Anti-Mullerian hormone attenuates both cyclophosphamide-induced damage and PI3K signalling activation, while rapamycin attenuates only PI3K signalling activation, in human ovarian cortex in vitro

STUDY QUESTION

What are the effects of cyclophosphamide exposure on the human ovary and can anti-Mullerian hormone (AMH) and rapamycin protect against these?

SUMMARY ANSWER

Exposure to cyclophosphamide compromises the health of primordial and transitional follicles in the human ovarian cortex and upregulates PI3K signalling, indicating both direct damage and increased follicular activation; AMH attenuates both of these chemotherapy-induced effects, while rapamycin attenuates only PI3K signalling upregulation.

WHAT IS KNOWN ALREADY

Studies primarily in rodents demonstrate that cyclophosphamide causes direct damage to primordial follicles or that the primordial follicle pool is depleted primarily through excessive initiation of follicle growth. This increased follicular activation is mediated via upregulated PI3K signalling and/or reduced local levels of AMH production due to lost growing follicles. Furthermore, while rodent data show promise regarding the potential benefits of inhibitors/protectants alongside chemotherapy treatment to preserve female fertility, there is no information about the potential for this in humans.

STUDY DESIGN, SIZE, DURATION

Fresh ovarian cortical biopsies were obtained from 17 healthy women aged 21-41 years (mean ± SD: 31.8 ± 4.9 years) at elective caesarean section. Biopsies were cut into small fragments and cultured for 24 h with either vehicle alone (DMSO), the active cyclophosphamide metabolite 4-hydroperoxycyclophosphamide (4-HC) alone, 4-HC + rapamycin or 4-HC+AMH. Two doses of 4-HC were investigated, 0.2 and 2 μM in separate experiments, using biopsies from seven women (aged 27-41) and six women (aged 21-34), respectively. Biopsies from four women (aged 28-38) were used to investigate the effect of rapamycin or AMH only.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Histological analysis of ovarian tissue was undertaken for follicle staging and health assessment. Western blotting and immunostaining were used to assess activation of PI3K signalling by measuring phosphorylation of AKT and phosphorylated FOXO3A staining intensity, respectively.

MAIN RESULTS AND THE ROLE OF CHANCE

Exposure to either dose of 4-HC caused an increase in the proportion of unhealthy primordial (P < 0.0001, both doses) and transitional follicles (P < 0.01 for low dose and P < 0.01 for high dose) compared to vehicle. AMH significantly reduced follicle damage by approximately half in both of the investigated doses of 4-HC (P < 0.0001), while rapamycin had no protective effect on the health of the follicles. Culture with AMH or rapamycin alone had no effect on follicle health. Activation of PI3K signalling following 4-HC exposure was demonstrated by both Western blotting data showing that 4-HC increased in AKT phosphorylation and immunostaining showing increased phosphorylated FOXO3A staining of non-growing oocytes. Treatment with rapamycin reduced the activation of PI3K signalling in experiments with low doses of 4-HC while culture with AMH reduced PI3K activation (both AKT phosphorylation and phosphorylated FOXO3A staining intensity) across both doses investigated.

LIMITATIONS, REASONS FOR CAUTION

These in vitro studies may not replicate in vivo exposures. Furthermore, longer experiment durations are needed to determine whether the effects observed translate into irreparable deficits of ovarian follicles.

WIDER IMPLICATIONS OF THE FINDINGS

These data provide a solid foundation on which to explore the efficacy of AMH in protecting non-growing ovarian follicles from gonadotoxic chemotherapies. Future work will require consideration of the sustained effects of chemotherapy treatment and potential protectants to ensure these agents do not impair the developmental competence of oocytes or lead to the survival of oocytes with accumulated DNA damage, which could have adverse consequences for potential offspring.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by grants from TENOVUS Scotland, the Academy of Medical Sciences (to R.R.), the Medical Research Council (G1100357 to R.A.A., MR/N022556/1 to the MRC Centre for Reproductive Health), and Merck Serono UK (to R.A.A.). R.R., H.L.S., N.S., and E.E.T. declare no conflicts of interest. R.A.A. reports grants and personal fees from Roche Diagnostics and Ferring Pharmaceuticals, and personal fees from IBSA and Merck outside the submitted work.

TRIAL REGISTRATION NUMBER

N/A.

Recent advances in the understanding of tubal ectopic pregnancy

Ectopic pregnancy (EP) is described as the implantation of an embryo outside the normal uterine cavity. It most commonly occurs in the fallopian tube, hence termed a tubal ectopic pregnancy (tEP). It is a gynaecological emergency and remains the leading cause of direct maternal mortality related to the first trimester of pregnancy worldwide. This article explores the emergence of additional risk factors for tEP, showing new evidence for identifying patient risk factors and highlighting potential areas of research. Additionally, we discuss the up-to-date patient-centred approach for the diagnosis, management and counselling of patients with tEP and ongoing clinical trials for the improvement of medical management.

Oncofertility awareness among primary care physicians in India

BACKGROUND

Primary care physicians not only coordinate referrals to oncology services but can play a crucial role in successful fertility preservation referrals in cancer-diagnosed patients. Hence, it is important to assess their knowledge and attitudes towards fertility preservation.

METHODS

An eighteen-item oncofertility survey was administered to primary care physicians between May 2019 to September 2020.  Results: A total of forty-six responses were received and analysed. About 60% of primary care physicians did not have adequate knowledge about available fertility preservation options and only 26-32% were aware of international guidelines recommending fertility preservation in cancer patients.  Conclusions: Imparting awareness and knowledge of fertility preservation and its options to primary care physicians could enable an integrated cancer care model while also facilitating successful oncofertility referrals in countries like India.

The impact of vincristine on testicular development and function in childhood cancer

BACKGROUND

Increasing childhood cancer survival rates in recent decades have led to an increased focus on fertility as a long-term complication of cancer treatment. Male childhood cancer survivors often face compromised testicular function as a late effect of chemotherapy exposure, with no well-established options to prevent such damage and subsequent infertility. Despite vincristine being considered to be associated with low-gonadotoxic potential, in prepubertal rodents, it was recently shown to result in morphological alterations of the testis and in severely impaired fertility.

OBJECTIVE AND RATIONALE

This systematic review aimed to evaluate the effects of vincristine-containing regimens on human prepubertal testis with reference to testicular function and fertility in adulthood.

SEARCH METHODS

The systematic search of the literature was conducted according to PRISMA guidelines, and the study was registered with PROSPERO. PubMed and Scopus were searched for articles published in English between 01 January 1900 and 05 March 2021, with the search including 'chemotherapy', 'vincristine', 'prepubertal', 'testis', 'spermatogenesis' and related terms. Abstracts and full-text articles were screened and selected for, providing they met the inclusion criteria (≤12 years at treatment, exposure to vincristine-containing regimens and long-term fertility outcomes). Additional studies were identified via bibliography screening. Bias evaluation across included studies was conducted using the ROBINS-I tool, subdivided into assessment for confounding, participant selection, intervention classification, missing data, outcome measurements and selection of reported results.

OUTCOMES

Our initial search identified 288 articles of which 24 (8%; n = 7134 males) met all inclusion criteria. Control groups were included for 9/24 (38%) studies and 4/24 (17%) studies provided sub-analysis of the relative gonadotoxicity of vincristine-based agents. Primary outcome measures were: fertility and parenthood; semen analysis (World Health Organization criteria); and hormonal function and testicular volume. For the studies that performed vincristine sub-analysis, none reported negative associations with vincristine for the potential of siring a pregnancy, including the largest (n = 6224; hazard ratio = 0.56) controlled study. For semen analysis, no significant difference versus healthy controls was illustrated for mitotic inhibitors (including vincristine) following sub-analysis in one study (n = 143). For hormone analysis, a single study did not find significant impacts on spermatogenesis attributed to vincristine based on levels of FSH and semen analysis, which meant that its administration was unlikely to be responsible for the diminished testicular reserve; however, most of the studies were based on low numbers of patients receiving vincristine-containing chemotherapy. Analysis of bias demonstrated that studies which included vincristine exposure sub-analysis had a lower risk of bias when compared with cohorts which did not.

