Cryopreservation of Human Oocytes and Ovarian Tissue

Morphological and Chemical Investigation of Ovarian Structures in a Bovine Model by Contrast-Enhanced X-ray Imaging and Microscopy

An improved understanding of an ovary's structures is highly desirable to support advances in folliculogenesis knowledge and reproductive medicine, with particular attention to fertility preservation options for prepubertal girls with malignant tumors. Although currently the golden standard for structural analysis is provided by combining histological sections, staining, and visible 2D microscopic inspection, synchrotron radiation phase-contrast microtomography is becoming a new challenge for three-dimensional studies at micrometric resolution. To this aim, the proper use of contrast agents can improve the visualization of internal structures in ovary tissues, which normally present a low radiopacity. In this study, we report a comparison of four staining protocols, based on iodine or tungsten containing agents, applied to bovine ovarian tissues fixed in Bouin's solution. The microtomography (microCT) analyses at two synchrotron facilities under different set-ups were performed at different energies in order to maximize the image contrast. While tungsten-based agents allow large structures to be well identified, Iodine ones better highlight smaller features, especially when acquired above the K-edge energy of the specific metal. Further scans performed at lower energy where the setup was optimized for overall quality and sensitivity from phase-contrast still provided highly resolved visualization of follicular and intrafollicular structures at different maturation stages, independent of the staining protocol. The analyses were complemented by X-ray Fluorescence mapping on 2D sections, showing that the tungsten-based agent has a higher penetration in this type of tissues.

Ultrastructural Evaluation of the Human Oocyte at the Germinal Vesicle Stage during the Application of Assisted Reproductive Technologies

After its discovery in 1825 by the physiologist J.E. Purkinje, the human germinal vesicle (GV) attracted the interest of scientists. Discarded after laparotomy or laparoscopic ovum pick up from the pool of retrieved mature oocytes, the leftover GV was mainly used for research purposes. After the discovery of Assisted Reproductive Technologies (ARTs) such as in vitro maturation (IVM), in vitro fertilization and embryo transfer (IVF-ET) and intracytoplasmic sperm injection (ICSI), its developing potential was explored, and recognized as an important source of germ cells, especially in the case of scarce availability of mature oocytes for pathological/clinical conditions or in the case of previous recurrent implantation failure. We here review the ultrastructural data available on GV-stage human oocytes and their application to ARTs.

Prognosis in fertilisation rate and outcome in IVF cycles in patients with and without endometriosis: a population-based comparative cohort study with controls

Background:

Subfertility occurs in 30-40% of endometriosis patients. Regarding the fertilisation rate with in vitro fertilisation (IVF) and endometriosis, conflicting data has been published. This study aimed to compare endometriosis patients to non-endometriosis cycles assessing fertilisation rates in IVF.

Methods:

A population-based cohort study was conducted at the Leiden University Medical Center. IVF cycles of endometriosis patients and controls (unexplained infertility and tubal pathology) were analysed. The main outcome measurement was fertilisation rate.

Results:

503 IVF cycles in total, 191 in the endometriosis group and 312 in the control. The mean fertilisation rate after IVF did not differ between both groups, 64.1%±25.5 versus 63.9%±24.8 (p=0.95) respectively, independent of age and r-ASRM classification. The median number of retrieved oocytes was lower in the endometriosis group (7.0 versus 8.0 respectively, p=0.19) and showed a significant difference when corrected for age (p=0.02). When divided into age groups, the statistical effect was only seen in the group of ≤ 35 years (p=0.04). In the age group ≤35, the endometriosis group also showed significantly more surgery on the internal reproductive organs compared to the control group (p<0.001). All other outcomes did not show significant differences.

Conclusion:

Similar fertilisation rates were found in endometriosis IVF cycles compared to controls. The oocyte retrieval was lower in the endometriosis group, however this effect was only significant in the age group ≤ 35 years. All other secondary outcomes did not show significant differences. In general, endometriosis patients with an IVF indication can be counselled positively regarding the chances of becoming pregnant, and do not need a different IVF approach.

Effects of paclitaxel and cisplatin on in vitro ovarian follicle development

INTRODUCTION

Despite its importance in pre-chemotherapy counselling, specific reproductive toxicological information about cisplatin and paclitaxel is very rare. This study aimed to investigate the concentrations at which cisplatin and paclitaxel, alone or combined, affect the in vitro development of ovarian follicles. Their differential effects on the oocytes and surrounding granulosa cells was also evaluated.

