Benefits of 8-bromo-guanosine 3',5'-cyclic monophosphate (8-br-cGMP) in human ovarian cortical tissue culture

Biomarkers identification in follicular fluid of women with OHSS by using UPLC-MS method

To figure out the differentially changed metabolites and disturbed pathways in follicular fluid (FF) of patients with OHSS in comparison to the control group undergoing in vitro fertilization (IVF), we conducted this metabolomic analysis between two groups, the OHSS group included 30 patients treated with oocyte retrieval and developed OHSS in the next 7-14 days, while another 30 patients without OHSS tendency were selected as the control group. The FF samples were obtained during the process of oocyte retrieval. FF samples were analyzed using ultra-high liquid chromatography-tandem mass spectrometry (UPLC-MS). The results identified a total of 59 differentially changed metabolites, including 33 decreased metabolites (P < 0.01) and 26 increased metabolites (P < 0.01) in FF of OHSS compared with the control group. 12 metabolites could be the most valuable biomarkers for OHSS based on ROC results. Our correlation analyses showed that deoxyinosine levels were found positively correlated with serum estradiol (E2) levels in OHSS patients, while L-isoleucine, pyruvic acid, maleamate, and arachidonic acid were found to be positively correlated with the number of retrieved oocytes. Furthermore, 4-hydroxyphenylacetaldehyde, deoxycorticosterone, creatinine, and creatine were found to be negatively associated with serum E2 levels, while 4-hydroxyphenylacetaldehyde, L-carnitine, isovaleric acid and L-2-hydroxyglutaric acid were negatively related with the number of oocytes retrieved in OHSS patients. Taken together, our study provides better identification of OHSS FF metabolic dynamics, suggesting the metabolic compounds can be used as valuable predictors or treatment targets of OHSS.

Human ovarian tissue in-vitro culture: primordial follicle activation as a new strategy for female fertility preservation

Cryopreservation and transplantation of ovarian tissue is the only fertility preservation option used for prepubertal girls and women who don't have a chance for embryo or oocyte vitrification. For women with aggressive cancer, hormone-responsive malignancies, autoimmune diseases, etc. ovary transplantation cannot be performed so an alternative technology called in-vitro follicle activation is thinkable. In this method, dormant primordial follicles are activated from the resting primordial pool by in-vitro culture and enter their growth phase. Different in-vitro culture media and supplements in addition to various culturing methods have been conducted for activating these dormant follicles. Furthermore, several signaling pathways such as Hippo, phosphatidylinositol-3-kinase, and mTOR influence follicle activation. Therefore, the addition of different activators of these signaling pathways can beneficially regulate this culture system. This review summarizes the findings on different aspects of human ovarian tissue culture strategies for in-vitro follicular activation, their medium, and different factors involved in this activation. Afterward, signaling pathways important for follicle activation and their clinical applications towards improving activation in culture are also reviewed.

The effect of agar substrate on growth and development of cryopreserved-thawed human ovarian cortical follicles in organ culture

OBJECTIVE

To preserve human ovarian tissue structure and improve follicular growth and survival during in-situ culture, various biomaterials are used. In this study we aimed to compare agar as a cultivation substrate with matrigel-coated insert in order to achieve an optimum system for in-situ human follicle culture.

STUDY DESIGN

Frozen-thawed human ovarian cortical tissues were cultured on either matrigel-coated inserts or agar-soaked substrates. The proportion of morphologically viable and degenerated follicles at different developmental stages, secreted hormonal levels, and apoptotic and proliferation gene expressions were compared between the cultured groups after 7-days of culture.

RESULTS

The follicular growth was not significantly different between the two cultured groups, although showing higher percentage of growing follicles in agar cultured group. The secreted hormonal levels didn't have any difference between two cultured groups. Although the apoptotic gene expressions didn't show any difference between the cultured groups, the apoptotic index was lower in agar cultured group. In addition, Ki67 gene expression, a proliferative marker, showed a significantly higher expression in agar cultured group.