WIDER IMPLICATIONS

In contrast to recent findings in rodent studies, the limited number of clinical studies do not indicate gonadotoxic effects of vincristine following prepubertal exposure. However, given the relative lack of data from studies with vincristine sub-analysis, experimental studies involving vincristine exposure using human testicular tissues are warranted. Results from such studies could better inform paediatric cancer patients about their future fertility and eligibility for fertility preservation before initiation of treatment.

Cisplatin Effects on the Human Fetal Testis - Establishing the Sensitive Period for (Pre)Spermatogonial Loss and Relevance for Fertility Preservation in Pre-Pubertal Boys

Background

Exposure to chemotherapy during childhood can impair future fertility. Studies using in vitro culture have shown exposure to platinum-based alkylating-like chemotherapy reduces the germ cell number in the human fetal testicular tissues. We aimed to determine whether effects of exposure to cisplatin on the germ cell sub-populations are dependent on the gestational age of the fetus and what impact this might have on the utility of using human fetal testis cultures to model chemotherapy exposure in childhood testis.

Methods

We utilised an in vitro culture system to culture pieces of human fetal testicular tissues (total n=23 fetuses) from three different gestational age groups (14-16 (early), 17-19 (mid) and 20-22 (late) gestational weeks; GW) of the second trimester. Tissues were exposed to cisplatin or vehicle control for 24 hours, analysing the tissues 72 and 240 hours post-exposure. Number of germ cells and their sub-populations, including gonocytes and (pre)spermatogonia, were quantified.

Results

Total germ cell number and number of both germ cell sub-populations were unchanged at 72 hours post-exposure to cisplatin in the testicular tissues from fetuses of the early (14-16 GW) and late (20-22 GW) second trimester. In the testicular tissues from fetuses of mid (17-19 GW) second trimester, total germ cell and gonocyte number were significantly reduced, whilst (pre)spermatogonial number was unchanged. At 240 hours post-exposure, the total number of germ cells and that of both sub-populations was significantly reduced in the testicular tissues from fetuses of mid- and late-second trimester, whilst germ cells in early-second trimester tissues were unchanged at this time-point.

Conclusions

In vitro culture of human fetal testicular tissues can be a useful model system to investigate the effects of chemotherapy-exposure on germ cell sub-populations during pre-puberty. Interpretation of the results of such studies in terms of relevance to later (infant and pre-pubertal) developmental stages should take into account the changes in germ cell composition and periods of germ cell sensitivity in the human fetal testis.

Maintenance of Sertoli Cell Number and Function in Immature Human Testicular Tissues Exposed to Platinum-Based Chemotherapy-Implications for Fertility Restoration

Background: Retrospective studies in adult survivors of childhood cancer show long-term impacts of exposure to alkylating chemotherapy on future fertility. We recently demonstrated germ cell loss in immature human testicular tissues following exposure to platinum-based chemotherapeutic drugs. This study investigated the effects of platinum-based chemotherapy exposure on the somatic Sertoli cell population in human fetal and pre-pubertal testicular tissues. Methods: Human fetal (n = 23; 14-22 gestational weeks) testicular tissue pieces were exposed to cisplatin (0.5 or 1.0 μg/ml) or vehicle for 24 h in vitro and analysed 24-240 h post-exposure or 12 weeks after xenografting. Human pre-pubertal (n = 10; 1-12 years) testicular tissue pieces were exposed to cisplatin (0.5 μg/ml), carboplatin (5 μg/ml) or vehicle for 24 h in vitro and analysed 24-240 h post-exposure; exposure to carboplatin at 10-times the concentration of cisplatin reflects the relative clinical doses given to patients. Immunohistochemistry was performed for SOX9 and anti-Müllerian hormone (AMH) expression and quantification was carried out to assess effects on Sertoli cell number and function respectively. AMH and inhibin B was measured in culture medium collected post-exposure to assess effects on Sertoli cell function. Results: Sertoli cell (SOX9^+ve) number was maintained in cisplatin-exposed human fetal testicular tissues (7,647 ± 459 vs. 7,767 ± 498 cells/mm²; p > 0.05) at 240 h post-exposure. No effect on inhibin B (indicator of Sertoli cell function) production was observed at 96 h after cisplatin (0.5 and 1.0 μg/ml) exposure compared to control (21 ± 5 (0.5 μg/ml cisplatin) vs. 23 ± 7 (1.0 μg/ml cisplatin) vs. 25 ± 7 (control) ng/ml, p > 0.05). Xenografting of cisplatin-exposed (0.5 μg/ml) human fetal testicular tissues had no long-term effect on Sertoli cell number or function (percentage seminiferous area stained for SOX9 and AMH, respectively), compared with non-exposed tissues. Sertoli cell number was maintained in human pre-pubertal testicular tissues following exposure to either 0.5 μg/ml cisplatin (6,723 ± 1,647 cells/mm²) or 5 μg/ml carboplatin (7,502 ± 627 cells/mm²) compared to control (6,592 ± 1,545 cells/mm²). Conclusions: This study demonstrates maintenance of Sertoli cell number and function in immature human testicular tissues exposed to platinum-based chemotherapeutic agents. The maintenance of a functional Sertoli cell environment following chemotherapy exposure suggests that fertility restoration by spermatogonial stem cell (SSC) transplant may be possible in boys facing platinum-based cancer treatment.

Can antioxidants protect against chemotherapy in a rat spermatogonial stem cell line?

Boys administered chemotherapy to treat cancer are at risk of damage to their healthy testicular tissue, which can lead to infertility in adulthood. Researchers are therefore investigating treatments to protect the testis during cancer treatment. Here, cells originating from rat testicles were cultured for 4 days and exposed to chemotherapy drugs with or without antioxidants for the final 2 days. Antioxidants can reduce cellular damage by inactivating toxic compounds. Here, antioxidants such as melatonin or n-acetylcysteine were tested against chemotherapy agents cisplatin, doxorubicin, or vincristine. Cultures were repeated four times, with cell survival measured at the end of culture. The antioxidants were not damaging and partially protected against cisplatin, although not doxorubicin. Surprisingly, n-acetylcysteine enhanced vincristine-induced damage. The results suggest that using antioxidants to protect the testis could have either beneficial or harmful effects when given alongside different chemotherapy drugs: this is important, considering that patients are often treated with multiple drugs.

Ectopic pregnancy and epithelial to mesenchymal transition: is there a link?

Ectopic pregnancy (EP) is defined as the implantation of an embryo outside of the uterus and is a leading cause of first trimester maternal mortality and morbidity. This article discusses a possible role for epithelial to mesenchymal transition in the pathogenesis of EP, given the notable similarity of protein expression between the two processes.

Chemotherapy induced damage to spermatogonial stem cells in prepubertal mouse in vitro impairs long-term spermatogenesis

Chemotherapy can affect testis development of young boys with cancer, reducing the chances of fatherhood in adulthood. Studies using experimental models are needed to determine the damage caused by individual chemotherapy drugs in order to predict the risk of infertility and direct patients towards appropriate fertility preservation options. Here, we investigated the individual role of two drugs, cisplatin and doxorubicin, using an in vitro culture model of prepubertal (postnatal day 5) mouse testis that supports induction and maintenance of full spermatogenesis. Twenty-four hour exposure with either drug at clinically-relevant doses (0.25, 0.5 or 0.75 μg/mL for cisplatin, or 0.01, 0.03 or 0.05 μg/mL for doxorubicin), induced an acute significant loss of spermatogonial stem cells (SSCs; PLZF+), proliferating SSCs (PLZF+BrdU+), total germ cells (MVH+), and spermatocytes (SCP3+) one week after chemotherapy exposure. By the time of the first (Week 4) and second (Week 8) waves of spermatogenesis, there was no longer any effect on SSC or proliferating SSC numbers in drug-exposed testis compared to untreated tissue: however, the populations of total germ cells and spermatocytes were still lower in the higher-dose cisplatin treated groups, along with a reduced frequency of round and elongated spermatids in both cisplatin- and doxorubicin-treated testis fragments. Overall, this study details a direct impairment of germ cell development following acute chemotherapy-induced damage during the prepubertal phase, most likely due to an effect on SSCs, using an in vitro culture system that successfully recapitulates key events of mouse spermatogenesis.

