Functional studies of subcutaneous ovarian transplants in non-human primates: steroidogenesis, endometrial development, ovulation, menstrual patterns and gamete morphology

Ovarian tissue damage after grafting: systematic review of strategies to improve follicle outcomes

Frozen-thawed human ovarian tissue endures large-scale follicle loss in the early post-grafting period, characterized by hypoxia lasting around 7 days. Tissue revascularization occurs progressively through new vessel invasion from the host and neoangiogenesis from the graft. Such reoxygenation kinetics lead to further potential damage caused by oxidative stress. The aim of the present manuscript is to provide a systematic review of proangiogenic growth factors, hormones and various antioxidants administered in the event of ovarian tissue transplantation to protect the follicle pool from depletion by boosting revascularization or decreasing oxidative stress. Although almost all investigated studies revealed an advantage in terms of revascularization and reduction in oxidative stress, far fewer demonstrated a positive impact on follicle survival. As the cascade of events driven by ischaemia after transplantation is a complex process involving numerous players, it appears that acting on specific molecular mechanisms, such as concentrations of proangiogenic growth factors, is not enough to significantly mitigate tissue damage. Strategies exploiting the activated tissue response to ischaemia for tissue healing and remodelling purposes, such as the use of antiapoptotic drugs and adult stem cells, are also discussed in the present review, since they yielded promising results in terms of follicle pool protection.

Influence of hydrogel encapsulation during cryopreservation of ovarian tissues and impact of post-thawing in vitro culture systems in a research animal model

Objective

Using domestic cats as a biomedical research model for fertility preservation, the present study aimed to characterize the influences of ovarian tissue encapsulation in biodegradable hydrogel matrix (fibrinogen/thrombin) on resilience to cryopreservation, and static versus non-static culture systems following ovarian tissue encapsulation and cryopreservation on follicle quality.

Methods

In experiment I, ovarian tissues (n=21 animals; 567 ovarian fragments) were assigned to controls or hydrogel encapsulation with 5 or 10 mg/mL fibrinogen (5 or 10 FG). Following cryopreservation (slow freezing or vitrification), follicle viability, morphology, density, and key protein phosphorylation were assessed. In experiment II (based on the findings from experiment I), ovarian tissues (n=10 animals; 270 ovarian fragments) were encapsulated with 10 FG, cryopreserved, and in vitro cultured under static or non-static systems for 7 days followed by similar follicle quality assessments.

Results

In experiment I, the combination of 10 FG encapsulation/slow freezing led to greater post-thawed follicle quality than in the control group, as shown by follicle viability (66.9%±2.2% vs. 61.5%±3.1%), normal follicle morphology (62.2%±2.1% vs. 55.2%±3.5%), and the relative band intensity of vascular endothelial growth factor protein phosphorylation (0.58±0.06 vs. 0.42±0.09). Experiment II demonstrated that hydrogel encapsulation promoted follicle survival and maintenance of follicle development regardless of the culture system when compared to fresh controls.

Conclusion

These results provide a better understanding of the role of hydrogel encapsulation and culture systems in ovarian tissue cryopreservation and follicle quality outcomes using an animal model, paving the way for optimized approaches to human fertility preservation.

Delaying Reproductive Aging by Ovarian Tissue Cryopreservation and Transplantation: Is it Prime Time?

Ovarian tissue cryopreservation and autotransplantation can restore ovarian endocrine function and fertility and recently were changed from experimental to fertility preservation procedures for medical indications by the American Society of Reproductive Medicine. Such advances have resulted in discussions around the utility of ovarian cryopreservation in healthy women to preserve fertility and delay menopause or as a hormone replacement approach. Such 'elective' use of ovarian tissue cryopreservation requires a risk-benefit assessment. Here, we review evidence for and against the utility of ovarian tissue harvesting in healthy women, scrutinize recent and needed advances to enhance the feasibility of such an approach, and provide practice and future research guidelines.

Ovarian tissue vitrification is more efficient than slow freezing to preserve ovarian stem cells in CF-1 mice

OBJECTIVE

The aim of this study was to investigate the efficacy of protocols for mice ovary cryopreservation to compare the differences in Mouse Vasa Homologue expression (a germline cell marker) and ovarian viability after vitrification or slow freezing.

METHODS

Female CF1 mice aged 40-45 days were randomly divided into three groups: Control, vitrification or slow freezing. Their ovaries were surgically removed, rinsed in saline solution and cryopreserved. For vitrification, we used a commercial protocol and for slow freeze, we used 1.5 M ethylene glycol (EG) as cryoprotectant. After that, the ovaries were processed for histological an immunohistochemical analysis, and counting of primordial, primary, pre-antral and antral follicles.

RESULTS

No significant difference was found in the proportion of high-quality primordial, primary and pre-antral follicles after thawing/warming in the slow freezing and vitrification groups. The immunohistochemistry for MVH antibody demonstrated that the slow freeze group had a higher number of unmarked cells (p=0.012), indicating a harmful effect on the MVH expression in the ovarian tissue, where the cell structure is complex.

CONCLUSION

Although both protocols indicated similar results in the histological analysis of follicular counts, the vitrification protocol was significantly better to preserve ovarian stem cells, an immature germ cell population. These cells are able to self-renew having regeneration potential, and may be effective for the treatment of ovarian failure and consequently infertility.

Strong Heterogeneity in Advances in Cryopreservation Techniques in the Mammalian Orders

Between 1970 and 2012, vertebrate abundance has declined by 58% with an average annual decline of 2%, calling for serious action to prevent a mass extinction and an irreversible loss of biodiversity. Cryobanks and cryopreservation have the potential to assist and improve ex situ and in situ conservation strategies by storing valuable genetic material. A great deal of studies concerning cryopreservation have been performed within the class Mammalia, although no systematic overview has previously been presented. The objective of this study is therefore to evaluate the status, pattern and future of cryopreservation within Mammalia. A strong disproportional distribution of studies in examined orders is displayed. For the majority of examined orders less than 10% of species has been examined. However, the cryopreservation of germplasm has in several cases been successful and resulted in successful applications of assisted reproductive techniques (ARTs). Various obstacles are associated with the development of cryopreservation protocols, and among them the most prominent is interspecific differences in cryotolerance. Extrapolation of protocols in closely related species is considered the most applicable procedure, and a future supplement to overcome this problem is the examination and comparison of cryobiological traits. Successful protocols have been developed for the vast majority of domesticated mammals, which gives incentive for the further extrapolation of protocols in threatened species.

