Restoration of a normal reproductive lifespan after grafting of cryopreserved mouse ovaries

Cryopreservation Methods and Frontiers in the Art of Freezing Life in Animal Models

The development in cryobiology in animal breeding had revolutionized the field of reproductive medicine. The main objective to preserve animal germplasm stems from variety of reasons such as conservation of endangered animal species, animal diversity, and an increased demand of animal models and/or genetically modified animals for research involving animal and human diseases. Cryopreservation has emerged as promising technique for fertility preservation and assisted reproduction techniques (ART) for production of animal breeds and genetically engineered animal species for research. Slow rate freezing and rapid freezing/vitrification are the two main methods of cryopreservation. Slow freezing is characterized by the phase transition (liquid turning into solid) when reducing the temperature below freezing point. Vitrification, on the other hand, is a phenomenon in which liquid solidifies without the formation of ice crystals, thus the process is referred to as a glass transition or ice-free cryopreservation. The vitrification protocol applies high concentrations of cryoprotective agents (CPA) used to avoid cryoinjury. This chapter provides a brief overview of fundamentals of cryopreservation and established methods adopted in cryopreservation. Strategies involved in cryopreserving germ cells (sperm and egg freezing) are included in this chapter. Last section describes the frontiers and advancement of cryopreservation in some of the important animal models like rodents (mouse and rats) and in few large animals (sheep, cow etc).

Folliculogenesis-Associated Genes Expression in Human Vitrified Ovarian Tissue after Xenotransplantation in γ-Irradiated Mice

Objective

Autograft transplantation of vitrified cortical ovarian tissue is an acceptable clinical technique for fertility preservation in women. Xenograft transplantation into animal models could be useful for evaluating the safety of human vitrified ovarian tissue. This study targeted to evaluate impact of vitrification on expression of the genes associated with folliculogenesis after xenograft transplantation of human vitrified ovarian tissue to γ-irradiated mice.

Materials and Methods

In this experimental study, ovarian biopsies were gathered from six transsexual persons. The cortical section of ovarian biopsies was separated and chopped into small pieces. These pieces were randomly divided into vitrified and non-vitrified groups. In each group some pieces were considered as non-transplanted tissues and the others were transplanted to γ-irradiated female National Medical Research Institute (NMRI) mice. Before and after two weeks of xenograft transplantation, histological assessment and evaluation of the expression of folliculogenesis- associated genes (FIGLA, GDF-9, KL and FSHR) were performed in both vitrified and non-vitrified groups.

Results

Percentage of the normal follicles and expression of the all examined genes from transplanted and non- transplanted tissue were similar in both vitrified and non-vitrified groups (P>0.05). After transplantation, the normal follicle rate was significantly decreased and among the folliculogenesis-associated genes, expression of GDF-9 gene was significantly increased, rather than before transplantation in vitrified and non-vitrified tissues (P<0.05).

Conclusion

The vitrification method using dimethyl solphoxide and ethylene glycol (EG) had no remarkable effect on the normal follicular rate and expression of folliculogenesis-associated genes after two weeks human ovarian tissue xenografting. In addition, transplantation process can cause a significant decrease in normal follicular rate and expression of GDF-9 gene.

Influence of graft size, histocompatibility,and cryopreservation on reproductive outcome following ovary transplantation in mice

Purpose

Transplantation of ovarian tissue is a valuable method to rescue mouse strains with fertility problems and to revitalize archived strains. The purpose of this study was to investigate the effect of (i) different sizes of transplanted ovary pieces on reproductive outcome, (ii) use of immunodeficient recipients to overcome the limitation of histocompatibility, and (iii) to compare different protocols for cryopreservation of ovarian tissue.

Methods

Halves, quarters, and eights of mouse ovaries were transplanted. Half ovaries from B6 donors were transferred into immunodeficient mice. Halves of ovaries were frozen according to four different protocols, thawed and transferred.

Results

Pregnancy rate after transplantation of ovarian tissue was high (90–100%) independent of the transplant size. Although, the average litter size was significantly lower for recipients of quarters and eights (4.4 and 4.6 vs. 6.5), the total number of offspring produced per donor ovary was higher compared with recipients of halves. Pregnancy rate of immunodeficient recipients was 40% (mean 4.7 offspring per litter). All four cryopreservation protocols used were able to preserve functionality of the ovarian tissue.

Conclusions

Transplantation of ovarian tissue smaller than halves resulted in reduced litter sizes. The distribution of ovarian tissue of one donor female to 4 or 8 recipients will therefore yield in a higher total number of offspring in a certain time period. The use of immunodeficient recipients is an option for non-histocompatible donors. Cryopreservation of ovarian tissue is generally feasible but the function of frozen-thawed ovary halves after transplantation differs depending on the freezing protocol used.

The transgenerational effects of oocyte mitochondrial supplementation

Many women suffer from either failed fertilisation or their embryos arrest early during development. Autologous mitochondrial supplementation has been proposed as an assisted reproductive technology to overcome these problems. However, its safety remains to be tested in an animal model to determine if there are transgenerational effects. We have supplemented oocytes with autologous populations of mitochondria to generate founders. We mated the female founders and their offspring to produce three generations. We assessed litter size, the ovarian reserve, and weight gain and conducted a full histopathological analysis from each of the three generations. Across the generations, we observed significant increases in litter size and in the number of primordial follicles in the ovary matched by changes in global gene expression patterns for these early-stage oocytes. However, full histopathological analysis revealed that cardiac structure was compromised in first and second generation offspring, which could seriously affect the health of the offspring. Furthermore, the offspring were prone to increased weight gain during early life. Mitochondrial supplementation appears to perturb the regulation of the chromosomal genome resulting in transgenerational phenotypic gains and losses. These data highlight the need for caution when using autologous mitochondrial supplementation to treat female factor infertility.