Cisplatin and carboplatin result in similar gonadotoxicity in immature human testis with implications for fertility preservation in childhood cancer

BACKGROUND

Clinical studies indicate chemotherapy agents used in childhood cancer treatment regimens may impact future fertility. However, effects of individual agents on prepubertal human testis, necessary to identify later risk, have not been determined. The study aimed to investigate the impact of cisplatin, commonly used in childhood cancer, on immature (foetal and prepubertal) human testicular tissues. Comparison was made with carboplatin, which is used as an alternative to cisplatin in order to reduce toxicity in healthy tissues.

METHODS

We developed an organotypic culture system combined with xenografting to determine the effect of clinically-relevant exposure to platinum-based chemotherapeutics on human testis. Human foetal and prepubertal testicular tissues were cultured and exposed to cisplatin, carboplatin or vehicle for 24 h, followed by 24-240 h in culture or long-term xenografting. Survival, proliferation and apoptosis of prepubertal germ stem cell populations (gonocytes and spermatogonia), critical for sperm production in adulthood, were quantified.

RESULTS

Cisplatin exposure resulted in a significant reduction in the total number of germ cells (- 44%, p < 0.0001) in human foetal testis, which involved an initial loss of gonocytes followed by a significant reduction in spermatogonia. This coincided with a reduction (- 70%, p < 0.05) in germ cell proliferation. Cisplatin exposure resulted in similar effects on total germ cell number (including spermatogonial stem cells) in prepubertal human testicular tissues, demonstrating direct relevance to childhood cancer patients. Xenografting of cisplatin-exposed human foetal testicular tissue demonstrated that germ cell loss (- 42%, p < 0.01) persisted at 12 weeks. Comparison between exposures to human-relevant concentrations of cisplatin and carboplatin revealed a very similar degree of germ cell loss at 240 h post-exposure.

CONCLUSIONS

This is the first demonstration of direct effects of chemotherapy exposure on germ cell populations in human foetal and prepubertal testis, demonstrating platinum-induced loss of all germ cell populations, and similar effects of cisplatin or carboplatin. Furthermore, these experimental approaches can be used to determine the effects of established and novel cancer therapies on the developing testis that will inform fertility counselling and development of strategies to preserve fertility in children with cancer.

In vitro administration of sodium arsenite in mouse prepubertal testis induces germ cell loss and apoptosis

High levels of arsenic contamination in drinking water pose serious health risks in numerous countries. The documentation reporting arsenic toxicity on reproduction and development is increasing, with evidence of arsenic inducing fertility and developmental issues. Nonetheless, the impact of arsenic exposure on the development of the male reproductive system is not fully elucidated. In the present study, we have investigated the direct effects of arsenic on prepubertal mouse testis using an in vitro testicular organ culture system. Culture medium was supplemented with a range of concentrations of sodium arsenite, examining effects of low (0.5 and 1 μM) and high (10, 50, 100 μM) concentrations, in cultures of post-natal day 5 CD1 mouse testis. In vitro exposure of low arsenic concentrations (0.5 or 1 μM) for 6 days did not cause any change in the testicular morphology, germ cells density, or apoptotic marker cleaved caspase 3 (CC3) expression. In contrast, exposure of prepubertal testis to high arsenic concentrations (10, 50 or 100 μM) induced drastic changes: severe destruction of testicular morphology, with loss of seminiferous tubule integrity; a dose-dependent decrease in germ cell density, and a hundred-fold increase in CC3 expression after 50 μM arsenic exposure. In conclusion, high arsenic treatment induced a dose-dependent induction of apoptosis and germ cell loss in prepubertal mouse testis.

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.

Oncofertility: Knowledge, Attitudes, and Barriers Among Indian Oncologists and Gynecologists

Purpose: Recommendations from the American Society of Clinical Oncology (ASCO) emphasize the critical need to understand current trends in fertility preservation (FP) among the two sets of primary health care providers involved in oncofertility: the oncologists and the gynecologists. This study is aimed at understanding the health care providers' knowledge, attitudes, and barriers in oncofertility across India. Methods: An 18-item oncofertility survey was designed and directed to 77 oncologists and 214 gynecologists across India. The responses were analyzed by using descriptive statistical methods, and the oncofertility trends between the two groups were studied. Results: The total response rate was 34%, with 49 of 214 oncologists (23%) and 49 of 77 gynecologists (64%) participating in the survey. The awareness of ASCO FP guidelines among oncologists and gynecologists was 53% and 59.5%, respectively. About 48% of oncologists felt knowledgeable about sperm banking, whereas 52% knew about oocyte freezing but not about other options. On the other hand, among gynecologists, 38% reported inadequate knowledge of testicular or ovarian tissue cryopreservation. About 85% of oncologists reported routine referral of cancer diagnosed patients for FP, whereas 75% of gynecologists reported routine FP discussion with patients. Health care providers from both groups perceived the major barriers in oncofertility to be, "financial burden on the patient" (73%-86%) and, "lack of patient awareness" (71%-79.5%). Conclusion: Effective collaboration between oncologists and gynecologists is essential to establish a successful FP program. Economic burden on the patient and lack of patient and physician awareness are limiting factors that need to be overcome.

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.

How does chemotherapy treatment damage the prepubertal testis?

Chemotherapy treatment is a mainstay of anticancer regimens, significantly contributing to the recent increase in childhood cancer survival rates. Conventional cancer therapy targets not only malignant but also healthy cells resulting in side effects including infertility. For prepubertal boys, there are currently no fertility preservation strategies in use, although several potential methods are under investigation. Most of the current knowledge in relation to prepubertal gonadotoxicity has been deduced from adult studies; however, the prepubertal testis is relatively quiescent in comparison to the adult. This review provides an overview of research to date in humans and animals describing chemotherapy-induced prepubertal gonadotoxicity, focusing on direct gonadal damage. Testicular damage is dependent upon the agent, dosage, administration schedule and age/pubertal status at time of treatment. The chemotherapy agents investigated so far target the germ cell population activating apoptotic pathways and may also impair Sertoli cell function. Due to use of combined chemotherapy agents for patients, the impact of individual drugs is hard to define, however, use of in vivo and in vitro animal models can overcome this problem. Furthering our understanding of how chemotherapy agents target the prepubertal testis will provide clarity to patients on the gonadotoxicity of different drugs and aid in the development of cytoprotective agents.

Chemotherapy drugs cyclophosphamide, cisplatin and doxorubicin induce germ cell loss in an in vitro model of the prepubertal testis

Long term survival rates for childhood cancers is steadily increasing, however cancer survivors can experience fertility problems as a consequence of chemotherapy treatment. This is particularly problematic for young boys, for whom no fertility preservation treatment is yet established. Here, we have determined the effects on prepubertal mouse testis of three commonly used chemotherapy drugs; cyclophosphamide (using its active metabolite phosphoramide mustard), cisplatin and doxorubicin, exposing testicular fragments to a clinically relevant range of concentrations in vitro. All three drugs induced a specific and highly significant loss of germ cells, including spermatogonial stem cells. In contrast, there was no significant effect on somatic cells, for either Sertoli or interstitial cells. Time course analysis of cleaved Caspase-3 expression showed a significant increase in apoptosis eight hours prior to a detectable decrease in germ cell numbers following exposure to phosphoramide mustard or cisplatin, although this pattern was not seen following doxorubicin-exposure. Moreover, analysis of DNA damage at 16 h showed increased γH2AX expression in response to all three drugs. Overall, results show that cisplatin, doxorubicin and cyclophosphamide all specifically induce loss of germ cells, including of spermatogonial stem cells, in the prepubertal mouse testis at concentrations relevant to human therapeutic exposures.