Expectations and limitations of ovarian tissue transplantation

Constant progress in the diagnosis and treatment of cancer disease has increased the number and prognosis of cancer survivors. However, the toxic effects of chemotherapy and radiotherapy on ovarian function have resulted in premature ovarian failure. Patients are, therefore, still expecting methods to be developed to preserve their fertility successfully. Several potential options are available to preserve fertility in patients who face premature ovarian failure, including immature or mature oocyte and embryo cryopreservation. However, for children or prepubertal women needing immediate chemotherapy, cryopreservation of ovarian tissue is the only alternative. The ultimate aim of this strategy is to implant ovarian tissue into the pelvic cavity (orthotopic site) or in a heterotopic site once oncological treatment is completed and the patient is disease free. Transplantation of ovarian tissue with sufficiently large numbers of follicles could potentially restore endocrine function and allow multiple cycles for conception. However, the success of ovarian tissue transplantation still has multiple challenges, such as the low number of follicles in the graft that may affect their longevity as well as the survival of the tissue during ex vivo processing and subsequent transplantation. Therefore, this review aims to summarize the achievements of ovary grafting and the potential techniques that have been developed to improve ovarian graft survival.

Strategies for Fertility Preservation in Female and Male Cancer Survivors

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

Use of nonhuman primates for the development of bioengineered female reproductive organs

Nonhuman primates (NHPs) have been widely used in reproductive biology, neuroscience, and drug development since a number of primate species are phylogenetically close to humans. In this review, we summarize the use of NHPs for nonclinical application in the reproductive system disorders including the loss or failure of an organ or tissue. Causes of infertility include congenital aplasia and acquired disorders of the reproductive organs. In addition, anti-cancer treatments can deplete ovarian follicles, leading to premature ovarian failure, infertility and long-term health risks. Along with a limited supply of human reproductive organs, anatomic/physiologic similarities to humans support the need for NHP models (New-World monkeys such as the common marmoset and Old-World monkeys such as cynomolgus and rhesus monkeys) to promote the advances in female infertility studies. For maintaining and executing animal studies using NHP, special protocols including animal care, anesthetic protocol, surgical technique, and immunosuppressive protocol are necessary. With a growing interest in the potential therapies such as endometrial tissue engineering, and ovary/follicle cryopreservation and grafting in Korea, this review can be useful in selecting appropriate animal models and can bridge between nonclinical studies and clinical applications by providing detailed information on the use of NHPs in the field of reproductive organ disorders.

VEGF and FGF2 Improve Revascularization, Survival, and Oocyte Quality of Cryopreserved, Subcutaneously-Transplanted Mouse Ovarian Tissues

This study was conducted to investigate the effect of the vascular endothelial growth factor (VEGF) and fibroblast growth factor 2 (FGF2) on revascularization, survival, and oocyte quality of cryopreserved, subcutaneously-transplanted mouse ovarian tissue. Autologous subcutaneous transplantation of vitrified-thawed mouse ovarian tissues treated with (experimental group) or without (control group) VEGF and FGF2 was performed. After transplantation to the inguinal region for two or three weeks, graft survival, angiogenesis, follicle development, and oocyte quality were examined after gonadotropin administration. VEGF coupled with FGF2 (VEGF/FGF2) promoted revascularization and significantly increased the survival rate of subcutaneously-transplanted cryopreserved ovarian tissues compared with untreated controls. The two growth factors did not show long-term effects on the ovarian grafts. In contrast to the untreated ovarian grafts, active folliculogenesis was revealed as the number of follicles at various stages and of mature oocytes in antral follicles after gonadotropin administration were remarkably higher in the VEGF/FGF2-treated groups. Although the fertilization rate was similar between the VEGF/FGF2 and control groups, the oocyte quality was much better in the VEGF/FGF2-treated grafts as demonstrated by the higher ratio of blastocyst development. Introducing angiogenic factors, such as VEGF and FGF2, may be a promising strategy to improve revascularization, survival, and oocyte quality of cryopreserved, subcutaneously-transplanted mouse ovarian tissue.

Cryopreservation of ovaries from neonatal marmoset monkeys

The ovary of neonatal nonhuman primates contains the highest number of immature oocytes, but its cryopreservation has not yet been sufficiently investigated in all life stages. In the current study, we investigated cryodamage after vitrification/warming of neonatal ovaries from a nonhuman primate, the common marmoset (Callithrix jacchus). A Cryotop was used for cryopreservation of whole ovaries. The morphology of the vitrified/warmed ovaries was found to be equivalent to that of fresh ovaries. No significant difference in the number of oocytes retaining normal morphology per unit area in histological sections was found between the two groups. In an analysis of dispersed cells from the ovaries, however, the cell viability of the vitrified/warmed group tended to be decreased. The results of a comet assay showed no significant differences in DNA damage. These results show that cryopreservation of neonatal marmoset ovaries using vitrification may be useful as a storage system for whole ovaries.

Does adipose tissue-derived stem cell therapy improve graft quality in freshly grafted ovaries?

BACKGROUND

A major concern in ovarian transplants is substantial follicle loss during the initial period of hypoxia. Adipose tissue-derived stem cells (ASCs) have been employed to improve angiogenesis when injected into ischemic tissue. This study evaluated the safety and efficacy of adipose tissue-derived stem cells (ASCs) therapy in the freshly grafted ovaries 30 days after injection.

METHODS

Rat ASCs (rASCs) obtained from transgenic rats expressing green fluorescent protein (GFP)-(5 × 10(4) cells/ovary) were injected in topic (intact) or freshly grafted ovaries of 30 twelve-week-old adult female Wistar rats. The whole ovary was grafted in the retroperitoneum without vascular anastomosis, immediately after oophorectomy. Vaginal smears were performed daily to assess the resumption of the estrous cycle. Estradiol levels, grafts morphology and follicular viability and density were analyzed. Immunohistochemistry assays were conducted to identify and quantify rASC-GFP(+), VEGF tissue expression, apoptosis (cleaved caspase-3 and TUNEL), and cell proliferation (Ki-67). Quantitative gene expression (qPCR) for VEGF-A, Bcl2, EGF and TGF-β1 was evaluated using RT-PCR and a double labeling immunofluorescence assay for GFP and Von Willebrand Factor (VWF) was performed.

RESULTS

Grafted ovaries treated with rASC-GFP(+) exhibited earlier resumption of the estrous phase (p < 0.05), increased VEGF-A expression (11-fold in grafted ovaries and 5-fold in topic ovaries vs. control) and an increased number of blood vessels (p < 0.05) in ovarian tissue without leading to apoptosis or cellular proliferation (p > 0.05). Estradiol levels were similar among groups (p > 0.05). rASC-GFP(+) were observed in similar quantities in the topic and grafted ovaries (p > 0.05), and double-labeling for GFP and vWF was observed in both injected groups.

