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.
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.
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.
After stroke, interhemispheric communication is often disrupted. Interhemispheric inhibition after transcranial magnetic stimulation (TMS) is thought to be mediated through the corpus callosum, but no studies have directly tested this association in people with chronic stroke. This study determined the association between TMS interhemispheric inhibition and structural integrity of the pathway connecting the bilateral motor cortices through the corpus callosum in people with chronic stroke. 33 individuals with chronic stroke [60.7 (8.3) years old; 24 male; 8.6 (6.6) years post-stroke] were enrolled. From a diffusion-weighted scan, fractional anisotropy (FA) values were extracted from the pathway between the lower limb representations of the motor cortices via the corpus callosum. TMS interhemispheric inhibition was assessed as the ipsilateral silent period (iSP) in both legs. We tested associations between FA of the corpus callosum, TMS iSP, motor impairment [Fugl Meyer Lower Extremity Assessment (FMLE)], and interlimb coordination. Fractional anisotropy values (mean [SD]: 0.35 [0.07]) were indicative of white matter damage in the corpus callosum. Ipsilateral silent periods were identified in the non-paretic (n = 31, mean [SD]: 59.9 [41.3]) and paretic TA (n = 24, mean [SD]: 60.8 [22.2]). Larger FA values were associated with shorter iSP duration in the paretic TA (R2 = 0.24, p = 0.02), better interlimb coordination (R2 = 0.19, p = 0.02), and lesser motor impairment (R2 = 0.14, p < 0.05). Results suggest that TMS interhemispheric inhibition is at least partially mediated via the corpus callosum. Preservation of corpus callosum after stroke may allow interhemispheric inhibition and motor function and coordination that more closely resembles that of individuals without stroke.
Ischemic stroke (IS) remains a devastating condition with limited neuroprotective options. This study investigated the role of the transcription factor inhibitor of DNA binding 3 (ID3) in acute IS through an integrated approach. Combining bioinformatic analysis of Gene Expression Omnibus (GEO) datasets with machine learning (ML) algorithms, we identified ID3 as a consistently downregulated key gene, and its expression level correlated with neurological severity. Functional analysis suggested ID3 modulates neuroinflammation. Furthermore, ID3 and C-type lectin domain family 4 member E (CLEC4E) showed potential as diagnostic biomarkers. Using network pharmacology, pantothenic acid (PA) was predicted as a potential ID3-targeting drug. This was preliminarily tested in an oxygen-glucose deprivation/reperfusion (OGD/R) model, where PA treatment specifically upregulated ID3, ameliorated neuronal electrophysiological dysfunction, and restored action potential amplitude. Our work provides the first integrative evidence suggesting ID3 as a pivotal protective factor in acute IS and nominates PA as a candidate for further development as a neuroprotective agent.
Two-pore domain potassium (K2P) channels control resting membrane potential of neurons and contribute to pain hypersensitivity when their expression or function is reduced. Tandem of P-domains in a Weak Inwardly rectifying K+ channel 1 (TWIK1) is broadly expressed in the nervous system, yet little is known about its regulation in dorsal root ganglion (DRG) neurons. Because components of the renin-angiotensin system (RAS) modulate sensory excitability, we investigated whether Angiotensin-II (Ang II) and its receptors, AT1R and AT2R, regulate TWIK1 expression. Using primary DRG cultures, we found that Ang II significantly increased TWIK1 mRNA and protein at 1-2 days in vitro. Quantitative immunocytochemistry revealed receptor-specific effects: TWIK1 up-regulation at 1 day was primarily AT2R-dependent, whereas AT1R contributed to a lesser extent. TWIK1 expression declined by 2 days but remained sensitive to receptor blockade. To test physiological relevance, we injected Ang II intradermally into the hindpaw of adult rats. Repeated-but not single-Ang II injections produced a modest reduction of TWIK1 in large L5 DRG neurons and in NF200-positive cutaneous terminals. This decrease was accompanied by mild mechanical hypersensitivity without changes in cold sensitivity. These in vivo effects align with preferential AT1R expression in medium and large DRG neurons and with the in vitro finding that TWIK1 down-regulation is most evident when AT1R remains active. These results identify TWIK1 as a downstream target of Ang II signaling in sensory neurons and suggest that RAS-dependent modulation of K2P channels may influence neuronal excitability and contribute to pain-related processes.
