STUDY QUESTION Does LH protect mouse oocytes and female fertility from alkylating chemotherapy? SUMMARY ANSWER LH treatment before and during chemotherapy prevents detrimental effects on follicles and reproductive lifespan. WHAT IS KNOWN ALREADY Chemotherapies can damage the ovary, resulting in premature ovarian failure and reduced fertility in cancer survivors. LH was recently suggested to protect prepubertal mouse follicles from chemotoxic effects of cisplatin treatment. STUDY DESIGN, SIZE, DURATION This experimental study investigated LH effects on primordial follicles exposed to chemotherapy. Seven-week-old CD-1 female mice were randomly allocated to four experimental groups: Control (n = 13), chemotherapy (ChT, n = 15), ChT+LH-1x (n = 15), and ChT+LH-5x (n = 8). To induce primary ovarian insufficiency (POI), animals in the ChT and ChT+LH groups were intraperitoneally injected with 120 mg/kg of cyclophosphamide and 12 mg/kg of busulfan, while control mice received vehicle. For LH treatment, the ChT+LH-1x and ChT+LH-5x animals received a 1 or 5 IU LH dose, respectively, before chemotherapy, then a second LH injection administered with chemotherapy 24 h later. Then, two animals/group were euthanized at 12 and 24 h to investigate the early ovarian response to LH, while remaining mice were housed for 30 days to evaluate short- and long-term reproductive outcomes. The effects of LH and chemotherapy on growing-stage follicles were analyzed in a parallel experiment. Seven-week-old NOD-SCID female mice were allocated to control (n = 5), ChT (n = 5), and ChT+LH-1x (n = 6) groups. Animals were treated as described above, but maintained for 7 days before reproductive assessment. PARTICIPANTS/MATERIALS, SETTING, METHODS In the first experiment, follicular damage (phosphorylated H2AX histone (γH2AX) staining and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay), apoptotic biomarkers (western blot), and DNA repair pathways (western blot and RT-qPCR) were assessed in ovaries collected at 12 and 24 h to determine early ovarian responses to LH. Thirty days after treatments, remaining mice were stimulated (10 IU of pregnant mare serum gonadotropin (PMSG) and 10 IU of hCG) and mated to collect ovaries, oocytes, and embryos. Histological analysis was performed on ovarian samples to investigate follicular populations and stromal status, and meiotic spindle and chromosome alignment was measured in oocytes by confocal microscopy. Long-term effects were monitored by assessing pregnancy rate and litter size during six consecutive breeding attempts. In the second experiment, mice were stimulated and mated 7 days after treatments and ovaries, oocytes, and embryos were collected. Follicular numbers, follicular protection (DNA damage and apoptosis by H2AX staining and TUNEL assay, respectively), and ovarian stroma were assessed. Oocyte quality was determined by confocal analysis. MAIN RESULTS AND THE ROLE OF CHANCE LH treatment was sufficient to preserve ovarian reserve and follicular development, avoid atresia, and restore ovulation and meiotic spindle configuration in mature oocytes exposed at the primordial stage. LH improved the cumulative pregnancy rate and litter size in six consecutive breeding rounds, confirming the potential of LH treatment to preserve fertility. This protective effect appeared to be mediated by an enhanced early DNA repair response, via homologous recombination, and generation of anti-apoptotic signals in the ovary a few hours after injury with chemotherapy. This response ameliorated the chemotherapy-induced increase in DNA-damaged oocytes and apoptotic granulosa cells. LH treatment also protected growing follicles from chemotherapy. LH reversed the chemotherapy-induced depletion of primordial and primary follicular subpopulations, reduced oocyte DNA damage and granulosa cell apoptosis, restored mature oocyte cohort size, and improved meiotic spindle properties. LARGE SCALE DATA N/A. LIMITATIONS, REASONS FOR CAUTION This was a preliminary study performed with mouse ovarian samples. Therefore, preclinical research with human samples is required for validation. WIDER IMPLICATIONS OF THE FINDINGS The current study tested if LH could protect the adult mouse ovarian reserve and reproductive lifespan from alkylating chemotherapy. These findings highlight the therapeutic potential of LH as a complementary non-surgical strategy for preserving fertility in female cancer patients. STUDY FUNDING/COMPETING INTEREST(S) This study was supported by grants from the Regional Valencian Ministry of Education (PROMETEO/2018/137), the Spanish Ministry of Science and Innovation (CP19/00141), and the Spanish Ministry of Education, Culture and Sports (FPU16/05264). The authors declare no conflict of interest.
