Generation of kisspeptin-responsive GnRH neurons from human pluripotent stem cells

[Notch1/Akt/Foxo1 Pathway Regulated by Kisspeptin Is Involved in Endometrial Decidualization in Patients With Recurrent Spontaneous Abortion]

Objective

Kisspeptin, a protein encoded by the KISS1 gene, functions as an essential factor in suppressing tumor growth. The intricate orchestration of cellular processes such as proliferation and differentiation is governed by the Notch1/Akt/Foxo1 signaling pathway, which assumes a central role in maintaining cellular homeostasis. In the specific context of this investigation, the focal point lies in a meticulous exploration of the intricate mechanisms underlying the regulatory effect of kisspeptin on the process of endometrial decidualization. This investigation delves into the interplay between kisspeptin and the Notch1/Akt/Foxo1 signaling pathway, aiming to elucidate its significance in the pathophysiology of recurrent spontaneous abortion (RSA).

Methods

We enrolled a cohort comprising 45 individuals diagnosed with RSA, who were admitted to the outpatient clinic of the Reproductive Center at the Second Affiliated Hospital of Soochow University between June 2020 and December 2020. On the other hand, an additional group of 50 women undergoing elective abortion at the outpatient clinic of the Family Planning Department during the same timeframe was also included. To comprehensively assess the molecular landscape, Western blot and RT-qPCR were performed to analyze the expression levels of kisspeptin (and its gene KISS1), IGFBP1 (an established marker of decidualization), Notch1, Akt, and Foxo1 within the decidua. Human endometrial stromal cells (hESC) were given targeted interventions, including treatment with siRNA to disrupt KISS1 or exposure to kisspeptin10 (the bioactive fragment of kisspeptin), and were subsequently designated as the siKP group or the KP10 group, respectively. A control group comprised hESC was transfected with blank siRNA, and cell proliferation was meticulously evaluated with CCK8 assay. Following in vitro induction for decidualization across the three experimental groups, immunofluorescence assay was performed to identify differences in Notch1 expression and decidualization morphology between the siKP and the KP10 groups. Furthermore, RT-qPCR and Western blot were performed to gauge the expression levels of IGFBP1, Notch1, Akt, and Foxo1 across the three cell groups. Subsequently, decidualization was induced in hESC by adding inhibitors targeting Notch1, Akt, and Foxo1. The expression profiles of the aforementioned proteins and genes in the four groups were then examined, with hESC induced for decidualization without adding inhibitors serving as the normal control group. To establish murine models of normal pregnancy (NP) and RSA, CBA/J×BALB/c and CBA/J×DBA/2 mice were used. The mice were respectively labeled as the NP model and RSA model. The experimental groups received intraperitoneal injections of kisspeptin10 and kisspeptin234 (acting as a blocker) and were designated as RSA-KP10 and NP-KP234 groups. On the other hand, the control groups received intraperitoneal injections of normal saline (NS) and were referred to as RSA-NS and NP-NS groups. Each group comprised 6 mice, and uterine tissues from embryos at 9.5 days of gestation were meticulously collected for observation of embryo absorption and examination of the expression of the aforementioned proteins and genes.

Results

The analysis revealed that the expression levels of kisspeptin, IGFBP1, Notch1, Akt, and Foxo1 were significantly lower in patients diagnosed with RSA compared to those in women with NP (P<0.01 for kisspeptin and P<0.05 for IGFBP1, Notch1, Akt, and Foxo1). After the introduction of kisspeptin10 to hESC, there was an observed enhancement in decidualization capability. Subsequently, the expression levels of Notch1, Akt, and Foxo1 showed an increase, but they decreased after interference with KISS1. Through immunofluorescence analysis, it was observed that proliferative hESC displayed a slender morphology, but they transitioned to a rounder and larger morphology post-decidualization. Concurrently, the expression of Notch1 increased, suggesting enhanced decidualization upon the administration of kisspeptin10, but the expression decreased after interference with KISS1. Further experimentation involved treating hESC with inhibitors specific to Notch1, Akt, and Foxo1 separately, revealing a regulatory sequence of Notch1/Akt/Foxo1 (P<0.05). In comparison to the NS group, NP mice administered with kisspeptin234 exhibited increased fetal absorption rates (P<0.001) and decreased expression of IGFBP1, Notch1, Akt, and Foxo1 (P<0.05). Conversely, RSA mice administered with kisspeptin10 demonstrated decreased fetal absorption rates (P<0.001) and increased expression levels of the aforementioned molecules (P<0.05).

