NG2/CSPG4 and progranulin in the posttraumatic glial scar

Chitosan/PLGA-based tissue engineered nerve grafts with SKP-SC-EVs enhance sciatic nerve regeneration in dogs through miR-30b-5p-mediated regulation of axon growth

Extracellular vesicles from skin-derived precursor Schwann cells (SKP-SC-EVs) promote neurite outgrowth in culture and enhance peripheral nerve regeneration in rats. This study aimed at expanding the application of SKP-SC-EVs in nerve grafting by creating a chitosan/PLGA-based, SKP-SC-EVs-containing tissue engineered nerve graft (TENG) to bridge a 40-mm long sciatic nerve defect in dogs. SKP-SC-EVs contained in TENGs significantly accelerated the recovery of hind limb motor and electrophysiological functions, supported the outgrowth and myelination of regenerated axons, and alleviated the denervation-induced atrophy of target muscles in dogs. To clarify the underlying molecular mechanism, we observed that SKP-SC-EVs were rich in a variety of miRNAs linked to the axon growth of neurons, and miR-30b-5p was the most important among others. We further noted that miR-30b-5p contained within SKP-SC-EVs exerted nerve regeneration-promoting effects by targeting the Sin3a/HDAC complex and activating the phosphorylation of ERK, STAT3 or CREB. Our findings suggested that SKP-SC-EVs-incorporating TENGs represent a novel type of bioactive material with potential application for peripheral nerve repair in the clinic.

Insertional effect following electrode implantation: an underreported but important phenomenon

Deep brain stimulation has revolutionized the treatment of movement disorders and is gaining momentum in the treatment of several other neuropsychiatric disorders. In almost all applications of this therapy, the insertion of electrodes into the target has been shown to induce some degree of clinical improvement prior to stimulation onset. Disregarding this phenomenon, commonly referred to as 'insertional effect', can lead to biased results in clinical trials, as patients receiving sham stimulation may still experience some degree of symptom amelioration. Similar to the clinical scenario, an improvement in behavioural performance following electrode implantation has also been reported in preclinical models. From a neurohistopathologic perspective, the insertion of electrodes into the brain causes an initial trauma and inflammatory response, the activation of astrocytes, a focal release of gliotransmitters, the hyperexcitability of neurons in the vicinity of the implants, as well as neuroplastic and circuitry changes at a distance from the target. Taken together, it would appear that electrode insertion is not an inert process, but rather triggers a cascade of biological processes, and, as such, should be considered alongside the active delivery of stimulation as an active part of the deep brain stimulation therapy.

Current state of neuroprotective therapy using antibiotics in human traumatic brain injury and animal models

TBI is a leading cause of death and disability in young people and older adults worldwide. There is no gold standard treatment for TBI besides surgical interventions and symptomatic relief. Post-injury infections, such as lower respiratory tract and surgical site infections or meningitis are frequent complications following TBI. Whether the use of preventive and/or symptomatic antibiotic therapy improves patient mortality and outcome is an ongoing matter of debate. In contrast, results from animal models of TBI suggest translational perspectives and support the hypothesis that antibiotics, independent of their anti-microbial activity, alleviate secondary injury and improve neurological outcomes. These beneficial effects were largely attributed to the inhibition of neuroinflammation and neuronal cell death. In this review, we briefly outline current treatment options, including antibiotic therapy, for patients with TBI. We then summarize the therapeutic effects of the most commonly tested antibiotics in TBI animal models, highlight studies identifying molecular targets of antibiotics, and discuss similarities and differences in their mechanistic modes of action.

Inhibition of CD44 suppresses the formation of fibrotic scar after spinal cord injury via the JAK2/STAT3 signaling pathway

Fibrotic scar is one of the main impediments to axon regeneration following spinal cord injury (SCI). In this study, we found that CD44 was upregulated during the formation of fibrotic scar, and blocking CD44 by IM7 caused downregulation of fibrosis-related extracellular matrix proteins at both 2 and 12 weeks post-spinal cord injury. More Biotinylated dextran amine (BDA)-traced corticospinal tract axons crossed the scar area and extended into the distal region after IM7 administration. A recovery of motor and sensory function was observed based on Basso Mouse Scale (BMS) scores and tail-flick test. In vitro experiments revealed that inhibiting CD44 and JAK2/STAT3 signaling pathway decreased the proliferation, differentiation, and migration of fibroblasts induced by the inflammatory supernatant. Collectively, these findings highlight the critical role of CD44 and its downstream JAK2/STAT3 signaling pathway in fibrotic scar formation, suggesting a potential therapeutic target for SCI.

In vitro assessment of protamine toxicity with neural cells, its therapeutic potential to counter chondroitin sulfate mediated neuron inhibition, and its effects on reactive astrocytes

Multiple therapies have been studied to ameliorate the neuroinhibitory cues present after traumatic injury to the central nervous system. Two previous in vitro studies have demonstrated the efficacy of the FDA-approved cardiovascular therapeutic, protamine (PRM), to overcome neuroinhibitory cues presented by chondroitin sulfates; however, the effect of a wide range of PRM concentrations on neuronal and glial cells has not been evaluated. In this study, we investigate the therapeutic efficacy of PRM with primary cortical neurons, hippocampal neurons, mixed glial cultures, and astrocyte cultures. We show the threshold for PRM toxicity to be at or above 10 μg/ml depending on the cell population, that 10 μg/ml PRM enables neurons to overcome the inhibitory cues presented by chondroitin sulfate type A, and that soluble PRM allows neurons to more effectively overcome inhibition compared to a PRM coating. We also assessed changes in gene expression of reactive astrocytes with soluble PRM and determined that PRM does not increase their neurotoxic phenotype and that PRM may reduce brevican production and serpin transcription in cortical and spinal cord astrocytes. This is the first study to thoroughly assess the toxicity threshold of PRM with neural cells and study astrocyte response after acute exposure to PRM in vitro.

Corticospinal tract: a new hope for the treatment of post-stroke spasticity

Stroke is the third leading cause of death and disability worldwide. Post-stroke spasticity (PSS) is the most common complication of stroke but represents only one of the many manifestations of upper motor neuron syndrome. As an upper motor neuron, the corticospinal tract (CST) is the only direct descending motor pathway that innervates the spinal motor neurons and is closely related to the recovery of limb function in patients with PSS. Therefore, promoting axonal remodeling in the CST may help identify new therapeutic strategies for PSS. In this review, we outline the pathological mechanisms of PSS, specifically their relationship with CST, and therapeutic strategies for axonal regeneration of the CST after stroke. We found it to be closely associated with astroglial scarring produced by astrocyte activation and its secretion of neurotrophic factors, mainly after the onset of cerebral ischemia. We hope that this review offers insight into the relationship between CST and PSS and provides a basis for further studies.

Nanoarchitectonics of cellulose nanocrystal conjugated with a tetrasaccharide-glycoprobe for targeting oligodendrocyte precursor cells

Demyelination is a serious complication of neurological disorders, which can be reversed by oligodendrocyte precursor cell (OPC) as the available source of myelination. Chondroitin sulfate (CS) plays key roles in neurological disorders, which still attracted less attention on how CS modulates the fate of OPCs. Nanoparticle coupled with glycoprobe is a potential strategy for investigating the carbohydrate-protein interaction. However, there is lack of CS-based glycoprobe with enough chain length that interact with protein effectively. Herein, we designed a responsive delivery system, in which CS was the target molecule, and cellulose nanocrystal (CNC) was the penetrative nanocarrier. A coumarin derivative (B) was conjugated at the reducing end of an unanimal-sourced chondroitin tetrasaccharide (4mer). This glycoprobe (4B) was grafted to the surface of a rod-like nanocarrier, which had a crystalline core and a poly(ethylene glycol) shell. This glycosylated nanoparticle (N4B-P) displayed a uniform size, improved water-solubility, and responsive release of glycoprobe. N4B-P displayed strong green fluorescence and good cell-compatibility, which imaged well the neural cells including astrocytes and OPCs. Interestingly, both of glycoprobe and N4B-P were internalized selectively by OPCs when they were incubated in astrocytes/OPCs mixtures. This rod-like nanoparticle would be a potential probe for studying carbohydrate-protein interaction in OPCs.

