Rescue of platinum-damaged oocytes from programmed cell death through inactivation of the p53 family signaling network

Discovery and evaluation of novel spiroheterocyclic protective agents via a SIRT1 upregulation mechanism in cisplatin-induced premature ovarian failure

Currently, no effective treatment exists for premature ovarian failure (POF). To obtain compounds with protective effects against POF, we aimed to design and synthesize a series of spiroheterocyclic protective agents with a focus on minimizing toxicity while enhancing their protective effect against cisplatin-induced POF. This was achieved through systematic modifications of Michael receptors and linkers within the molecular structure of 1,5-diphenylpenta-1,4-dien-3-one analogs. To assess the cytotoxicity and activity of these compounds, we constructed quantitative conformational relationship models using an artificial intelligence random forest algorithm, resulting in R2 values exceeding 0.87. Among these compounds, j2 exhibited optimal protective activity. It significantly increased the survival of cisplatin-injured ovarian granulosa KGN cells, improved post-injury cell morphology, reduced apoptosis, and enhanced cellular estradiol (E2) levels. Subsequent investigations revealed that j2 may exert its protective effect via a novel mechanism involving the activation of the SIRT1/AKT signal pathway. Furthermore, in cisplatin-injured POF in rats, j2 was effective in increasing body, ovarian, and uterine weights, elevating the number of follicles at all levels in the ovary, improving ovarian and uterine structures, and increasing serum E2 levels in rats with cisplatin-injured POF. In conclusion, this study introduces a promising compound j2 and a novel target SIRT1 with substantial protective activity against cisplatin-induced POF.

KIT in oocytes: a key factor for oocyte survival and reproductive lifespan

BACKGROUND

The KITL-KIT interaction is known as an important initiator in oocyte activation through the downstream pathway of PI3K-AKT-FOXO3 signalling. Previous studies utilising germ cell-specific Kit mutant knockin and kinase domain knockout models with Vasa-Cre suggested the crucial role of KIT in oocyte activation at the primordial follicle stage.

METHODS

We utilised mice with complete postnatal deletion of KIT expression in oocytes via Gdf9-iCre and conducted analyses on ovarian follicle development, specific markers, hormone assays, and fertility outcomes.

FINDINGS

Our findings reveal contrasting phenotypes compared to previous mouse models with prenatal deletion of Kit. Specifically, postnatal deletion of Kit exhibit no defects in germ cell nest breakdown, follicle activation, and folliculogenesis during development. Remarkably, upon reaching full maturity, mice with postnatal deletion of Kit experience a complete loss of ovarian reserve, growing follicles, and ovarian function. Furthermore, mice display smaller ovarian size and weight, delayed folliculogenesis, and phenotypes indicative of primary ovarian insufficiency (POI), including elevated serum levels of FSH, reduced AMH, and absence of ovarian follicles, ultimately resulting in infertility. Additionally, the ovaries exhibit randomly distributed expression of granulosa and theca cell markers such as Inhibin α, ACVR2B, and LHR. Notably, there is the uncontrolled expression of p-SMAD3 and Ki67 throughout the ovarian sections, along with the widespread presence of luteinised stroma cells and cleaved Caspase-3-positive dying cells.

INTERPRETATION

These genetic studies underscore the indispensable role of KIT in oocytes for maintaining the survival of ovarian follicles and ensuring the reproductive lifespan.

FUNDING

This work was supported by National Institutes of Health grant R01HD096042 and startup funds from UNMC (S.Y.K.).

Gynotoxic Effects of Chemotherapy and Potential Protective Mechanisms

Chemotherapy is one of the leading cancer treatments. Unfortunately, its use can contribute to several side effects, including gynotoxic effects in women. Ovarian reserve suppression and estrogen deficiency result in reduced quality of life for cancer patients and are frequently the cause of infertility and early menopause. Classic alkylating cytostatics are among the most toxic chemotherapeutics in this regard. They cause DNA damage in ovarian follicles and the cells they contain, and they can also induce oxidative stress or affect numerous signaling pathways. In vitro tests, animal models, and a few studies among women have investigated the effects of various agents on the protection of the ovarian reserve during classic chemotherapy. In this review article, we focused on the possible beneficial effects of selected hormones (anti-Müllerian hormone, ghrelin, luteinizing hormone, melatonin), agents affecting the activity of apoptotic pathways and modulating gene expression (C1P, S1P, microRNA), and several natural (quercetin, rapamycin, resveratrol) and synthetic compounds (bortezomib, dexrazoxane, goserelin, gonadoliberin analogs, imatinib, metformin, tamoxifen) in preventing gynotoxic effects induced by commonly used cytostatics. The presented line of research appears to provide a promising strategy for protecting and/or improving the ovarian reserve in the studied group of cancer patients. However, well-designed clinical trials are needed to unequivocally assess the effects of these agents on improving hormonal function and fertility in women treated with ovotoxic anticancer drugs.

Primary oocytes with cellular senescence features are involved in ovarian aging in mice

In mammalian females, quiescent primordial follicles serve as the ovarian reserve and sustain normal ovarian function and egg production via folliculogenesis. The loss of primordial follicles causes ovarian aging. Cellular senescence, characterized by cell cycle arrest and production of the senescence-associated secretory phenotype (SASP), is associated with tissue aging. In the present study, we report that some quiescent primary oocytes in primordial follicles become senescent in adult mouse ovaries. The senescent primary oocytes share senescence markers characterized in senescent somatic cells. The senescent primary oocytes were observed in young adult mouse ovaries, remained at approximately 15% of the total primary oocytes during ovarian aging from 6 to 12 months, and accumulated in aged ovaries. Administration of a senolytic drug ABT263 to 3-month-old mice reduced the percentage of senescent primary oocytes and the transcription of the SASP factors in the ovary, in addition, led to increased numbers of primordial and total follicles and a higher rate of oocyte maturation. Our study provides experimental evidence that primary oocytes, a germline cell type that is arrested in meiosis, become senescent in adult mouse ovaries and that senescent cell clearance reduced primordial follicle loss and mitigated ovarian aging phenotypes.

Sodium thiosulfate does not protect ovarian reserve from cisplatin-induced gonadotoxicity†

Cisplatin, a platinum-containing alkylating agent, is used in the treatment of various tumors owing to its potent antitumor activity. However, it causes permanent and adverse effects, particularly hearing loss and depletion of ovarian reserve. Until recently, there were no clinically available protective agents to mitigate the adverse side effects of cisplatin-induced cytotoxicity. In 2022, sodium thiosulfate (STS) was approved by the Food and Drug Administration for mitigating hearing loss in children and adolescents undergoing cisplatin treatment. Consequently, our investigation aimed to determine if STS could protect ovarian reserve against cisplatin-induced gonadotoxicity. In an ex vivo culture, the cisplatin-only group exhibited a loss of primordial follicles, while post-STS administration after cisplatin exposure effectively protected primordial follicles. However, when post-STS was administrated either 6 or 4 h after cisplatin exposure, it did not confer protection against cisplatin-induced gonadotoxicity in postnatal day 7 or adolescent mouse models. Immunofluorescence assays using γH2AX and cPARP revealed that oocytes within primordial follicles exhibited DNA damage after cisplatin exposure, irrespective of post-STS administration. This underscores the rapid and heightened sensitivity of oocytes to gonadotoxicity. In addition, oocytes demonstrated an increased expression of pCHK2 rather than pERK, suggesting that the pathway leading to oocyte death differs from the pathway observed in the inner ear cell death following cisplatin exposure. These results imply that while the administration of STS after cisplatin is highly beneficial in preventing hearing loss, it does not confer a protective effect on the ovaries in mouse models.

Germline cell de novo mutations and potential effects of inflammation on germline cell genome stability

Uncontrolled pathogenic genome mutations in germline cells might impair adult fertility, lead to birth defects or even affect the adaptability of a species. Understanding the sources of DNA damage, as well as the features of damage response in germline cells are the overarching tasks to reduce the mutations in germline cells. With the accumulation of human genome data and genetic reports, genome variants formed in germline cells are being extensively explored. However, the sources of DNA damage, the damage repair mechanisms, and the effects of DNA damage or mutations on the development of germline cells are still unclear. Besides exogenous triggers of DNA damage such as irradiation and genotoxic chemicals, endogenous exposure to inflammation may also contribute to the genome instability of germline cells. In this review, we summarized the features of de novo mutations and the specific DNA damage responses in germline cells and explored the possible roles of inflammation on the genome stability of germline cells.