CONCLUSION

rASC therapy in autologous freshly ovarian grafts could be feasible and safe, induces earlier resumption of the estrous phase and enhances blood vessels in rats. This pilot study may be useful in the future for new researches on frozen-thawed ovarian tissue.

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

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

Effect of antifreeze protein on mouse ovarian tissue cryopreservation and transplantation

PURPOSE

To investigate the effect of antifreeze protein (AFP) supplementation on ovarian vitrification and transplantation.

MATERIALS AND METHODS

In this experimental study, we researched a total of 182 ovaries from 4-week-old ICR mice. The equilibration solution included 20% ethylene glycol (EG), and the vitrification solution included 40% EG, 18% Ficoll, and 0.3 M sucrose. Intact ovaries were first suspended in 1 mL of equilibration solution for 10 min, and then mixed with 0.5 mL of vitrification solution for 5 min. Ovaries were randomly assigned to 3 groups and 0, 5, or 20 mg/mL of type III AFP was added into the vitrification solution (control, AFP5, and AFP20 groups, respectively). The vitrified ovaries were evaluated after warming and 2 weeks after autotransplantation. The main outcome measurements are follicular morphology and apoptosis assessed by histology and the TUNEL assay.

RESULTS

A significantly higher intact follicle ratio was shown in the AFP treated groups (control, 28.9%; AFP5, 42.3%; and AFP20, 44.7%). The rate of apoptotic follicles was significantly lower in the AFP treated groups (control, 26.6%; AFP5, 18.7%; and AFP20, 12.6%). After transplantation of the vitrified-warmed ovaries, a significantly higher intact follicle ratio was shown in the AFP20 group. The rate of apoptotic follicles was similar among the groups.

CONCLUSION

The results of the present study suggest that supplementing AFP in the vitrification solution has beneficial effects on the survival of ovarian tissue during cryopreservation and transplantation.

Effect of preoperative simvastatin treatment on transplantation of cryopreserved-warmed mouse ovarian tissue quality

After the ovarian tissue (OT) transplantation, the ischemia-reperfusion injury causes depletion and apoptosis of follicle. Recent reports stated that simvastatin reduces ischemic damage. Therefore, we used the mouse whole ovarian vitrification and autotransplantation models to investigate the effects of simvastatin. Five-week-old B6D2F1 mice were randomly divided into four groups. Three groups were given simvastatin orally (5 mg/kg) before ovariectomy, either 2 hours before (2H Tx) or once a day for 3 or 7 days. The control group was given saline 2 hours before ovariectomy. All ovaries were cryopreserved by vitrification, held in liquid nitrogen for 1 week before being warmed, and autotransplanted. The grafts were collected for analysis on 2, 7, or 21 days after transplantation. Ovarian follicle morphology and apoptosis were assessed by hematoxylin and eosin staining and terminal deoxynucleotidyl transferase dUTP nick end labeling assay. Vessel integrity in ovary was evaluated by immunohistochemistry using anti-CD31 antibody. Serum FSH level was measured to estimate the transplanted ovarian reserve. The proportion of morphologically normal (G1) follicles at 7 and 21 days and the percentage of CD31 (+) tissue at 21 days was significantly higher in the 2H Tx group than that in the control group. In addition, the 2H Tx group showed a significantly increased intact primordial follicle ratio at 2 and 21 days after OT transplantation. Administration of simvastatin 2 hours before ovariectomy could improve the quality after transplantation of cryopreserved mouse OT.

Effect of necrostatin on mouse ovarian cryopreservation and transplantation

OBJECTIVE

To investigate the effects of necrostatin-1 (Nec-1) supplementation on vitrification, warming and transplantation of ovarian tissue.

STUDY DESIGN

Ovaries from 4-week-old ICR mice were vitrified using a two-step procedure; ovaries were suspended in equilibration solution for 10min, and then mixed with vitrification solution for 5min. Ovaries were divided at random into three groups and 0 (control), 25 or 100μM Nec-1 was added to the vitrification solution. After warming, follicular morphology and apoptosis were assessed. For each group, a sample of vitrified, warmed ovaries was autotransplanted. The same dose of Nec-1 that was added to the vitrification solution was added to each warming solution and injected intraperitoneally. Follicular morphology and apoptosis of transplanted ovaries were assessed after 2 weeks.

RESULTS

After vitrification and warming, morphological analysis revealed that the intact follicle ratio was significantly higher in the Nec-1-treated groups compared with the control group (control, 45.1%; 25μM Nec-1, 51.7%; 100μM Nec-1, 57.9%). The rate of apoptosis was lower in the Nec-1 treated groups compared with the control group (control, 11.2%; 25μM Nec-1, 8.5%; 100μM Nec-1, 7.2%). After transplantation of the vitrified, warmed ovaries, morphological analysis revealed that the intact follicle ratio was significantly higher in the Nec-1 treated groups compared with the control group (control, 43.1%; 25μM Nec-1, 60.6%; 100μM Nec-1, 70.7%). The rate of apoptosis was lower in the Nec-1 treated groups compared with the control group (control, 5.3%; 25μM Nec-1, 2.5%; 100μM Nec-1, 2.0%).

CONCLUSIONS

Nec-1 supplementation during vitrification, warming and transplantation has beneficial effects on the survival of ovarian tissue. These results can help to improve ovarian tissue vitrification and transplantation protocols for fertility preservation.

Isoform 111 of vascular endothelial growth factor (VEGF111) improves angiogenesis of ovarian tissue xenotransplantation

BACKGROUND

Cryopreservation of cortex ovarian tissue before anticancer therapy is a promising technique for fertility preservation mainly in children and young women. Ischemia in the early stage after ovarian graft causes massive follicle loss by apoptosis. VEGF111 is a recently described vascular endothelial growth factor (VEGF) isoform that does not bind to the extracellular matrix, diffuses extensively, and is resistant to proteolysis. These properties confer a significantly higher angiogenic potential to VEGF111 in comparison with the other VEGF isoforms.

METHODS

We evaluated the morphology of cryopreserved sheep ovarian cortex grafted in the presence or absence of VEGF111. Ovarian cortex biopsies were embedded in type I collagen with or without VEGF111 addition before transplantation to severe combined immunodeficient mice ovaries. Transplants were retrieved 3 days or 3 weeks later. Follicular density, vasculature network, hemoglobin content, and cell proliferation were analyzed.