MATERIAL AND METHODS

Ovarian follicles were cultured in vitro using gonadotropins and treated with 10^-8-10^-10 M of cisplatin, paclitaxel, or both. At day 13, granulosa cells and oocytes were retrieved and used for imaging and functional analyses.

RESULTS

Follicular survival and growth was significantly suppressed in all treatment groups at 10^-9 M or higher concentrations, and additive effects were observed in the combination group (p < 0.01). Oocyte-specific genes such as growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15) were more suppressed in the paclitaxel group than in the cisplatin group. Granulosa cell-specific gene suppression and its electron microscopic alteration were more prominent in the cisplatin group than in the paclitaxel group. X-linked inhibitor of apoptosis protein (XIAP) expression of granulosa cells was also further down-regulated in the cisplatin group.

CONCLUSIONS

These data provide an insight into the critical concentrations regarding in vitro follicular development and the differential effects of chemotherapeutic effects on oocytes and granulosa cells. Further studies are necessary to develop more efficient pre-chemotherapeutic fertility-sparing medical treatment that can evade oocyte-specific damage.

Production of blastocysts following in vitro maturation and fertilization of dromedary camel oocytes vitrified at the germinal vesicle stage

Cryopreservation of oocytes would serve as an alternative to overcome the limited availability of dromedary camel oocytes and facilitate improvements in IVP techniques in this species. Our goal was to develop a protocol for the vitrification of camel oocytes at the germinal vesicle (GV) stage using different cryoprotectant combinations: 20% EG and 20% DMSO (VS1), 25% EG plus 25% DMSO (VS2) or 25% EG and 25% glycerol (VS3) and various cryo-carriers; straws or open pulled-straw (OPS) or solid surface vitrification (SSV); and Cryotop. Viable oocytes were cultured in vitro for 30 h. Matured oocytes were fertilized with epididymal spermatozoa and then cultured in vitro in modified KSOMaa medium for 7 days. Survival and nuclear maturation rates were significantly lower (P ≤ 0.05) in oocytes exposed to VS3 (44.8% and 34.0%, respectively) than those exposed to VS1 (68.2% and 48.0%, respectively) and VS2 (79.3% and 56.9%, respectively). Although recovery rates were significantly lower (P ≤ 0.05) in SSV and Cryotop vitrified oocytes (66.9% to 71.1%) than those vitrified by straws with VS1 or VS2 solutions (86.3% to 91.0%), survival rates were higher in the SSV and Cryotop groups (90.7% to 94.8%) than in the straw and OPS groups (68.2% to 86.5%). Among vitrified groups, maturation and fertilization rates were the highest in the Cryotop-VS2 group (51.8% and 39.2%, respectively). These values were comparable to those seen in the controls (59.2% and 44.6%, respectively). Cleavage (22.5% to 27.9%), morula (13.2% to 14.5%), and blastocyst (6.4% to 8.5%) rates were significantly higher (P ≤ 0.05) in SSV and Cryotop groups than in straws. No significant differences were observed in these parameters between the Cryotop and control groups. We report for the first time that dromedary oocytes vitrified at the GV-stage have the ability to be matured, fertilized and subsequently develop in vitro to produce blastocysts at frequencies comparable to those obtained using fresh oocytes.

Influence of gonadotropins on ovarian follicle growth and developmentin vivoandin vitro

Gonadotropins are the key regulators of ovarian follicles development. They are applied in therapeutic practice in assisted reproductive technology clinics. In the present review we discuss the basic gonadotropic hormones – recombinant human follicle-stimulating hormone, its derivatives, luteinizing hormone and gonadotropin serum of pregnant mares, their origin, and application in ovarian follicle systems inin vitroculture systems.

Microfluidic Encapsulation of Ovarian Follicles for 3D Culture

The ovarian follicle that contains one single oocyte is the fundamental functional tissue unit of mammalian ovary. Therefore, isolation and in vitro culture of ovarian follicles to obtain fertilizable oocytes are regarded as a promising strategy for women to combat infertility. In this communication, we performed a brief survey of studies on microfluidic encapsulation of ovarian follicles in core-shell hydrogel microcapsules for biomimetic 3D culture. These studies highlighted that recapitulation of the mechanical heterogeneity of the extracellular matrix in ovary is crucial for in vitro culture to develop early pre-antral follicles to the antral stage, and for the release of cumulus-oocyte complex (COC) from antral follicles in vitro. The hydrogel encapsulation-based biomimetic culture system and the microfluidic technology may be invaluable to facilitate follicle culture as a viable option for restoring women's fertility in the clinic.

