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

Advances in the mechanisms related to follicle loss after frozen-thawed ovarian tissue transplantation

Ovaries are important reproductive and endocrine organs in women. Ovarian tissue cryopreservation and transplantation technology can not only solve the fertility problems of patients, but also may improve female endocrine problems. This is particularly important for patients in urgent need of radiotherapy and chemotherapy, and for women with prepubertal malignant tumors. However, follicle loss after freeze-thawing is a key challenge for effective ovarian tissue transplantation and leads to poor transplant outcomes. Therefore, it is crucial to elucidate the mechanisms underlying follicle loss after transplantation. This paper reviews current research on the mechanisms of follicle loss after frozen-thawed ovarian tissue transplantation, including the activation, apoptosis, and pyroptosis mechanisms of primordialfollicles. Further, it highlights the requirement of more experimental studies for improving ovarian tissue transplantation methods.

The mTOR Inhibitor Rapamycin Counteracts Follicle Activation Induced by Ovarian Cryopreservation in Murine Transplantation Models

Background and Objectives: Ovarian tissue cryopreservation followed by autotransplantation (OTCTP) is currently the only fertility preservation option for prepubertal patients. Once in remission, the autotransplantation of frozen/thawed tissue is performed when patients want to conceive. A major issue of the procedure is follicular loss directly after grafting mainly due to follicle activation. To improve follicular survival during the OTCTP procedure, we inhibited the mTOR pathway involved in follicle activation using rapamycin, an mTOR inhibitor. Next, we compared two different in vivo models of transplantation: the recently described non-invasive heterotopic transplantation model between the skin layers of the ears, and the more conventional and invasive transplantation under the kidney capsule. Materials and Methods: To study the effects of adding rapamycin during cryopreservation, 4-week-old C57BL/6 mouse ovaries, either fresh, slow-frozen, or slow-frozen with rapamycin, were autotransplanted under the kidney capsule of mice and recovered three weeks later for immunohistochemical (IHC) analysis. To compare the ear with the kidney capsule transplantation model, fresh 4-week-old C57BL/6 mouse ovaries were autotransplanted to either site, followed by an injection of either LY294002, a PI3K inhibitor, vehicle control, or neither, and these were recovered three weeks later for IHC analysis. Results: Rapamycin counteracts cryopreservation-induced follicle proliferation, as well as AKT and mTOR pathway activation, in ovaries autotransplanted for three weeks under the kidney capsule of mice. Analyses of follicle proliferation, mTOR activation, and the effects of LY294002 treatment were similar in transplanted ovaries using either the ear or kidney capsule transplantation model. Conclusions: By adding rapamycin during the OTCTP procedure, we were able to transiently maintain primordial follicles in a quiescent state. This is a promising method for improving the longevity of the ovarian graft. Furthermore, both the ear and kidney capsule transplantation models were suitable for investigating follicle activation and proliferation and pharmacological strategies.

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.

Cancer Treatment-Related Ovarian Dysfunction in Women of Childbearing Potential: Management and Fertility Preservation Options

PURPOSE

To review the complex concerns of oncofertility created through increased cancer survivorship and the long-term effects of cancer treatment in young adults.

DESIGN

Review chemotherapy-induced ovarian dysfunction, outline how fertility may be addressed before treatment initiation, and discuss barriers to oncofertility treatment and guidelines for oncologists to provide this care to their patients.

CONCLUSION

In women of childbearing potential, ovarian dysfunction resulting from cancer therapy has profound short- and long-term implications. Ovarian dysfunction can manifest as menstrual abnormalities, hot flashes, night sweats, impaired fertility, and in the long term, increased cardiovascular risk, bone mineral density loss, and cognitive deficits. The risk of ovarian dysfunction varies between drug classes, number of received lines of therapy, chemotherapy dosage, patient age, and baseline fertility status. Currently, there is no standard clinical practice to evaluate patients for their risk of developing ovarian dysfunction with systemic therapy or means to address hormonal fluctuations during treatment. This review provides a clinical guide to obtain a baseline fertility assessment and facilitate fertility preservation discussions.

Impacts of vitrification on the transcriptome of human ovarian tissue in patients with gynecological cancer

Objective: This study investigated the effects of a vitrification/warming procedure on the mRNA transcriptome of human ovarian tissues.