CONCLUSION

Based on the results, agar is as suitable as matrigel-coated inserts for the survival and growth of follicles during culture. Therefore, agar can be an inexpensive alternative substrate for culturing frozen-thawed human ovarian cortical strips.

Human umbilical cord stem cell conditioned medium versus serum-free culture medium in the treatment of cryopreserved human ovarian tissues in in-vitro culture: a randomized controlled trial

BACKGROUND

To reduce young female fertility loss, the in-vitro culture of cryopreserved ovarian cortical tissues (OCTs) is considered an effective approach without delaying treatment and undergoing stimulation medicine. However, ischemic damage and follicular loss during the in-vitro culture of OCTs are major technical challenges. Human umbilical cord stem cells (HUMSCs) and their conditioned medium (HUMSC-CM) have been considered to be potential resources for regeneration medicine because they secrete cytokines and enhance cell survival and function. The aim of this study was to determine whether HUMSC-CM improves the development of frozen-thawed in-vitro cultured ovarian tissues compared with a serum-free culture medium (SF-CM).

METHODS

The thawed OCTs (n = 68) were cultivated in HUMSC-CM and SF-CM in vitro for 8 days, and the ovarian tissues were processed and analyzed by a classical histological evaluation. The microvessel density (MVD) and apotosis detection during in-vitro culture of OCTs were also performed.

RESULTS

A significant difference in the rate of morphologically normal primordial follicles in the HUMSC-CM group was observed compared to that in the SF-CM group (group C) from days 2 to 4 (day 2: group B 58.0 ± 2.45% vs group C 32.0 ± 5.83%, p = 0.002; day 3: group B 55.5 ± 4.20% vs group C 21.0 ± 9.80%, p = 0.048; day 4: group B 52.0 ± 4.08% vs group C 21.5 ± 8.19%, p = 0.019). The microvessel density (MVD) detection showed a time-dependent increase and peaked on day 4. There was a significant difference between groups B (49.33 ± 0.58) and C (24.33 ± 3.79) (p = 0.036). The percentage of apoptotic follicles in group B was lower than that in group C on day 1 (13.75 ± 2.50% vs 27.0 ± 10.10%, p = 0.003), day 5 (11.75 ± 1.50% vs 51.0 ± 10.5%, p = 0.019) and day 7 (15.0 ± 5.10% vs 46.5 ± 21.75%, p = 0.018).

CONCLUSIONS

These data have provided the first experimental evidence of the effect of HUMSC-CM on frozen-thawed OCTs in vitro. The results showed that the HUMSC-CM group provided a better protecting effect on the in-vitro culture of the cryopreserved OCTs compared to the SF-CM group.

Ovarian tissue culture in the presence of VEGF and fetuin stimulates follicle growth and steroidogenesis

Ovarian tissue cryopreservation together with follicle culture provides a promising technique for fertility preservation in cancer patients. The study aimed to evaluate follicle parameters in a culture medium supplemented with VEGFA165 and/or fetuin. Vitrified-warmed ovarian cortical pieces were divided randomly into four culture groups consisting of basic culture medium (control), and the basic culture medium supplemented with VEGFA165, fetuin or both. After six days of culture, we evaluated the following: percentage of resting, primary and secondary growing follicles; survival rate; steroid hormones production; levels of reactive oxygen species, lipid peroxidation and total antioxidant capacity; and developmental and antioxidant gene expression. The addition of VEGFA165 alone or in combination with fetuin to the culture medium caused resting follicle activation and increased the number of growing follicles. In the VEGFA165 group, we found a significant increase in the concentrations of 17β-estradiol at day 6 and progesterone from 4th day of the culture period. In the VEGFA165 + fetuin group, the concentration of 17β-estradiol rose at day 4 of the culture period. The levels of BMP15, GDF9 and INHB mRNAs were increased in all treated groups. In the fetuin and fetuin + VEGFA165 groups, we observed a high level of total antioxidant capacity and expression of SOD1 and CAT genes, low reactive oxygen species and lipid peroxidation levels and increased number of viable follicles. In conclusion, the present study provides useful evidence that supplementation of culture medium with VEGFA165 + fetuin leads to primordial follicle activation and development and increased percentage of healthy secondary growing follicles.

