Abstract Tanycytes are radial-glia-like cells that play important roles in regulating the neuroendocrine system and metabolism. Synapse-like (synaptoid) connections have previously been described between neurons and tanycytes, but their structure and function are unclear. Here, we report that neuron-tanycyte synaptoids are abundant and resemble typical neuronal synapses in shape and composition. Tanycytic subtypes receive specific inputs from a variety of hypothalamic as well as extrahypothalamic neuronal populations and respond to several neurotransmitters and neuromodulators. As proof-of-principle of their functional relevance, we demonstrate in mice, that two distinct populations of kisspeptin neurons, which stimulate the gonadotropic axis, innervate different tanycytic subsets of the mediobasal hypothalamus to control basal levels of the gonadotropin luteinizing hormone (LH) and its pulsatile release pattern, in a sex‑ and region‑specific manner. Neuron-tanycyte synaptoid connections are thus widespread, diverse and functionally specific elements of hypothalamic neural circuits that play a key role in finetuning hormonal axes.

Structural and functional insights into the mouse hypothalamus are hampered by its small size and deep location. Here, we leverage ultra-high-field magnetic resonance imaging (UHF-MRI) at 17.2 Tesla to achieve unprecedented spatial resolution in structural, functional and neurochemical imaging of the mouse hypothalamus, including sexual dimorphism in certain nuclei. High-resolution ex vivo anatomical MRI enabled precise hypothalamic parcellation, improving on existing atlases and revealing nuclei previously unresolved by MRI. Diffusion MRI and tractography mapped intra- and extra-hypothalamic pathways, facilitating circuit-level exploration without a priori assumptions. Resting-state fMRI combined with independent component analysis identified novel hypothalamic networks, demonstrating the enhanced capacity of UHF MRI to detect deep-brain activity. Proton magnetic resonance spectroscopy quantified neurochemical profiles, revealing sexually dimorphic heterogeneity within the hypothalamus. Our comprehensive multimodal approach uncovers sex differences in hypothalamic anatomy, microstructure, and neurochemistry, emphasizing the importance of sex as a biological variable. This integrated pipeline offers a valuable resource for dissecting hypothalamic circuits and functions, advancing our understanding of neuroendocrine regulation, behavior, and disease mechanisms, with direct translational relevance. ### Competing Interest Statement The authors have declared no competing interest. Agence Nationale de la Recherche, https://ror.org/00rbzpz17, ANR-24-CE16-3311

Liraglutide, a glucagon-like peptide-1 receptor (GLP-1R) agonist for type 2 diabetes and obesity management, shows variable patient responses. We investigated the metabolic state-dependent mechanisms underlying this heterogeneity and how liraglutide’s mode of action shifts across stages of metabolic dysfunction. We employed human pancreatic islets from donors across metabolic states (normoglycaemic [HbA1c <42 mmol/l (<6.0

BACKGROUND:Cerebral small vessel disease (cSVD) is a major cause of stroke and dementia, and is associated with increased blood-brain barrier permeability, neuroinflammation, and endothelial dysfunction. Endothelial Gαq/11 proteins are involved in vascular tone regulation and have been shown to affect capillary blood flow in the brain. Since factors downstream of activated Gαq/11 proteins, such as endothelial NO synthase (eNOS) activity, are discussed in cSVD, we asked whether the brain endothelial Gαq/11 signalling pathway might influence cSVD-related pathology. METHODS:Here, we generated mice carrying a brain endothelial-specific deletion of the Gαq/11 signalling and characterised these mice using different imaging and staining techniques, as well as behaviour tests measuring cognition in adult and aged mice. Immunoblots, electrophysiology, perfusion measurements, and in vitro experiments complemented those techniques. FINDINGS:The brain endothelial Gαq/11 signalling pathway preserves normal vascular reactivity, and its loss resembles mild endothelial dysfunction in the brain. While the vessel structure was maintained in adult mice, deletion of Gαq/11 signalling led to capillary rarefaction and blood-brain barrier disruption in aged mice. These effects were accompanied by disturbed VEGF signalling and an increase in senescence markers and oxidative stress in the vasculature, culminating in cognitive impairment with increased tau phosphorylation in the cortex and hippocampus and decreased myelination in the white matter. INTERPRETATION:These findings reflect the main hallmarks of cSVD and demonstrate a protective role of Gαq/11 in endothelial cells in ageing. Furthermore, our results show that the combination of cerebral endothelial dysfunction and ageing accelerates cognitive impairment. FUNDING:Research was supported by grants from the European Research Council, the Deutsche Forschungsgemeinschaft, the institutional priority program MI-VascAD of the University of Lübeck, and the Marie-Sklodowska-Curie European Union's Horizon 2020 research program.