Primary oocytes with cellular senescence features are involved in ovarian aging in mice

In mammalian females, quiescent primordial follicles serve as the ovarian reserve and sustain normal ovarian function and egg production via folliculogenesis. The loss of primordial follicles causes ovarian aging. Cellular senescence, characterized by cell cycle arrest and production of the senescence-associated secretory phenotype (SASP), is associated with tissue aging. In the present study, we report that some quiescent primary oocytes in primordial follicles become senescent in adult mouse ovaries. The senescent primary oocytes share senescence markers characterized in senescent somatic cells. The senescent primary oocytes were observed in young adult mouse ovaries, remained at approximately 15% of the total primary oocytes during ovarian aging from 6 months to 12 months, and accumulated in aged ovaries. Administration of a senolytic drug ABT263 to 3-month-old mice reduced the percentage of senescent primary oocytes and the transcription of the SASP cytokines in the ovary. In addition, led to increased numbers of primordial and total follicles and a higher rate of oocyte maturation and female fertility. Our study provides experimental evidence that primary oocytes, a germline cell type that is arrested in meiosis, become senescent in adult mouse ovaries and that senescent cell clearance reduced primordial follicle loss and mitigated ovarian aging phenotypes.

Molecular Mechanisms Determining Mammalian Oocyte Quality with the Treatment of Cancer Therapy

Cancer is a global public health issue and remains one of the leading causes of death in the United States (Siegel et al. CA Cancer J Clin. 72:7-33, 2022). It is estimated in the US in 2022, about 935,000 new cases of cancer will be diagnosed in women, and the probability of developing invasive cancer is 5.8% for females younger than 50 years old (Siegel et al. CA Cancer J Clin. 72:7-33, 2022). However, advances in screening programs, diagnostic methods, and therapeutic options have greatly increased the five-year survival rate in reproductive-age women with a variety of cancers. Given the clinical consequences of gonadotoxic cancer therapies, young, female cancer survivors may face compromised fertility, premature ovarian insufficiency, early-onset menopause, and endocrine dysregulation (Bedoschi et al. Future Oncol. 12:2333-44, 2016). Gonadotoxic side effects may include decreased oocyte quality within surviving follicles, loss of ovarian follicles, and impaired ovarian function. In reproductive-age women, oocyte quality is an important element for successful clinical pregnancies and healthy offspring as poor-quality oocytes may be a cause of infertility (McClam et al. Biol Reprod. 106:328-37, 2022; Marteil et al. Reprod Biol. 9:203-24, 2009; Krisher. J Anim Sci. 82: E14-E23, 2004). Thus, it is critical to determine the quantity and quality of surviving follicles in the ovary after cancer treatment and to assess oocyte quality within those surviving follicles as these are markers for determining the capacity for ovarian function restoration and future fertility, especially for young cancer survivors (Xu et al. Nat Med. 17:1562-3, 2011). The long-term effects of cancer therapeutics on oocyte quality are influenced by factors including, but not limited to, individual patient characteristics (e.g. age, health history, comorbidities, etc.), disease type, or treatment regimen (Marci et al. Reprod Biol Endocrinol. 16:1-112, 2018). These effects may translate clinically into an impaired production of viable oocytes and compromised fertility (Garutti et al. ESMO Open. 6:100276, 2021).

Overactivation or Apoptosis: Which Mechanisms Affect Chemotherapy-Induced Ovarian Reserve Depletion?

Dormant primordial follicles (PMF), which constitute the ovarian reserve, are recruited continuously into the cohort of growing follicles in the ovary throughout female reproductive life. Gonadotoxic chemotherapy was shown to diminish the ovarian reserve pool, to destroy growing follicle population, and to cause premature ovarian insufficiency (POI). Three primary mechanisms have been proposed to account for this chemotherapy-induced PMF depletion: either indirectly via over-recruitment of PMF, by stromal damage, or through direct toxicity effects on PMF. Preventative pharmacological agents intervening in these ovotoxic mechanisms may be ideal candidates for fertility preservation (FP). This manuscript reviews the mechanisms that disrupt follicle dormancy causing depletion of the ovarian reserve. It describes the most widely studied experimental inhibitors that have been deployed in attempts to counteract these affects and prevent follicle depletion.

Chemotherapy-induced ovarian damage and protective strategies

More than 9.2 million women worldwide suffer from cancer, and about 5% of them are at reproductive age. Chemotherapy-induced impairment of fertility affects the quality of life of these women. Several chemotherapeutic agents have been proven to cause apoptosis and autophagy by inducing DNA damage and cellular stress. Injuries to the ovarian stroma and micro-vessel network are also considered as pivotal factors resulting in ovarian dysfunction induced by chemotherapeutic agents. Primordial follicle pool over-activation may also be the mechanism inducing damage to the ovarian reserve. Although many studies have explored the mechanisms involved in chemotherapy-induced reproductive toxicity, the exact molecular mechanisms have not been elucidated. It is essential to understand the mechanisms involved in ovarian damage, in order to develop potential protective treatments to preserve fertility. In this article, we reviewed the current knowledge on the mechanism of chemotherapy-induced ovarian damage and possible protective strategies that prevent the ovary from such damages.

Inhibition of checkpoint kinase prevents human oocyte apoptosis induced by chemotherapy and allows enhanced tumour chemotherapeutic efficacy

STUDY QUESTION

Could inhibition of the checkpoint kinase (CHEK) pathway protect human oocytes and even enhance the anti-tumour effects, during chemotherapy?

SUMMARY ANSWER

CHEK inhibitors prevented apoptosis of human oocytes induced by chemotherapy and even enhanced the anti-tumour effects.

WHAT IS KNOWN ALREADY

CHEK inhibitors showed ovarian protective effects in mice during chemotherapy, while their role in human oocytes is unclear.

STUDY DESIGN, SIZE, DURATION

This experimental study evaluated the ovarian reserve of young patients (120 patients) with cancer, exposed or not exposed to taxane and platinum (TP)-combined chemotherapy. Single RNA-sequencing analysis of human primordial oocytes from 10 patients was performed to explore the mechanism of oocyte apoptosis induced by TP chemotherapy. The damaging effects of paclitaxel (PTX) and cisplatin on human oocytes were also evaluated by culturing human ovaries in vitro. A new mouse model that combines human ovarian xenotransplantation and patient-derived tumour xenografts was developed to explore adjuvant therapies for ovarian protection. The mice were randomly allocated to four groups (10 mice for each group): control, cisplatin, cisplatin + CK1 (CHEK1 inhibitor, SCH 900776), and cisplatin + CK2 (CHEK2 inhibitor, BML277).

PARTICIPANTS/MATERIALS, SETTING, METHODS

In the prospective cohort study, human ovarian follicles were counted and serum AMH levels were evaluated. RNA-sequencing analysis was conducted, and staining for follicular damage (phosphorylated H2AX histone; γH2AX), terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labelling (TUNEL) assays and assessments of apoptotic biomarkers (western blot and immunofluorescence) were conducted in human ovaries. After the treatments, histological analysis was performed on human ovarian samples to investigate follicular populations, and oocyte damage was measured by γH2AX staining, BAX staining, and TUNEL assays. At the same time, the tumours were evaluated for volume, weight, and apoptosis levels.

MAIN RESULTS AND THE ROLE OF CHANCE

Patients who received TP chemotherapy showed decreased ovarian reserves. Single RNA-sequencing analysis of human primordial oocytes indicated that TP chemotherapy induced apoptosis of human primordial oocytes by causing CHEK-mediated TAp63α phosphorylation. In vitro culture of human ovaries showed greater damaging effects on oocytes after cisplatin treatment compared with that after PTX treatment. Using the new animal model, CHEK1/2 inhibitors prevented the apoptosis of human oocytes induced by cisplatin and even enhanced its anti-tumour effects. This protective effect appeared to be mediated by inhibiting DNA damage via the CHEK-TAp63α pathway and by generation of anti-apoptotic signals in the oocytes.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

This was a preclinical study performed with human ovarian samples, and clinical research is required for validation.

WIDER IMPLICATIONS OF THE FINDINGS

These findings highlight the therapeutic potential of CHEK1/2 inhibitors as a complementary strategy for preserving fertility in female cancer patients.

STUDY FUNDING/COMPETING INTEREST(S)

This work was financially supported by the National Natural Science Foundation of China (nos. 82001514 and 81902669) and the Fundamental Research Funds for the Central Universities (2021yjsCXCY087). The authors declare no conflict of interest.

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.

The future of fertility preservation for women treated with chemotherapy

Cytotoxic chemotherapies have been a mainstay of cancer treatment, but are associated with numerous systemic adverse effects, including impacts to fertility and endocrine health. Irreversible ovarian damage and follicle depletion are side-effects of chemotherapy that can lead to infertility and premature menopause, both being major concerns of young cancer patients. Notably, many women will proceed with fertility preservation, but unfortunately existing strategies don't entirely solve the problem. Most significantly, oocyte and embryo freezing do not prevent cancer treatment-induced ovarian damage from occurring, which may result in the impairment of long-term hormone production. Unfortunately, loss of endogenous endocrine function is not fully restored by hormone replacement therapy. Additionally, while GnRH agonists are standard care for patients receiving alkylating chemotherapy to lessen the risk of premature menopause, their efficacy is incomplete. The lack of more broadly effective options stems, in part, from our poor understanding of how different treatments damage the ovary. Here, we summarise the impacts of two commonly utilised chemotherapies - cyclophosphamide and cisplatin - on ovarian function and fertility, and discuss the mechanisms underpinning this damage. Additionally, we critically analyse current research avenues in the development of novel fertility preservation strategies, with a focus on fertoprotective agents.