Cryopreservation and transplantation of ovarian tissue: results from one center in the USA

Purpose

To report the results of cryopreserved ovary tissue transplantation for leukemia and other cancers, in a single US center.

Methods

One hundred eight females between age 6 and (median age 24) 35 were referred for possible ovary tissue cryopreservation over a 20-year period, with either slow freeze or vitrification. Thus far 13 patients returned up to 18 years later to have their tissue transplanted back.

Results

All 13 patients had return of ovarian function 5 months post transplant with regular menstrual cycling. AMH rose to very high levels as the FSH declined to normal. Four months later, the AMH again declined to very low levels. Nonetheless, the grafts remained functional for up to 5 years or longer. Ten of the 13 (77%) became spontaneously pregnant at least once, resulting in 13 healthy babies. A total of 24 healthy babies have been born 11 from fresh transplanted ovarian tissue and 13 from cryopreserved transplanted ovarian tissue.

Conclusions

(1) Ovary tissue cryopreservation is a robust method for preserving a woman’s fertility. (2) Cortical tissue pressure may be a key regulator of primordial follicle arrest, recruitment, and ovarian longevity. (3) This is the only such series yet reported in the USA.

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.

Extragonadal oocytes residing in the mouse ovarian hilum contribute to fertility

The observation of pups born from recipient and donor mice after ovariectomy followed by ovarian transplant poses the interesting possibility of an extraovarian source of oocytes. However, whether mammalian adult oocytes reside in extragonadal tissues remains elusive. Using transgenic fluorescent reporter mice and transplantation surgeries, we demonstrate the presence of both donor- and recipient-derived corpora lutea and recovery of both donor- and recipient-derived offspring from ovariectomized mice after transplantation of donor ovaries. A potential region for extraovarian oocytes is the hilum, a ligament-like structure between the ovary and the reproductive tract. Immunofluorescent confocal microscopy of mouse ovaries and reproductive tracts revealed that a population of primordial follicles resides outside the ovary within the hilum. Ovariectomy-only controls confirmed that oocytes remain in the recipient hilum after surgery. These results provide evidence that the hilum is a reserve source of follicles, which likely return to the ovary for maturation and ovulation. By identifying a new follicle reservoir, our study addresses a long-standing question in reproductive biology and contributes to new conceptual knowledge about ovarian function and fertility.

Ovarian tissue cryopreservation and transplantation: scientific implications

After fresh or frozen ovary transplantation, FSH levels return to normal, and menstrual cycles resume by 150 days, coincident with anti-Müllerian hormone rising to higher than normal levels. AMH then returns to well below normal levels by 240 days, remaining as such for many years with nonetheless normal ovulation and fertility. To date, 20 babies have been born in our program from 11 fresh and 13 cryopreserved ovary transplant recipients with a live baby rate of over 70 % (11 babies from fresh and 9 from frozen). Globally, over 70 live births have been reported for both fresh and frozen ovary transplants with an approximate 30 % live birth rate. Given the rapid rise of AMH after the fall of FSH, with a subsequent AMH decrease with retention of ovarian function, it is tempting to speculate the existence of a shared mechanism controlling primordial follicle recruitment, fetal oocyte meiotic arrest, and recruitment in the adult ovary. With the massive recruitment of primordial follicles observed after human ovarian cortical tissue transplantation, which subsides to an extremely low recruitment rate, we will discuss how this phenomenon suggests a unifying theory implicating ovarian cortical tissue rigidity in the regulation of both fetal oocyte arrest and recruitment of follicles in the adult ovary. As the paper by Winkler-Crepaz et al. in this issue demonstrates, our in vivo results are consistent with the in vitro demonstration that primordial follicles in the fetal cortex are "locked" in development, resulting in meiotic arrest, which spares the oocytes from being rapidly lost all at once (Winkler-Crepaz et al., J Assist Reprod Genet, 1). Winkler-Crepaz et al. demonstrate that follicle loss after ovarian cortex transplantation is unlikely due to ischemic apoptosis, but rather from a "burst" of primordial follicle recruitment. In vivo, primordial follicles are normally resistant to further development or activation to prevent oocyte depletion. The dense fibrous ovarian cortex, through as yet unresolved mechanisms, arrests the further continuation of meiosis and also prevents a sudden depletion of all resting follicles in the adult ovary. Intrinsic tissue pressure is released after cortical tissue transplantation, temporarily resulting in a rapid follicle depletion. These results are consistent with the observation that once the ovarian reserve is reduced in the graft, the rate of recruitment diminishes and the ovarian tissue exhibits a relatively long duration of function.

Maternal and fetal roles in bacterially induced preterm labor in the mouse

BACKGROUND

The relative roles of the mother and fetus in signaling for labor remain poorly understood.

OBJECTIVE

We previously demonstrated using gene knockout (KO) mice that Escherichia coli-induced preterm delivery is completely dependent on MyD88, a toll-like receptor adaptor protein. Here we leveraged this finding to conduct a genetic experiment testing whether the mother, the fetus, or both signal for parturition in bacterially induced labor.

