Fertilization and development in humans

Mutational analysis of IZUMO1R in women with fertilization failure and polyspermy after in vitro fertilization

PURPOSE

The etiology of fertilization failure and polyspermy during assisted reproductive technology (ART) remains elusive. The aim of this study was to determine whether mutations in the IZUMO1 receptor (IZUMO1R) gene, which is essential for mammalian fertilization, contribute to the pathogenesis of fertilization failure or polyspermy in humans.

METHODS

We recruited 215 female subjects with fertilization failure/poor fertilization, 330 females with polyspermy, and 300 matched controls. All subjects underwent IVF treatment. Peripheral blood DNA of cases was extracted and screened for mutations in IZUMO1R gene.

RESULTS

Four rare single nucleotide polymorphisms (SNPs) of the IZUMO1R were identified among specimens from patients with fertilization failure and polyspermy but were absent in the 300 control subjects. These included a missense SNP (rs76779571 in exon 4), which was found in two fertilization failure patients, and a nonsynonymous SNP (rs61742524 in exon 1) and two synonymous SNPs (rs76781645 in exon 1 and rs377369966 in intron 2), which were found among three polyspermy cases.

CONCLUSIONS

The variations in IZUMO1R might play a role in the pathogenesis of fertilization failure and polyspermy, and the putative functions and effects of these rare variants require further studies.

Fertility conservation in breast cancer patients

Breast cancer is the most common malignant tumor in women. Increasing survival rates after breast cancer, new reproductive techniques and growing interest regarding the quality of life after cancer have brought the possibilities of fertility-preserving treatment to the center of attention of oncologists and affected patients. Many of these women suffer from infertility and premature menopause as a result of chemotherapy. Several measures, for example gonadotropin-releasing hormone analogs, hormonal stimulation to cryopreserve oocytes, ovarian tissue cryoconservation or a combination of the methods, can be undertaken depending on the hormone receptor status of the tumor, and the patient's age and partner status. Embryo cryopreservation is currently the most promising fertility preservation option. Early counseling on fertility-preserving strategies is of utmost importance, so that the fertility-preserving method can be integrated into the oncologic therapy regime.

A critical evaluation of ovarian tissue cryopreservation and grafting as a strategy for preserving the human female germline

Ovarian tissue freezing has been used successfully in animals and it has recently begun to be offered clinically to young women who have medical conditions with a high risk of sterility. Although no frozen human ovarian grafts have yet been returned to the donor and resulted in a pregnancy, there are many indications that this procedure should be feasible. Although live young have been derived from frozen grafts in several species, research should aim to make further improvements to the cryopreservation and grafting procedures to optimize follicle survival, and hence minimize the amount of tissue that needs to be collected, stored and returned. Ovarian tissue freezing, particular if used in combination with egg and embryo freezing, should allow a patient to safeguard their chance of becoming a parent later (Table 1). In cases where the patient has a systemic cancer or infection and malignant cells or viruses may be present in the systemic circulation and the gonadal tissue, ovarian tissue could be collected and frozen, but grafting is not currently recommended (Table 3).

Increased messenger ribonucleic acid expression of the cyclin-dependent kinase inhibitor p27Kip1 in cleavage-stage human embryos exhibiting developmental arrest

OBJECTIVE

To quantify p27 messenger RNA (mRNA) levels in human arrested and normally developing embryos and nonfertilized oocytes to determine whether the p27 protein abundance, reported in cleavage-stage embryos exhibiting developmental arrest, is regulated at the mRNA expression level.

DESIGN

Real-time reverse transcription quantitative polymerase chain reaction was used to quantify the expression of p27 in three samples: arrested embryos (group A, n = 29), normally developing embryos (group D, n = 34), and nonfertilized oocytes (group O, n = 20).

SETTING

Research laboratory working closely with a clinical IVF practice.

PATIENT(S)

Oocytes and embryos were obtained from patients undergoing assisted fertilization.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Quantification of mRNA transcripts.

RESULT(S)

The amount of p27 mRNA was statistically significantly higher in group A (mean +/- SEM, 86,143 +/- 42,496 relative units [RU]) compared with groups D (10,680 +/- 3,850 RU) and O (3,555 +/- 1,458 RU). Furthermore, in a group of 13 two- to four-cell arrested embryos, high levels of p27 mRNA (51,481 +/- 31,120 RU) were found in comparison with the nonfertilized oocyte group (3,555 +/- 1,458 RU).

