Immunohistochemical localization of growth factors after cryopreservation and 3 weeks' xenotransplantation of human ovarian tissue

Follicle outcomes in human ovarian tissue: effect of freezing, culture, and grafting

OBJECTIVE

To study the effect of freezing, in vitro culture (IVC) and grafting to chorioallantoic membrane (CAM) on follicle outcomes in human ovarian tissue.

DESIGN

An experimental study.

SETTING

University-based research laboratory.

PATIENTS

Fresh and cryopreserved ovarian tissue from 10 patients was donated to research with their consent and institutional review board approval.

INTERVENTIONS

Fresh and frozen-thawed ovarian cortical pieces were in vitro-cultured and compared (fresh-IVC vs FT-IVC). The FT-IVC fragments were then examined against fragments grafted to CAM (FT-CAM). After both IVC and CAM grafting, ovarian cortical pieces (4×2×1 mm³) were analyzed on days 0, 1, and 6.

MAIN OUTCOME MEASURES

Follicle analyses included histology (count and classification) and immunohistochemistry (Ki67 [proliferation], caspase-3 [apoptosis], 1A and 1B light chain 3B [autophagy], p-Akt, FOXO1, and p-rpS6 [PI3K activation]). Droplet digital polymerase chain reaction further explored expression of PI3K pathway- and oocyte-related genes in tissue sections.

RESULTS

No major differences were detected between fresh-IVC and FT-IVC tissues in any conducted analyses. Although a significant drop was observed in primordial follicle (PF) proportions in the fresh-IVC and FT-IVC groups (d0 vs. d6, P<.002), they held steady in the FT-CAM group (d0 vs. d6, P>.05). The PF rates were also significantly higher in the FT-CAM group than the FT-IVC group on d6 (P=.02). Importantly, avian erythrocytes were already present in 30% of implants from d1. Apoptotic and autophagic follicle rates increased during IVC (P<.008), but remained significantly lower in the FT-CAM group (P<.01), confirming superior follicle preservation in CAM-grafted tissue. Upregulation of the PI3K/FOXO pathway was established in the IVC groups, demonstrating PF activation, whereas significant pathway downregulation was detected in the FT-CAM group (P<.03). The droplet digital polymerase chain reaction tests confirmed oocyte growth during IVC and follicle autophagy in all groups; however, the PI3K pathway appeared to be differentially modulated in tissues and follicles.

CONCLUSIONS

In vitro culture induces PF depletion with no additional impact of freezing. Grafting to CAM preserves the PF pool by curbing follicle activation, apoptosis, and autophagy, probably thanks to rapid graft revascularization and/or the circulating embryonic antimüllerian hormone. These findings highlight the importance of enhancing neoangiogenesis in ovarian grafts and investigating the potential benefits of administering antimüllerian hormone to prevent PF burnout.

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

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

Ovarian tissue cryopreservation and novel bioengineering approaches for fertility preservation

PURPOSE OF REVIEW

Breast cancer patients who cannot delay treatment or for whom hormone stimulation and egg retrieval are contraindicated require alternative methods of fertility preservation prior to gonadotoxic treatment. Ovarian tissue cryopreservation is an alternative approach that may offer patients the opportunity to preserve fertility and carry biologically-related children later in life. Various experimental approaches are being explored to obtain mature gametes from cryopreserved and thawed ovarian tissue for fertilization and implantation using biomimetic tissue culture in vitro. Here we review the most recent developments in ovarian tissue cryopreservation and exciting advances in bioengineering approaches to in vitro tissue and ovarian follicle culture.

RECENT FINDINGS

Slow freezing is the most widely accepted method for ovarian tissue cryopreservation, but efforts have been made to modify vitrification for this application as well. Numerous approaches to in vitro tissue and follicle culture are in development, most prominently two-step culture systems for ovarian cortical tissue and encapsulation of ovarian follicles in biomimetic matrices for in vitro culture.