Design: Human ovarian tissues were collected and processed through vitrification (T-group) and then subjected to RNA sequencing (RNA-seq) analysis, HE, TdT-mediated dUTP nick-end labeling (TUNEL), and real-time quantitative PCR, and the results were compared to those of the fresh group (CK).

Results: A total of 12 patients, aged 15–36 years old, with a mean anti-Müllerian hormone level of 4.57 ± 3.31 ng/mL were enrolled in this study. According to the HE and TUNEL results, vitrification effectively preserved human ovarian tissue. A total of 452 significantly dysregulated genes (|log2FoldChange| > 1 and p < 0.05) were identified between the CK and T groups. Among these, 329 were upregulated and 123 were downregulated. A total of 372 genes were highly enriched for 43 pathways (p < 0.05), which were mainly related to systemic lupus erythematous, cytokine–cytokine receptor interaction, the TNF signaling pathway, and the MAPK signaling pathway. IL10, AQP7, CCL2, FSTL3, and IRF7 were significantly upregulated (p < 0.01), while IL1RN, FCGBP, VEGFA, ACTA2, and ASPN were significantly downregulated in the T-group (p < 0.05) compared to the CK group, which agreed with the results of the RNA-seq analysis.

Conclusion: These results showed (for the first time to the authors’ knowledge) that vitrification can induce changes in mRNA expression in human ovarian tissues. Further molecular studies on human ovarian tissues are required to determine whether altered gene expression could result in any downstream consequences.

Biomechanical forces and signals operating in the ovary during folliculogenesis and their dysregulation: implications for fertility

BACKGROUND

Folliculogenesis occurs in the highly dynamic environment of the ovary. Follicle cyclic recruitment, neo-angiogenesis, spatial displacement, follicle atresia and ovulation stand out as major events resulting from the interplay between mechanical forces and molecular signals. Morphological and functional changes to the growing follicle and to the surrounding tissue are required to produce oocytes capable of supporting preimplantation development to the blastocyst stage.

OBJECTIVE AND RATIONALE

This review will summarize the ovarian morphological and functional context that contributes to follicle recruitment, growth and ovulation, as well as to the acquisition of oocyte developmental competence. We will describe the changes occurring during folliculogenesis to the ovarian extracellular matrix (ECM) and to the vasculature, their influence on the mechanical properties of the ovarian tissue, and, in turn, their influence on the regulation of signal transduction. Also, we will outline how their dysregulation might be associated with pathologies such as polycystic ovary syndrome (PCOS), endometriosis or premature ovarian insufficiency (POI). Finally, for each of these three pathologies, we will highlight therapeutic strategies attempting to correct the altered biomechanical context in order to restore fertility.

SEARCH METHODS

For each area discussed, a systematic bibliographical search was performed, without temporal limits, using PubMed Central, Web of Science and Scopus search engines employing the keywords extracellular matrix, mechanobiology, biomechanics, vasculature, angiogenesis or signalling pathway in combination with: ovary, oogenesis, oocyte, folliculogenesis, ovarian follicle, theca, granulosa, cumulus, follicular fluid, corpus luteum, meiosis, oocyte developmental competence, preimplantation, polycystic ovary syndrome, premature ovarian insufficiency or endometriosis.

OUTCOMES

Through search engines queries, we yielded a total of 37 368 papers that were further selected based on our focus on mammals and, specifically, on rodents, bovine, equine, ovine, primates and human, and also were trimmed around each specific topic of the review. After the elimination of duplicates, this selection process resulted in 628 papers, of which 287 were cited in the manuscript. Among these, 89.2% were published in the past 22 years, while the remaining 8.0%, 2.4% or 0.3% were published during the 1990s, 1980s or before, respectively. During folliculogenesis, changes occur to the ovarian ECM composition and organization that, together with vasculature modelling around the growing follicle, are aimed to sustain its recruitment and growth, and the maturation of the enclosed oocyte. These events define the scenario in which mechanical forces are key to the regulation of cascades of molecular signals. Alterations to this context determine impaired folliculogenesis and decreased oocyte developmental potential, as observed in pathological conditions which are causes of infertility, such as PCOS, endometriosis or POI.