Conclusion

It is suggested that kisspeptin might exert its regulatory influence on the process of decidualization through the modulation of the Notch1/Akt/Foxo1 signaling cascade. A down-regulation of the expression levels of kisspeptin could result in suboptimal decidualization, which in turn might contribute to the development or progression of RSA.

Time and dose-dependent effects of FGF8-FGFR1 signaling in GnRH neurons derived from human pluripotent stem cells

Fibroblast growth factor 8 (FGF8), acting through the fibroblast growth factor receptor 1 (FGFR1), has an important role in the development of gonadotropin-releasing hormone-expressing neurons (GnRH neurons). We hypothesized that FGF8 regulates differentiation of human GnRH neurons in a time- and dose-dependent manner via FGFR1. To investigate this further, human pluripotent stem cells were differentiated during 10 days of dual-SMAD inhibition into neural progenitor cells, followed either by treatment with FGF8 at different concentrations (25 ng/ml, 50 ng/ml or 100 ng/ml) for 10 days or by treatment with 100 ng/ml FGF8 for different durations (2, 4, 6 or 10 days); cells were then matured through DAPT-induced inhibition of Notch signaling for 5 days into GnRH neurons. FGF8 induced expression of GNRH1 in a dose-dependent fashion and the duration of FGF8 exposure correlated positively with gene expression of GNRH1 (P<0.05, Rs=0.49). However, cells treated with 100 ng/ml FGF8 for 2 days induced the expression of genes, such as FOXG1, ETV5 and SPRY2, and continued FGF8 treatment induced the dynamic expression of several other genes. Moreover, during exposure to FGF8, FGFR1 localized to the cell surface and its specific inhibition with the FGFR1 inhibitor PD166866 reduced expression of GNRH1 (P<0.05). In neurons, FGFR1 also localized to the nucleus. Our results suggest that dose- and time-dependent FGF8 signaling via FGFR1 is indispensable for human GnRH neuron ontogeny.

This article has an associated First Person interview with the first author of the paper.

Summary: This article demonstrates the essential role FGF8–FGFR1 signaling has in the development of gonadotropin-releasing hormone (GnRH)-expressing neurons by using a human stem cell model.

Physiological Characterization and Transcriptomic Properties of GnRH Neurons Derived From Human Stem Cells

Gonadotropin-releasing hormone (GnRH) neurons in the hypothalamus play a key role in the regulation of reproductive function. In this study, we sought an efficient method for generating GnRH neurons from human embryonic and induced pluripotent stem cells (hESC and hiPSC, respectively). First, we found that exposure of primitive neuroepithelial cells, rather than neuroprogenitor cells, to fibroblast growth factor 8 (FGF8), was more effective in generating GnRH neurons. Second, addition of kisspeptin to FGF8 further increased the efficiency rates of GnRH neurogeneration. Third, we generated a fluorescent marker mCherry labeled human embryonic GnRH cell line (mCh-hESC) using a CRISPR-Cas9 targeting approach. Fourth, we examined physiological characteristics of GnRH (mCh-hESC) neurons: similar to GnRH neurons in vivo, they released the GnRH peptide in a pulsatile manner at ~60 min intervals; GnRH release increased in response to high potassium, kisspeptin, estradiol, and neurokinin B challenges; and injection of depolarizing current induced action potentials. Finally, we characterized developmental changes in transcriptomes of GnRH neurons using hESC, hiPSC, and mCh-hESC. The developmental pattern of transcriptomes was remarkably similar among the 3 cell lines. Collectively, human stem cell-derived GnRH neurons will be an important tool for establishing disease models to understand diseases, such as idiopathic hypothalamic hypogonadism, and testing contraceptive drugs.