STUDY DESIGN

Six different maternal/fetal genotype combinations for MyD88 were studied: wild-type (WT) dams carrying one of the following: (1) WT or (2) MyD88 heterozygous (het) fetuses (generated by mating WT females with WT or MyD88-knockout [KO] males, respectively); (3) WT dams carrying MyD88-KO fetuses (generated by replacing the ovaries of WT females with MyD88-KO ovaries, followed by mating with MyD88-KO males); a similar strategy was used to generate MyD88-KO dams carrying (4) MyD88-KO, (5) MyD88 het, or (6) WT fetuses. On day 14.5 of gestation, mice received intrauterine injections of either 1 × 10(9) killed E coli or sterile medium. Delivery of ≥ 1 fetus within 48 hours was considered preterm. A separate group of similarly treated pregnant mice was euthanized 5 hours after surgery for gene expression and tissue analysis.

RESULTS

E coli-induced preterm delivery is dependent on maternal and not fetal genotype: > 95% of WT and < 5% of MyD88-KO dams deliver prematurely, regardless of fetal genotype (P = .0001). In contrast, fetal survival in utero is influenced by fetal genotype: in MyD88-KO dams, in which premature birth rarely occurs, only 81% of WT and 86% of MyD88-heterozygous fetuses were alive 48 hours after surgery compared with 100% of MyD88-KO fetuses (P < .01). Messenger ribonucleic acids for the inflammatory mediators interleukin-1β, tumor necrosis factor, interleukin-6, and cyclooxygenase-2 were elevated in uterine tissues only in WT mothers treated with E coli and were low or undetectable in the uteri of KO mothers or in animals treated with saline. Serum progesterone levels were lower in KO mothers with WT ovaries than in WT mothers with KO ovaries, but bacterial exposure did not have an impact on these levels.

CONCLUSION

In the murine E coli-induced labor model, preterm delivery and uterine expression of inflammatory mediators is determined by the mother and not the fetus and is not attributable to a decline in serum progesterone.

Orthotopic transplantation of cryopreserved mouse ovaries and gonadotrophin releasing hormone analogues in the restoration of function following chemotherapy-induced ovarian damage

Therapy advances are constantly improving survival rates of cancer patients, however the toxic effects of chemotherapy drugs can seriously affect patients' quality of life. In women, fertility and premature ovarian endocrine dysfunction are of particular concern. It is urgently we find methods to preserve or reconstruct ovarian function for these women. This study compares GnRHa treatment with ovarian tissue cryopreservation and orthotopic transplantation in a chemotherapy-induced ovarian damage murine model. 56 inbred Lewis rats were divided into 4 treatment groups: Saline control (group I); cyclophosphamide only (group II); cyclophosphamide plus GnRHa (group III); cyclophosphamide and grafting of thawed cryopreserved ovaries (group IV). Body weight, estrous cycle recovery time, ovarian weight, morphology and follicle count, as well as breeding and fertility were compared among groups. Only group IV was able to restore to normal body weight by the end of the observation period and resumed normal estrous cycles in a shorter time compared to other treatment groups. There was a decrease in primordial follicles in all treatment groups, but group III had the greatest reduction. Although, there was no difference in pregnancy, only one animal littered normal pups in group II, none littered in group III and four littered in group IV. Thus, cryopreservation and orthotopic transplantation of ovarian tissue can restore the fertility of rats subjected to chemotherapy in a manner that is superior to GnRHa treatment. We also observed increased rates of hepatic, splenic and pulmonary haemorrhage in group III, suggesting there may be synergistic toxicity of GnRHa and cyclophosphamide.

Fertility preservation for age-related fertility decline

Cryopreservation of eggs or ovarian tissue to preserve fertility for patients with cancer has been studied since 1994 with R G Gosden's paper describing restoration of fertility in oophorectomised sheep, and for decades previously by others in smaller mammals. Clinically this approach has shown great success. Many healthy children have been born from eggs cryopreserved with the Kuwayama egg vitrification technique for non-medical (social) indications, but until now very few patients with cancer have achieved pregnancy with cryopreserved eggs. Often, oncologists do not wish to delay cancer treatment while the patient goes through multiple ovarian stimulation cycles to retrieve eggs, and the patient can only start using the oocytes after full recovery from cancer. Ovarian stimulation and egg retrieval is not a barrier for patients without cancer who wish to delay childbearing, which makes oocyte cryopreservation increasingly popular to overcome an age-related decline in fertility. Cryopreservation of ovarian tissue is an option if egg cryopreservation is ruled out. More than 35 babies have been born so far with cryopreserved ovarian tissue in patients with cancer who have had a complete return of hormonal function, and fertility to baseline. Both egg and ovarian tissue cryopreservation might be ready for application to the preservation of fertility not only in patients with cancer but also in countering the increasing incidence of age-related decline in female fertility.