Etoposide damages female germ cells in the developing ovary

BACKGROUND

As with many anti-cancer drugs, the topoisomerase II inhibitor etoposide is considered safe for administration to women in the second and third trimesters of pregnancy, but assessment of effects on the developing fetus have been limited. The purpose of this research was to examine the effect of etoposide on germ cells in the developing ovary. Mouse ovary tissue culture was used as the experimental model, thus allowing us to examine effects of etoposide on all stages of germ cell development in the same way, in vitro.

RESULTS

Fetal ovaries from embryonic day 13.5 CD1 mice or neonatal ovaries from postnatal day 0 CD1 mice were cultured with 50-150 ng ml(-1) or 50-200 ng ml(-1) etoposide respectively, concentrations that are low relative to that in patient serum. When fetal ovaries were treated prior to follicle formation, etoposide resulted in dose-dependent damage, with 150 ng ml(-1) inducing a near-complete absence of healthy follicles. In contrast, treatment of neonatal ovaries, after follicle formation, had no effect on follicle numbers and only a minor effect on follicle health, even at 200 ng ml(-1). The sensitivity of female germ cells to etoposide coincided with topoisomerase IIα expression: in the developing ovary of both mouse and human, topoisomerase IIα was expressed in germ cells only prior to follicle formation.

CONCLUSIONS

Exposure of pre-follicular ovaries, in which topoisomerase IIα expression was germ cell-specific, resulted in a near-complete elimination of germ cells prior to follicle formation, with the remaining germ cells going on to form unhealthy follicles by the end of culture. In contrast, exposure to follicle-enclosed oocytes, which no longer expressed topoisomerase IIα in the germ cells, had no effect on total follicle numbers or health, the only effect seen specific to transitional follicles. Results indicate the potential for adverse effects on fetal ovarian development if etoposide is administered to pregnant women when germ cells are not yet enclosed within ovarian follicles, a process that starts at approximately 17 weeks gestation and is only complete towards the end of pregnancy.

Irinotecan metabolite SN38 results in germ cell loss in the testis but not in the ovary of prepubertal mice

STUDY QUESTION

Does the Irinotecan metabolite 7-ethyl-10-hydroxycamptothecan (SN38) damage the gonads of male and female prepubertal mice?

SUMMARY ANSWER

The Irinotecan metabolite SN38 reduces germ cell numbers within the seminiferous tubules of mouse testes at concentrations that are relevant to cancer patients, while in contrast it has little if any effect on the female germ cell population.

WHAT IS KNOWN ALREADY

Little is known about the role of the chemotherapeutic agent Irinotecan on female fertility, with only one article to date reporting menopausal symptoms in perimenopausal women treated with Irinotecan, while no data are available either on adult male fertility or on the impact of Irinotecan on the subsequent fertility of prepubertal cancer patients, female or male.

STUDY DESIGN SIZE, DURATION

Male and female gonads were obtained from postnatal day 5 C57BL/6 mice and exposed in vitro to a range of concentrations of the Irinotecan metabolite SN38: 0.002, 0.01, 0.05, 0.1 or 1 µg ml^–1 for the testis and 0.1, 1, 2.5 or 5 µg ml^–1 for the ovary, with treated gonads compared to control gonads not exposed to SN38. SN38 was dissolved in 0.5% dimethyl sulfoxide, with controls exposed to the same concentration of diluent. The number of testis fragments used for each analysis ranged between 3 and 9 per treatment group, while the number of ovaries used for each analysis ranged between 4 and 12 per treatment group.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Neonatal mouse gonads were developed in vitro, with tissue analysed at the end of the 4–6 day culture period, following immunofluorescence or hematoxylin and eosin staining. Statistical analyses were performed using one-way ANOVA followed by Bonferroni post-hoc test for normally distributed data and Kruskal-Wallis test followed by Dunns post-test for non-parametric data.

MAIN RESULTS AND THE ROLE OF CHANCE

Abnormal testis morphology was observed when tissues were exposed to SN38, with a smaller seminiferous tubule diameter at the highest concentration of SN38 (1 µg ml⁻¹, p < 0.001 versus control) and increased number of Sertoli cell-only tubules at the two highest concentrations of SN38 (0.1 µg ml⁻¹, p < 0.001; 1 µg ml⁻¹, p < 0.0001, both versus control). Within seminiferous tubules, a dose response decrease was observed in both germ cell number (mouse vasa homologue (MVH)-positive cells) and in proliferating cell number (bromodeoxyuridine (BrdU)-positive cells), with significance reached at the two highest concentrations of SN38 (0.1 µg ml⁻¹, p < 0.01 for both; 1 µg ml⁻¹, p < 0.001-MVH, p < 0.01-BrdU; all versus control). No change was seen in protein expression of the apoptotic marker cleaved caspase 3. Double immunofluorescence showed that occasional proliferating germ cells were present in treated testes, even after exposure to the highest drug concentration. When prepubertal ovaries were treated with SN38, no effect was seen on germ cell number, apoptosis or cell proliferation, even after exposure to the highest drug concentrations.

LIMITATIONS REASONS FOR CAUTION

As with any study using in vitro experiments with an experimental animal model, caution is required when extrapolating the present findings to humans. Differences between human and mouse spermatogonial development also need to be considered when assessing the effect of chemotherapeutic exposure. However, the prepubertal testes and ovaries used in the present studies contain germ cell populations that are representative of those found in prepubertal patients, and experimental tissues were exposed to drug concentrations within the range found in patient plasma.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings demonstrate that the prepubertal mouse ovary is relatively insensitive to exposure to the Irinotecan metabolite SN38, while it induces a marked dose-dependent sensitivity in the testicular germ cell population. The study identifies the importance of further investigation to identify the risk of infertility in young male cancer patients treated with Irinotecan.

LARGE SCALE DATA

None.

STUDY FUNDING AND COMPETING INTEREST(S)

Work supported by Medical Research Grant (MRC) grant G1002118 and Children with Cancer UK grant 15-198. The authors declare that there is no conflict of interest that could prejudice the impartiality of the present research.

Cancer treatment and gonadal function: experimental and established strategies for fertility preservation in children and young adults

Preservation of gonadal function is an important priority for the long-term health of cancer survivors of both sexes and all ages at treatment. Loss of opportunity for fertility is a prime concern in both male and female cancer survivors, but endocrine effects of gonadal damage are likewise central to long-term health and wellbeing. Some fertility preservation techniques, such as semen and embryo cryopreservation, are established and successful in adults, and development of oocyte vitrification has greatly improved the potential to cryopreserve unfertilised oocytes. Despite being recommended for all pubertal male patients, sperm banking is not universally practised in paediatric oncology centres, and very few adolescent-friendly facilities exist. All approaches to fertility preservation have specific challenges in children and teenagers, including ethical, practical, and scientific issues. For young women, cryopreservation of ovarian cortical tissue with later replacement has resulted in at least 40 livebirths, but is still regarded as experimental in most countries. For prepubertal boys, testicular biopsy cryopreservation is offered in some centres, but how that tissue might be used in the future is unclear, and so far no evidence suggests that fertility can be restored. For both sexes, these approaches involve an invasive procedure and have an uncertain risk of tissue contamination in haematological and other malignancies. Decision making for all these approaches needs assessment of the individual's risk of fertility loss, and is made at a time of emotional distress. Development of this specialty needs better provision of information for patients and their medical teams, and improvements in service provision, to match technical and scientific advances.

Culture and co-culture of mouse ovaries and ovarian follicles

The mammalian ovary is composed of ovarian follicles, each follicle consisting of a single oocyte surrounded by somatic granulosa cells, enclosed together within a basement membrane. A finite pool of follicles is laid down during embryonic development, when oocytes in meiotic arrest form a close association with flattened granulosa cells, forming primordial follicles. By or shortly after birth, mammalian ovaries contain their lifetime's supply of primordial follicles, from which point onwards there is a steady release of follicles into the growing follicular pool. The ovary is particularly amenable to development in vitro, with follicles growing in a highly physiological manner in culture. This work describes the culture of whole neonatal ovaries containing primordial follicles, and the culture of individual ovarian follicles, a method which can support the development of follicles from an immature through to the preovulatory stage, after which their oocytes are able to undergo fertilization in vitro. The work outlined here uses culture systems to determine how the ovary is affected by exposure to external compounds. We also describe a co-culture system, which allows investigation of the interactions that occur between growing follicles and the non-growing pool of primordial follicles.