RESULTS

Addition of VEGF111 increased density of functional capillaries (P=0.01) 3 days after grafting. By double immunostaining of Ki-67 and von Willebrand factor, we demonstrated that proliferating endothelial cells were found in 83% of the VEGF111 group compared with 33% in the control group (P=0.001). This angiostimulation was associated with a significant enhancement of hemoglobin content (P=0.03). Three weeks after transplantation, the number of primary follicles was significantly higher in VEGF111 grafts (P=0.02).

CONCLUSION

VEGF111 accelerates blood vessel recruitment and functional angiogenesis and improves the viability of ovarian cortex by limiting ischemia and ovarian cortex damage.

Follicle development in cryopreserved bitch ovarian tissue grafted to immunodeficient mouse

The present study evaluated: (1) in vivo follicular development in canine ovarian tissue after slow freezing and xenotransplantation; and (2) the use of erythropoietin (EPO) as an angiogenic factor to optimise the transplantation procedure. Frozen-thawed ovarian tissue from five bitches was grafted into severe combined immunodeficient (SCID) mice (n=47) treated with or without EPO (500 IU kg(-1), once daily for 3 days) (Groups A and B, respectively) and analysed after 0, 1, 8 or 16 weeks. Follicle grade, follicle density, follicle morphology and stromal cells density were assessed by histological analysis, whereas vascularisation of the graft was quantified by immunohistochemistry with anti-α-smooth muscle actin antibody. Despite a massive loss of follicles after grafting, secondary follicle density was higher at 8 and 16 weeks than at 1 week regardless of EPO treatment. EPO significantly improved early follicle morphology and stromal cell density after 8 weeks and blood vessel density at 16 weeks after transplantation (P<0.05). Intact secondary follicles with more than three granulosa cells layers were observed 16 weeks after transplantation. The results suggest that canine ovarian tissue can be successfully preserved by our slow-freezing protocol because the tissue showed follicular growth after xenotransplantation. EPO treatment did not lessen the massive loss of follicles after transplantation.

Assessment of long-term function of heterotopic transplants of vitrified ovarian tissue in cynomolgus monkeys

BACKGROUND

Ovarian tissue cryopreservation by rapid cooling (vitrification) is a convenient fertility preservation option. However, the progress of vitrified ovarian tissue after transplantation is not well understood in primates.

METHODS

For tissues from cynomolgus monkeys, we used closed straw vitrification and open cryosupport vitrification in which tissues are immersed directly into liquid nitrogen. Following warming, ovarian cortical pieces were autotransplanted and their function was monitored by computed tomography (CT), hormone assays and oocyte recovery, ICSI and embryo transfers (ETs).

RESULTS

Hormone cycles were restored in 6 of 7 animals in a mean of 126 days with no significant difference between the two vitrification regimens. The presence of new blood vessels supplying the grafted ovarian tissue was confirmed by contrast-enhanced CT. Oocyte retrieval from two monkeys after transplantation of the ovarian cortex vitrified by cryosupport vitrification yielded a total of nine oocytes of which six fertilized after ICSI, but ETs did not lead to any pregnancies.

CONCLUSIONS

This work shows that CT can give insight into ovarian function after heterotopic transplantation, and that heterotopic autografts of vitrified ovarian cortex can give rise to long-term ovarian function and embryos in a primate model. It remains to be established how outcomes following rapid vitrification compared with outcomes following conventional slow cooling procedures.

Viability and function of the cryopreserved whole rat ovary: comparison between slow-freezing and vitrification

OBJECTIVE

To investigate four different protocols for cryopreservation of the whole rat ovary with intact vasculature to evaluate whether differences exist in post-thawing viability of the ovary after either vitrification or slow freezing.

DESIGN

Experimental study.

SETTING

Obstetrics and gynecology department.

ANIMAL(S)

Immature Sprague-Dawley female rats.

INTERVENTION(S)

Ovaries were isolated with the vascular tree intact up to the bifurcation of the abdominal aorta and were subsequently cannulated. The ovaries were flushed with increasing concentrations of the cryoprotectant dimethyl sulfoxide (DMSO) to either 1.5 or 7 M. The ovaries underwent cryopreservation by vitrification or passive slow freezing.

MAIN OUTCOME MEASURE(S)

After thawing, the ovaries were subjected to neutral red viability staining to assess the density of viable small follicles and for long-term (48 hours) incubation evaluation of steroid secretion, histology, and apoptosis assay.

RESULT(S)

The follicular viability was decreased in both vitrification groups and in the slow-freezing group with the high concentration of DMSO, as compared with fresh controls. Estradiol levels in the incubation medium followed the same pattern. Light microscopy revealed well-preserved morphology in all groups after 48 hours' incubation. Apoptosis was increased in both vitrified and cryopreserved ovaries.

CONCLUSION(S)

We have developed a new method that can be used in basic studies to improve cryopreservation protocols. Our initial findings suggest that a moderate concentration of the cryoprotectant DMSO is superior to a high DMSO concentration for both vitrification and slow freezing.

Effect of graft site and gonadotrophin treatment on follicular development of canine ovarian grafts transplanted to NOD-SCID mice

PURPOSE

To investigate the effect of graft site and gonadotrophins administration on the number and survival rate of follicles of canine ovarian grafts transplanted to NOD-severe combined immune deficiency (SCID) mice.

METHODS

Fresh ovarian cortex slices obtained from immature bitches were grafted subcutaneously (SC), under kidney capsule (KC) or into ovarian bursa (OB) in NOD-SCID mice. Two months after surgery, the mice allocated into non-treated and treated gonadotrophins groups that injected with porcine follicle stimulating hormone during 7 days and human chorionic gonadotrophin 48 h later. Ovarian grafts were collected after 10 h of last injection and processed for histology.

RESULTS

The number of transitional and preantral follicles under KC and into OB was significantly higher in gonadotrophins-treated mice than those who received saline. Furthermore, the survival rates of primary, transitional and preantral follicles under KC and into OB grafts were significantly higher than those placed SC in the treated gonadotrophins group, and in the non-treated gonadotrophins group; the proportion of primary and preantral follicle survival was significantly higher under KC and into OB than SC grafts.

CONCLUSIONS

In canine ovarian xenografting, administration of gonadotrophin could be effective for improvement of survival of transplanted ovary. Furthermore, the grafting into OB appeared to be better than grafting under KC, which in turn is better than SC.