Alginate encapsulation supports the growth and differentiation of human primordial follicles within ovarian cortical tissue

PURPOSE

In vitro follicle growth (IVFG) is an investigational fertility preservation technique in which immature follicles are grown in culture to produce mature eggs that can ultimately be fertilized. Although progress has been made in growing primate primary and secondary follicles in vitro, it has been a relatively greater challenge to isolate and culture primordial follicles. The purpose of this study was to develop methods to grow human primordial follicles in vitro using alginate hydrogels.

METHODS

We obtained human ovarian tissue for research purposes through the National Physicians Cooperative from nationwide sites and used it to test two methods for culturing primordial follicles. First, primordial follicles were isolated from the ovarian cortex and encapsulated in alginate hydrogels. Second, 1 mm × 1 mm pieces of 500 μm-thick human ovarian cortex containing primordial follicles were encapsulated in alginate hydrogels, and survival and follicle development within the tissue was assessed for up to 6 weeks.

RESULTS

We found that human ovarian tissue could be kept at 4 °C for up to 24 h while still maintaining follicle viability. Primordial follicles isolated from ovarian tissue did not survive culture. However, encapsulation and culture of ovarian cortical pieces supported the survival, differentiation, and growth of primordial and primary follicles. Within several weeks of culture, many of the ovarian tissue pieces had formed a defined surface epithelium and contained growing preantral and antral follicles.

CONCLUSIONS

The early stages of in vitro human follicle development require the support of the native ovarian cortex.

Multiple follicle culture supports primary follicle growth through paracrine-acting signals

In vitro follicle growth in alginate hydrogels is a unique and versatile method for studying ovarian and follicle biology that may also have implications for fertility preservation. Current culture systems support the development of isolated mouse follicles from the secondary stage onward. However, it has been a challenge to grow smaller follicles in vitro due to the dissociation of the oocyte from companion somatic cells. Recent work has demonstrated that coculturing primary follicles with mouse embryonic fibroblasts or ovarian stromal cells supports follicle survival and growth. In this study, we demonstrate that follicles themselves can exert a beneficial coculture effect. When primary follicles were cultured in groups of five or ten (multiple follicle culture), there was increased growth and survival. The multiple follicle culture approach maintained follicle integrity and resulted in the formation of antral stage follicles containing meiotically competent gametes. The growth and survival of primary follicles were highly number dependent, with the most significant enhancement observed when the largest number of follicles was grown together. Our data suggest that the follicle unit is necessary to produce the secreted factors responsible for the supportive effects of multiple follicle culture, as neither denuded oocytes, oocyte-secreted factors, nor granulosa cells alone were sufficient to support early follicle growth in vitro. Therefore, there may be signaling from both the oocyte and the follicle that enhances growth but requires both components in a feedback mechanism. This work is consistent with current in vivo models for follicle growth and thus advances the movement to recapitulate the ovarian environment in vitro.

Alginate scaffold for organ culture of cryopreserved-thawed human ovarian cortical follicles

PURPOSE

To compare macroporous alginate scaffolds with Matrigel for culturing frozen-thawed human primordial follicles in organ culture.

METHODS

Twelve girls/women donated ovarian tissue. One tissue sample was fixed immediately after thawing (uncultured samples). Slices were cultured for 2 weeks on either Matrigel or on alginate scaffolds with a serum-free culture medium. Growth evaluation consisted of follicular counts and classification, immunohistochemistry and measurement of 17β-Estradiol (E(2)) production.

RESULTS

The number of developing follicles was significantly higher in alginate scaffold-cultured samples than on Matrigel with a concomitant decrease in the number of primordial follicles in alginate scaffold-cultured samples than uncultured samples. The number of atretic follicles after 1 week was significantly higher in the Matrigel-cultured samples than in the alginate scaffold cultured samples. E(2) production was similar in both groups.