Microenvironmentally Responsive Chemotherapeutic Prodrugs and CHEK2 Inhibitors Self-Assembled Micelles: Protecting Fertility and Enhancing Chemotherapy

Chemotherapy is a widely used and effective adjuvant treatment for cancer, and it has unavoidable damage to female fertility, with statistics showing 38% of women who have received chemotherapy are infertile. How to reduce fertility toxicity while enhancing the oncologic chemotherapy is a clinical challenge. Herein, co-delivery micelles (BML@PMP) are developed, which are composed of a reduction-sensitive paclitaxel prodrug (PMP) for chemotherapy and a CHEK2 inhibitor (BML277) for both fertility protection and chemotherapy enhancement. BML@PMP achieves fertility protection through three actions: (1) Due to the enhanced permeability and retention (EPR) effect, BML@PMP is more enriched in the tumor, while very little in the ovary (about 1/10th of the tumor). (2) Glutathione (GSH) triggers the release of PTX, and with low levels of GSH in the ovary, the amount of PTX released in the ovary is correspondingly reduced. (3) BML277 inhibits oocyte apoptosis by inhibiting the CHEK2-TAp63α pathway. Because of the different downstream targets of CHEK2 in tumor cells and oocytes, BML277 also enhances chemotherapeutic efficacy by reducing DNA damage repair which is activated through the CHEK2 pathway. This bidirectional effect of CHEK2 inhibitor-based co-delivery system represents a promising strategy for improving oncology treatment indices and preventing chemotherapy-associated fertility damage.

Thyroid hormone triiodothyronine does not protect ovarian reserve from DNA damage induced by X-ray and cisplatin

PURPOSE

Cancer therapy can induce premature ovarian insufficiency, necessitating methods for preserving fertility in female cancer patients. However, the only accepted clinical practice for doing so is cryopreservation of embryos, unfertilized ova, and ovarian tissue, despite potential options such as in vitro maturation of follicles. Therefore, considerable interest has arisen in fertoprotective agents, with research on rat ovarian granulosa cells suggesting that triiodothyronine (T3) regulates an anti-apoptosis mechanism that protects the ovarian reserve from paclitaxel-induced DNA damage. In this study, we used postnatal day 5 mouse ovary to confirm the existence of T3 thyroid hormone receptor (THR), as well as to investigate the potential protective effects of T3 against cisplatin- and X-ray-induced apoptosis. We also tested the potential anti-apoptotic effect of T3 in the breast cancer cell line MDA-MB-231.

METHODS

We treated cultured mouse ovaries with varying concentration of T3 and 4 μM cisplatin and 0.2 Gy X-ray. Real-time PCR, histological analysis, immunoblot analysis, and immunofluorescence were performed to assess the potential anti-apoptotic effects of T3.

RESULTS

We confirmed that THR alpha and beta are expressed in the mouse ovary. T3 (0.1, 1, 10, 100 nM, and 1 µM) does not protect ovarian reserve from cisplatin- or X-ray-induced apoptosis or DNA damage. Similarly, it does not protect mouse granulosa cells and MDA-MB-231 cells from cisplatin- or X-ray-induced apoptosis.

CONCLUSION

Our findings suggest that T3 is ineffective as a fertoprotective agent, and its candidacy as a potential agent to preserve fertility should be reconsidered.

Regulation of Oocyte Apoptosis: A View from Gene Knockout Mice

Apoptosis is a form of programmed cell death that plays a critical role in cellular homeostasis and development, including in the ovarian reserve. In humans, hundreds of thousands of oocytes are produced in the fetal ovary. However, the majority die by apoptosis before birth. After puberty, primordial follicles develop into mature follicles. While only a large dominant follicle is selected to ovulate, smaller ones undergo apoptosis. Despite numerous studies, the mechanism of oocyte death at the molecular level remains elusive. Over the last two and a half decades, many knockout mouse models disrupting key genes in the apoptosis pathway have been generated. In this review, we highlight some of the phenotypes and discuss distinct and overlapping roles of the apoptosis regulators in oocyte death and survival. We also review how the transcription factor p63 and its family members may trigger oocyte apoptosis in response to DNA damage.

VX-765 has a Protective Effect on Mice with Ovarian Injury Caused by Chemotherapy

BACKGROUND

Malignant tumors continue to remain a main global public health issue. In the past 40 years, due to strides made in multi-disciplinary comprehensive treatment schemes for patients suffering from malignant tumors, especially chemotherapy schemes, the survival rate has been greatly improved in such patients. This group can be expected to maintain their fertility or have restored endocrine function following successful malignant tumor treatment. Therefore, focusing on the ovarian damage caused by chemotherapy in women of childbearing age is vital in order to protect their fertility and improve their quality of life.

OBJECTIVE

This study attempted to evaluate whether VX-765 possesses an ovarian protective effect in ovarian injury induced by chemotherapy in the mice model.

METHODS

Female C57BL/6J mice were administered with VX-765 gavage once a day for 21 consecutive days. Use of cyclophosphamide (Cy) began one week after the last gavage administration of VX- 765. Detailed classification of follicles at various levels was then quantified in each group. Immunohistochemistry and Western blot analysis were then used in order to analyze the expression of key proteins (FOXO3a, mTOR, RPS6 and AKT) as well as their phosphorylation of the PI3K / PTEN / AKT pathways in the ovary. The concentrations of AMH were measured by ELISA.

RESULTS

The follicles at all levels of Cy treated mice were less than those of the normal group (P < 0.05). Meanwhile, mice treated with VX-765 prior to receiving Cy treatment had more primordial follicles (PMF) than mice treated with Cy alone (P < 0.05). In early growing follicles (EGF) and antral follicles (AF), no difference was observed among the experimental groups (P > 0.05), however, they were lower than those in the normal group (P < 0.05). In mice treated with continuous Cy, the total follicle number (TF) of mice combined with VX-765 (C-Cy-Vx765) was higher than that of mice without VX-765, and the TF of the two groups was lower than that of the normal group (P < 0.05). The value of PMF/TF in C-Cy-Vx765 group was significantly higher than that in the other three groups, while that of EGF/TF was significantly lower (P < 0.05). Immunohistochemical results showed that the phosphorylated forms of the main proteins of the PI3K / PTEN / AKT pathway were found to be more positive in Cy treated mice. The Western blot analysis showed that when Cy and VX-765 were cotreated, the increased levels of these phosphorylated proteins decreased compared with those treated with Cy alone. The AMH level of infancy Cy and VX-765 co-treated mice was higher than that of infancy normal mice (P < 0.05). After the mice grew to sexual maturity, the AMH level of Cy and VX- 765 co-treated mice was still higher than that of Cy treated mice (P < 0.05), and there was no significant difference with normal mice (P > 0.05).

CONCLUSION

VX-765 can maintain the level of AMH and inhibit the recruitment of PMF, thus protecting mice from Cy induced gonadotropic toxicity. Accordingly, VX-765 may play a protective role in mice with ovarian injury caused by chemotherapy.

TAp63 determines the fate of oocytes against DNA damage

Cyclophosphamide and doxorubicin lead to premature ovarian insufficiency as an off-target effect. However, their oocyte death pathway has been debated. Here, we clarified the precise mechanism of ovarian depletion induced by cyclophosphamide and doxorubicin. Dormant oocytes instead of activated oocytes with high PI3K activity were more sensitive to cyclophosphamide. Checkpoint kinase 2 (CHK2) inhibitor rather than GNF2 protected oocytes from cyclophosphamide and doxorubicin, as cyclophosphamide up-regulated p-CHK2 and depleted primordial follicles in Abl1 knockout mice. Contrary to previous reports, TAp63 is pivotal in cyclophosphamide and doxorubicin-induced oocyte death. Oocyte-specific Trp63 knockout mice prevented primordial follicle loss and maintained reproductive function from cyclophosphamide and doxorubicin, indicated by undetectable levels of BAX and cPARP. Here, we demonstrated that TAp63 is fundamental in determining the signaling of oocyte death against DNA damage. This study establishes the role of TAp63 as a target molecule of adjuvant therapies to protect the ovarian reserve from different classes of chemotherapy.

Oocyte CTR1 is not essential for cisplatin-induced oocyte death of primordial follicle

Accumulated evidence indicates that cisplatin, a platinum-based alkylating agent, causes preferential DNA damage to oocytes of primordial follicles (PFs) in the ovary, suggesting oocyte-favored accumulation of cisplatin. Copper transporter 1 (CTR1; Slc31a1 ) is implicated in facilitating cisplatin uptake in cells. Here we found that oocytes of PFs had constitutively higher expression of CTR1 than other cell types in mouse ovary. However, oocyte-specific Slc31a1 knockout was not sufficient to prevent cisplatin-induced depletion of PFs in vitro . Our data indicate that CTR1 would not be the only route for cisplatin to be transported inside the oocytes of PFs in the ovary.