WIDER IMPLICATIONS

The knowledge of these mechanisms and the rules that govern them lay a sound basis to explain how follicles recruitment and growth are modulated, and stimulate insights to develop, in clinical practice, strategies to improve follicular recruitment and oocyte competence, particularly for pathologies like PCOS, endometriosis and POI.

Rapamycin maintains the primordial follicle pool and protects ovarian reserve against cyclophosphamide-induced damage

Any abnormal activation of primordial follicles and subsequent depletion can irreversibly diminish the ovarian reserve, which is one of the major chemotherapy-induced adverse effects in young patients with cancer. Herein, we investigated the effects of rapamycin on the activation and development of ovarian follicles to evaluate its fertility-sparing therapeutic value in a cyclophosphamide (CTX)-treated mouse model. Based on ovarian histomorphological changes and follicle counting in 50 SPF female C57BL/6 mice, daily administration of 5 mg/kg rapamycin for 30 days was deemed an ideal dosage and duration for administration in subsequent experiments. Compared with the control group, rapamycin treatment inhibited the activation of quiescent primordial follicles, with no obvious side effects observed. Finally, 48 mice were randomly divided into four groups: control, rapamycin-treated, cyclophosphamide-treated, and rapamycin intervention. Body weight, ovarian histomorphological changes, number of primordial follicles, DDX4/MVH expression, apoptosis of follicular cells, and expression of apoptosis protease-activating factor (APAF)-1, cleaved caspase 3, and caspase 3 were monitored. Co-administration of rapamycin reduced primordial follicle loss and the development of follicular cell apoptosis, thereby rescuing the ovarian reserve after CTX treatment. On analyzing the mTOR signaling pathway, we observed that rapamycin significantly decreased CTX-mediated overactivation of mTOR and its downstream molecules. These findings suggest that rapamycin exhibits potential as an ovarian-protective agent that could maintain the ovarian primordial follicle pool and preserve fertility in young female patients with cancer undergoing chemotherapy.

Targeting signaling pathways involved in primordial follicle growth or dormancy: potential application in prevention of follicular loss and infertility

INTRODUCTION

Premature ovarian failure (POF) is one of the important causes of infertility in females. To date, no efficient preventive pharmacological treatment has been offered to prevent POF. Therefore, it is necessary to focus on strategies that provide a normal reproductive lifespan to females at risk of developing POF.

AREAS COVERED

Recently, attention has been drawn to discovering pathways involved in primordial follicle activation, as the inhibition of this process might maintain the stock of primordial follicles and therefore, prevent POF. In vitro and animal studies have resulted in the discovery of several of these pathways that can be used to develop new treatments for POF. These studies show crosstalk of these pathways at different levels. One of the important crossing points of many of these pathways involves anti-Mullerian hormone (AMH). Herein, we discuss different aspects of this topic by reviewing related published articles indexed in PubMed and Web of Science as of December 2021.

EXPERT OPINION

Although the findings seem promising, most of the studies were conducted on animals, and the interaction between these factors and the possible outcomes of their administration in the long term are still unknown. Therefore, further investigation is necessary to assess these aspects.

L-Carnitine improves follicular survival and function in ovarian grafts in the mouse

CONTEXT

Ovarian tissue transplantation is performed to preserve fertility in patients undergoing chemotherapy and radiotherapy. However, the ischemia-reperfusion injury which occurs after the ovarian tissue transplantation causes follicular depletion and apoptosis. l -Carnitine has antioxidant and anti-inflammation properties.

AIMS

Therefore, we aimed to investigate the beneficial effect of l -carnitine on mouse ovaries following heterotopic autotransplantation.

METHODS

Mice were randomly divided into three groups (six mice per group): control, autografted and autografted+l -carnitine (200mg/kg daily intraperitoneal injections). Seven days after ovary autografting, the serum levels of malondialdehyde (MDA), total antioxidant capacity, tumor necrosis factor alpha (TNF-α), interleukin (IL)-6 and IL-10 were measured. Ovary histology, serum concentrations of progesterone and estradiol were also measured 28days after autotransplantation. Data were analysed using one-way analysis of variance (ANOVA) and Tukey test, and the means were considered significantly different at P Key results: In the autografted+l -carnitine group, the total volume of the ovary, the volume of the cortex, the number of follicles, the serum concentrations of IL-10, estradiol and progesterone significantly increased compared to the autografted group. In the autografted+l -carnitine group, serum concentrations of IL-6, TNF-α and MDA were significantly decreased compared to the autografted group.