Study question Could controlled ovarian stimulation (COS) protocols used in fertility preservation (FP) impact on malignant cell proliferation and tumour molecular profiling of breast cancer (BC) patients? Summary answer Letrozole supplementation during ovarian stimulation for oocyte vitrification could be considered as a safe procedure in estrogen-dependent BC patients undergoing FP. What is known already High estradiol levels associated to COS could promote changes in gene expression in estrogen-positive BC tumors. Estradiol levels reached during the ovarian stimulation could aggressively promote malignant cell proliferation and cell migration to adjacent organs. Aromatase inhibitors such as letrozole, are added to standard stimulation protocols to avoid this undesirable potential side effect. Despite the reassuring clinical results achieved by using letrozole for FP in BC patients, there is still a lack of evidence regarding its impact on malignant cell behaviour. For this reason, specific molecular studies to properly evaluate safety of letrozole in this specific population are still required. Study design, size, duration Experimental in vivo study. Thirty 5-week-old Nude-nu female mice were divided into three different groups: BC (n = 10), BC and FSH stimulation (BC-FSH, n = 10), or BC and letrozole stimulation (BC-LTZ, n = 10). BC was considered the control group, whereas BC-FSH and BC-LTZ represented distinct COS protocols. Hormone-dependent BC was induced in all mice. Animals were followed-up for 5 months and then euthanized to collect kidney, ovary, spleen, and liver tissues for gene expression and immunohistochemistry (IHC) analysis. Participants/materials, setting, methods One million of human MCF–7 BC cells were injected into the mouse left kidney capsule. Two days after xenograft, COS was induced by 10IU FSH or 1mg/ml letrozole + 10IU FSH, followed by ovarian triggering with 10IU hCG at 48h. Human BC RT2 Profiler PCR Arrays were performed to evaluate the impact of COS on tumour behaviour. BC biomarkers (Ki67, Erα, PR and HER–2) were also analyzed by IHC to validate gene expression results. Main results and the role of chance The differential gene expression was firstly assessed in kidney samples, as they represent the xenograft site, and different expression profiles were obtained depending on the COS protocol used. The BC-FSH group showed a global over-expression pattern of all genes of the array when compared to BC and BC-LTZ. Further gene ontology analysis revealed that cellular process, biological regulation, metabolic process, and proteases were the most over-represented biological terms, with a 20.5-fold over-expression for MMP2 compared to the other groups. On the other hand, BC-LTZ mice presented gene expression profiles similar to that of controls. When other tissues were analysed to detect malignant cell presence, our results revealed a significant up-regulation of matrix-proteases, cell cycle and proliferation related-genes, in liver samples from the BC-FSH group, but no amplification of any of the studied genes was detected in ovarian tissue or spleen. IHC findings confirmed the presence of human BC cells in 100% of samples from kidney tissue and in 30% of samples from liver tissue in the BC-FSH group. No human cells were detected by IHC in the BC and BC-LTZ groups. Limitations, reasons for caution Since this is an animal model of estrogen-dependent BC induced through a cell line, further validation with human tumour breast cancer samples would be required. Wider implications of the findings: Adjuvant letrozole in COS protocols prevents BC cell migration. The present study suggests that this protective effect could be mediated by interfering ER-pathway downstream genes involved in cell proliferation and matrix digestion. Altogether, letrozole could safely be used as a supplement during COS procedures for oocyte vitrification in BC women. Trial registration number Not applicable
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