Circadian rhythms are ~24-h rhythms generated by the suprachiasmatic nucleus (SCN) in the mammalian hypothalamus. The regulation of circadian rhythms and downstream processes is highly dependent on the proper development and function of the SCN. Six3 and Six6 are homologous homeodomain transcription factors that have been shown to be required for SCN development; intriguingly, both Six3 and Six6 remain expressed in the adult SCN. To determine the role of Six3 and Six6 in the SCN after neurogenesis, we used Cre-lox to conditionally knockdown either Six3 or Six6 from cells that express neuromedin-S (NMS), a neuropeptide expressed in approximately half of SCN neurons. We found that the Nmscre allele turns on in the SCN after embryonic Day 16.5, limiting Cre-lox-mediated loss of Six3 or Six6 to the period after SCN neurogenesis. Using this approach, we hypothesized that Six3 and Six6 in NMS neurons regulate SCN circadian output and resulting reproductive function in males and females. Loss of Six6 from NMS neurons had no impact on puberty and reproduction. While loss of Six3 from NMS neurons had no effect in females, we found significantly decreased sperm motility in males, potentially through direct effects of Six3 in the testis. Loss of Six3, but not Six6, in NMS neurons resulted in shortened wheel-running periods in constant darkness, indicating a shortening of the endogenous rhythm within the SCN. Together, these data indicate a role of Six3 in determining the circadian period, suggesting differing functions of Six3 and Six6 in the adult SCN.
Diabetes plays an important role in the pathogenesis of ischemic stroke and brain recovery. We have reported the neuroprotective effect of low dose naltrexone (LDN) in type 2 diabetic (db/db) mice post-hypoxia-ischemia (HI) injury. In this study, we explored LDN mediated mechanisms of neuroprotection in diabetic mice. Adult male db/db and non-diabetic (db/+) mice underwent right common carotid artery occlusion followed by hypoxia (8% O2) for 20 min. LDN (1 mg/kg) was administered at 4, 24, and 48 h post-HI, and mice were euthanized at 72 h. Blood and brain tissue were analyzed for cytokines and growth factors by multiplex array, immunofluorescence and western blotting. LDN treatment resulted in an increased number of reactive astrocytes in the motor cortex and caudate and hippocampus of diabetic mice, which was decreased in db/+ mice, except in the CA3 hippocampal region. LDN did not show any significant change in the cytokine response between db/+ and db/db mice. However, the vascular endothelial growth factor (VEGF) levels in the plasma and brain tissue of LDN-treated db/db mice that were significantly reduced in the vehicle-treated db/db group were restored to the level of the db/+ treated group. When infarct size was categorized, LDN increased VEGF+ neurons in the motor cortex and caudate in small infarcts, and in the motor cortex of large infarcts, in db/db mice. The study suggests that acute LDN increased the number of VEGF+ neurons and prevented astrocytic cell death in db/db mice, thus enhancing neuroprotection following brain HI injury.
