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.

A Case of Pre-Existing Pregnancy During an In-Vitro Fertilization Cycle

Serum progesterone levels performed prior to oocyte pick-up is commonly used to guide embryo transfer in in-vitro fertilization (IVF) cycles, as elevated levels can negatively influence pregnancy outcomes. However, levels associated with normal pregnancies should trigger clinicians to consider alternative causes such as a pre-existing pregnancy. We report a case of a 37-year-old patient who underwent controlled ovarian hyperstimulation in a gonadotrophin-releasing hormone antagonist cycle while having an undetected early pregnancy. No oocytes were retrieved at oocyte retrieval despite adequate follicular responses. Her serum progesterone level on the day of her trigger injection was 57.8 nmol/L. She was found to have a pregnancy of unknown location, detected 3 weeks after her oocyte retrieval and was subsequently treated with systemic methotrexate.

O-190 Comparison between effects of exposure to platinum-based chemotherapeutics (cisplatin and carboplatin) on Sertoli cell number and functions in immature human testicular tissues

Study question

Does exposure to either cisplatin or carboplatin have a damaging effect on the Sertoli cell population in the immature human testicular tissues?

Summary answer

Exposure to cisplatin or carboplatin did not appear to have a major effect on Sertoli cell number or function in the immature human testicular tissues

What is known already

Long-term survival rates for children with cancer are more than 80%. However, childhood cancer treatment may result in subsequent infertility. Cisplatin is one of the most commonly used drugs for childhood cancers. Carboplatin, a second generation platinum drug, is administered at 10-times the dose of cisplatin and is believed to be less gonadotoxic. In our recent publication we have shown that exposure to both cisplatin and carboplatin acutely reduce the germ cell number in immature human testicular tissues. However, it is not known how cisplatin and carboplatin affect Sertoli cell number and function.

Study design, size, duration

In-vitro culture of human fetal and pre-pubertal testicular tissues was utilised. Tissue pieces were cultured for 1-3 days prior to exposure to clinically-relevant doses of chemotherapeutics or vehicle control for 24hrs in two sets of experiments: 1) 0.5 or 1 μg/ml cisplatin and culture ended at 24 and 96hrs post-exposure (fetal only); 2) 0.5 μg/ml cisplatin or 5 ­μg/ml carboplatin until 72 (both fetal and pre-pubertal) and 240hrs post-­exposure (fetal only).

Participants/materials, setting, methods

Testicular tissue fragments from second trimester human fetal (14-22 gestational weeks; n = 3-6) or pre-pubertal patients (1-8years old; n = 5) were cultured in a ‘hanging drop’ system.Quantification of Sertoli cell number (cells per cord/tubular area (mm2)) was performed on sections stained for expression of SOX9. Culture medium was collected to measure levels (ng/ml) of Anti-Mullerian hormone (AMH) and Inhibin B using ELISA. Statistical analysis was performed using two-way ANOVA to account for inter-individual variation between fetuses/patients.

Main results and the role of chance

Quantification of positively stained Sertoli cells showed that exposure to both doses of cisplatin had no effect on Sertoli cell number at 24 and 96hrs post-exposure. No changes in AMH and inhibin B levels were observed at these time-points. Comparison between cisplatin- or carboplatin-exposed human fetal testicular tissues showed no difference in Sertoli cell numbers at either 72hrs or 240hrs post-exposure. No difference in Sertoli cell number was observed in pre-pubertal testicular tissues exposed to either cisplatin or carboplatin at 72hrs post-exposure.

Limitations, reasons for caution

Human fetal and pre-pubertal testis tissue is of limited availability, thus, sample sizes used in this study were relatively low. ‘Hanging drop’ culture might not recapitulate all in-vivo aspects of immature testis microenvironment.

Wider implications of the findings

Exposure to cisplatin or carboplatin did not affect Sertoli cell number in the immature human testicular tissues. Taken together with our recent publication, this suggests that these two platinum-based chemotherapeutic agents cause direct damage to germ cells. Functionality of Sertoli cells in chemotherapy-exposed tissues need to be further investigated.

Trial registration number

not applicable

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.

Experimental models of testicular development and function using human tissue and cells

The mammalian testis has two main roles, production of gametes for reproduction and synthesis of steroid- and peptide hormones for masculinization. These processes are tightly regulated and involve complex interactions between a number of germ and somatic cell-types that comprise a unique microenvironment known as the germ stem cell niche. In humans, failure of normal testicular development or function is associated with susceptibility to a variety of male reproductive disorders including disorders of sex development, infertility and testicular cancer. Whilst studies in rodent models have provided detailed insight into the signaling pathways and molecular mechanisms that regulate the testis, there are important species differences in testicular development, function and reproductive disorders that highlight the need for suitable experimental models utilising human testicular tissues or cells. In this review, we outline experimental approaches used to sustain cells and tissue from human testis at different developmental time-points and discuss relevant end-points. These include survival, proliferation and differentiation of cell lineages within the testis as well as autocrine, paracrine and endocrine function. We also highlight the utility of these experimental approaches for modelling the effects of environmental exposures on testicular development and function.