Potential ovarian toxicity and infertility risk following targeted anti-cancer therapies

Unlike traditional chemotherapy agents which are generally cytotoxic to all cells, targeted anti-cancer therapies are designed to specifically target proliferation mechanisms in cancer cells but spare normal cells, resulting in high potency and reduced toxicity. There has therefore been a rapid increase in their development and use in clinical settings, including in curative-intent treatment regimens. However, the targets of some of these drugs including kinases, epigenetic regulatory proteins, DNA damage repair enzymes and proteasomes, have fundamental roles in governing normal ovarian physiology. Inhibiting their action could have significant consequences for ovarian function, with potentially long-lasting adverse effects which persist after cessation of treatment, but there is limited evidence of their effects on reproductive function. In this review, we will use literature that examines these pathways to infer the potential toxicity of targeted anti-cancer drugs on the ovary.

Lay summary

Compared to traditional chemotherapy agents, anti-cancer therapies are thought to be highly effective at targeting cancer cells but sparing normal cells, resulting in reduced drug side effects. However, many of processes within the cells that these drugs affect are also important for the ovary to work normally, so suppressing them in this way could have long-lasting implications for female fertility. This review examines the potential toxicity of anti-cancer therapies on the ovary.

Protective Effects of Antioxidants on Cyclophosphamide-Induced Ovarian Toxicity

The most common limitation of anticancer chemotherapy is the injury to normal cells. Cyclophosphamide, which is one of the most widely used alkylating agents, can cause premature ovarian insufficiency and infertility since the ovarian follicles are extremely sensitive to their effects. Although little information is available about the pathogenic mechanism of cyclophosphamide-induced ovarian damage, its toxicity is attributed to oxidative stress, inflammation, and apoptosis. The use of compounds with antioxidant and cytoprotective properties to protect ovarian function from deleterious effects during chemotherapy would be a significant advantage. Thus, this article reviews the mechanism by which cyclophosphamide exerts its toxic effects on the different cellular components of the ovary, and describes 24 cytoprotective compounds used to ameliorate cyclophosphamide-induced ovarian injury and their possible mechanisms of action. Understanding these mechanisms is essential for the development of efficient and targeted pharmacological complementary therapies that could protect and prolong female fertility.

Preserving Oocytes in Oncofertility†

The prodigious rise of cancer survival rates enables many cancer survivors to live long lives. Therefore, the side effects of cancer treatments as well as the long-term quality of life after cancer have become more relevant. Ovarian toxicity is a major off-target effect of anticancer agents for childhood and young adult female cancer patients. Both chemotherapy and irradiation have been demonstrated to damage the ovary and increase the risks of premature ovarian failure (POF), early menopause, ovarian endocrine disorders, and sub- or infertility. Oncofertility is an emerging and multidisciplinary research and medical field that focuses on providing cancer patients with fertility preservation options. Oocyte quality and quantity are one of the most important factors to determine women's fertility success; therefore, preserving oocytes is paramount for maintaining the ability of young female cancer patients' reproduction after their recovery. This review summarizes peer-reviewed literature on current oocyte preservation options in oncofertility. We describe in-depth oocyte and embryo cryopreservation, ovarian suppression, ovarian tissue cryopreservation, in vitro maturation, ovarian transposition, and adjuvant therapy. Further, we discuss current guidelines and practices of female fertility preservation that cover preserving oocytes.

Female Oncofertility: Current Understandings, Therapeutic Approaches, Controversies, and Future Perspectives

Recent advances in early detection and oncological therapies have ameliorated the survival rate of young cancer patients. Yet, ovarian impairment induced by chemotherapy and radiotherapy is still a challenging issue. This review, based on clinical and lab-based studies, summarizes the evidence of gonadotoxicity of chemoradiotherapy, the recent approaches, ongoing controversies, and future perspectives of fertility preservation (FP) in female patients who have experienced chemo- or radio-therapy. Existing data indicate that chemotherapeutic agents induce DNA alterations and massive follicle activation via the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway. Meanwhile, the radiation causes ionizing damage, leading to germ cell loss. In addition to the well-established methods, numerous therapeutic approaches have been suggested, including minimizing the follicle loss in cryopreserved ovarian grafts after transplantation, in vitro activation or in vitro growing of follicles, artificial ovarian development, or fertoprotective adjuvant to prevent ovarian damage from chemotherapy. Some reports have revealed positive outcomes from these therapies, whereas others have demonstrated conflictions. Future perspectives are improving the live birth rate of FP, especially in patients with adverse ovarian reserve, eliminating the risk of malignancy reintroducing, and increasing society’s awareness of FP importance.

Effects of PD-1 blockade on ovarian follicles in a prepubertal female mouse

Immunotherapy has emerged at the forefront of cancer treatment. Checkpoint inhibitor pembrolizumab (KEYTRUDA), a chimeric antibody which targets programmed cell death protein 1 (PD-1), has been approved by the Food and Drug Administration (FDA) for use in pediatric patients with relapsed or refractory classical Hodgkin's lymphoma. However, there is currently no published data regarding the effects of pembrolizumab on the ovary of female pediatric patients. In this study, prepubertal immunocompetent and immunodeficient female mice were injected with pembrolizumab or anti-mouse PD-1 antibody. The number of primordial follicles significantly decreased post-injection of both pembrolizumab and anti-mouse PD-1 antibody in immunocompetent mice. However, no changes in follicle numbers were observed in immunodeficient nude mice. Superovulation test and vaginal opening experiments suggest that there is no difference in the number of cumulus-oocyte complexes (COCs) and the timing of puberty onset between the control and anti-mouse PD-1 antibody treatment groups, indicating that there is no effect on short-term fertility. Elevation of pro-inflammatory cytokine TNF-α following COX-2 upregulation was observed in the ovary. CD3+ T-cell infiltration was detected within some ovarian follicles and between stromal cells of the ovaries in mice following treatment with anti-mouse PD-1 antibody. Thus, PD-1 immune checkpoint blockade affects the ovarian reserve through a mechanism possibly involving inflammation following CD3+ T-cell infiltration.

Genomic Consideration in Chemotherapy-Induced Ovarian Damage and Fertility Preservation

Chemotherapy-induced ovarian damage and fertility preservation in young patients with cancer are emerging disciplines. The mechanism of treatment-related gonadal damage provides important information for targeting prevention methods. The genomic aspects of ovarian damage after chemotherapy are not fully understood. Several studies have demonstrated that gene alterations related to follicular apoptosis or accelerated follicle activation are related to ovarian insufficiency and susceptibility to ovarian damage following chemotherapy. This may accelerate follicular apoptosis and follicle reservoir utilization and damage the ovarian stroma via multiple molecular reactions after chemotherapy. This review highlights the importance of genomic considerations in chemotherapy-induced ovarian damage and multidisciplinary oncofertility strategies for providing high-quality care to young female cancer patients.

Targeted cancer treatment and fertility: effect of immunotherapy and small molecule inhibitors on female reproduction

Targeted cancer therapy is rapidly evolving the landscape of personalized health care. Novel approaches to selectively impeding tumour growth carry significant potential to improve survival outcomes, particularly for reproductive-aged patients harbouring treatment refractory disease. Current agents fall within two classes: immunotherapy and small molecule inhibitors. These are collectively divided into the following subclasses: monoclonal antibodies; immunomodulators; adoptive cell therapy; treatment vaccines; kinase inhibitors; proteasome inhibitors; metalloproteinase and heat shock protein inhibitors; and promoters of apoptosis. The short- and long-term effects of these treatments on the female reproductive system are not well understood. As a result, clinicians are rendered unable to appropriately counsel women on downstream effects to their fertility. Data-driven consensus recommendations are desperately needed. This review aims to characterize the effect of targeted cancer therapy on the female hypothalamic-pituitary-ovary axis, direct ovarian function and conception.

The Role of Mutant p63 in Female Fertility

The transcription factor p63, one of the p53 family members, plays an essential role in regulating maternal reproduction and genomic integrity as well as epidermal development. TP63 (human)/Trp63 (mouse) produces multiple isoforms: TAp63 and ΔNp63, which possess a different N-terminus depending on two different promoters, and p63a, p63b, p63g, p63δ, and p63ε as products of alternative splicing at the C-terminus. TAp63 expression turns on in the nuclei of primordial germ cells in females and is maintained mainly in the oocyte nuclei of immature follicles. It has been established that TAp63 is the genomic guardian in oocytes of the female ovaries and plays a central role in determining the oocyte fate upon oocyte damage. Lately, there is increasing evidence that TP63 mutations are connected with female infertility, including isolated premature ovarian insufficiency (POI) and syndromic POI. Here, we review the biological functions of p63 in females and discuss the consequences of p63 mutations, which result in infertility in human patients.

