Nervous system proteoglycans as modulators of neurite outgrowth

Recovery of Post-Stroke Spatial Memory and Thalamocortical Connectivity Following Novel Glycomimetic and rhBDNF Treatment

Stroke-induced cognitive impairments remain of significant concern, with very few treatment options available. The involvement of glycosaminoglycans in neuroregenerative processes is becoming better understood and recent advancements in technology have allowed for cost-effective synthesis of novel glycomimetics. The current study evaluated the therapeutic potential of two novel glycomimetics, compound A and G, when administered systemically five-days post-photothrombotic stroke to the PFC. As glycosaminoglycans are thought to facilitate growth factor function, we also investigated the combination of our glycomimetics with intracerebral, recombinant human brain-derived neurotrophic factor (rhBDNF). C56BL/6J mice received sham or stroke surgery and experimental treatment (day-5), before undergoing the object location recognition task (OLRT). Four-weeks post-surgery, animals received prelimbic injections of the retrograde tracer cholera toxin B (CTB), before tissue was collected for quantification of thalamo-PFC connectivity and reactive astrogliosis. Compound A or G treatment alone modulated a degree of reactive astrogliosis yet did not influence spatial memory performance. Contrastingly, compound G+rhBDNF treatment significantly improved spatial memory, dampened reactive astrogliosis and limited stroke-induced loss of connectivity between the PFC and midline thalamus. As rhBDNF treatment had negligible effects, these findings support compound A acted synergistically to enhance rhBDNF to restrict secondary degeneration and facilitate functional recovery after PFC stroke.

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.

Central versus peripheral nervous system regeneration: is there an exception for cranial nerves?

There exists a dichotomy in regenerative capacity between the PNS and CNS, which poses the question - where do cranial nerves fall? Through the discussion of the various cells and processes involved in axonal regeneration, we will evaluate whether the assumption that cranial nerve regeneration is analogous to peripheral nerve regeneration is valid. It is evident from this review that much remains to be clarified regarding both PNS and CNS regeneration. Furthermore, it is not clear if cranial nerves follow the PNS model, CNS model or possess an alternative novel regenerative process altogether. Future research should continue to focus on elucidating how cranial nerves regenerate; and the various cellular interactions, molecules and pathways involved.

Heparan sulfate in human cutaneous Meissner's and Pacinian corpuscles

Heparan sulfate proteoglycans are pericellular/cell surface molecules involved in somatosensory axon guidance in the peripheral nervous system. However, the distribution of heparan sulfate proteoglycans in the extracellular matrix of human cutaneous sensory corpuscles is unknown. Immunohistochemistry and immunofluorescence assays were performed to define the localization of heparan sulfate proteoglycans in human cutaneous Meissner's and Pacinian corpuscles using two anti-heparan sulfate antibodies together with anti-S100 protein, anti-PGP9.5, anti-CD34 (to immunolabel basement membranes, Schwann cells, axon and the intermediate endoneurial layer of Pacinian corpuscles, respectively), anti-Type IV collagen, and anti-chondroitin sulfate antibodies. Heparan sulfate proteoglycans were colocalized with Type IV collagen in Meissner's corpuscles and were located in the outer core lamellae and capsule, but not in the inner core or the intermediate layer, in Pacinian corpuscles. Chondroitin sulfate was observed in the intermediate layer of Pacinian corpuscles but was never colocalized with heparan sulfate proteoglycans. The present results strongly suggest that heparan sulfate proteoglycans are associated with the basement membranes of the lamellar cells in Meissner's corpuscles and with the complex outer core capsule in Pacinian corpuscles. The functional significance of these results, if any, remains to be elucidated.

Neuroprotective Effects of Combined Treatment with Minocycline and Olfactory Ensheathing Cells Transplantation against Inflammation and Oxidative Stress after Spinal Cord Injury

Objective

Traumatic spinal cord injury (SCI) is considered one of the most devastating injuries leading to neuronal disruption. Olfactory ensheathing cells (OECs) and minocycline have been shown to promote locomotor function after spinal cord injury. In this study, we have tested the efficacy of combined treatment with minocycline and OECs after contusive spinal cord injury.