New role of astrocytes in neuroprotective mechanisms after ischemic stroke

Astrocytes are the most abundant cell subtypes in the central nervous system. Previous studies believed that astrocytes are supporting cells in the brain, which only provide nutrients for neurons. However, recent studies have found that astrocytes have more crucial and complex functions in the brain, such as neurogenesis, phagocytosis, and ischemic tolerance. After an ischemic stroke, the activated astrocytes can exert neuroprotective or neurotoxic effects through a variety of pathways. In this review, we will discuss the neuroprotective mechanisms of astrocytes in cerebral ischemia, and mainly focus on reactive astrocytosis or glial scar, neurogenesis, phagocytosis, and cerebral ischemic tolerance, for providing new strategies for the clinical treatment of stroke.

Early posttraumatic CSF1R inhibition via PLX3397 leads to time- and sex-dependent effects on inflammation and neuronal maintenance after traumatic brain injury in mice

BACKGROUND

There is a need for early therapeutic interventions after traumatic brain injury (TBI) to prevent neurodegeneration. Microglia/macrophage (M/M) depletion and repopulation after treatment with colony stimulating factor 1 receptor (CSF1R) inhibitors reduces neurodegeneration. The present study investigates short- and long-term consequences after CSF1R inhibition during the early phase after TBI.

METHODS

Sex-matched mice were subjected to TBI and CSF1R inhibition by PLX3397 for 5 days and sacrificed at 5 or 30 days post injury (dpi). Neurological deficits were monitored and brain tissues were examined for histo- and molecular pathological markers. RNAseq was performed with 30 dpi TBI samples.

RESULTS

At 5 dpi, CSF1R inhibition attenuated the TBI-induced perilesional M/M increase and associated gene expressions by up to 50%. M/M attenuation did not affect structural brain damage at this time-point, impaired hematoma clearance, and had no effect on IL-1β expression. At 30 dpi, following drug discontinuation at 5 dpi and M/M repopulation, CSF1R inhibition attenuated brain tissue loss regardless of sex, as well as hippocampal atrophy and thalamic neuronal loss in male mice. Selected gene markers of brain inflammation and apoptosis were reduced in males but increased in females after early CSF1R inhibition as compared to corresponding TBI vehicle groups. Neurological outcome in behaving mice was almost not affected. RNAseq and gene set enrichment analysis (GSEA) of injured brains at 30 dpi revealed more genes associated with dendritic spines and synapse function after early CSF1R inhibition as compared to vehicle, suggesting improved neuronal maintenance and recovery. In TBI vehicle mice, GSEA showed high oxidative phosphorylation, oxidoreductase activity and ribosomal biogenesis suggesting oxidative stress and increased abundance of metabolically highly active cells. More genes associated with immune processes and phagocytosis in PLX3397 treated females vs males, suggesting sex-specific differences in response to early CSF1R inhibition after TBI.

CONCLUSIONS

M/M attenuation after CSF1R inhibition via PLX3397 during the early phase of TBI reduces long-term brain tissue loss, improves neuronal maintenance and fosters synapse recovery. Overall effects were not sex-specific but there is evidence that male mice benefit more than female mice.

Injectable and reactive oxygen species-scavenging gelatin hydrogel promotes neural repair in experimental traumatic brain injury

Oxidative stress caused by the overexpression of reactive oxygen species (ROS) plays an important role in the pathogenesis of traumatic brain injury (TBI). Accumulation of ROS can lead to cell death, neurodegeneration, and neurological deficit. Therefore, the design and application of functional materials with ROS scavenging ability is of great significance for neural repair. Herein, an injectable and antioxidant hydrogel was developed for TBI treatment based on the Schiff base reaction of gallic acid-conjugated gelatin (GGA) and oxidized dextran (Odex). The resulting GGA/Odex hydrogel could effectively scavenge DPPH and ABTS radicals, as well as protect cells from the oxidative damage in vitro. Moreover, GGA/Odex hydrogel possessed well biocompatible features. In a moderate TBI mouse model, in situ implantation of GGA6Odex hydrogel efficiently facilitated neurogenesis and promoted the motor, learning and memory abilities. Also, this composite hydrogel suppressed oxidative stress and inflammation via the activation of Nrf2/HO-1 pathway and the regulating of inflammatory factors secretion and macrophage/microglia polarization. Therefore, this injectable and ROS-scavenging GGA6Odex hydrogel is a promising biomaterial for tissue regenerative medicine, including TBI and other tissue repair relevant to raised ROS circumstance.

Dental Pulp-Derived Stem Cells Preserve Astrocyte Health During Induced Gliosis by Modulating Mitochondrial Activity and Functions

Astrocytes have been implicated in the onset and complication of various central nervous system (CNS) injuries and disorders. Uncontrolled astrogliosis (gliosis), while a necessary process for recovery after CNS trauma, also causes impairments in CNS performance and functions. The ability to preserve astrocyte health and better regulate the gliosis process could play a major role in controlling damage in the aftermath of acute insults and during chronic dysfunction. Here in, we demonstrate the ability of dental pulp-derived stem cells (DPSCs) in protecting the health of astrocytes during induced gliosis. First of all, we have characterized the expression of genes in primary astrocytes that are relevant to the pathological conditions of CNS by inducing gliosis. Subsequently, we found that astrocytes co-cultured with DPSCs reduced ROS production, NRF2 and GCLM expressions, mitochondrial membrane potential, and mitochondrial functions compared to the astrocytes that were not co-cultured with DPSCs in gliosis condition. In addition, hyperactive autophagy was also decreased in astrocytes that were co-cultured with DPSCs compared to the astrocytes that were not co-cultured with DPSCs during gliosis. This reversal and mitigation of gliosis in astrocytes were partly due to induction of neurogenesis in DPSCs through enhanced expressions of the neuronal genes like GFAP, NeuN, and Synapsin in DPSCs and by secretion of higher amounts of neurotropic factors, such as BDNF, GDNF, and TIMP-2. Protein-Protein docking analysis suggested that BDNF and GDNF can bind with CSPG4 and block the downstream signaling. Together these findings demonstrate novel functions of DPSCs to preserve astrocyte health during gliosis.

Phosphatidylethanolamine Deficiency and Triglyceride Overload in Perilesional Cortex Contribute to Non-Goal-Directed Hyperactivity after Traumatic Brain Injury in Mice

Traumatic brain injury (TBI) is often complicated by long-lasting disabilities, including headache, fatigue, insomnia, hyperactivity, and cognitive deficits. In a previous study in mice, we showed that persistent non-goal-directed hyperactivity is a characteristic post-TBI behavior that was associated with low levels of endocannabinoids in the perilesional cortex. We now analyzed lipidome patterns in the brain and plasma in TBI versus sham mice in association with key behavioral parameters and endocannabinoids. Lipidome profiles in the plasma and subcortical ipsilateral and contralateral brain were astonishingly equal in sham and TBI mice, but the ipsilateral perilesional cortex revealed a strong increase in neutral lipids represented by 30 species of triacylglycerols (TGs) of different chain lengths and saturation. The accumulation of TG was localized predominantly to perilesional border cells as revealed by Oil Red O staining. In addition, hexosylceramides (HexCer) and phosphatidylethanolamines (PE and ether-linked PE-O) were reduced. They are precursors of gangliosides and endocannabinoids, respectively. High TG, low HexCer, and low PE/PE-O showed a linear association with non-goal-directed nighttime hyperactivity but not with the loss of avoidance memory. The analyses suggest that TG overload and HexCer and PE deficiencies contributed to behavioral dimensions of post-TBI psychopathology.