Protective effects of human umbilical cord mesenchymal stem cell-derived conditioned medium on ovarian damage

Chemotherapeutic agents are extensively used to treat malignancies. However, chemotherapy-induced ovarian damage and reduced fertility are severe side effects. Recently, stem cell transplantation has been reported to be an effective strategy for premature ovarian insufficiency (POI) treatment, but safety can still be an issue in stem cell-based therapy. Here, we show the protective effects of human umbilical cord mesenchymal stem cell-derived conditioned medium (hUCMSC-CM) on a cisplatin (Cs)-induced ovarian injury model. hUCMSC-CM can relieve Cs-induced depletion of follicles and preserve fertility. In addition, hUCMSC-CM can decrease apoptosis of oocytes and granulosa cells induced by Cs. RNA sequencing analysis reveals the differentially expressed genes of ovaries after Cs and hUCMSC-CM treatments, including genes involved in cell apoptosis. Furthermore, we show that the granulocyte colony-stimulating factor (G-CSF)/phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) pathway plays an important role in protecting granulosa cells from Cs-induced apoptosis. Together, we confirm the protective effects of hUCMSC-CM on ovarian reserve and fertility in mice treated with Cs, highlighting the remarkable therapeutic effects of hUCMSC-CM.

A Tiered Female Ovarian Toxicity Screening Identifies Toxic Effects of Checkpoint Kinase 1 Inhibitors on Murine Growing Follicles

Ovarian toxicity (ovotoxicity) is one of the major side effects of pharmaceutical compounds for women at or before reproductive age. The current gold standard for screening of compounds' ovotoxicity largely relies on preclinical investigations using whole animals. However, in vivo models are time-consuming, costly, and harmful to animals. Here, we developed a 3-tiered ovotoxicity screening approach starting from encapsulated in vitro follicle growth (eIVFG) and screened for the potential ovotoxicity of 8 preclinical compounds from AstraZeneca (AZ). Results from Tiers 1 to 2 screenings using eIVFG showed that the first 7 tested AZ compounds, AZ-A, -B, -C, -D, -E, -F, and -G, had no effect on examined mouse follicle and oocyte reproductive outcomes, including follicle survival and development, 17β-estradiol secretion, ovulation, and oocyte meiotic maturation. However, AZ-H, a preclinical compound targeting the checkpoint kinase 1 inhibitor to potentiate the anticancer effects of DNA-damaging agents, significantly promoted granulosa cell apoptosis and the entire growing follicle atresia at clinically relevant concentrations of 1 and 10 μM. The more targeted explorations in Tier 2 revealed that the ovotoxic effect of AZ-H primarily resulted from checkpoint kinase 1 inhibition in granulosa cells. Using in vivo mouse model, the Tier 3 screening confirmed the in vitro ovotoxicities of AZ-H discovered in Tiers 1 and 2. Also, although AZ-H at 0.1 μM alone was not ovotoxic, it significantly exacerbated gemcitabine-induced ovotoxicities on growing follicles. Taken together, our study demonstrates that the tiered ovotoxicity screening approach starting from eIVFG identifies and prioritizes pharmaceutical compounds of high ovotoxicity concern.

Molecular Mechanism and Prevention Strategy of Chemotherapy- and Radiotherapy-Induced Ovarian Damage

Fertility preservation is an emerging discipline, which is of substantial clinical value in the care of young patients with cancer. Chemotherapy and radiation may induce ovarian damage in prepubertal girls and young women. Although many studies have explored the mechanisms implicated in ovarian toxicity during cancer treatment, its molecular pathophysiology is not fully understood. Chemotherapy may accelerate follicular apoptosis and follicle reservoir utilization and damage the ovarian stroma via multiple molecular reactions. Oxidative stress and the radiosensitivity of oocytes are the main causes of gonadal damage after radiation treatment. Fertility preservation options can be differentiated by patient age, desire for conception, treatment regimen, socioeconomic status, and treatment duration. This review will help highlight the importance of multidisciplinary oncofertility strategies for providing high-quality care to young female cancer patients.

Cisplatin decreases HOXA13 and alphaVBeta3 integrin levels in the uterus

OBJECTIVE

To examine the effects of cisplatin on uterine histology and implantation molecules and the possible protective role of recombinant Klotho administration on uterine histology and uterine receptivity in mice exposed to cisplatin.

MATERIALS AND METHODS

This study was conducted using thirty-two adult female mice assigned to four groups with 8 mice in each group. Saline was given to the 1st group, cisplatin to the 2nd group, recombinant mouse Klotho to the 3rd group and recombinant mouse Klotho plus cisplatin to the 4th group. Uterine tissues were examined for damage histologically and immunobiologically for the uterine receptivity markers HOXA13 and alphaVBeta3 integrin.

RESULTS

Apoptosis, degeneration, decrease in uterine thickness and uterine absence of gland scores were higher in the cisplatin group (3rd group) compared to the saline group (1st group) (cisplatin vs. saline p < 0.0001 for all parameters). In the recombinant Klotho plus cisplatin group (4th group), scores of apoptosis, degeneration, reduction in uterine thickness and uterine absence of gland were lower than the group receiving only cisplatin (cisplatin plus recombinant Klotho vs cisplatin, p = 0.006 for apoptosis; p = 0.017 for degeneration; p = 0.011 for the reduction in uterine thickness; p = 0.002 for the absence of gland). However, HOXA13 and alphaVBeta3 integrin staining levels were not different between the cisplatin group (group 3) and the cisplatin plus recombinant Klotho group (group 4) (p = 0.980 and p = 0.762, respectively.) CONCLUSION: Cisplatin has adverse effects on the uterus. Administration of recombinant Klotho was found to attenuate the cisplatin-induced damage but failed to preserve levels of the implantation molecules HOXA13 and alphaVbeta3. Further studies examining the effect of cisplatin toxicity using other implantation markers along with functional studies are needed.

Evaluation of mitochondria in mouse oocytes following cisplatin exposure

BACKGROUND

Cisplatin is a platinum-based chemotherapeutic that damages genomic DNA leading to cell death. It also damages mitochondrial DNA and induces high levels of mitochondrial reactive oxygen species (mtROS), further sensitising cells to apoptosis. Notably, immature oocytes are particularly vulnerable to cisplatin treatment, a common side effect of which is depletion of the primordial follicle reserve, leading to infertility and early menopause. Cisplatin is known to damage the DNA of oocytes, but the possibility that cisplatin also compromises oocyte survival and quality by damaging mitochondria, has not been investigated. To begin to address this question, neonatal mice were treated with saline or cisplatin (2 mg/kg or 4 mg/kg) and the short and long-term impacts on mitochondria in oocytes were characterised.

RESULTS

At 6 and 24 h after treatment, mitochondrial localisation, mass and ATP content in immature oocytes were similar between groups. However, TMRM staining intensity, a marker of mitochondrial membrane potential, was decreased in immature oocytes from cisplatin treated mice compared to saline treated controls, consistent with the induction of apoptosis. When mice were super ovulated 5 weeks after exposure, the number of mature oocytes harvested from cisplatin treated mice was significantly lower than controls. Mitochondrial localisation, mass, membrane potential and ATP levels showed no differences between groups.

CONCLUSIONS

These findings suggest that mitochondrial dysfunction may contribute to the depletion of the ovarian reserve caused by cisplatin, but long-term impacts on mitochondria may be minimal as those immature oocytes that survive cisplatin treatment develop into mature oocytes with normal mitochondrial parameters.

DNA repair in primordial follicle oocytes following cisplatin treatment

PURPOSE

Genotoxic chemotherapy and radiotherapy can cause DNA double stranded breaks (DSBs) in primordial follicle (PMF) oocytes, which then undergo apoptosis. The development of effective new fertility preservation agents has been hampered, in part, by a limited understanding of DNA repair in PMF oocytes. This study investigated the induction of classical DSB repair pathways in the follicles of wild type (WT) and apoptosis-deficient Puma^-/- mice in response to DSBs caused by the chemotherapy agent cisplatin.

METHODS

Adult C57BL/6 WT and Puma^-/- mice were injected i.p. with saline or cisplatin (5 mg/kg); ovaries were harvested at 8 or 24 h. Follicles were counted, and H2A histone family member (γH2AX) immunofluorescence used to demonstrate DSBs. DNA repair protein RAD51 homolog 1 (RAD51) and DNA-dependent protein kinase, catalytic subunit (DNA-PKcs) immunofluorescence were used to identify DNA repair pathways utilised.

RESULTS

Puma^-/- mice retained 100% of follicles 24 h after cisplatin treatment. Eight hours post-treatment, γH2AX immunofluorescence showed DSBs across follicular stages in Puma^-/- mice; staining returned to control levels in PMFs within 5 days, suggesting repair of PMF oocytes in this window. RAD51 immunofluorescence eight hours post-cisplatin was positive in damaged cell types in both WT and Puma^-/- mice, demonstrating induction of the homologous recombination pathway. In contrast, DNA-PKcs staining were rarely observed in PMFs, indicating non-homologous end joining plays an insignificant role.