CONCLUSION(S)

Cleavage-stage human embryos exhibiting developmental arrest show increased p27 mRNA expression. This probably is due to increased transcriptional activity.

Effect of choline-supplemented sodium-depleted slow freezing versus vitrification on mouse oocyte meiotic spindles and chromosome abnormalities

OBJECTIVE

To evaluate and compare vitrification and choline-supplemented sodium-depleted slow freezing of mouse oocytes.

DESIGN

Animal study.

SETTING

University-affiliated hospital.

ANIMAL(S)

CD-1 mice.

INTERVENTION(S)

Oocyte cryopreservation by vitrification or choline-supplemented sodium-depleted slow freezing.

MAIN OUTCOME MEASURE(S)

Survival rate, fertilization and embryonic development in vitro, meiotic spindle and chromosome configuration, and aneuploidy screening after parthenogenetic activation.

RESULT(S)

A total of 564 oocytes were vitrified, and 791 oocytes were cryopreserved using the slow freezing. The survival rates were 91.8% (518/564) and 73.3% (579/791), respectively. After IVF, the cleavage and blastocyst formation rates of vitrified oocytes were significantly higher than those of slow-frozen oocytes (63.6% vs. 39.9% and 30.50% vs. 20.2%, respectively). Vitrified oocytes were more likely than slow-frozen oocytes to maintain normal meiotic spindles and chromosome alignment (86.9% vs. 70.1%). However, the incidence of aneuploidy was similar in vitrified oocytes and slow-frozen oocytes (9.30% vs. 8.7%).

CONCLUSION(S)

Vitrification is superior to choline-supplemented sodium-depleted slow freezing, leading to improved survival, fertilization, and embryonic development in vitro. Analysis of meiotic spindle integrity and chromosome alignment indicates that less damage was detected in vitrified oocytes. However, the incidence of aneuploidy is similar in both vitrified and slow-frozen oocytes.

Effect of in vitro fertilization on gene expression and development of mouse preimplantation embryos

In vitro culture (IVC) of preimplantation mouse embryos is associated with changes in gene expression. It is however, not known if the method of fertilization affects the global pattern of gene expression. We compared gene expression and development of mouse blastocysts produced by in vitro fertilization (IVF) versus blastocysts fertilized in vivo and cultured in vitro from the zygote stage (IVC) versus control blastocysts flushed out of the uterus on post coital day 3.5. The global pattern of gene expression was assessed using the Affymetrix 430 2.0 chip. It appears that each method of fertilization has a unique pattern of gene expression and development. Embryos cultured in vitro had a reduction in the number of trophoblastic cells (IVF 33.5 cells, IVC 39.9 cells, and 49.6 cells in the in vivo group) and, to a lesser degree, of inner cell mass cells (12.8, 11.7, and 13.8 respectively). The inner cell mass nuclei were larger after culture in vitro (140 microm(2), 113 microm(2), and 86 microm(2) respectively). Although a high number of genes (1912) was statistically different in the IVF cohort when compared with the in vivo control embryos, the magnitude of the changes in gene expression were low and only a minority of genes (29 genes) was changed more than fourfold. Surprisingly, IVF embryos were different from IVC embryos (3058 genes were statistically different, but only three changed more than fourfold). Proliferation, apoptosis, and morphogenetic pathways are the most common pathways altered after IVC. Overall, IVF and embryo culture have a profound effect on gene expression pattern and phenotype of mouse preimplantation embryos.

Differential staining combined with TUNEL labelling to detect apoptosis in preimplantation bovine embryos

Development of accurate laboratory methods to assess embryo quality will improve the efficiency of embryo production from in-vitro culture systems. Currently, the techniques of TdT (terminal deoxynucleotidyl transferase)-mediated dUDP nick-end (TUNEL) labelling for the detection of apoptosis, and differential staining for determining the ratio of inner cell mass (ICM) to trophectoderm (TE) cells, are used separately to assess embryo quality in a range of different species. This paper reports a unique, simple and fast method for the assessment of embryo quality using differential staining of TE and ICM, but combined with TUNEL labelling (DST staining). This technique was used to investigate the effect of serum supplementation on total cell number, ICM:TE ratio and apoptosis index after in-vitro production of bovine embryos. Serum supplementation increased total cell number (P < 0.01), but reduced the ratio of ICM:TE cells. No differences were observed in the number of apoptotic nuclei between treatments, or in the localization of the apoptotic nuclei. However, more apoptotic nuclei were observed in ICM than TE cells in both culture groups. In conclusion, using DST, it has been possible to carry out both a qualitative and quantitative analysis of embryos produced using the two different methods. DST provides a means of assessing the effect of culture conditions on cell number of both embryo compartments (ICM and TE), as well as providing information on the localization of apoptotic nuclei within the blastocyst.