Materials and Methods

In this experimental study, adult female Wistar rats were randomly divided into five groups. Rats received an intraperitoneal injection of minocycline immediately after SCI, and then 24 hours after the injury. Transplantations were performed 7 days after the injury. Functional recovery was evaluated using the Basso, Beattie and Bresnahan scale (BBB). After that, the animals were sacrificed, and T11 segment of the spinal cord was removed after 5 weeks, and then used for histopathological, immunohistochemical, and biochemical assessments. Western blot analysis was applied to determine the protein expression of tumor necrosis factor alpha (TNF-α), interleukin 1 beta (IL1β) and caspase3.

Results

The results of this study showed that the combination of OECs graft and minocycline reduced the functional deficits and diminished cavitation and astrogliosis in spinal tissue. The analysis of protein expression by western blotting revealed that minocycline treatment along with OECs transplantation further decreased the level of IL-1β, TNF-α, caspase-3, and the oxidative stress as compared with when minocycline or OECs transplantation was used alone.

Conclusion

The combinatory treatment with OECs graft and minocycline induced a more effective response to the repair of spinal cord injury, and it is considered a therapeutic potential for the treatment of SCI.

Micropatterned biodegradable polyesters clicked with CQAASIKVAV promote cell alignment, directional migration, and neurite outgrowth

The interplay of microstructures and biological cues is critical to regulate the behaviors of Schwann cells (SCs) in terms of cellular spatial arrangement and directional migration as well as neurite orientation for bridging the proximal and distal stumps of the injured peripheral nervous system. In this study, stripe micropatterns having ridges/grooves of width 20/20 and 20/40 μm were fabricated on the surface of maleimide-functionalized biodegradable poly(ester carbonate) (P(LLA-MTMC)) films by the polydimethylsiloxane mold-pressing method, respectively. The laminin-derived CQAASIKVAV peptides end-capped with an SH group were then grafted by the thiol-ene click reaction under mild conditions to obtain micropatterned and peptide-grafted films. SCs cultured on these films, especially on the 20/40-μm film, displayed faster and aligned adhesion as well as a larger number of elongated cells with a higher length-to-width (L/W) ratio along the stripe direction than those on the flat-pep film. The migration rate of SCs was significantly enhanced in parallel to the stripe direction with a large net displacement. The micropatterned and peptide-grafted films, especially the 20/40-μm film, could promote SC proliferation and nerve growth factor (NGF) secretion in a manner similar to that of the peptide-grafted planar film. Moreover, the neurites of rat pheochromocytoma 12 (PC12) cells sprouted along the ridges with a longer average length on the micropatterned and peptide-grafted films. The synergistic effect of physical patterns and biological cues was evaluated by considering the results of cell adhesion force; immunofluorescence staining of vinculin; fluorescence staining of F-actin and the nucleus; as well as gene expression of neural cadherin (NCAD), neurocan (NCAN), and myelin protein zero (P0).

STATEMENT OF SIGNIFICANCE

The interplay of microstructures and biological cues is critical to regulate the behaviors of Schwann cells (SCs) and nerve cells, and thereby the regeneration of peripheral nerve system. In this study, the combined micropatterning and CQAASIKVAV grafting endowed the modified P(LLA-MTMC) films with both contact guidance and bioactive chemical cues to enhance cell proliferation, directional alignment and migration, longer net displacement and larger NGF secretion, and stronger neurite outgrowth of SCs and PC12 cells. Hence, the integration of physical micropatterns and bioactive molecules is an effective way to obtain featured biomaterials for the regeneration of nerves and other types of tissues.

