In this study, we examined the viability and function of oocytes derived in vitro from pre-antral follicles as an alternative method for restoring fertility. Pre-antral follicles (specified as secondary follicle with a diameter around 100-130 μm) were mechanically isolated from vitrified-warmed and fresh adult mouse ovarian tissues and cultured for 12 days followed by an ovulation induction protocol at the end of this period to initiate oocyte maturation. Oocytes were then released from these follicles, fertilized in vitro, and cultured to the blastocyst stage and vitrified. After storage in liquid nitrogen for 2 weeks, groups of vitrified blastocysts were warmed and transferred into pseudo-pregnant recipient females. Although most of the isolated mouse pre-antral follicles from fresh (79.4%) and vitrified (75.0%) ovarian tissues survived the 12-day in vitro culture period, significantly fewer mature oocytes developed from vitrified-warmed pre-antral follicles than from the fresh controls (62.2 vs 86.4%, P<0.05). No difference was observed in embryo cleavage rates between these two groups, but the proportion of embryos that developed into blastocysts in the vitrification group was only half that of the controls (24.2 vs 47.2%, P<0.05). Nevertheless, live births of healthy normal pups were achieved after transfer of vitrified blastocysts derived from both experimental groups. This study shows that successful production of healthy offspring using an in vitro follicle culture system is feasible, and suggests that this procedure could be used in cancer patients who wish to preserve their fertility using ovarian tissue cryopreservation.

Live offspring from vitrified blastocysts derived from fresh and cryopreserved ovarian tissue grafts of adult mice

Ovarian tissue cryopreservation and transplantation can be used to preserve fertility for cancer patients. In this study, we assessed the viability and function of ovarian tissue from adult mice that was cryopreserved by solid surface vitrification or traditional slow-cooling using variousin vitroandin vivotechniques, including allotransplantation,in vitrooocyte maturation, embryo culturein vitro, blastocyst cryopreservation, embryo transfer, and development. The importance of cumulus cells for oocyte maturation, fertilization, and embryo development was investigated. Graft recovery, follicle survival, and oocyte retrieval was similar in control, vitrified, and slow-cooled groups. High rates of oocyte maturation, cleavage, and blastocyst formation were achieved, with no significant differences between the control, vitrified or slow-cooled ovarian tissue grafts. The presence of cumulus cells was important for oocyte maturation, fertilization, and subsequent development. Cumulus–oocyte complexes with no surrounding cumulus cells (N-COCs) or with an incomplete layer (P-COCs) had significantly lower rates of oocyte maturation and blastocyst formation than cumulus–oocyte complexes with at least one complete layer of cumulus cells (F-COCs; maturation rate: 63, 78 vs 94%; blastocyst rate: 29, 49 vs 80%). Live births were achieved using vitrified blastocysts derived from oocytes taken from vitrified and slow-cooled ovarian tissue heterotypic allografts. Successful production of healthy offspring from these vitrified blastocysts suggests that this technique should be considered as a useful stage to pause in the assisted reproduction pathway. This provides an alternative protocol for restoring fertility and offering cancer patients a better indication of their chances of pregnancy and live birth.

Secondary follicle growth and oocyte maturation by culture in alginate hydrogel following cryopreservation of the ovary or individual follicles

An option for fertility preservation for women facing a cancer diagnosis involves the cryopreservation of ovarian tissue for later re-transplantation or in vitro culture, with in vitro culture preferred to avoid reintroduction of the cancer. Small, immature follicles survive the freeze-thaw process, and can be matured through in follicle maturation (IFM) that involves an initial growth of the follicle and subsequent maturation of the oocyte. The ovarian tissue can be cryopreserved in two forms: (i) cortical strips consisting of follicles and surrounding stroma (Cryo-Ov) or (ii) individually isolated follicles (Cryo-In). The aim of this study was to assess the follicle growth and oocyte maturation for follicles that were cryopreserved either as strips or individually using a slow-freezing cryopreservation method. The two follicle groups, together with non-cryopreserved control follicles, were grown in an alginate-based three-dimensional culture system for 12 days. The overall survival, size increase and antrum formation rates were comparable among the three groups. At day 12 of culture, Androstenedione levels were decreased in the Cryo-Ov group relative to the other two, and the ratio of progesterone to estradiol was increased in the two cryopreserved groups relative to the control. Both Gja1 (known as connexin 43) and Gja4 (known as connexin 37) mRNA expression were decreased at day 6 in the cryopreserved groups relative to controls, and by day 12, Gja1 was similar for all three groups. Moreover, Cryo-In resulted in lower GVBD rate indicating some impaired oocyte development. Overall, the present study demonstrated that mouse preantral follicles, either within ovarian tissues or individually isolated, could be successfully cryopreserved by the slow-freezing method, as evidenced by post-thaw follicle development and steroidgenesis, oocyte maturation and molecular markers for oocyte and/or granulosa cells connection.