SUMMARY

Refinements to slow freeze and vitrification protocols continue to address challenges associated with cryopreservation, such as ice crystal formation and damage to the stroma. Similarly, improvements to in vitro tissue and follicle culture show promise for utilizing patients' cryopreserved tissues to obtain mature gametes after disease treatment and remission. Development of an effective and reproducible culture system for human ovarian follicles will serve as a broad assisted reproductive technology for cancer survivors who cryopreserved tissue prior to treatment.

Progress in Fertility Preservation Strategies in Turner Syndrome

Growth retardation and gonadal dysgenesis are two of the most important clinical manifestations of Turner syndrome (TS). As premature ovarian failure generally occurs early in life in women with TS, these patients should be counseled and evaluated as early as possible for discussion of optimal and individualized fertility preservation strategies. Infertility seriously affects the quality of life of women with TS. For those who have ovarian reserve, the theoretical options for future fertility in TS patients include cryopreservation of oocytes, ovarian tissues, and embryos. For those who have already lost their ovarian reserve, oocyte or embryo donation, gestational surrogacy, and adoption are strategies that allow fulfillment of desire for parenting. This review describes the etiologies of infertility and reviews the fertility preservation strategies for women with TS.

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

Purpose

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

Methods

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

Results

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

Conclusions

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

Evaluation of a new freezing protocol containing 20% dimethyl sulphoxide concentration to cryopreserve human ovarian tissue

RESEARCH QUESTION

Could a modification in the ovarian tissue freezing protocol improve follicle survival after cryopreservation and xenotransplantation?

DESIGN

Ovarian tissue was used from 13 adult patients, frozen either with our original protocol, or a modified version involving a higher concentration of dimethyl sulphoxide (DMSO), larger volume of cryopreservation solution and lower seeding temperature. After thawing, the ovarian fragments were xenotransplanted to six mice with severe combined immunodeficiency (SCID) for 3 weeks.

RESULTS

The proportion of primordial follicles decreased, and the proportion of growing follicles increased significantly (all P < 0.01) after cryopreservation and xenografting compared with fresh controls for both protocols. Follicle density, development, ultrastructure and function were similar between treatments.

CONCLUSIONS

This study showed that, although the higher DMSO concentration did not improve survival of preantral follicles, it did not seem to induce any major toxicity in the follicle population either.

In vivo and in vitro strategies to support caprine preantral follicle development after ovarian tissue vitrification

The aim of the present study was to compare fresh and vitrified goat ovarian tissue after autotransplantation and in vitro culture. Adult goats were completely ovariectomised and each ovarian pair was sliced and distributed among six different treatment groups: fresh control, fresh transplant, fresh culture, vitrified control, vitrified transplant and vitrified culture. Follicular morphology, development, growth, density, revascularisation and hormone production were evaluated in all groups. Three antral follicles (two in the fresh transplant and one in the vitrified transplant groups) were observed on the surface of the graft 90 days after transplantation. The percentage of morphologically normal follicles was similar in the fresh control, fresh transplant and vitrified transplant groups. The percentage of developing (transition, primary and secondary) follicles was higher after in vitro culture of fresh or vitrified tissue. Transplantation resulted in a lower follicle density. Serum oestradiol concentrations remained constant during the entire transplantation period. In contrast, progesterone production decreased significantly. Expression of CD31 mRNA was lower in fresh culture. In conclusion, restoration of goat ovarian function can be successfully achieved following transplantation of both fresh and vitrified goat ovarian tissue. However, transplantation induced higher follicle loss than in vitro culture.

Ovarian injury during cryopreservation and transplantation in mice: a comparative study between cryoinjury and ischemic injury

STUDY QUESTION

What is the main cause of ovarian injury during cryopreservation and transplantation in mice: cryoinjury or ischemic injury?

SUMMARY ANSWER

Post-transplantation ischemia is the main cause of ovarian injury during cryopreservation and transplantation for restoring ovarian function.

WHAT IS KNOWN ALREADY

During cryopreservation and the transplantation of ovaries, cryoinjury and ischemic injury inevitably occur, which has a detrimental effect on ovarian quality and reserve.

