Effect of cryopreservation and transplantation on the expression of kit ligand and anti-Mullerian hormone in human ovarian tissue

Human ovarian tissue xenotransplantation: advancements, challenges, and future perspectives

Ovarian tissue cryopreservation and transplantation has emerged as a promising fertility preservation technique for individuals facing premature ovarian insufficiency due to various medical conditions or treatments. Xenotransplantation, involving the transplantation of ovarian tissue into animal hosts, has played a pivotal role in refining ovarian tissue cryopreservation and transplantation techniques and addressing key challenges. This review provides a comprehensive overview of the current landscape of ovarian tissue xenotransplantation research, focusing on its applications in investigating ovarian biology, optimizing ovarian tissue cryopreservation and transplantation protocols, and assessing safety concerns. It also explores the utilization of xenografting of human ovarian tissue in mouse models in the last 10 years. Key findings from preclinical studies investigating grafting site optimization, cryopreservation protocol refinement, the development of strategies to mitigate chemotherapy-induced damage, follicle development, tissue revascularization, and the risk of malignant cell reintroduction are summarized. Moreover, the review examines the ethical considerations surrounding the use of animals in ovarian tissue xenotransplantation research and suggests emerging alternative models that aim to minimize animal use while maximizing clinical relevance.

Impact of endometriosis on the ovarian follicles

A significant body of evidence has supported a negative impact of endometriosis on ovarian follicles; however, the origin and relevance of this ovarian impairment in endometriosis is still a matter of debate. The ovarian damage can be caused by endometriosis itself or by surgeries aiming to remove endometriotic lesions. In this review, we summarized the existing knowledge on the mechanisms by which endometriosis can impact the ovarian follicles, from molecular to clinical points of view. From a molecular standpoint, the presence of endometriosis or its consequences can induce oxidative stress, inflammation, aberrant mitochondrial energy metabolism and inappropriate steroid production in granulosa cells, phenomena that may impair the quality of oocytes to variable degrees. These alterations may have clinical relevance on the accelerated exhaustion of the ovarian reserve, on the ovarian response to gonadotrophin stimulation in IVF cycles and on the competence of the oocytes. Critical points to be considered in current clinical practices related to fertility issues in endometriosis are discussed.

Decreased oocyte quality in patients with endometriosis is closely related to abnormal granulosa cells

Infertility and menstrual abnormalities in endometriosis patients are frequently caused by aberrant follicular growth or a reduced ovarian reserve. Endometriosis typically does not directly harm the oocyte, but rather inhibits the function of granulosa cells, resulting in a decrease in oocyte quality. Granulosa cells, as oocyte nanny cells, can regulate meiosis, provide the most basic resources required for oocyte development, and influence ovulation. Endometriosis affects oocyte development and quality by causing granulosa cells apoptosis, inflammation, oxidative stress, steroid synthesis obstacle, and aberrant mitochondrial energy metabolism. These aberrant states frequently interact with one another, however there is currently relatively little research in this field to understand the mechanism of linkage between abnormal states.

Recombinant anti-Mullerian hormone treatment attenuates primordial follicle loss after ovarian cryopreservation and transplantation

PURPOSE

The foremost drawback of ovarian tissue cryopreservation and re-transplantation (OTCT) technique is the rapid loss of the primordial follicle (PF) pool. In recent studies, we have demonstrated that post-transplantation burnout of the PFs occurs due to the altered expression of the activatory and inhibitory proteins that control PF reserve, and rapamycin prevented it.

METHODS

Here, we investigated whether anti-Mullerian hormone administration in the bilateral oophorectomy and transplantation group and internal AMH in the unilateral oophorectomy and transplantation group protect follicle reserve by regulating the expression of the molecules that control follicle growth after OTCT in mice.

RESULTS

After 14 days of OTCT, PF reserve is significantly reduced in both unilateral oophorectomy and transplantation and bilateral oophorectomy and transplantation groups, while anti-Mullerian hormone treatment attenuates PF loss after bilateral oophorectomy and transplantation. The expression of KitL, Bmp-15, and p27 decreased after unilateral oophorectomy and transplantation and bilateral oophorectomy and transplantation, yet recombinant anti-Mullerian hormone treatment did not restore the expression of these proteins in the BLO-T group.

CONCLUSION

Exogenous recombinant anti-Mullerian hormone administration in the BLO-T group preserved the expressions of Tsc1 and Gdf-9 in PF and p-s6k and Gdf-9 in growing follicles after OTCT. Nonetheless, recombinant anti-Mullerian hormone administration did not affect granulosa cell proliferation and death rates in the growing follicles. These findings suggest a novel hormonal replacement strategy for fertility preservation by restoring anti-Mullerian hormone to regulate Tsc1 and p-s6k, thereby linking this hormone with the mTOR pathway and Gdf-9 signaling.

Proliferating cell nuclear antigen presentation, as a marker of folliculogenesis, in the transplanted ovarian tissue

AIM

One of the most important ways to understand the ovarian biology is studding the initiation of primordial follicle development and subsequent folliculogenesis control. In this study, proliferating cell nuclear antigen (PCNA) presentation was used as a marker of follicular development in the thawed ovarian tissue (OT) following transplantation onto chick embryo chorioallantoic membrane (CAM) using two methods of freezing of slow freezing and vitrification.

METHODS

Samples of OT from 10 patients were subjected to slow freezing and vitrification. After warming, CAM transplantation was done and PCNA proliferation index (PI; percent of PCNA-positive granulosa cells) was calculated for each follicle stage. Image J software was used to determine the mean staining intensity.

RESULTS

PCNA was positive for granulosa cells and oocytes nuclei, but negative for ooplasm. There were no remarkable PCNA staining in the granulosa cells of primordial follicles, but increased significantly as follicle progression (p < 0.05). Proliferation rate was also insignificantly higher in the vitrified than slow freezing group, before and after transplantation (p < 0.05). Lower PCNA presentation index was observed after CAM transplantation (p < 0.05). The earliest stage of follicular recruitment took place in the transitional follicles, before squamous cells transform to cuboidal cells.

CONCLUSION

PCNA showed that follicles had proliferation power after cryopreservation. Higher presentation after vitrification may indicate accelerated folliculogenesis in the thawed OT.

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.