Genomic sequencing and characterization of cynomolgus macaque cytomegalovirus

Cytomegalovirus (CMV) infection is the most common opportunistic infection in immunosuppressed individuals, such as transplant recipients or people living with HIV/AIDS, and congenital CMV is the leading viral cause of developmental disabilities in infants. Due to the highly species-specific nature of CMV, animal models that closely recapitulate human CMV (HCMV) are of growing importance for vaccine development. Here we present the genomic sequence of a novel nonhuman primate CMV from cynomolgus macaques (Macaca fascicularis; CyCMV). CyCMV (Ottawa strain) was isolated from the urine of a healthy, captive-bred, 4-year-old cynomolgus macaque of Philippine origin, and the viral genome was sequenced using next-generation Illumina sequencing to an average of 516-fold coverage. The CyCMV genome is 218,041 bp in length, with 49.5% G+C content and 84% protein-coding density. We have identified 262 putative open reading frames (ORFs) with an average coding length of 789 bp. The genomic organization of CyCMV is largely colinear with that of rhesus macaque CMV (RhCMV). Of the 262 CyCMV ORFs, 137 are homologous to HCMV genes, 243 are homologous to RhCMV 68.1, and 200 are homologous to RhCMV 180.92. CyCMV encodes four ORFs that are not present in RhCMV strain 68.1 or 180.92 but have homologies with HCMV (UL30, UL74A, UL126, and UL146). Similar to HCMV, CyCMV does not produce the RhCMV-specific viral homologue of cyclooxygenase-2. This newly characterized CMV may provide a novel model in which to study CMV biology and HCMV vaccine development.

Fibrin encapsulation and vascular endothelial growth factor delivery promotes ovarian graft survival in mice

Ovarian cryopreservation before chemotherapy and autotransplantation post-treatment can restore fertility to women with premature ovarian failure. Although the majority of primordial follicles survive the cryopreservation cycle, the follicular pool is reduced after transplantation due to ischemic death. Therefore, we engineered a biomaterial-based system to promote angiogenesis in a mouse model of ovarian transplantation. To mimic the clinical situation of sterility, a bilateral ovariectomy was performed 2 weeks before transplantation, during which time serum levels of follicular stimulating hormone rose to menopausal levels. Before transplantation, vitrified/thawed ovarian tissue from 12-day-old C57Bl/6J pups was encapsulated in fibrin modified with heparin-binding peptide (HBP), heparin, and loaded with 0.5 μg vascular endothelial growth factor (VEGF). The group transplanted with fibrin-HBP-VEGF had twice as many surviving primordial follicles and an increased number of blood vessels relative to the no biomaterial control. Transplanted tissue was viable and supported natural conception that led to live and healthy offspring. The timeline of live births with VEGF delivery suggested that primary follicles survived transplantation, and provided the gametes for the first litter. Thus, VEGF delivery from fibrin supported integration of the transplant with the host, promoted angiogenesis, and enhanced engraftment and function of the tissue.

Orthotopic and heterotopic ovarian tissue transplantation

BACKGROUND

Transplantation of ovarian tissue is, at present, the only clinical option available to restore fertility using cryopreserved ovarian tissue. More than 30 transplantations of cryopreserved tissue have been reported, and six babies have been born, worldwide, following this procedure. Despite these encouraging results, it is essential to optimize the procedure by improving the follicular survival, confirming safety and developing alternatives. Here, we review the different factors affecting follicular survival and growth after grafting.

METHODS

Relevant studies were identified by searching Pubmed up to January 2009 with English language limitation. The following key words were used: (ovarian tissue or whole ovary) AND (transplantation) AND (cryopreservation or pregnancy). Using the literature and personal experience, we examined relevant data on the different exogenous and clinical factors affecting follicular development after grafting.

RESULTS

Clinical factors such as the patient's age and the transplantation sites influenced the lifespan of the graft. A heterotopic transplantation site is not optimal but offers some advantages and it may also promote the hormonal environment after a combined heterotopic and orthotopic transplantation. Exogenous factors such as antioxidants, growth factors or hormones were tested to improve follicular survival; however, their efficiency regarding further follicular development and fertility potential remains to be established.

CONCLUSION

Additional evidence is required to define optimal conditions for ovarian tissue transplantation. Alternatives such as whole ovary or isolated follicles transplantations require further investigation but are likely to be successful in humans in the future.

Ovarian tissue and oocyte cryopreservation

Although currently investigational, ovarian tissue cryopreservation and oocyte cryopreservation hold promise for future female fertility preservation, particularly following aggressive chemotherapy and/or radiotherapy treatment protocols.

Ovary and uterus transplantation

Ovarian and uterine transplantation are procedures gaining more attention again because of potential applications in respectively fertility preservation for cancer and other patients and, more tentatively, women with uterine agenesis or hysterectomy. Cryopreservation of tissue slices, and possibly whole organs, is providing opportunities for banking ovaries for indefinite periods before transplanting them back to restore fertility. The natural plasticity of this organ facilitates grafting to different sites where they can be revascularized and rapidly restore the normal physiology of secretion and ovulation. Ischemic damage is a chief limitation because many follicles are lost, at least in avascular grafts, and functional longevity is reduced. Nevertheless, grafts of young ovarian tissue, even after cryopreservation, can be highly fertile in laboratory rodents and, in humans, autografts have functioned for up to 3 years before needing replacement. Transplantation by vascular anastomosis provides potentially longer function but it is technically much more demanding and riskier for the recipient. It is the only practicable method with the uterus, and has enabled successful pregnancies in several species, but not yet in humans. Contrary to claims made many years ago, neither organ is privileged immunologically, and allografts become rapidly rejected except in hosts whose immune system is deficient or suppressed pharmacologically. All in all, transplantation of these organs, especially the ovary, provides a broad platform of opportunities for research and new applications in reproductive medicine and conservation biology.

Human oocyte and ovarian tissue cryopreservation and its application

PURPOSE

To review the recent progress in human oocyte and ovarian tissue cryopreservation, and in the application of these two technologies for preserving female fertility of patients who are undergoing cancer treatment.

DESIGN

The literature on human oocyte and ovarian tissue freezing was searched with PubMed. The scientific background, current developments and potential future applications of these two methods were reviewed.

RESULTS

Chemotherapy and/or radiotherapy can induce premature ovarian failure in most of female cancer patients. Consequently, there has been a greater need for options to preserve the reproductive potential of these individuals. However, options are somewhat limited currently, particularly following aggressive chemotherapy and/or radiotherapy treatment protocols. In recent years, there have been considerable advances in the cryopreservation of human oocytes and ovarian tissue. For women facing upcoming cancer therapies, cryopreservation of ovarian tissue and oocytes is a technology that holds promise for banking reproductive potential for the future. Recent laboratory modifications have resulted in improved oocyte survival, oocyte fertilization, and pregnancy rates from frozen-thawed oocytes in IVF. This suggests potential for clinical application.