CONCLUSIONS

Three dimensional alginate scaffolds are a promising putative in vitro technology for developing human primordial follicles.

In vitro oocyte maturation and preantral follicle culture from the luteal-phase baboon ovary produce mature oocytes

Female cancer patients who seek fertility preservation but cannot undergo ovarian stimulation and embryo preservation may consider 1) retrieval of immature oocytes followed by in vitro maturation (IVM) or 2) ovarian tissue cryopreservation followed by transplantation or in vitro follicle culture. Conventional IVM is carried out during the follicular phase of menstrual cycle. There is limited evidence demonstrating that immature oocyte retrieved during the luteal phase can mature in vitro and be fertilized to produce viable embryos. While in vitro follicle culture is successful in rodents, its application in nonhuman primates has made limited progress. The objective of this study was to investigate the competence of immature luteal-phase oocytes from baboon and to determine the effect of follicle-stimulating hormone (FSH) on baboon preantral follicle culture and oocyte maturation in vitro. Oocytes from small antral follicle cumulus-oocyte complexes (COCs) with multiple cumulus layers (42%) were more likely to resume meiosis and progress to metaphase II (MII) than oocytes with a single layer of cumulus cells or less (23% vs. 3%, respectively). Twenty-four percent of mature oocytes were successfully fertilized by intracytoplasmic sperm injection, and 25% of these developed to morula-stage embryos. Preantral follicles were encapsulated in fibrin-alginate-matrigel matrices and cultured to small antral stage in an FSH-independent manner. FSH negatively impacted follicle health by disrupting the integrity of oocyte and cumulus cells contact. Follicles grown in the absence of FSH produced MII oocytes with normal spindle structure. In conclusion, baboon luteal-phase COCs and oocytes from cultured preantral follicles can be matured in vitro. Oocyte meiotic competence correlated positively with the number of cumulus cell layers. This study clarifies the parameters of the follicle culture system in nonhuman primates and provides foundational data for future clinical development as a fertility preservation option for women with cancer.

Meiosis in a bottle: new approaches to overcome Mammalian meiocyte study limitations

The study of meiosis is limited because of the intrinsic nature of gametogenesis in mammals. One way to overcome these limitations would be the use of culture systems that would allow meiotic progression in vitro. There have been some attempts to culture mammalian meiocytes in recent years. In this review we will summarize all the efforts to-date in order to culture mammalian sperm and oocyte precursor cells.

Current achievements and future research directions in ovarian tissue culture, in vitro follicle development and transplantation: implications for fertility preservation

BACKGROUND Female cancer patients are offered 'banking' of gametes before starting fertility-threatening cancer therapy. Transplants of fresh and frozen ovarian tissue between healthy fertile and infertile women have demonstrated the utility of the tissue banked for restoration of endocrine and fertility function. Additional methods, like follicle culture and isolated follicle transplantation, are in development. METHODS Specialist reproductive medicine scientists and clinicians with complementary expertise in ovarian tissue culture and transplantation presented relevant published literature in their field of expertise and also unpublished promising data for discussion. As the major aims were to identify the current gaps prohibiting advancement, to share technical experience and to orient new research, contributors were allowed to provide their opinioned expert views on future research. RESULTS Normal healthy children have been born in cancer survivors after orthotopic transplantation of their cryopreserved ovarian tissue. Longevity of the graft might be optimized by using new vitrification techniques and by promoting rapid revascularization of the graft. For the in vitro culture of follicles, a successive battery of culture methods including the use of defined media, growth factors and three-dimensional extracellular matrix support might overcome growth arrest of the follicles. Molecular methods and immunoassay can evaluate stage of maturation and guide adequate differentiation. Large animals, including non-human primates, are essential working models. CONCLUSIONS Experiments on ovarian tissue from non-human primate models and from consenting fertile and infertile patients benefit from a multidisciplinary approach. The new discipline of oncofertility requires professionalization, multidisciplinarity and mobilization of funding for basic and translational research.