Vitrification by Cryotop and the Maturation, Fertilization, and Developmental Rates of Mouse Oocytes

Background:

Oocyte cryopreservation is an important part of modern fertility treatment. The effect of vitrification on the fertilization and developmental rates of embryo is still a matter of debate.

Objectives:

This study aimed to investigate the effect of vitrification on the success of mouse oocyte maturation, fertilization, and preimplantation development in vitro.

Materials and Methods:

In this experimental study, a total of 200 germinal vesicle (GV) and 200 metaphase II (MII) oocytes were obtained from ovaries and fallopian tubes of NMRI mice, respectively and divided into two control and experimental (vitrified) groups. Oocytes in the experimental group were vitrified by Cryotop using vitrification medium (Origio, Denmark) and kept in liquid nitrogen for one month. Then, they were cultured in maturation medium for 24 hours. In vitro maturated metaphase 2 (IVM-MII) and ovulated metaphase 2 (OV-MII) oocytes were inseminated and the fertilized embryos assessed until the hatching blastocyst stage. Outcomes were assessed for statistical significance by Chi-square test using SPSS software.

Results:

Vitrification caused a significant reduction in the maturation rate of oocytes. Of those that matured, the fertilization rate of vitrified IVM-MII (44.1%) and OV-MII oocytes (50%) was not significantly different from each other but both were significantly lower than the control group (P < 0.05). There was no significant difference in developmental rates of both vitrified groups and the control group.

Conclusions:

The present study showed that vitrification using Cryotop and freezing medium can damage oocytes by reducing the maturation and fertilization rates in both developmental stages.

Safety aspects and side-effects of ExEm-gel and foam for uterine cavity distension and tubal patency testing

A state-of-the-art overview of the safety and side-effects of ExEm-gel for uterine cavity distension and ExEm-foam for tubal patency testing is presented. A literature search was carried out using PubMed, textbooks, pharmaceutical databases and reports of toxicity tests. Information on clinical use in humans and experiments in animal models was collected and grouped according to the following components: glycerol, hydroxyethyl cellulose and purified water; subjects included toxicity test, influence on sperm cells, oocytes, blastocyst development, uterine cavity distension, tubal patency testing, pain and obstetric applications. No unknown side-effects of gel or foam, or unexpected concerns about safety, were reported. More information than expected was available on the absence of effects of the components on various human tissues. Although it is difficult to prove that the search is complete, and it is possible that side-effects remain unreported, the combination of glycerol, hydroxyethyl cellulose and purified water is considered to be safe for intrauterine application and tubal patency testing, indicating an optimal risk-benefit ratio in clinical use. The safest strategy, however, is to restrict clinical examinations with gel and foam to the pre-ovulatory phase of the menstrual cycle.

Replacement of sodium with choline in slow-cooling media improves human ovarian tissue cryopreservation