Neonatal overfeeding reduces estradiol plasma levels and disrupts noradrenergic-kisspeptin-GnRH pathway and fertility in adult female rats

This work evaluated the effects of neonatal overfeeding, induced by litter size reduction, on fertility and the noradrenaline-kisspeptin-gonadotrophin releasing hormone (GnRH) pathway in adult female rats. The litter size was adjusted to 3 pups with each mother in the small litters (SL) and 10 pups with each mother in the normal litters (NL). SL females exhibited metabolic changes associated with reproductive dysfunctions, shown by earlier vaginal opening and first estrus, later regular cyclicity onset, and lower and higher occurrences of estrus and diestrus phases, respectively, as well as reduced fertility, estradiol plasma levels, and mRNA expressions of tyrosine hydroxylase in the locus coeruleus, kisspeptin, and GnRH in the preoptic area in adult females in the afternoon of proestrus. These results suggest that neonatal overfeeding in female rats promotes reproductive dysfunctions in adulthood, such as lower estradiol plasma levels associated with impairments in fertility and noradrenaline-kisspeptin-GnRH pathway during positive feedback.

MiR-199-3p modulates the onset of puberty in rodents probably by regulating the expression of Kiss1 via the p38 MAPK pathway

The Kiss1 gene plays an indispensable role in modulating the onset of puberty and fertility in mammals. Although an increasing number of genetic and environmental factors that influence reproduction through Kiss1 have been identified, the function of microRNAs, a class of posttranscriptional regulators, in regulating Kiss1 expression remains poorly understood. This study aimed at investigating the mechanism by which Kiss1 expression is regulated by microRNAs. A simplified miRNome screen by a dual-fluorescence reporter system based on Kiss1 was performed to identify microRNAs that affect the expression of Kiss1. The expression patterns of the identified microRNAs during the period of murine sexual development were investigated, and only miR-199-3p was studied further. Aided by bioinformatics algorithms, miR-199-3p was demonstrated to be a repressor of Kiss1 expression, as it blocked the expression of Kiss1 through the p38 MAPK pathway by simultaneously inhibiting several targets in both GT1-7 cells and primary hypothalamic neurons. Both the inhibition of the p38 MAPK pathway by the intracerebroventricular administration of chemical agents in rats and the ectopic expression of miR-199-3p by lentivirus injection in the hypothalamus in mice delayed puberty onset and gonad development. Our results presented a novel regulatory mechanism of puberty onset which the sustained downregulation of miR-199-3p might gradually release the inhibition of the p38 MAPK/Fos/CREB/Kiss1 pathway during puberty development.

Dopamine-induced interactions of female mouse hypothalamic proteins with progestin receptor-A in the absence of hormone

Neural progestin receptors (PR) function in reproduction, neural development, neuroprotection, learning, memory and the anxiety response. In the absence of progestins, PR can be activated by dopamine (DA) in the rodent hypothalamus to elicit female sexual behaviour. The present study investigated mechanisms of DA activation of PR by testing the hypothesis that proteins from DA-treated hypothalami interact with PR in the absence of progestins. Ovariectomised, oestradiol-primed mice were infused with a D1-receptor agonist, SKF38393 (SKF), into the third ventricle 30 minutes prior to death. Proteins from SKF-treated hypothalami were pulled-down with glutathione S-transferase-tagged mouse PR-A or PR-B and the interactomes were analysed by mass spectrometry. The largest functional group to interact with PR-A in a DA-dependent manner was synaptic proteins. To test the hypothesis that DA activation of PR regulates synaptic proteins, we developed oestradiol-induced PR-expressing hypothalamic-like neurones derived from human-induced pluripotent stem cells (hiPSCs). Similar to progesterone (P4), SKF treatment of hiPSCs increased synapsin1/2 expression. This SKF-dependent effect was blocked by the PR antagonist RU486, suggesting that PR are necessary for this DA-induced increase. The second largest DA-dependent PR-A protein interactome comprised metabolic regulators involved in glucose metabolism, lipid synthesis and mitochondrial energy production. Interestingly, hypothalamic proteins interacted with PR-A, but not PR-B, in an SKF-dependent manner, suggesting that DA promotes the interaction of multiple hypothalamic proteins with PR-A. These in vivo and in vitro results indicate novel mechanisms by which DA can differentially activate PR isoforms in the absence of P4 and provide a better understanding of ligand-independent PR activation in reproductive, metabolic and mental health disorders in women.