Insights into nervous system repair from the fruit fly

Millions of people experience injury to the central nervous system (CNS) each year, many of whom are left permanently disabled, providing a challenging hurdle for the field of regenerative medicine. Repair of damage in the CNS occurs through a concerted effort of phagocytosis of debris, cell proliferation and differentiation to produce new neurons and glia, distal axon/dendrite degeneration, proximal axon/dendrite regeneration and axon re-enwrapment. In humans, regeneration is observed within the peripheral nervous system, while in the CNS injured axons exhibit limited ability to regenerate. This has also been described for the fruit fly Drosophila. Powerful genetic tools available in Drosophila have allowed the response to CNS insults to be probed and novel regulators with mammalian orthologs identified. The conservation of many regenerative pathways, despite considerable evolutionary separation, stresses that these signals are principal regulators and may serve as potential therapeutic targets. Here, we highlight the role of Drosophila CNS injury models in providing key insight into regenerative processes by exploring the underlying pathways that control glial and neuronal activation in response to insult, and their contribution to damage repair in the CNS.

Current Knowledge of Microglia in Traumatic Spinal Cord Injury

Microglia are the resident immune cells in the central nervous system (CNS). After traumatic spinal cord injury (SCI), microglia undergo activation, proliferation, and changes in gene and protein expression and morphology, with detrimental and beneficial effects. Activated microglia cause secondary neuronal injury via the production of proinflammatory cytokines, reactive oxygen species, and proteases. However, activated microglia also promote neuronal repair through the secretion of anti-inflammatory growth factors and cytokines. Proinflammatory cytokines increase endothelial permeability, promote A1 astrocyte activation and axonal demyelination, and reduce neural stem/progenitor cells (NSPCs), leading to the exacerbation of neuronal injury. In contrast, anti-inflammatory factors facilitate angiogenesis, reduce reactive astrocytes, and promote axonal remyelination and the propagation of NSPCs, contributing to tissue repair and locomotor recovery. Due to its limited regenerative capacity, the CNS requires beneficial microglia for continuous protection against injury. Understanding and regulating microglial activation status are beneficial to reducing detrimental effects and promoting repair behaviors and to obtain more information on efficient therapies for traumatic SCI. This review discusses microglial activation and the differences between microglia and similar immune cells, microglial interactions with other cells in the spinal cord, and the progress in the development of therapies targeting microglia in SCI.

The emerging role of the chondroitin sulfate proteoglycan family in neurodegenerative diseases

Chondroitin sulfate (CS) is a kind of linear polysaccharide that is covalently linked to proteins to form proteoglycans. Chondroitin sulfate proteoglycans (CSPGs) consist of a core protein, with one or more CS chains covalently attached. CSPGs are precisely regulated and they exert a variety of physiological functions by binding to adhesion molecules and growth factors. Widely distributed in the nervous system in human body, CSPGs contribute to the major component of extracellular matrix (ECM), where they play an important role in the development and maturation of the nervous system, as well as in the pathophysiological response to damage to the central nervous system (CNS). While there are more than 30 types of CSPGs, this review covers the roles of the most important ones, including versican, aggrecan, neurocan and NG2 in the pathogenesis of neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and multiple sclerosis. The updated reports of the treatment of neurodegenerative diseases are involving CSPGs.

Deciphering glial scar after spinal cord injury

Spinal cord injury (SCI) often leads to permanent disability, which is mainly caused by the loss of functional recovery. In this review, we aimed to investigate why the healing process is interrupted. One of the reasons for this interruption is the formation of a glial scar around the severely damaged tissue, which is usually covered by reactive glia, macrophages and fibroblasts. Aiming to clarify this issue, we summarize the latest research findings pertaining to scar formation, tissue repair, and the divergent roles of blood-derived monocytes/macrophages, ependymal cells, fibroblasts, microglia, oligodendrocyte progenitor cells (OPCs), neuron-glial antigen 2 (NG2) and astrocytes during the process of scar formation, and further analyse the contribution of these cells to scar formation. In addition, we recapitulate the development of therapeutic treatments targeting glial scar components. Altogether, we aim to present a comprehensive decoding of the glial scar and explore potential therapeutic strategies for improving functional recovery after SCI.

Generation and Release of Neurogranin, Vimentin, and MBP Proteolytic Peptides, Following Traumatic Brain Injury

Traumatic brain injury (TBI) is a major neurological disorder without FDA-approved therapies. In this study, we have examined the concept that TBI might trigger global brain proteolysis in the acute post-injury phase. Thus, we conducted a systemic proteolytic peptidomics analysis using acute cerebrospinal fluid (CSF) samples from TBI patients and normal control samples. We employed ultrafiltration-based low molecular weight (LMW; < 10 kDa) peptide enrichment, coupled with nano-reversed-phase liquid chromatography/tandem mass spectrometry analysis, followed with orthogonal quantitative immunoblotting-based protein degradation analysis. We indeed identified novel patterns of injury-dependent proteolytic peptides derived from neuronal components (pre- and post-synaptic terminal, dendrites, axons), extracellular matrix, oligodendrocytes, microglial cells, and astrocytes. Among these, post-synaptic protein neurogranin was identified for the first time converted to neurogranin peptides including neurogranin peptide (aa 16-64) that is phosphorylated at Ser-36/48 (P-NG-fragment) in acute human TBI CSF samples vs. normal control with a receiver operating characteristic area under the curve of 0.957. We also identified detailed processing of astroglia protein (vimentin) and oligodendrocyte protein (MBP and Golli-MBP) to protein breakdown products (BDPs) and/or LMW proteolytic peptides after TBI. In addition, using MS/MS selected reaction monitoring method, two C-terminally released MBP peptides TQDENPVVHFF and TQDENPVVHF were found to be elevated in acute and subacute TBI CSF samples as compared to their normal control counterparts. These findings imply that future therapeutic strategies might be placed on the suppression of brain proteolysis as a target. The endogenous proteolytic peptides discovered in human TBI biofluid could represent useful diagnostic and monitoring tools for TBI.

Microglia as hackers of the matrix: sculpting synapses and the extracellular space

Microglia shape the synaptic environment in health and disease, but synapses do not exist in a vacuum. Instead, pre- and postsynaptic terminals are surrounded by extracellular matrix (ECM), which together with glia comprise the four elements of the contemporary tetrapartite synapse model. While research in this area is still just beginning, accumulating evidence points toward a novel role for microglia in regulating the ECM during normal brain homeostasis, and such processes may, in turn, become dysfunctional in disease. As it relates to synapses, microglia are reported to modify the perisynaptic matrix, which is the diffuse matrix that surrounds dendritic and axonal terminals, as well as perineuronal nets (PNNs), specialized reticular formations of compact ECM that enwrap neuronal subsets and stabilize proximal synapses. The interconnected relationship between synapses and the ECM in which they are embedded suggests that alterations in one structure necessarily affect the dynamics of the other, and microglia may need to sculpt the matrix to modify the synapses within. Here, we provide an overview of the microglial regulation of synapses, perisynaptic matrix, and PNNs, propose candidate mechanisms by which these structures may be modified, and present the implications of such modifications in normal brain homeostasis and in disease.

Identification of a germline CSPG4 variation in a family with neurofibromatosis type 1-like phenotype

Neurofibromatosis type 1 (NF1), an autosomal dominant and multisystem disorder, is generally considered to be caused by NF1 inactivation. However, there are also numerous studies showing that Neurofibromatosis type 1-like phenotype can be caused by the abnormalities in the other genes. Through targeted parallel sequencing, whole-exome sequencing, de novo genomic sequencing, and RNA isoform sequencing, we identified a germline V2097M variation in CSPG4 gene probably increased susceptibility to a NF1-like phenotype family. Besides, a series of in vitro functional studies revealed that this variant promoted cell proliferation by activating the MAPK/ERK signaling pathway via hindering ectodomain cleavage of CSPG4. Our data demonstrate that a germline variation in the CSPG4 gene might be a high risk to cause NF1-like phenotype. To our knowledge, this is the first report of mutations in the CSPG4 gene in human diseases.