Exploring Optic Nerve Axon Regeneration

Background:

Traumatic optic nerve injury is a leading cause of irreversible blindness across the world and causes progressive visual impairment attributed to the dysfunction and death of retinal ganglion cells (RGCs). To date, neither pharmacological nor surgical interventions are sufficient to halt or reverse the progress of visual loss. Axon regeneration is critical for functional recovery of vision following optic nerve injury. After optic nerve injury, RGC axons usually fail to regrow and die, leading to the death of the RGCs and subsequently inducing the functional loss of vision. However, the detailed molecular mechanisms underlying axon regeneration after optic nerve injury remain poorly understood.

Methods:

Research content related to the detailed molecular mechanisms underlying axon regeneration after optic nerve injury have been reviewed.

Results:

The present review provides an overview of regarding potential strategies for axonal regeneration of RGCs and optic nerve repair, focusing on the role of cytokines and their downstream signaling pathways involved in intrinsic growth program and the inhibitory environment together with axon guidance cues for correct axon guidance. A more complete understanding of the factors limiting axonal regeneration will provide a rational basis, which contributes to develop improved treatments for optic nerve regeneration. These findings are encouraging and open the possibility that clinically meaningful regeneration may become achievable in the future.

Conclusion:

Combination of treatments towards overcoming growth-inhibitory molecules and enhancing intrinsic growth capacity combined with correct guidance using axon guidance cues is crucial for developing promising therapies to promote axon regeneration and functional recovery after ON injury.

Conditioned Medium of Human Adipose Mesenchymal Stem Cells Increases Wound Closure and Protects Human Astrocytes Following Scratch Assay In Vitro

Astrocytes perform essential functions in the preservation of neural tissue. For this reason, these cells can respond with changes in gene expression, hypertrophy, and proliferation upon a traumatic brain injury event (TBI). Different therapeutic strategies may be focused on preserving astrocyte functions and favor a non-generalized and non-sustained protective response over time post-injury. A recent strategy has been the use of the conditioned medium of human adipose mesenchymal stem cells (CM-hMSCA) as a therapeutic strategy for the treatment of various neuropathologies. However, although there is a lot of information about its effect on neuronal protection, studies on astrocytes are scarce and its specific action in glial cells is not well explored. In the present study, the effects of CM-hMSCA on human astrocytes subjected to scratch assay were assessed. Our findings indicated that CM-hMSCA improved cell viability, reduced nuclear fragmentation, and preserved mitochondrial membrane potential. These effects were accompanied by morphological changes and an increased polarity index thus reflecting the ability of astrocytes to migrate to the wound stimulated by CM-hMSCA. In conclusion, CM-hMSCA may be considered as a promising therapeutic strategy for the protection of astrocyte function in brain pathologies.

Sulfation of Glycosaminoglycans and Its Implications in Human Health and Disorders

Sulfation is a dynamic and complex posttranslational modification process. It can occur at various positions within the glycosaminoglycan (GAG) backbone and modulates extracellular signals such as cell-cell and cell-matrix interactions; different sulfation patterns have been identified for the same organs and cells during their development. Because of their high specificity in relation to function, GAG sulfation patterns are referred to as the sulfation code. This review explores the role of GAG sulfation in different biological processes at the cell, tissue, and organism levels. We address the connection between the sulfation patterns of GAGs and several physiological processes and discuss the misregulation of GAG sulfation and its involvement in several genetic and metabolic disorders. Finally, we present the therapeutic potential of GAGs and their synthetic mimics in the biomedical field.

