MicroRNA profiling and identification of let-7a as a target to prevent chemotherapy-induced primordial follicles apoptosis in mouse ovaries

The role of declining ataxia-telangiectasia-mutated (ATM) function in oocyte aging

Despite the advances in the understanding of reproductive physiology, the mechanisms underlying ovarian aging are still not deciphered. Recent research found an association between impaired ATM-mediated DNA double-strand break (DSB) repair mechanisms and oocyte aging. However, direct evidence connecting ATM-mediated pathway function decline and impaired oocyte quality is lacking. The objective of this study was to determine the role of ATM-mediated DNA DSB repair in the maintenance of oocyte quality in a mouse oocyte knockdown model. Gene interference, in vitro culture, parthenogenesis coupled with genotoxicity assay approaches, as well as molecular cytogenetic analyses based upon next-generation sequencing, were used to test the hypothesis that intact ATM function is critical in the maintenance of oocyte quality. We found that ATM knockdown impaired oocyte quality, resulting in poor embryo development. ATM knockdown significantly lowered or blocked the progression of meiosis in vitro, as well as retarding and reducing embryo cleavage after parthenogenesis. After ATM knockdown, all embryos were of poor quality, and none reached the blastocyst stage. ATM knockdown was also associated with an increased aneuploidy rate compared to controls. Finally, ATM knockdown increased the sensitivity of the oocytes to a genotoxic active metabolite of cyclophosphamide, with increased formation of DNA DSBs, reduced survival, and earlier apoptotic death compared to controls. These findings suggest a key role for ATM in maintaining oocyte quality and resistance to genotoxic stress, and that the previously observed age-induced decline in oocyte ATM function may be a prime factor contributing to oocyte aging.

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.

Overexpression of Let-7a mitigates diploidization in mouse androgenetic haploid embryonic stem cells

Mouse androgenetic haploid embryonic stem cells (mAG-haESCs) can be utilized to uncover gene functions, especially those of genes with recessive effects, and to produce semicloned mice when injected into mature oocytes. However, mouse haploid cells undergo rapid diploidization during long-term culture in vitro and subsequently lose the advantages of haploidy, and the factors that drive diploidization are poorly understood. In this study, we compared the small RNAs (sRNAs) of mAG-haESCs, normal embryonic stem cells (ESCs), and mouse round spermatids by high-throughput sequencing and identified distinct sRNA profiles. Several let-7 family members and miR-290-295 cluster microRNAs (miRNAs) were found significantly differentially transcribed. Knockdown and overexpression experiments showed that let-7a and let-7g suppress diploidization while miR-290a facilitates diploidization. Our study revealed the unique sRNA profile of mAG-haESCs and demonstrated that let-7a overexpression can mitigate diploidization in mAG-haESCs. These findings will help us to better understand mAG-haESCs and utilize them as tools in the future.

Research progress on the prevention and treatment of chemotherapy-induced ovarian damage

Chemotherapy is a main treatment option for malignant tumors, but it may cause various adverse effects, including dysfunction of female endocrine and fertility. Chemotherapy-induced ovarian damage has been concerned, apart from ovarian preservation, the prevention and treatment of ovarian dysfunction are widely studied. In this article, the mechanisms of ovarian injury caused by chemotherapy, including the apoptosis of follicle and supporting cells, follicle "burn out", ovarian stromal and microvascular damage; and influencing factors, including age at diagnosis and initial low pre-treatment anti-Müllerian hormone levels, toxicity, dose and regimen of chemotherapy drugs are reviewed based on the latest research results and clinical practice. The article also discusses measures and frontier therapies for prevention and treatment of ovarian injury, including the application of gonadotropin releasing hormone agonists or antagonists, tyrosine kinase inhibitors, antioxidants, sphingosine-1-phosphate, ceramide-1-phosphate, mammalian target of rapamycin inhibitors, granulocyte-colony stimulating factor, stem cell therapy and artificial ovary, etc.