CONCLUSION

PMF oocytes are able to conduct high-fidelity repair of DNA damage accumulated during chemotherapy. Therefore, apoptosis inhibition presents a viable strategy for fertility preservation in women undergoing treatment.

Melatonin provides protection against cisplatin-induced ovarian damage and loss of fertility in mice

RESEARCH QUESTION

Can melatonin provide non-invasive ovarian protection against damage caused by cis-diamminedichloroplatinum (cisplatin) and preserve fertility in female cancer patients? And if so, what is the possible mechanism?

DESIGN

Athymic BALB/c nude tumour-bearing female mice were used to demonstrate whether melatonin affects the antineoplastic effect when co-administrated with cisplatin. Sexually mature and newborn C57BL/6 female mice were used to evaluate the potential effects of melatonin on the ovarian follicle pool, pregnancy rate and litter number in cisplatin-treated mice. The ovaries underwent immunohistochemical, TdT (terminal deoxynucleotidyl transferase)-mediated dUTP nick-end labelling (TUNEL) and gene array analysis to explore the underlying mechanism. In addition, granulosa cells were isolated to investigate the potential protective mechanism of melatonin.

RESULTS

Melatonin not only enhanced the anti-cancer effect of cisplatin in tumour-bearing nude mice, but also reduced ovarian toxicity and preserved long-term fertility in cisplatin-treated C57BL/6 female mice. When co-administrated, melatonin was able to reduce the DNA damage and toxic effects on lipid peroxidation in the ovaries caused by cisplatin. Specifically, melatonin was able to largely restore lipid peroxidation in granulosa cells and thus prevent ovarian follicles from being depleted.

CONCLUSIONS

Melatonin has the potential to be used as a chemotherapeutic adjuvant to simultaneously improve the outcome of anti-cancer treatment and preserve ovarian function during cisplatin chemotherapy. Notably, its properties of DNA protection and antioxidant effects on follicles may benefit female cancer survivors and prevent premature ovarian failure as well as fertility loss caused by chemotherapy.

The effects of recombinant klotho in cisplatin-induced ovarian failure in mice

AIM

To investigate whether recombinant klotho given concomitantly with cisplatin is effective in preventing cisplatin-induced ovarian damage.

METHODS

Thirty-two adult female mice were divided into four groups. Saline was given to the first group, cisplatin to the second group, recombinant mouse klotho to the third group, and recombinant mouse klotho + cisplatin to the fourth group. The removed ovarian tissues were examined and groups were compared histologically and immunohistochemical examination for antimullerian hormone (AMH), superoxide dismutase (SOD) and catalase expression were done. Glutathione peroxidase (GPx) and glutathione reductase (GR) activities were measured by ELISA.

RESULTS

Ovarian tissue weight, primary and secondary follicle counts were higher in cisplatin + recombinant klotho group compared to cisplatin group in our study (respectively p < 0.0001, p < 0.0001, and p = 0.010). Injury scores (stromal congestion, edema and infiltration, follicular degeneration scores and edema in corpus luteum scores) were similar between cisplatin and cisplatin + recombinant klotho groups (all p > 0.05). AMH staining intensities were similar between cisplatin and cisplatin + recombinant klotho groups (p = 0.925). There was no difference between the groups in terms of SOD, GPx, and GR (p > 0.05).

CONCLUSIONS

The recombinant klotho administered before cisplatin could partially protect the ovarian tissue from cisplatin-induced ovarian damage considering that there was no difference in histologic injury score parameters, AMH staining intensity and oxidative stress markers between cisplatin and cisplatin plus klotho groups except that klotho preserved follicules to some extent. The antioxidant mechanism of action of klotho may not be the primary protection mechanism in cisplatin induced ovarian injury.

Asciminib Mitigates DNA Damage Stress Signaling Induced by Cyclophosphamide in the Ovary

Cancer treatments can often adversely affect the quality of life of young women. One of the most relevant negative impacts is the loss of fertility. Cyclophosphamide is one of the most detrimental chemotherapeutic drugs for the ovary. Cyclophosphamide may induce the destruction of dormant follicles while promoting follicle activation and growth. Herein, we demonstrate the in vivo protective effect of the allosteric Bcr-Abl tyrosine kinase inhibitor Asciminib on signaling pathways activated by cyclophosphamide in mouse ovaries. We also provide evidence that Asciminib does not interfere with the cytotoxic effect of cyclophosphamide in Michigan Cancer Foundation (MCF)7 breast cancer cells. Our data indicate that concomitant administration of Asciminib mitigates the cyclophosphamide-induced ovarian reserve loss without affecting the anticancer potential of cyclophosphamide. Taken together, these observations are relevant for the development of effective ferto-protective adjuvants to preserve the ovarian reserve from the damaging effects of cancer therapies.

Can Some Anticancer Treatments Preserve the Ovarian Reserve?

BACKGROUND

Preventing premature ovarian failure (POF) is a major challenge in oncology. With conventional regimens, cytotoxicity-associated POF involves primordial follicles (PF) pool depletion by apoptosis or overactivation mechanisms, notably mediated by the ABL/TAp63 and PI3K/Akt/mTOR pathways. New anticancer treatments have been designed to target pathways implicated in tumor growth. Although concerns regarding fertility arise with these targeted therapies, we hypothesized that targeted therapies may exert off-tumor effects on PF that might delay POF. We provide an overview of evidence concerning these off-tumor effects on PF. Limitations and future potential implications of these findings are discussed.

DESIGN

PubMed was searched by combining Boolean operators with the following keywords: fertility, ovarian, follicle, anti-tumoral, cancer, targeted, cytotoxic, and chemotherapy.

RESULTS

Cisplatin-related PF apoptosis via the ABL/TAp63 pathway was targeted with a tyrosine kinase inhibitor, imatinib, in mice, but effects were recently challenged by findings on human ovarian xenografts in mice. In cyclophosphamide-treated mice, PI3K/Akt/mTOR pathway inhibition with mTOR inhibitors and AS101 preserved the PF pool. Proteasome and GSK3 inhibitors were evaluated for direct and indirect follicle DNA damage prevention. Surprisingly, evidence for cytotoxic drug association with PF pool preservation was found. We also describe selected non-anticancer molecules that may minimize gonadotoxicity.

CONCLUSION

Not all anticancer treatments are associated with POF, particularly since the advent of targeted therapies. The feasibility of associating a protective drug targeting PF exhaustion mechanisms with cytotoxic treatments should be evaluated, as a way of decreasing the need for conventional fertility preservation techniques. Further evaluations are required for transfer into clinical practice.

IMPLICATIONS FOR PRACTICE

Anticancer therapies are associated with infertility in 10%-70% of patients, which is the result of primordial follicles pool depletion. Alone or associated with gonadotoxic treatments, some targeted therapies may exert favorable off-targets effects on the primordial follicle pool by slowing down their exhaustion. Current evidence of these effects relies on murine models or human in vitro models. Evaluation of these protective strategies in humans is challenging; however, if these results are confirmed with clinical and biological data, it not only could be a new approach to female fertility preservation but also would change standard fertility strategies.

DNA Damaged Induced Cell Death in Oocytes

The production of haploid gametes through meiosis is central to the principle of sexual reproduction. The genetic diversity is further enhanced by exchange of genetic material between homologous chromosomes by the crossover mechanism. This mechanism not only requires correct pairing of homologous chromosomes but also efficient repair of the induced DNA double-strand breaks. Oocytes have evolved a unique quality control system that eliminates cells if chromosomes do not correctly align or if DNA repair is not possible. Central to this monitoring system that is conserved from nematodes and fruit fly to humans is the p53 protein family, and in vertebrates in particular p63. In mammals, oocytes are stored for a long time in the prophase of meiosis I which, in humans, can last more than 50 years. During the entire time of this arrest phase, the DNA damage checkpoint remains active. The treatment of female cancer patients with DNA damaging irradiation or chemotherapeutics activates this checkpoint and results in elimination of the oocyte pool causing premature menopause and infertility. Here, we review the molecular mechanisms of this quality control system and discuss potential therapeutic intervention for the preservation of the oocyte pool during chemotherapy.

The role of microRNAs in ovarian function and the transition toward novel therapeutic strategies in fertility preservation: from bench to future clinical application

BACKGROUND

New therapeutic approaches in oncology have converted cancer from a certain death sentence to a chronic disease. However, there are still challenges to be overcome regarding the off-target toxicity of many of these treatments. Oncological therapies can lead to future infertility in women. Given this negative impact on long-term quality of life, fertility preservation is highly recommended. While gamete and ovarian tissue cryopreservation are the usual methods offered, new pharmacological-based options aiming to reduce ovarian damage during oncological treatment are very attractive. In this vein, advances in the field of transcriptomics and epigenomics have brought small noncoding RNAs, called microRNAs (miRNAs), into the spotlight in oncology. MicroRNAs also play a key role in follicle development as regulators of follicular growth, atresia and steroidogenesis. They are also involved in DNA damage repair responses and they can themselves be modulated during chemotherapy. For these reasons, miRNAs may be an interesting target to develop new protective therapies during oncological treatment. This review summarizes the physiological role of miRNAs in reproduction. Considering recently developed strategies based on miRNA therapy in oncology, we highlight their potential interest as a target in fertility preservation and propose future strategies to make the transition from bench to clinic.