Implications of Nonphysiological Ovarian Primordial Follicle Activation for Fertility Preservation

In recent years, ovarian tissue cryopreservation has rapidly developed as a successful method for preserving the fertility of girls and young women with cancer or benign conditions requiring gonadotoxic therapy, and is now becoming widely recognized as an effective alternative to oocyte and embryo freezing when not feasible. Primordial follicles are the most abundant population of follicles in the ovary, and their relatively quiescent metabolism makes them more resistant to cryoinjury. This dormant pool represents a key target for fertility preservation strategies as a resource for generating high-quality oocytes. However, development of mature, competent oocytes derived from primordial follicles is challenging, particularly in larger mammals. One of the main barriers is the substantial knowledge gap regarding the regulation of the balance between dormancy and activation of primordial follicles to initiate their growing phase. In addition, experimental and clinical factors also affect dormant follicle demise, while the mechanisms involved remain largely to be elucidated. Moreover, most of our basic knowledge of these processes comes from rodent studies and should be extrapolated to humans with caution, considering the differences between species in the reproductive field. Overcoming these obstacles is essential to improving both the quantity and the quality of mature oocytes available for further fertilization, and may have valuable biological and clinical applications, especially in fertility preservation procedures. This review provides an update on current knowledge of mammalian primordial follicle activation under both physiological and nonphysiological conditions, and discusses implications for fertility preservation and priorities for future research.

Hormonal Stimulation of Human Ovarian Xenografts in Mice: Studying Folliculogenesis, Activation, and Oocyte Maturation

Ovarian tissue cryopreservation and banking provides a fertility preservation option for patients who cannot undergo oocyte retrieval; it is quickly becoming a critical component of assisted reproductive technology programs across the world. While the transplantation of cryopreserved ovarian tissue has resulted in over 130 live births, the field has ample room for technological improvements. Specifically, the functional timeline of grafted tissue and each patient's probability of achieving pregnancy is largely unpredictable due to patient-to-patient variability in ovarian reserve, lack of a reliable method for quantifying follicle numbers within tissue fragments, potential risk of reintroduction of cancer cells harbored in ovarian tissues, and an inability to control follicle activation rates. This review focuses on one of the most common physiological techniques used to study human ovarian tissue transplantation, xenotransplantation of human ovarian tissue to mice and endeavors to inform future studies by discussing the elements of the xenotransplantation model, challenges unique to the use of human ovarian tissue, and novel tissue engineering techniques currently under investigation.

Long-Term Advantages of Ovarian Reserve Maintenance and Follicle Development Using Adipose Tissue-Derived Stem Cells in Ovarian Tissue Transplantation

(1) Background: Ovarian tissue transplantation with adipose tissue-derived stem cells (ASCs) has been shown to enhance graft vascularization and increase follicle survival after a short interval of 7 days. The aim of the present study was to investigate their long-term effects on primordial follicle pool maintenance and follicle development. (2) Methods: A total of 14 severe combined immunodeficient (SCID) mice were grafted with frozen-thawed human ovarian tissue with or without ASCs. Blood was taken monthly in order to quantify the anti-Müllerian hormone (AMH) and estradiol. After 6 months, all the grafts were retrieved and sent for histology and immunolabeling (AMH, AMH receptor II, estrogen receptors α and β, and c-kit/kit ligand). (3) Results: A significant upturn was observed in AMH and estradiol plasma levels 4 months after transplantation in both grafted groups. The primordial follicle pool was better preserved in the ASC group (41.86 ± 28.35) than in the standard transplantation group (9.65 ± 17.6, p < 0.05) compared to non-grafted controls (124.7 ± 140). (4) Conclusions: The use of ASCs prior to ovarian tissue transplantation yielded a larger primordial follicle pool and more physiological follicle distribution after long-term grafting. These findings suggested that ASC use might extend the ovarian tissue lifespan.

Altered expression of activator proteins that control follicle reserve after ovarian tissue cryopreservation/transplantation and primordial follicle loss prevention by rapamycin

PURPOSE

We investigated whether expression of activator proteins that control follicle reserve and growth change after ovarian tissue vitrification and re-transplantation. Moreover, we assessed whether inhibition of mTOR signaling pathway by rapamycin would protect primordial follicle reserve after ovarian tissue freezing/thawing and re-transplantation.

METHODS

Fresh control, frozen/thawed, fresh-transplanted, frozen/thawed and transplanted, rapamycin/control, rapamycin fresh-transplanted, and rapamycin frozen-thawed and transplanted groups were established in rats. After freezing and thawing process, two ovaries were transplanted into the back muscle of the same rat. After 2 weeks, grafts were harvested, fixed, and embedded into paraffin block. Normal and atretic primordial/growing follicle count was performed in all groups. Ovarian tissues were evaluated for the dynamic expressions of Gdf-9, Bmp-15, KitL, Lif, Fgf-2, and p-s6K using immunohistochemistry, and H-score analyses were done.

RESULTS

Primordial follicle reserve reduced almost 50% after ovarian tissue re-transplantation. Expression of Gdf-9 and Lif increased significantly in primordial and growing follicles in frozen-thawed, fresh-transplanted, and frozen/thawed and transplanted groups, whereas expression of Bmp-15, KitL, and Fgf-2 decreased in primordial follicles. Freezing and thawing of ovarian tissue solely significantly increased p-s6K expression in primordial follicles, and on the other hand, suppression of mTORC1 pathway using rapamycin preserved the primordial follicle pool.

CONCLUSION

Altered expressions of activator proteins that regulate primordial follicle reserve and growth may lead to primordial follicle loss and rapamycin treatment can protect ovarian reserve after ovarian tissue cryopreservation/transplantation.

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.

Effects of Ovarian Transplant on Anti-Müllerian Hormone, Kisspeptin-1, and Kisspeptin-1 Receptor Levels in Rats

OBJECTIVES

Information is scarce on levels of kisspeptin-1 and the kisspeptin-1 receptorin females after ovarian transplant. In this study, our aim was to explore serum estradiol, anti-Müllerian hormone, kisspeptin-1, and kisspeptin receptor levels, along with kisspeptin-1-positive cell density, in ovaries from rats after ovarian transplant.

MATERIALS AND METHODS

For this study, 28 female Sprague Dawley rats were divided into 4 groups, with sham surgery performed on rats in group 1 (control group). Group 2 rats had ovaries transplanted under the peritoneum, and group 3 rats had their own ovaries transplanted subcutaneously. Group 4 rats were maintained in an estrous state. Serum anti-Müllerian hormone, kisspeptin-1, estradiol, and ovarian kisspeptin receptor levels were determined using commercial enzyme-linked immunosorbent assay kits. Kisspeptin-1-positive cell densities in the ovaries were determined immunohistochemically.The ovaries were also examined histopathologically.

RESULTS

Our statistical analyses showed that levels of kisspeptin receptors in the ovaries were lowest in the subcutaneously transplanted group (group 3; 628.57 ± 35.69 pg/mL). The highest serum anti-Müllerian hormone levels were found in the estrous group (group 4; 16.91 ± 2.12 ng/mL). Differences between groups in terms of serum kisspeptin-1 and estradiol concentrations were not statistically significant.

CONCLUSIONS

Our findings suggest that, in rats, results were better in the peritoneum transplant group than in the subcutaneous transplant group. We also found that serum anti-Müllerian hormone levels were lower in the transplant groups than in the estrous group, although levels were not completely decreased to zero. These results support the finding that ovarian activities continue after transplant.