Ovarian tissue cryopreservation is a promising technique for fertility preservation in young female cancer patients and efforts have been made to improve its effectiveness. During cooling and thawing, sodium ions significantly contribute to the 'solute effect' that plays a major role in disrupting cell membranes. Choline ions, which do not cross the cell membrane, should not contribute to the intracellular solute load. The present study assessed the effects of sodium substitution with choline in slow-cooling freezing media on human ovarian cortical strip cryopreservation. A total of 629 follicles (fresh control n=266; cryopreserved n=363), collected from ovarian biopsies of 11 women (22-40years) during laparoscopic surgery, were studied by light microscopy, immunohistochemistry and transmission electron microscopy to evaluate their morphology, apoptosis and ultrastructure. The results demonstrate that choline substitution leads to: (i) an improved preservation of oocytes and follicular cells; (ii) the recovery of a higher percentage of grade-1 follicles negative for p53, p21 and Apaf-1 apoptotic markers; (iii) a reduced mitochondrial damage as observed at an ultrastructural level; and (iv) a better preservation of ovarian tissue stroma. In conclusion, the use of choline-based media may represent a valuable tool to improve human ovarian tissue cryopreservation. Ovarian tissue cryopreservation is a promising fertility preservation approach for cancer patients before undergoing treatments that irreversibly reduce the ovarian reserve. Autotransplantation of ovarian cortical strips has resulted in viable offspring in animal models and human. Worldwide, 20 live births have been reported thus far following autotransplantation of frozen-thawed ovarian tissue. However, currently the success rate of this technology is far from being satisfactory. This could be due to inappropriate cryopreservation procedures that might impair the physiology of ovarian follicles. Sodium ions contained in freezing media significantly contribute to the 'solute effect' that plays a major role in disrupting cell membranes. Choline ions, which do not cross the cell membrane, would not be expected to contribute to the intracellular solute load. In the present study we assessed the effects of sodium substitution with choline in slow-cooling freezing media on human ovarian cortical strip cryopreservation. A total of 629 follicles, collected from ovarian biopsies of 11 women (aged 22-40years) during laparoscopic surgery, have been studied by light microscopy, immunohistochemistry and transmission electron microscopy to evaluate their morphology, apoptosis and ultrastructure. Results demonstrated that choline substitution allowed: (i) a better preservation of oocytes and follicular cells; (ii) the recovery of an higher percentage of healthy follicles negative for apoptotic markers; (iii) a lower mitochondria ultrastructural damage; and (iv) a better preservation of ovarian tissue stroma. In conclusion, the use of choline-based media could represent a valuable tool to cryopreserve human ovarian tissue for fertility preservation.

Effects of vitrification solutions and equilibration times on the morphology of cynomolgus ovarian tissues

This study assessed the effects of vitrification solutions and equilibration times on morphology of cynomolgus ovarian tissues. Ovarian cortical sections (0.1-0.2 cm thickness) of seven cynomolgus monkeys were randomly allocated to either a control group or one of six vitrification groups. Ovarian tissue sections were vitrified ultra-rapidly by placing them directly into liquid nitrogen using two different vitrification solutions (VSEGP: 5.64 mol/l ethylene glycol+5% (w/v) polyvinylpyrrolidone+0.5 mol/l sucrose; and VSED: 3.22 mol/l ethylene glycol+2.56 mol/l dimethylsulphoxide+0.5 mol/l sucrose) after three different exposure times (5-20 min). After warming, follicle morphology was analysed using light and transmission electron microscopy. The proportion of morphologically normal follicles vitrified using VSED after a 5-min exposure was lower (P<0.05) than those vitrified by other conditions. The proportion of normally structured mitochondria in oocytes of preantral follicles vitrified after a 5-min exposure to VSED (56%) was lower (P<0.01) than those vitrified by other conditions (78-88%). Following tissue vitrification with VSED, the surface ratio of lysosome was increased compared with non-vitrified oocytes (1.64% versus 1.11%; P<0.05). These results indicate that VSEGP can support the morphology of vitrified preantral follicles and oocytes.

Biotransport phenomena in freezing mammalian oocytes

Water transport across the cell plasma membrane and intracellular ice formation (IIF)-the two biophysical events that may cause cell injury during cryopreservation-were studied by cryomicroscopy and modeling using mammalian (Peromyscus) oocytes. Unusually high activation energy for water transport across the cell plasma membrane was identified indicating that the water transport process is unusually sensitive to temperature (and cooling rate). Although literally all studies on IIF were conducted using protocols with ice-seeding (seeding extracellular ice usually at ≥-7 °C), it is not used for cell cryopreservation by vitrification that is becoming increasingly popular today. In this article, we show that ice-seeding has a significant impact on IIF. With ice-seeding and cooling at 60 °C/min, IIF was observed to occur over a wide range from approximately -8 to -48 °C with a clear change of the ice nucleation mechanism (from surface- to volume-catalyzed nucleation) at approximately -43 °C. On the contrary, without ice-seeding, IIF occurred over a much narrower range from approximately -19 to -27 °C without a noticeable change of the nucleation mechanism. Moreover, the kinetics of IIF without ice-seeding was found to be strongly temperature (and cooling rate) dependent. These findings indicate the importance of quantifying the IIF kinetics in the absence of ice-seeding during cooling for development of optimal vitrification protocols of cell cryopreservation.