CONCLUSIONS

Our results indicated that l -carnitine can ameliorate the consequences of ischemia-reperfusion on the mice ovarian tissue following autotransplantation.

IMPLICATIONS

l -carnitine improves the structure and function of transplanted ovaries.

Expression of pro-apoptotic and anti-apoptotic proteins in granulosa cells of women with diminished ovarian reserve

PURPOSE

To evaluate the expressions of caspase-3 and cytochrome c and heat shock protein 70 (Hsp70) in granulosa cells (GCs) from women with normal ovarian reserve (NOR) and diminished ovarian reserve (DOR) undergoing intracytoplasmic sperm injection (ICSI).

METHODS

GCs were collected from 117 infertile women during oocyte retrieval. Patients were classified into four groups as follows: DOR-COC score of 0, DOR-COC score of I, NOR-COC score of 0, and NOR-COC score of I. The caspase-3, cytochrome c, and Hsp70 analyses were performed immunohistochemically in GCs. The ICSI outcomes were evaluated prospectively.

RESULTS

The clinical pregnancy and live birth rates were higher in DOR-COC score of I (15, 30.6%; 14, 38.9%) and NOR-COC score of I (19, 38.77%; 19, 52.7%) groups, compared with DOR-COC score of 0 (12, 24.4%; 3, 6.1%) and NOR-COC score of 0 (3, 6.1%; 0%) groups (p = 0.0001; 0.00002), respectively. Caspase-3 and cytochrome c expression levels were higher in DOR-COC score of 0 (23, 65.7%; 25, 71.4%) and NOR-COC score of 0 groups (19, 61.3%; 20, 64.5%), compared with DOR-COC score of I (8, 32%; 9, 36%) and NOR-COC score of I groups (7, 26.9%; 8, 30.8%) (p = 0.00297; p = 0.002), respectively. Lower expression levels of Hsp70 were found in DOR-COC score of 0 (11, 31.4%) and NOR-COC score of 0 groups (10, 32.3%), compared with DOR-COC score of I (16, 64%) and NOR-COC score of I groups (20, 76.9%) (p = 0.001), respectively. Hsp70 expression levels were positively correlated with the number of day 3 good-quality embryo and negatively correlated with estradiol levels in the DOR group.

CONCLUSION

Our data suggest that COC score of 0 is associated with increased expression levels of apoptotic proteins, decreased expression levels of anti-apoptotic protein, and poor ICSI clinical outcomes in women with and without DOR.

The protective effects of rapamycin pretreatment on ovarian damage during ovarian tissue cryopreservation and transplantation

Ovarian tissue cryopreservation and transplantation (OCT) has been sufficiently proven effective and feasible to preserve fertility for women especially for prepubertal girls suffering from cancer with radiotherapy and chemotherapy. However, grafts' survival, significant follicle loss and a delay of revascularization during OCT still need to be resolved no matter what kind of cryopreserved method being used. Different from previous reports about additives treatment on recipient after ovarian transplantation, we here report a new vitrification protocol with pretreatment of rapamycin, an inhibitor of the mTOR signaling pathway. The rapamycin treatment has been shown to inhibit the activation of mTOR signaling pathway in fresh thawed ovaries or in ovaries shortly grafted in the recipient mice. Further study revealed increased percentage of primordial follicles and reduced apoptosis after 5 days of transplantation. Long-term follow up of ovarian development demonstrated the increase of ovarian survival rates in rapamycin treated ovaries after 2 weeks of transplantation. Although follicular development showed a slight delay with more secondary and early antral follicles found in rapamycin treated ovaries, follicular development was not blocked as manifested by the ovarian morphology after 5 weeks of transplantation. Taken together, the pretreatment of rapamycin before vitrification is a good method for clinical application with its effectiveness on preserving follicle reserve and promoting ovarian survival during the process of OCT.