Derivation, growth and applications of human embryonic stem cells

Human embryonic stem (hES) cells are pluripotent cells derived from the inner cell mass cells of blastocysts with the potential to maintain an undifferentiated state indefinitely. Fully characterised hES cell lines express typical stem cell markers, possess high levels of telomerase activity, show normal karyotype and have the potential to differentiate into numerous cell types under in vitro and in vivo conditions. Therefore, hES cells are potentially valuable for the development of cell transplantation therapies for the treatment of various human diseases. However, there are a number of factors which may limit the medical application of hES cells: (a) continuous culture of hES cells in an undifferentiated state requires the presence of feeder layers and animal-based ingredients which incurs a risk of cross-transfer of pathogens; (b) hES cells demonstrate high genomic instability and non-predictable differentiation after long-term growth; and (c) differentiated hES cells express molecules which could cause immune rejection. In this review we summarise recent progress in the derivation and growth of undifferentiated hES cells and their differentiated progeny, and the problems associated with these techniques. We also examine the potential use of the therapeutic cloning technique to derive isogenic hES cells.

Deadly decisions: the role of genes regulating programmed cell death in human preimplantation embryo development

Human preimplantation embryo development is prone to high rates of early embryo wastage, particularly under current in vitro culture conditions. There are many possible underlying causes for embryo demise, including DNA damage, poor embryo metabolism and the effect of suboptimal culture media, all of which could result in an imbalance in gene expression and the failed execution of basic embryonic decisions. In view of the complex interactions involved in embryo development, a thorough understanding of these parameters is essential to improving embryo quality. An increasing body of evidence indicates that cell fate (i.e. survival/differentiation or death) is determined by the outcome of specific intracellular interactions between pro- and anti-apoptotic proteins, many of which are expressed during oocyte and preimplantation embryo development. The recent availability of mutant mice lacking expression of various genes involved in the regulation of cell survival has enabled rapid progress towards identifying those molecules that are functionally important for normal oocyte and preimplantation embryo development. In this review we will discuss the current understanding of the regulation of cell death gene expression during preimplantation embryo development, with a focus on human embryology and a discussion of animal models where appropriate.

Gynaecologic concerns for young women exposed to gonadotoxic chemotherapy

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

Gestação obtida em coelha após ooforectomia bilateral e transplante ovariano homógeno

OBJETIVO: Verificar a possibilidade de fertilização natural após ooforectomia total bilateral e transplante ovariano homógeno ortotópico sem anastomose vascular e imunossuprimidos pela ciclosporina. MÉTODO: Foram utilizadas dez coelhas da raça Nova Zelândia Branca e Califórnia. Realizou-se ooforectomia total bilateral e transplante ortotópico dos ovários entre pares de animais. De um lado, foi transplantado o ovário íntegro e de outro, o ovário fatiado. Não houve anastomose vascular. A imunossupressão se deu com a administração ciclosporina através de tubo orogástrico diariamente, durante seis meses. Três meses depois, as fêmeas foram colocadas diariamente para copular com machos sabidamente férteis da raça Nova Zelândia Branca, por outros seis meses. No final do período do experimento, foram realizadas dosagens de estradiol, progesterona, hormônio folículo estimulante e hormônio luteinizante, além de estudo histológico dos ovários, tubas e úteros. RESULTADOS: Gravidezes ocorreram em cinco coelhas, sendo que, em quatro delas, houve nascimento de filhotes. As dosagens hormonais estiveram dentro da faixa de normalidade em todos os animais. Os ovários transplantados estavam rodeados de tecido conjuntivos, bem vascularizados e com folículos ovarianos em vários estádios de desenvolvimento. CONCLUSÕES: Obteve-se, com sucesso, a fertilização natural e manutenção hormonal feminina em coelhas submetidas a transplante homógeno de tecido ovariano sem anastomose vascular e imunossuprimidos pela ciclosporina.