CONCLUSIONS

In the case of patients who are facing infertility due to cancer therapy, oocyte cryopreservation may be one of the few options available. Ovarian tissue cryopreservation can only be recommended as an experimental protocol in carefully selected patients. In ovarian tissue transplantation, more research is needed in order to enhance the revascularization process with the goal of reducing the follicular loss that takes place after tissue grafting. These technologies are still investigational, although tremendous progress has been made. The availability of such treatment will potentially lead to its demand not only from patients with cancer but also from healthy women who chose to postpone childbearing until later in life and therefore wish to retain their fertility.

Therapy Insight: preserving fertility in cyclophosphamide-treated patients with rheumatic disease

Cyclophosphamide remains a necessary treatment for severe rheumatic diseases, despite the continued search for alternative therapies with less gonadal toxicity. The risk of premature gonadal failure and sterility might lead young patients to delay treatment with cyclophosphamide. The patient's age at treatment and the cumulative dose received remain important risk factors for cyclophosphamide-induced gonadal failure in both males and females. Estrogen-containing oral contraceptives for females and testosterone for males are suggested to reduce the gonadal toxicity of cyclophosphamide, although few studies support these interventions. Owing to increased side effects, hormonal therapy is often avoided in patients with edema, hypertension, nephrotic syndrome or antiphospholipid antibodies. Agonists and antagonists of gonadotropin receptors are under study. Gonadotropin-receptor agonists might have beneficial effects in addition to suppression of sex-hormone production. The outcome of attempted cryopreservation of eggs, embryos or ovaries remains uncertain for women seeking to preserve their reproductive potential. Storing male gametes before chemotherapy is widely practiced and technically successful. As recovery of menses or production of testosterone does not predict individual fertility, identification of biomarkers of gonadal function and reserve, including serum levels of several hormones, ultrasonographic measurements of ovarian volume and antral follicle count, are necessary.

Membrane Transport Properties of Equine and Macaque Ovarian Tissues Frozen in Mixtures of Dimethylsulfoxide and Ethylene Glycol

The rate at which equine and macaque ovarian tissue sections are first cooled from +25°Cto+4°C has a significant effect on the measured water transport when the tissues are subsequently frozen in 0.85M solutions of glycerol, dimethylsulfoxide (DMSO), or ethylene glycol (EG). To determine whether the response of ovarian tissues is altered if they are suspended in mixtures of cryoprotective agents (CPAs), rather than in solutions of a single CPA, we have now measured the subzero water transport from ovarian tissues that were suspended in mixtures of DMSO and EG. Sections of freshly collected equine and macaque ovaries were suspended either in a mixture of 0.9M EG plus 0.7M DMSO (equivalent to a mixture of ∼5%v∕v of EG and DMSO) or in a 1.6M solution of only DMSO or only EG. The tissue sections were cooled from +25°Cto+4°C and then frozen to subzero temperatures at 5°C∕min. As the tissues were being frozen, a shape-independent differential scanning calorimeter technique was used to measure water loss from the tissues and, consequently, the best fit membrane permeability parameters (Lpg and ELp) of ovarian tissues during freezing. In the mixture of DMSO+EG, the respective values of Lpg and ELp for equine tissue first cooled at 40°C∕min between +25°C and +4°C before being frozen were 0.15μm∕minatm and 7.6kcal∕mole. The corresponding Lpg and ELp values for equine tissue suspended in 1.6M DMSO were 0.12μm∕minatm and 27.2kcal∕mole; in 1.6M EG, the values were 0.06μm∕minatm and 21.9kcal∕mole, respectively. For macaque ovarian tissues suspended in the mixture of DMSO+EG, the respective values of Lpg and ELp were 0.26μm∕minatm and 26.2kcal∕mole. Similarly, the corresponding LLg and ELp values for macaque tissue suspended in 1.6M DMSO were 0.22μm∕minatm and 31.4kcal∕mole; in 1.6M EG, the values were 0.20μm∕minatm and 27.9kcal∕mole. The parameters for both equine and macaque tissue samples suspended in the DMSO+EG mixture and first cooled at 0.5°C∕min between +25°C and +4°C were very similar to the corresponding values for samples cooled at 40°C∕min. In contrast, the membrane parameters of equine and macaque samples first cooled at 0.5°C∕min in single-component solutions were significantly different from the corresponding values for samples cooled at 40°C∕min. These results show that the membrane properties of ovarian cells from two species are different, and that the membrane properties are significantly affected both by the solution in which the tissue is suspended and by the rate at which the tissue is cooled from +25°Cto+4°C before being frozen. These observations suggest that these variables ought to be considered in the derivation of methods to cryopreserve ovarian tissues.

Ovarian tissue cryostorage and grafting: an option to preserve fertility in pediatric patients with malignancies

Fertility preservation in childhood cancer has become an important area of investigation due to increasing survival rates after cancer therapy. For these patients with an increased risk of infertility and premature ovarian failure, cryopreservation of ovarian tissue is a promising tool to preserve at least part of the reproductive potential. In recent years significant improvements have been achieved in this area, and 2 live births after autografting of frozen-thawed ovarian tissue have been reported. However, further research is needed to assess the clinical effectiveness of ovarian cryopreservation, to optimize the technique, and to limit the risk of reintroducing cancer cells in the patient with the graft.

Harvesting and autotransplantation of vascularized ovarian grafts: approaches and techniques

The objective of this study was to describe the different surgical approaches involved in harvesting and heterotopic autotransplantation of intact ovaries with microvascular anastomosis. Twenty-one synchronized Merino sheep underwent harvesting of their intact ovaries with vascular pedicles. Autotransplantation was performed with fresh (n = 6) and cryopreserved-thawed (C-T; n = 15) ovaries. The ovarian vessels were anastomosed to the deep inferior epigastric vessels using end-to-end (n = 8), end-to-side (n = 6) and fish-mouth modification (n = 7) techniques. Patency of the anastomosis, ischaemia time, hormonal functions and histology were evaluated. In addition, ovarian harvesting techniques in two human subjects were described. Possible autotransplantation sites in humans were suggested. In all, 33.3% (7/21) of all fresh and C-T transplants showed patency after 10 days of follow-up. Patency was observed in 5/8, 2/6 and 0/7 animals using end-to-end, end-to-side and fish-mouth modification for completion of the microvascular anastomosis respectively. Use of the fish mouth modification technique was associated with significantly higher ischaemia time compared with end-to-end (P < 0.01) and end-to-side (P = 0.05) anastomosis. A laparoscopic approach appears to be convenient for ovarian harvesting in humans. The inferior epigastric vessel is probably the most suitable heterotopic vascularizing vessel. End-to-end anastomosis yields the highest patency rate of vascularized grafts.

