Chemotherapy-induced late transgenerational effects in mice

Human adipose-derived stromal cells transplantation prolongs reproductive lifespan on mouse models of mild and severe premature ovarian insufficiency

Background

Although recent studies have investigated the ability of Mesenchymal Stromal Cells (MSCs) to alleviate short-term ovarian damage in animal models of chemotherapy-induced Premature Ovarian Insufficiency (POI), no data are available on reproductive lifespan recovery, especially in a severe POI condition. For this reason, we investigated the potential of MSCs isolated from human adipose tissue (hASCs), since they are easy to harvest and abundant, in ameliorating the length and performance of reproductive life in both mild and severe chemotherapy-induced murine POI models.

Methods

Mild and severe POI models were established by intraperitoneally administering a light (12 mg/kg busulfan + 120 mg/kg cyclophosphamide) or heavy (30 mg/kg busulfan + 120 mg/kg cyclophosphamide) dose of chemotherapy, respectively, in CD1 mice. In both cases, a week later, 1 × 10⁶ hASCs were transplanted systemically through the tail vein. After four additional weeks, some females were sacrificed to collect ovaries for morphological evaluation. H&E staining was performed to assess stroma alteration and to count follicle numbers; immunofluorescence staining for αSMA was used to analyse vascularization. Of the remaining females, some were mated after superovulation to collect 2-cell embryos in order to evaluate their pre-implantation developmental capacity in vitro, while others were naturally mated to monitor litters and reproductive lifespan length. F1 litters’ weight, ovaries and reproductive lifespan were also analysed.

Results

hASC transplantation alleviated ovarian weight loss and size decrease and reduced alterations on ovarian stroma and vasculature, concurrently preventing the progressive follicle stockpile depletion caused by chemotherapy. These effects were associated with the preservation of the oocyte competence to develop into blastocyst in vitro and, more interestingly, with a significant decrease of chemotherapy-induced POI features, like shortness of reproductive lifespan, reduced number of litters and longer time to plug (the latter only presented in the severe POI model).

Conclusion

Human ASC transplantation was able to significantly reduce all the alterations induced by the chemotherapeutic treatment, while improving oocyte quality and prolonging reproductive functions, thus counteracting infertility. These results, strengthened by the use of an outbred model, support the potential applications of hASCs in women with POI, nowadays mainly induced by anticancer therapies.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02590-5.

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.

Impact of chemotherapy on subsequent generations

Chemotherapy is extensively used in healthcare and its usage is only increasing. Since DNA and DNA modifiers (epigenetics) are altered by chemotherapy, the long-term effects in exposed individuals are important to clinicians and researchers. For example, animal studies have shown evidence of both genetic and epigenetic changes in progeny several generations downstream from the initial exposure. At present, there is extremely limited available research in humans but the study of the generational effects of chemotherapy could prove to be significant.

Novel insights into the pathophysiology of chemotherapy-induced damage to the ovary

Cancer is the second leading cause of death in the USA and is considered a public health issue worldwide. Early diagnosis and advancement of treatment modalities contributed to declining mortality rates. Consequently, survival rates increased, leading to a greater interest in maintaining the quality of life after cancer treatment. Overall survival and disease-free survival rates are improved with the use of adjuvant chemotherapy. However, chemotherapy treatment might cause short and long-term side effects for cancer survivors. A special concern of young women diagnosed with cancer is their reproductive potential after chemotherapy. Chemotherapy drugs act by distinct mechanisms in the ovaries. DNA damage of primordial follicle oocytes, leading to chemotherapy-induced apoptosis, was recognized as the principal mechanism responsible for the irreversible decline of the ovarian reserve. The oocyte first attempts to repair DNA damage via the DNA damage repair pathway mediated by ataxia-telangiectasia mutated. Elimination through apoptosis occurs in cells in which DNA damage could not be repaired. In this review, the clinical impact and the major mechanisms of ovarian damage from chemotherapy treatment will be briefly described.