Neural Tissue Homeostasis and Repair Is Regulated via CS and DS Proteoglycan Motifs

Chondroitin sulfate (CS) is the most abundant and widely distributed glycosaminoglycan (GAG) in the human body. As a component of proteoglycans (PGs) it has numerous roles in matrix stabilization and cellular regulation. This chapter highlights the roles of CS and CS-PGs in the central and peripheral nervous systems (CNS/PNS). CS has specific cell regulatory roles that control tissue function and homeostasis. The CNS/PNS contains a diverse range of CS-PGs which direct the development of embryonic neural axonal networks, and the responses of neural cell populations in mature tissues to traumatic injury. Following brain trauma and spinal cord injury, a stabilizing CS-PG-rich scar tissue is laid down at the defect site to protect neural tissues, which are amongst the softest tissues of the human body. Unfortunately, the CS concentrated in gliotic scars also inhibits neural outgrowth and functional recovery. CS has well known inhibitory properties over neural behavior, and animal models of CNS/PNS injury have demonstrated that selective degradation of CS using chondroitinase improves neuronal functional recovery. CS-PGs are present diffusely in the CNS but also form denser regions of extracellular matrix termed perineuronal nets which surround neurons. Hyaluronan is immobilized in hyalectan CS-PG aggregates in these perineural structures, which provide neural protection, synapse, and neural plasticity, and have roles in memory and cognitive learning. Despite the generally inhibitory cues delivered by CS-A and CS-C, some CS-PGs containing highly charged CS disaccharides (CS-D, CS-E) or dermatan sulfate (DS) disaccharides that promote neural outgrowth and functional recovery. CS/DS thus has varied cell regulatory properties and structural ECM supportive roles in the CNS/PNS depending on the glycoform present and its location in tissue niches and specific cellular contexts. Studies on the fruit fly, Drosophila melanogaster and the nematode Caenorhabditis elegans have provided insightful information on neural interconnectivity and the role of the ECM and its PGs in neural development and in tissue morphogenesis in a whole organism environment.

Single intracerebroventricular progranulin injection adversely affects the blood-brain barrier in experimental traumatic brain injury

Progranulin (PGRN) is a neurotrophic and anti-inflammatory factor with protective effects in animal models of ischemic stroke, subarachnoid hemorrhage, and traumatic brain injury (TBI). Administration of recombinant (r) PGRN prevents exaggerated brain pathology after TBI in Grn-deficient mice, suggesting that local injection of recombinant progranulin (rPGRN) provides therapeutic benefit in the acute phase of TBI. To test this hypothesis, we subjected adult male C57Bl/6N mice to the controlled cortical impact model of TBI, administered a single dose of rPGRN intracerebroventricularly (ICV) shortly before the injury, and examined behavioral and biological effects up to 5 days post injury (dpi). The anti-inflammatory bioactivity of rPGRN was confirmed by its capability to inhibit the inflammation-induced hypertrophy of murine primary microglia and astrocytes in vitro. In C57Bl/6N mice, however, ICV administration of rPGRN failed to attenuate behavioral deficits over the 5-day observation period. (Immuno)histological gene and protein expression analyses at 5 dpi did not reveal a therapeutic benefit in terms of brain injury size, brain inflammation, glia activation, cell numbers in neurogenic niches, and neuronal damage. Instead, we observed a failure of TBI-induced mRNA upregulation of the tight junction protein occludin and increased extravasation of serum immunoglobulin G into the brain parenchyma at 5 dpi. In conclusion, single ICV administration of rPGRN had not the expected protective effects in the acute phase of murine TBI, but appeared to cause an aggravation of blood-brain barrier disruption. The data raise questions about putative PGRN-boosting approaches in other types of brain injuries and disease.

CSPGs promote the migration of meningeal fibroblasts via p38 mitogen-activated protein kinase signaling pathway under OGD conditions

AIMS

Usually glial scar that occurs after central nervous system injury has significantly affected the local neural microenvironment. Meningeal fibroblasts play an essential role in the formation of the glial scar. However, how and why meningeal fibroblasts migrate to lesion sites is still unclear.

MAIN METHODS

Astrocytes were subjected to oxygen-glucose deprivation/reperfusion (OGD/R) injury. And then, we measured the glial fibrillary acidic protein(GFAP) and chondroitin sulfate proteoglycans (CSPGs) expression of reactive astrocytes by western blot and quantitative polymerase chain reaction (qPCR) after they were co-cultured with meningeal fibroblasts. Following, we clarified the possibility that CSPGs induce the migration of meningeal fibroblasts to glial scar by transwell migration assay and the activation of the p38 MAPK signaling pathway during the migration by western blot.

KEY FINDINGS

We found that co-cultured meningeal fibroblasts could alleviate the significantly increased expression of GFAP and CSPGs in the activation of reactive astrocytes induced by OGD/R. Additionally, CSPGs secreted by reactive astrocytes could induce the migration of meningeal fibroblasts and the expression of phospho-p38 in meningeal fibroblasts when meningeal fibroblasts were co-cultured with supernatant of reactive astrocytes. What's more, we could observe a noticeable increase in CSPGs that chondroitinase ABC could reverse their functions. Moreover, phospho-p38 could cause the expression of phospho-cofilin and the migration of CSPGs-induced meningeal fibroblasts.

SIGNIFICANCE

Our study provides reliable evidence for explaining scar formation mechanisms and further studying to improve regeneration after an injury to the central nervous system.

Neural crest cell-derived pericytes act as pro-angiogenic cells in human neocortex development and gliomas

Central nervous system diseases involving the parenchymal microvessels are frequently associated with a ‘microvasculopathy’, which includes different levels of neurovascular unit (NVU) dysfunction, including blood–brain barrier alterations. To contribute to the understanding of NVU responses to pathological noxae, we have focused on one of its cellular components, the microvascular pericytes, highlighting unique features of brain pericytes with the aid of the analyses carried out during vascularization of human developing neocortex and in human gliomas. Thanks to their position, centred within the endothelial/glial partition of the vessel basal lamina and therefore inserted between endothelial cells and the perivascular and vessel-associated components (astrocytes, oligodendrocyte precursor cells (OPCs)/NG2-glia, microglia, macrophages, nerve terminals), pericytes fulfil a central role within the microvessel NVU. Indeed, at this critical site, pericytes have a number of direct and extracellular matrix molecule- and soluble factor-mediated functions, displaying marked phenotypical and functional heterogeneity and carrying out multitasking services. This pericytes heterogeneity is primarily linked to their position in specific tissue and organ microenvironments and, most importantly, to their ontogeny. During ontogenesis, pericyte subtypes belong to two main embryonic germ layers, mesoderm and (neuro)ectoderm, and are therefore expected to be found in organs ontogenetically different, nonetheless, pericytes of different origin may converge and colonize neighbouring areas of the same organ/apparatus. Here, we provide a brief overview of the unusual roles played by forebrain pericytes in the processes of angiogenesis and barriergenesis by virtue of their origin from midbrain neural crest stem cells. A better knowledge of the ontogenetic subpopulations may support the understanding of specific interactions and mechanisms involved in pericyte function/dysfunction, including normal and pathological angiogenesis, thereby offering an alternative perspective on cell subtype-specific therapeutic approaches.

Neural crest cell-derived pericytes act as pro-angiogenic cells in human neocortex development and gliomas

Central nervous system diseases involving the parenchymal microvessels are frequently associated with a ‘microvasculopathy’, which includes different levels of neurovascular unit (NVU) dysfunction, including blood–brain barrier alterations. To contribute to the understanding of NVU responses to pathological noxae, we have focused on one of its cellular components, the microvascular pericytes, highlighting unique features of brain pericytes with the aid of the analyses carried out during vascularization of human developing neocortex and in human gliomas. Thanks to their position, centred within the endothelial/glial partition of the vessel basal lamina and therefore inserted between endothelial cells and the perivascular and vessel-associated components (astrocytes, oligodendrocyte precursor cells (OPCs)/NG2-glia, microglia, macrophages, nerve terminals), pericytes fulfil a central role within the microvessel NVU. Indeed, at this critical site, pericytes have a number of direct and extracellular matrix molecule- and soluble factor-mediated functions, displaying marked phenotypical and functional heterogeneity and carrying out multitasking services. This pericytes heterogeneity is primarily linked to their position in specific tissue and organ microenvironments and, most importantly, to their ontogeny. During ontogenesis, pericyte subtypes belong to two main embryonic germ layers, mesoderm and (neuro)ectoderm, and are therefore expected to be found in organs ontogenetically different, nonetheless, pericytes of different origin may converge and colonize neighbouring areas of the same organ/apparatus. Here, we provide a brief overview of the unusual roles played by forebrain pericytes in the processes of angiogenesis and barriergenesis by virtue of their origin from midbrain neural crest stem cells. A better knowledge of the ontogenetic subpopulations may support the understanding of specific interactions and mechanisms involved in pericyte function/dysfunction, including normal and pathological angiogenesis, thereby offering an alternative perspective on cell subtype-specific therapeutic approaches.