Testicular niche repair after gonadotoxic treatments: Current knowledge and future directions

The testicular niche, which includes the germ cells, somatic cells, and extracellular matrix, plays a crucial role in maintaining the proper functions of the testis. Gonadotoxic treatments, such as chemotherapy and radiation therapy, have significantly improved the survival rates of cancer patients but have also been shown to have adverse effects on the testicular microenvironment. Therefore, repairing the testicular niche after gonadotoxic treatments is essential to restore its function. In recent years, several approaches, such as stem cell transplantation, gene therapy, growth factor therapy, and pharmacological interventions have been proposed as potential therapeutic strategies to repair the testicular niche. This comprehensive review aims to provide an overview of the current understanding of testis damage and repair mechanisms. We will cover a range of topics, including the mechanism of gonadotoxic action, repair mechanisms, and treatment approaches. Overall, this review highlights the importance of repairing the testicular niche after gonadotoxic treatments and identifies potential avenues for future research to improve the outcomes for cancer survivors.

Structural and Pharmacological Network Focused on MiRNAs Involved in Rheumatoid Arthritis: A Systematic Review

BACKGROUND

Rheumatoid Arthritis (RA) is a chronic autoimmune disease that has a prevalence of over one percent of the world population, causing substantial pain, joint deformity, and functional disability in patients. The identification and measurement of miRNAs are relatively easy to perform. Future studies will corroborate if miRNAs can fulfill their roles as biomarkers with either predictive or diagnostic evaluation of treatment potential and provide actual clinical utility.

METHODS

In the last decade, various advances have been made regarding the identification of the origin and exact functions of miRNAs, allowing us to have a potential use both in the research and clinical fields.

OBJECTIVE

This systematic review aimed to collect, analyze, and improve the current understanding of RA-related miRNAs and their applicability in therapeutics. A bibliographic search of the miRNAs involved in RA was carried out, and through the use of databases, their target genes and small molecules that had some relationship with their expression were searched. The analysis of these data was done through structural network analysis.

RESULTS

During the network analysis, miR-30a, miR-30c, let-7a, miR-144, miR-17-5p, miR-124, miR -23b, miR-23, miR-15a, miR-16 were the most connected, which could be used as possible biomarkers or be candidates for further analysis due to their interaction with other miRNAs and genes.

CONCLUSION

Additionally, this is the first systematic review, in which we proposed that small compounds like toxicants and drugs could have a potential role within RA because they regulate the expression of miRNAs involved in this pathology. Some of these compounds are commonly found as environmental contaminants, and others as drugs. These ideas open a new panorama of understanding RA, proposing possible causes or treatments against this pathology. Therefore, these small molecules would give us some indication of a relationship with RA, thereby helping in seeking causes, treatment, or prevention of this disease.

CONCLUSION

This is the first time it is intended to use structural network analysis to determine possible biomarkers of AR for diagnosis and prognosis through the expression of these miRNAs and their relationship with compounds of daily life.

The Role of microRNA in Spermatogenesis: Is There a Place for Fertility Preservation Innovation?

Oncological treatments have dramatically improved over the last decade, and as a result, survival rates for cancer patients have also improved. Quality of life, including concerns about fertility, has become a major focus for both oncologists and patients. While oncologic treatments are often highly effective at suppressing neoplastic growth, they are frequently associated with severe gonadotoxicity, leading to infertility. For male patients, the therapeutic option to preserve fertility is semen cryopreservation. In prepubertal patients, immature testicular tissue can be sampled and stored to allow post-cure transplantation of the tissue, immature germ cells, or in vitro spermatogenesis. However, experimental techniques have not yet been proven effective for restoring sperm production for these patients. MicroRNAs (miRNAs) have emerged as promising molecular markers and therapeutic tools in various diseases. These small regulatory RNAs possess the unique characteristic of having multiple gene targets. MiRNA-based therapeutics can, therefore, be used to modulate the expression of different genes involved in signaling pathways dysregulated by changes in the physiological environment (disease, temperature, ex vivo culture, pharmacological agents). This review discusses the possible role of miRNA as an innovative treatment option in male fertility preservation-restoration strategies and describes the diverse applications where these new therapeutic tools could serve as fertility protection agents.