In vitro Activation Prior to Transplantation of Human Ovarian Tissue: Is It Truly Effective?

Research Question: What are the true benefits, if any, of disrupting the Hippo signaling pathway and stimulating the Akt pathway in xenotransplanted human ovarian tissue using an in vitro activation (IVA) approach? Design: Human ovarian tissue was retrieved from 18 young patients by laparoscopy and grafted to 54 severe combined immunodeficient mice. The experiment was conducted using fresh ovarian tissue (group I; n = 6 women), slow-frozen-thawed ovarian tissue (group II; n = 6 women), and vitrified-warmed ovarian tissue (group III; n = 6 women). Slow-freezing and vitrification procedures were performed according to Gosden's and Kawamura's protocols, respectively. The tissue (fresh, slow-frozen, and vitrified) was fragmented into small cubes (1 × 1 × 1 mm) to disrupt the Hippo signaling pathway and cultured or not in IVA medium for 48 h with Akt stimulators (PI3K stimulator and PTEN inhibitor), before being transplanted to the mice. All the grafts were maintained for 28 days. Results: (1) Follicular density: Follicular density decreased in all groups after transplantation, most significantly in the vitrification group. Culture with IVA had no impact. (2) Follicle activation: Addition of PI3K stimulator and PTEN inhibitor for 48 h prior to grafting did not significantly change the proportion of primordial follicles in any of the groups (fresh, slow-frozen, or vitrified tissue) compared to 48 h of control culture without these molecules. Particularly, vitrification and culture in IVA medium yielded no benefits in terms of growing follicle percentages or follicle proliferation rates. The large proportion of growing follicles in the vitrified tissue group after grafting may have been responsible for the higher rate of atresia. Conclusion: We were unable to demonstrate any significant benefits of cutting ovarian tissue into small cubes and applying IVA with Akt stimulators. The association of vitrification and transplantation was actually found to be the most deleterious combination with respect to the follicle reserve, and even worse when culture with Akt stimulators was performed.

Evaluation of a new freezing protocol containing 20% dimethyl sulphoxide concentration to cryopreserve human ovarian tissue

RESEARCH QUESTION

Could a modification in the ovarian tissue freezing protocol improve follicle survival after cryopreservation and xenotransplantation?

DESIGN

Ovarian tissue was used from 13 adult patients, frozen either with our original protocol, or a modified version involving a higher concentration of dimethyl sulphoxide (DMSO), larger volume of cryopreservation solution and lower seeding temperature. After thawing, the ovarian fragments were xenotransplanted to six mice with severe combined immunodeficiency (SCID) for 3 weeks.

RESULTS

The proportion of primordial follicles decreased, and the proportion of growing follicles increased significantly (all P < 0.01) after cryopreservation and xenografting compared with fresh controls for both protocols. Follicle density, development, ultrastructure and function were similar between treatments.

CONCLUSIONS

This study showed that, although the higher DMSO concentration did not improve survival of preantral follicles, it did not seem to induce any major toxicity in the follicle population either.

Successful in Vitro Fertilization and Embryo Transfer after Transplantation of Cryopreserved Ovarian Tissue: Report of the First Korean Case

For patients at risk of premature ovarian failure with cancer treatment, it is an important option to re-implant the ovarian tissue (OT) after cryopreservation to preserve endocrine function and fertility. With this technique, about 30% of pregnancy success rate and about 90 live births have been reported to date. However, there has been no case report of successful in vitro fertilization (IVF) and embryo transfer (ET) with oocytes collected from transplanted cryopreserved OT in Korea. We report a 30-year old woman with rectal cancer who underwent IVF and ET after cryopreserved OT thawing and re-implantation. She has been diagnosed with stage IIIC rectal cancer after surgery, and right ovary was removed and cryopreserved between cycles of chemotherapy. After completion of chemotherapy and radiotherapy, the patient underwent orthotopic transplantation of cryopreserved OTs. Three months after transplantation, the serum follicle-stimulating hormone level decreased from 91.11 mIU/mL to 43.69 mIU/mL. Thereafter, the patient underwent 11 ovarian stimulation cycles, and in 7 cycles, follicle growth was observed at the OT graft site. In one of these cycles, the oocyte was successfully retrieved and one embryo was transplanted after IVF. The patient was not pregnant, but the cryopreservation of OT can save the fertility after anticancer chemotherapy.

Transplantation of UC-MSCs on collagen scaffold activates follicles in dormant ovaries of POF patients with long history of infertility

Premature ovarian failure (POF) is a refractory disease for clinical treatment with the goal of restoring fertility. In this study, umbilical cord mesenchymal stem cells on a collagen scaffold (collagen/UC-MSCs) can activate primordial follicles in vitro via phosphorylation of FOXO3a and FOXO1. Transplantation of collagen/UC-MSCs to the ovaries of POF patients rescued overall ovarian function, evidenced by elevated estradiol concentrations, improved follicular development, and increased number of antral follicles. Successful clinical pregnancy was achieved in women with POF after transplantation of collagen/UC-MSCs or UC-MSCs. In summary, collagen/UC-MSC transplantation may provide an effective treatment for POF.

Effect of Vitrification on Functional Morphology and Viability of the Ovarian Tissue

The results of a complex morphofunctional study with markers of proliferation (PCNA and Ki-67), angiogenesis (CD31 and CD34), and structural integrity of mesenchymal cells (vimentin) suggest that the pool of primordial follicles was well preserved in vitrified ovarian tissue and that viability of its cellular components can be rapidly restored during incubation at 37°C within 4 h after thawing.

Expression of inhibitor proteins that control primordial follicle reserve decreases in cryopreserved ovaries after autotransplantation

PURPOSE

Even with 86 live births reported globally so far, the mechanism of primordial follicle loss following autotransplantation of the frozen-thawed ovarian tissue needs further evaluation. Pten, Tsc1, p27, and Amh are the inhibitor proteins that play crucial roles in suppressing the transition from the primordial follicle to primary state, maintaining the primordial follicle reserve. In this study, we aimed to evaluate whether the expression patterns of these proteins change and it may be related to the global primordial follicle loss after autotransplantation of the frozen-thawed ovarian tissue.

METHODS

Four groups were established in rats: fresh-control, frozen/thawed, fresh-transplanted, and frozen/thawed and transplanted. After slow freezing and thawing process, two ovarian pieces were transplanted into the back muscle of the same rat. After 2 weeks, grafts were harvested, fixed, and embedded into the paraffin block. Normal and atretic primordial/growing follicle count was performed in all groups. Ovarian tissues were evaluated for the dynamic expressions of the Pten, Tsc1, p27, and Amh proteins using immunohistochemistry, and H-score analyses were done.