Loss of PUMA protects the ovarian reserve during DNA-damaging chemotherapy and preserves fertility

Female gametes are stored in the ovary in structures called primordial follicles, the supply of which is non-renewable. It is well established that DNA-damaging cancer treatments can deplete the ovarian reserve of primordial follicles, causing premature ovarian failure and infertility. The precise mechanisms underlying this chemotherapy-driven follicle loss are unclear, and this has limited the development of targeted ovarian-protective agents. To address this fundamental knowledge gap, we used gene deletion mouse models to examine the role of the DNA damage-induced pro-apoptotic protein, PUMA, and its transcriptional activator TAp63, in primordial follicle depletion caused by treatment with cyclophosphamide or cisplatin. Cyclophosphamide caused almost complete destruction of the primordial follicle pool in adult wild-type (WT) mice, and a significant destructive effect was also observed for cisplatin. In striking contrast, Puma-/- mice retained 100% of their primordial follicles following either genotoxic treatment. Furthermore, elimination of PUMA alone completely preserved fertility in cyclophosphamide-treated mice, indicating that oocytes rescued from DNA damage-induced death can repair themselves sufficiently to support reproductive function and offspring health. Primordial follicles were also protected in TAp63-/- mice following cisplatin treatment, but not cyclophosphamide, suggesting mechanistic differences in the induction of apoptosis and depletion of the ovarian reserve in response to these different chemotherapies. These studies identify PUMA as a crucial effector of apoptosis responsible for depletion of primordial follicles following exposure to cyclophosphamide or cisplatin, and this indicates that inhibition of PUMA may be an effective ovarian-protective strategy during cancer treatment in women.

Increased incidence of inguinal hernia in offspring of female survivors of childhood central nervous system tumors

Female survivors of childhood central nervous system (CNS) tumors experience an increased risk of infertility and various pregnancy complications. We aimed to explore whether the incidence of inguinal hernia could be higher in offspring of female CNS tumor survivors as compared to the general population. Girls who were younger than 15 years of age and diagnosed with CNS tumors between 1958 and 2013 were identified from the Swedish Cancer Registry. By linking with the Swedish Medical Birth Registry, we identified 580 children who were born to mothers of CNS tumor survivors. After 9,662 person-years of follow-up, 23 of them were diagnosed with inguinal hernia, giving an incidence rate (IR) of 2.4 per 1,000 person-years, whereas the IR was 1.2 for the matched controls. Cox regression analysis was used to calculate the hazard ratio (HR) of inguinal hernia. After adjusting for some confounding factors, the incidence of inguinal hernia was significantly increased with an HR of 1.92 (95%CI 1.08-3.41). The association was predominant in offspring whose mothers were diagnosed with CNS tumors at the age of 10 and older, and with CNS tumors located in the brain.

Fertility preservation for patients with hematologic malignancies: The Korean Society for Fertility Preservation clinical guidelines

Although the survival rate of hematologic malignancies in young patients is very high, cytotoxic therapies such as chemotherapy and total body irradiation therapy can significantly reduce a patient's reproductive capacity and cause irreversible infertility. Early ovarian failure also commonly occurs following additional cancer treatment, bone marrow transplantation, or autologous transplantation. Because the risk of early ovarian failure depends on the patient's circumstances, patients with a hematologic malignancy must consult health professionals regarding fertility preservation before undergoing treatments that can potentially damage their ovaries. While it is widely known that early menopause commonly occurs following breast cancer treatment, there is a lack of reliable study results regarding fertility preservation during hematologic malignancy treatment. Therefore, an in-depth discussion between patients and health professionals about the pros and cons of the various options for fertility preservation is necessary. In this study, we review germ cell toxicity, which occurs during the treatment of hematologic malignancies, and propose guidelines for fertility preservation in younger patients with hematologic malignancies.

Under-reporting of Adverse Events in the Biomedical Literature

Purpose

To address the under-reporting of research results, with emphasis on the under-reporting/distorted reporting of adverse events in the biomedical research literature.

Design/methodology/approach

A four-step approach is used: (1) To identify the characteristics of literature that make it adequate to support policy; (2) to show how each of these characteristics becomes degraded to make inadequate literature; (3) to identify incentives to prevent inadequate literature; and (4) to show policy implications of inadequate literature.