The hypothalamic-pituitary-gonadal axis (HPG) controls pubertal development, sexual maturation, and fertility. We identified a role of hypothalamic microglia in controlling the HPG axis through receptor activator of nuclear factor κB (Rank) signaling. Whole-body and microglia Rank (mouse) depletion led to hypogonadotropic hypogonadism (HH) resulting from an alteration in gonadotropin-releasing hormone (GnRH) neuron function. In addition, we identified rare gene variants of RANK (human) in patients with HH. Transcriptional profiling upon Rank loss revealed defective microglia activation and morphological alterations in the median eminence, decreasing the contacts and engulfment of GnRH terminal projections and impairing GnRH neuronal responses to kisspeptin. Overall, our data uncover the microglia as regulator of GnRH neuronal function through Rank signaling, with potential implications for reproductive maturation and fertility.

The human nasal region arises from neural crest and placodal lineages, yet its early development remains poorly understood owing to limited fetal tissue access and structural complexity. Here we present an integrated single-nucleus and spatial transcriptomic atlas of the human fetal nasal region, generated from male and female fetuses between 7 and 12 post-conceptional weeks. Single-nucleus RNA sequencing [snRNA-seq] resolved 32 distinct cell types, while integration with multiplexed error-robust fluorescence in situ hybridization (MERFISH) enabled spatial and temporal mapping of gene expression dynamics across the olfactory epithelium (OE) and adjacent tissues. We identify markers of olfactory sensory neuron differentiation and pathways governing epithelial patterning and OE morphogenesis. Notably, spatially resolved snRNA-seq profiles of 169 olfactory receptor genes reveal molecular support for the "one neuron-one receptor" principle already in the first trimester. Together, this work establishes a molecular and spatial framework of early human olfactory development and provides a resource for studies of sensory neurogenesis and congenital disorders.

Vascular endothelial growth factors (VEGFs) and their receptors (VEGFRs) are critical regulators of angiogenesis and vascular homeostasis. While VEGF signaling has been extensively studied in endothelial cells, emerging evidence suggests it also plays roles in non-endothelial brain cells. However, its spatial and cell-type-specific function within the hypothalamus, and more specifically at the level of the blood/CSF barrier, remains poorly defined. In particular, little is known about VEGF receptor expression in tanycytes, a specialized glial population that lines the third ventricle and regulates body-brain communication within the median eminence (ME), a key neurovascular interface located at the tuberal region of the hypothalamus. We used a multi-modal approach including single-cell RNA sequencing (scRNA-seq) reanalysis, RNAscope in situ hybridization, immunohistochemistry, FACS-isolated qPCR in male and female mice, and human spatial transcriptomics to map the expression of VEGFR1 (Flt1), VEGFR2 (Kdr), and VEGF ligands in hypothalamic tanycytes across gender, development, and aging. Our data reveal a striking spatial compartmentalization of VEGFR expression in tanycytes within the ME and the arcuate (ARH), ventromedial (VMH) and dorsomedial (DMH) hypothalamus. VEGFR2 is preferentially expressed in ARH-tanycytes, while VEGFR1 is confined to VMH/DMH-tanycytes; and none of these receptors are expressed in ME-tanycytes. This pattern is unique to the ME and not observed in other circumventricular organs. VEGFR1 expression is established neonatally in mice (P0) and remains stable throughout life, whereas VEGFR2 expression becomes progressively refined postnatally, localizing to ARH-tanycytes in adulthood and showing a significant decline with aging. VEGFA is broadly expressed in all hypothalamic tanycytes, including ME-tanycytes, supporting a paracrine model of signaling. Importantly, despite species-specific differences in the spatial organization of VEGF receptors in tanycytes, the presence of VEGF ligands (Vegfa and Vegfb) and receptors in tanycytes of both mice and humans supports partial evolutionary conservation of VEGF signaling at the brain–blood interface. Our findings unveil, for the first time a non-endothelial VEGF signaling system in hypothalamic tanycytes that is spatially compartmentalized, developmentally programmed and age-dependent. These insights reveal new roles for VEGF signaling in neurovascular and neuroendocrine function, raising important considerations for central effects of VEGF-targeted therapies in aging and disease.