Docetaxel induces moderate ovarian toxicity in mice, primarily affecting granulosa cells of early growing follicles

Advances in cancer therapy have focused attention on the quality of life of cancer survivors. Since infertility is a major concern following chemotherapy, it is important to characterize the drug-specific damage to the reproductive system to help find appropriate protective strategies. This study investigates the damage on neonatal mouse ovary maintained in vitro for 6 days, and exposed for 24 h (on Day 2) to clinically relevant doses of Docetaxel (DOC; low: 0.1 µM, mid: 1 µM, high: 10 µM). Furthermore, the study explores the putative protective action exerted by Tri-iodothyronine (T3; 10⁻⁷ M). At the end of culture, morphological analyses and follicle counts showed that DOC negatively impacts on early growing follicles, decreasing primary follicle number and severely affecting health at the transitional and primary stages. Poor follicle health was mainly due to effects on granulosa cells, indicating that the effects of DOC on oocytes were likely to be secondary to granulosa cell damage. DOC damages growing follicles specifically, with no direct effect on the primordial follicle reserve. Immunostaining and western blotting showed that DOC induces activation of intrinsic, type II apoptosis in ovarian somatic cells; increasing the levels of cleaved caspase 3, cleaved caspase 8, Bax and cleaved poly(ADP-ribose) polymerase, while also inducing movement of cytochrome C from mitochondria into the cytosol. T3 did not prevent the damage induced by the low dose of DOC. These results demonstrated that DOC induces a gonadotoxic effect on the mouse ovary through induction of somatic cell apoptosis, with no evidence of direct effects on the oocyte, and that the damaging effect is not mitigated by T3.

Cisplatin and doxorubicin induce distinct mechanisms of ovarian follicle loss; imatinib provides selective protection only against cisplatin

PURPOSE

Chemotherapy treatment in premenopausal women has been linked to ovarian follicle loss and premature ovarian failure; the exact mechanism by which this occurs is uncertain. Here, two commonly used chemotherapeutic agents (cisplatin and doxorubicin) were added to a mouse ovary culture system, to compare the sequence of events that leads to germ cell loss. The ability of imatinib mesylate to protect the ovary against cisplatin or doxorubicin-induced ovarian damage was also examined.

EXPERIMENTAL DESIGN

Newborn mouse ovaries were cultured for a total of six days, exposed to a chemotherapeutic agent on the second day: this allowed for the examination of the earliest stages of follicle development. Cleaved PARP and TUNEL were used to assess apoptosis following drug treatment. Imatinib was added to cultures with cisplatin and doxorubicin to determine any protective effect.

RESULTS

Histological analysis of ovaries treated with cisplatin showed oocyte-specific damage; in comparison doxorubicin preferentially caused damage to the granulosa cells. Cleaved PARP expression significantly increased for cisplatin (16 fold, p<0.001) and doxorubicin (3 fold, p<0.01). TUNEL staining gave little evidence of primordial follicle damage with either drug. Imatinib had a significant protective effect against cisplatin-induced follicle damage (p<0.01) but not against doxorubicin treatment.

CONCLUSION

Cisplatin and doxorubicin both induced ovarian damage, but in a markedly different pattern, with imatinib protecting the ovary against damage by cisplatin but not doxorubicin. Any treatment designed to block the effects of chemotherapeutic agents on the ovary may need to be specific to the drug(s) the patient is exposed to.

Raman micro-spectroscopy can be used to investigate the developmental stage of the mouse oocyte

In recent years, the uptake of assisted reproductive techniques such as in vitro fertilisation has risen exponentially. However, there is much that is still not fully understood about the biochemical modifications that take place during the development and maturation of the oocyte. As such, it is essential to further the understanding of how oocyte manipulation during these procedures ultimately affects its developmental potential; yet, there are few methods currently available which are capable of providing a quantitative measure of oocyte quality. Raman spectroscopy enables investigation of the global biochemical profile of intact cells without the need for labelling. Here, Raman spectra were acquired from the ooplasm of mouse oocytes at various stages of development, from late pre-antral follicles, collected after in vitro maturation within their ovarian follicles and from unstimulated and stimulated ovulatory cycles. Using a combination of univariate and multivariate statistical methods, it was found that ooplasm lipid content could be used to discriminate between different stages of oocyte development. Furthermore, the spectral profiles of mature oocytes revealed that oocytes which have developed in vitro are protein-deficient when compared to in vivo grown oocytes. Finally, the ratio of two Raman peak intensities, namely 1605∶1447 cm⁻¹, used as a proxy for the protein-to-lipid ratio of the ooplasm, was shown to be indicative of the oocyte's quality. Together, results indicate that Raman spectroscopy may present an alternative analytical tool for investigating the biochemistry of oocyte developmental stage and quality.

Implantation failure in mice with a disruption in Phospholipase C beta 1 gene: lack of embryonic attachment, aberrant steroid hormone signalling and defective endocannabinoid metabolism

Phospholipase C beta 1 (PLCβ1) is a downstream effector of G-protein-coupled receptor signalling and holds central roles in reproductive physiology. Mice with a disruption in the Plcβ1 gene are infertile with pleiotropic reproductive defects, the major reproductive block in females being implantation failure. Here, PLCβ1 was demonstrated at the luminal and glandular epithelia throughout the pre- and peri-implantation period, with transient stromal expression during 0.5-1.5 days post coitum (dpc). Examination of implantation sites at 4.5 dpc showed that in females lacking functional PLCβ1 (knock-out (KO) females), embryos failed to establish proper contact with the uterine epithelium. Proliferating luminal epithelial cells were evident in KO implantation sites, indicating failure to establish a receptive uterus. Real-time PCR demonstrated that KO implantation sites had aberrant ovarian steroid signalling, with high levels of estrogen receptor α, lactoferrin and amphiregulin mRNA, while immunohistochemistry revealed very low levels of estrogen receptor α protein, possibly due to rapid receptor turnover. KO implantation sites expressed markedly less fatty acid amide hydrolase and monoacylglycerol lipase, indicating that endocannabinoid metabolism was also affected. Collectively, our results show that PLCβ1 is essential for uterine preparation for implantation, and that defective PLCβ1-mediated signalling during implantation is associated with aberrant ovarian steroid signalling and endocannabinoid metabolism.

How do chemotherapeutic agents damage the ovary?

BACKGROUND

Chemotherapy treatment in premenopausal women is associated with an increased risk of premature ovarian failure (POF) but the exact mechanism through which this occurs is uncertain. In this review we examine the current evidence for the direct action of chemotherapeutic agents on the ovary and discuss possible molecular pathways through which follicle loss may occur.

METHODS

A systemic search of the databases, PubMed and Google Scholar, was made for all English language articles through to 2011 in each subject area discussed.

RESULTS

POF results from the loss of primordial follicles but this is not necessarily a direct effect of the chemotherapeutic agents. Instead, the disappearance of primordial follicles could be due to an increased rate of growth initiation to replace damaged developing follicles. Likewise, the loss of oocytes need not necessarily be a direct result of damage: evidence suggests that chemotherapy drugs can also induce oocyte death indirectly via damage to somatic cells. Specific molecular mechanisms and likely ovarian targets are discussed for some of the anti-cancer drugs most commonly used to treat premenopausal women. Finally, we consider current and prospective methods of preserving fertility.

CONCLUSIONS

It is likely that different chemotherapeutic drugs act through a range of mechanisms and on different target cells. More research into the cellular mechanisms underpinning chemotherapy-induced follicle loss could lead to the generation of treatments specifically designed to prevent POF.