LIN28 is essential for the maintenance of chicken primordial germ cells

Understanding the mechanism of stem cell maintenance underlies the establishment of long-term and mass culture methods for stem cells that are fundamental for clinical and agricultural applications. In this study, we use chicken primordial germ cell (PGC) as a model to elucidate the molecular mechanisms underlying stem cell maintenance. The PGC is a useful experimental model because it is readily gene-manipulatable and easy to test gene function in vivo using transplantation. Previous studies to establish a long-term culture system have shown that secreted factors such as FGF2 are required to maintain the self-renewal capability of PGC. On the other hand, we know little about intracellular regulators responsible for PGC maintenance. Among representative stem cell factors, we focus on RNA-binding factors LIN28A and LIN28B as possible central regulators for the gene regulatory network essential to PGC maintenance. By taking advantage of the CRISPR/Cas9-mediated gene editing and a clonal culture technique, we find that both LIN28A and LIN28B regulate the proliferation of PGC in vitro. We further showed that colonization efficiency of grafted PGC at the genital ridges, rudiments for the gonads, of chicken embryos were significantly decreased by knockout (KO) of LIN28A or LIN28B. Of note, overexpression of human LIN28 in LIN28-KO PGC was sufficient to restore the low colonization rates, suggesting that LIN28 plays a key role in PGC colonization at the gonads. Transcriptomic analyses of LIN28-KO PGC reveal that several genes related to mesenchymal traits are upregulated, including EGR1, a transcription factor that promotes the differentiation of mesodermal tissues. Finally, we show that the forced expression of human EGR1 deteriorates replication activity and colonization efficiency of PGCs. Taken together, this work demonstrates that LIN28 maintains self-renewal of PGC by suppressing the expression of differentiation genes including EGR1.

A Journey to Reach the Ovary Using Next-Generation Technologies

Although effective in terms of the chances of future live birth, the current methods for fertility preservation, such as oocyte, embryo, or ovarian tissue cryopreservation, cannot be offered to all cancer patients in all clinical contexts. Expanding options for fertility preservation is crucial to addressing the need to encompass all situations. One emerging strategy is pharmacoprotection, a non-invasive approach that has the potential to fill existing gaps in fertility preservation. In addition to the identification of the most effective therapeutic agents, the potential for off-target effects remains one of the main limitations of this strategy for clinical application, particularly when healthy ovarian tissue is targeted. This review focuses on the advances in pharmacoprotective approaches and the challenge of targeting the ovaries to deliver these agents. The unique properties of gold nanoparticles (AuNPs) make them an attractive candidate for this purpose. We discuss how AuNPs meet many of the requirements for an ideal drug delivery system, as well as the existing limitations that have hindered the progression of AuNP research into more clinical trials. Additionally, the review highlights microRNA (miRNA) therapy as a next-generation approach to address the issues of fertility preservation and discusses the obstacles that currently impede its clinical availability.

Regulation of follicular activation signaling pathways by in vitro inhibition of YAP/TAZ activity in mouse ovaries

The Hippo pathway plays a crucial role in the regulation of follicular activation, which constitutes the first step of the folliculogenesis process. Disruption of this pathway occurs in several non-physiological contexts, after fragmentation for ovarian tissue cryopreservation procedures or chemotherapy exposure, leading to massive follicular growth and depletion. This study aimed to investigate the effect of controlling the Hippo pathway using verteporfin (VERT) during in vitro ovarian culture and to evaluate its potential preventive effects on chemotherapy-induced follicle activation using a mouse model. After exposure of cut ovaries to different concentrations of VERT for 3 h, a dose-dependent effect of VERT was observed that reached significant inhibition of YAP activity at 3 µmol/L. To assess the potential effect of controlling chemotherapy-induced Hippo pathway disruption, whole mouse ovaries were exposed to VERT alone or as a co-treatment with 4-hydroperoxycylophosphamide (4HC). VERT co-treatment prevented chemotherapy-induced YAP activation but had a limited impact on downstream effector gene, Ccn2. Surprisingly, VERT co-treatment also prevented mTOR and survival signaling pathway alterations following chemotherapy exposure. These results suggest an interaction between the two main signaling pathways regulating follicle activation and a protective effect of VERT on 4HC-induced DNA damage.