STUDY DESIGN, SIZE, DURATION

A total of 80 B6D2F1 female mice were randomly allocated to 2 control and 6 experimental groups according to the presence or the absence of transplantation (n = 10/group). The control groups consisted of fresh or vitrified-warmed controls that had the whole ovary fixed without transplantation (fresh and vitri-con, respectively). The experimental groups were further divided according to the presence of vitrification (fresh or vitrified-warmed) and the transplantation period (2 [D2], 7 [D7] or 21 [D21] days).

PARTICIPANTS/MATERIALS, SETTING, METHODS

In the control groups, fresh and vitrified-warmed ovaries were immediately fixed after the collection (fresh) and the vitrification-warming process (vitrification control, vitri-con), respectively. Of those experimental groups, three were auto-transplanted with fresh whole ovary (FrOT; FrOT-D2, FrOT-D7 and FrOT-D21). For the other three groups, the ovaries were harvested and stored in liquid nitrogen for 1 week after vitrification and then warmed to auto-transplant the vitrified whole ovaries (vitrified ovary [VtOT]; VtOT-D2, VtOT-D7 and VtOT-D21). After 2, 7 or 21 days of grafting, the grafts and blood sera were collected for analysis by hematoxylin-eosin staining, terminal deoxynucleotidyl transferase dUTP nick end labeling assay, CD31 immunohistochemistry and follicle-stimulating hormone enzyme-linked immunosorbent assay.

MAIN RESULTS AND THE ROLE OF CHANCE

The vitrification-warming procedure decreased the proportion of intact follicles (Grade 1, G1) (vitri-con 50.3% versus fresh 64.2%) but there was a larger decrease due to ischemic injury after transplantation (FrOT-D2: 42.5%). The percentage of apoptotic follicles was significantly increased in the vitrified-warmed ovary group compared with the fresh control, but it increased more after transplantation without vitrification (fresh: 0.9%, vitri-con: 6.0% and FrOT-D2: 26.8%). The mean number of follicles per section and percentage of CD31-positive area significantly decreased after vitrification but decreased to a larger extent after transplantation (number of follicles, fresh: 30.3 ± 3.6, vitri-con: 20.6 ± 2.9, FrOT-D2: 17.9 ± 2.1; CD31-positive area, fresh: 10.6 ± 1.3%, vitri-con: 5.7 ± 0.9% and FrOT-D2: 4.2 ± 0.4%). Regarding the G1 follicle ratio and CD31-positive area per graft, only the FrOT groups significantly recovered with time after transplantation (G1 follicle ratio, FrOT-D2: 42.5%, FrOT-D7: 56.1% and FrOT-D21: 70.7%; CD31-positive area, FrOT-D2: 4.2 ± 0.4%, FrOT-D7: 5.4 ± 0.6% and FrOT-D21: 7.5 ± 0.8%). Although there was no significant difference between the two transplantation groups at each evaluation, the serum follicle-stimulating hormone level of both groups significantly decreased over time.

LIMITATIONS AND REASONS FOR CAUTION

It is unclear how far these results can be extrapolated from mice to the human ovary.

WIDER IMPLICATIONS OF THE FINDINGS

Minimizing ischemic injury should be the first priority rather than preventing cryoinjury alone, and decreasing the combination of cryoinjury and ischemic injury is necessary to improve ovarian quality after cryopreservation and transplantation.

STUDY FUNDING/COMPETING INTEREST

This study was supported by a grant of the Korea Healthcare Technology R&D Project, Ministry of Health & Welfare, Republic of Korea (HI12C0055). The authors have no conflict of interest to declare.

Morphometric characteristics of preantral and antral follicles and expression of factors involved in folliculogenesis in ovaries of adult baboons (Papio anubis)

PURPOSE

Baboons are commonly utilized as an animal model for studies of human reproduction. However, folliculogenesis in this species has not been fully documented. The aim of this study was to assess follicle morphometry and expression of essential proteins involved in folliculogenesis in baboons.