Decreased oocyte DAZL expression in mice results in increased litter size by modulating follicle-stimulating hormone-induced follicular growth

While the germ cell-specific RNA binding protein, DAZL, is essential for oocytes to survive meiotic arrest, DAZL heterozygous (het) mice have an increased ovulation rate that is associated with elevated inhibin B and decreased plasma follicle-stimulating hormone (FSH). The relationship between decreased oocyte DAZL expression and enhanced follicular development in het mice was investigated using in vitro follicle cultures and in vivo modulation of endogenous FSH, by treating mice with inhibin and exogenous FSH. In vitro, follicles from het mice are more sensitive to FSH than those of wild-type (wt) mice and can grow in FSH concentrations that are deleterious to wild-type follicles. In vivo, despite no differences between genotypes in follicle population profiles, analysis of granulosa cell areas in antral follicles identified a significantly greater number of antral follicles with increased granulosa cell area in het ovaries. Modulation of FSH in vivo, using decreasing doses of FSH or ovine follicular fluid as a source of inhibin, confirmed the increased responsiveness of het antral follicles to FSH. Significantly more follicles expressing aromatase protein confirmed the earlier maturation of granulosa cells in het mice. In conclusion, it is suggested that DAZL expression represses specific unknown genes that regulate the response of granulosa cells to FSH. If this repression is reduced, as in DAZL het mice, then follicles can grow to the late follicular stage despite declining levels of circulating FSH, thus leading to more follicles ovulating and increased litter size.

Differential expression and regulation by activin of the neurotrophins BDNF and NT4 during human and mouse ovarian development

The tropomyosin-related kinase (Trk) B neurotrophin receptor is essential for ovarian germ cell survival and primordial follicle formation, but the contributions of its ligands, brain-derived neurotrophic factor (BDNF) and neurotrophin-4 (NT4), are unknown. We have investigated their expression and regulation in developing human and mouse ovaries. BDNF expression increased with increasing gestation, expression of human NTF4 and of both Ntf5 and Bdnf in the mouse was unchanged. Bdnf expression was dramatically lower than Ntf5 in the mouse, but levels were comparable in the human. Human fetal ovarian somatic cells expressed BDNF. Activin A selectively regulated BDNF and Ntf5 expression in human and mouse, respectively, identifying an oocyte/somatic signaling pathway which might mediate the pro-survival effects of activin. These data reveal that expression and regulation of the TrkB ligands are differentially controlled in the developing ovaries of humans and mice, and identify BDNF as a potential regulator of germ cell fate in the human fetal ovary.

Phospholipase C-beta1 signaling affects reproductive behavior, ovulation, and implantation

Infertility can result from a wide range of defects, from behavioral, through germ cell development and maturation, to fertilization or embryo development. Many of the hormones regulating these processes signal via G protein-coupled receptors, which in turn activate a range of plasma membrane enzymes including phospholipase C (PLC)-beta isoforms. Transgenic mice lacking functional Plc-beta1 (Plc-beta1 KO mice) have been noted to have severely impaired fertility, but there has been little study of the reproductive processes affected by lack of this enzyme. This study examined reproductive behavior, gonadal development, fertilization, and implantation in Plc-beta1 KO mice. Male and female Plc-beta1 KO mice exhibited impaired reproductive behavior. No other defect in reproduction was noted in males, raising the possibility that the reduced fertility of Plc-beta1 KO males could be due solely to impaired behavior. In contrast, female Plc-beta1 KO mice exhibited both behavioral and nonbehavioral defects. Plc-beta1 KO females ovulated only in response to exogenous hormones, with a large proportion of in vivo embryos recovered on embryonic d 4.5 exhibiting abnormal morphology. In addition, uteri of pregnant Plc-beta1 KO females exhibited an implantation defect, with poor embryo attachment and a failure to up-regulate cyclooxygenase-2 mRNA.

A single, mild, transient scrotal heat stress causes DNA damage, subfertility and impairs formation of blastocysts in mice

Infertility represents a major clinical problem and 50% of cases are attributable to the male partner. Testicular function is temperature dependent, and in both man and mouse the position of the testes in the scrotum ensures that they are kept at between 2 and 8 °C below core body temperature. We used a mouse model to investigate the impact of a single, transient, mild, scrotal heat stress (38, 40 or 42 °C for 30 min) on testicular function, sperm DNA integrity and embryo survival. We detected temperature-dependent changes in testicular architecture, number of apoptotic cells and a significant reduction in testis weight 7 and 14 days after heat stress at 42 °C. We report for the first time that DNA strand breaks (γ-H2AX-positive foci) were present in spermatocytes recovered from testes subjected to 40 or 42 °C. Fertility of heat-stressed males was tested 23–28 d after treatment (sperm at this time would have been spermatocytes at time of heating). Paternal heat stress at 42 °C resulted in reduced pregnancy rate, placental weight and litter size; pregnancies from the 40 °C group had increased resorptions at e14.5. Abnormalities in embryonic development were detected at e3.5 andin vitrofertilisation with sperm recovered 16 h or 23 d after scrotal stress at 42 °C revealed a block in development between the 4-cell and blastocyst stages. This study has provided evidence of temperature-dependent effects on germ cell DNA integrity and highlighted the importance of an intact paternal genome for normal embryo development.

Follicular growth and oocyte competence in the in vitro cultured mouse follicle: effects of gonadotrophins and steroids

Although there have been extensive studies on the effects of gonadotrophins and steroids on follicular development, less is known as to the effects these hormones have on the acquisition of oocyte developmental competence. This study investigates the effect of altering the gonadotrophin or steroidal environment on follicular development and on oocyte viability and DNA methylation. Oocytes were obtained from pre-ovulatory follicles after individual follicle culture from the pre-antral stage; gonadotrophin or steroid levels were manipulated during the culture period. Oocytes obtained from follicles grown in gonadotrophin free conditions were able to fertilize and develop to the blastocyst stage despite their impaired follicle development. There was no effect of luteinizing hormone or steroids on follicular growth. Altering the steroidal environment did, however, affect oocyte development. The oocytes of follicles exposed to high estrogen levels had lower fertilization rates, regardless of the presence or absence of high androgen levels. The combined presence of high levels of both steroids altered the level of global methylation. This study demonstrates that gonadotrophins and steroids influence the acquisition of developmental competence of the oocyte and suggests that optimal steroid exposure during follicle development is required for the oocyte to mature correctly.

The temporal and spatial expression pattern of Myosin Va, Vb and VI in the mouse ovary

There are 16 classes of unconventional myosins. Class V myosins have been shown to be involved in transporting cargo to and from the cell periphery. Class VI myosins have also been shown to transport cargo from the cell periphery, although it seems that these proteins have many roles which include the mediation of cell migration and stereocillia stabilisation. With the requirement of myosin VI for Drosophila oogenesis, the localised expression of Myosin V in the developing egg chamber and recent mounting evidence which links myosin VI to the migration of human ovarian cancer cell lines, we wanted to investigate the expression pattern of these two myosin classes in the normal mouse ovary. Here we show that these myosins are expressed, localised and regulated within the oocyte and granulosa cells of the developing mouse follicle.

Genomic imprinting and reproduction

Genomic imprinting is the parent-of-origin specific gene expression which is a vital mechanism through both development and adult life. One of the key elements of the imprinting mechanism is DNA methylation, controlled by DNA methyltransferase enzymes. Germ cells undergo reprogramming to ensure that sex-specific genomic imprinting is initiated, thus allowing normal embryo development to progress after fertilisation. In some cases, errors in genomic imprinting are embryo lethal while in others they lead to developmental disorders and disease. Recent studies have suggested a link between the use of assisted reproductive techniques and an increase in normally rare imprinting disorders. A greater understanding of the mechanisms of genomic imprinting and the factors that influence them are important in assessing the safety of these techniques.