PARP1-catalyzed PARylation of YY1 mediates endoplasmic reticulum stress in granulosa cells to determine primordial follicle activation

Although only a small number of primordial follicles are known to be selectively activated during female reproductive cycles, the mechanisms that trigger this recruitment remain largely uncharacterized. Misregulated activation of primordial follicles may lead to the exhaustion of the non-renewable pool of primordial follicles, resulting in premature ovarian insufficiency. Here, we found that poly(ADP-ribose) polymerase 1 (PARP1) enzymatic activity in the surrounding granulosa cells (GCs) in follicles determines the subpopulation of the dormant primordial follicles to be awakened. Conversely, specifically inhibiting PARP1 in oocytes in an in vitro mouse follicle reconstitution model does not affect primordial follicle activation. Further analysis revealed that PARP1-catalyzed transcription factor YY1 PARylation at Y185 residue facilitates YY1 occupancy at Grp78 promoter, a key molecular chaperone of endoplasmic reticulum stress (ERS), and promotes Grp78 transcription in GCs, which is required for GCs maintaining proper ERS during primordial follicle activation. Inhibiting PARP1 prevents the loss of primordial follicle pool by attenuating the excessive ERS in GCs under fetal bisphenol A exposure. Together, we demonstrate that PARP1 in GCs acts as a pivotal modulator to determine the fate of the primordial follicles and may represent a novel therapeutic target for the retention of primordial follicle pool in females.

Chemotherapy and female fertility

Chemotherapy to treat cancer is usually responsible for early ovarian follicle depletion. Ovarian damage induced by cancer treatments frequently results in infertility in surviving patients of childbearing age. Several fertility preservation techniques have been developed. Nowadays, oocyte or embryo cryopreservation with or without ovarian stimulation and cryopreservation of the ovarian cortex are the most commonly used. However, these methods may be difficult to implement in some situations, and subsequent use of the cryopreserved germ cells remains uncertain, with no guarantee of pregnancy. Improved knowledge of the molecular mechanisms and signaling pathways involved in chemotherapy-induced ovarian damage is therefore necessary, to develop new strategies for fertility preservation. The effects of various chemotherapies have been studied in animal models or in vitro on ovarian cultures, suggesting various mechanisms of gonadotoxicity. Today the challenge is to develop molecules and techniques to limit the negative impact of chemotherapy on the ovaries, using experimental models, especially in animals. In this review, the various theories concerning ovarian damage induced by chemotherapy will be reviewed and emerging approaches for ovarian protection will be explained.

Let-7a mimic transfection reduces chemotherapy-induced damage in a mouse ovarian transplantation model

Pharmacological approaches offer a non-invasive and promising option for fertility preservation in young female cancer patients undergoing gonadotoxic therapy. The GnRH-agonists are the only clinically available drugs in this indication, but their use and mechanisms of protection are still controversial. Recently, we have investigated new targeted drugs based on microRNA (miRNA) replacement therapy, and have identified the let-7a miRNA as candidate for fertility preservation strategies. Here, the effect of let-7a replacement during chemotherapy exposure on follicular growth and oocyte maturation capacity was investigated using a mouse ovarian-kidney transplantation model. Newborn mouse ovaries were cultured under different conditions; control, chemotherapy exposure (4-hydroperoxycyclophosphamide, 4-HC), and co-treatment with 4-HC and let-7a mimic transfection (4-HC + let-7a). The ovaries were then transplanted under the kidney capsule of recipient mice and follicular growth, survival, and oocyte in vitro maturation were assessed after 3 weeks. The results showed that the follicular pool was highest in the control group but higher in the 4-HC + let-7a group than the 4-HC group. DNA-damage/apoptosis ratios were higher in all 4-HC-exposed groups compared to control but were reduced in the 4-HC + let-7a group. In addition, the post-transplantation oocyte in vitro maturation rate was higher in the 4-HC + let-7a group compared to the 4-HC group, suggesting better oocyte quality. These results provide new information regarding the beneficial effects of let-7a replacement against chemotherapy-induced ovarian damage and open new perspectives for future in vivo applications.