METHODS

Ovaries were recovered from four adult baboons and processed for histological evaluation and immunohistochemical analyses. Follicle proportion, follicle and oocyte diameter, theca layer thickness, number of granulosa cells, and follicle density were calculated. Immunohistochemical staining was also carried out for connexin 43 (Cx43), aromatase, and zona pellucida 3 (ZP3).

RESULTS

A total of 2221 follicles were counted and measured. Proportions of primordial, primary, secondary, small antral, and large antral follicles were 49, 26, 23, 1, and 1 %, respectively. The increase in follicle diameter was due not only to the increase in oocyte diameter but also to granulosa cell proliferation. Almost all antral follicles were positive for Cx43 (89.8 %), aromatase (84.8 %), and ZP3 (100 %). Most secondary follicles were positive for Cx43 (65 %) and ZP3 (64.5 %), and some primary follicles were positive only for Cx43. No primordial follicles stained positive in any of these immunohistochemical analyses. Only antral follicles showed aromatase activity.

CONCLUSIONS

On the basis of these results, we can conclude that folliculogenesis in baboons appears to be similar to that in humans, and this animal therefore constitutes a valuable model.

An externally validated age-related model of mean follicle density in the cortex of the human ovary

Purpose

The ability to accurately estimate a woman’s ovarian reserve by non-invasive means is the goal of ovarian reserve prediction. It is not known whether a correlation exists between model-predicted estimates of ovarian reserve and data generated by direct histological analysis of ovarian tissue. The aim of this study was to compare mean non-growing follicle density values obtained from analysis of ovarian cortical tissue samples against ovarian volume models.

Methods

Non-growing follicle density values were obtained from 13 ovarian cortical biopsies (16-37 years). A mean non-growing follicle density was calculated for each patient by counting all follicles in a given volume of biopsied ovarian cortex. These values were compared to age-matched model generated densities (adjusted to take into consideration the proportion of ovary that is cortex) and the correlation between data sets tested.

Results

Non-growing density values obtained from fresh biopsied ovarian cortical samples closely matched model generated data with low mean difference, tight agreement limits and no proportional error between the observed and predicted results.

Conclusion

These findings validate the use of the adjusted population and ovarian volume models, to accurately predict mean follicle density in the ovarian cortex of healthy adult women.

Trolox enhances follicular survival after ovarian tissue autograft in squirrel monkey (Saimiri collinsi)

The aim of this study was to evaluate ovarian tissue pre-treatment with 50 µM Trolox followed by heterotopic transplantation in squirrel monkeys (Saimiri collinsi) and to assess tissue functionality via immunohistochemical analysis of the stroma and ovarian follicles. Five healthy and sexually mature squirrel monkey (Saimiri collinsi) females were used. Heterotopic autografting of fresh ovarian tissue with or without previous exposure to the antioxidant Trolox was performed and grafts were recovered for analysis 7 days later. Tissue vascularisation was confirmed by both macroscopic inspection and cluster of differentiation 31 (CD31) staining. Trolox prevented massive follicular activation and kept the percentages of morphologically normal follicles higher than in untreated grafts. Expression of anti-Müllerian hormone in developing follicles was observed only in controls and Trolox-treated grafts. Also, immunostaining for growth differentiation factor-9 was positive only in primordial follicles from controls and from Trolox-treated grafts. Although Trolox improved follicular quality and avoided apoptosis in stromal cells, ovarian tissue fibrosis was increased in Trolox-treated grafts, mainly due to an increase in collagen Type I synthesis.

Xenotransplantation of cryopreserved human ovarian tissue--a systematic review of MII oocyte maturation and discussion of it as a realistic option for restoring fertility after cancer treatment

OBJECTIVE

To systematically review the reporting of MII (MII) oocyte development after xenotransplantation of human ovarian tissue.

DESIGN

Systematic review in accordance with the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA).

SETTING

Not applicable.

PATIENT(S)

Not applicable.

INTERVENTION(S)

Formation of MII oocytes after xenotransplantation of human ovarian tissue.

MAIN OUTCOME MEASURE(S)

Any outcome reported in Pubmed.

RESULT(S)

Six publications were identified that report on formation of MII oocytes after xenotransplantation of human ovarian tissue.