Introduction and Objective: Tanycytes are specialized ependymoglial cells lining the third ventricle that sense peripheral metabolic signals and relay them to the hypothalamus. LRP2 (Low-Density Lipoprotein Receptor-Related Protein 2) is expressed in tanycytes and has been implicated in the uptake/transport of circulating signals into the brain. However, the role of LRP2 in glucose metabolism remains unknown. Here, we investigated whether tanycytic LRP2 contributes to systemic glucose regulation and whether this effect engages steroidogenic factor 1 (SF1) neurons in the ventromedial hypothalamus (VMH). Methods: To selectively suppress LRP2 in tanycytes, we used a Cre-dependent AAV knockdown strategy. Cre-dependent AAV1/2-shLRP2-eGFP was co-injected with an AAV-Dio2-Cre (to drive Cre expression in tanycytes) into the 3rd ventricle of adult mice, generating LRP2TanKD mice. We confirmed that LRP2 expression in tanycytes of the median eminence was reduced by ~80% over controls. Results: LRP2TanKD mice displayed a 34% increase in body weight compared to controls at 20 weeks post-injection without changes in food intake. This weight gain was driven by an increase in lean mass rather than fat mass. Despite greater body weight, LRP2TanKD mice showed improved glucose tolerance on a chow diet, as evidenced by a lower AUC during the GTT. This effect is associated with enhanced glucose-stimulated insulin secretion. Concurrently, increased insulin sensitivity was also detected in LRP2TanKD mice. Importantly, suppression of tanycytic LRP2 leads to a marked increase in SF1 and c-fos gene expression, indicating enhanced SF1 neuronal activity. By deleting SF1 in the VMH, we found that the improvement in glucose tolerance and insulin sensitivity in LRP2TanKD mice is restored to normal levels, suggesting a functional connection between tanycytic LRP2 and SF1 neurons. Conclusion: Our findings demonstrate that tanycytic LRP2 modulates systemic glucose metabolism by regulating SF1 neuron activity in the VMH, highlighting a novel tanycyte-neuron crosstalk for maintaining glucose homeostasis. Disclosure F. Timzoura: None. I. Martinez-Corral: None. A.A. Uner: None. W. Yang: None. Y. Kim: None. V. Prevot: None. Funding R01AG080842

Phosphoenolpyruvate carboxykinase 1 (PCK1) is a key integrator of hepatic energy metabolism, but its role in hepatic stellate cells (HSCs), the main fibrogenic cells in the liver, remains unknown. We found that PCK1 is reduced in HSCs from fibrotic animals and people with fibrosis, correlating negatively with fibrosis severity. Silencing PCK1 activates human HSCs and increases fibrotic markers, whereas ectopic PCK1 expression blunts transforming growth factor β1 (TGF-β1)-induced activation. Activated HSCs show elevated glycolysis and tricarboxylic acid (TCA) cycle activity, but PCK1 overexpression reduces acetyl-coenzyme A (CoA), limiting TCA cycle intermediates and ameliorating HSC activation. In mice, HSC-specific PCK1 loss accelerates diet-induced liver fibrosis. Notably, mice lacking PCK1 in HSCs also develop spontaneous fibrosis on a normal diet. These findings show that disrupted cataplerosis from PCK1 loss enhances glycolysis and activates HSCs, promoting liver fibrosis.

