The majority of animal models of Parkinson's disease (PD) focus on motor symptoms that are induced by unilateral injections of such neurotoxins as 6-hydroxydopamine (6-OHDA) in nigrostriatal dopaminergic pathways. However, motor changes that are induced by unilateral 6-OHDA injections may interfere with the identification of cognitive and affective dysfunctions induced by dopaminergic neurodegeneration. To select an appropriate method for studying nonmotor symptoms of PD and potential neuroprotective treatments, the present study compared behavioral effects of bilateral 6-OHDA infusions directly in the substantia nigra pars compacta (SNpc) or striatum in rats. A battery of behavioral tests, including affective and cognitive tasks, was performed for 22 days after 6-OHDA nigrostriatal lesions. The massive degeneration of tyrosine hydroxylase-immunoreactive neurons was observed in the SNpc, striatum, and ventral tegmental area with 6-OHDA infusions in either the SNpc or striatum. Concerning functional outcomes, 6-OHDA infusions in the striatum decreased general exploratory activity 7 days after the lesion. Rats that received 6-OHDA in the SNpc exhibited cognitive impairments and despair-like behavior. A decrease in the number of newborn neurons was found in the hippocampus in rats that received 6-OHDA in the striatum, indicating a alteration of neuron maturation. 6-OHDA infusions in both the SNpc and striatum impacted the maturation of newborn hippocampal neurons. These results indicate that bilateral injections of 6-OHDA in the SNpc might be useful for studying nonmotor symptoms of PD.

Oligodendrocytes (OLs) are essential for central nervous system (CNS) function through their role in axon myelination, and their dysfunction is implicated in a range of neurological disorders. Despite this, in vitro modeling of human OL biology remains limited by the scarcity of primary human OLs. Furthermore, while induced pluripotent stem cells (iPSCs) offer a promising source of human OLs, current differentiation protocols remain complex, inefficient, and time-consuming. Here, we present an optimized protocol to generate OLs from iPSCs (iOLs) using defined soluble factors supplemented in the culture media. Within 28 days, cultures yielded an average of 85% O4[+] iOLs, and by Day 38, approximately 70% expressed MBP, a key marker of mature OLs. Bulk RNA-seq analysis confirmed a stepwise transcriptional progression consistent with OL lineage identity, with upregulation of key OL-specific transcripts and gene expression profiles. Comparative transcriptomic analyses further revealed increased expression of gene networks associated with myelination, extracellular matrix remodeling, and gliogenesis when iOLs were cultured on aligned nanofiber scaffolds. Importantly, iOLs formed compact myelin sheaths around axons and showed enhanced maturation in a three-dimensional (3D) environment, highlighting the importance of spatial and matrix-derived cues in OL development. This study establishes a cost- and time-efficient approach for generating functional OLs from iPSCs, with broad applicability for disease modeling, drug screening, and the development of regenerative therapies.

This narrative review examines the essential roles of heparan sulfate proteoglycans (HSPGs) in brain development, synaptic function, axonal guidance, synapse formation and stabilization, and the establishment of correctly interconnected neural networks. Distinct HSPG profiles help shape precise neural circuits, whereas HSPG dysregulation is associated with impaired neurodevelopmental processes, cognitive decline, and pathological changes in brain tissues. These findings emphasize the importance of HSPGs in normal brain function and in disease-associated tissue dysfunction. HSPGs are a diverse group of proteins with critical roles in the CNS and PNS, including synaptic function, neurodevelopment, neurodegeneration, cell migration, and regulation of neuroprogenitor stem cell niches in the subventricular ependymal zone and subgranular dentate gyrus. Together, the diverse functions of HSPGs place them as master regulators of tissue form and function in health and disease.

Mild traumatic brain injury (mTBI) is associated with persistent physical, cognitive, and emotional symptoms, yet the functional brain changes that accompany recovery remain incompletely understood. This longitudinal study investigated brain entropy (BEN), a resting-state measure of irregularity or complexity of spontaneous BOLD activity derived from resting-state functional magnetic resonance imaging (rs-fMRI), during the first year following mTBI. Data of rs-fMRI were acquired from 48 patients with mTBI at the acute (< 14 days), 6-month, and 12-month post-injury visits, and 34 healthy controls (HCs). BEN was quantified using sample entropy. Patients with mTBI also underwent behavioral assessments evaluating quality of life and cognitive function. Behavioral assessments demonstrated progressive improvements in patient-reported quality of life and objective cognitive performance. Cross-sectional analyses revealed dynamic, time-dependent alterations in BEN. Compared with HCs, patients with mTBI exhibited higher BEN in precuneus, temporal, occipital, and sensorimotor regions during the acute and 6-month stages, whereas lower BEN was observed in sensorimotor, occipital, and frontoparietal regions at the 12-month follow-up. Longitudinal analyses demonstrated progressive regional reductions in BEN over time. Several associations between longitudinal changes in regional BEN and cognitive performance were nominally significant, particularly in the precuneus, but none survived multiple comparison corrections. These findings indicate that mTBI recovery is accompanied by dynamic, regionally specific changes in resting state BOLD irregularity. BEN may therefore provide a promising imaging biomarker for tracking the evolving neural dynamics underlying recovery following mTBI.