CONCLUSION(S)

Xenografting of human ovarian tissue has proved to be a useful model for examining ovarian function and follicle development in vivo. With human follicles that have matured through xenografting, the possibility of cancer transmission and relapse can also be eliminated, because cancer cells are not able to penetrate the zona pellucida. The reported studies have demonstrated that xenografted ovarian tissue from a range of species, including humans, can produce antral follicles that contain mature (MII) oocytes, and it has been shown that mice oocytes have the potential to give rise to live young. Although some ethical questions remain unresolved, xenotransplantation may be a promising method for restoring fertility. This review furthermore describes the value of xenotransplantation as a tool in reproductive biology and discusses the ethical and potential safety issues regarding ovarian tissue xenotransplantation as a means of recovering fertility.

Isoform 165 of vascular endothelial growth factor in collagen matrix improves ovine cryopreserved ovarian tissue revascularisation after xenotransplantation in mice

BACKGROUND

Aggressive anti-cancer treatments can result in ovarian failure. Ovarian cryopreservation has been developed to preserve the fertility of young women, but early graft revascularisation still requires improvement.

METHODS

Frozen/thawed sheep ovarian cortical biopsies were embedded in collagen matrix with or without isoform 165 of vascular endothelial growth factor (VEGF165) and transplanted into ovaries of immunodeficient mice. Ovaries were chosen as transplantation sites to more closely resemble clinical conditions in which orthotopic transplantation has previously allowed several spontaneous pregnancies.

RESULTS

We found that VEGF165 significantly increased the number of Dextran-FITC positive functional vessels 3 days after grafting. Dextran- fluorescein isothiocyanate (FITC) positive vessels were detectable in 53% and 29% of the mice in the VEGF-treated and control groups, respectively. Among these positive fragments, 50% in the treated group displayed mature smooth-muscle-actin-alpha (alpha-SMA) positive functional vessels compared with 0% in the control group. CD31 positive murine blood vessels were observed in 40% of the VEGF165 transplants compared with 21% of the controls. After 3 weeks, the density of murine vessels was significantly higher in the VEGF165 group.

CONCLUSION

The encapsulation of ovarian tissue in collagen matrix in the presence of VEGF165 before grafting has a positive effect on functional blood vessel recruitment. It can be considered as a useful technique to be improved and further developed before human clinical applications in female cancer patients in the context of fertility preservation.

Immunolocalization of growth, inhibitory, and proliferative factors involved in initial ovarian folliculogenesis from adult common squirrel monkey (Saimiri collinsi)

We performed an immunohistochemical (IHC) study to determine the follicular expression of growth differentiation factor 9 (GDF-9), anti-Müllerian hormone (AMH), Kit Ligand (KL), and c-Kit in squirrel monkey ovary. Ovarian tissue fragments from 4 squirrel monkeys were collected by laparotomy and processed for classical histology and IHC. Additionally, follicle development was assessed by Ki67 immunostaining to evaluate proliferative status of granulosa cells. A total of 4025 follicles were examined (1475 for classical histology and 2550 for immunohistochemistry). More than 80% of the evaluated follicles were morphologically normal. The GDF-9 protein was detectable in oocyte cytoplasm from primordial (100%), primary (99.1%), and secondary (100%) follicles. The AMH was not expressed in primordial follicles but just in few primary follicles (13.8%). On the other hand, it was highly expressed in granulosa cells from secondary follicles (67.9%). c-Kit, KL receptor, was found in the oolemma of primordial (100%), primary (100%), and secondary (100%) follicles. The KL expression was observed in oocytes and granulosa cells from primordial (94.9%), primary (91.6%) and secondary follicles (100%). Ki67 immunostaining was observed in granulosa cells from primary (5.7%) and secondary (54.8%) follicles but not in primordial follicles. In conclusion, we described the localization of GDF-9, KL, c-Kit, and Ki67 proteins and confirmed the presence of AMH protein in preantral follicles from squirrel monkey. Our results offer contribution for understanding of folliculogenesis in neotropical nonhuman primates. Moreover, these markers can be used to assess follicular viability and functionality after cryopreservation, transplantation, or in vitro culture of ovarian tissue.