Findings

This review has provided reasons for, and examples of, adverse health effects of myriad substances (1) being under-reported in the premiere biomedical literature, or (2) entering this literature in distorted form. Since there is no way to gauge the extent of this under/distorted-reporting, the quality and credibility of the ‘premiere’ biomedical literature is unknown. Therefore, any types of meta-analyses or scientometric analyses of this literature will have unknown quality and credibility. The most sophisticated scientometric analysis cannot compensate for a highly flawed database.

Research limitations

The main limitation is in identifying examples of under-reporting. There are many incentives for under-reporting and few dis-incentives.

Practical implications

Almost all research publications, addressing causes of disease, treatments for disease, diagnoses for disease, scientometrics of disease and health issues, and other aspects of healthcare, build upon previous healthcare-related research published. Many researchers will not have laboratories or other capabilities to replicate or validate the published research, and depend almost completely on the integrity of this literature. If the literature is distorted, then future research can be misguided, and health policy recommendations can be ineffective or worse.

Originality/value

This review has examined a much wider range of technical and non-technical causes for under-reporting of adverse events in the biomedical literature than previous studies.

Differential DNA Methylation Regions in Adult Human Sperm following Adolescent Chemotherapy: Potential for Epigenetic Inheritance

BACKGROUND

The potential that adolescent chemotherapy can impact the epigenetic programming of the germ line to influence later life adult fertility and promote epigenetic inheritance was investigated. Previous studies have demonstrated a number of environmental exposures such as abnormal nutrition and toxicants can promote sperm epigenetic changes that impact offspring.

METHODS

Adult males approximately ten years after pubertal exposure to chemotherapy were compared to adult males with no previous exposure. Sperm were collected to examine differential DNA methylation regions (DMRs) between the exposed and control populations. Gene associations and correlations to genetic mutations (copy number variation) were also investigated.

METHODS AND FINDINGS

A signature of statistically significant DMRs was identified in the chemotherapy exposed male sperm. The DMRs, termed epimutations, were found in CpG desert regions of primarily 1 kilobase size. Observations indicate adolescent chemotherapy exposure can promote epigenetic alterations that persist in later life.

CONCLUSIONS

This is the first observation in humans that an early life chemical exposure can permanently reprogram the spermatogenic stem cell epigenome. The germline (i.e., sperm) epimutations identified suggest chemotherapy has the potential to promote epigenetic inheritance to the next generation.

Chemotherapy-induced damage to ovary: mechanisms and clinical impact

Cancer is a major public health problem around the world. Currently, about 5% of women diagnosed with cancer are of reproductive age. These young survivors may face compromised fertility. The effects of chemotherapeutic agents on ovarian reserve and its clinical consequences are generally inferred from a variety of surrogate markers of ovarian reserve, all aiming to provide prognostic information on fertility or the likelihood of success of infertility treatment. Until recently, the mechanisms that are responsible for chemotherapy-induced ovarian damage were not fully elucidated. The understanding of these mechanisms may lead to targeted treatments to preserve fertility. In this manuscript, we will review the current knowledge on the mechanism of ovarian damage and clinical impact of chemotherapy agents on fertility.

History of ABVD alters the number of oocytes vitrified after in vitro maturation in fertility preservation candidates

AIM

This retrospective case-control study aimed at analyzing the results of in vitro maturation (IVM) of oocytes, used for fertility preservation (FP), in patients with history of ABVD (adriamycin, bleomycin, vinblastine and dacarbazine) for classical Hodgkin lymphoma.

PATIENTS & METHODS

A total of 22 candidates for FP, having received ABVD at least 2 years before IVM for FP were studied. IVM results were compared with those of 44 breast cancer patients, without history of chemotherapy, matched for ovarian reserve parameters.

RESULTS

The number of cumulo-oocyte complexes recovered and the total number of matured oocytes vitrified was lower in patients having received AVBD (5.5 ± 4.8 vs 8.5 ± 4.4 oocytes; p = 0.03 and 3.5 ± 3.7 vs 6 ± 3.0 oocytes; p < 0.04, respectively).