Fertility preservation in girls during childhood: is it feasible, efficient and safe and to whom should it be proposed?

BACKGROUND

In prepubertal and adolescent girls, fertility may be impaired by gonadotoxic treatments, repeat ovarian surgery or genetic disorders. Cryopreservation of ovarian cortex is an existing option to preserve fertility in these young girls at risk of premature ovarian failure (POF). The efficacy, feasibility and risks of ovarian cryopreservation in children must be assessed in order to validate the technique.

METHODS

Here, we conducted a review of ovarian cryopreservation in adults and, more specifically, in children using the PubMed databases. In addition, our own experience with ovarian cryopreservation in children was evaluated and compared with the literature.

RESULTS

Analysis of the literature and six published series on ovarian cryopreservation in children, as well as our own series of 58 cases, show that there is no reason to doubt its efficacy in this young population. However, no consensus has yet been reached on the indications for the technique. Indeed, with existing models, the real risk of POF may be over- or underestimated.

CONCLUSION

Our review suggests that ovarian cortex cryopreservation is feasible and as safe as comparable operative procedures in children. Although no births have yet resulted from freeze-thawing of prepubertal ovarian cortex, the results of this approach in adults are encouraging. However, the absence of consensus on the indications for fertility preservation, as well as the optimal timing and quantity of ovarian cortex for cryopreservation, should be taken into consideration when discussing fertility issues with girls at risk of POF and their parents.

Preserving female fertility following cancer treatment: current options and future possibilities

Children and women of reproductive age are increasingly surviving cancer diagnoses, and therefore long-term quality-of-life issues are of greater importance at the time of diagnosis. Cancer therapies including radiation and chemotherapy can be detrimental to fertility, and therefore many patients are motivated to preserve fertility prior to cancer treatment. The only highly successful method in preserving fertility to date is embryo cryopreservation, which may not be appropriate for some patients due to age, delay in treatment, cancer type and stage, as well as availability of an acceptable sperm donor. Alternative methods including oocyte cryopreservation and ovarian tissue banking may also preserve fertility while providing additional flexibility to patients. In vitro ovarian follicle maturation following tissue banking is one potential approach that would not require a delay in cancer therapy for ovarian stimulation, would not require an immediate sperm donor, and does not carry the risk of reintroducing malignant cells following tissue transplantation. In vitro follicle culture systems have resulted in successful live births in the mouse. However, many challenges must be addressed in translating the system to the human. This review summarizes current approaches to fertility preservation and discusses recent developments and future challenges in developing a human in vitro follicle culture system.

Clinical aspects of fertility preservation in female patients

There are several methods of fertility preservation available for female patients facing infertility following gonadotoxic treatment of cancer or systemic disease. Embryos, oocytes or ovarian tissue can be cryopreserved and stored until the time when the patient is cured of her main disease and is expecting parenthood. The individual's choice depends on the nature and stage of the main disease, expected treatment, their condition, and age and existence of the partner. It is important to inform all such women about the options, and together with them, choose the most appropriate ones. It is often possible to save ovarian tissue even though the first chemotherapy courses have been undergone, but many more follicles can be stored before cancer treatment.

In vitro grown human ovarian follicles from cancer patients support oocyte growth

BACKGROUND

Young female adult and adolescent cancer patients facing life-preserving but fertility-threatening chemo- or radiation-therapy are increasingly seeking options to protect their reproductive potential. Ovarian tissue cryopreservation with transplantation is a promising technique to safeguard fertility in cancer patients. However, this method may risk re-introduction of the original cancer to the survivor of the disease. Thus, developing a method for in vitro growth of immature follicles may provide a method for fertility restoration in the future.

METHODS

Human secondary follicles were isolated from ovarian tissues obtained from cancer patients and grown in vitro within a bio-engineered culture system for 30 days.

RESULTS

Human ovarian follicles became steroidogenically active, and developed from the early secondary to antral stage in vitro. The follicles contained healthy, growing oocytes that were connected by transzonal projections between the somatic cells and oocyte.