Loss of BMAL1 in ovarian steroidogenic cells results in implantation failure in female mice

The circadian clock plays a significant role in many aspects of female reproductive biology, including estrous cycling, ovulation, embryonic implantation, onset of puberty, and parturition. In an effort to link cell-specific circadian clocks to their specific roles in female reproduction, we used the promoter that controls expression of Steroidogenic Factor-1 (SF1) to drive Cre-recombinase-mediated deletion of the brain muscle arnt-like 1 (Bmal1) gene, known to encode an essential component of the circadian clock (SF1-Bmal1(-/-)). The resultant SF1-Bmal1(-/-) females display embryonic implantation failure, which is rescued by progesterone supplementation, or bilateral or unilateral transplantation of wild-type ovaries into SF1-Bmal1(-/-) dams. The observation that the central clock, and many other peripheral clocks, are fully functional in this model allows the assignment of the implantation phenotype to the clock in ovarian steroidogenic cells and distinguishes it from more general circadian related systemic pathology (e.g., early onset arthropathy, premature aging, ovulation, late onset of puberty, and abnormal estrous cycle). Our ovarian transcriptome analysis reveals that deletion of ovarian Bmal1 disrupts expression of transcripts associated with the circadian machinery and also genes critical for regulation of progesterone production, such as steroidogenic acute regulatory factor (Star). Overall, these data provide a powerful model to probe the interlocking and synergistic network of the circadian clock and reproductive systems.

Viability of human ovarian tissue confirmed 5 years after freezing with spontaneous ice-formation by autografting and chorio-allantoic membrane culture

To achieve optimal and uniform outcomes, slow cooling protocols for human ovarian tissues generally initiate ice formation at high sub-zero temperatures (-6 to -9 °C). The aim of the study was to investigate the function of ovarian tissue that had unintentionally self seeded at -20 °C during the freezing step, by examining its development following chicken embryonic chorioallantoic membrane (CAM) grafting and after transplantation back to the patient. Ovarian tissue was frozen in 6% (v/v) dimethyl sulfoxide, 6% (v/v) ethylene glycol and 0.15M sucrose which had self-seeded at -20 °C. Five years after cryopreservation, 8 pieces were thawed and transplanted back to the patient. Two small (1 × 2 × 1 mm) pieces of this thawed tissue were cultured in a CAM-system for 5 days to assess the tissue viability. The autografted ovarian tissue re-established spontaneous menstrual bleeding within five months and raised serum 17-β Estradiol from 19 to 330 pg/ml. Ultrasound revealed a dominant follicle at the site of the transplanted tissue in the follicular phase after the menstrual bleed. Analysis of the CAM cultured tissue established that 88% of the primordial follicles are degenerated and there was limited in growth of blood vessels. In conclusion, in spite of the damage caused by the cryopreservation with spontaneous ice-formation the viability could be confirmed by CAM culture and the restoration of ovarian function after auto-transplantation.

Restoring fertility after ovarian tissue cryopreservation: a half century of research

Tissue transplantation and in vitro ovarian follicle culture have been investigated as alternative techniques to restore fertility in young women who are facing fertility-threatening diseases or treatments following ovarian tissue cryopreservation. Although transplants of fresh or frozen ovarian tissue have successfully yielded healthy live births in different species including humans, the risks of reintroducing cancer cells back into the patient, post treatment, have limited its clinical purpose. The in vitro ovarian follicle culture minimizes these risks and provides a way to harvest more mature oocytes, however its clinical translation has yet to be determined. Not only is it possible for tissue cryopreservation to safeguard fertility in cancer patients, this technique also allows the maintenance of germplasm banks for animals of high commercial value or for those animals that are at risk of extinction. Given the importance of managing female genetic material, this paper reviews the progress of the methods used to preserve and restore female fertility in different species to demonstrate the results obtained in the past 50 years of research, the current achievements and the future directions on this field.

Underuse of ovarian transposition in reproductive-aged cancer patients treated by primary or adjuvant pelvic irradiation

AIM

To investigate the application status of ovarian transposition (OT) in reproductive-aged cancer patients undergoing radiation therapy.

MATERIAL & METHODS

Between November 1999 and December 2008, 2524 patients had received pelvic irradiation at Seoul National University Hospital. We filtered the patients with the indications of (i) within 12 to 40 years of age, and (ii) receiving primary or adjuvant pelvic irradiation. There were 241 patients within 12 to 40 years of age. After excluding 133 patients with metastatic disease or under palliative radiation treatment, 108 patients were discovered appropriate for OT. We analyzed the application status of OT, surgical types of OT, cancer types and radiation types in those 108 patients.

RESULTS

Cervical cancer was the major indication (n = 68, 62.9%). Another 37.1% of indicated disease were composed of rectal cancer (n = 19), vulvo-vaginal cancer (n = 4), non-Hodgkin's lymphoma (n = 3), and other pelvic tumors (n = 14). Among the 108 patients, only 31 (28.7%) patients had received OT before pelvic irradiation. Most of the operations were applied on cervical cancer patients (n = 29) and only two procedures on rectal and endometrial cancer, respectively. OT had been mostly performed during laparotomy. Laparoscopic procedure was applied in only one case with advanced cervical cancer.

CONCLUSIONS

Although OT could be a preventive measure of premature ovarian failure from radiation therapy, this procedure has been considerably underused at our institution. This procedure should be applied more widely to preserve the fertility and improve the quality of life in reproductive-aged cancer patients.

Granulocyte colony-stimulating factor in conjunction with vascular endothelial growth factor maintains primordial follicle numbers in transplanted mouse ovaries

OBJECTIVE

To determine whether granulocyte colony-stimulating factor (G-CSF), stem cell factor (SCF), or vascular endothelial growth factor (VEGF) improve the outcome of ovarian grafting.

DESIGN

Experimental animal study.

SETTING

Tertiary care hospital, animal facilities.