Electroencephalography hyperscanning enables the study of neural synchronisation during social interaction, but its application to adult–infant dyads in naturalistic contexts remains methodologically challenging. Developmental EEG is characterised by high artefact load and age-dependent signal properties, while hyperscanning requires harmonised preprocessing across partners to ensure valid inter-brain coupling measures. We introduce HyPICE, an open-source, end-to-end pipeline for adult–infant EEG hyperscanning that integrates adaptive developmental preprocessing with established hyperscanning analysis tools. HyPICE extends the use of APICE-Py (Automated Pipeline for Infants Continuous EEG, Lorenzo et al., 2025), for data-driven artefact handling, and (ii) HyPyP (Hyperscanning Python Pipeline, Ayrolles et al., 2021), for inter-brain connectivity analysis, into an improved unified system with a standardized architecture linking infant-specific preprocessing, inter-brain connectivity analysis, with BIDS-adapted organisation. HyPICE ensures consistent processing steps across dyad members while preserving individual signal characteristics. To improve the interpretability of neural synchrony in naturalistic interactions, this workflow also incorporates automated detection of mutual gaze events, enabling behaviourally informed analyses. With HyPICE, we offer a reproducible framework for multimodal integration, empowering researchers to explore neural synchrony in the context of naturalistic early social interactions.

This study aims to provide a detailed characterization of luteinizing hormone (LH) pulsatility in male and female Sprague-Dawley and Wistar rats, utilizing a minimally invasive tail-tip blood sampling approach across various reproductive states. LH levels were measured in sequential blood samples collected from the tail tip using ultrasensitive ELISA, in both sexes and across different reproductive states. LH pulse frequency, amplitude, pattern and baseline levels were analyzed in intact and gonadectomized rats to assess strain differences and estrous cycle variation. Additionally, we evaluate LH hormonal changes in dams at day 7, 14, and 21 of gestation and lactation. LH pulse frequency and pattern were comparable between the strains in both sexes. In females, LH pulsatility varied across the estrous cycle, peaking during Metestrus and decreasing during Estrus. Gonadectomy elicited a marked increase in LH secretion in both sexes, reflected by higher amplitude and baseline levels at 6- and 10-min interval sampling, while the increase of pulse frequency was only observed at 6-min sampling. The LH surge during Proestrus exhibited substantial temporal variability, with most animals attaining peak levels between late afternoon and early night, aligning with previous observations. During gestation, LH secretion remained pulsatile, with stable frequency but increased amplitude. In lactating females, the restoration of baseline but not pulsatile LH secretion upon the removal of the sucking stimulus was unexpectedly rapid. Collectively, these results demonstrate conserved yet distinct patterns of LH secretion across sex, strain, and reproductive states, strengthening the idea that the rat is a good model for integrative neuroendocrine studies of the hypothalamic-pituitary-gonadal axis, and that the tail-tip sampling method is a reliable, humane, and minimally stressful approach for monitoring LH dynamics in rats.