RESULTS

Ovarian tissue cryopreservation does not change the expression patterns of inhibitory proteins that control ovarian reserve. Both in fresh and frozen/thawed autotransplanted groups, the expression of inhibitory proteins and Amh decreased significantly in primordial follicles and in growing follicles, respectively. In control group and in frozen/thawed group, primordial follicle counts were similar but decreased by almost half in both fresh-transplanted and frozen/thawed and transplanted groups.

CONCLUSIONS

One of the causes of primordial follicle loss after transplantation of ovarian graft may be decreased expression of the inhibitory proteins that guard the ovarian reserve and transplantation itself seems to be the major cause for disruption of inhibitory molecular signaling. Our findings highlight important molecular aspects for future clinical applications for fertility preservation in humans.

Effects of vitrification and transplantation on follicular development and expression of EphrinB1 and PDGFA in mouse ovaries

The aim of this study was to assess the follicular development and the patterns of EphrinB1 and PDGFA immunostaining in vitrified mouse ovarian tissue (OT) with and without transplantation. Histological evaluation was performed on fresh and vitrified OTs, whether transplanted or not. RT-PCR was performed on fresh and vitrified ovarian samples (OSs) and vitrified OS graft. Vitrification alone did not significantly reduce the normal primordial, primary, and secondary follicles except antral ones (p > 0.05). However, transplantation decreased all the follicle types. The EphrinB1 immunoexpression showed high intensity in all follicular types in vitrified OT and the significant increased was detected in secondary and antral follicles (p < 0.05). PDGFA protein immunoexpression of primordial and primary follicles was decreased in vitrified OT (p < 0.05). However, the lowest immunoexpression of EphrinB1 and PDGFA was detected after transplantation (p < 0.05). The levels of ephrinb1 and pdgfa mRNA expressions in vitrified OS and vitrified OS grafts were found as comparable to the fresh OS. In conclusion, vitrification has no detrimental effect on the follicles at the different developmental stages, majority of ovarian follicular loss takes place after transplantation rather than vitrification. Overall, vitrification and grafting do not change the ephrinb1 and pdgfa gene expressions. In addition, EphrinB1 and PDGFA are expressed during different stages of folliculogenesis in a different manner in fresh, vitrified, or grafted OTs. Vitrification and/or grafting appear to affect the follicular expression of EphrinB1 and PDGFA. These findings suggest that these proteins could have several functions related to the development of follicles and angiogenesis after transplantation.

Expression of kit ligand and insulin-like growth factor binding protein 3 during in vivo or in vitro development of ovarian follicles in sheep

Expression of Kit ligand (KL) and insulin-like growth factor binding protein (IGFBP3) genes was studied at different in vivo and corresponding in vitro stages of development of the ovarian follicles in sheep. The expression of both KL and IGFBP3 was significantly higher in the primordial follicles relative to any other stage of development. Compared to the other stages, the KL expression in the cumulus cells from in vivo grown large antral follicles and that of IGFBP3 in COCs' isolated from large antral follicles matured in vitro for 24 hr were significantly higher. In the oocytes from in vivo grown ovarian follicles, the expression of KL was the same at all the stages of development. Insulin-like growth factor binding protein 3 expression was also the same in the oocytes at all the stages of the development except for a significantly lower expression in those from antral follicles. The expression of KL in the cumulus cells decreased significantly in the in vitro grown early antral follicles but did not change further as the development progressed. The expression of IGFBP3 in the cumulus cells from in vitro grown ovarian follicles appeared to increase as the development progressed although the increase was not significant between any two consecutive stages of development. In the oocytes in in vitro grown ovarian follicles, the expression levels of KL and IGFBP3 genes did not change with development. It is concluded that (i) KL and IGFBP3 genes follow specific patterns of expression during ovarian folliculogenesis and (ii) in vitro culture of preantral follicles compromises the development potential through alterations in the stage-specific patterns of expression of these and other developmentally important genes.

Ovarian injury during cryopreservation and transplantation in mice: a comparative study between cryoinjury and ischemic injury

STUDY QUESTION

What is the main cause of ovarian injury during cryopreservation and transplantation in mice: cryoinjury or ischemic injury?

SUMMARY ANSWER

Post-transplantation ischemia is the main cause of ovarian injury during cryopreservation and transplantation for restoring ovarian function.

WHAT IS KNOWN ALREADY

During cryopreservation and the transplantation of ovaries, cryoinjury and ischemic injury inevitably occur, which has a detrimental effect on ovarian quality and reserve.

STUDY DESIGN, SIZE, DURATION

A total of 80 B6D2F1 female mice were randomly allocated to 2 control and 6 experimental groups according to the presence or the absence of transplantation (n = 10/group). The control groups consisted of fresh or vitrified-warmed controls that had the whole ovary fixed without transplantation (fresh and vitri-con, respectively). The experimental groups were further divided according to the presence of vitrification (fresh or vitrified-warmed) and the transplantation period (2 [D2], 7 [D7] or 21 [D21] days).

PARTICIPANTS/MATERIALS, SETTING, METHODS

In the control groups, fresh and vitrified-warmed ovaries were immediately fixed after the collection (fresh) and the vitrification-warming process (vitrification control, vitri-con), respectively. Of those experimental groups, three were auto-transplanted with fresh whole ovary (FrOT; FrOT-D2, FrOT-D7 and FrOT-D21). For the other three groups, the ovaries were harvested and stored in liquid nitrogen for 1 week after vitrification and then warmed to auto-transplant the vitrified whole ovaries (vitrified ovary [VtOT]; VtOT-D2, VtOT-D7 and VtOT-D21). After 2, 7 or 21 days of grafting, the grafts and blood sera were collected for analysis by hematoxylin-eosin staining, terminal deoxynucleotidyl transferase dUTP nick end labeling assay, CD31 immunohistochemistry and follicle-stimulating hormone enzyme-linked immunosorbent assay.

MAIN RESULTS AND THE ROLE OF CHANCE

The vitrification-warming procedure decreased the proportion of intact follicles (Grade 1, G1) (vitri-con 50.3% versus fresh 64.2%) but there was a larger decrease due to ischemic injury after transplantation (FrOT-D2: 42.5%). The percentage of apoptotic follicles was significantly increased in the vitrified-warmed ovary group compared with the fresh control, but it increased more after transplantation without vitrification (fresh: 0.9%, vitri-con: 6.0% and FrOT-D2: 26.8%). The mean number of follicles per section and percentage of CD31-positive area significantly decreased after vitrification but decreased to a larger extent after transplantation (number of follicles, fresh: 30.3 ± 3.6, vitri-con: 20.6 ± 2.9, FrOT-D2: 17.9 ± 2.1; CD31-positive area, fresh: 10.6 ± 1.3%, vitri-con: 5.7 ± 0.9% and FrOT-D2: 4.2 ± 0.4%). Regarding the G1 follicle ratio and CD31-positive area per graft, only the FrOT groups significantly recovered with time after transplantation (G1 follicle ratio, FrOT-D2: 42.5%, FrOT-D7: 56.1% and FrOT-D21: 70.7%; CD31-positive area, FrOT-D2: 4.2 ± 0.4%, FrOT-D7: 5.4 ± 0.6% and FrOT-D21: 7.5 ± 0.8%). Although there was no significant difference between the two transplantation groups at each evaluation, the serum follicle-stimulating hormone level of both groups significantly decreased over time.