OBJECTIVE AND RATIONALE

How can miRNA therapeutic approaches be used to develop new adjuvant protective therapies to reduce the ovarian damage caused by cytotoxic oncological treatments?

SEARCH METHODS

A systematic search of English language literature using PubMed and Google Scholar databases was performed through to 2019 describing the role of miRNAs in the ovary and their use for diagnosis and targeted therapy in oncology. Personal data illustrate miRNA therapeutic strategies to target the gonads and reduce chemotherapy-induced follicular damage.

OUTCOMES

This review outlines the importance of miRNAs as gene regulators and emphasizes the fact that insights in oncology can inspire new adjuvant strategies in the field of onco-fertility. Recent improvements in nanotechnology offer the opportunity for drug development using next-generation miRNA-nanocarriers.

WIDER IMPLICATIONS

Although there are still some barriers regarding the immunogenicity and toxicity of these treatments and there is still room for improvement concerning the specific delivery of miRNAs into the ovaries, we believe that, in the future, miRNAs can be developed as powerful and non-invasive tools for fertility preservation.

Impact of imatinib or dasatinib coadministration on in vitro preantral follicle development and oocyte acquisition in cyclophosphamide-treated mice

OBJECTIVE

We investigated the impact of tyrosine kinase inhibitor (imatinib or dasatinib) coadministration with cyclophosphamide (Cp) on preantral follicle development in an in vitro mouse model.

METHODS

Seventy-three female BDF1 mice were allocated into four experimental groups: group A, saline; group B, Cp (25 mg/kg); group C, Cp (25 mg/kg) and imatinib (7.5 mg/kg); and group D, Cp (25 mg/kg) and dasatinib (7.5 mg/kg). Preantral follicles were isolated and cultured in vitro up to 12 days. Final oocyte acquisition and spindle integrity of metaphase II (MII) oocytes were assessed. Levels of 17β-estradiol and anti-Müllerian hormone (AMH) in the final spent media were measured by enzyme-linked immunosorbent assays, and the mRNA levels of Star, Sod1, Mapk3, and Casp3 in the final follicular cells were quantified by real-time polymerase chain reaction.

RESULTS

The percentage of MII oocytes per initiated follicle, the proportion of MII oocytes with normal spindles, and the 17β-estradiol level were similar in all four groups. The median AMH level in group B (7.74 ng/mL) was significantly lower than that in group A (10.84 ng/mL). However, the median AMH levels in group C (9.96 ng/mL) and group D (9.71 ng/mL) were similar to that in group A. The mRNA expression levels of Star, Sod1, Mapk3, and Casp3 were similar in all four groups.

CONCLUSION

Coadministration of imatinib or dasatinib with Cp could preserve AMH production capacity in this in vitro mice preantral follicle culture model, and it did not affect MII oocyte acquisition.

Continuous treatment with cisplatin induces the oocyte death of primordial follicles without activation

Chemotherapy directly or indirectly affects organs in a short-term or continuous manner. Endocrine organs are especially sensitive to cancer treatment, leading to concerns among patients regarding their quality of life afterward. Side effects to the ovary include damage to the ovarian reserve, resulting in follicle loss, endocrine hormone deficiency, and infertility. It has been previously demonstrated that continuous treatment with 2 mg/kg cisplatin for 15 days can activate primordial follicles, suggesting that the response in the oocytes of primordial follicles was dependent on cisplatin concentration and administration frequency. However, our results demonstrate that continuous treatment with 2 mg/kg cisplatin for 15 days leads to the same consequence as with the continuous treatment of 5 mg/kg cisplatin: the death of oocytes in primordial follicles without indication of activation. Moreover, animals co-injected with melatonin and cisplatin did not display any significant differences from those treated with cisplatin only contrary to the known results. 6-hydroxymelatonin, a metabolite of melatonin, could not prevent follicle destruction, implying that melatonin does not confer the protection of ovarian follicles, either directly or indirectly. Altogether, our data support that fertoprotectants against cisplatin must target molecules that control cell death pathways in the oocytes of primordial follicles.

SIX1 cooperates with RUNX1 and SMAD4 in cell fate commitment of Müllerian duct epithelium

During female mammal reproductive tract development, epithelial cells of the lower Müllerian duct are committed to become stratified squamous epithelium of the vagina and ectocervix, when the expression of ΔNp63 transcription factor is induced by mesenchymal cells. The absence of ΔNp63 expression leads to adenosis, the putative precursor of vaginal adenocarcinoma. Our previous studies with genetically engineered mouse models have established that fibroblast growth factor (FGF)/mitogen-activated protein kinase (MAPK), bone morphogenetic protein (BMP)/SMAD, and activin A/runt-related transcription factor 1 (RUNX1) signaling pathways are independently required for ΔNp63 expression in Müllerian duct epithelium (MDE). Here, we report that sine oculis homeobox homolog 1 (SIX1) plays a critical role in the activation of ΔNp63 locus in MDE as a downstream transcription factor of mesenchymal signals. In the developing mouse reproductive tract, SIX1 expression was restricted to MDE within the future cervix and vagina. SIX1 expression was totally absent in SMAD4 null MDE and was reduced in RUNX1 null and FGFR2 null MDE, indicating that SIX1 is under the control of vaginal mesenchymal factors: BMP4, activin A and FGF7/10. Furthermore, Six1, Runx1, and Smad4 gene-dose-dependently activated ΔNp63 expression in MDE within the vaginal fornix. Using a mouse model of diethylstilbestrol (DES)-associated vaginal adenosis, we found DES action through epithelial estrogen receptor α (ESR1) inhibits activation of ΔNp63 locus in MDE by transcriptionally repressing SIX1 and RUNX1 in the vaginal fornix.

Cisplatin- and cyclophosphamide-induced primordial follicle depletion is caused by direct damage to oocytes

It is well established that DNA-damaging chemotherapies can cause infertility and ovarian endocrine failure by depleting the ovarian reserve of primordial follicles. Currently, no effective pharmacological therapies exist for the preservation of long-term fertility and ovarian function in female cancer patients, due to a limited understanding of the mechanisms of chemotherapy-induced follicle depletion. This study investigated the cellular targets, molecular mechanisms, and temporal course of ovarian reserve depletion following treatment with commonly used chemotherapeutic drugs. Adult female C57BL/6 mice were injected i.p. with saline, cisplatin (5mg/kg), or cyclophosphamide (300mg/kg); ovaries were harvested after 8 or 24 hours. Follicle counts showed depletion of all follicular stages 24 hours after administration of cisplatin or cyclophosphamide. Eight hours post-treatment, H2A histone family member X (γH2AX) immunofluorescence showed DNA double-stranded breaks at all follicular stages, including within primordial follicle oocytes. This staining was resolving by 24 hours, indicating that primordial follicle oocytes begin to undergo either apoptosis or repair in this timeframe. γH2AX-positive follicles were further examined to identify the specific cell types damaged. In primordial, transitional, and primary follicles, only oocytes sustained DNA damage, whereas in secondary and antral follicles, only somatic cells were affected. TUNEL staining confirmed that apoptosis occurs in these targeted cell types. Whilst multi-drug and multi-dose regimens were not examined, this study conclusively shows that cyclophosphamide and cisplatin cause direct damage to primordial follicle oocytes, which then undergo apoptosis. Therefore, future pharmacological strategies to prevent chemotherapy-induced infertility in females must specifically prevent primordial follicle oocyte death.

Ovarian damage from chemotherapy and current approaches to its protection

BACKGROUND

Anti-cancer therapy is often a cause of premature ovarian insufficiency and infertility since the ovarian follicle reserve is extremely sensitive to the effects of chemotherapy and radiotherapy. While oocyte, embryo and ovarian cortex cryopreservation can help some women with cancer-induced infertility achieve pregnancy, the development of effective methods to protect ovarian function during chemotherapy would be a significant advantage.

OBJECTIVE AND RATIONALE

This paper critically discusses the different damaging effects of the most common chemotherapeutic compounds on the ovary, in particular, the ovarian follicles and the molecular pathways that lead to that damage. The mechanisms through which fertility-protective agents might prevent chemotherapy drug-induced follicle loss are then reviewed.

SEARCH METHODS

Articles published in English were searched on PubMed up to March 2019 using the following terms: ovary, fertility preservation, chemotherapy, follicle death, adjuvant therapy, cyclophosphamide, cisplatin, doxorubicin. Inclusion and exclusion criteria were applied to the analysis of the protective agents.