CONCLUSIONS

Our data support the notion that human follicle development can be achieved in vitro in a bio-engineered culture system. More studies are required to investigate whether the fully sized oocytes obtained from in vitro grown follicle are competent to resume meiosis and be fertilized.

Encapsulated three-dimensional culture supports development of nonhuman primate secondary follicles

In vitro ovarian follicle cultures may provide fertility-preserving options to women facing premature infertility due to cancer therapies. An encapsulated three-dimensional (3-D) culture system utilizing biomaterials to maintain cell-cell communication and support follicle development to produce a mature oocyte has been developed for the mouse. We tested whether this encapsulated 3-D system would also support development of nonhuman primate preantral follicles, for which in vitro growth has not been reported. Three questions were investigated: Does the cycle stage at which the follicles are isolated affect follicle development? Does the rigidity of the hydrogel influence follicle survival and growth? Do follicles require luteinizing hormone (LH), in addition to follicle-stimulating hormone (FSH), for steroidogenesis? Secondary follicles were isolated from adult rhesus monkeys, encapsulated within alginate hydrogels, and cultured individually for </=30 days. Follicles isolated from the follicular phase of the menstrual cycle had a higher survival rate (P < 0.05) than those isolated from the luteal phase; however, this difference may also be attributed to differing sizes of follicles isolated during the different stages. Follicles survived and grew in two hydrogel conditions (0.5% and 0.25% alginate). Follicle diameters increased to a greater extent (P < 0.05) in the presence of FSH alone than in FSH plus LH. Regardless of gonadotropin treatment, follicles produced estradiol, androstenedione, and progesterone by 14-30 days in vitro. Thus, an alginate hydrogel maintains the 3-D structure of individual secondary macaque follicles, permits follicle growth, and supports steroidogenesis for </=30 days in vitro. This study documents the first use of the alginate system to maintain primate tissue architecture, and findings suggest that encapsulated 3-D culture will be successful in supporting the in vitro development of human follicles.

The in vitro growth and maturation of follicles

The development of technologies to grow oocytes from the most abundant primordial follicles to maturity in vitro holds many attractions for clinical practice, animal production technology and research. The production of fertile oocytes and live offspring has been achieved in mice following the long-term culture of oocytes in primordial follicles from both fresh and cryopreserved ovarian tissue. In contrast, in non-rodent species advances in follicle culture are centred on the growth of isolated preantral follicles. As a functional unit, mammalian preantral follicles are well-suited to culture but primordial and primary follicles do not grow well after isolation from the ovarian stroma. The current challenges for follicle culture are numerous and include: optimisation of culture media and the tailoring of culture environments to match the physiological needs of the cell in vivo; the maintenance of cell-cell communication and signalling during culture; and the evaluation of the epigenetic status, genetic health and fertility of in vitro derived mature oocytes. In large animals and humans, the complete in vitro growth and maturation of oocytes is only likely to be achieved following the development of a multistage strategy that closely mimics the ovary in vivo. In this approach, primordial follicle growth will be initiated in situ by the culture of ovarian cortex. Isolated preantral follicles will then be grown to antral stages before steroidogenic function is induced in the somatic cells. Finally, cytoplasmic and nuclear maturation will be induced in the in vitro derived oocytes with the production of fertile metaphase II gametes.

Growth differentiation factor-9 and anti-Müllerian hormone expression in cultured human follicles from frozen-thawed ovarian tissue