Females transplanted with ovaries subjected to hypoxic preconditioning show impair of ovarian function

Background

Cryopreservation of the ovarian tissue has shown promising results. However, there remain controversial issues such as the short half-life of grafts. In this aspect, there are some evidences that preconditioning the ovarian tissue before transplantation is beneficial.

Objective

To determine the effect of hypoxic preconditioning in vitro on ovarian tissue prior to transplantation.

Methods

Eighteen female adult Wistar rats, were sorted into three experimental groups. Ovaries were maintained in DMEM low glucose serum free at 37°C with 5% CO2, at atmospheric oxigen concentration (normoxia) or 1% O₂ (hypoxia) for 16 hours. Oxigen concentration was determined by injection of nitrogen in the incubator. Animals submitted to ovarian transplantation immediately after oophorectomy were the Control Group (C). After this, the ovaries were implanted in the retroperitoneum with nonabsorbable suture and animals evaluated for thirty days after transplantation. Beginning on postoperative (PO) day 11, a daily collection of vaginal smear was carried out. Analyses comprised morphological, morphometric (counting ovarian follicles and corpora lutea) and immunohistochemistry for cleaved caspase-3 (apoptosis).

Results

In normoxia and control groups all animals recovered their estrous cycles, while in the hypoxia group, two animals did not ovulate but, among those which did, resumption took longer than in the other groups (p < 0.05). The number of ovarian follicles and corpora lutea decreased significantly in the hypoxia group when compared to the other two groups (p < 0.001) and apoptosis was increased in the few ovarian follicles which remained viable (p < 0.001).

Conclusion

The hypoxic preconditioning in vitro was not beneficial to the graft and worsened their viability, compromising its functionality or delaying the return of this.

Strategies for using the sheep ovarian cortex as a model in reproductive medicine

OBJECTIVE

To evaluate and compare the distribution and density of primordial follicles within a whole sheep ovary and to gain insight into how to overcome the impact of natural follicular heterogeneity on the experimental results.

DESIGN

Histological study.

SETTING

Academic research center.

ANIMALS

Five- to nine-month-old ewes.

INTERVENTIONS

Freshly sampled whole sheep ovaries were collected and prepared for histological analysis.

MAIN OUTCOME MEASURE(S)

The follicular densities and distributions were determined for hematoxylin and eosin sections. A mathematical model was derived based on the follicle counts and Monte-Carlo simulations.

RESULTS

Heterogeneous distributions and densities of primordial follicles were identified 1) for distinct areas of the same ovarian cortex, 2) between the ovaries of the same animal and 3) across different ewes. A mathematical model based on the analysis of 37,153 primordial follicles from 8 different ovaries facilitated the estimation of the number of cortical biopsies and sections that had to be analyzed to overcome such heterogeneity.

CONCLUSION

The influence of physiological follicular heterogeneity on experimental and clinical results can be overcome when a definite number of cortical pieces and sections are taken into consideration.

Does stimulation with human gonadotropins and gonadotropin-releasing hormone agonist enhance and accelerate the developmental capacity of oocytes in human ovarian tissue xenografted into severe combined immunodeficient mice?

OBJECTIVE

To assess the capacity of human frozen-thawed ovarian follicles matured in xenografts to form metaphase II (MII) oocytes after xenotransplantation and exogenous stimulation.

DESIGN

Prospective controlled animal study.

SETTING

University hospital gynecology research unit.

PATIENT(S)

Ovarian fragments were obtained from 17 women with malignant diseases who wished to cryopreserve ovarian tissue for later pregnancy before chemotherapy.

ANIMAL(S)

Eighty-eight female severe combined immunodeficient (SCID) mice.

INTERVENTION(S)

Cryopreserved human ovarian tissue was grafted into oophorectomized SCID mice. The mice were divided into three groups: Group A received hMG alone every 2 days for a maximum of 24 weeks; group B additionally received nRH agonist (GnRHa) every 4 weeks; and group C was an untreated control group.