Membrane permeability characteristics of bovine oocytes and development of a step-wise cryoprotectant adding and diluting protocol

Membrane permeability is very helpful for the optimization of effective cryopreservation protocols. In this study, experiments were performed to determine these characteristics for immature (germinal vesicle (GV)) and in vitro matured (metaphase II (MII)) bovine oocytes within 4-37 degrees C, and a new step-wise adding and diluting protocol for ethylene glycol (EG) was developed and verified. Osmotically inactive volumes (V(b)) of GV and MII oocytes were calculated to be 16.1% and 26.1%. The membrane permeability of the oocytes to water (L(p)) in the presence of EG were between 0.08-0.18 and 0.14-0.28 microm/min/atm, and the membrane permeability of the oocytes to solutes (Ps) were between 0.0011-0.0038 and 0.0029-0.0061 cm/min for GV and MII oocytes, respectively. The activation energies (E(a)) for L(p) and P(s) in the presence of EG were 3.68 and 6.84 kcal/mol for GV oocyte, while 3.62 and 0.83-9.08 kcal/mol for MII oocyte. The data indicated that L(p) and P(s) varied significantly between developmental stages and among temperatures evaluated. Based on these results, different protocols for EG adding and diluting from oocytes were developed and tested. The assessment of cleavage rate and embryonic development in vitro confirmed that the designed 4-step adding 2-step diluting protocol indicated a better outcome. The present study is helpful for better understanding of cryobiological properties and the design of cryopreservation protocols for bovine oocytes.

Protective effects of the cumulus-corona radiata complex during vitrification of horse oocytes

Vitrifying oocytes is a potentially valuable means of preserving the female germ line, but significantly compromises oocyte developmental competence. This study examined the hypothesis that the cumulus complex protects the oocyte during vitrification. Vitrified-warmed immature cumulus oocyte complexes (COCs) were labelled with a plasma membrane impermeant DNA marker (ethidium homodimer-1) to examine the percentage and location of dead cumulus cells, and to investigate the effect of the proportion of dead cells (+1,+2 or +3) on the success of in vitro maturation (IVM). Further, oocytes were labelled for connexin-43 or injected with Lucifer yellow dye to determine whether the integrity of the gap junctions between an oocyte and its cumulus was compromised by vitrification. Finally, the effect of denuding immature and mature oocytes on their ability to withstand vitrification was examined. Cryopreserving immature COCs increased the number of dead cumulus cells (13 vs 2.6% for controls; P<0.05). However, an increased proportion of dead cumulus cells did not affect post-warming maturation rates (∼30% MII) presumably because dead cells were located at the periphery of the cumulus mass and cumulus-oocyte gap junction communication was not disrupted. Moreover, cumulus removal prior to IVM or vitrification indicated that while the cumulus does protect immature oocytes during vitrification it does so by mechanisms other than support during maturation. Cumulus presence was also found to protect mature equine oocytes against vitrification-induced damage since cumulus-enclosed MII oocytes preserved their meiotic spindle quality better during vitrification than denuded oocytes (38.1 vs 3.1% normal spindles; P<0.05).

Intracytoplasmic sperm injection in livestock species: an update

Intracytoplasmic sperm injection (ICSI) is a powerful technique in the field of assisted reproduction (ART) and provides exciting opportunities for studying the basic mechanisms of fertilization and early embryo development. Nevertheless, its application in agriculture and conservation biology has been greatly hampered by the low success rate reported for this method in respect of economically important species. Specifically, the rates of blastocyst formation and live newborn are greatly reduced when zygotes are generated by ICSI. Except for humans, ICSI remains a low efficiency technology in comparison with alternatives such as in vitro fertilization (IVF) and its application is less widespread. In this paper, we discuss the present status, applications and factors affecting ICSI in pigs and other species.

Morphology and function of cryopreserved whole ovine ovaries after heterotopic autotransplantation

BACKGROUND

The objective of this study was to perform complex characterization of cryopreserved and then autotransplanted ovaries including determination of the ability to respond to in vivo follicle stimulating hormone (FSH)-treatment, fertilizability of retrieved oocytes, and morphology, vascularization, cellular proliferation and apoptosis in sheep.