Myelin Debris Stimulates NG2/CSPG4 Expression in Bone Marrow-Derived Macrophages in the Injured Spinal Cord

Although the increased expression of members of the chondroitin sulfate proteoglycan family, such as neuron-glial antigen 2 (NG2), have been well documented after an injury to the spinal cord, a complete picture as to the cellular origins and function of this NG2 expression has yet to be made. Using a spinal cord injury (SCI) mouse model, we describe that some infiltrated bone marrow-derived macrophages (BMDMΦ) are early contributors to NG2/CSPG4 expression and secretion after SCI. We demonstrate for the first time that a lesion-related form of cellular debris generated from damaged myelin sheaths can increase NG2/CSPG4 expression in BMDMΦ, which then exhibit enhanced proliferation and decreased phagocytic capacity. These results suggest that BMDMΦ may play a much more nuanced role in secondary spinal cord injury than previously thought, including acting as early contributors to the NG2 component of the glial scar.

Pharmacologic Inhibition of ADAM10 Attenuates Brain Tissue Loss, Axonal Injury and Pro-inflammatory Gene Expression Following Traumatic Brain Injury in Mice

The α-secretase A disintegrin and metalloprotease 10 (ADAM10) regulates various physiological and pathophysiological processes. Despite its broad functional implications during development, plasticity, and disease, no pharmacological approaches to inhibit ADAM10 in acute brain injury have been reported. Here, we examined the effects of the ADAM10 inhibitor GI254023X on the neurological and histopathological outcome after experimental traumatic brain injury (TBI). C57BL/6N mice were subjected to the controlled cortical impact (CCI) model of TBI or sham procedure and received GI254023X or vehicle during the acute phase of injury (n = 40, 100 mg/kg, 25% DMSO, 0.1 M Na2CO3, intraperitoneal, 30 min and 24 h after TBI). GI254023X treatment did not improve neurological deficits from 1 to 7 days post-injury (dpi) but animals treated with GI254023X exhibited smaller brain lesions compared to vehicle treatment. Determination of brain mRNA expression by quantitative PCR showed that TBI-induced up-regulation of Adam10 and Adam17 was not influenced by GI254023X but the up-regulation of the matrix metalloproteinase genes Mmp2 and Mmp9 was attenuated. GI254023X treatment further increased the T cell marker Cd247 but did not affect blood brain barrier integrity, as assessed by Occludin mRNA expression and IgG brain extravasation. However, in agreement with neuroprotective effects of ADAM10 inhibition, GI254023X treatment attenuated axonal injury, as indicated by decreased generation of spectrin breakdown products (SBDPs) and decreased immunostaining using anti-non-phosphorylated neurofilament (SMI-32). Interestingly, reduced axonal injury in GI254023X-treated animals coincided with subtle mRNA dysregulation in the glutamate receptor subunit genes Gria1 and Grin2b. Quantitative PCR also revealed that GI254023X mitigated up-regulation of the pro-inflammatory markers Il6, Tnfa, and Lcn2 but not the up-regulation of the pan-microglia marker Aif1, the M2 microglia marker Arg1 and the reactive astrocyte marker Gfap. Taken together, the ADAM10 inhibitor GI254023X attenuates brain tissue loss, axonal injury and pro-inflammatory gene expression in the CCI model of TBI. These results suggest that ADAM10 may represent a therapeutic target in the acute phase of TBI.

Strategies for Oligodendrocyte and Myelin Repair in Traumatic CNS Injury

A major consequence of traumatic brain and spinal cord injury is the loss of the myelin sheath, a cholesterol-rich layer of insulation that wraps around axons of the nervous system. In the central nervous system (CNS), myelin is produced and maintained by oligodendrocytes. Damage to the CNS may result in oligodendrocyte cell death and subsequent loss of myelin, which can have serious consequences for functional recovery. Demyelination impairs neuronal function by decelerating signal transmission along the axon and has been implicated in many neurodegenerative diseases. After a traumatic injury, mechanisms of endogenous remyelination in the CNS are limited and often fail, for reasons that remain poorly understood. One area of research focuses on enhancing this endogenous response. Existing techniques include the use of small molecules, RNA interference (RNAi), and monoclonal antibodies that target specific signaling components of myelination for recovery. Cell-based replacement strategies geared towards replenishing oligodendrocytes and their progenitors have been utilized by several groups in the last decade as well. In this review article, we discuss the effects of traumatic injury on oligodendrocytes in the CNS, the lack of endogenous remyelination, translational studies in rodent models promoting remyelination, and finally human clinical studies on remyelination in the CNS after injury.

Administration of all-trans retinoic acid after experimental traumatic brain injury is brain protective

BACKGROUND AND PURPOSE

All-trans retinoic acid (ATRA) is a vitamin A metabolite, important in the developing and mature brain. Pre-injury ATRA administration ameliorates ischaemic brain insults in rodents. This study examined the effects of post-traumatic ATRA treatment in experimental traumatic brain injury (TBI).

EXPERIMENTAL APPROACH

Male adult mice were subjected to the controlled cortical impact model of TBI or sham procedure and killed at 7 or 30 days post-injury (dpi). ATRA (10 mg kg-1, i.p.) was given immediately after the injury and 1, 2 and 3 dpi. Neurological function and sensorimotor coordination were evaluated. Brains were processed for (immuno-) histological, mRNA and protein analyses (qPCR and western blot).

KEY RESULTS

ATRA treatment reduced brain lesion size, reactive astrogliosis and axonal injury at 7 dpi, and hippocampal granule cell layer (GCL) integrity was protected at 7 and 30 dpi, independent of cell proliferation in neurogenic niches and blood-brain barrier damage. Neurological and motor deficits over time and the brain tissue loss at 30 dpi were not affected by ATRA treatment. ATRA decreased gene expression of markers for damage-associated molecular pattern (HMGB1), apoptosis (caspase-3 and Bax), activated microglia (TSPO), and reactive astrogliosis (GFAP, SerpinA3N) at 7 dpi and a subset of markers at 30 dpi (TSPO, GFAP).

CONCLUSION AND IMPLICATIONS

In experimental TBI, post-traumatic ATRA administration exerted brain protective effects, including long-term protection of GCL integrity, but did not affect neurological and motor deficits. Further investigations are required to optimize treatment regimens to enhance ATRA's brain protective effects and improve outcomes.

Extracellular Matrix in Neural Plasticity and Regeneration

The extracellular matrix (ECM) is a fundamental component of biological tissues. The ECM in the central nervous system (CNS) is unique in both composition and function. Functions such as learning, memory, synaptogenesis, and plasticity are regulated by numerous ECM molecules. The neural ECM acts as a non-specific physical barrier that modulates neuronal plasticity and axon regeneration. There are two specialized types of ECM in the CNS, diffuse perisynaptic ECM and condensed ECM, which selectively surround the perikaryon and initial part of dendritic trees in subtypes of neurons, forming perineuronal nets. This review presents the current knowledge about the role of important neuronal ECM molecules in maintaining the basic functions of a neuron, including electrogenesis and the ability to form neural circuits. The review mainly focuses on the role of ECM components that participate in the control of key events such as cell survival, axonal growth, and synaptic remodeling. Particular attention is drawn to the numerous molecular partners of the main ECM components. These regulatory molecules are integrated into the cell membrane or disposed into the matrix itself in solid or soluble form. The interaction of the main matrix components with molecular partners seems essential in molecular mechanisms controlling neuronal functions. Special attention is paid to the chondroitin sulfate proteoglycan 4, type 1 transmembrane protein, neural-glial antigen 2 (NG2/CSPG4), whose cleaved extracellular domain is such a molecular partner that it not only acts directly on neural and vascular cells, but also exerts its influence indirectly by binding to resident ECM molecules.