ANIMAL(S)

Young adult (6- to 8-week-old) C57BL/6 female mice.

INTERVENTION(S)

Orthotopic transplantation of the frozen-thawed ovary. Group 1 (n = 6) received VEGF (8 g/kg/day); group 2 (n = 6) received VEGF and G-CSF (50 g/kg/day), group 3 (n = 6) received G-CSF and SCF (100 g/kg/day), and group 4 (n = 5) received saline (vehicle controls). All injections were given once daily for 5 days starting the day after surgery. Ovaries were collected 2 weeks after transplantation.

MAIN OUTCOME MEASURE(S)

Number of nonatretic immature (primordial, primary, and small preantral) follicles.

RESULT(S)

Transplanted ovaries in mice injected with VEGF concurrently with G-CSF maintained a statistically significantly larger pool of primordial follicles compared with transplanted ovaries in saline-injected controls. Follicle numbers (total immature and primordial) in transplanted ovaries showed no statistically significant difference in mice injected with VEGF alone or G-CSF plus SCF compared with saline-injected controls.

CONCLUSION(S)

After ovarian transplantation, mice treated with VEGF and G-CSF maintain a significantly greater number of primordial follicles compared with the transplanted ovaries in control animals, suggesting that the combination of G-CSF and VEGF minimizes ischemic damage and thus improves the viability and function of the ovarian graft.

Assessment of follicular development in cryopreserved primate ovarian tissue by xenografting: prepubertal tissues are less sensitive to the choice of cryoprotectant

Improvements in cancer survival rates have renewed interest in the cryopreservation of ovarian tissue for fertility preservation. We used the marmoset as a non-human primate model to assess the effect of different cryoprotectives on follicular viability of prepubertal compared to adult ovarian tissue following xenografting. Cryopreservation was performed with dimethylsulfoxide (DMSO), 1,2-propanediol (PrOH), or ethylene glycol (EG) using a slow freezing protocol. Subsequently, nude mice received eight grafts per animal from the DMSO and the PrOH groups for a 4-week grafting period. Fresh, cryopreserved-thawed, and xenografted tissues were serially sectioned and evaluated for the number and morphology of follicles. In adult tissue, the percentage of morphologically normal primordial follicles significantly decreased from 41.2 ± 4.5% (fresh) to 13.6 ± 1.8 (DMSO), 9.5 ± 1.7 (PrOH), or 6.8 ± 1.0 (EG) following cryopreservation. After xenografting, the percentage of morphologically normal primordial (26.2 ± 2.5%) and primary follicles (28.1 ± 5.4%) in the DMSO group was significantly higher than that in the PrOH group (12.2 ± 3 and 5.4 ± 2.1% respectively). Proliferating cell nuclear antigen (PCNA) staining suggests the resumption of proliferative activity in all cellular compartments. In prepubertal tissues, primordial but not primary follicles display a similar sensitivity to cryopreservation, and no significant differences between DMSO and PrOH following xenografting were observed. In conclusion, DMSO shows a superior protective effect on follicular morphology compared with PrOH and EG in cryopreserved tissues. Xenografting has confirmed better efficacy of DMSO versus PrOH in adult but not in prepubertal tissues, probably owing to a greater capacity of younger animals to compensate for cryoinjury.

Effectiveness of slow freezing and vitrification for long-term preservation of mouse ovarian tissue

This study was conducted to evaluate the interaction between cryo-damage and ART outcome after cryopreservation of mouse ovarian tissues with different methods. Either a vitrification or a slow freezing was employed for the cryopreservation of B6CBAF1 mouse ovaries and follicle growth and the preimplantation development of intrafollicular oocytes following parthenogenesis or IVF were monitored. Both cryopreservation protocols caused significant damage to follicle components, including vacuole formation and mitochondrial deformities. Regardless of the cryopreservation protocols employed, a sharp (P < 0.0001) decrease in follicle viability and post-thaw growth was detected. When IVF program was employed, significant (P < 0.05) decrease in cleavage and blastocyst formation was notable in both modes of cryopreservation. However, such retardation was not found when oocytes were parthenogenetically activated. In the IVF oocytes, slow freezing led to better development than vitrification. In conclusion, a close relationship between cryopreservation and ART methods should be considered for the selection of cryopreservation program.

Whole sheep ovary cryopreservation: evaluation of a slow freezing protocol with dimethylsulphoxide

PURPOSE

To evaluate a slow freezing method for whole ovary cryopreservation by evaluating effects of added cryoprotectant.

METHODS

Sheep ovaries were isolated during surgery, flushed with either Ringer-Acetate or dimethylsulphoxide and cryopreserved by slow freezing. After rapid thawing, viability was assessed by ovarian in vitro perfusion, cell culture, histology and fluorescent live-dead assay.

RESULTS

Production of cyclic AMP and progesterone was slightly higher in the dimethylsulphoxide group. Cultured ovarian cells from dimethylsulphoxide-preserved ovaries secreted larger amounts of progesterone than cells from Ringer-Acetate preserved. Light microscopy of ovarian biopsies obtained after perfusion, revealed well-preserved tissue in the dimethysulphoxide group but not in the Ringer-Acetate group. The density of small follicles and ovarian cell viability were higher in dimethysulphoxide ovaries compared to Ringer-Acetate ovaries.

CONCLUSIONS

Equilibrium with its protective effect can be achieved by slow freezing protocol, with an additional protective effect by the presence of dimethylsulphoxide.