MAIN OUTCOME MEASURE(S)

Follicular density, morphology, proliferation, oocyte maturation, malignant cell contamination.

RESULT(S)

Follicle survival and development were similar in all three groups. No significant interactions between the stimulation protocols and grafting duration were noted. Three MII oocytes were observed in grafted follicles. Two MII oocytes were harvested without stimulation. None of the mice showed signs of reintroduced malignancy, nor did microscopic evaluation of the grafts raise any suspicion of residual malignant disease.

CONCLUSION(S)

After xenotransplantation, human primordial follicles can be matured to MII oocytes even without stimulation. Administering human gonadotropin and GnRHa does not enhance the developmental capacity of xenografted oocytes. The optimal stimulation schedule for grafted tissue remains unknown.

Fertility preservation in women

In women, ∼10% of cancers occur in those <45 years old. Chemotherapy, radiotherapy and bone marrow transplantation can cure >90% of girls and young women with diseases that require such treatments. However, these treatments can result in premature ovarian failure, depending on the follicular reserve, the age of the patient and the type and dose of drugs used. This article discusses the different fertility preservation strategies: medical therapy before chemotherapy; ovarian transposition; embryo cryopreservation; oocyte vitrification; and ovarian tissue cryopreservation. The indications, results and risks of these options are discussed. Whether medical therapy should be used to protect the gonads during chemotherapy remains a source of debate. Fertility preservation needs to be completed before chemotherapy and/or irradiation is started and might take 2-3 weeks with established techniques such as embryo or oocyte cryopreservation. Further studies are needed in patients with cancer to confirm the excellent outcomes obtained in patients without cancer or in egg donation programmes. For prepubertal girls or cases where immediate therapy is required, cryopreservation of ovarian tissue is the only available option. Finally, possible future approaches are reviewed, including in vitro maturation of nonantral follicles, the artificial ovary, oogonial stem cells and drugs to prevent follicle loss.

VEGF and bFGF increase survival of xenografted human ovarian tissue in an experimental rabbit model

PURPOSE

The aim of this study is to determine whether vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) could increase the survival of xenografted human ovarian tissue in an experimental rabbit model.

METHODS

Fresh human ovarian tissue was xenotransplanted into the back muscle of 25 castrated female New Zealand rabbits for 6 weeks with the immunosuppression of FTY720 (2 mg/kg/d). Rabbits were randomly divided into five experimental groups: (A) graft and host treatment with VEGF (50 ng/ml); (B) graft and host treatment with bFGF (100 ng/ml); (C) graft and host treatment with VEGF(50 ng/ml) + bFGF (100 ng/ml); (D) graft and host treatment with normal saline; (E) control group, no treatment. 4 weeks after transplantation, human menopausal gonadotropin (HMG) 10 IU was administered every second day in group A, group B, group C and group D for 2 weeks. Graft survival was assessed by graft recovery rate, histological analysis, immunohistochemical staining for CD31 and Ki-67expression, TUNEL assay.

RESULTS

After 6 weeks of grafting, the number of CD31-positive stained cells increased significantly in group A, group B and group C compared to the control group. All groups showed strong Ki-67 immunostaining in ovarian stroma. Only one rabbit in group C retained the grafts' follicles. Grafting resulted in relative lower fibrosis in group A and group C compared to the control group. Apoptosis was significantly lower in group C compared to the control group.

CONCLUSIONS

Fresh human ovarian cortex grafted into the back muscle of rabbit can sustain part of ovarian tissue function with the immunosuppression of FTY720, although follicle number diminishes significantly after grafting. The administration of VEGF and bFGF, especially the combination of them, may trigger angiogenesis, reduce apoptosis and fibrosis, increase survival in transplanted human ovarian tissue.