OUTCOMES

Recent studies reveal how chemotherapeutic drugs can affect the different cellular components of the ovary, causing rapid depletion of the ovarian follicular reserve. The three most commonly used drugs, cyclophosphamide, cisplatin and doxorubicin, cause premature ovarian insufficiency by inducing death and/or accelerated activation of primordial follicles and increased atresia of growing follicles. They also cause an increase in damage to blood vessels and the stromal compartment and increment inflammation. In the past 20 years, many compounds have been investigated as potential protective agents to counteract these adverse effects. The interactions of recently described fertility-protective agents with these damage pathways are discussed.

WIDER IMPLICATIONS

Understanding the mechanisms underlying the action of chemotherapy compounds on the various components of the ovary is essential for the development of efficient and targeted pharmacological therapies that could protect and prolong female fertility. While there are increasing preclinical investigations of potential fertility preserving adjuvants, there remains a lack of approaches that are being developed and tested clinically.

Comparative gonadotoxicity of the chemotherapy drugs cisplatin and carboplatin on prepubertal mouse gonads

The treatment of childhood cancer with chemotherapy drugs can result in infertility in adulthood. Newer generations of drugs are developed to replace parent drugs, with the potential benefits of less toxic side effects. For platinum alkylating-like drugs, in contrast to the parent compound cisplatin, the newer-generation drug carboplatin is reported to have reduced toxicity in some respects, despite being administered at 5-15 times higher than the cisplatin dose. Whether carboplatin is also less toxic than cisplatin to the reproductive system is unknown. Here we compare the gonadotoxic impact of cisplatin and carboplatin on female and male mouse prepubertal gonads. In vitro cultured CD1 mouse ovaries or testis fragments were exposed to either cisplatin or carboplatin for 24 h on Day 2 of culture and analysed by Day 6. A dose response for each drug was determined for the ovary (0.5, 1 & 5 μg/ml cisplatin and 1, 5 & 10 μg/ml carboplatin) and the testis (0.01, 0.05 & 0.1 μg/ml cisplatin and 0.1, 0.5 & 1 μg/ml carboplatin). For the ovary, unhealthy follicles were evident from 1 μg/ml cisplatin (73% unhealthy, P = 0.001) and 5 μg/ml carboplatin (84% unhealthy, P = 0.001), with a concomitant reduction in follicle number (P = 0.001). For the testis, the proliferating germ cell population was significantly reduced from 0.05 μg/ml cisplatin (73% reduction, P = 0.001) and 0.5 μg/ml carboplatin (75% reduction, P = 0.001), with no significant impact on the Sertoli cell population. Overall, results from this in vitro animal model study indicate that, at patient equivalent concentrations, carboplatin is no less gonadotoxic than cisplatin.

Single and combined effects of cisplatin and doxorubicin on the human and mouse ovary in vitro

Chemotherapy drugs are administered to patients using combination regimens, and as such the possibility of multiplicative effects between drugs need to be investigated. This study examines the individual and combined effects of the chemotherapy drugs cisplatin and doxorubicin on the human ovary. Although cisplatin and doxorubicin are known to affect female fertility, there is limited information about their direct effects on the human ovary, and none examining the possibility of combined, multiplicative effects of co-exposure to these drugs. Here, human ovarian biopsies were obtained from 14 women at the time of caesarean section, with 38 mouse ovaries also obtained from neonatal C57Bl/6J mice. Tissue was cultured for 6 days prior to analyses, with chemotherapy drugs added to culture medium on the second day of culture only. Treatment groups of a single (5 μg/mL human; 0.5 μg/mL mouse) or double (10 μg/mL human; 1.0 μg/mL mouse) dose of cisplatin, a single (1 μg/mL human; 0.05 μg/mL mouse) or double (2 μg/mL human; 0.1 μg/mL mouse) dose of doxorubicin or a combination of a single dose of both drugs together were compared to controls without drug exposure. Exposure to cisplatin or doxorubicin significantly decreased follicle health in human and mouse, supporting the suitability of the mouse as a model for the human ovary. There was also a significant reduction of mouse follicle number. Human ovarian stromal tissue exhibited increased apoptosis and decreased cell proliferation. Crucially, there was no evidence indicating the occurrence of multiplicative effects between cisplatin and doxorubicin.

Preserving fertility in female patients with hematological malignancies: a multidisciplinary oncofertility approach

Oncofertility is a new interdisciplinary field at the intersection of oncology and reproductive medicine that expands fertility options for young cancer patients. The most common forms of hematological malignancies that occur in girls and young women and therefore necessitate oncofertility care are acute lymphocytic leukemia, acute myeloid leukemia, non-Hodgkin's lymphoma, and Hodgkin's lymphoma. Aggressive gonadotoxic anticancer regimens including alkylating chemotherapy and total body irradiation are used often in treating girls and young women with hematological malignancies. The risks of gonadotoxicity and subsequent iatrogenic premature ovarian insufficiency and fertility loss depend mainly on the type and stage of the disease, dose of anticancer therapy as well as the age of the patient at the beginning of treatment. To avoid or at least mitigate the devastating complications of anticancer therapy-induced gonadotoxicity, effective and comprehensive strategies that integrate different options for preserving and restoring fertility ranging from established to experimental strategies should be offered before, during, and after chemotherapy or radiotherapy. A multidisciplinary approach that involves strong coordination and collaboration between hemato-oncologists, gynecologists, reproductive biologists, research scientists, and patient navigators is essential to guarantee high standard of care.

Consequences of chemotherapeutic agents on primordial follicles and future clinical applications

The ovarian reserve is necessary for female fertility and endocrine health. Commonly used cancer therapies diminish the ovarian reserve, thus, resulting in primary ovarian insufficiency, which clinically presents as infertility and endocrine dysfunction. Prepubertal children who have undergone cancer therapies often experience delayed puberty or cannot initiate puberty and require endocrine support to maintain a normal life. Thus, developing an effective intervention to prevent loss of the ovarian reserve is an unmet need for these cancer patients. The selection of adjuvant therapies to protect the ovarian reserve against cancer therapies underlies the mechanism of loss of primordial follicles (PFs). Several theories have been proposed to explain the loss of PFs. The "burn out" theory postulates that chemotherapeutic agents activate dormant PFs through an activation pathway. Another theory posits that chemotherapeutic agents destroy PFs through an "apoptotic pathway" due to high sensitivity to DNA damage. However, the mechanisms causing loss of the ovarian reserve remains largely speculative. Here, we review current literature in this area and consider the mechanisms of how gonadotoxic therapies deplete PFs in the ovarian reserve.

The Impact of Chemotherapy on the Ovaries: Molecular Aspects and the Prevention of Ovarian Damage

Cancer treatment, such as chemotherapy, induces early ovarian follicular depletion and subsequent infertility. In order to protect gametes from the gonadotoxic effects of chemotherapy, several fertility preservation techniques—such as oocyte or embryo cryopreservation with or without ovarian stimulation, or cryopreservation of the ovarian cortex—should be considered. However, these methods may be difficult to perform, and the future use of cryopreserved germ cells remains uncertain. Therefore, improving the methods currently available and developing new strategies to preserve fertility represent major challenges in the area of oncofertility. Animal and ovarian culture models have been used to decipher the effects of different cytotoxic agents on ovarian function and several theories regarding chemotherapy gonadotoxicity have been raised. For example, cytotoxic agents might (i) have a direct detrimental effect on the DNA of primordial follicles constituting the ovarian reserve and induce apoptosis; (ii) induce a massive growth of dormant follicles, which are then destroyed; or (ii) induce vascular ovarian damage. Thanks to improvements in the understanding of the mechanisms involved, a large number of studies have been carried out to develop molecules limiting the negative impact of chemotherapy on the ovaries.

Kinase-independent inhibition of cyclophosphamide-induced pathways protects the ovarian reserve and prolongs fertility

Premature ovarian failure and infertility are adverse effects of cancer therapies. The mechanism underlying chemotherapy-mediated depletion of the ovarian reserve remains unclear. Here, we aim to identify the signaling pathways involved in the loss of the ovarian reserve to prevent the damaging effects of chemotherapy. We evaluated the effects of cyclophosphamide, one of the most damaging chemotherapeutic drugs, against follicle reserve. In vivo studies showed that the cyclophosphamide-induced loss of ovarian reserve occurred through a sequential mechanism. Cyclophosphamide exposure induced the activation of both DNAPK-γH2AX-checkpoint kinase 2 (CHK2)-p53/TAp63α isoform and protein kinase B (AKT)-forkhead box O3 (FOXO3a) signaling axes in the nucleus of oocytes. Concomitant administration of an allosteric ABL inhibitor and cyclophosphamide modulated both pathways while protecting the ovarian reserve from chemotherapy assaults. As a consequence, the fertility of the treated mice was prolonged. On the contrary, the administration of an allosteric ABL activator enhanced the lethal effects of cyclophosphamide while shortening mouse fertility. Therefore, kinase-independent inhibition may serve as an effective ovarian-protective strategy in women under chemotherapy.