A robust biostatistical method leverages informative but uncertainly determined qPCR data for biomarker detection, early diagnosis, and treatment

As a common medium-throughput technique, qPCR (quantitative real-time polymerase chain reaction) is widely used to measure levels of nucleic acids. In addition to accurate and complete data, experimenters have unavoidably observed some incomplete and uncertainly determined qPCR data because of intrinsically low overall amounts of biological materials, such as nucleic acids present in biofluids. When there are samples with uncertainly determined qPCR data, some investigators apply the statistical complete-case method by excluding the subset of samples with uncertainly determined data from analysis (CO), while others simply choose not to analyze (CNA) these datasets altogether. To include as many observations as possible in analysis for interesting differential changes between groups, some investigators set incomplete observations equal to the maximum quality qPCR cycle (MC), such as 32 and 40. Although straightforward, these methods may decrease the sample size, skew the data distribution, and compromise statistical power and research reproducibility across replicate qPCR studies. To overcome the shortcomings of the existing, commonly-used qPCR data analysis methods and to join the efforts in advancing statistical analysis in rigorous preclinical research, we propose a robust nonparametric statistical cycle-to-threshold method (CTOT) to analyze incomplete qPCR data for two-group comparisons. CTOT incorporates important characteristics of qPCR data and time-to-event statistical methodology, resulting in a novel analytical method for qPCR data that is built around good quality data from all subjects, certainly determined or not. Considering the benchmark full data (BFD), we compared the abilities of CTOT, CO, MC, and CNA statistical methods to detect interesting differential changes between groups with informative but uncertainly determined qPCR data. Our simulations and applications show that CTOT improves the power of detecting and confirming differential changes in many situations over the three commonly used methods without excess type I errors. The robust nonparametric statistical method of CTOT helps leverage qPCR technology and increase the power to detect differential changes that may assist decision making with respect to biomarker detection and early diagnosis, with the goal of improving the management of patient healthcare.

Unraveling the mechanisms of chemotherapy-induced damage to human primordial follicle reserve: road to developing therapeutics for fertility preservation and reversing ovarian aging

Among the investigated mechanisms of chemotherapy-induced damage to human primordial follicle reserve are induction of DNA double-strand breaks (DSBs) and resultant apoptotic death, stromal-microvascular damage and follicle activation. Accumulating basic and translational evidence suggests that acute exposure to gonadotoxic chemotherapeutics, such as cyclophosphamide or doxorubicin, induces DNA DSBs and triggers apoptotic death of primordial follicle oocytes within 12-24 h, resulting in the massive loss of ovarian reserve. Evidence also indicates that chemotherapeutic agents can cause microvascular and stromal damage, induce hypoxia and indirectly affect ovarian reserve. While it is possible that the acute reduction of the primordial follicle reserve by massive apoptotic losses may result in delayed activation of some primordial follicles, this is unlikely to be a predominant mechanism of loss in humans. Here, we review these mechanisms of chemotherapy-induced ovarian reserve depletion and the potential reasons for the discrepancies among the studies. Based on the current literature, we propose an integrated hypothesis that explains both the acute and delayed chemotherapy-induced loss of primordial follicle reserve in the human ovary.

Integrated analysis of miRNA-mRNA interaction in ovaries of Turpan Black Sheep during follicular and luteal phases