Acute brain injuries trigger microglia as an additional source of the proteoglycan NG2

NG2 is a type I transmembrane glycoprotein known as chondroitin sulfate proteoglycan 4 (CSPG4). In the healthy central nervous system, NG2 is exclusively expressed by oligodendrocyte progenitor cells and by vasculature pericytes. A large body of immunohistochemical studies showed that under pathological conditions such as acute brain injuries and experimental autoimmune encephalomyelitis (EAE), a number of activated microglia were NG2 immuno-positive, suggesting NG2 expression in these cells. Alternative explanations for the microglial NG2 labeling consider the biochemical properties of NG2 or the phagocytic activity of activated microglia. Reportedly, the transmembrane NG2 proteoglycan can be cleaved by a variety of proteases to deposit the NG2 ectodomain into the extracellular matrix. The ectodomain, however, could also stick to the microglial surface. Since microglia are phagocytic cells engulfing debris of dying cells, it is difficult to identify a genuine expression of NG2. Recent studies showing (1) pericytes giving rise to microglial after stroke, and (2) immune cells of NG2-EYFP knock-in mice lacking NG2 expression in an EAE model generated doubts for the de novo expression of NG2 in microglia after acute brain injuries. In the current study, we took advantage of three knock-in mouse lines (NG2-CreERT2, CX₃CR₁-EGFP and NG2-EYFP) to study NG2 expression indicated by transgenic fluorescent proteins in microglia after tMCAO (transient middle cerebral artery occlusion) or cortical stab wound injury (SWI). We provide strong evidence that NG2-expressing cells, including OPCs and pericytes, did not differentiate into microglia after acute brain injuries, whereas activated microglia did express NG2 in a disease-dependent manner. A subset of microglia continuously activated the NG2 gene at least within the first week after tMCAO, whereas within 3 days after SWI a limited number of microglia at the lesion site transiently expressed NG2. Immunohistochemical studies demonstrated that these microglia with NG2 gene activity also synthesized the NG2 protein, suggesting activated microglia as an additional source of the NG2 proteoglycan after acute brain injuries.

A Clonal NG2-Glia Cell Response in a Mouse Model of Multiple Sclerosis

NG2-glia, also known as oligodendrocyte precursor cells (OPCs), have the potential to generate new mature oligodendrocytes and thus, to contribute to tissue repair in demyelinating diseases like multiple sclerosis (MS). Once activated in response to brain damage, NG2-glial cells proliferate, and they acquire a reactive phenotype and a heterogeneous appearance. Here, we set out to investigate the distribution and phenotypic diversity of NG2-glia relative to their ontogenic origin, and whether there is a clonal NG2-glial response to lesion in an experimental autoimmune encephalomyelitis (EAE) murine model of MS. As such, we performed in utero electroporation of the genomic lineage tracer, StarTrack, to follow the fate of NG2-glia derived from single progenitors and to evaluate their response to brain damage after EAE induction. We then analyzed the dispersion of the NG2-glia derived clonally from single pallial progenitors in the brain of EAE mice. In addition, we examined several morphological parameters to assess the degree of NG2-glia reactivity in clonally-related cells. Our results reveal the heterogeneity of these progenitors and their cell progeny in a scenario of autoimmune demyelination, revealing the ontogenic phenomena at play in these processes.

Progranulin/EphA2 axis: A novel oncogenic mechanism in bladder cancer

The growth factor progranulin plays a critical role in bladder cancer by modulating tumor cell motility and invasion. Progranulin regulates remodeling of the actin cytoskeleton by interacting with drebrin, an actin binding protein that regulates tumor growth. We previously discovered that progranulin depletion inhibits epithelial-to-mesenchymal transition and markedly reduces in vivo tumor growth. Moreover, progranulin depletion sensitizes urothelial cancer cells to cisplatin treatment, further substantiating a pro-survival function of progranulin. Until recently, the progranulin signaling receptor remained unidentified, precluding a full understanding of progranulin action in tumor cell biology. We recently identified EphA2, a member of a large family of receptor tyrosine-kinases, as the functional receptor for progranulin. However, it is not established whether EphA2 plays an oncogenic role in bladder cancer. Here we demonstrate that progranulin, and not ephrin-A1, the canonical ligand for EphA2, is the predominant EphA2 ligand in bladder cancer. Progranulin evoked Akt- and Erk1/2-mediated EphA2 phosphorylation at Ser897, which could drive bladder tumorigenesis. We discovered that EphA2 depletion severely blunted progranulin-dependent motility and anchorage-independent growth, and sensitized bladder cancer cells to cisplatin treatment. We further defined the mechanisms of progranulin/EphA2-dependent motility by identifying liprin-α1 as a novel progranulin-dependent EphA2 interacting protein and establishing its critical role in cell motility. The discovery of EphA2 as the functional signaling receptor for progranulin and the identification of novel downstream effectors offer a new avenue for understanding the underlying mechanism of progranulin action and may constitute novel clinical and therapeutic targets in bladder cancer.

NrCAM is a marker for substrate-selective activation of ADAM10 in Alzheimer's disease

The metalloprotease ADAM10 is a drug target in Alzheimer's disease, where it cleaves the amyloid precursor protein (APP) and lowers amyloid‐beta. Yet, ADAM10 has additional substrates, which may cause mechanism‐based side effects upon therapeutic ADAM10 activation. However, they may also serve—in addition to APP—as biomarkers to monitor ADAM10 activity in patients and to develop APP‐selective ADAM10 activators. Our study demonstrates that one such substrate is the neuronal cell adhesion protein NrCAM. ADAM10 controlled NrCAM surface levels and regulated neurite outgrowth in vitro in an NrCAM‐dependent manner. However, ADAM10 cleavage of NrCAM, in contrast to APP, was not stimulated by the ADAM10 activator acitretin, suggesting that substrate‐selective ADAM10 activation may be feasible. Indeed, a whole proteome analysis of human CSF from a phase II clinical trial showed that acitretin, which enhanced APP cleavage by ADAM10, spared most other ADAM10 substrates in brain, including NrCAM. Taken together, this study demonstrates an NrCAM‐dependent function for ADAM10 in neurite outgrowth and reveals that a substrate‐selective, therapeutic ADAM10 activation is possible and may be monitored with NrCAM.

Beneficial and Detrimental Remodeling of Glial Connexin and Pannexin Functions in Rodent Models of Nervous System Diseases

A variety of glial cell functions are supported by connexin and pannexin proteins. These functions include the modulation of synaptic gain, the control of excitability through regulation of the ion and neurotransmitter composition of the extracellular milieu and the promotion of neuronal survival. Connexins and pannexins support these functions through diverse molecular mechanisms, including channel and non-channel functions. The former comprise the formation of gap junction-mediated networks supported by connexin intercellular channels and the formation of pore-like membrane structures or hemichannels formed by both connexins and pannexins. Non-channel functions involve adhesion properties and the participation in signaling intracellular cascades. Pathological conditions of the nervous system such as ischemia, neurodegeneration, pathogen infection, trauma and tumors are characterized by distinctive remodeling of connexin expression and function. However, whether these changes can be interpreted as part of the pathogenesis, or as beneficial compensatory effects, remains under debate. Here we review the available evidence addressing this matter with a special emphasis in mouse models with selective manipulation of glial connexin and pannexin proteins in vivo. We postulate that the beneficial vs. detrimental effects of glial connexin remodeling in pathological conditions depend on the impact of remodeling on the different connexin and pannexin channel and non-channel functions, on the characteristics of the inflammatory environment and on the type of interaction among glial cells types.