Cold-induced calcium elevation triggers DNA fragmentation in immature pig oocytes

Fluo-4 loaded immature oocytes were cooled from 30 degrees C to various lower temperatures between 20 and 10 degrees C and changes in intracellular calcium (Ca(2+)) levels were measured. Pig oocytes cooled to 14 degrees C exhibited a clear biphasic Ca(2+) rise. Lower temperatures produced similar responses, while higher temperatures did not exert any effect. The Ca(2+) response appeared to rely on ryanodine dependent stores as removal of extracellular Ca(2+) and intracytoplasmic injection of heparin did not modify cold-induced Ca(2+) elevation, while procaine or ruthenium red virtually eliminated the response. Confocal analysis of subcellular Ca(2+) distribution during cooling revealed that the ion rises sharply within the nucleus. As Ca(2+) imbalance may activate nuclear endonucleases, DNA integrity of cooled pig oocytes was evaluated by TUNEL and comet assays. Most cooled oocytes showed clear signs of DNA fragmentation. Oocytes injected with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetracetic acid tetrapotassium salt (BAPTA), a Ca(2+) chelator, maintained their DNA integrity thus confirming that intracellular Ca(2+) is involved in triggering DNA fragmentation. The protective effect exerted by ruthenium red and/or procaine further confirmed this hypothesis. These data show that a moderate and transient cooling is sufficient to cause an intracellular Ca(2+) rise that leads to DNA damage. The addition of inhibitors of ryanodine dependent Ca(2+) stores may represent a valuable protective treatment to reduce chilling injuries.

Amplification of representative cDNA pools from single human oocytes and pronucleate embryos

In the human embryo, gene expression studies have been hindered by the scarcity of material and the fact that in vitro fertilisation (IVF) embryos available for research are usually of poor quality and are, therefore, not representative of normal development. This has led most authors to study individual human embryos, using conventional RT-PCR strategies, which permit analysis of only a few genes. Variability in the expression of genes between individual embryos is characteristic of these studies. In this study, a global RT-PCR strategy has been used, allowing the analysis of an almost infinite number of genes from a single embryo. We have used oocytes, which failed to fertilise and representative pronucleate embryos donated from cycles in which the patient conceived, to investigate possible variability in transcript abundance between individual embryos. We have screened oocytes and embryos for a panel of genes including beta-actin (expressed in 24/28 oocytes, 6/6 pronuclear embryos), the integrins beta1 (17/28 oocytes, 6/6 pronuclear embryos) and beta5 (8/28 oocytes, 5/6 pronuclear embryos), and the apoptotic regulators BCL-2 (20/28 oocytes, 2/6 pronuclear embryos) and BAX (21/28 oocytes, 5/6 pronuclear embryos). The expression of the pro-apoptotic regulator BAX increased in human oocytes following prolonged periods of culture. Overall, patterns of gene transcript presence showed variation between embryos and this was independent of either zona removal or lysis conditions. Pronucleate embryos showed less variation, however, even sibling embryos from the patient did not express an identical subset of genes.

Fertility after treatment for Hodgkin's disease

BACKGROUND

The investigational endeavors of ovarian cryopreservation await the clinical experience of auto- or xenotransplantation, in vitro maturation of thawed primordial follicles, their in vitro fertilization and embryo transfer. Although promising, this experience is not yet available. Moreover, the risk of possible reimplantation of malignant stem cells with the thawed cryoperserved ovary has been raised following experimental animal observations. Therefore, until these innovative endeavors prove successful, we have attempted to minimize the gonadotoxic effect of chemotherapy by the co-treatment with a gonadotropin-releasing hormone agonistic analog (GnRH-a) to induce a temporary prepubertal milieu. The immunoreactive inhibin-A and -B in these patients was measured before, during and following the gonadotoxic chemotherapy.

METHODS

A prospective clinical protocol was undertaken in 60 women aged 15-40 years with lymphoma, 10 with leukemia and 10 undergoing chemotherapeutic treatments for non-malignant diseases such as systemic lupus erythematosus or other autoimmune diseases. A monthly injection of depot D-TRP(6)-GnRH-a was administered from before starting the chemotherapy until its conclusion, up to a maximum of 6 months. Hormonal profile [follicle-stimulating hormone (FSH), luteinizing hormone (LH), E2, T, P4, insulin-like growth factor (IGF)-1, IGF-BP3 and prolactin) was taken before starting the GnRH-a/chemotherapy co-treatment, and monthly thereafter until resumtion of spontaneous ovulation. This group was compared with a control group of 60 women who have been treated with similar chemotherapy.