CONCLUSION

In light of these results, FP should be discussed before ABVD.

Cancer and fertility preservation: international recommendations from an expert meeting

In the last years, thanks to the improvement in the prognosis of cancer patients, a growing attention has been given to the fertility issues. International guidelines on fertility preservation in cancer patients recommend that physicians discuss, as early as possible, with all patients of reproductive age their risk of infertility from the disease and/or treatment and their interest in having children after cancer, and help with informed fertility preservation decisions. As recommended by the American Society of Clinical Oncology and the European Society for Medical Oncology, sperm cryopreservation and embryo/oocyte cryopreservation are standard strategies for fertility preservations in male and female patients, respectively; other strategies (e.g. pharmacological protection of the gonads and gonadal tissue cryopreservation) are considered experimental techniques. However, since then, new data have become available, and several issues in this field are still controversial and should be addressed by both patients and their treating physicians.In April 2015, physicians with expertise in the field of fertility preservation in cancer patients from several European countries were invited in Genova (Italy) to participate in a workshop on the topic of "cancer and fertility preservation". A total of ten controversial issues were discussed at the conference. Experts were asked to present an up-to-date review of the literature published on these topics and the presentation of own unpublished data was encouraged. On the basis of the data presented, as well as the expertise of the invited speakers, a total of ten recommendations were discussed and prepared with the aim to help physicians in counseling their young patients interested in fertility preservation.Although there is a great interest in this field, due to the lack of large prospective cohort studies and randomized trials on these topics, the level of evidence is not higher than 3 for most of the recommendations highlighting the need of further research efforts in many areas of this field. The participation to the ongoing registries and prospective studies is crucial to acquire more robust information in order to provide evidence-based recommendations.

Dexrazoxane Diminishes Doxorubicin-Induced Acute Ovarian Damage and Preserves Ovarian Function and Fecundity in Mice

Advances in cancer treatment utilizing multiple chemotherapies have dramatically increased cancer survivorship. Female cancer survivors treated with doxorubicin (DXR) chemotherapy often suffer from an acute impairment of ovarian function, which can persist as long-term, permanent ovarian insufficiency. Dexrazoxane (Dexra) pretreatment reduces DXR-induced insult in the heart, and protects in vitro cultured murine and non-human primate ovaries, demonstrating a drug-based shield to prevent DXR insult. The present study tested the ability of Dexra pretreatment to mitigate acute DXR chemotherapy ovarian toxicity in mice through the first 24 hours post-treatment, and improve subsequent long-term fertility throughout the reproductive lifespan. Adolescent CD-1 mice were treated with Dexra 1 hour prior to DXR treatment in a 1:1 mg or 10:1 mg Dexra:DXR ratio. During the acute injury period (2-24 hours post-injection), Dexra pretreatment at a 1:1 mg ratio decreased the extent of double strand DNA breaks, diminished γH2FAX activation, and reduced subsequent follicular cellular demise caused by DXR. In fertility and fecundity studies, dams pretreated with either Dexra:DXR dose ratio exhibited litter sizes larger than DXR-treated dams, and mice treated with a 1:1 mg Dexra:DXR ratio delivered pups with birth weights greater than DXR-treated females. While DXR significantly increased the "infertility index" (quantifying the percentage of dams failing to achieve pregnancy) through 6 gestations following treatment, Dexra pretreatment significantly reduced the infertility index following DXR treatment, improving fecundity. Low dose Dexra not only protected the ovaries, but also bestowed a considerable survival advantage following exposure to DXR chemotherapy. Mouse survivorship increased from 25% post-DXR treatment to over 80% with Dexra pretreatment. These data demonstrate that Dexra provides acute ovarian protection from DXR toxicity, improving reproductive health in a mouse model, suggesting this clinically available drug may provide ovarian protection for cancer patients.