The natural product 4,10-aromadendranediol induces neuritogenesis in neuronal cells in vitro through activation of the ERK pathway

Recent studies focus on promoting neurite outgrowth to remodel the central nervous network after brain injury. Currently, however, there are few drugs treating brain diseases in the clinic by enhancing neurite outgrowth. In this study, we established an NGF-induced PC12 differentiation model to screen novel compounds that have the potential to induce neuronal differentiation, and further characterized 4,10-Aromadendranediol (ARDD) isolated from the dried twigs of the Baccharis gaudichaudiana plant, which exhibited the capability of promoting neurite outgrowth in neuronal cells in vitro. ARDD (1, 10 μmol/L) significantly enhanced neurite outgrowth in NGF-treated PC12 cells and N1E115 cells in a time-dependent manner. In cultured primary cortical neurons, ARDD (5, 10 μmol/L) not only significantly increased neurite outgrowth but also increased the number of neurites on the soma and the number of bifurcations. Further analyses showed that ARDD (10 μmol/L) significantly increased the phosphorylation of ERK1/2 and the downstream GSK-3β, subsequently induced β-catenin expression and up-regulated the gene expression of the Wnt ligands Fzd1 and Wnt3a in neuronal cells. The neurite outgrowth-promoting effect of ARDD in neuronal cells was abolished by pretreatment with the specific ERK1/2 inhibitor PD98059, but was partially reversed by XAV939, an inhibitor of the Wnt/β-catenin pathway. ARDD also increased the expression of BDNF, CREB and GAP-43 in N1E115 cells, which was reversed by pretreatment with PD98059. In N1E115 cells subjected to oxygen and glucose deprivation (OGD), pretreatment with ARDD (1-10 μmol/L) significantly enhanced the phosphorylation of ERK1/2 and induced neurite outgrowth. These results demonstrated that the natural product ARDD exhibits neurite outgrowth-inducing activity in neurons via activation of the ERK signaling pathway, which may be beneficial to the treatment of brain diseases.

Lanthionine ketimine ester promotes locomotor recovery after spinal cord injury by reducing neuroinflammation and promoting axon growth

The mammalian central nervous system (CNS) has limited regenerative ability after injury, largely due to scar formation and axonal growth inhibitors. Experimental suppression of neuroinflammation encourages recovery from spinal cord injury (SCI), yet practical means for pharmacologically treating SCI have remained elusive. Lanthionine ketimine (LK) is a natural brain sulfur amino acid metabolite with demonstrated anti-neuroinflammatory and neurotrophic activities. LK and its synthetic brain-penetrating ethyl ester (LKE) promote growth factor-dependent neurite extension in cultured cell and suppress microglial activation in animal models of neurodegeneration. Thus far however, LKE has not been explored as a potential therapy for SCI. The present study investigated the hypothesis that systemic LKE could improve motor functional recovery after SCI in a mouse model. Intraperitoneal administration of LKE (100 mg/kg/d) after near-complete transect of spinal cord at the T7 level significantly improved motor function over a 4-week time course. Vehicle-treated mice, in contrast, demonstrated negligible functional recovery. In terms of histology, LKE treatment reduced pro-neuroinflammatory microglia/macrophage activation evidenced by quantitative Iba1 labeling and shifted the microglial phenotype toward a more neurotrophic M2 character evidenced by changes in the M2 marker arginase-1. This was correlated with less dense scar formation and more extensive axonal regrowth across the transection site demonstrated by 5-hydroxytryptamine (5HT) immunolabeling of raphespinal tract axons. These data provide evidence that LKE or similar compounds have potential therapeutic value for recovery after certain forms of SCI.

Differential Effects of Coating Materials on Viability and Migration of Schwann Cells

Synthetic nerve conduits have emerged as an alternative to guide axonal regeneration in peripheral nerve gap injuries. Migration of Schwann cells (SC) from nerve stumps has been demonstrated as one essential factor for nerve regeneration in nerve defects. In this experiment, SC viability and migration were investigated for various materials to determine the optimal conditions for nerve regeneration. Cell viability and SC migration assays were conducted for collagen I, laminin, fibronectin, lysine and ornithine. The highest values for cell viability were detected for collagen I, whereas fibronectin was most stimulatory for SC migration. At this time, clinically approved conduits are based on single-material structures. In contrast, the results of this experiment suggest that material compounds such as collagen I in conjunction with fibronectin should be considered for optimal nerve healing.