Chronic pain in later life may be accompanied by alterations in brain structure and cognition, but whether pain extent and central sensitization symptoms identify distinct brain-behavior patterns remains unclear. We examined associations of pain extent and central sensitization symptoms, assessed using the 9-item Central Sensitization Inventory (CSI-9), with regional gray matter volume and cognitive function in community-dwelling older adults. This cross-sectional study included 272 participants with chronic pain from the Bunkyo Health Study. Participants were classified as having single-site or multisite pain and by CSI-9 score as having lower or higher scores, with ≥ 12 defining the higher group. Regional gray matter volume was quantified using 0.3-Tesla magnetic resonance imaging, and cognition was assessed using the Trail Making Test Part B (TMT-B), processing speed, and global and domain-specific measures. Pain extent and CSI-9 group interacted for TMT-B performance, with the longest completion time in participants with single-site pain and a higher CSI-9 score. No other cognitive outcome remained significant after correction for multiple testing. In categorical analyses, the higher CSI-9 group had smaller volumes in the right middle frontal gyrus, bilateral anterior cingulate cortex, right insula, right hippocampus, and bilateral amygdala, whereas pain extent and the interaction were not associated with regional volume. In a contextual comparison, only the single-site/higher CSI-9 group showed slower TMT-B performance than participants with no current pain. Pain extent and central sensitization symptoms may represent partly distinct dimensions of chronic pain, although the small single-site/higher CSI-9 group and attenuation in several sensitivity analyses warrant caution.

The Endoterpenoid System (ETS) is a proposed new membrane-based framework that ensembles classical endocannabinoid signaling (ECS) with ectopically expressed olfactory GPCRs, ion channels, and microbially derived terpenoids. Integrated with this model is the proposed endoterpenoidome (eTBome) machine: a chemically diverse pool of endogenous cannabinoids, dietary terpenoids, and microbial metabolites whose lipophilicity drives partitioning into cholesterol-rich lipid rafts. Within these nanoscale microdomains, ETS components undergo co-localization and co-expression, enabling receptor heteromerization and β-arrestin-scaffolded signalosomes that facilitate dynamic crosstalk and emergent responses such as bistable apoptotic switches and context specific modulation of Gᵢ/o, Gₛ/olf, and Gq pathways. We detail molecular mechanisms underpinning ETS behavior, including lipid mediated allostery, scaffold protein recruitment, and lateral diffusion effects, and highlight the gut microbiota as pivotal architects of the eTBome through terpene synthase-driven production of bioactive ligands. Germ free and antibiotic treated animal models underscore the dependence of ETS ligand pools and receptor distributions on microbial colonization. This article proposes key avenues for experimental validation, including high resolution structural studies of CB-OR heteromers, quantitative lipidomic mapping of eTBome distributions, live cell super resolution imaging of receptor nanoclusters, and gnotobiotic manipulations of microbial terpene synthesis. By introducing them as proposals to the scientific community and by integrating ECS/eCBome biology with olfactory receptor (OR) and microbial metabolite research, the ETS/eTBome concept offers a cohesive hypothesis for lipid-driven GPCR crosstalk and indicated non-standard targets for therapeutic modulation in cancer, neuroinflammation, and metabolic disorders.