RESULTS

Whereas all but three (40, 36 and 34 year old) of the surviving patients within the GnRH-a/ chemotherapy co-treatment group resumed spontaneous ovulation and menses within 12 months, less than half of the patients in the 'control' group (chemotherapy without GnRH-a co-treatment) resumed ovarian function and regular cyclic activity (P <0.05). The remaining 55% experienced premature ovarian failure (POF). Temporarily increased FSH concentrations were experienced by about one-third of the patients resuming cyclic ovarian function, suggesting reversible ovarian damage in a larger proportion of women than those experiencing POF. Inhibin-A and -B decreased during the GnRH-a/ chemotherapy co-treatment but increased to normal levels in patients who resumed regular ovarian cyclicity, and/or spontaneously conceived, as compared with low levels in those who developed POF.

CONCLUSIONS

If these preliminary data are consisent in a larger group of patients, GnRH-a co-treatment should be considered in every woman of reproductive age receiving chemotherapy, in addition to assisted reproductive technologies and the investigation into ovarian cryopreservation for future in vitro maturation, autotransplantation or xenotransplantation.

Preservation of fertility and ovarian function and minimalization of chemotherapy associated gonadotoxicity and premature ovarian failure: the role of inhibin-A and -B as markers

BACKGROUND

Following the improved long term survival in young women with lymphoma and leukemia undergoing chemotherapy, the preservation of future fertility has been the focus of recent interest. The investigational endeavors of ovarian cryopreservation awaits the clinical experience of in-vitro maturation of thawed primordial follicles, their in-vitro fertilization and ET. Although promising, this experience is not available yet. Moreover, the risk of possible reimplantation of malignant stem cells with the thawed cryopreserved ovary has been raised, following experimental animal observations. Therefore, until these innovative endeavors prove successful, and in parallel to them we attempted to minimize the gonadotoxic effect of chemotherapy by the co-treatment with a GnRH agonistic analogue to induce a temporary prepubertal milieu. Whereas, inhibin-B concentrations in serum may reflect the ovarian granulosa cell compartment, inhibin-A reflects luteal function. The immunoreactive inhibin-A and -B in these patients, before, during, and following the gonadotoxic chemotherapy were measured.

METHODS

A prospective clinical protocol was undertaken in 55 women with lymphoma, aged 15-40 years, ten with leukemia and eight undergoing chemotherapeutic treatments for non malignant diseases such as systemic lupus erythematosus (SLE) or other autoimmune diseases. A monthly injection of depot D-TRP6-GnRH-a was administered from before starting the chemotherapy until its conclusion, up to a maximum of 6 months. Hormonal profile (FSH, LH, E2, T, P4, IGF-1, IGF-BP3, and PRL) was taken before starting the GnRH-a/chemotherapy co-treatment, and monthly thereafter, until resuming spontaneous ovulation. This group was compared with a control group of 55 women who have been treated with similar chemotherapy. Inhibin-A and -B immunoactivity was measured by an ELISA commercial kit (Serotec).

RESULTS

Whereas, all but three (40- and 36-year-old) of the surviving patients with GnRH-a/chemotherapy co-treatment group resumed spontaneous ovulation and menses within 12 months, less than half of the patients in the control group (chemotherapy without GnRH-a co-treatment) resumed ovarian function and regular cyclic activity (P<0.05). The remaining 56% experienced premature ovarian failure (POF). Temporary increased FSH concentrations were experienced by about a third of the patients resuming cyclic ovarian function, suggesting a reversible ovarian damage in a larger proportion of women than those experiencing POF. Inhibin-A and -B decreased during the GnRH-a/chemotherapy co-treatment but increased to normal levels in patients who resumed regular ovarian cyclicity, and/or spontaneously conceived, as compared with low levels in those who developed POF.

CONCLUSIONS

If these preliminary data are consistent in a larger group of patients, inhibin-A or -B concentrations may serve as prognostic factors for predicting the resumption of ovarian function, in addition to the levels of FSH, LH and E2. The GnRH-a co-treatment should be considered in every woman in the reproductive age receiving chemotherapy, in addition to ART, and to the investigational attempts of ovarian cryopreservation for future in-vitro maturation, autotransplantation, or xenotransplantation.