To investigate the regulatory mechanism of the follicular-luteal phase transition in Turpan black sheep (Ovis aries), the genome-wide expression patterns of microRNAs (miRNAs) and genes were investigated in ovaries of six sheep (3 years and single lamb with 3 consecutive births) during follicular and luteal phases of the oestrous cycle. Bioinformatic analysis was used to screen potential miRNAs and genes related to Turpan black sheep ovarian function. RT-qPCR was used to validate the sequencing results. In total, we identified 139 known and 71 novel miRNAs in the two phases with miRNA-seq, and a total of 19 miRNAs were significantly differentially expressed, of which 7 were up-regulated and 12 were down-regulated in the follicular phase compared with luteal phase. A total of 150 genes were significantly differentially expressed, including 63 up-regulated and 87 down-regulated in the follicular phase compared with the luteal phase by RNA-seq data analysis. Those DEGs were significantly enriched in 103 GO terms and several KEGG pathways, including metabolic pathway, ovarian steroidogenesis, steroid hormone biosynthesis and oestrogen signalling pathway. In addition, we created a miRNA-mRNA regulatory network to further elucidate the mechanism of follicular-luteal transition. Finally, we identified key miRNAs and genes including miR-143, miR-99a, miR-150, miR-27a, miR-125b, STAR, STAT1, which might play crucial roles in reproductive hormone biosynthesis and follicular development. The miRNA-mRNA interactive network clearly illustrates molecular basis involving in follicular-luteal transition.

Slow-Freezing Cryopreservation Ensures High Ovarian Tissue Quality Followed by In Vivo and In Vitro Methods and Is Safe for Fertility Preservation

Background and objectives: Cancer incidence is growing with younger patients diagnosed with this disease every year. Improved cancer diagnostics and treatment lead to better survival of cancer patients. However, after aggressive chemo- or radiotherapy, cancer survivors suffer from various degrees of subfertility or infertility. Several fertility preservation technologies have been developed for young cancer patients: cryopreservation of germ cells, embryos, or reproductive tissues. The best results have been shown by cryopreservation of sperm and embryos. Yet the success of using cryopreserved oocytes or reproductive tissues (ovarian and testicular) is still insufficient. Therefore, this study was designed to assess the vitality, viability, general quality, and safety of frozen-thawed human ovarian tissue for retransplantation using modern molecular tests. Materials and Methods: The new miRNA array test was used to evaluate miRNA expression in thawed ovarian tissue in combination with standard xenotransplantation and pathological examination of microslides. Results: Our results demonstrated that slow freezing is an efficient way (80%) to cryopreserve ovarian tissue with no structural damage afterwards. We have shown that xenotransplantation into immunodeficient mice, histology, and immunohistochemistry could be potentially replaced by more recent molecular methods. Conclusions: The latter method has shown that altered expression of miRNAs might be used as identifiers of normal/damaged tissue after further analysis. Newer, safer, and more specific approaches need to be developed in order to eliminate the risk of disease reoccurrence.

Reproducibility challenges for biomarker detection with uncertain but informative experimental data

Recent studies have revealed that circulating microRNAs are promising biomarkers for detecting toxicity or disease. Quantitative real-time polymerase chain reaction (qPCR) is often used to measure the levels of microRNAs. Besides complete and certain data, investigators inevitably have observed technically incomplete or uncertain qPCR data. Investigators usually set incomplete observations equal to the maximum quality number of qPCR cycles, apply the complete-observation method, or choose not to analyze targets with incomplete observations. Using biostatistical knowledge and published studies, we show that three commonly applied methods tend to cause biased inference and decrease reproducibility in biomarker detection. More efforts are needed to address the challenges to identify and detect reliable, novel circulating biomarkers in liquid biopsies.

Exposure to Chemotherapy During Childhood or Adulthood and Consequences on Spermatogenesis and Male Fertility

Over the last decade, the number of cancer survivors has increased thanks to progress in diagnosis and treatment. Cancer treatments are often accompanied by adverse side effects depending on the age of the patient, the type of cancer, the treatment regimen, and the doses. The testicular tissue is very sensitive to chemotherapy and radiotherapy. This review will summarize the epidemiological and experimental data concerning the consequences of exposure to chemotherapy during the prepubertal period or adulthood on spermatogenic progression, sperm production, sperm nuclear quality, and the health of the offspring. Studies concerning the gonadotoxicity of anticancer drugs in adult survivors of childhood cancer are still limited compared with those concerning the effects of chemotherapy exposure during adulthood. In humans, it is difficult to evaluate exactly the toxicity of chemotherapeutic agents because cancer treatments often combine chemotherapy and radiotherapy. Thus, it is important to undertake experimental studies in animal models in order to define the mechanism involved in the drug gonadotoxicity and to assess the effects of their administration alone or in combination on immature and mature testis. These data will help to better inform cancer patients after recovery about the risks of chemotherapy for their future fertility and to propose fertility preservation options.

