The Activation of Residual Dormant Follicles by Human Chorionic Gonadotropin (HCG) in Vivo: a Novel Treatment for Premature Ovarian Insufficiency

BackgroundWith the influence of factors such as ovarian surgery, high-dose radiotherapy and chemotherapy, environmental degradation, and bad living habits, the occurrence of premature ovarian insufficiency(POI) is getting younger and younger, and many young women's ovaries have entered the aging stage earlier. While many studies have investigated the patients with POI, which is still a challenge in reproductive medicine as the treatments available now are not ideal. POI patients have varying amounts of residual dormant follicles in the ovaries. Therefore, it is critical to further our understanding of primordial follicle activation in order to treat.This study aimed to investigate the activation of residual follicles in POI patients with injection of HCG, whether they could obtain embryos and become pregnant.Methods Four patients with POI were pretreated with dehydroepiandrosterone, Coenzyme Q10, estrogen and medroxyprogesterone. The prescribed amounts of estrogen and medroxyprogesterone were adjusted to maintain the level of FSH at ˂15 mIU/ml and the level of LH˂10 mIU/ml. When the treatments failed to induce the appearance of follicles after 3 months, the patients received treatment with 10000 IU of HCG. Results The residual dormant follicles in POI patients can be activated using our approach to obtain embryos and conceive by injection of HCG. ConclusionsPOI patients may conceive their own genetic children by activating dormant follicles in vivo. These findings may represent a new simple and feasible solution for the treatment of patients with POI to conceive their own genetic children.

ESR2 regulates indian hedgehog signaling in neonatal rat ovary

The transcriptional regulatory function of estrogen receptor β (ESR2) is essential for the regulation of primordial follicle activation (PFA). Increased PFA due to the loss of ESR2 becomes evident as early as postnatal day 8 (PND8). To identify the ESR2-regulated genes that control PFA, we performed RNA-seq analyses of wildtype, and Esr2 knockout (Esr2KO) neonatal rat ovaries collected on PND4, PND6, and PND8. Among the differentially expressed genes in Esr2KO ovaries, indian hedgehog (Ihh) displayed the highest downregulation among the ovary enriched genes. IHH regulated genes including Hhip as well as the steroidogenic enzymes were also downregulated in Esr2KO rat ovaries. Remarkably, the expression of Ihh in Esr2KO ovaries was not upregulated despite the high levels of Gdf9 and Bmp15, which are known regulators of Ihh expression in granulosa cells. Our findings suggest that indian hedgehog signaling in the neonatal rat ovary is dependent on ESR2.

Maintenance of quiescent oocytes by noradrenergic signals

All females adopt an evolutionary conserved reproduction strategy; under unfavorable conditions such as scarcity of food or mates, oocytes remain quiescent. However, the signals to maintain oocyte quiescence are largely unknown. Here, we report that in four different species – Caenorhabditis elegans, Caenorhabditis remanei, Drosophila melanogaster, and Danio rerio – octopamine and norepinephrine play an essential role in maintaining oocyte quiescence. In the absence of mates, the oocytes of Caenorhabditis mutants lacking octopamine signaling fail to remain quiescent, but continue to divide and become polyploid. Upon starvation, the egg chambers of D. melanogaster mutants lacking octopamine signaling fail to remain at the previtellogenic stage, but grow to full-grown egg chambers. Upon starvation, D. rerio lacking norepinephrine fails to maintain a quiescent primordial follicle and activates an excessive number of primordial follicles. Our study reveals an evolutionarily conserved function of the noradrenergic signal in maintaining quiescent oocytes.

Regulation of mouse primordial follicle formation by signaling through the PI3K pathway

Cell signaling mediated by the KIT receptor is critical for many aspects of oogenesis including the proliferation and migration of primordial germ cells, as well as the survival, growth, and maturation of ovarian follicles. We previously showed that KIT regulates cyst breakdown and primordial follicle formation, and in this study, have investigated the mechanisms downstream of the receptor by modulating the activity of two downstream signaling cascades: the phosphoinositide 3-kinase (PI3K) and the mitogen-activated protein kinase (MAPK) pathways. E17.5 ovaries were cultured for five days with a daily dose of media supplemented with either the PI3K inhibitor LY294002, the MEK inhibitor U0126, or a DMSO vehicle control. Our histological observations aligned with the established role of PI3K in oocyte growth and primordial follicle activation but also revealed that LY294002 treatment delayed the processes of cyst breakdown and primordial follicle formation. U0126 treatment also led to a reduction in oocyte growth and follicle development but did not appear to affect cyst breakdown. The delay in cyst breakdown was mitigated when ovaries were dually dosed with LY294002 and KITL, suggesting that while KIT may signal through PI3K to promote cyst breakdown, other signaling networks downstream of the receptor could compensate. These observations unearth a role for PI3K signaling in the establishment of the ovarian reserve and suggest that PI3K might be the primary mediator of KIT-induced cyst breakdown and primordial follicle formation in the mouse ovary.