In-vitro growth of frozen-thawed human follicles is perceived as a potential option for restoring women's fertility. The aims of this study were: (i) to test the usefulness of a defined serum-free medium for growth of frozen-thawed human follicles; and (ii) to evaluate the expression of growth differentiation factor-9 (GDF-9) and anti-Müllerian hormone (AMH) in cultured follicles. Frozen-thawed ovarian cortical pieces from 7-, 12-, 25- and 27-year-old women were cultured for 0, 7, 14, 21 and 28 days. Follicle developmental quality was evaluated and expression of proliferating cell nuclear antigen (PCNA) (day 21), GDF-9 (days 14 and 28) and AMH (day 21) was assessed by immunohistochemistry. Primary follicles and enclosed oocytes underwent significant growth at the end of culture (P < 0.05). Cultured follicles from all patients studied reached the early secondary stage and a few follicles from two patients developed up to the secondary stage. The rate of atresia was variable throughout the culture periods. PCNA was expressed in the granulosa cells at all the different follicular stages. AMH and GDF-9 immunostaining were found respectively in the granulosa cells and oocytes after several weeks of culture. The transition from resting to growing follicles leading to the development of secondary follicles showed the normal expression patterns of GDF-9 and AMH.

Cryopreservation/transplantation of ovarian tissue and in vitro maturation of follicles and oocytes: challenges for fertility preservation

Cryopreservation of ovarian tissue and in vitro follicle maturation are two emerging techniques for fertility preservation, especially in cancer patients. These treatment regimes are opening up more options and allow for more suitable choices to preserve fertility according to the patient's specific circumstances. If these technologies are to become widely accepted, they need to be safe, easy to perform and must obtain favorable results. The generation of healthy eggs with the normal genetic complement and the ability to develop into viable and healthy embryos requires tight regulation of oocyte development and maturation. Novel freezing techniques such as vitrification, along with whole ovary cryopreservation and three-dimensional follicle cultures, have shown favorable outcomes. The scope of this article is to take a comprehensively look at the challenges still faced in order for these novel technologies to be routinely employed with the aim of successful fertility preservation.

Hormonal manipulations in the luteal phase to coordinate subsequent antral follicle growth during ovarian stimulation

During the early follicular phase in the menstrual cycle, antral follicle sizes are often markedly heterogeneous. These follicular size discrepancies may, at least in part, result from the early exposure of FSH-sensitive follicles to gradient FSH concentrations during the preceding luteal phase. In addition, they potentially affect the results of ovarian stimulation. Indeed, pre-existing follicle size discrepancies may encumber coordinated follicular growth during ovarian stimulation, thereby reducing the number of follicles that reach maturation at once. To investigate this issue, three clinical studies were conducted to test the hypothesis that luteal FSH suppression could coordinate follicular growth. First, luteal FSH concentrations were artificially lowered by administering physiological oestradiol doses and measured follicular characteristics on the subsequent day 3. Second, it was verified whether luteal oestradiol administration could promote the coordination of follicular growth during ovarian stimulation and improve its results. Third, the effects of premenstrual gonadotrophin-releasing hormone (GnRH) antagonist administration on follicular characteristics were assessed during the early follicular phase. The results showed that luteal FSH suppression by either oestradiol or GnRH antagonist administration reduces the size and improves the homogeneity of early antral follicles during the early follicular phase, an effect that persists during ovarian stimulation. Coordination of follicular development may optimize ovarian response to short GnRH agonist and antagonist protocols, and constitutes an attractive approach to improving their outcome.

Human ovarian tissue from cortex surrounding benign cysts: a model to study ovarian tissue cryopreservation

BACKGROUND

The scarcity of human ovarian tissue is a major problem in developing research on ovarian cryopreservation. We were interested in ovarian cortex surrounding benign ovarian cysts harvested during their requisite operations.

METHODS

Ovarian tissue was collected from 25 women (mean age = 27.7 +/- 1.0 SEM) and frozen in serum-free cryoprotective medium. Histological and viability analysis were performed on fresh and frozen-thawed slices of tissue.

RESULTS

Dermoid (n = 7), endometriosis (n = 13) and serous (n = 5) cysts were observed. Follicular densities (expressed per mm3) in ovarian cortex surrounding dermoid cysts were higher than in endometriosis and serous cysts for both histological (median of follicular densities: 13.04, 0.31 and 0.89 respectively) and viability analysis (2.93, 0.05 and 0.71 respectively). Freezing-thawing did not result in gross abnormality of follicle population either in number or morphology (80% of follicles preserved a normal pattern). However, a slight decrease of the density of living follicles (expressed per mm2) was reported.