Apelin Receptor Signaling Protects GT1-7 GnRH Neurons Against Oxidative Stress In Vitro

Hypothalamic-pituitary-adrenal (HPA) axis regulates stress response in the body and abnormal increase in oxidative stress contributes to the various disease pathogenesis. Although hypothalamic distribution of Apelin receptor (APLNR) has been studied, the potential regulatory role in hormone releasing function of hypothalamus in response to stress is not well elucidated yet. To determine whether APLNR is involved in the protection of the hypothalamus against oxidative stress, gonadotropin-releasing hormone (GnRH) cells were used as an in vitro model system. GT1-7 mouse hypothalamic neuronal cell line was subjected to H₂O₂ and hypoxia induced oxidative stress under various circumstances including APLNR overexpression, knockdown and knockout. Overexpression and activation of APLNR in GnRH producing neurons caused an increase in cell proliferation under oxidative stress. In addition, blockage of APLNR function by siRNA reduced GnRH release. Activation of APLNR initiated AKT kinase pathway as a proliferative response against hypoxic culture conditions and blocked apoptosis. Although expression and activation of APLNR have not been related to GnRH neuron differentiation during development, positive contribution of activated APLNR signaling to GnRH release in mouse embryonic stem cell derived GnRH neurons was observed in the present study. Sustained overexpression and complete deletion of APLNR in mouse embryonic stem cell derived GnRH neurons reduced GnRH release in vitro. The present findings suggest that expression and activation of APLNR in GnRH releasing GT1-7 neurons might induce a protective mechanism against oxidative stress induced cell death and APLNR signaling may play a role in GnRH neurons.

The Emerging Key Role of Klotho in the Hypothalamus-Pituitary-Ovarian Axis

The hypothalamus-pituitary-ovary axis is the most important system for regulating female reproductive endocrine function. Its dysfunction would lead to the abnormal secretion of gonadotropin-releasing hormone, follicle-stimulating hormone, or luteinizing hormone, and eventually result in the occurrence of reproductive disease, such as congenital hypogonadotropic hypogonadism, polycystic ovary syndrome, and premature ovarian failure. Recently, an anti-aging gene, Klotho, has gained broad attention in female reproductive diseases. Reports have shown that Klotho is closely correlated to the hypothalamus-pituitary-ovary axis and plays a key role in the development and progression of reproductive diseases. With this issue, we generally review the physiological and pathological role of Klotho in the hypothalamus-pituitary-ovary axis. We also review the underlying mechanisms of Klotho in promoting and preventing female reproductive diseases, which involve the dysfunction of the fibroblast growth factor-Klotho endocrine system, the abnormal signaling regulation of Wnt-β-catenin and insulin-like growth factor-1, the accumulation of oxidative stress, and the inhibition of autophagy, eventually affecting the genesis, development, ovulation, or atresia of follicles. The present review would provide new insights and potential therapeutic target strategies for clinical strategies.

GHR gene transcript heterogeneity may explain phenotypic variability in GHR pseudoexon (6Ψ) patients

OBJECTIVES

The homozygous GH receptor (GHR) pseudoexon (6Ψ) mutation leads to growth hormone insensitivity (GHI) with clinical and biochemical heterogeneity. We investigated whether transcript heterogeneity (6Ψ-GHR to WT-GHR transcript ratio) and/or concurrent defects in other short stature (SS) genes contribute to this.