LIMITATIONS AND REASONS FOR CAUTION

It is unclear how far these results can be extrapolated from mice to the human ovary.

WIDER IMPLICATIONS OF THE FINDINGS

Minimizing ischemic injury should be the first priority rather than preventing cryoinjury alone, and decreasing the combination of cryoinjury and ischemic injury is necessary to improve ovarian quality after cryopreservation and transplantation.

STUDY FUNDING/COMPETING INTEREST

This study was supported by a grant of the Korea Healthcare Technology R&D Project, Ministry of Health & Welfare, Republic of Korea (HI12C0055). The authors have no conflict of interest to declare.

Supplementation of transport and freezing media with anti-apoptotic drugs improves ovarian cortex survival

Background

Ovarian tissue preservation is proposed to patients at risk of premature ovarian failure, but this procedure still needs to be optimized. To limit injury during ovarian tissue cryopreservation, anti-apoptotic drugs were added to the transport and freezing media of ovarian cortex tissue.

Methods

Sheep ovaries were transported, prepared and frozen in solutions containing vehicle or anti-apoptotic drugs (Z-VAD-FMK, a pan-caspase inhibitor, or sphingosine-1-phosphate (S1P), a bioactive lipid). After the tissue was thawed, the ovarian cortex was cultured for 2 or 6 days. Follicular quantification and morphological and proliferation analyses were performed on histological sections.

Results

After 2 days of culture, S1P improved the quality of primordial follicles; higher densities of morphologically normal and proliferative primordial follicles were found. Z-VAD-FMK displayed similar effects by preserving global primordial follicular density, but this effect was evident after 6 days of culture. This drug also improved cell proliferation after 2 and 6 days of culture.

Conclusions

Our results showed that the addition of S1P or Z-VAD-FMK to the transport and freezing media prior to ovarian tissue cryopreservation improves primordial follicular quality and therefore improves global tissue survival. This should ultimately lead to improved fertility restoration after auto-transplantation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13048-016-0216-0) contains supplementary material, which is available to authorized users.

Human single follicle growth in vitro from cryopreserved ovarian tissue after slow freezing or vitrification

STUDY QUESTION

What is the effect of human ovarian tissue cryopreservation on single follicular development in vitro?

SUMMARY ANSWER

Vitrification had a greater negative effect on growth and gene expression of human ovarian follicles when compared with fresh follicles.

WHAT IS KNOWN ALREADY

For human ovarian cortex cryopreservation, the conventional option is slow freezing while more recently vitrification has been demonstrated to maintain good quality and function of ovarian tissues.

STUDY DESIGN, SIZE, DURATION

Ovarian tissues were collected from 11 patients. For every patient, the ovarian cortex was divided into three samples: Fresh, slow-rate freezing (Slow) and vitrification (Vit). Tissue histology was performed and follicles were isolated for single-cell mRNA analysis and in vitro culture (IVC) in 1% alginate for 8 days.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Follicle morphology was assessed with hematoxylin-eosin analysis. Follicles were individually embedded in alginate (1% w/v) and cultured in vitro for 8 days. Follicle survival and growth were assessed by microscopy. Follicle viability was observed after Calcein-AM and ethidium homodimer-I (Ca-AM/EthD-I) staining. Expression of genes, including GDF9 (growth differentiation factor 9), BMP15 (bone morphogenetic protein 15) and ZP3 (zona pellucida glycoprotein 3) in oocytes and AMH (anti-Mullerian hormone), FSHR (FSH receptor), CYP11A (cholesterol side-chain cleavage cytochrome P450) and STAR (steroidogenic acute regulatory protein) in GCs, was evaluated by single-cell mRNA analysis.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 129 follicles were separated from ovarian cortex (Fresh n = 44; Slow n = 40; Vit n = 45). The percentage of damaged oocytes and granulosa cells was significantly higher in both the Slow and Vit groups, as compared with Fresh control (P< 0.05). The growth of follicles in vitro was significantly delayed in the Vit group compared with the Fresh group (P< 0.05). Both slow freezing (P< 0.05) and vitrification (P< 0.05) down-regulated the mRNA levels of ZP3 and CYP11A compared with Fresh group, while there was no significant difference between the Slow and Vit groups (P> 0.05). Vitrification also down-regulates AMH mRNA levels compared with Fresh group (P< 0.05).

LIMITATIONS, REASONS FOR CAUTION

Only short-term IVC studies (8 days) are reported. Further study should be performed to examine and improve follicular development in a long-term culture system after cryopreservation.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first comparison of gene expression and growth of single human ovarian follicles in vitro after either slow freezing or vitrification. With the decreased gene expression and growth during IVC, damage by cryopreservation still exists and needs to be minimized during the long-term IVC of follicles in the future for eventual clinical application.

STUDY FUNDING/COMPETING INTERESTS

This work was supported by the National Natural Science Foundation of China (31230047, 81571386, 81471508, 31429004 and 81501247), National Natural Science Foundation of Beijing (7142166) and Mega-projects of Science Research for the 12th five-year plan (2012ba132b05). There are no conflicts of interest to declare.

Ovarian tissue freezing: current status

PURPOSE OF REVIEW

This article aims to carefully evaluate a number of critical points related to ovarian tissue freezing and presents factual data in terms of live birth rates and risks.

RECENT FINDINGS

Reimplantation of frozen-thawed ovarian tissue remains an experimental procedure according to the American Society for Reproductive Medicine, despite almost 40 live births reported in the literature. Recent literature on the topic has focused on the risk of reimplanting malignant cells, so the present review assesses the risks according to disease.

SUMMARY

This manuscript emphasizes the crucial importance of not only preserving fertility in young women but also clearly explaining to patients the different available options and their respective success rates. Some previously published reviews have reported inaccurate reimplantation success rates. In this review, we report the true picture, with a live birth rate of 25%. Ovarian tissue freezing may be combined with pickup of immature oocytes (at the time of ovarian biopsy and tissue removal) or mature oocytes (if chemotherapy can be delayed).

First pregnancies, live birth, and in vitro fertilization outcomes after transplantation of frozen-banked ovarian tissue with a human extracellular matrix scaffold using robot-assisted minimally invasive surgery

BACKGROUND

Ovarian tissue cryopreservation is an experimental fertility preservation method and the transplantation techniques are still evolving.

OBJECTIVE

We attempted to improve the technique with the utility of a human decellularized extracellular tissue matrix (ECTM) scaffold, robot-assisted minimally invasive surgery, and perioperative pharmacological support.