To obtain rewards, animals must select actions while facing threats, often under competing appetitive and defensive drives and with uncertainty about harm. While neural circuits controlling isolated threats or rewards are well characterized, it remains unclear which specific cortical and subcortical nodes are causally necessary to organize behavior during motivational conflict. Here, we used the step-down avoidance-mediated conflict (SDAmC) task in adult male rats, which quantifies avoidance, risk assessment, and reward approach within the same session. We performed pharmacological inactivation across eight candidate structures implicated in valence and action selection: prelimbic (PL) and infralimbic (IL) cortices, lateral orbitofrontal cortex (lOFC), anterior (aIC) and posterior (pIC) insular cortices, lateral habenula (LHb), basolateral amygdala (BLA), and nucleus accumbens (NAc). Inactivation revealed a precise anatomical dissociation within this network. Silencing PL or pIC facilitated approach behavior during conflict, but with dissociable effects on risk assessment. In contrast, BLA inactivation induced a broader behavioral disinhibition evident even in non-conflict conditions, whereas NAc inactivation disrupted the temporal organization of approach, yielding a fragmented behavioral phenotype. Notably, inactivation of IL, lOFC, aIC, and LHb did not alter conflict resolution in this paradigm. Together, these findings identify a selective cortico-limbic network in which PL and pIC are necessary for limiting approach under conflict, BLA contributes to avoidance expression across motivational states, and NAc contributes to approach-related behavioral organization under conflict, constraining the set of brain regions that are necessary to organize behavior when reward seeking competes with threat.

Epilepsy is one of the most common neurological disorders worldwide, affecting around 1% of the population. The epilepsies represent a diverse group of conditions, ranging from acquired forms resulting from neurological insults to common multifactorial epilepsies and rare, often monogenic epilepsies caused by highly penetrant genetic variants. The genetic epilepsies demonstrate frequent comorbidity with a range of neurodevelopmental and psychiatric disorders, and epileptic seizures are also a common feature of neurodevelopmental disorders such as Fragile X syndrome and Rett syndrome. Astrocytes, the most numerous glial cells in the central nervous system, have emerged as crucial players in the pathophysiology of acquired epilepsies. Whilst the contribution of astrocytes to acquired epilepsy has been widely reviewed, astrocyte dysfunction in rare genetic epilepsies or neurodevelopmental disorders has been neglected, despite the fact that the genes implicated are expressed in astrocytes, albeit to a lesser extent than in neurons. Additionally, affected individuals with rare genetic epilepsies are more likely to exhibit drug-resistant seizures, highlighting the need to identify novel therapeutic targets. In this paper, we review the existing literature on astrocyte dysfunction in genetic epilepsy syndromes and neurodevelopmental disorders with seizures. We have identified several key studies that highlight alterations in crucial astrocyte functions including calcium signaling and ion homeostasis. Our review highlights the need for further research to establish the contribution of astrocyte dysfunction to neuronal health and seizure activity in rare genetic epilepsies.

This narrative review highlights the functional attributes of keratan sulfate (KS), a glycosaminoglycan integral to structural support, hydration, and diverse tissue functions. KS has roles in cell signaling and regulates cellular adhesion, proliferation, and differentiation. The electroconductive properties of KS stabilize ion fluxes and electrochemical gradients at the cell surface essential for membrane polarization that directs neuronal activation and neurotransmission. KS interacts with a diverse collection of kinases, growth factors, morphogens, and neuro-modulatory proteins, facilitating axonal guidance and correctly inter-connected neural networks essential for control of tissue function. The ability of KS to capture and transport protons assists in neuronal signaling and provides an ultrasensitive system that allows neurons to participate in neurosensory processes and contribute to neurosensory perception. The roles of some KS-proteoglycans are highlighted and encourage further studies in innovative areas of sensory perception and tissue function.

Parkinson's disease (PD) is a neurodegenerative disorder, clinically characterized by motor- and non-motor symptoms. Misfolding of alpha-synuclein into pathological substrates, followed by neuronal spread, seems to be a key event in the spatiotemporal course of the disease. Previously, few studies have yielded insight into altered cell numbers in post-mortem brains from PD patients. Beside nigral neuronal loss, no quantitative studies have reported significant loss of neurons in PD brains, suggesting that the neuropathological progress in PD have minor impact on neuronal survival outside of the substantia nigra. Reports further show impairment of intra- and inter-cortical white matter tracts, observations that signify a role of oligodendrocytes in PD pathogenesis. Hence, our objective of the present study was to investigate oligodendroglia morphology (total numbers and volumes) in the neocortex of post-mortem brains from PD patients and control subjects using stereological methods. Our findings show an explicit 34% reduction in the total number of oligodendrocytes in the frontal cortex of PD patients, with no such changes in the other cortical lobes. Furthermore, the results displayed no group differences in the mean volume of oligodendrocytes in the entire neocortex or its subregions. The reduction in frontal oligodendrocytes may be related to the demonstrated impairment of white matter tracts, however, further studies are needed to clarify the mechanistic and functional relevance of oligodendropathy in PD.