METHODS

6Ψ-GHR and WT-GHR mRNA transcripts of 4 6Ψ patient (height SDS -4.2 to -3.1) and 1 control fibroblasts were investigated by RT-PCR. Transcripts were quantified by qRT-PCR and delta delta CT analysis and compared using ANOVA with Bonferroni correction. In eleven 6Ψ patients, 40 genes known to cause GHI/SS were analysed by targeted next generation sequencing.

RESULTS

RT-PCR confirmed 6Ψ-GHR transcript in the 6Ψ patients but not control. 6Ψ-GHR transcript levels were comparable in patients 1 and 3 but significantly different among all other patients. The mean 6Ψ:WT transcript ratios ranged from 29-71:1 for patients 1-4 and correlated negatively with height SDS (R=-0.85; p<0.001). Eight deleterious variants in 6 genes were detected but the number of gene hits did not correlate with the degree of SS in individual 6Ψ patients.

CONCLUSION

Variable amounts of 6Ψ- and WT-GHR transcripts were identified in 6Ψ patients but no 6Ψ transcript was present in the control. Higher 6Ψ:WT GHR transcript ratio correlated with SS severity and may explain the phenotypic variability. Analysis of known SS genes suggested that phenotypic variation is independent of the genetic background. This is the first report of transcript heterogeneity producing a spectrum of clinical phenotypes in different individuals harbouring an identical homozygous genetic mutation.

Predicted Benign and Synonymous Variants in CYP11A1 Cause Primary Adrenal Insufficiency Through Missplicing

Primary adrenal insufficiency (PAI) is a potentially life-threatening condition that can present with nonspecific features and can be difficult to diagnose. We undertook next generation sequencing in a cohort of children and young adults with PAI of unknown etiology from around the world and identified a heterozygous missense variant (rs6161, c.940G>A, p.Glu314Lys) in CYP11A1 in 19 individuals from 13 different families (allele frequency within undiagnosed PAI in our cohort, 0.102 vs 0.0026 in the Genome Aggregation Database; P < 0.0001). Seventeen individuals harbored a second heterozygous rare disruptive variant in CYP11A1 and two had very rare synonymous changes in trans (c.990G>A, Thr330 = ; c.1173C>T, Ser391 =). Although p.Glu314Lys is predicted to be benign and showed no loss-of-function in an Escherichia coli assay system, in silico and in vitro studies revealed that the rs6161/c.940G>A variant, plus the c.990G>A and c.1173C>T changes, affected splicing and that p.Glu314Lys produces a nonfunctional protein in mammalian cells. Taken together, these findings show that compound heterozygosity involving a relatively common and predicted "benign" variant in CYP11A1 is a major contributor to PAI of unknown etiology, especially in European populations. These observations have implications for personalized management and demonstrate how variants that might be overlooked in standard analyses can be pathogenic when combined with other very rare disruptive changes.

A dual fluorescence reporter system for high throughput screening of effectors of Kiss1 gene expression

Kisspeptin is a multifunctional peptide encoded by the Kiss1 gene that plays critical roles in mammalian puberty onset modulation and fertility maintenance in the hypothalamus. Understanding how Kiss1 expression is regulated is essential for elucidating the molecular mechanisms responsible for these reproductive events. In this study, we constructed an in vitro dual fluorescence reporter system to facilitate high throughput screening of effectors influencing the expression of Kiss1. In GT1‐7 cells, an enhanced GFP gene was placed under the control of the Kiss1 gene regulatory elements and translated together with this gene. A tdTomato gene cassette was simultaneously introduced into the same cell for normalization of the fluorescence signal. After treatment with different effectors, the cells were analyzed by flow cytometry. We first tested the efficacy of the system using canonical regulators and then carried out high throughput functional screening to identify chemical compounds that can regulate Kiss1 gene expression. Of 22 tested compounds from natural sources, 13 significantly affected Kiss1 expression. Verification by western blot and quantitative reverse transcription PCR (qRT‐PCR) assays and structural analysis identified two chalcone compounds as possible regulators of Kiss1 gene expression. This system may be suitable for gene functional analysis, drug screening and pharmaceutical studies.