Scanning electron microscopy of chronically implanted intracortical microelectrode arrays in non-human primates

OBJECTIVE

Signal attenuation is a major problem facing intracortical sensors for chronic neuroprosthetic applications. Many studies suggest that failure is due to gliosis around the electrode tips, however, mechanical and material causes of failure are often overlooked. The purpose of this study was to investigate the factors contributing to progressive signal decline by using scanning electron microscopy (SEM) to visualize structural changes in chronically implanted arrays and histology to examine the tissue response at corresponding implant sites.

APPROACH

We examined eight chronically implanted intracortical microelectrode arrays (MEAs) explanted from non-human primates at times ranging from 37 to 1051 days post-implant. We used SEM, in vivo neural recordings, and histology (GFAP, Iba-1, NeuN). Three MEAs that were never implanted were also imaged as controls.

MAIN RESULTS

SEM revealed progressive corrosion of the platinum electrode tips and changes to the underlying silicon. The parylene insulation was prone to cracking and delamination, and in some instances the silicone elastomer also delaminated from the edges of the MEA. Substantial tissue encapsulation was observed and was often seen growing into defects in the platinum and parylene. These material defects became more common as the time in vivo increased. Histology at 37 and 1051 days post-implant showed gliosis, disruption of normal cortical architecture with minimal neuronal loss, and high Iba-1 reactivity, especially within the arachnoid and dura. Electrode tracts were either absent or barely visible in the cortex at 1051 days, but were seen in the fibrotic encapsulation material suggesting that the MEAs were lifted out of the brain. Neural recordings showed a progressive drop in impedance, signal amplitude, and viable channels over time.

SIGNIFICANCE

These results provide evidence that signal loss in MEAs is truly multifactorial. Gliosis occurs in the first few months after implantation but does not prevent useful recordings for several years. Progressive meningeal fibrosis encapsulates and lifts MEAs out of the cortex while ongoing foreign body reactions lead to progressive degradation of the materials. Long-term impedance drops are due to the corrosion of platinum, cracking and delamination of parylene, and delamination of silicone elastomer. Oxygen radicals released by cells of the immune system likely mediate the degradation of these materials. Future MEA designs must address these problems through more durable insulation materials, more inert electrode alloys, and pharmacologic suppression of fibroblasts and leukocytes.

Genome-wide association studies in pharmacogenomics of antidepressants

Major depressive disorder (MDD) is one of the most common psychiatric disorders worldwide. Doctors must prescribe antidepressants based on educated guesses due to the fact that it is unmanageable to predict the effectiveness of any particular antidepressant in an individual patient. With the recent advent of scientific research, the genome-wide association study (GWAS) is extensively employed to analyze hundreds of thousands of single nucleotide polymorphisms by high-throughput genotyping technologies. In addition to the candidate-gene approach, the GWAS approach has recently been utilized to investigate the determinants of antidepressant response to therapy. In this study, we reviewed GWAS studies, their limitations and future directions with respect to the pharmacogenomics of antidepressants in MDD.

Chondroitin Sulfate Glycosaminoglycan Hydrogels Create Endogenous Niches for Neural Stem Cells