METHODS

Mature crossbred ewes were divided into two groups; an intact (control) group (n = 4), and autotransplanted group (n = 4) in which oophorectomy was performed laparoscopically and ovaries with intact vascular pedicles frozen, thawed and transplanted back into the same animal at a different site. Approximately five months after autotransplantation, estrus was synchronized, ewes were treated with FSH, and ovaries were collected. For all ovaries, number of visible follicles was determined, and collected cumulus oocyte complexes (COC) were matured and fertilized in vitro. Remaining ovarian tissues were fixed for evaluation of morphology, expression of factor VIII (marker of endothelial cells), vascular endothelial growth factor (VEGF; expressed by pericytes and smooth muscle cells), and smooth muscle cell actin (SMCA; marker of pericytes and smooth muscle cells), and cellular proliferation and apoptosis. Two fully functional ovaries were collected from each control ewe (total 8 ovaries).

RESULTS

Out of eight autotransplanted ovaries, a total of two ovaries with developing follicles were found. Control ewes had 10.6 +/- 2.7 follicles/ovary, oocytes were in vitro fertilized and developed to the blastocyst stage. One autotransplanted ewe had 4 visible follicles from which 3 COC were collected, but none of them was fertilized. The morphology of autotransplanted and control ovaries was similar. In control and autotransplanted ovaries, primordial, primary, secondary, antral and preovulatory follicles were found along with fully functional vascularization which was manifested by expression of factor VIII, VEGF and SMCA. Proliferating cells were detected in follicles, and the rate of apoptosis was minimal in ovaries of control and autotransplanted ovaries.

CONCLUSION

These data demonstrate successful autotransplantation of a portion of frozen/thawed ovaries manifested by restoration of selected ovarian function including in vitro maturation of collected oocytes, presence of follicles from several stages of folliculogenesis and blood vessels expressing specific markers of vascularization, and proliferation and apoptosis of ovarian cells. Thus, heterotopic autotransplantation of a whole frozen/thawed ovary allows for development of preovulatory follicles, oocyte growth, and for restoration of vascularization and cellular function. However, additional improvements are required to enhance the efficiency of autotransplantation of frozen/thawed ovaries to produce more oocytes.

Cryopreserved human adipogenic-differentiated pre-adipocytes: a potential new source for adipose tissue regeneration

BACKGROUND

Previously, we have shown that in vitro adipogenic differentiation of pre-adipocytes before implantation can enhance in vivo adipose tissue formation. For large-scale adipose tissue engineering or repeat procedures, cryopreservation of fat grafts has been commonly used in recent years. However, the feasibility of cryopreservation of adipogenic differentiated pre-adipocytes has not been investigated.

METHODS

To examine the impact of cryopreservation on the adipogenic functions of adipogenic-differentiated pre-adipocytes, freeze-thawed adipocytes were compared with fresh differentiated adipocytes in vitro and in vivo. Adipogenic function was assessed by Oil red O staining, ELISA analysis of leptin secretion and RT-PCR of adipogenic-related genes. After transplantation, adipose tissue formation was assessed by histomorphologic and volumetric analysis.

RESULTS

Freeze-thawed adipocytes constantly showed typical adipogenic functions in terms of lipid content, leptin secretion and adipogenic gene expression, as well as good viability. Importantly, implants derived from freeze-thawed adipocytes were successfully developed to adipose tissue and newly formed adipose tissues were similar to those developed from fresh differentiated adipocytes, based on histomorphologic and volumetric analysis. In addition, CD34-positive endothelial cells were detected in implants. These results demonstrate that the specific characters of adipogenic-differentiated pre-adipocytes are successfully conserved after cryopreservation without any significant alteration.

DISCUSSION

Cryopreservation of adipogenic-differentiated pre-adipocytes is a feasible method and extends their clinical use in adipose tissue-engineering applications and transplantation.

Ovarian and oocyte cryopreservation

PURPOSE OF REVIEW

The present article is an update on progress in the two available techniques of oocyte and ovarian cryopreservation: slow cooling/rapid thawing and vitrification. A new line of research has opened in recent years: freezing the whole ovary with its vascular pedicle, so as to enable vascular grafts limiting ischemia-related follicle reserve loss.

RECENT FINDINGS

The technique of mature oocyte vitrification has advanced significantly, with improved oocyte physiology, increased safety, and higher clinical pregnancy rates. The number of studies on whole ovary freezing has grown, and there has been a large-mammal (sheep) live birth by orthotopic graft with vascular anastomosis of a cryopreserved ovary.