Ovarian tissue cryopreservation: An update

Ovarian tissue cryopreservation and transplantation have been considered as promising means of fertility preservation for women who have survived cancer, with livebirths being reported from this technique. Ovarian tissue cryopreservation can be offered to patients with different types of cancer. Among the cryoprotectants, glycerol appears to give the poorest results. The techniques of cryopreserving ovarian tissue and alternative approaches have been reviewed in this article. The readers are reminded that this technique is still experimental and informed consent to be obtained from patients after counseling with medical information on the risks involved.

Follicular growth and estradiol follow-up after subcutaneous xenografting of fresh and cryopreserved human ovarian tissue

OBJECTIVE

To assess ovarian cortex surrounding benign ovarian cysts after cryopreservation and grafting to severe combined immunodeficient (SCID) mice.

DESIGN

Animal study.

SETTING

Academic research laboratories.

PATIENT(S)

Ovarian tissue obtained from 15 patients.

INTERVENTION(S)

Grafting of fresh and frozen/thawed ovarian tissue into the subcutaneous space of 22 SCID mice for 80 days.

MAIN OUTCOME MEASURE(S)

Histologic analysis before and after grafting. Serum E(2) measured before (after 37 days of grafting) and after FSH/LH supplementation (end of the study).

RESULT(S)

After grafting, follicular density had decreased for frozen/thawed tissue in all cases. The follicular distribution was modified in fresh tissue: Primordial follicles proportion was reduced (79% vs. 17%), whereas the primary and secondary ones were increased (21% vs. 57% and 0% vs. 23%, respectively). The same tendency was observed in frozen/thawed tissue. Significant E(2) secretion was obtained before and after FSH/LH supplementation in castrated mice, grafted with either fresh or frozen/thawed tissue.

CONCLUSION(S)

Fresh and cryopreserved ovarian cortex surrounding benign ovarian cysts grafted into the subcutaneous space of SCID mice is able to sustain ovarian tissue function, although follicular growth appears lower with frozen/thawed tissue.

Demande de préservation de la fertilité chez la femme en cas de maladie auto-immune: possibilités et pratiques en France

Cancer is not the only disease where the question of the female fertility preservation is asked. In autoimmune diseases, alkylating agents are also used and it is now established that 20 g as a cumulative dose of cyclophosphamide is associated with premature ovarian failure in 50% of 20-year-old patients. Several strategies are discussed and offered to these patients to prevent the ovarian failure: GnRH agonist treatment, in vitro fertilization and embryos cryopreservation, oocytes cryopreservation and ovarian cortex cryopreservation. These techniques might also be associated one with the other. A survey was conducted in France in order to assess the practices realised in these diseases. Four centres were asked for these diseases, concerning 17 patients (mean age: 26.2 +/- 1.8 SEM [15-43]) and systemic lupus erythematosus was the most frequent disease (7/17). Ovarian cortex cryopreservation was realised for 6 patients. Embryos or oocytes cryopreservation was realised for 2 patients including one where ovarian cortex cryopreservation was associated. In 10 cases, considering the treatment and the patient's wish no fertility preservation was realised. Female fertility preservation in autoimmune diseases is a difficult question and a national registry, such as the one conducted by the GRECOT, can help to answer this question.

Novel gamete storage

The aim of this review is to outline recent advances in gamete storage that are beneficial for rescuing endangered species or for the breeding of companion animals. Much more information is available on the technical resolutions and practical applications of sperm cryopreservation in various species than of female gametes, reproductive tissues or organs. Mammalian sperm cryopreservation often works relatively efficiently; however, the ability of female gametes to be cryopreserved and still be viable for fertilisation is also essential for rescuing endangered species. For a proper evaluation of gamete cryopreservation possibilities in a given species, it is essential to understand the basic mechanism affecting the survival of cryopreserved cells, the technical and physical limitations, the available techniques and the new avenues to resolve the specific problems in that species. This paper is aimed to provide some help for this process. The limited length of this paper resulted in the omission of information on many important areas, including most data on teleosts, amphibian and insect cryopreservation.

Novel direct cover vitrification for cryopreservation of ovarian tissues increases follicle viability and pregnancy capability in mice

BACKGROUND

Cryopreservation of ovarian tissue is valuable for fertility preservation. We develop an innovative vitrification method using less concentrated cryoprotectants and direct application of liquid nitrogen to the ovarian tissue (direct cover vitrification, DCV) to improve its efficiency.

METHODS

Ovaries of 5- to 6-week-old C57BL/6J mice were randomly allocated to four groups: DCV, conventional vitrification, slow-freezing and non-frozen controls. Experiment 1: observing the follicle morphology. Experiment 2: assessing viability. Experiment 3: investigating the ultrastructure. Experiment 4: examining the follicle number after grafting. Experiment 5: ascertaining pregnancy potential by allogeneic orthotopic transplantation.

RESULTS

The percentages of morphologically normal or viable follicles from DCV were significantly greater than those achieved from conventional vitrification and slow freezing (P < 0.01). The ultrastructure of primordial follicles from DCV appeared better than that achieved from conventional vitrification and slow freezing. After grafting, the follicle number from DCV was greater than conventional vitrification (P = 0.001) and slow freezing (P = 0.021). The pregnancy rate of DCV was higher than conventional vitrification (P < 0.01). The litter size from DCV was comparable with that from non-frozen graft and was significantly greater than that achieved from conventional vitrification and slow freezing (P < 0.01).