Transcriptomic profiling of neonatal mouse granulosa cells reveals new insights into primordial follicle activation

The dormant population of ovarian primordial follicles is determined at birth and serves as the reservoir for future female fertility. Yet our understanding of the molecular, biochemical, and cellular processes underpinning primordial follicle activation remains limited. The survival of primordial follicles relies on the correct complement and morphology of granulosa cells, which provide signalling factors essential for oocyte and follicular survival. To investigate the contribution of granulosa cells in the primordial-to-primary follicle transition, gene expression profiles of granulosa cells undergoing early differentiation were assessed in a murine model. Ovaries from C57Bl/6 mice were enzymatically dissociated at time-points spanning the initial wave of primordial follicle activation. Post-natal day (PND) 1 ovaries yielded primordial granulosa cells, and PND4 ovaries yielded a mixed population of primordial and primary granulosa cells. The comparative transcriptome of granulosa cells at these time-points was generated via Illumina NextSeq 500 system which identified 131 significantly differentially expressed transcripts. The differential expression of eight of the transcripts was confirmed by RT-qPCR Following biological network mapping via Ingenuity Pathway Analysis, the functional expression of the protein products of three of the differentially expressed genes, namely FRZB, POD1 and ZFX, was investigated with in-situ immunolocalisation in PND4 mouse ovaries was investigated. Finally, evidence was provided that Wnt pathway antagonist, secreted frizzled-related protein 3 (FRZB), interacts with a suppressor of primordial follicle activation WNT3A and may be involved in promoting primordial follicle activation. This study highlights the dynamic changes in gene expression of granulosa cells during primordial follicle activation and provides evidence for a renewed focus into the Wnt signalling pathway’s role in primordial follicle activation.

CHEK2 SIGNALING IS THE KEY REGULATOR OF OOCYTE SURVIVAL AFTER CHEMOTHERAPY

Radiation and chemotherapy can damage the primordial follicle reserve in female cancer patients leading to ovarian failure and infertility. Preservation of ovarian function requires treatment strategies that prevent loss of immature oocytes in primordial follicles during cancer therapy. Checkpoint kinase 2 (CHEK2) inhibition prevents loss of primordial oocytes caused by DNA damage and thus is a promising target for ovoprotective treatment against genotoxic agents. To determine which cancer treatments could benefit from ovoprotective activity of CHEK2 inhibition we investigated oocyte survival in Chek2-/- mice exposed to different chemotherapy drugs. Here, we show that loss of CHEK2 function prevents elimination of primordial oocytes damaged by cisplatin, cyclophosphamide, mafosfamide, doxorubicin, and etoposide, suggesting it could be used to reduce ovarian damage caused by wide range of drugs. Using genetic knockouts we reveal a critical role for TRP53 in oocyte response to chemotherapy drugs and show that both targets of CHEK2, TAp63 and TRP53, are activated by cisplatin and cyclophosphamide. Furthermore, we show that checkpoint kinase inhibitor and radiation- and chemotherapy sensitizer AZD7762 reduces oocyte elimination after radiation and chemotherapy treatments, despite its cytotoxic effect on ovarian somatic cells. Altogether, these findings demonstrate the role for CHEK2 as the master regulator of primordial oocyte survival or death and credential its targeting for ovoprotective treatments.

PI3K/PTEN/AKT Signaling Pathways in Germ Cell Development and Their Involvement in Germ Cell Tumors and Ovarian Dysfunctions

Several studies indicate that the PI3K/PTEN/AKT signaling pathways are critical regulators of ovarian function including the formation of the germ cell precursors, termed primordial germ cells, and the follicular pool maintenance. This article reviews the current state of knowledge of the functional role of the PI3K/PTEN/AKT pathways during primordial germ cell development and the dynamics of the ovarian primordial follicle reserve and how dysregulation of these signaling pathways may contribute to the development of some types of germ cell tumors and ovarian dysfunctions.