Follicle growth and oocyte development after ovary transplantation into back muscle of immune-intact adult castrated male mice

Ovary grafting is not only a method of investigating follicle and oocyte development, but also a useful model to explore the possibility of the re-establishment of the reproductive axis in male-to-female sexual reversal. This study investigated ovary survival and follicle development after mouse ovaries were transplanted into immune-intact castrated male mice. Ten-day-old mouse ovaries were transplanted into the back muscle of adult outbred castrated male mice treated with immunosuppressants. Twenty-two days later, the ovary structure and the number of follicles present was examined by hematoxylin and eosin staining. The oocytes were harvested, and then used for in vitro maturation (IVM) and IVF. The results showed that primordial and antral follicles were mainly found in the grafts, and there were obvious differences compared with 32-day-old fresh ovaries (P<0.05). Embryos were derived from collected oocytes after IVM and IVF with a 72.4% cleavage rate and 7.9% blastocyst rate; 12 live pups were generated by embryo transfer. The hormone assay showed that plasma concentrations of both estrogen and progesterone increased after ovarian transplantation (P<0.01). In conclusion, immune-intact adult castrated male mice can support ovary survival and further development of follicles with endocrine function after ovarian transplantation.

Duration of fertility after fresh and frozen ovary transplantation

OBJECTIVE

To evaluate the function of human ovarian transplants.

DESIGN

Follow a series of fresh ovarian transplants for up to 5 years, and compare fresh and frozen ovarian tissue transplantation.

SETTING

Tertiary referral community hospital.

PATIENT(S)

Nine women with premature ovarian failure who received an ovary donated from a monozygotic twin sibling, and 16 young cancer patients undergoing ovarian cryopreservation. Two of the transplant recipients were cancer survivors rendered sterile by their therapy.

INTERVENTION(S)

Fresh ovary transplantation between monozygotic twin sisters, as well as transplantation of previously frozen ovarian tissue, and study of cryopreserved tissue in cancer patients.

MAIN OUTCOME MEASURE(S)

Return of normal menstrual cycling, hormone levels, pregnancy, healthy babies, duration of transplant function, and ovarian tissue evaluation.

RESULT(S)

Normal serum FSH and regular menstrual cycles returned by 5 months after surgery in all cases, both fresh and frozen. Fourteen spontaneous pregnancies were established leading to eight healthy live births and two healthy ongoing conceptions. All three frozen tissue transplants conceived spontaneously, one delivered, and two were ongoing. Oocyte survival with slow freezing was 42% and after vitrification 89%.

CONCLUSION(S)

Ovarian transplantation in humans is a robust procedure, even after cryopreservation, and vitrification might prove to be more effective than slow freezing.

Strategies and considerations for distributing and recovering mouse lines

As more and more genetically modified mouse lines are being generated, it becomes increasingly common to share animal models among different research institutions. Live mice are routinely transferred between animal facilities. Due to various issues concerning animal welfare, intellectual property rights, colony health status and biohazard, significant paperwork and coordination are required before any animal travel can take place. Shipping fresh or frozen preimplantation embryos, gametes, or reproductive organs can bypass some of the issues associated with live animal transfer, but it requires the receiving facilities to be able to perform delicate and sometimes intricate procedures such as embryo transfer, in vitro fertilization (IVF), or ovary transplantation. Here, we summarize the general requirements for live animal transport and review some of the assisted reproductive technologies (ART) that can be applied to shipping and reviving mouse lines. Intended users of these methods should consult their institution's responsible official to find out whether each specific method is legal or appropriate in their own animal facilities.

Biological methods for archiving and maintaining mutant laboratory mice. Part I: conserving mutant strains

The mouse is now firmly established as the model organism of choice for scientists studying mammalian biology and human disease. Consequently, a plethora of novel, genetically altered (GA) mouse lines have been created. In addition, the output from the large scale mutagenesis programmes currently under way around the world will increase the collection of GA mouse strains still further. Because of the implications for animal welfare and the constraints on resources, it would be unreasonable to expect anything other than those strains essential for ongoing research programmes to be maintained as breeding colonies. Unfortunately, unless the redundant strains are preserved using robust procedures, which guarantee their recovery, they will be lost to future generations of researchers.This chapter describes some of the preservation methods currently used in laboratories around the world to archive novel mouse strains.

Live offspring from vitrified blastocysts derived from fresh and cryopreserved ovarian tissue grafts of adult mice

Ovarian tissue cryopreservation and transplantation can be used to preserve fertility for cancer patients. In this study, we assessed the viability and function of ovarian tissue from adult mice that was cryopreserved by solid surface vitrification or traditional slow-cooling using variousin vitroandin vivotechniques, including allotransplantation,in vitrooocyte maturation, embryo culturein vitro, blastocyst cryopreservation, embryo transfer, and development. The importance of cumulus cells for oocyte maturation, fertilization, and embryo development was investigated. Graft recovery, follicle survival, and oocyte retrieval was similar in control, vitrified, and slow-cooled groups. High rates of oocyte maturation, cleavage, and blastocyst formation were achieved, with no significant differences between the control, vitrified or slow-cooled ovarian tissue grafts. The presence of cumulus cells was important for oocyte maturation, fertilization, and subsequent development. Cumulus–oocyte complexes with no surrounding cumulus cells (N-COCs) or with an incomplete layer (P-COCs) had significantly lower rates of oocyte maturation and blastocyst formation than cumulus–oocyte complexes with at least one complete layer of cumulus cells (F-COCs; maturation rate: 63, 78 vs 94%; blastocyst rate: 29, 49 vs 80%). Live births were achieved using vitrified blastocysts derived from oocytes taken from vitrified and slow-cooled ovarian tissue heterotypic allografts. Successful production of healthy offspring from these vitrified blastocysts suggests that this technique should be considered as a useful stage to pause in the assisted reproduction pathway. This provides an alternative protocol for restoring fertility and offering cancer patients a better indication of their chances of pregnancy and live birth.