SUMMARY

Ovarian and oocyte cryopreservation is essential to conserving the fertility of young women. Results of mature oocyte freezing techniques have improved significantly over the past few years, but remain poorer than those with embryo freezing. Mature oocyte vitrification is progressing well, but requires safety validation in view of the high cryoprotectant concentrations used. Ovarian cortex fragment freezing is widely used in patients, with two live births after orthotopic graft, worldwide. The problem of rapid graft exhaustion has led to a focus on whole ovary cryopreservation which has resulted in one live birth in a ewe.

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.

Engineering the follicle microenvironment

In vitro ovarian follicle culture provides a tool to investigate folliculogenesis, and may one day provide women with fertility-preservation options. The application of tissue engineering principles to ovarian follicle maturation may enable the creation of controllable microenvironments that will coordinate the growth of the multiple cellular compartments within the follicle. Three-dimensional culture systems can preserve follicle architecture, thereby maintaining critical cell-cell and cell-matrix signaling lost in traditional two-dimensional attached follicle culture systems. Maintaining the follicular structure while manipulating the biochemical and mechanical environment will enable the development of controllable systems to investigate the fundamental biological principles underlying follicle maturation. This review describes recent advances in ovarian follicle culture, and highlights the tissue engineering principles that may be applied to follicle culture, with the ultimate objective of germline preservation for females facing premature infertility.

In vitro growth and maturation of mouse oocyte-granulosa cell complex from cryopreserved ovaries and achievement of pup birth

Ovarian tissue banking is a feasible strategy for fertility preservation for young women after cancer treatments. Ovarian tissue, after thawing, is used for several options; orthotopic grafting (normal site), autologous heterotopic grafting and collection of ovarian follicles for culture. Recent reports of live birth encouraged clinicians and researchers to apply this technology to premature ovarian failure (POF) resulting from strong cancer therapy. Grafting, however, carries a risk of malignant cell recurrence. For safety, development of a culture method is necessary but optimum culturing conditions for less-developed follicles abundant in the ovary are not well known. In the present article, the current status of ovarian tissue cryopreservation, and in vitro oocyte growth and maturation from the preserved ovaries are reviewed.

Ovarian tissue preservation, present and clinical perspectives

Ovarian tissue preservation and transplantation are intended for women undergoing aggressive regimens of chemical and/or radiological therapy, bone marrow transplantation or stem cell transplantation. Main indications for the procedure are neoplastic diseases and autoimmune disorders. The first live human birth after ovarian tissue autotransplantation was successfully done in 2002. Cryopreserved ovarian tissue can be autografted either orthotopically or heterotopically. Neovascularization of the implanted tissue is essential for the procedure. Vascular transplantation seems to be the best approach for avoiding follicular loss and extending the lifespan of the ovarian grafts. The procedure, regardless of whether ortho- or heterotopic, is connected with a risk of reimplantation of neoplastic cells. This can be minimized by multiple ovary biopsies, thorough histological examination and molecular genetic techniques. Introducing ovarian tissue transplantation into clinical practice requires many problems to be solved. Standardization of the freeze-thaw protocol is one of the most important issues. Solving the problem of transient graft ischemia is also essential. Eventually, the future safety of the method requires the development of efficient tests to detect the presence of neoplastic cells in the transplanted tissue.

Does oocyte cryopreservation have a future in Hungary?

The Committee of Human Reproduction established by the Hungarian Ministry of Health is currently working on a proposition that has the intention to ban oocyte cryopreservation in Hungary temporarily. According to the notion of the committee, oocyte cryopreservation and the utilization of frozen oocytes entail enormous risks for future generations. They argue that the safety of the method is unproven. Consequently, their standpoint maintains that cryopreservation invariably remains a grave risk factor with regards to the genetic material of the oocyte by significantly increasing the risk to the offspring. Therefore,the Committee is requesting additional animal experiments to clarify the probability of permanent lesions to the spindle and alterations to the genetic material. According to their point of view, the suspension of the method is further justified since the efficiency of the procedure has yet not reached the level required for clinical adaptation. With the proposed forthcoming step,this commentary takes the opportunity to make critical comments and clarify necessary questions.