Bortezomib prevents acute doxorubicin ovarian insult and follicle demise, improving the fertility window and pup birth weight in mice

Increasing numbers of female patients survive cancer, but succumb to primary ovarian insufficiency after chemotherapy. We tested the hypothesis that Bortezomib (Bort) protects ovaries from doxorubicin (DXR) chemotherapy by treating female mice with Bort 1 hour prior to DXR. By preventing DXR accumulation in the ovary, Bort attenuated DXR-induced DNA damage in all ovarian cell types, subsequent γH2AFX phosphorylation, and resulting apoptosis in preantral follicles. Bort pretreatment extended the number of litters per mouse, improved litter size and increased pup weight following DXR treatment, thus increasing the duration of post-chemotherapy fertility and improving pup health. As a promising prophylactic ovoprotective agent, Bort does not interfere with cancer treatment, and is currently used as a chemotherapy adjuvant. Bort-based chemoprotection may preserve ovarian function in a non-invasive manner that avoids surgical ovarian preservation, thus diminishing the health complications of premature menopause following cancer treatment.

Fertility preservation in young females with hematological malignancies

Impaired reproductive function and possible infertility are major concerns in long-term survivors of hematological malignancies. The ongoing increase in the survival rates of these patients is therefore accompanied with a growing demand for effective, safe and specifically tailored fertility preservation options. When approaching patients facing hematological malignancy, an individual evaluation of potential infertility risks and possible preventive or preserving measures should be performed. This review aims to provide up-to-date knowledge on female reproductive risks, and ovarian, uterine and genital injuries associated with therapy regimens currently used in hemato-oncological disorders. Recent progress in fertility preservation methods including ovarian tissue cryopreservation and transplantation, egg and embryo freezing, ovarian transposition and their specific role in hematological disorders are presented. The efficacy of these methods, possible risks and future challenges are critically discussed.

Prevention of chemotherapy-induced ovarian damage: possible roles for hormonal and non-hormonal attenuating agents

BACKGROUND

Current options for female fertility preservation in the face of cytotoxic treatments include embryo, oocyte and ovarian tissue cryopreservation. However these methods are limited by the patient age, status or available timeframe before treatment and they necessitate invasive procedures. Agents which can prevent or attenuate the ovotoxic effects of treatment would provide significant advantages over the existing fertility preservation techniques, and would allow patients to retain their natural fertility without the necessity for costly, invasive and risky procedures. Recent studies have contributed to our understanding of the mechanisms involved in cytotoxicity-induced ovarian follicle loss and highlight a number of agents that may be able to prevent or reduce this loss.

METHODS

This paper reviews the relevant literature (research articles published in English up to December 2013) on the mechanisms of cytotoxic-induced ovarian damage and the implications for fertility preservation. We present a comprehensive discussion of the potential agents that have been shown to preserve the ovarian follicle reserve in the face of cytotoxic treatments, including an analysis of their respective advantages and risks, and mechanisms of action.

RESULTS

Multiple molecular pathways are involved in the cellular response to cytotoxic treatments, and specific cellular reactions depend on variables including the drug class and dose, cell type, and cell stage. A number of agents acting on different elements of these pathways have demonstrated potential for preventing or reducing ovarian follicle loss, although in most cases, the studies are still very preliminary.

CONCLUSIONS

Advances in our understanding of the mechanisms and pathways involved in both cytotoxic ovarian damage and follicle growth and development have opened up new directions for fertility preservation. In order to bring these agents from the lab to the clinic, it will be vital to accurately evaluate the efficacy of each agent and additionally to demonstrate that co-treatment with these agents will not interfere with the anti-cancer activity of the chemotherapy drugs, or produce genetically comprised embryos.

Environmental epigenetics and phytoestrogen/phytochemical exposures

One of the most important environmental factors to promote epigenetic alterations in an individual is nutrition and exposure to plant compounds. Phytoestrogens and other phytochemicals have dramatic effects on cellular signaling events, so have the capacity to dramatically alter developmental and physiological events. Epigenetics provides one of the more critical molecular mechanisms for environmental factors such as phytoestrogens/phytochemicals to influence biology. In the event these epigenetic mechanisms become heritable through epigenetic transgenerational mechanisms the impacts on the health of future generations and areas such as evolutionary biology need to be considered. The current review focuses on available information on the environmental epigenetics of phytoestrogen/phytochemical exposures, with impacts on health, disease and evolutionary biology considered. This article is part of a Special Issue entitled 'Phytoestrogens'.