STUDY DESIGN

We prospectively studied 2 subjects with hemophagocytic lymphohistiocytosis (patient A) and non-Hodgkin lymphoma (patient B) who underwent ovarian tissue cryopreservation at the age of 23 years, before receiving preconditioning chemotherapy for hematopoietic stem cell transplantation. Both experienced ovarian failure postchemotherapy and we transplanted ovarian cortical tissues to the contralateral menopausal ovary 7 and 12 years later, using a human ECTM scaffold and robotic assistance. The ECTM scaffold tissue compatibility was shown in preclinical studies. Patients also received estrogen supplementation and baby aspirin preoperatively to aid in the revascularization process.

RESULTS

Ovarian follicle development was observed approximately 10 (patient A) and 8 (patient B) weeks after ovarian tissue transplantation. Following 8 and 7 cycles of in vitro fertilization, 9 and 10 day-3 embryos were cryopreserved (patients A and B, respectively). While the baseline follicle-stimulating hormone (range 3.6-15.4 mIU/mL) levels near normalized by 7 months and remained steady postovarian transplantation in patient A, patient B showed improved but elevated follicle-stimulating hormone levels throughout (range 21-31 mIU/mL). Highest follicle yield was achieved 14 (8 follicles; patient A) and 11 (6 follicles; patient B) months postintervention. Patient A experienced a chemical pregnancy after the third frozen embryo transfer attempt. She then conceived following her first fresh in vitro fertilization embryo transfer and the pregnancy is currently ongoing. Patient B conceived after the first frozen embryo transfer attempt and delivered a healthy girl at term.

CONCLUSION

We report the first pregnancies after the minimally invasive transplantation of previously cryopreserved ovarian tissue with an ECTM scaffold. This approach seems to be associated with steady ovarian function after a follow-up of up to 2 years.

Histomorphometric Evaluation of Superovulation Effect on Follicular Development after Autologous Ovarian Transplantation in Mice

The effect of superovulation by pregnant mare serum gonadotropin (PMSG) on autologous transplanted ovaries in the lumbar muscles of mice was histomorphometrically evaluated using the indices of number and volume of different kind of follicles and volume of corpora lutea, ovary, and stroma. Angiogenesis was observed after mouse ovarian transplantation on days 14 and 21 after ovarian grafting. After transplantation, the total number and volume of primary and secondary follicles reduced, while PMSG superovulation increased the total number and total volume of tertiary follicles and also the ovarian volume after transplantation. Transplantation increased the average size of primary, secondary, and tertiary follicles. Therefore, primary and secondary follicles can survive after autologous transplantation but their reservations diminished by increasing the time of transplantation. However, number of tertiary follicles and their response to superovulation increased over time after transplantation.

Developmental Status: Impact of Short-Term Ischemia on Follicular Survival of Whole Ovarian Transplantation in a Rabbit Model

Ischemia is the first mechanism that provokes the loss of follicles in ovarian grafts over the long term. In whole ovarian transplantation, it remains unknown, however, how changes in follicular development are influenced by short-term ischemia. Fresh whole ovarian orthotopic auto-transplantation was performed in rabbits with 45 min ischemia, and the impact of ischemia on follicular survival and development status was evaluated at different time-points (1 day, 3 days, 1 week, 2 weeks and 1 month). Assessment of follicular quantity and morphology was carried out via histologic analysis. Follicle proliferating status was evidenced by immunostaining with proliferating cell nuclear antigen (PCNA), and the Hedgehog signaling pathway (Patched and Gli); was verified via TUNEL assay. Quantitative PCR was carried out to quantify the mRNA of target genes including PCNA, Patched, Gli, Caspase 3, Bax, and Bcl-2. Compared with its contralateral fresh controls, the morphology, proliferation and apoptosis of the follicles in the grafts showed no significant differences and most primordial follicles were quiescent. However, morphology and proliferation status were significantly decreased 1 week after grafting, in comparison with the longitudinal grafting time. Patched and Gli in the Hedgehog signaling pathway were activated in only the follicles of the grafts. Short-term ischemia slightly impacts follicular survival and development status in whole ovarian grafting. Receiving intervention in the first week post-transplantation might be helpful.

Impact of the cryopreservation technique and vascular bed on ovarian tissue transplantation in cynomolgus monkeys

PURPOSE

The aim of this study was to determine the best combination in terms of cryopreservation techniques and vascular bed preparation before grafting in order to obtain functional ovarian tissue after transplantation.

METHODS

Five cynomolgus monkeys were used. Strips from 10 ovaries were cryopreserved, 5 by vitrification (V), and 5 by slow-freezing (SF). Pieces of fresh ovarian tissue were used for controls. After 1 month, the strips were autografted to two different vascular beds, healed (HB) or freshly decorticated (FDB), constituting four study groups: SF-HB, SF-FDB, V-HB, and V-FDB. These were compared to fresh tissue. After 6 months, the ovaries were removed and several parameters analyzed: follicle quality, stage, density, proliferation, apoptosis, functionality, vascularization, and fibrosis. Mixed effect linear regression models were built to assess the impact of cryopreservation and vascular bed preparation on ovarian tissue viability and functionality. p values were adjusted for multiple testing using the Benjamini-Hochberg method, and q values < 0.20 were considered significant in order to achieve a 20% false discovery rate.

RESULTS

Compared to fresh tissue, no difference was observed in the percentage of morphologically normal follicles, while a significant increase was noted in the follicle proliferation rate (41%, q = 0.19), percentage of antral follicles (12%, q = 0.14), and number of vessels per area (3.3 times, q = 0.07) in the V-FDB group.

CONCLUSIONS

Vitrification associated with FDB vascular bed preparation is the best combination to obtain functional autografted ovarian tissue. Further studies are nevertheless required, with confirmed pregnancies and live births before introducing the procedure into clinical practice.

Damage to fetal bovine ovarian tissue caused by cryoprotectant exposure and vitrification is mitigated during tissue culture

PURPOSE

The objective of this study is to characterize the impact of exposure to cryoprotectants followed by vitrification on primordial follicle survival and activation using a fetal bovine model.

METHODS

In the first study, fetal bovine cortical pieces were exposed to cryoprotectants with or without sucrose and cultured up to 7 days in the presence or absence of insulin. In the second study, cortical pieces were exposed to cryoprotectants with or without sucrose, vitrified, and cultured up to 7 days after warming in the presence or absence of insulin. Viability and morphology of follicles, as well as proliferation and/or DNA repair in ovarian tissue were analyzed.