Ovarian tissue and oocyte cryopreservation

Although currently investigational, ovarian tissue cryopreservation and oocyte cryopreservation hold promise for future female fertility preservation, particularly following aggressive chemotherapy and/or radiotherapy treatment protocols.

Subzero water transport characteristics and optimal rates of freezing rhesus monkey (Macaca mulatta) ovarian tissue

The purpose of the present study was to examine the effect of two different suprazero (room temperature +25 degrees C to +4 degrees C) cooling conditions on the measured water transport response of primate (Macaca mulatta) ovarian tissue in the presence and absence of cryoprotective agents (CPAs). Freshly collected Macaca mulatta (rhesus monkey) ovarian tissue sections were cooled at either 0.5 degrees C/min or 40 degrees C/min from 25 to 4 degrees C. A shape independent differential scanning calorimeter (DSC) technique was then used to measure the volumetric shrinkage during freezing of ovarian tissue sections at a freezing rate of 5 degrees C/min in the presence and absence of three different CPAs (0.85 M glycerol, 0.85 M dimethylsulfoxide, and 0.85 M ethylene glycol). Thus, water transport during freezing of primate ovarian tissue was obtained at eight different conditions (i.e., at four different freezing media with two different suprazero cooling conditions). The water transport response of ovarian tissue cooled rapidly from 25 to 4 degrees C was significantly different (P < 0.01) than that of slow cooled tissue, in the freezing media without CPAs and with dimethylsulfoxide. However, the differences in the measured water transport response due to the imposed suprazero cooling conditions were reduced with the addition of glycerol and ethylene glycol (statistically different with P < 0.05). By fitting a model of water transport to the experimentally obtained volumetric shrinkage data the best-fit membrane permeability parameters (L(pg) and E(Lp)) were determined. The best-fit parameters of water transport in primate ovarian tissue sections ranged from: L(pg) = 0.7 to 0.15 microm/min-atm and E(Lp) = 22.1 to 32.1 kcal/mol (the goodness of fit parameter, R(2) > 0.96). These parameters suggest that the "optimal rates of cryopreservation" for ovarian tissue are significantly dependent upon suprazero cooling conditions and the choice of CPA.

Ovarian tissue cryopreservation and transplantation: a review

The review covers current options for ovarian tissue cryopreservation and transplantation and provides a systematic review of the existing literature from the last 10 years, taking into account all previously published reviews on the subject. The different cryopreservation options available for fertility preservation in cancer patients are embryo cryopreservation, oocyte cryopreservation and ovarian tissue cryopreservation. The choice depends on various parameters: the type and timing of chemotherapy, the type of cancer, the patient's age and the partner status. The different options and their results are discussed, as well as their putative indications and efficacy. The review concludes that advances in reproductive technology have made fertility preservation techniques a real possibility for patients whose gonadal function is threatened by premature menopause, or by treatments such as radiotherapy, chemotherapy or surgical castration.

Preservation of female germ cells from ovaries of cat species

This review provides an overview on recent knowledge on female germ cell population within cat ovaries; on isolation, culture and cryopreservation of feline preantral follicles and on ovarian tissue preservation.

Suprazero cooling conditions significantly influence subzero permeability parameters of mammalian ovarian tissue

To model the cryobiological responses of cells and tissues, permeability characteristics are often measured at suprazero temperatures and the measured values are used to predict the responses at subzero temperatures. The purpose of the present study was to determine whether the rate of cooling from +25 to +4 degrees C influenced the measured water transport response of ovarian tissue at subzero temperatures in the presence or absence of cryoprotective agents (CPAs). Sections of freshly collected equine ovarian tissue were first cooled either at 40 degrees C/min or at 0.5 degrees C/min from 25 to 4 degrees C, and then cooled to subzero temperatures. A shape-independent differential scanning calorimeter (DSC) technique was used to measure the volumetric shrinkage during freezing of equine ovarian tissue sections. After ice was induced to form in the extracellular fluid within the specimen, the sample was frozen from the phase change temperature to -50 degrees C at 5 degrees C/min. Replicate samples were frozen in isotonic medium alone or in medium containing 0.85 M glycerol or 0.85 M dimethylsulfoxide. The water transport response of ovarian tissue samples cooled at 40 degrees C/min from 25 to 4 degrees C was significantly different (confidence level >95%) from that of tissue samples cooled at 0.5 degrees C/min, whether in the presence or absence of CPAs. We fitted a model of water transport to the experimentally-derived volumetric shrinkage data and determined the best-fit membrane permeability parameters (L(pg) and E(Lp)) of equine ovarian tissue during freezing. Subzero water transport parameters of ovarian tissue samples cooled at 0.5 degrees C/min from 25 to 4 degrees C ranged from: L(pg) = 0.06 to 0.73 microm/min.atm and E(Lp) = 6.1 to 20.5 kcal/mol. The corresponding parameters of samples cooled at 40 degrees C/min from 25 to 4 degrees C ranged from: L(pg) = 0.04 to 0.61 microm/min.atm and E(Lp) = 8.2 to 54.2 kcal/mol. Calculations made of the theoretical response of tissue at subzero temperatures suggest that the optimal cooling rates to cryopreserve ovarian tissue are significantly dependent upon suprazero cooling conditions.

Reducing ischaemic damage in rodent ovarian xenografts transplanted into granulation tissue

BACKGROUND

Anti-cancer therapies frequently lead to ovarian damage and impaired fertility. To preserve fertility, cryopreservation and subsequent transplantation of the ovaries have been suggested. One of the challenges in ovarian graft transplantation is overcoming the initial ischaemic damage that depletes a significant fraction of the oocyte pool.

METHODS AND RESULTS

Follicular survival in ovarian grafts was examined by magnetic resonance imaging (MRI) and fluorescence microscopy in a model system in which rat ovaries were transplanted into nude mice. Transplantation into angiogenic granulation tissue created during wound healing shortened the ischaemic period by 24 h and significantly increased the pool of healthy primordial follicles and the perfused area of the transplanted grafts. Functional blood vessels were detected within the grafts as early as 2 days after transplantation. Gain of function was demonstrated both by growth of the grafts and by the hormonal influence on the host uteri.

CONCLUSION

Implantation of ovarian grafts into an angiogenic granulation tissue improved graft vascularization and follicular survival. This procedure/treatment may be used for reducing the ischaemic damage in ovarian transplants, thus prolonging graft functionality and increasing the yield of oocytes that can be easily recovered for fertilization.