Ovarian tissue cryopreservation and transplantation: a realistic, effective technology for fertility preservation

It is clear that ovarian tissue cryopreservation can serve a very important role in providing fertility preservation. To date, more than 30 live human births have resulted from the transplantation of cryopreserved ovarian tissue, proving the successful implementation of this technique. The ideal conditions for ovarian tissue cryopreservation have yet to be determined, indicating the crucial need for more research in this field. Nonetheless, it is recommended that ovarian tissue cryopreservation be offered as an option to women before undergoing chemotherapy treatment in instances where there is no time to delay for hormonal stimulation and oocyte retrieval.

Biomarkers of chemotherapy-induced testicular damage

Increasing numbers of men are having or wanting children after chemotherapy treatment. This can be attributed to improvements in cancer therapies that increase survival. However, a side effect of most chemotherapy drugs is disruption of spermatogenesis and a drastic reduction in sperm count and quality. Although many men eventually recover reproductive function, as indicated by normal semen analyses, there is no clinical test that can assess sperm quality at a high level of sensitivity. Sperm fluorescent in situ hybridization (i.e., FISH) and several different tests for deoxyribonucleic acid (DNA) fragmentation have been used infrequently in clinical assessment. Animal models of chemotherapy-induced testicular damage are currently being used to identify potential molecular biomarkers that may be translatable to humans-these include sperm messenger RNAs, microRNAs, histone modifications, and DNA methylation patterns. Changes in these molecular measurements are quantitative and sensitive, potentially making them important clinical biomarkers of testicular function after chemotherapy treatment.

The dynamics of the primordial follicle reserve

The female germline comprises a reserve population of primordial (non-growing) follicles containing diplotene oocytes arrested in the first meiotic prophase. By convention, the reserve is established when all individual oocytes are enclosed by granulosa cells. This commonly occurs prior to or around birth, according to species. Histologically, the ‘reserve’ is the number of primordial follicles in the ovary at any given age and is ultimately depleted by degeneration and progression through folliculogenesis until exhausted. How and when the reserve reaches its peak number of follicles is determined by ovarian morphogenesis and germ cell dynamics involving i) oogonial proliferation and entry into meiosis producing an oversupply of oocytes and ii) large-scale germ cell death resulting in markedly reduced numbers surviving as the primordial follicle reserve. Our understanding of the processes maintaining the reserve comes primarily from genetically engineered mouse models, experimental activation or destruction of oocytes, and quantitative histological analysis. As the source of ovulated oocytes in postnatal life, the primordial follicle reserve requires regulation of i) its survival or maintenance, ii) suppression of development (dormancy), and iii) activation for growth and entry into folliculogenesis. The mechanisms influencing these alternate and complex inter-related phenomena remain to be fully elucidated. Drawing upon direct and indirect evidence, we discuss the controversial concept of postnatal oogenesis. This posits a rare population of oogonial stem cells that contribute new oocytes to partially compensate for the age-related decline in the primordial follicle reserve.

Emergency IVF versus ovarian tissue cryopreservation: decision making in fertility preservation for female cancer patients

Hundreds of thousands of women in their reproductive years are diagnosed with cancer each year. As the number of female patients who survive cancer increases, the demand for effective and individualized fertility preservation options grows. Currently there are limited clinical options for fertility preservation, and the paucity of publications describing clinical experience and outcomes data has limited accessibility to these options. Decision making for patients diagnosed with cancer requires up-to-date knowledge of the efficacy and safety of available techniques. This article describes a step-by-step approach to evaluation of the cancer patient and presents an accumulation of clinical experience with challenges unique to patients with breast cancer and leukemia. Current data on reproductive outcomes of fertility preservation techniques are examined, demonstrating increasing evidence that these techniques are becoming effective enough to offer routinely to patients facing gonadotoxic cancer therapies, including those still considered to be "experimental."