Progranulin deficiency confers resistance to autoimmune encephalomyelitis in mice

Progranulin is a secreted neurotrophin that assists in the autophagolysosomal pathways that contribute to MHC-mediated antigen processing, pathogen removal, and autoimmunity. We showed that patients with multiple sclerosis (MS) have high levels of circulating progranulin and that its depletion in a mouse model by a monoclonal antibody aggravates MS-like experimental autoimmune encephalomyelitis (EAE). However, unexpectedly, progranulin-deficient mice (Grn^−/−) were resistant to EAE, and this resistance was fully restored by wild-type bone marrow transplantation. FACS analyses revealed a loss of MHC-II-positive antigen-presenting cells in Grn^−/− mice and a reduction in the number of CD8+ and CD4+ T-cells along with a strong increase in the number of scavenger receptor class B (CD36+) phagocytes, suggesting defects in antigen presentation along with a compensatory increase in phagocytosis. Indeed, bone marrow-derived dendritic cells from Grn^−/− mice showed stronger uptake of antigens but failed to elicit antigen-specific T-cell proliferation. An increase in the number of CD36+ phagocytes was associated with increased local inflammation at the site of immunization, stronger stimulation-evoked morphological transformation of bone marrow-derived macrophages to phagocytes, an increase in the phagocytosis of E. coli particles and latex beads and defects in the clearance of the material. Hence, the outcomes in the EAE model reflect the dichotomy of progranulin-mediated immune silencing and autoimmune mechanisms of antigen recognition and presentation, and our results reveal a novel progranulin-dependent pathway in autoimmune encephalomyelitis.

Comprehensive Proteomic Analysis Reveals Intermediate Stage of Non-Lesional Psoriatic Skin and Points out the Importance of Proteins Outside this Trend

To better understand the pathomechanism of psoriasis, a comparative proteomic analysis was performed with non-lesional and lesional skin from psoriasis patients and skin from healthy individuals. Strikingly, 79.9% of the proteins that were differentially expressed in lesional and healthy skin exhibited expression levels in non-lesional skin that were within twofold of the levels observed in healthy and lesional skin, suggesting that non-lesional skin represents an intermediate stage. Proteins outside this trend were categorized into three groups: I. proteins in non-lesional skin exhibiting expression similar to lesional skin, which might be predisposing factors (i.e., CSE1L, GART, MYO18A and UGDH); II. proteins that were differentially expressed in non-lesional and lesional skin but not in healthy and lesional skin, which might be non-lesional characteristic alteration (i.e., CHCHD6, CHMP5, FLOT2, ITGA7, LEMD2, NOP56, PLVAP and RRAS); and III. proteins with contrasting differential expression in non-lesional and lesional skin compared to healthy skin, which might contribute to maintaining the non-lesional state (i.e., ITGA7, ITGA8, PLVAP, PSAPL1, SMARCA5 and XP32). Finally, proteins differentially expressed in lesions may indicate increased sensitivity to stimuli, peripheral nervous system alterations, furthermore MYBBP1A and PRKDC were identified as potential regulators of key pathomechanisms, including stress and immune response, proliferation and differentiation.

Depletion of regulatory T cells increases T cell brain infiltration, reactive astrogliosis, and interferon-γ gene expression in acute experimental traumatic brain injury

Background

Traumatic brain injury (TBI) is a major cause of death and disability. T cells were shown to infiltrate the brain during the first days after injury and to exacerbate tissue damage. The objective of this study was to investigate the hitherto unresolved role of immunosuppressive, regulatory T cells (Tregs) in experimental TBI.

Methods

“Depletion of regulatory T cell” (DEREG) and wild type (WT) C57Bl/6 mice, treated with diphtheria toxin (DTx) to deplete Tregs or to serve as control, were subjected to the controlled cortical impact (CCI) model of TBI. Neurological and motor deficits were examined until 5 days post-injury (dpi). At the 5 dpi endpoint, (immuno-) histological, protein, and gene expression analyses were carried out to evaluate the consequences of Tregs depletion. Comparison of parametric or non-parametric data between two groups was done using Student’s t test or the Mann-Whitney U test. For multiple comparisons, p values were calculated by one-way or two-way ANOVA followed by specific post hoc tests.

Results

The overall neurological outcome at 5 dpi was not different between DEREG and WT mice but more severe motor deficits occurred transiently at 1 dpi in DEREG mice. DEREG and WT mice did not differ in the extent of brain damage, blood-brain barrier (BBB) disruption, or neuronal excitotoxicity, as examined by lesion volumetry, immunoglobulin G (IgG) extravasation, or calpain-generated αII-spectrin breakdown products (SBDPs), respectively. In contrast, increased protein levels of glial fibrillary acidic protein (GFAP) and GFAP+ astrocytes in the ipsilesional brain tissue indicated exaggerated reactive astrogliosis in DEREG mice. T cell counts following anti-CD3 immunohistochemistry and gene expression analyses of Cd247 (CD3 subunit zeta) and Cd8a (CD8a) further indicated an increased number of T cells infiltrating the brain injury sites of DEREG mice compared to WT. These changes coincided with increased gene expression of pro-inflammatory interferon-γ (Ifng) in DEREG mice compared to WT in the injured brain.

Conclusions

The results show that the depletion of Tregs attenuates T cell brain infiltration, reactive astrogliosis, interferon-γ gene expression, and transiently motor deficits in murine acute traumatic brain injury.

Dynamic cell type-specific expression of Nrf2 after traumatic brain injury in mice

Nrf2 plays a pivotal role in antioxidant response and anti-inflammation after traumatic brain injury (TBI), and its deletion aggravates TBI-induced brain damage. Previous studies have demonstrated that Nrf2 is activated post TBI, but dynamic changes in expression and cell type-specific characteristics remain unclear. In this study, the Feeney weight-drop contusion model was conducted to mimic TBI, and the ipsilateral cerebral cortex was collected at 1, 3, 7 and 14 days post TBI (dpi). Nrf2 protein levels were observed by western blot. Cell type-specific localization of Nrf2 after TBI was detected at different time intervals by double immunofluorescence staining. NeuN, GFAP, IBA1 and NG2 were used as cell type-specific markers to neurons, astrocytes, microglia and NG2 glia, respectively. After TBI, Nrf2 protein levels peaked at 1 dpi. Robust transient Nrf2 accumulation was co-localized with neurons, which was predominant at 1 dpi. Continuous weak Nrf2 expression was detected in activated astrocytes, and the number of double positive cells peaked at 7 dpi. Inducible widespread immunostaining of Nrf2 was observed in the nucleus of the microglia, and the number of Nrf2+ microglia peaked at 7 dpi. In addition, we also explored colocalization of Nrf2 in NG2 glia, in which the percentage of Nrf2+ in NG2 glia reached a climax at 3 dpi. This study reveals that the accumulation of endogenous Nrf2 might mediate different pathophysical roles in neurons and glias after TBI, the cell-type specific and time-dependent expression provide insights to explain the roles of Nrf2 in different neural cells.

Role of heparan sulfate 6-0 endosulfatases in intervertebral disc homeostasis

The expression of heparan sulfate endosulfatases (Sulfs) was investigated in the intervertebral disc (IVD) to clarify their role in IVD homeostasis. Sulf-1 and -2 expression were elucidated in normal and degenerated human IVD. Age-related effects on Sulf expression, type II collagen levels, and structural changes were analyzed in IVDs of wild-type (WT) and Sulf-1 knockout (Sulf-1⁻/⁻) mice. The effect of recombinant Sulf-1 (100 ng/ml) and Sulf-1 knockdown on heparan sulfate proteoglycan and collagen expression in ATDC5 cells were examined. Finally, the effect of Sulf-1 on transforming growth factor (TGF) β1-induced signaling was evaluated. Results show that Sulf-1 and -2 levels were higher in degenerated human IVDs. In WT mice, Sulf-1 and -2 expression generally declined as the animals aged. In particular, Sulf-1 in the nucleus pulposus was higher compared with Sulf-2 at the age of 1 and 6 months and significantly declined with aging. Sulf-1⁻/⁻ mice showed more severe IVD pathology than WT mice, with lower type II collagen levels in nucleus pulposus, and degeneration with type I collagen in annulus fibrosus. In vitro, Sulf-1 induced type II collagen expression and significantly increased TGF-β1-induced Smad2/3 phosphorylation in ATDC5 cells. In conclusion, Sulf-1 might play a critical role from development to maintenance of IVD homeostasis by regulating collagen expression.