Blastocyst development after cryopreservation and subcutaneous transplantation of mouse ovarian tissue

PURPOSE

To investigate follicle survival and developmental potential with IVF of cryopreserved, subcutaneously transplanted mouse ovarian tissue.

METHODS

Fresh and frozen mouse ovarian tissue was autologously transplanted into subcutaneous tissue. Two weeks after the transplantation, the morphology and histology of the fresh and frozen grafts were compared. Superovulation and IVF was performed to evaluate the fertility potential of the frozen ovarian graft.

RESULTS

Both fresh and frozen grafts of ovarian tissue survived in 14 of 16 mice (88%). Morphologically, both types of grafts resembled fresh ovarian tissue and contained follicles at all stages of folliculogenesis. A total of 73% of follicles in fresh grafts and 62% in frozen grafts survived after transplantation compared with fresh ovarian tissue. Sixteen ICR mice underwent superovulation. A total of 56 oocytes from antral follicles were recovered from the subcutaneously transplanted cryopreserved ovarian tissue. Fourteen (25%) oocytes were in metaphase II stage, 6 were fertilized by IVF, and 2 progressed to the blastocyst stage.

CONCLUSIONS

Cryopreservation and subcutaneous transplantation of ovarian tissue provides a possible means of fertility preservation. The main loss of follicles occurred during grafting rather than during freezing and thawing.

Coculture of monkey ovarian tissue increases survival after vitrification and slow-rate freezing

OBJECTIVE

To assess whether coculture of monkey ovarian tissue after low-temperature storage enhances follicular viability. To assess a novel method of vitrifying ovarian tissue.

DESIGN

Prospective in vitro study.

SETTING

University-affiliated national research center.

ANIMAL(S)

Ovaries from 15 cynomolgus or rhesus macaques (1-11 years).

INTERVENTION(S)

Vitrification using a containerless liquid nitrogen emersion system that involves dropping thin cortical pieces suspended in cyroprotectant directly into liquid nitrogen with outcome compared with slow-rate-controlled freezing. Before analysis, some of the thawed tissue was cocultured on mitotically inactivated mouse fetal fibroblast monolayers supplemented with FSH, insulin, transferrin, and selenium.

MAIN OUTCOME MEASURE(S)

Percentage of oocytes viable using live-dead fluorescent staining with carboxyfluorescein diacetate succinimidyl ester and propidium iodide.

RESULT(S)

Postthaw survival rates were 70.4% +/- 4.8% of 1,705 follicles after vitrification and 67.3% +/- 1.9% of 1,895 follicles after slow-rate freeze in six trials with each method. Coculture of the thawed tissue increased the viability, respectively, to 89% +/- 2.1% of 2,833 follicles previously vitrified and to 90.3% +/- 1.9% of 2,109 follicles after a slow-rate freeze (P<.01). Primordial follicles (30- to 50-microm diameter) were the vast majority of surviving follicles after thaw and coculture. Follicular viability in control fresh tissue (eight trials) was 76.0% +/- 4.1%, suggesting negligible loss in follicular viability after cryopreservation.

CONCLUSION(S)

Coculture of thawed ovarian tissue on mouse fetal fibroblasts and FSH increases the percentage of viable follicles. A novel method of vitrifying ovarian tissue is as effective as slow-rate freezing. These approaches may improve graft survival and function when used to treat chemotherapy-induced sterility.

Ovarian tissue and oocyte cryopreservation

Although currently investigational, ovarian tissue cryopreservation and oocyte cryopreservation hold promise for future female fertility preservation, particularly following aggressive chemotherapy and/or radiotherapy treatment protocols.

Human oocyte cryopreservation: a valid alternative to embryo cryopreservation?

Embryo cryopreservation has become an ethical necessity due to the way human in vitro fertilization (IVF) infertility therapy has developed. Limited embryonic implantation has by necessity driven IVF therapy to adopt ways to maximize the harvest of oocytes following ovarian hyperstimulation with its attendant risks. Collection of more oocytes has allowed more embryos to be generated to compensate for poor embryonic viability, often leading to transfer of multiple embryos to increase per transfer pregnancy rates. In an era of improving embryonic viability and prevailing trend toward single embryo transfers, production of excessive numbers of surplus embryos appears increasingly inappropriate. At which stage embryo cryopreservation can be undertaken most effectively remains controversial. Embryo cryopreservation nevertheless represents the current solution to the problem of excessive embryo production, but inherently raises ethical concerns for certain couples uncomfortable with what they might perceive to be "experimental" cryostorage, who in extreme circumstances may even choose to limit the number of oocytes inseminated to obviate the production of spare embryos. On a more practical level, cryostored embryos are co-owned by two people who may separate, and as such the embryos then face an uncertain fate, commonly decided in courts of law. Oocyte cryopreservation, if consistent and successful, offers a way to avoid the above complications of routine IVF therapy. Oocytes may need to be cryostored in the event of unforeseen non-production of sperm during IVF therapy, allowing a more measured consideration of donor sperm use or other means of sperm retrieval. Beyond IVF for infertility therapy using a couple's own gametes, oocyte cryopreservation provides a wonderful opportunity to optimize donor oocyte cryo-banking, reducing costs and improving convenience. Meanwhile, frozen embryo donation is an approach that many couples are uncomfortable with, and allows only for retrospective donor screening, and less gametic choice. Advances in ovarian tissue cryopreservation will probably provide the best approach for long term storage of female gametes for women wishing to elect to prolong their reproductive potential, or prior to cancer therapy. However, improved consistency with vitrification technology through standardization of protocols and cell-carrying systems is bringing routine single oocyte cryostorage, at all stages of egg maturity, closer to reality. This, coupled with in vitro maturation, will aid development of oocyte collection protocols using minimal amounts of gonadotropins. All of which will help drive IVF programs to consider cryostorage of excess oocytes and not embryos, inseminating post-thaw/warming only a limited number of oocytes at any one time, in anticipation of the need for only one or two embryos at transfer. The question then is how close are we to being able to provide routine clinical application of human oocyte cryostorage, and when will it be appropriate?

Live birth after ovarian tissue transplant

Radiation and high-dose chemotherapy may render women with cancer prematurely sterile, a side-effect that would be avoided if ovarian tissue that had been removed before treatment could be made to function afterwards. Live offspring have been produced from transplanted ovarian tissue in mice and sheep but not in monkeys or humans, although sex steroid hormones are still secreted. Here we describe the successful transplantation of fresh ovarian tissue to a different site in a monkey, which has led to the birth of a healthy female after oocyte production, fertilization and transfer to a surrogate mother. The ectopically grafted tissue functions without surgical connection to major blood vessels and sets the stage for the transplantation of cryopreserved ovarian tissue in humans.