The cultured rodent follicle as a model for investigations of gonadotrophin surge-attenuating factor (GnSAF) production

Gonadotrophin surge-attenuating factor (GnSAF) bioactivity (the suppression of GnRH-induced but not basal LH and FSH secretion from pituitary gonadotrophs) is produced by granulosa cells in vitro. Previous studies to investigate this bioactivity used dispersed granulosa cells which lack some cell types and the structural components of the follicle in vivo. The aim of this study, therefore, was to investigate whether intact rodent follicle culture was a suitable model for the study of the production of GnSAF bioactivity, allowing GnSAF to be investigated in a more physiologically realistic environment while still retaining culture conditions from which, as with granulosa cell cultures, extraneous factors can be excluded. Follicles from 16-day-old rats and 21-day-old mice were cultured for 3–6 days in the presence or absence of FSH and/or LH. The follicle-conditioned medium, and matching samples of unconditioned culture medium were added to our established rat pituitary monolayer GnSAF bioassay. Both mouse and rat intact follicles produced GnSAF bioactivity, reducing GnRH-induced LH secretion significantly. GnSAF output from the mouse follicles was highest during days 1–3 of culture, when follicles were at an early antral stage of development, and fell on days 4–6 as the follicles grew to the mid antral stage. While the stimulatory effects of FSH on rat follicle GnSAF secretion was dose-dependent, LH alone did not increase GnSAF production. An antibody against human GnSAF blocked GnSAF bioactivity produced by rat follicles, and recognised proteins within the expected pI and molecular weight range for GnSAF in two-dimensional gels of rat follicle-conditioned medium, showing a good homology between rodent and human GnSAF proteins. In conclusion, the release of GnSAF bioactivity is principally from small follicles stimulated by FSH. Therefore, intact rodent follicle culture systems offer an excellent model for the investigation of factors controlling GnSAF production under relatively physiological conditions.

The role of neurotrophin receptors in female germ-cell survival in mouse and human

During mammalian ovary formation, the production of ovarian follicles is accompanied by an enormous loss of germ cells. It is not known how this loss is regulated. We have investigated the role of the Trk tyrosine kinase receptors, primarily TrkB, in this process. The ovaries of TrkB-/- and TrkC-/- mice with a mixed (129Sv x C57BL/6) genetic background were examined shortly after birth. Around 50% of TrkB-/- mice had grossly abnormal ovaries that contained greatly reduced numbers of follicles. No defects were found in the ovaries of TrkC-/- mice. Congenic TrkB-/- mice were generated on 129Sv and C57BL/6 backgrounds: whereas the former had a mixed ovarian phenotype similar to that of the original colony of mice, the ovaries of all offspring of the C57BL/6 congenic line contained reduced numbers of follicles. RT-PCR showed that mRNA encoding TrkB and its two ligands, neurotrophin 4 (NT4) and brain-derived neurotrophic factor (BDNF), were present throughout the period of follicle formation in the mouse. In situ hybridisation showed that TrkB was expressed primarily in the germ cells before and after follicle formation. Mouse neonatal and fetal ovaries and human fetal ovaries were cultured in the presence of K252a, a potent inhibitor of all Trk receptors. In mice, K252a inhibited the survival of germ cells in newly formed (primordial) follicles. This effect was rescued by the addition of basic fibroblast growth factor (bFGF) to the culture medium. Combined addition of both BDNF and NT4 blocking antibodies lowered germ-cell survival, indicating that these TrkB ligands are required in this process. The results indicate that signalling through TrkB is an important component of the mechanism that regulates the early survival of female germ cells.

Mouse ovarian follicles secrete factors affecting the growth and development of like-sized ovarian follicles in vitro

A series of experiments have been carried out to determine whether follicles secrete factors able to affect the growth and development of other, like-sized follicles. Late preantral mouse ovarian follicles were either cocultured or cultured in media conditioned by previously cultured follicles. In particular, the experiments examined whether follicles do secrete such factors, whether the level of FSH in the culture media can affect that process, and what the nature of such secretory factor(s) might be. First, pairs of follicles were cocultured across a polycarbonate membrane containing pores. This showed that communication between the follicles resulted in the stimulation of growth and that the stimulation was due, at least in part, to the production of secretory factor(s). In subsequent experiments, follicles were cultured in media that had been preconditioned by previously cultured follicles. The concentration of FSH in the cultures determined the effect of the conditioned media: conditioned media was stimulatory to follicle growth when levels of FSH remained high throughout the culture, but inhibitory when FSH levels were dropped midway through the cultures. Heat inactivation removed this inhibitory effect, showing that the factor was likely to be a protein; addition of follistatin to the conditioned media did not alter its effect, indicating that the factor was unlikely to be activin. We have shown through a series of culture experiments that mouse follicles secrete factor(s) that can affect the development of other like-sized follicles when cultured from the late preantral to Graafian stages. Furthermore, we have shown that the effect (or production) of such factors is dependent on the FSH environment of the follicles.

Neurotropins and their receptors are expressed in the human fetal ovary

Mammalian ovarian development is characterized by a sequential pattern of mitotic proliferation of oogonia, initiation then arrest of meiosis, and primordial follicle formation. The factors regulating these processes are poorly understood. The neurotropins are survival and differentiation factors in the nervous system, acting via high affinity receptors of the trk protooncogene family and the low affinity p75 nerve growth factor receptor, and have also been described in the rodent ovary, where changes in NT4/TrkB gene expression have been detected at the time of primordial follicle formation. There are no data on neurotropin expression in the normal human ovary. We have investigated the expression and localization of neurotropins and their receptors in the midtrimester human fetal ovary (13-21 wk gestation). Expression of mRNA for neurotropins and their receptors was detected by RT-PCR. Clusters of oogonia were found to be the predominant site of NT4 mRNA expression using in situ hybridization. However, at later gestations granulosa cells of primordial follicles showed increased expression, with lesser expression in the enclosed oocytes. NT4 protein was also localized to the granulosa cells by immunohistochemistry and at earlier developmental stages to epithelioid cells, which were mingled with clusters of oogonia not expressing NT4. TrkB receptor protein was localized by immunohistochemistry to germ cells at all gestations examined. The p75 nerve growth factor receptor protein was exclusively expressed in the ovarian stroma. These data demonstrate the expression of neurotropins and their receptors within the human fetal ovary. Developmental changes in the pattern of expression of NT4 around the time of primordial follicle formation suggest that neurotropins may be involved in signaling between somatic cells and germ cells at this crucial stage of ovarian development.

Combined effect of follicle-follicle interactions and declining follicle-stimulating hormone on murine follicle health in vitro

Follicle selection occurs throughout an adult female's reproductive life, with selected, dominant follicle(s) developing to the preovulatory stage whereas the remaining, subordinate follicles within the growing cohort instead undergo atresia and die. To date, most research into follicle dominance has concentrated on its endocrine regulation, although it seems likely that intraovarian mechanisms are also involved in its regulation. We demonstrate here that the response of singly cultured murine follicles to declining concentrations of FSH depends on their developmental stage, with follicles at an earlier stage of development being much more susceptible than mature follicles to a lowering of FSH levels. We then extrapolate this information to follicle cocultures, in which a large dominant follicle was grown with a small subordinate follicle in a manner that maintained a dominant/subordinate relationship, with follicle health assessed by a terminal transferase-mediated 2'-deoxyuracil 5'-triphosphate nick end-labeled reaction on whole-follicle mounts. Our investigations show a combined negative effect of coculture and FSH withdrawal on small subordinate follicles, such that subordinate follicles cocultured with dominant follicles and subjected to a lowering of FSH levels during the culture period exhibit a greatly increased incidence of apoptosis in the granulosa cells (750% increase) compared with that exhibited by the dominant follicles (97% increase). We suggest that a similar interaction between endocrine and intraovarian factors regulates follicular dominance in vivo, such that dominant follicles, in addition to bringing about a fall in FSH levels via the hypothalamic-pituitary axis, exert local, direct effects on subordinate follicles, with both of these influences combining to induce atresia in subordinate follicles.