KLB, encoding β-Klotho, is mutated in patients with congenital hypogonadotropic hypogonadism

Congenital hypogonadotropic hypogonadism (CHH) is a rare genetic form of isolated gonadotropin‐releasing hormone (GnRH) deficiency caused by mutations in > 30 genes. Fibroblast growth factor receptor 1 (FGFR1) is the most frequently mutated gene in CHH and is implicated in GnRH neuron development and maintenance. We note that a CHH FGFR1 mutation (p.L342S) decreases signaling of the metabolic regulator FGF21 by impairing the association of FGFR1 with β‐Klotho (KLB), the obligate co‐receptor for FGF21. We thus hypothesized that the metabolic FGF21/KLB/FGFR1 pathway is involved in CHH. Genetic screening of 334 CHH patients identified seven heterozygous loss‐of‐function KLB mutations in 13 patients (4%). Most patients with KLB mutations (9/13) exhibited metabolic defects. In mice, lack of Klb led to delayed puberty, altered estrous cyclicity, and subfertility due to a hypothalamic defect associated with inability of GnRH neurons to release GnRH in response to FGF21. Peripheral FGF21 administration could indeed reach GnRH neurons through circumventricular organs in the hypothalamus. We conclude that FGF21/KLB/FGFR1 signaling plays an essential role in GnRH biology, potentially linking metabolism with reproduction.

Modeling Congenital Adrenal Hyperplasia and Testing Interventions for Adrenal Insufficiency Using Donor-Specific Reprogrammed Cells

Adrenal insufficiency is managed by hormone replacement therapy, which is far from optimal; the ability to generate functional steroidogenic cells would offer a unique opportunity for a curative approach to restoring the complex feedback regulation of the hypothalamic-pituitary-adrenal axis. Here, we generated human induced steroidogenic cells (hiSCs) from fibroblasts, blood-, and urine-derived cells through forced expression of steroidogenic factor-1 and activation of the PKA and LHRH pathways. hiSCs had ultrastructural features resembling steroid-secreting cells, expressed steroidogenic enzymes, and secreted steroid hormones in response to stimuli. hiSCs were viable when transplanted into the mouse kidney capsule and intra-adrenal. Importantly, the hypocortisolism of hiSCs derived from patients with adrenal insufficiency due to congenital adrenal hyperplasia was rescued by expressing the wild-type version of the defective disease-causing enzymes. Our study provides an effective tool with many potential applications for studying adrenal pathobiology in a personalized manner and opens venues for the development of precision therapies.

Comparison of fusion protein and DC vaccine in inhibition of mouse B16F10 melanoma tumor

Dendritic cell (DC) vaccine and fusion protein vaccine have been put into clinical use in cancer immunotherapy. This study compared DC vaccine and fusion protein vaccine directly in their capability of inducing specific immune response. We used mouse Granulocyte Macrophage-Colony Stimulating Factor (mGM-CSF) fused with gastrin-releasing peptide (GRP) and Gonadotrophin Releasing Hormone (GnRH) respectively to obtain mGM-CSF/GRP6 (mG6) and mGM-CSF/mGGn (mGGn) fusion proteins. We prepared fusion protein vaccine and DC vaccine including mG6 protein vaccine (6P), mGGn protein vaccine (nP), mG6 DC vaccine (6D) and mGGn DC vaccine (nD), then the two proteins were mixed to prepare combination proteins vaccine (6nP) and DC vaccine (6nD). After that, C57BL/6 mice were injected with B16F10 cell line to build melanoma tumor model, and were immunized with vaccines to produce antibodies to inhibit and destruct melanoma tumor cells. The discoveries showed that anti- mGM-CSF-GRP6 and anti- mGM-CSF-mGGn antibody vaccines were successfully created as expected; this was deduced from significant inhibition of melanoma tumor in vivo and significant reduction of tumor weight and volume. The effects of DC groups were better than that of the protein groups and the combination of vaccines were more effective than vaccine given separately. Our results indicate that using combination vaccine provides a new strategy to inhibit melanoma tumor growth but a complete cure of melanoma needs further investigations.