Transplantation of an alginate-matrigel matrix containing isolated ovarian cells: first step in developing a biodegradable scaffold to transplant isolated preantral follicles and ovarian cells

For women diagnosed with leukemia, transplantation of cryopreserved ovarian tissue after disease remission is not advisable. Therefore, to restore fertility in these patients, we aim to develop a biodegradable artificial ovary that offers an environment where isolated follicles and ovarian cells (OCs) can survive and grow. Four NMRI mice were ovariectomized and their ovaries used to isolate OCs. Groups of 50,000 OCs were embedded in an alginate-matrigel matrix for further fixation (fresh controls), one week of in vitro culture (IVC) or heterotopic autografting. OC proliferation (Ki67), apoptosis (TUNEL), scaffold degradation, vessel formation (CD34) and inflammation (CD45) were analyzed. Ki67-positive OCs were found in 2.3%, 9.0% and 15.5% cells of cases in fresh, IVC and grafted beads respectively, while cells were TUNEL-positive in 0%, 1.5% and 6.9% of cases. After IVC or grafting, the beads degraded, losing their original round aspect, and infiltrating blood capillaries could be observed in the grafted beads. CD34-positive cells and 22% CD45-positive cells were found around and inside the matrix. In conclusion, our results demonstrate that an alginate-based matrix is a promising proposition to graft isolated OCs. After transplantation, this matrix was able to degrade, allowed vascularization and elicited a low inflammatory response.

Effect of cryopreservation and transplantation on the expression of kit ligand and anti-Mullerian hormone in human ovarian tissue

BACKGROUND

Although cryopreservation and transplantation of ovarian tissue represent a promising alternative to safeguard fertility in cancer patients, low recovery rates of oocytes aspirated from antral follicles and a significant number of empty follicles have been observed in women with transplanted frozen-thawed ovarian tissue. In order to understand how freezing and/or grafting may affect follicular development, the follicular expression of kit ligand (KL) and anti-Müllerian hormone (AMH), two key factors activating and inhibiting follicle growth, were assessed after long-term grafting in severe combined immunodeficient (SCID) mice.

METHODS

Ovarian biopsies from eight patients were used for fresh and frozen-thawed tissue xenografting in 13 SCID mice for a period of 28 weeks, including 2 weeks of gonadotrophin stimulation. KL, AMH and proliferating cell nuclear antigen (PCNA) immunostaining were quantified before and after grafting in the two treatment groups (fresh and frozen-thawed grafted ovarian tissue).

RESULTS

Lower expression of KL was found in primordial and primary follicles after grafting of both fresh and frozen-thawed tissue. Consistent expression of AMH was found in most growing follicles at a similar rate in both graft types. In fresh and frozen-thawed grafts, 13-14% of primordial follicles were PCNA-positive, indicating a similar maintenance of quiescent follicles despite follicle activation.

CONCLUSIONS

Grafting and/or gonadotrophin stimulation appear to affect the follicular expression of KL, which may alter oocyte quality. AMH expression in growing follicles after ovarian tissue transplantation may be one of the factors contributing to the preservation of resting follicles in 28-week-old grafts.

Impact of freezing and thawing of human ovarian tissue on follicular growth after long-term xenotransplantation

PURPOSE

To assess follicular growth after xenografting in order to understand how freezing and/or grafting may affect follicular development.

METHODS

Human ovarian biopsies were used for fresh and frozen-thawed xenografting to SCID mice. After xenotransplantation, follicular morphology and proportion, oocyte and follicle diameter, and quantitative and qualitative parameters of antral follicles were analyzed.

RESULTS

The proportion of growing follicles was significantly higher in grafted than non-grafted ovarian tissue. Follicular growth to the antral stage was observed and there was no significant difference in oocyte or follicle diameter in fresh or frozen-thawed grafts. Although no significant difference was observed in antral area or zona pellucida thickness, the theca layer in antral follicles from frozen-thawed grafted tissue was found to be significantly thinner than in fresh grafts.

CONCLUSION

Antral follicles obtained after grafting of frozen-thawed human ovarian tissue showed a thinner theca cell layer compared to those from fresh grafts, which could affect follicular development and function. Further studies are nevertheless warranted to confirm the identity of theca cells and assess if they retain the ability to respond to luteinizing hormone and produce androgens.