Alzheimer's disease (AD) is characterized by pathological Tau protein accumulation in the brain and cerebrospinal fluid (CSF), instead of timely efflux into the blood. However, the underlying mechanisms are unclear. We show, using animal and cellular models and patient tissues, that tanycytes of the hypothalamic median eminence, which bridge the blood and CSF, are involved in Tau transport and AD pathogenesis. In mice, tanycytes take up CSF-borne Tau and release it into pituitary portal capillaries, whence it enters the systemic circulation. Blocking tanycytic vesicular transport blunts CSF-to-blood Tau efflux and potentiates Tau pathology. In AD patients, plasma-to-CSF ratios of total and p181 Tau are decreased. Tanycytes from postmortem AD patient brains display dramatically fragmented processes and significant transcriptomic alterations by single-nucleus RNA sequencing, notably in vesicular-transport-related genes, explaining this clearance deficit. The involvement of tanycytic dysfunction in human pathophysiology and evidence for a brain-to-blood tanycytic shuttle has far-reaching implications.

After more than a century since Alzheimer's disease (AD) was described and decades of research into β-amyloid and Tau proteins, mechanisms underlying pathogenic protein clearance from brain remain poorly understood. Recent research identifies tanycytes-specialized hypothalamic cells lining the third ventricle-as a previously unrecognized clearance system for brain Tau. These cells actively transport Tau from cerebrospinal fluid to blood via pituitary portal circulation but are dramatically fragmented in AD brains. Single-nucleus RNA sequencing reveals altered stress and transport gene expression in AD tanycytes, while functional studies show disrupted tanycytic transport reduces Tau efflux and exacerbates pathology. Beyond protein clearance, tanycytes maintain critical metabolic and neuroendocrine pathways influencing cognition. Their unique blood-brain interface position makes them attractive therapeutic targets. As transcriptomic evidence suggests tanycytes are hotspots for age-related changes, their dysfunction may herald "tanycytopathies" underlying multiple neurodegenerative disorders.

ABSTRACT Resmetirom is a liver‐directed, thyroid hormone receptor β (THRβ)‐selective agonist approved for treating metabolic‐associated steatohepatitis (MASH). While Resmetirom hepatocyte‐specific effects are well‐established, its impact on other hepatic cells, particularly hepatic stellate cells (HSCs), the main fibrogenic cells, remains unknown. Using animal models, immortalized cell lines, and primary murine and human HSCs, we combined pharmacological treatments with genetic manipulation of THRα and fatty acid amide hydrolase (FAAH) to examine the effects of Resmetirom. Resmetirom ameliorates MASH through actions in both hepatocytes and HSCs. The overexpression of solute carrier organic anion transporter family member 1B1(SLCO1β1) in both cell types increases the efficiency of Resmetirom. THRα expression is higher in HSCs than in hepatocytes in both human and murine cells. Resmetirom attenuates TGF‐β1‐induced HSC activation via THRα and increased FAAH expression and activity, while their inhibition prevents Resmetirom from reducing fibrotic marker expression and the elevated glycolytic activity typical of activated HSCs. These results uncover an unrecognized mechanism of action for Resmetirom, demonstrating that its antifibrotic efficacy extends beyond hepatocytes to include direct effects on HSCs via THRα and FAAH. These results may support the development of future therapeutic strategies aimed at THRα in HSC, in combination with existing approaches targeting hepatocyte THRβ.

Several neuronal populations in the hypothalamus and brainstem express thyrotropin-releasing hormone (TRH). While TRH neurons in the paraventricular nucleus (PVN) regulate the thyroid axis, the roles of other TRH-producing neurons remain largely unknown. Here we investigate the role of TRH neurons in the PVN, the dorsomedial hypothalamus (DMH), the medial preoptic area (MPA), and the rostral raphe pallidus (RPa) for metabolism in mice. Selective activation of these populations using chemogenetics in mice revealed that TRH neurons of the hypothalamus increase food intake and influence energy homeostasis in different ways. Specifically, TRH neurons in the PVN and DMH enhance brown adipose tissue activity via a polysynaptic circuit, while MPA-located neurons increase locomotor activity and maintain cold tolerance. These effects were independent of the thyroid axis, demonstrating that TRH neurons have distinct, subtype-specific ways to increase energy expenditure beyond regulating the thyroid axis in mice.