Curcumin Can Improve Spinal Cord Injury by Inhibiting TGF-β-SOX9 Signaling Pathway

Spinal cord injury (SCI) is a severe nervous system disease with high morbidity and disability rate. Signaling pathways play a key role in the neuronal restorative mechanism following SCI. SRY-related high mobility group (HMG)-box gene 9 (SOX9) affects glial scar formation via Transforming growth factor beta (TGF-β) signaling pathway. Activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) is transferred into nucleus to upregulate TGF-β-SOX9. Curcumin exhibits potent anti-inflammatory and anti-oxidant properties. Curcumin can play an important role in SCI recovery by inhibiting the expression of NF-κB and TGF-β-SOX9. Herein, we review the potential mechanism of curcumin-inhibiting SOX9 signaling pathway in SCI treatment. The inhibition of NF-κB and SOX9 signaling pathway by curcumin has the potentiality of serving as neuronal regenerative mechanism following SCI.

Functional Consequences of Keratan Sulfate Sulfation in Electrosensory Tissues and in Neuronal Regulation

Keratan sulfate (KS) is a functional electrosensory and neuro-instructive molecule. Recent studies have identified novel low sulfation KS in auditory and sensory tissues such as the tectorial membrane of the organ of Corti and the Ampullae of Lorenzini in elasmobranch fish. These are extremely sensitive proton gradient detection systems that send signals to neural interfaces to facilitate audition and electrolocation. High and low sulfation KS have differential functional roles in song learning in the immature male zebra song-finch with high charge density KS in song nuclei promoting brain development and cognitive learning. The conductive properties of KS are relevant to the excitable neural phenotype. High sulfation KS interacts with a large number of guidance and neuroregulatory proteins. The KS proteoglycan microtubule associated protein-1B (MAP1B) stabilizes actin and tubulin cytoskeletal development during neuritogenesis. A second 12 span transmembrane synaptic vesicle associated KS proteoglycan (SV2) provides a smart gel storage matrix for the storage of neurotransmitters. MAP1B and SV2 have prominent roles to play in neuroregulation. Aggrecan and phosphacan have roles in perineuronal net formation and in neuroregulation. A greater understanding of the biology of KS may be insightful as to how neural repair might be improved.

Sex hormones modulate pathogenic processes in experimental traumatic brain injury

Clinical and animal studies have revealed sex-specific differences in histopathological and neurological outcome after traumatic brain injury (TBI). The impact of perioperative administration of sex steroid inhibitors on TBI is still elusive. Here, we subjected male and female C57Bl/6N mice to the controlled cortical impact (CCI) model of TBI and applied pharmacological inhibitors of steroid hormone synthesis, that is, letrozole (LET, inhibiting estradiol synthesis by aromatase) and finasteride (FIN, inhibiting dihydrotestosterone synthesis by 5α-reductase), respectively, starting 72 h prior CCI, and continuing for a further 48 h after CCI. Initial gene expression analyses showed that androgen (Ar) and estrogen receptors (Esr1) were sex-specifically altered 72 h after CCI. When examining brain lesion size, we found larger lesions in male than in female mice, but did not observe effects of FIN or LET treatment. However, LET treatment exacerbated neurological deficits 24 and 72 h after CCI. On the molecular level, FIN administration reduced calpain-dependent spectrin breakdown products, a proxy of excitotoxicity and disturbed Ca²⁺ homeostasis, specifically in males, whereas LET increased the reactive astrocyte marker glial fibrillary acid protein specifically in females. Examination of neurotrophins (brain-derived neurotrophic factor, neuronal growth factor, NT-3) and their receptors (p75^NTR , TrkA, TrkB, TrkC) revealed CCI-induced down-regulation of TrkB and TrkC protein expression, which was reduced by LET in both sexes. Interestingly, FIN decreased neuronal growth factor mRNA expression and protein levels of its receptor TrkA only in males. Taken together, our data suggest a sex-specific impact on pathogenic processes in the injured brain after TBI. Sex hormones may thus modulate pathogenic processes in experimental TBI.

Meeting Between Rumi and Shams in Notch Signaling; Implications for Pain Management: A Narrative Review

The meeting between Rumi and Shams, in the 13th century, was a turning point in the life of Rumi leading to a revolutionary effect in his thoughts, ideas, and poems. This was an ever-inspiring meeting with many results throughout the centuries. This meeting has created some footprints in cellular and molecular medicine: The discovery of two distinct genes in Drosophila, i.e. Rumi and Shams and their role in controlling Notch signaling, which has a critical role in cell biology. This nomination and the interactions between the two genes has led us to a number of novel studies during the last years. This article reviews the interactions between Rumi and Shams and their effects on Notch signaling in order to find potential novel drugs for pain control through drug development studies in the future.

Glycans and glycosaminoglycans in neurobiology: key regulators of neuronal cell function and fate

The aim of the present study was to examine the roles of l-fucose and the glycosaminoglycans (GAGs) keratan sulfate (KS) and chondroitin sulfate/dermatan sulfate (CS/DS) with selected functional molecules in neural tissues. Cell surface glycans and GAGs have evolved over millions of years to become cellular mediators which regulate fundamental aspects of cellular survival. The glycocalyx, which surrounds all cells, actuates responses to growth factors, cytokines and morphogens at the cellular boundary, silencing or activating downstream signaling pathways and gene expression. In this review, we have focused on interactions mediated by l-fucose, KS and CS/DS in the central and peripheral nervous systems. Fucose makes critical contributions in the area of molecular recognition and information transfer in the blood group substances, cytotoxic immunoglobulins, cell fate-mediated Notch-1 interactions, regulation of selectin-mediated neutrophil extravasation in innate immunity and CD-34-mediated new blood vessel development, and the targeting of neuroprogenitor cells to damaged neural tissue. Fucosylated glycoproteins regulate delivery of synaptic neurotransmitters and neural function. Neural KS proteoglycans (PGs) were examined in terms of cellular regulation and their interactive properties with neuroregulatory molecules. The paradoxical properties of CS/DS isomers decorating matrix and transmembrane PGs and the positive and negative regulatory cues they provide to neurons are also discussed.

[The role of glial scar on axonal regeneration after spinal cord injury]

The 'glial scar' has been widely studied in the regeneration of spinal cord injury (SCI). For decades, mainstream scientific concept considers glial scar as a 'physical barrier' to impede axonal regeneration after SCI. Moreover, some extracellular molecules produced by glial scar are also regarded as axonal growth inhibitors. With the development of technology and the progress of research, multiple lines of new evidence challenge the pre-existing traditional notions in SCI repair, including the role of glial scar. This review briefly reviewed the history, advance, and controversy of glial scar research in SCI repair since 1930s, hoping to recognize the roles of glial scar and crack the international problem of SCI regeneration.

Topological remodeling of cortical perineuronal nets in focal cerebral ischemia and mild hypoperfusion

Despite the crucial role of perineuronal nets (PNNs) in neural plasticity and neurological disorders, their ultrastructural organization remains largely unresolved. We have developed a novel approach combining superresolution structured illumination microscopy (SR-SIM) and mathematical reconstruction that allows for quantitative analysis of PNN topology. Since perineuronal matrix is capable to restrict neural plasticity but at the same time is necessary to maintain synapses, we hypothesized that a beneficial post stroke recovery requires a reversible loosening of PNNs. Our results indicated that focal cerebral ischemia induces partial depletion of PNNs and that mild hypoperfusion not associated with ischemic injury can induce ultra-structural rearrangements in visually intact meshworks. In line with the activation of neural plasticity under mild stress stimuli, we provide evidence that topological conversion of PNNs can support post stroke neural rewiring.

Decoding fibrosis: Mechanisms and translational aspects

Fibrosis, a complex process of abnormal tissue healing which inevitably leads to loss of physiological organ structure and function, is a worldwide leading cause of death. Despite a large body of research over the last two decades, antifibrotic approaches are mainly limited to organ replacement therapy generating high costs of medical care. In this translational issue, a unique group of basic and clinical researchers provide meaningful answers to a desperate call of society for effective antifibrotic treatments. Fortunately, a plethora of novel fibrogenic factors and biomarkers has been identified. Noninvasive diagnostic methods and drug delivery systems have been recently developed for the management of fibrosis. Consequently, a large number of exciting clinical trials addressing comprehensive, organ and stage-specific mechanisms of fibrogenesis are ongoing. By critically addressing previously unsuccessful and novel promising therapeutic strategies, we aim to spread hope for future treatments of the various forms of organ fibrosis.