CONCLUSIONS

Ovarian cortex surrounding ovarian cysts, especially dermoid cysts, could be considered a source of ovarian tissue for future research. In our study, the cryopreservation procedure resulted in high follicular survival assessed by both histological and viability analysis. Nevertheless, further studies of in vivo and in vitro follicular maturation are needed to strengthen this model.

Methods for cryopreservation of human ovarian tissue

Human ovarian tissue can be successfully cryopreserved, with good survival and function after thawing. Experimental animal studies regarding ovarian tissue cryopreservation resulting in live-born offspring preceded the present freezing systems in humans. On the basis of current knowledge, the standard method for human ovarian cryopreservation is slow programmed freezing, using human serum albumin-containing medium, and propanediol, dimethylsulphoxide (DMSO) or ethylene glycol as a cryoprotectant, combined with sucrose. Vitrification is still at the experimental stage. Whole organ cryopreservation is an interesting experimental option. Transplantation of the frozen-thawed tissue is a feasible method to utilize the tissue in infertility treatment. Ovarian function has been restored in humans. Because one healthy child has already been born from cryopreserved tissue, tissue cryopreservation should perhaps be offered to all young girls and women who can be predicted to undergo premature ovarian failure due to cancer treatment or genetic causes. Maturation of follicles in vitro from frozen-thawed tissue is another option that is still under development.

Diagnostic assessment of the developmental potential of human cryopreserved ovarian tissue from multiple patients using xenografting

BACKGROUND

Although ovarian tissue cryopreservation for women at risk of losing ovarian function is offered by many clinics, there is a lack of evidence relating to the developmental potential of the stored tissue and, therefore, its clinical potential. This study was designed to use xenografting of cryopreserved tissue from multiple patients to assess the reproducibility of preservating developmental potential, the variation in developing follicle profile and the relationship between pre-freeze histology and post-thaw development.

METHODS

Using previously published methods, cryopreserved ovarian cortex from nine patients was thawed and grafted under the kidney capsules of immunodeficient mice. Development of follicles was assessed after 26 weeks and compared to histology prior to freezing.

RESULTS

Multiple growing follicles including antral stages were observed in multiple grafts of tissue from all patients. Metaphase II oocytes (n=9) were observed in follicles in grafts from five patients. There was no relationship between pre-freeze histology and developing follicle profile in xenografts.

CONCLUSIONS

The propanediol freezing method used in this study is capable of reproducibly preserving the developmental potential of human ovarian follicles. The developing follicle profile after cryopreservation cannot be accurately predicted from pre-freeze histology. Xenografting provides a powerful tool for assessing the potential of human cryopreserved ovarian tissue.

Human ovarian tissue cultures: extracellular matrix composition, coating density and tissue dimensions

Human ovarian tissue can be successfully cryopreserved for fertility preservation. Optimal use of this approach requires the development of reliable restoration methods, including in-vitro culture of follicles. A culture system has been established, but improvement of the basic handling and techniques is necessary. Ovarian biopsies were collected from 33 women, cut into small pieces and cultured for 7-14 days on an extracellular matrix. Three separate studies investigated tissue dimensions (slices and cubes), coating density of extracellular matrix (diluted, thin and thick), and different extracellular matrix compositions (regular Matrigel, growth factor reduced Matrigel and laminin). Initial recruitment of primordial follicles and reduction in follicle viability was observed in all cultures compared with uncultured tissue. After 7 days of culture, more viable follicles were present in the cubed tissue, which also showed significant activation of growth, observed in tissue slices only after 14 days of culture. A diluted coating of Matrigel supported a greater proportion of viable follicles in 7-day cultures, whereas composition of the extracellular matrix had no effect. Human ovarian follicles can grow and develop in vitro within cortical tissue, and may benefit from culture as cubes on diluted Matrigel. This technique may provide a solution to the successful recovery and growth of follicles from frozen human ovarian tissue even though it will take time and much more optimization before it can be used in clinical practice.