Crosstalk between PTEN/PI3K/Akt Signalling and DNA Damage in the Oocyte: Implications for Primordial Follicle Activation, Oocyte Quality and Ageing

The preservation of genome integrity in the mammalian female germline from primordial follicle arrest to activation of growth to oocyte maturation is fundamental to ensure reproductive success. As oocytes are formed before birth and may remain dormant for many years, it is essential that defence mechanisms are monitored and well maintained. The phosphatase and tensin homolog of chromosome 10 (PTEN)/phosphatidylinositol 3-kinase (PI3K)/protein kinase B (PKB, Akt) is a major signalling pathway governing primordial follicle recruitment and growth. This pathway also contributes to cell growth, survival and metabolism, and to the maintenance of genomic integrity. Accelerated primordial follicle activation through this pathway may result in a compromised DNA damage response (DDR). Additionally, the distinct DDR mechanisms in oocytes may become less efficient with ageing. This review considers DNA damage surveillance mechanisms and their links to the PTEN/PI3K/Akt signalling pathway, impacting on the DDR during growth activation of primordial follicles, and in ovarian ageing. Targeting DDR mechanisms within oocytes may be of value in developing techniques to protect ovaries against chemotherapy and in advancing clinical approaches to regulate primordial follicle activation.

Oncofertility: Pharmacological Protection and Immature Testicular Tissue (ITT)-Based Strategies for Prepubertal and Adolescent Male Cancer Patients

While the incidence of cancer in children and adolescents has significantly increased over the last decades, improvements made in the field of cancer therapy have led to an increased life expectancy for childhood cancer survivors. However, the gonadotoxic effect of the treatments may lead to infertility. Although semen cryopreservation represents the most efficient and safe fertility preservation method for males producing sperm, it is not feasible for prepubertal boys. The development of an effective strategy based on the pharmacological protection of the germ cells and testicular function during gonadotoxic exposure is a non-invasive preventive approach that prepubertal boys could benefit from. However, the progress in this field is slow. Currently, cryopreservation of immature testicular tissue (ITT) containing spermatogonial stem cells is offered to prepubertal boys as an experimental fertility preservation strategy by a number of medical centers. Several in vitro and in vivo fertility restoration approaches based on the use of ITT have been developed so far with autotransplantation of ITT appearing more promising. In this review, we discuss the pharmacological approaches for fertility protection in prepubertal and adolescent boys and the fertility restoration approaches developed on the utilization of ITT.

Answer to Controversy: miR-10a Replacement Approaches Do Not Offer Protection against Chemotherapy-Induced Gonadotoxicity in Mouse Model

It is well known that chemotherapeutic agents may lead to premature ovarian failure and infertility. Therefore, fertility preservation is highly recommended for female cancer survivors. Despite the currently available techniques, new, non-invasive methods need to be developed to protect the ovarian follicles during oncological treatments. MicroRNAs can be effective tools in this field, as they alter their expression during chemotherapy exposure, and hence they can be useful to minimize the off-target toxicity. Previously, we identified several miRNAs with an important role in newborn mouse ovaries exposed to chemotherapy; among them, the miR-10a was one of the most downregulated miRNAs. Given the controversial role of miR-10a in the ovarian function, we decided to investigate its implication in chemotherapy-induced gonadotoxicity. The downregulated levels of miR-10a were restored by a liposome system conjugated with a mimic miR-10a, and the overexpressed miR-10a prevented the upregulation of the targeted gene, phosphatase and tensin homolog (Pten). The apoptosis was evaluated by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) Assay and Bax expression quantification, while histological studies were also performed to evaluate the follicle count and development. Our results showed that the miR-10a replacement could not protect the ovaries from chemotherapy-induced apoptosis, whereas the targeting of Pten may affect the follicle activation via the phosphoinositide 3-kinase (PI3K)/PTEN/protein kinase B (AKT) pathway. Consequently, the application of miR-10a in fertility preservation is not recommended, and the role of miR-10a needs to be further elucidated.