Effect of ascorbic acid on health and morphology of bovine preantral follicles during long-term culture

During ovarian folliculogenesis, ascorbic acid may be involved in collagen biosynthesis, steroidogenesis and apoptosis. The aims of this study were to determine the effects of ascorbic acid on bovine follicle development in vitro. Preantral follicles were cultured for 12 days in serum-free medium containing ascorbic acid (50 microg ml(-1)). Half of the medium was replaced every 2 days, and conditioned medium was analysed for oestradiol and matrix metalloproteinase 2 (MMP-2) and MMP-9 secretion. On day 12, cell death was assessed by TdT-mediated dUTP-biotin nick end labelling (TUNEL). In the absence of serum, there was significant (P < 0.05) follicle growth and oestradiol secretion over the 12 day culture period. Ascorbic acid had no effect on these parameters. The addition of serum from day 0 stimulated follicle growth (P < 0.05), but compromised follicle integrity. By day 12 of culture, a higher proportion of follicles remained intact in the presence of ascorbic acid in serum-free conditions (P < 0.05), and significantly (P < 0.01) less granulosa and theca cell death was observed in these follicles than in control follicles. Moreover, ascorbic acid significantly (P < 0.05) increased production of MMP-9, an enzyme involved in basement membrane remodelling. In conclusion, this culture system was capable of supporting follicle differentiation over the 12 day culture period. Furthermore, ascorbic acid maintains bovine follicle health and basement membrane remodelling in vitro.

Follicular development in vitro

There has been tremendous interest in recent years in the culture of oocytes and follicles. Although much of the research using follicle culture aims to increase understanding of the regulation of follicle development, an important goal has been to develop a method that will eventually allow maturation of human oocytes from the primordial follicle to the mature Graafian stage. We are still some way from this at present, although it has now been achieved in the mouse. In this article, we consider various methods of follicle culture for primordial, preantral, and antral follicles. In vitro development of primordial follicles has used primarily whole ovaries or ovarian fragments as a source of follicles. Culture of later stages of follicle development uses mainly isolated follicular units, either whole (with an intact basement membrane and, in some cases, attached thecal cells) or nonintact (oocyte-somatic cell complexes, which may or may not have remnants of basement membranes and/or thecal cells attached).

Role of ascorbic acid in promoting follicle integrity and survival in intact mouse ovarian follicles in vitro

Ascorbic acid has three known functions: it is necessary for collagen synthesis, promotes steroidogenesis and acts as an antioxidant. Within the ovary, most studies have concentrated on the role of ascorbic acid in luteal formation and regression and little is known about the function of this vitamin in follicular growth and development. Follicular growth and development were investigated in this study using an individual follicle culture system that allows the growth of follicles from the late preantral stage to Graafian morphology. Follicles were isolated from prepubertal mice and cultured for 6 days. Control media contained serum and human recombinant FSH. Further groups of follicles were cultured in the same media but with the addition of ascorbic acid at concentrations of either 28 or 280 micromol l(-1). Addition of ascorbic acid at the higher concentration significantly increased the percentage of follicles that maintained basement membrane integrity throughout culture (P < 0.001). Ascorbic acid had no effect on the growth of the follicles or on oestradiol production. Metalloproteinase 2 activity tended to increase at the higher concentration of ascorbic acid and there was a significant concomitant increase in the activity of tissue inhibitor of metalloproteinase 1 (P < 0.01). Follicles cultured without the addition of serum but with FSH and selenium in the culture media underwent apoptosis. Addition of ascorbic acid to follicles cultured under serum-free conditions significantly reduced apoptosis (P < 0.05). From these data it is concluded that ascorbic acid is necessary for remodelling the basement membrane during follicular growth and that the ability of follicles to uptake ascorbic acid confers an advantage in terms of granulosa cell survival.

Müllerian inhibitory substance induces growth of rat preantral ovarian follicles

Müllerian inhibitory substance (MIS), also known as anti-Müllerian hormone, is best known as the hormone that regulates the regression of the Müllerian duct in males. In females, MIS is expressed in granulosa cells of preantral and early antral follicles. The specific MIS type II receptor is present in granulosa and theca cells of these small, growing follicles. Because the role of MIS in preantral follicle development is unknown, we have evaluated the effect of MIS on the growth, differentiation, and apoptosis of intact preantral follicles in a serum-free culture system. In this system, treatment with FSH induces an increase in both follicle diameter, cell number, and follicle cell differentiation based on increased inhibin-alpha synthesis. Of interest, treatment with MIS enhances the effect of FSH both on follicle diameter and cell number. Although treatment with activin A also enhances FSH effects on follicle growth, treatment with transforming growth factor (TGF)-ss inhibits the FSH effects on follicle growth. Based on in situ staining of fragmented DNA, MIS was found to have no effect on follicle cell apoptosis, unlike its proapoptotic action on Müllerian ducts. In contrast to MIS and activin, TGF-ss was a potent proapoptotic factor for preantral follicles in culture. Analysis of inhibin-alpha expression of cultured preantral follicles further indicated that in contrast to activin, treatment with MIS did not enhance FSH-stimulated follicle differentiation. Thus, MIS is a unique factor that promotes preantral follicle growth but not preantral follicle cell differentiation and apoptosis.

Failure of founder transgenic male mice to transmit an attenuated HSV thymidine kinase transgene results from mosaicism and sperm competition

Previously we found that male mice carrying either of two attenuated herpes simplex virus thymidine kinase reporter transgenes displayed low level ectopic expression of the reporter gene in the testis and, although fertile, exhibited reduced fecundity. In contrast to males of later generations, many of the founder males failed to transmit the transgene to their progeny. This led to the suggestion that these fertile non-transmitting males are mosaic, with the sperm developing from the non-transgenic lineage outperforming those from the heterozygous transgenic lineage. Here we present the results of artificial insemination (AI) and in vitro fertilization (IVF) experiments designed to test this hypothesis. Albino CF(1) hybrid females were inseminated with mixtures of equal numbers of sperm from heterozygous transgenic (HT) males (equivalent to C57BL/6 x CBAF(2)) and CF(1) males. Similar mixed inseminations were carried out in parallel with sperm from non-transgenic (NT) siblings of the HT mice and 13-day fetuses were scored by eye color to determine their paternity. The pooled data from five experiments gave ratios of CF(1) to HT and CF(1) to NT offspring of 8.13 and 0.22 respectively, implying a calculated HT to NT ratio of 0.027. This indicates that, in competition with each other, the NT sperm would be almost 40 times more successful in fertilization than the HT sperm. Smaller differences were observed between HT and NT when AI was performed with unmixed sperm, consistent with the fertility of HT non-founder males. However, in five IVF experiments carried out with unmixed sperm, 142/212 oocytes exposed to NT sperm were activated and divided, while only 8/226 oocytes treated with HT sperm reached the two-cell stage. This confirms that HT sperm are defective and indicates that the IVF method employed amplified these deficiencies, which may have only a small effect upon natural reproduction when the HT sperm are not in competition with normal sperm.

Gonadotropin induction of ovulation and corpus luteum formation in young estrogen receptor-alpha knockout mice

Estrogen receptor-alpha (ERalpha) knockout (ERalphaKO) female mice are infertile. Initially, they exhibit normal follicular development, but by 4-5 wk of age, they begin to develop hemorrhagic ovarian cysts. Follicles in adult ERalphaKO female mice progress to the graafian stage, but there are no corpora lutea (CL). To test whether ERalpha is required for ovarian folliculogenesis, ovulation, and CL formation, eCG and hCG were used to ovulate 3- to 5-wk-old ERalphaKO and wild-type (WT) sibling mice. Gonadotropin administration resulted in ovulation in both ERalphaKO and WT mice. Gonadotropin-treated ERalphaKO females that ovulated produced 7.09 +/- 0.77 oocytes per mouse, whereas gonadotropin-treated WT female mice had 16.17 +/- 0.84 oocytes. Surprisingly, ruptured ERalphaKO ovarian follicles developed into CL that had normal morphology. Gonadotropin-treated ERalphaKO mice had 3-fold higher concentrations of serum progesterone than did control ERalphaKO mice that had been administered saline rather than gonadotropins. Thus, the CL in gonadotropin-treated ERalphaKO mice appeared to be steroidogenically functional. On the basis of these findings, ovarian folliculogenesis, ovulation, and CL formation can occur in the absence of ERalpha, although to a lesser extent than in WT mice.