Fundamental cryobiology of mammalian oocytes and ovarian tissue

Embryo cryopreservation is a widely used and relatively well-established procedure. By contrast, ovarian tissue and unfertilized oocytes are only rarely cryopreserved, even though for germ line storage these often would be preferable to embryo cryopreservation. There are many reasons for this discrepancy. Unfertilized mature (MII) stage oocytes are more difficult to cryopreserve than cleavage stage embryos of the same species. Many factors contribute to this including the oocyte's surface to volume ratio, single membrane, temperature-sensitive metaphase spindle and zona, and its susceptibility to parthenogenetic activation and chill-injury. A completely different set of problems applies to primordial follicles. Oocytes in primordial follicles are very small and tolerate cryopreservation by slow cooling very well. The problem lies in the difficulty in producing mature oocytes from these primordial follicles. Better and/or more convenient cryopreservation procedures for both oocytes and ovarian tissue are being developed. This paper describes some of the advances in this area and outlines the relative merits and limitations of several currently available egg and ovarian tissue cryopreservation procedures.

Ovarian injury and modern options to preserve fertility in female cancer patients treated with high dose radio-chemotherapy for hemato-oncological neoplasias and other cancers

High dose chemotherapy and radiotherapy have radically increased long term survival of young cancer patients. Among the side effects of chemotherapy treatments are ovarian failure and infertility, which are of particularly great concern to young cancer patients. Recently, cryopreservation procedures such as in vitro fertilization and embryo storage, or ovarian tissue cryopreservation have been used to preserve fertility in patients subjected to cancer treatments. Knowledge of the risks and probabilities of ovarian failure as well as the risks of the cryopreservation procedures is crucial for patients and physicians in order to make informed choices that will best serve the patients interests. This article presents data of a prospective study that determines the risk of ovarian failure following exposure to chemotherapy as well as a review of related publications. Progressive, dose-related depletion of primordial follicles is noted on histology, explaining the risk of undergoing premature ovarian failure years after exposure to chemotherapy. The safety of ovarian tissue cryopreservation procedures with a new round biopter was evaluated, as well as the risk of malignant cell transmission. It has been shown that laproscopic ovarian biopsy performed with the round biopter is a safe and efficient method for collection of ovarian tissue in cancer patients. In Hodgkin's disease patients' ovarian cortical tissue obtained for cryopreservation does not contain malignant cells. However the risk of cryopreserving and transferring malignant cells should be tested separately for each disease according to the risk of ovarian metastasis and the ability to detect single malignant cells.

Long-term ovarian function in sheep after ovariectomy and transplantation of autografts stored at -196 C

We have previously demonstrated that ovarian function and fertility can be preserved in sheep after castration by autotransplantation of cryopreserved strips of ovarian cortex. In the current experiments we have investigated the long term survival of such grafts by detailed measurements of ovarian function for a period of nearly 2 yr after autotransplantation. After ovariectomy and transplantation of frozen/thawed grafts, the concentrations of FSH and LH rose to castrate levels for about 14 weeks before falling gradually to reach near-normal levels at about 60 weeks. In the breeding season from October 1994 to March 1995, all ewes had 5-10 estrous cycles that were similar in length to those in the 4 control ewes. Luteal function as indicated by the progesterone concentration was identical before and 11 months after transplantation. In contrast, the basal concentrations of FSH and LH were persistently raised throughout the luteal phase, but showed a normal decline during the follicular phase. The concentration of inhibin A in ovarian venous plasma measured at the end of the experiment 22 months after transplantation was significantly lower than that in control ewes (mean +/- SE, 409 +/- 118 vs. 1914 +/- 555 pg/ml; P < 0.004). Transplantation of frozen/thawed ovarian tissue to SCID mice demonstrated that about 28% of primordial follicles survived the procedure. All of the ovaries transplanted into sheep contained large antral follicles and/or cysts, but very few primordial oocytes when recovered at autopsy after 22 months. These results demonstrate that despite a drastic reduction in the total number of primordial follicles, cyclical ovarian function is preserved in sheep after autotransplantation of frozen/thawed ovarian tissue and provide experimental confirmation that such a technique could provide a means of preserving fertility in women undergoing chemo- or radiotherapy for malignant disease.