Unusual suspects: Glial cells in fertility regulation and their suspected role in polycystic ovary syndrome

Altered GnRH neuron-glia networks close to interface of polycystic ovary syndrome: Molecular mechanism and clinical perspectives

Polycystic ovary syndrome (PCOS) has been noticed as a neuroendocrine syndrome manifested by reproductive hormone dysregulation involving increased luteinizing hormone (LH) pulse frequency and an increased LH to follicle-stimulating hormone ratio, yet theory is just beginning to be established. Neuroglia located in the arcuate nucleus and median eminence (ARC-ME) that are close to gonadotropin-releasing hormone (GnRH) axon terminals, comprise the blood-brain barrier and fenestrated vessels implying their putative roles in the modulation of the abnormal GnRH pulse in PCOS. This review outlines the disturbances of neuron-glia networks that underlie hypothetically the deregulation of GnRH-LH release and impaired sex hormone negative feedback in PCOS. We then discuss chronic and low-grade inflammatory status together with gut dysbiosis and how the detriments may intrude the hypothalamus by virtue of violating interfaces between the brain and periphery, which might contribute to the etiology of the impaired neural circuits in the ARC-ME to induce PCOS.

SIRT2-dependent DKK1 deacetylation aggravates polycystic ovary syndrome by targeting the TGF-β1/Smad3 signaling pathway

BACKGROUND

Polycystic ovarian syndrome (PCOS) is a prevalent metabolic and endocrine condition in females of reproductive age. This work was to discover the underlying role of Dickkopf 1 (DKK1) and its putative regulating mechanism in P COS.

METHODS

Mice recieved dehydroepiandrosterone (DHEA) injection to establish the in vivo P COS model.Hematoxylin and eosin (H&E) staining was performed for histological analysis. RT-qP CR and Western blotting were used to detect gene and protein expression. CCK-8 and flow cytometry assays were applied to detect cell viability and apoptosis. Co-immunoprecipitation (Co-IP) and immunoprecipitation (IP) were applied to assess association between DKK1 and SIRT2.

RESULTS

In this work, DKK1 is downregulated in P COS rats. It was revealed that DKK1 knockdown induced apoptosis and suppressed proliferation in KGN cells, whereas DKK1 overexpression had exactly the opposite effects. In addition, DKK1 deactivates the T GF-β1/SMad3 signaling pathway, thereby controlling KGN cell proliferation and apoptosis. Besides, SIRT2 inhibition reversed the impact of DKK1 overexpression on KGN cell proliferation and apoptosis. Furthermore, SIRT2 downregulated DKK1 expression by deacetylating DKK1 in KGN cells.

DISCUSSION

Altogether, we concluded that SIRT2-induced deacetylation of DKK1 triggers T GF-β1/Smad3 hyperactivation, thereby inhibiting proliferation and promoting apoptosis of KGN cells. The above results indicated that DKK1 might function as a latent target for P COS treatment.

Troxerutin dampened hypothalamic neuroinflammation via microglial IL-22/IL-22R1/IRF3 activation in dihydrotestosterone-induced polycystic ovary syndrome rats

BACKGROUND

Polycystic ovary syndrome (PCOS) is the most common reproductive-endocrine condition in premenopausal women. Troxerutin, a common clinical anti-coagulant agent, was shown to work as a strong IL-22 boosting agent counteracting the hyperactivated gonadotrophin releasing hormone (GnRH) neurons and heightened GnRH release, the neuroendocrine origin of PCOS with unknown mechanism in rats. Exploring the off-label use of troxerutin medication for PCOS is thus sorely needed.

METHODS

Serum IL-22 content and hypothalamic IL-22 protein were detected. Inflammatory factor levels in hypothalamo-pituitary were evaluated. Immunofluorescence staining was employed to determine the activation and M1/M2-prone polarization of microglia in arcuate hypothalamus and median eminence. RNA-sequencing and transcriptome analysis were applied to explore the potential driver of microglia M2-polarization in response to IL-22 bolstering effect. The function of microglial IL-22/IL-22R1/IRF3 system was further verified using in vivo knockdown of IL-22R1 and a potent IRF3 inhibitor in BV2 microglial cell lines in vitro.