Fibrinogen is a blood-derived protein involved in coagulation and can make its way into the central nervous system (CNS) following breakdown of the blood-brain barrier. This molecule has been implicated in multiple sclerosis (MS), a disease marked by inflammation and demyelination in the CNS. However, the effect of this molecule has not been studied on human myelinating cells. This study examines how fibrinogen influences human oligodendrocyte (OL) lineage cells at various stages of development. Using induced pluripotent stem cell-derived (iPSC) OL precursors and human primary OLs, we examined the effects of fibrinogen on cell differentiation, viability, and myelination-related function. Here we show the differential effect of fibrinogen, based on OL-lineage stage. While fibrinogen induced aberrant differentiation of early lineage OLs, by inhibiting their maturation and inducing an astrocytic phenotype, on mature OLs fibrinogen was found to promote myelination capacity, as shown by ensheathment assays as well as on the RNA level. These effects were associated with the activation of bone morphogenetic protein (BMP) signaling, both in early and mature OLs. We further found BMP signaling enrichment in OLs to be correlated with the inflammatory activity of an MS lesion and confirmed fibrinogen deposition on OLs in situ. Unlike previous rodent studies, these findings indicate that fibrinogen has a lineage-dependent effect, where it may be inhibitory earlier in the lineage while promoting OL function in later stages. Understanding this dual role will provide insight into remyelination failure in MS and highlights the importance of timing and target in future therapeutic strategies.
Mild traumatic brain injury (mTBI) is a major public health concern worldwide and contributes to chronic, persistent neurodegenerative diseases; however, the mechanisms are not fully understood. Most studies have examined cerebral cortex, hippocampus, and thalamus brain tissue, but the impact on the cerebellum following repetitive mTBI (rmTBI) leading to secondary injury cascades and long-term pathophysiology is largely unexplored. This study investigated changes in gene expression in cerebellum tissue from an established murine model of rmTBI. The cerebellum tissue from 15 male C57BL/6J mice was analyzed using RNA sequencing technology for animals sacrificed 48 h (acute) and 90 days (chronic) following a repetitive mild impact schedule. Differentially expressed gene (DEG) analysis showed no dysregulated genes above log2 fold change at 48 h, but 360 DEGs at 90 days. At 90 days, multiple Gene Ontologies were different to controls, including disruption to mitochondria, proteosomes, ribosomes, and a reduction in vital cellular energy processes. Kyoto Encyclopedia of Genes and Genomes pathway analysis in the chronic injury group revealed that dysregulated genes were characteristic of multiple neurological diseases, including Parkinson's and Huntington's disease genetic signatures. This data demonstrates that the cerebellum and other brain regions disparate from the site of impact are more than just a bystander in chronic neurodegenerative pathologies and provides a vital link to the development of neurological disorders like Parkinson's disease from rmTBI trauma.
Purkinje cells (PCs), the principal output neurons of the cerebellar cortex, are classically implicated in motor coordination via inhibitory projections to the deep cerebellar nuclei (DCN). Emerging evidence suggests their influence extends to seizure susceptibility, yet the underlying mechanisms remain unclear. Here, we investigated the functional role of PCs in locomotion and seizure-like activity in zebrafish larvae. Using the UAS/Gal4 system, we selectively expressed light-sensitive ion channels in PCs: Channelrhodopsin-2 (ChR2) to activate, and Anion ChannelRhodopsin-2 (ACR2) to inhibit neuronal activity. Behavioral assays at 5 days post-fertilization assessed locomotor output, while local field potential recordings monitored seizure-like events under baseline conditions and following administration of a proconvulsant agent. Optogenetic activation of PCs transiently increased locomotion and significantly reduced the duration and power of seizure-like events under hyperexcitable conditions, without affecting baseline activity. Conversely, inhibition of PCs was sufficient to induce seizure-like activity even in the absence of convulsant stimuli. These results reveal a dual role for PCs: they suppress pathological hyperexcitability during proconvulsant states, yet their inhibition can trigger seizures. This work highlights the cerebellum as a critical regulator of excitation-inhibition balance, linking motor control and seizure susceptibility, and suggests that cerebellar dysfunction may contribute to both motor and epileptic phenotypes observed in neurodegenerative disorders.
Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by cognitive decline, memory impairment, and behavioral alterations. The pathogenesis of AD involves the accumulation of amyloid-beta (Aβ) plaques and the hyperphosphorylated tau proteins, which disrupt neuronal function and trigger neuroinflammation. This study explores the therapeutic potential of epigallocatechin gallate (EGCG) and punicalagin (PU) in mitigating Aβ-induced toxicity using an adult zebrafish model of AD. Our results demonstrate that the EGCG + PU combination significantly reduces Aβ accumulation, protects against cellular damage, suppresses acetylcholinesterase (AChE) activity, and normalizes the expression of amyloidogenic and AD-related genes. Additionally, EGCG + PU treatment alleviates neuroinflammation by suppressing glial activation, including reductions in L-plastin and proinflammatory cytokine expression, while promoting neuronal recovery through mechanisms of neurogenesis and neuroprotection. Notably, the combination treatment restored neuronal density and improved behavioral outcomes by alleviating anxiety- and aggression-like behaviors associated with Aβ toxicity. These results underscore the synergistic neuroprotective effects of EGCG + PU, highlighting their potential as a novel therapeutic approach for mitigating the pathological, behavioral, and inflammatory aspects of AD.
Chronic trigeminal neuropathic pain is caused by a lesion, damage, or trauma to the trigeminal sensory system. The pain affects female individuals with higher incidence and greater severity compared with males. Despite a strong sex bias in this clinical condition, the majority of preclinical experimental studies of trigeminal neuropathic pain have been conducted in males. This study investigated sex differences in the number of ΔFosB and FosB immunoreactive cells, as markers of neuronal adaptation following infraorbital nerve chronic constriction injury (ION-CCI). Sex differences in ΔFosB and FosB expression were identified in infra-orbital recipient regions of laminae I-II of the medullary dorsal horn during the post-injury period. Three phases of altered expression were identified following ION-CCI: (1) an early phase 2 days after injury, (2) a transitional phase (7-14 days), and (3) a late phase (28+ days). Nerve-injured female rats had consistently lower levels of ΔFosB immunoreactive cells when compared with males and showed increased FosB expression during the early phase. In contrast, in males, the number of ΔFosB immunoreactive cells decreased significantly from the early phase to the transitional phase post-injury. However, by the late phase, ΔFosB expression in the superficial laminae of the medullary dorsal horn was significantly higher than in females. These data suggest that cellular adaptation in neurons in laminae I-II of the medullary dorsal horn in males is much greater than that in females, revealing one location at which the sex differences seen in the incidence and severity of trigeminal neuropathic pain might be mediated.
Recent evidence has shown that bone marrow mesenchymal stem cells (BMSCs) have multiple biological applications and play an important role in improving cognitive dysfunction. However, it is still unclear whether BMSCs play a role in cognitive impairment induced by chronic pain. This study aimed to evaluate the therapeutic effect of BMSCs on neuropathic pain-induced cognitive dysfunction and explore its potential mechanisms. A mouse chronic constriction injury (CCI) model was established, and the new object recognition task and fear conditioning were used to detect cognitive function; the expression of CXCL12/CXCR4 in blood and hippocampus was detected. After intravenous injection of BMSCs, changes in cognitive function and expression of the CXCL12/CXCR4 pathway, dentate gyrus neurogenesis, and excitability of hippocampal neurons were detected. In addition, induction of cognitive impairment in normal mice by CXCL12 recombinant protein was used to clarify whether the CXCL12/CXCR4 pathway mediates the cognitive function improvement effect of BMSCs. Our results found CCI mice showed significant cognitive impairment 21 days after surgery, with significantly increased expression of CXCL12/CXCR4 in blood and hippocampus. Intravenous injection of BMSCs significantly improved cognitive function, inhibited expression of CXCL12/CXCR4 in blood and hippocampus, promoted neurogenesis in dentate gyrus of CCI mice, and increased expression of BDNF and c-Fos in the hippocampus. In addition, BMSCs alleviate cognitive impairment induced by intravenous injection of CXCL12 recombinant protein in mice. In summary, BMSCs improve chronic neuropathic pain-induced cognitive dysfunction through peripheral blood CXCL12/CXCR4, and BMSCs may develop into therapeutic targets for chronic pain induced cognitive impairment.