RESULTS

When compared to non-exposed controls, normal follicular morphology was affected in groups exposed to cryoprotectants only immediately post-exposure and after 1 day of culture, but improved by day 3 and did not significantly differ by day 7. Similarly, normal follicular morphology was compromised in vitrified groups after warming and on day 1 compared to controls, but improved by days 3 and 7. Proliferation and/or DNA repair in ovarian tissue was not affected by vitrification in this model. Cryoprotectant exposure and vitrification of ovarian tissue did not impair the activation of primordial follicles in response to insulin, although activation was delayed relative to non-exposed controls. Interestingly, sucrose had no noticeable protective effect.

CONCLUSION

Vitrified fetal bovine ovarian tissue has the intrinsic capacity to mitigate the immediate damage to primordial follicles' morphology and retains the capacity to activate. These findings provide a basis for a successful cryopreservation protocol for ovarian cortical tissue in other species including humans.

Effect of Exogenous Anti-Müllerian Hormone Treatment on Cryopreserved and Transplanted Mouse Ovaries

Follicle loss occurs after ovary cryopreservation and transplantation. To preserve the follicle pool of cryopreserved or grafted ovaries, anti-Müllerian hormone (AMH), which inhibits ovarian follicle recruitment, was used in a mouse model. In experiment 1, ovaries were vitrified warmed with different doses of AMH (0, 5, 15, or 45 μg/mL) supplementation. In experiment 2, AMH (0, 50, 250, and 1250 μg/mL) was injected into mice before and/or after cryopreserved ovary autotransplantation, and the recipients remained for 7 or 28 days after grafting. Ovaries were evaluated by follicle morphology, density, and apoptosis ratio. Additionally, serum follicle-stimulating hormone was measured in experiment 2. Significantly decreased follicle apoptosis were detected in AMH-treated groups when compared to the control ovaries in experiment 1, meanwhile no positive effect of exogenous AMH was found in experiment 2. Thus, we suggest AMH supplementation during ovary vitrification warming has beneficial effect on reducing follicle apoptosis.

Xenotransplantation of cryopreserved human ovarian tissue--a systematic review of MII oocyte maturation and discussion of it as a realistic option for restoring fertility after cancer treatment

OBJECTIVE

To systematically review the reporting of MII (MII) oocyte development after xenotransplantation of human ovarian tissue.

DESIGN

Systematic review in accordance with the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA).

SETTING

Not applicable.

PATIENT(S)

Not applicable.

INTERVENTION(S)

Formation of MII oocytes after xenotransplantation of human ovarian tissue.

MAIN OUTCOME MEASURE(S)

Any outcome reported in Pubmed.

RESULT(S)

Six publications were identified that report on formation of MII oocytes after xenotransplantation of human ovarian tissue.

CONCLUSION(S)

Xenografting of human ovarian tissue has proved to be a useful model for examining ovarian function and follicle development in vivo. With human follicles that have matured through xenografting, the possibility of cancer transmission and relapse can also be eliminated, because cancer cells are not able to penetrate the zona pellucida. The reported studies have demonstrated that xenografted ovarian tissue from a range of species, including humans, can produce antral follicles that contain mature (MII) oocytes, and it has been shown that mice oocytes have the potential to give rise to live young. Although some ethical questions remain unresolved, xenotransplantation may be a promising method for restoring fertility. This review furthermore describes the value of xenotransplantation as a tool in reproductive biology and discusses the ethical and potential safety issues regarding ovarian tissue xenotransplantation as a means of recovering fertility.

Isoform 165 of vascular endothelial growth factor in collagen matrix improves ovine cryopreserved ovarian tissue revascularisation after xenotransplantation in mice

BACKGROUND

Aggressive anti-cancer treatments can result in ovarian failure. Ovarian cryopreservation has been developed to preserve the fertility of young women, but early graft revascularisation still requires improvement.

METHODS

Frozen/thawed sheep ovarian cortical biopsies were embedded in collagen matrix with or without isoform 165 of vascular endothelial growth factor (VEGF165) and transplanted into ovaries of immunodeficient mice. Ovaries were chosen as transplantation sites to more closely resemble clinical conditions in which orthotopic transplantation has previously allowed several spontaneous pregnancies.

RESULTS

We found that VEGF165 significantly increased the number of Dextran-FITC positive functional vessels 3 days after grafting. Dextran- fluorescein isothiocyanate (FITC) positive vessels were detectable in 53% and 29% of the mice in the VEGF-treated and control groups, respectively. Among these positive fragments, 50% in the treated group displayed mature smooth-muscle-actin-alpha (alpha-SMA) positive functional vessels compared with 0% in the control group. CD31 positive murine blood vessels were observed in 40% of the VEGF165 transplants compared with 21% of the controls. After 3 weeks, the density of murine vessels was significantly higher in the VEGF165 group.

CONCLUSION

The encapsulation of ovarian tissue in collagen matrix in the presence of VEGF165 before grafting has a positive effect on functional blood vessel recruitment. It can be considered as a useful technique to be improved and further developed before human clinical applications in female cancer patients in the context of fertility preservation.

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.

Fibrin-mediated delivery of an ovarian follicle pool in a mouse model of infertility

The cryopreservation and autotransplantation of ovarian tissue is emerging as a powerful approach for preserving fertility. However, for cancer patients, it may not be possible to transplant ovarian tissue due to the risk of re-seeding disease. We investigated strategies for transplantation of individually isolated follicles to minimize the risk of re-introducing cancer cells present within the vasculature of ovarian stroma. Procedures for large-scale isolation of early-stage follicles and their encapsulation into fibrin hydrogels were developed. For in vivo validation studies, mice were ovariectomized and transplanted with encapsulated follicles into the ovarian bursa. A substantial increase in the number of secondary follicles was observed in the graft at 9 days after transplantation, and antral follicles by day 21, demonstrating primordial follicle recruitment into the growing pool. Initially, elevated follicle-stimulating hormone levels declined substantially by day 21, indicating feedback from the graft; presence of corpora lutea showed the graft's capability of restoring hormone cyclicity. Taken together, the transplanted follicles were able to engraft, mature, and restore ovarian function in an infertile mouse. This biomaterial may, thus, provide a platform for follicle transplantation with a low risk of cancer contamination and for developing strategies that preserve fertility for women facing a cancer diagnosis.

Does stimulation with human gonadotropins and gonadotropin-releasing hormone agonist enhance and accelerate the developmental capacity of oocytes in human ovarian tissue xenografted into severe combined immunodeficient mice?

OBJECTIVE

To assess the capacity of human frozen-thawed ovarian follicles matured in xenografts to form metaphase II (MII) oocytes after xenotransplantation and exogenous stimulation.

DESIGN

Prospective controlled animal study.

SETTING

University hospital gynecology research unit.

PATIENT(S)

Ovarian fragments were obtained from 17 women with malignant diseases who wished to cryopreserve ovarian tissue for later pregnancy before chemotherapy.

ANIMAL(S)

Eighty-eight female severe combined immunodeficient (SCID) mice.