RESULTS

Troxerutin augmented serum IL-22 content, and its consequent spillover into the hypothalamus led to the direct activation of IL-22R1/IRF3 system on microglia, thereby promoted microglia M2 polarization in arcuate hypothalamus and median eminence, dampened hypothalamic neuroinflammation, inhibited hyperactive GnRH and rescued a breadth of PCOS-like traits in dihydrotestosterone (DHT) rats. The salutary effects of troxerutin treatment on hypothalamic neuroinflammation, microglial M1/2 polarization, GnRH secretion and numerous PCOS-like features were blocked by in vivo knockdown of IL-22R1. Moreover, evidence in vitro illustrated that IL-22 supplement to BV-2 microglia cell lines promoted M2 polarization, overproduction of anti-inflammatory marker and limitation of pro-inflammatory factors, whereas these IL-22 effects were blunted by geldanamycin, a potent IRF3 inhibitor.

CONCLUSION

Here, the present study reported the potential off-label use of troxerutin medication, a common clinical anti-coagulant agent and an endogenous IL-22 enhancer, for multiple purposes in PCOS. The rational underlying the application of troxerutin as a therapeutic choice in PCOS derived from its activity as an IL-22 memetic agent targeting the neuro-endocrine origin of PCOS, and its promotive impact on microglia M2 polarization via activating microglial IL-22R1/IRF3 system in the arcuate hypothalamus and median eminence of DHT female rats.

SEMA6A drives GnRH neuron-dependent puberty onset by tuning median eminence vascular permeability

Innervation of the hypothalamic median eminence by Gonadotropin-Releasing Hormone (GnRH) neurons is vital to ensure puberty onset and successful reproduction. However, the molecular and cellular mechanisms underlying median eminence development and pubertal timing are incompletely understood. Here we show that Semaphorin-6A is strongly expressed by median eminence-resident oligodendrocytes positioned adjacent to GnRH neuron projections and fenestrated capillaries, and that Semaphorin-6A is required for GnRH neuron innervation and puberty onset. In vitro and in vivo experiments reveal an unexpected function for Semaphorin-6A, via its receptor Plexin-A2, in the control of median eminence vascular permeability to maintain neuroendocrine homeostasis. To support the significance of these findings in humans, we identify patients with delayed puberty carrying a novel pathogenic variant of SEMA6A. In all, our data reveal a role for Semaphorin-6A in regulating GnRH neuron patterning by tuning the median eminence vascular barrier and thereby controlling puberty onset.

Investigation of the Effects of Metallic Nanoparticles on Fertility Outcomes and Endocrine Modification of the Hypothalamic-Pituitary-Gonadal Axis

Nanotechnology is a very disruptive twenty-first-century revolution that will allow social and economic welfare to increase although it also involves a significant human exposure to nanoparticles. The aim of the present study was to contribute to the elucidation on whether metallic nanoparticles have a potential to induce fertility impairments. Regulatory studies that observed official OECD guidelines 415, 416 and 422 have failed to detect any fertility alterations caused by nanoparticle exposure. However, the scientific literature provides evidence that some nanoparticles may cause gonad impairments although the actual impact on fertility remains uncertain. This aim of the present study is to revisit the previously published RNAseq studies by analyzing the effects of several nanoparticles on the transcriptome of T98G human glioblastoma cells given that glial cells are known to play a pivotal role in the regulation of gonadotropin releasing hormone neurons. We found evidence that nanoparticles impair the gonadotropin releasing hormone receptor pathway and several related biological process like, among others, the cellular response to follicular stimulating hormone, cellular response to gonadotropin stimulus, cellular response to hormone stimulus, response to steroid hormone, ovulation cycle and response to estradiol. We propose that nanoparticles interfere with the ability of glial cells to regulate gonadotropin-releasing hormone neurons and, subsequently, the hypothalamic-pituitary-gonadal axis, potentially leading to fertility impairments. To our knowledge, this is the first proposal of a mode of action based on endocrine disruption for explaining the possible effects of nanoparticles on fertility. Whether these finding can be extended to other types of nanoparticles requires further investigation.