Cryopreserved ovarian tissues can maintain a long-term function after heterotopic autotransplantation in rat

The functional longevity of cryopreserved ovarian grafts is one of the most challenging questions regarding ovarian transplantation at present. This study used a rat ovarian grafting model to investigate whether ovarian tissues from adult rats, which had been cryopreserved by vitrification and followed by heterotopic transplantation, could establish long-term hormone secretion and follicle development. Fresh and cryopreserved ovarian tissues were autologously transplanted under the kidney capsule. One-third of the animals in each group (sham-operated, fresh autografts, cryopreserved autografts, or castrated) were killed 5, 8, or 10 months after transplantation. Vaginal cytology, serum estradiol (E2), progesterone, and the morphology of the reproductive tract were used to assess ovarian function. Both fresh and cryopreserved ovarian grafts survived well in all the animal models with comparable proportion of follicles at each stage of folliculogenesis at all three time points. The serum E2 and progesterone concentrations in the groups with fresh or cryopreserved grafts remained comparable with those in sham-operated controls at all investigated time points. However, a loss of grafts and primordial follicles following heterotopic transplantation was noted. In conclusion, the heterotopic autotransplantation of vitrified ovarian tissues from adult rat without vascular anastomosis can maintain long-term ovarian function and exert endocrine function in target organs, in spite of the reduction in follicle pool.

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

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

Ovarian endocrine profile and long-term vascular patency following heterotopic autotransplantation of cryopreserved whole ovine ovaries

BACKGROUND

This study examined the ability of cryopreserved whole ovine ovaries to resume function in vivo following autotransplantation.

METHODS

Swaledale ewes had their left ovaries removed and either perfused but not cryopreserved (n = 4; control), or perfused and cryopreserved (n = 8; cryopreserved) before autotransplantation sub-cutaneously to the neck by microvascular anastomosis. Right ovaries were removed and fixed as non-grafted controls. Weekly jugular venous blood samples were analysed for plasma FSH, LH, inhibin A and progesterone levels, grafts were scanned transdermally and oestrus was detected. Vascular patency was assessed post-mortem and follicle populations were measured in recovered tissue.

RESULTS

Immediate vascular patency was achieved in all ewes and maintained in 7/8 cryopreserved and 3/4 control grafts. Functional corpora lutea were identified in three ewes (one control; two cryopreserved) 18-25 weeks after grafting. Inhibin A levels indicated resumption of follicular development in four cryopreserved and one control ewes, however, castrate gonadotrophin levels persisted in five cryopreserved and two control ewes. Primordial follicle density was reduced following grafting in both cryopreserved and non-frozen ovaries (P < 0.001).

CONCLUSIONS

In conclusion, these results demonstrate successful partial restoration of ovarian function following cryopreservation of the whole ovary and vascular pedicle in a large monovulatory species. The inability to restore full ovarian function was related to loss of primordial follicles rather than vascular patency in both frozen and fresh tissue, suggesting that factors associated with cannulation and perfusion may contribute to this depletion. Further work is therefore needed to elucidate these factors before the procedure could be considered a viable option for fertility preservation.

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.

Orthotopic transplantation of neonatal GFP rat ovary as experimental model to study ovarian development and toxicology

The rat is one of the most commonly used experimental animal species in biomedical research. The availability of new research tools in rats could therefore provide considerable advances in the areas where this mammal is extensively used. We report the development of a new green fluorescent protein (GFP) rat strain suitable for organ transplantation and the birth of GFP rats following orthotopic transplantation of neonatal ovaries from this newly developed GFP rat strain to a wild-type Fischer 344 (F344) strain. A new GFP rat strain was developed by backcrossing eGFP Sprague-Dawley (SD-Tg(CAG-EGFP)Cz-004Osb) to wild-type F344 for eight generations. Whole ovaries from postnatal day (PND) 8 or PND 21 GFP rats were transplanted orthotopically to bilaterally ovariectomized wild-type adult females (n=6). All recipients were mated, and three of the five resulting litters contained GFP pups. In the PND 8 group, all recipients cycled regularly and the ovarian morphology appeared normal when collected at 9 months post-transplantation. In the PND 21 group, 60% of the recipients displayed regular estrous cycles at 9 months post-transplantation, but showed reduced ovarian size. This new strain and neonatal orthotopic transplantation could be useful for many biomedical fields including transplantation, development, and reproductive toxicology.

Abnormally low expression of connexin 37 and connexin 43 in subcutaneously transplanted cryopreserved mouse ovarian tissue

PURPOSE

To analyze the gap junction proteins connexin 37 (Cx37) and connexin 43 (Cx43) after subcutaneous transplantation of cryopreserved mouse ovarian tissue.