CONCLUSIONS

DCV is highly efficient for cryopreservation of ovarian tissue. Using less concentrated cryoprotectants appears to reduce toxicity. Direct cover by liquid nitrogen maximizes cooling that could facilitate vitrification and prevent ice crystal injury.

Permeability of ovine primordial follicles to different cryoprotectants

OBJECTIVE

To determine the behavior of isolated primordial follicles that were exposed to different concentrations of dimethyl sulfoxide (DMSO), ethylene glycol (EG), propylene glycol (PROH), and glycerol (GLY).

DESIGN

Isolated primordial follicles were exposed to the cryoprotectant (CPA) solution and photographed to calculate their volume at different periods of exposure.

SETTING

Laboratorio Renzo Giuliani, University of Florence, Italy.

ANIMAL(S)

Lambs, 30-40 days old.

INTERVENTION(S)

Isolation of primordial follicles and subsequent exposure to CPA.

MAIN OUTCOME MEASURE(S)

Follicular volume.

RESULT(S)

At 2 minutes of CPA exposure, all follicles appeared to be shrunken. At approximately 5 minutes, shrinkage ceased, and follicles started to swell, absorbing the CPA and water to maintain osmotic equilibrium. When DMSO was tested, follicular dehydration in all concentrations did not exceed 17%; with PROH and EG, it reached 33% and 27%, respectively. The highest degree of dehydration (48%) was seen with GLY. In almost all tested concentrations, follicular shrinkage occurred up to 5 minutes.

CONCLUSION(S)

Volume changes in isolated primordial follicles can fluctuate according to the CPA used and its concentration.

Orthotopic microvascular reanastomosis of whole cryopreserved ovine ovaries resulting in pregnancy and live birth

OBJECTIVE

To evaluate the feasibility of contralateral autotransplantation of cryopreserved whole ovaries with microanastomosis of the ovarian vascular pedicle.

DESIGN

Animal study.

SETTING

Department of Biomedical Sciences, General Hospital of Vienna, Austria.

ANIMAL(S)

Nine ewes, six month of age.

INTERVENTION(S)

Laparotomic unilateral oophorectomy was performed. Ovaries were frozen using a controlled-rate freezing system. After frozen storage, contralateral laparotomic oophorectomy was performed, and the thawed ovaries were returned to the contralateral orthotopic site with microsurgical vascular anastomosis.

MAIN OUTCOME MEASURE(S)

Histologic examination and serum follicle-stimulating hormone and progesterone levels.

RESULT(S)

Four sheep showed postoperative luteal function. One sheep conceived after spontaneous intercourse and delivered a healthy lamb 545 days after transplantation. Histologic examination of the ovaries 18-19 months after transplantation showed that the structural integrity of the ovarian stroma had largely been retained in six out of nine animals. Follicular survival rate in the grafted ovaries was 1.7%-7.6%.

CONCLUSION(S)

Microvascular anastomosis of whole ovaries and orthotopic transplantation after cryopreservation is technically feasible and a promising procedure in ovarian tissue banking.

Update on reproductive biotechnologies in small ruminants and camelids

Recent advances in reproductive biotechnologies in small ruminants include improvement of methods for in vitro production of embryos and attempts at spermatogonial stem cell transplantation. In vitro production of embryos by IVM/IVF, intra-cytoplasmic sperm injection (ICSI), or nuclear transfer (NT) has been made possible by improvements in oocyte collection and maturation techniques, and early embryo culture systems. However, in vitro embryo production still is not very efficient due to several limiting factors affecting the outcome of each step of the process. This paper discusses factors affecting in vitro embryo production in small ruminants and camelids, as well as preliminary results with the technique of spermatogonial stem cell transplantation.

Effects of sucrose concentration on the developmental potential of human frozen–thawed oocytes at different stages of maturity

BACKGROUND

Success of human oocyte cryopreservation depends on multiple cryobiological factors that could influence the developmental potential of the oocytes. The objective of this study was to examine the effects of different sucrose concentrations on the developmental potential of human frozen-thawed oocytes at different maturity stages.

METHODS

A total of 355 oocytes collected from small follicles were randomly divided into three groups and two groups (B and C) were cryopreserved using slow-freezing method. Group A included 131 oocytes at different maturity stages without freezing. Another 119 oocytes in Group B were cryopreserved with 0.1 M sucrose and 105 oocytes in Group C with 0.2 M sucrose concentration.

RESULTS

The post-thaw survival rate of the oocytes and the cleavage rate in Group C were significantly higher than that of Group B (P<0.05). For immature metaphase I (MI) stage oocytes, a significant difference was found in the maturation rate between Group C and Group B (P<0.05). The maturation rate for the GV oocytes in Groups A and C was significantly higher than Group B (P<0.01).

CONCLUSIONS

The results suggested that sucrose concentration of 0.2 M in the cryoprotectant solution is more suitable for human oocyte cryopreservation.

Gynaecologic concerns for young women exposed to gonadotoxic chemotherapy

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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