INTERVENTION(S)

Cryopreserved human ovarian tissue was grafted into oophorectomized SCID mice. The mice were divided into three groups: Group A received hMG alone every 2 days for a maximum of 24 weeks; group B additionally received nRH agonist (GnRHa) every 4 weeks; and group C was an untreated control group.

MAIN OUTCOME MEASURE(S)

Follicular density, morphology, proliferation, oocyte maturation, malignant cell contamination.

RESULT(S)

Follicle survival and development were similar in all three groups. No significant interactions between the stimulation protocols and grafting duration were noted. Three MII oocytes were observed in grafted follicles. Two MII oocytes were harvested without stimulation. None of the mice showed signs of reintroduced malignancy, nor did microscopic evaluation of the grafts raise any suspicion of residual malignant disease.

CONCLUSION(S)

After xenotransplantation, human primordial follicles can be matured to MII oocytes even without stimulation. Administering human gonadotropin and GnRHa does not enhance the developmental capacity of xenografted oocytes. The optimal stimulation schedule for grafted tissue remains unknown.

Gene expression in human ovarian tissue after xenografting

Cryobanking and transplantation of ovarian tissue is a promising approach to restore fertility in cancer patients. However, ischemic stress following avascular ovarian cortex grafting is known to induce stromal tissue fibrosis and alterations in follicular development. The aim of the study was to analyze the impact of freeze-thawing and grafting procedures on gene expression in human ovarian tissue. Frozen-thawed ovarian tissue from 14 patients was xenografted for 7 days to nude mice and one ungrafted fragment was used as a control. Immediately after recovery, grafts were processed for RNA extraction and histological analysis. Their expression profile was screened by whole-genome oligonucleotide array (n = 4) and validated by reverse-transcriptase polymerase chain analysis (n = 10). After data filtering, the Limma package was used to build a linear regression model for each gene and to compute its fold change between tissues on Days 0 and 7. After adjusting the P-value by the Sidak method, 84 of the transcripts were significantly altered after 7 days of grafting, including matrix metalloproteinase-9 and -14 and angiogenic factors such as placental growth factor and C-X-C chemokine receptor type 4 (CXCR4). Major biological processes were related to tissue remodeling, including secretory processes, cellular adhesion and response to chemical and hormonal stimuli. Angiopoietin signaling, the interleukin-8 pathway and peroxisome proliferator-activated receptor activation were shown to be differentially regulated. On Day 7, overexpression was confirmed by PCR for interleukin-8, transforming growth factor-beta 1, matrix metalloproteinase-14 and CXCR4, compared with ungrafted controls. In conclusion, new as well as known genes involved in tissue restructuring and angiogenesis were identified and found to play a key role during the first days after human ovarian tissue transplantation. This will facilitate the development of strategies to optimize grafting techniques.

Enhanced follicular recruitment and atresia in cortex derived from ovaries with endometriomas

OBJECTIVE

To evaluate the effects of endometriomas on the regulation of early follicular development.

DESIGN

Histologic analysis of prospectively collected biopsy samples.

SETTING

Research unit in a university hospital.

PATIENT(S)

Women <40 years of age who have ovarian endometriomas.

INTERVENTION(S)

Biopsy of healthy cortex from ovaries affected by endometriomas (≤ 4 cm) and contralateral ovaries without cysts.

MAIN OUTCOME MEASURE(S)

Histomorphological staging of early follicles, measurement of follicle, oocyte, and oocyte nucleus diameters, immunohistochemistry of proliferating cell nuclear antigen, and caspase-3.

RESULT(S)

Thirteen cortical samples from ovaries with endometriomas and 13 samples from contralateral ovaries without endometriomas were evaluated. Cortex from ovaries with endometriomas contained significantly more morphologically atretic early follicles than cortex from contralateral ovaries without cysts. These follicles showed cleaved caspase-3 immunostaining. Diameters of primordial follicles and oocytes were decreased in cortex from ovaries with endometriomas, whereas early follicles with proliferating cell nuclear antigen-positive granulosa cells (GCs) were significantly increased in number.

CONCLUSION(S)

Ovaries with endometriomas, which may be more prone to local pelvic inflammation, showed activated follicular recruitment and atresia of early follicles. The potential contribution of inflammation to follicle "burnout" in case of endometriomas is discussed.

Fertility preservation in women

In women, ∼10% of cancers occur in those <45 years old. Chemotherapy, radiotherapy and bone marrow transplantation can cure >90% of girls and young women with diseases that require such treatments. However, these treatments can result in premature ovarian failure, depending on the follicular reserve, the age of the patient and the type and dose of drugs used. This article discusses the different fertility preservation strategies: medical therapy before chemotherapy; ovarian transposition; embryo cryopreservation; oocyte vitrification; and ovarian tissue cryopreservation. The indications, results and risks of these options are discussed. Whether medical therapy should be used to protect the gonads during chemotherapy remains a source of debate. Fertility preservation needs to be completed before chemotherapy and/or irradiation is started and might take 2-3 weeks with established techniques such as embryo or oocyte cryopreservation. Further studies are needed in patients with cancer to confirm the excellent outcomes obtained in patients without cancer or in egg donation programmes. For prepubertal girls or cases where immediate therapy is required, cryopreservation of ovarian tissue is the only available option. Finally, possible future approaches are reviewed, including in vitro maturation of nonantral follicles, the artificial ovary, oogonial stem cells and drugs to prevent follicle loss.

Attempted application of bioengineered/biosynthetic supporting matrices with phosphatidylinositol-trisphosphate-enhancing substances to organ culture of human primordial follicles

PURPOSE

To improve human primordial follicle culture.

METHODS

Thin or thick ovarian slices were cultured on alginate scaffolds or in PEG-fibrinogen hydrogels with or without bpV (pic), which prevents the conversion of phosphatidylinositol-trisphosphate (PIP3) to phosphatidylinositol-bisphosphate (PIP2) or 740Y-P which converts PIP2 to PIP3. Follicular growth was evaluated by follicular counts, Ki67 immunohistochemistry, and 17β-estradiol (E2) levels.

RESULTS

BpV (pic) had a destructive effect on cultured follicles. Thawed-uncultured samples had more primordial follicles than samples cultured in basic medium and fewer developing follicles than samples cultured in PEG-fibrinogen hydrogels with 740Y-P. There were more atretic follicles in samples cultured on alginate scaffolds than in PEG-fibrinogen hydrogels, and in samples cultured in PEG-fibrinogen hydrogels with 740Y-P than in PEG-fibrinogen hydrogels with basic medium. Ki67 staining was higher in PEG-fibrinogen hydrogels than on alginate scaffolds. E2 levels were higher in thick than in thin slices.

CONCLUSIONS

PEG-fibrinogen hydrogels appear to have an advantage over alginate scaffolds for culturing human primordial follicles. Folliculogenesis is not increased in the presence of substances that enhance PIP3 production or with thin rather than thick sectioning.