METHODS

Expression of gap junction genes was assessed by immunohistochemistry and real-time polymerase chain reaction (PCR) in transplanted cryopreserved ovarian tissue compared with that of normal ovarian tissue. Apoptosis of ovarian cells was evaluated by using the terminal deoxynucleotidyl transferase-mediated biotinylated deoxyuridine triphosphates nick end-labeling method.

RESULTS

After subcutaneous transplantation, Cx37 and Cx43 mRNA and protein expression were significantly lower in cryopreserved than in normal ovarian tissue. Apoptosis was increased in granulosa cells from antral follicles of the cryopreserved tissue.

CONCLUSION

After cryopreservation and subcutaneous transplantation of ovarian tissue, proteins forming gap junctions between oocytes and granulosa cells are under-expressed compared with normal controls.

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.

Preservation of fertility in young cancer patients: contribution of transmission electron microscopy

During the last decade, new technologies in reproductive medicine have emerged to preserve the fertility of women whose gonadal function is threatened by premature menopause or gonadotoxic treatments. To offer an individualized approach to these patients, different experimental procedures are under investigation, including oocyte cryopreservation and cryopreservation and transplantation of ovarian tissue in the form of cortical fragments, whole ovary or isolated follicles. This review shows that transmission electron microscopy (TEM), combined with other in-vivo and in-vitro analysis techniques, is a valuable tool in the establishment of new experimental protocols to preserve female fertility. Ultrastructural studies allow in-depth evaluation of the oocyte's unique morpho-functional characteristics, which explain its low cryotolerance, and provide essential information on follicular, stromal and endothelial cell integrity, as well as cellular interactions crucial for normal folliculogenesis. In order to be able to offer appropriate and efficient options in every clinical situation, oocyte in-vitro maturation and ovarian tissue transplantation need to be optimized. Further development of new approaches, such as follicular isolation and whole ovary transplantation, should be encouraged. Fine ultrastructural details highlighted by TEM studies will be useful for the further optimization of these emerging technologies.

Reproductive outcome after transplantation of ovarian tissue: a systematic review

BACKGROUND

Despite interest in ovarian tissue transplantation (OTT) as a promising procedure for fertility preservation, to date, no precise data are available about its effectiveness. We systematically reviewed reproductive function after OTT for fertility preservation in women at high risk of premature ovarian failure (POF).

METHODS

We searched the MEDLINE, EMBASE, Cochrane Systematic Reviews, CENTRAL, Web of Science and Scopus databases for studies on the reproductive outcomes after OTT in humans up to June 2007. Women with follicle-stimulating hormone (FSH) >30 IU/l at the time of OTT were included in a meta-analysis of individual-patient data to evaluate the time to re-establishment of ovarian function (ROF). Secondary outcomes included short-term (<12 months) and long-term (>12 months) ovarian function (OVF) and pregnancy after OTT.

RESULTS

We identified 25 reports including 46 unique cases. OTT was performed to treat POF in 27 women, to prevent POF in 15, to treat infertility in 2 and accidentally in 1. In 23 women with FSH >30 at the time of OTT, OVF was re-established with a median time to ROF of 120 days (range 60-244). Within 6 months after ROF, four women had recurrent ovarian failure. There are insufficient data to evaluate the long-term OVF (>12 months). Fresh grafts had an increased likelihood of return of OVF and a decreased likelihood for recurrent ovarian failure compared with cryopreserved grafts [HR of 2.44 (95% CI 0.92, 6.49) and 0.47 (95% CI 0.18, 1.12), respectively]. In 25 women who sought pregnancy, eight women had nine pregnancies at 12 months, giving a cumulative pregnancy rate of 37% (95% CI 19, 60).

CONCLUSIONS

Transplantation of ovarian tissue can re-establish OVF after POF; however, the efficacy of OTT using cryopreserved tissues is not yet equivalent to that of fresh grafts. A controlled multicenter trial with sufficient follow-up would provide valid evidence of the potential benefit of this procedure.

Long-term ovarian function and fertility after heterotopic autotransplantation of cryobanked human ovarian tissue: 8-year experience in cancer patients

OBJECTIVE

To assess the long-term ovarian function and fertility after heterotopic autotransplantation of frozen-thawed ovarian tissue in cancer patients.

DESIGN

Prospective clinical case series.

SETTING

Academic medical center

PATIENT(S)

Four young cancer patients who completed cancer treatment.

INTERVENTION(S)

Cryopreserved ovarian tissue (2000-2002) was thawed and transplanted to the heterotopic site (between the rectus muscle and fascia) between 2002 and 2005.

MAIN OUTCOME MEASURE(S)

[1] Serial blood tests (FSH, LH, estradiol, progesterone, testosterone) and ultrasound examinations. [2] Oocyte retrieval and in vitro fertilization.

RESULT(S)

The hormonal profiles were consistent with the postmenopausal level before transplantation. The return of the ovarian function was evidenced by hormonal profiles between 12 and 20 weeks after transplantation. Three patients underwent a second transplantation, as restored ovarian function lasted only 3 to 5 months. After the second transplantation, long-term ovarian function (lasting for 15-41 months) was established in all three patients. Six oocytes (one GV, four MI, one MII) were retrieved from the grafts. Three MI oocytes were developed to full maturity in vitro. Four MII oocytes were fertilized and developed to the cleavage stage embryos (up to six-cell).

CONCLUSION(S)

Autotransplantation of frozen-thawed ovarian tissue to a heterotopic site restored long-term ovarian function (for >40 months), and showed a potential to restore fertility in cancer patients.