Neuroinflammation, driven by microglia activation and the production of pro-inflammatory cytokines, has been implicated in several neurological diseases and neuropathic pain. MicroRNAs (miRNAs) have emerged as important regulators of neuroinflammatory processes. Prior studies identified elevated levels of circulating miR-19a and miR-19b in individuals living with chronic pain following spinal cord injury (SCI). In this study, we wanted to determine whether miR-19a and miR-19b have a direct effect on microglia activation, specifically pro-inflammatory activation, associated with neuroinflammation. Microglia were activated by inflammatory stimuli in the presence of miR-19a or miR-19b mimics, and assessed for the expression of cytokines, chemokines, and effector molecules. The results show that miR-19a or miR-19b mimics increased the expression of pro-inflammatory cytokines, chemokines, and effector molecules in microglia. The results also showed decreased expression of suppressor of cytokine signaling (SOCS) proteins, namely SOCS1 and SOCS3, in activated microglia with miR-19a and miR-19b mimics. Additionally, enhanced signaling through the NFκB and Jak pathways was observed with increased NFkB-p65 and JAK1 phosphorylation in the presence of miR-19a and miR-19b mimics. Further results show that miR-19a and miR-19b inhibitors reversed these effects on activated microglia. Overall, our results demonstrate that miR-19a or miR-19b increased the expression of pro-inflammatory cytokines, chemokines, and effector molecules in activated microglia. These results indicate that miR-19a and miR-19b can enhance microglia activation and associated inflammatory responses, which may have implications for conditions associated with neuroinflammation.

Stromal nerves regulate the sensory functions of the cornea, which can be disrupted by surgical, traumatic, or chemical injuries. Corneal Schwann cells (cSCs) ensheath axons to provide trophic support, but their role in axonal regeneration is still unexplored. We utilized the proteolipid protein 1-enhanced green fluorescent protein (Plp1-eGFP) reporter mice to investigate cSCs in two models of corneal nerve injury: the corneal micropocket injury (CMI) model, which causes focal stromal axonal severance, and acute exposure to nitrogen mustard (NM), which results in blunt damage across the entire cornea and limbal tissue. After CMI, the cSC network declined rapidly over 7 days post-injury (dpi) but recovered to levels of uninjured controls by 14 dpi with sprouting at both the injury and collateral areas. Axons remained significantly lower than cSCs, compromising mechanosensory functions. The NM injury led to a sustained cSC and axonal deficit with persistent mechanosensory loss through 14 dpi. Previously, we identified Dickkopf-related protein 1 (DKK1) as a novel candidate gene expressed in cSCs. In this study, we developed a micellar formulation RM4404 incorporating a small-molecule DKK1 inhibitor for topical application and tested the therapeutic potential of this drug in both injury models. Application of RM4404 during the cSC regenerative phase (7-14 dpi) enhanced cSC repair and significantly improved axonal regeneration with restoration of mechanosensory function in both injury paradigms. These findings identify a promising DKK1-targeted therapy that promotes cSC repair, enhances corneal nerve regeneration, and restores sensory function in models of corneal injury.

Although functional connectomics typically relies on resting-state fMRI, its analytical methods have been applied to task fMRI data in the investigation of broader involvements of brain regions even if inactive during a specific task. The purpose of this study is to assess the feasibility of inferring a true resting-state connectivity from task-fMRI data and to investigate the impact of connectomic-based analysis on behavioral trait studies. To this purpose, subjects underwent two visual fMRI tasks. The Blood-Oxygen-Level-Dependent (BOLD) time-series were processed to get both a "task" condition and a "pseudo-resting" condition applying different task regression setups to derive connectomes. Stimulus-classification experiments were conducted to compare "task" and "pseudo-resting" connectomes. Additionally, the influence of task regression was assessed through a classification experiment comparing children with Developmental Dyslexia (DD) and Typical Readers (TR). While task regression successfully removes task-related content from fMRI signals, stimulus information could still be inferred from connectomes, regardless of the preprocessing method used. Furthermore, a Support Vector Machine (SVM) experiment effectively discriminates between DD and TR in both "task" and "pseudo-resting" conditions. The study explored the impact of preprocessing in task fMRI experiments analyzed with connectomics. The ability to classify the stimuli in "pseudo-resting" conditions suggests that connectomes retain task-related signals even after task regression. Discriminative connections vary across tasks, affecting how classifiers differentiate between DD and TR. Despite these task-related differences, preprocessing had no effect on the inference of classification rules, indicating that key features are similarly evaluated in both tasks.