Experimental evidence showing that no mitotically active female germline progenitors exist in postnatal mouse ovaries

It has been generally accepted for more than half a century that, in most mammalian species, oocytes cannot renew themselves in postnatal or adult life, and that the number of oocytes is already fixed in fetal or neonatal ovaries. This assumption, however, has been challenged over the past decade. In this study, we have taken an endogenous genetic approach to this question and generated a multiple fluorescent Rosa26(rbw/+);Ddx4-Cre germline reporter mouse model for in vivo and in vitro tracing of the development of female germline cell lineage. Through live cell imaging and de novo folliculogenesis experiments, we show that the Ddx4-expressing cells from postnatal mouse ovaries did not enter mitosis, nor did they contribute to oocytes during de novo folliculogenesis. Our results provide evidence that supports the traditional view that no postnatal follicular renewal occurs in mammals, and no mitotically active Ddx4-expressing female germline progenitors exist in postnatal mouse ovaries.

Environmentally induced epigenetic transgenerational inheritance of phenotype and disease

Environmental epigenetics has an important role in regulating phenotype formation or disease etiology. The ability of environmental factors and exposures early in life to alter somatic cell epigenomes and subsequent development is a critical factor in how environment affects biology. Environmental epigenetics provides a molecular mechanism to explain long term effects of environment on the development of altered phenotypes and "emergent" properties, which the "genetic determinism" paradigm cannot. When environmental factors permanently alter the germ line epigenome, then epigenetic transgenerational inheritance of these environmentally altered phenotypes and diseases can occur. This environmental epigenetic transgenerational inheritance of phenotype and disease is reviewed with a systems biology perspective.

The primordial follicle reserve is not renewed after chemical or γ-irradiation mediated depletion

Reports indicate that germ-line stem cells present in adult mice can rapidly generate new oocytes and contribute to the primordial follicle reserve following conditions of ovotoxic stress. We further investigated the hypothesis that adult mice have the capacity to generate new oocytes by monitoring primordial follicle numbers throughout postnatal life and following depletion of the primordial follicle reserve by exposure to doxorubicin (DXR), trichostatin A (TSA), or whole-body γ-irradiation. We show that primordial follicle number remains stable in adult C57BL/6 mice between the ages of 25 and 100 days. However, within 2 days of treatment with DXR or TSA, primordial follicle numbers had declined to 65 and 51% respectively (P<0.05-0.01 when compared to untreated controls), with no restoration of follicle numbers evident after 7 days for either treatment. Furthermore, ovaries from mice subjected to sterilizing doses of γ-irradiation (0.45 or 4.5 Gy) revealed complete ablation of all primordial follicles 5 days after treatment, with no indication of follicular renewal. We conclude that neo-folliculogenesis does not occur following chemical or γ-irradiation mediated depletion of the primordial follicle reserve.

Mechanisms of chemotherapy-induced human ovarian aging: double strand DNA breaks and microvascular compromise

The mechanism of chemotherapy-induced acceleration of ovarian aging is not fully understood. We used doxorubicin, a widely used cancer chemotherapeutic, in a variety of in vivo xenograft, and in vitro models to investigate the impact of chemotherapy-induced aging on the human ovary. Doxorubicin caused massive double-strand-DNA-breaks in primordial follicles, oocytes, and granulosa cells in a dose dependent fashion as revealed by accumulating γH2AX foci. This damage was associated with apoptotic oocyte death and resulted in the activation of ATM. It appeared that the repair response enabled a minor proportion of oocytes (34.7%) and granulosa cells (12.1%) to survive while the majority succumbed to apoptotic death. Paradoxically, inhibition of ATM by KU-55933 resulted in improved survival, probably via prevention of downstream activation of TAp63α. Furthermore, doxorubicin caused vascular and stromal damage in the human ovary, which might impair ovarian function both pre- and post-menopausally. Chemotherapy-induced premature ovarian aging appears to result from a complex process involving both the germ- and non-germ cell components of the ovary. These effects may have clinical implications in aging both for premenopausal and postmenopausal cancer survivors.