Neural stem cells (NSCs) possess great potential for neural tissue repair after traumatic injuries to the central nervous system (CNS). However, poor survival and self-renewal of NSCs after injury severely limits its therapeutic potential. Sulfated chondroitin sulfate glycosaminoglycans (CS-GAGs) linked to CS proteoglycans (CSPGs) in the brain extracellular matrix (ECM) have the ability to bind and potentiate trophic factor efficacy, and promote NSC self-renewal in vivo. In this study, we investigated the potential of CS-GAG hydrogels composed of monosulfated CS-4 (CS-A), CS-6 (CS-C), and disulfated CS-4,6 (CS-E) CS-GAGs as NSC carriers, and their ability to create endogenous niches by enriching specific trophic factors to support NSC self-renewal. We demonstrate that CS-GAG hydrogel scaffolds showed minimal swelling and degradation over a period of 15 days in vitro, absorbing only 6.5 ± 0.019% of their initial weight, and showing no significant loss of mass during this period. Trophic factors FGF-2, BDNF, and IL10 bound with high affinity to CS-GAGs, and were significantly (p < 0.05) enriched in CS-GAG hydrogels when compared to unsulfated hyaluronic acid (HA) hydrogels. Dissociated rat subventricular zone (SVZ) NSCs when encapsulated in CS-GAG hydrogels demonstrated ∼88.5 ± 6.1% cell viability in vitro. Finally, rat neurospheres in CS-GAG hydrogels conditioned with the mitogen FGF-2 demonstrated significantly (p < 0.05) higher self-renewal when compared to neurospheres cultured in unconditioned hydrogels. Taken together, these findings demonstrate the ability of CS-GAG based hydrogels to regulate NSC self-renewal, and facilitate growth factor enrichment locally.

Sulf1 and Sulf2 Differentially Modulate Heparan Sulfate Proteoglycan Sulfation during Postnatal Cerebellum Development: Evidence for Neuroprotective and Neurite Outgrowth Promoting Functions

Introduction

Sulf1 and Sulf2 are cell surface sulfatases, which remove specific 6-O-sulfate groups from heparan sulfate (HS) proteoglycans, resulting in modulation of various HS-dependent signaling pathways. Both Sulf1 and Sulf2 knockout mice show impairments in brain development and neurite outgrowth deficits in neurons.

Methodology and Main Findings

To analyze the molecular mechanisms behind these impairments we focused on the postnatal cerebellum, whose development is mainly characterized by proliferation, migration, and neurite outgrowth processes of precursor neurons. Primary cerebellar granule cells isolated from Sulf1 or Sulf2 deficient newborns are characterized by a reduction in neurite length and cell survival. Furthermore, Sulf1 deficiency leads to a reduced migration capacity. The observed impairments in cell survival and neurite outgrowth could be correlated to Sulf-specific interference with signaling pathways, as shown for FGF2, GDNF and NGF. In contrast, signaling of Shh, which determines the laminar organization of the cerebellar cortex, was not influenced in either Sulf1 or Sulf2 knockouts. Biochemical analysis of cerebellar HS demonstrated, for the first time in vivo, Sulf-specific changes of 6-O-, 2-O- and N-sulfation in the knockouts. Changes of a particular HS epitope were found on the surface of Sulf2-deficient cerebellar neurons. This epitope showed a restricted localization to the inner half of the external granular layer of the postnatal cerebellum, where precursor cells undergo final maturation to form synaptic contacts.

Conclusion

Sulfs introduce dynamic changes in HS proteoglycan sulfation patterns of the postnatal cerebellum, thereby orchestrating fundamental mechanisms underlying brain development.

Neurotrophic factor-α1 modulates NGF-induced neurite outgrowth through interaction with Wnt-3a and Wnt-5a in PC12 cells and cortical neurons

Wnt-3a and Wnt-5a signaling activities inhibit and promote neurite outgrowth, respectively, to regulate dendritic and axonal genesis during neurodevelopment. NF-α1, a neurotrophic factor, has been shown to modulate dendritic remodeling and negatively regulate the canonical Wnt-3a pathway. Here, we investigated whether NF-α1 could modify nerve growth factor (NGF)-induced neurite outgrowth through interaction with Wnt-3a and Wnt-5a in PC12 cells and mouse primary cortical neurons. We showed that NGF-induced neurite outgrowth was inhibited by Wnt-3a, and this inhibition was prevented by NF-α1. Western blot analysis revealed that NF-α1 reduced the expression of both β-catenin in the canonical Wnt-3a pathway and Rho, a downstream effector of Wnt-3a's non-canonical signaling pathway. Treatment of PC12 cells with a ROCK inhibitor prevented the inhibition of NGF-induced neurite outgrowth by Wnt-3a, suggesting that NF-α1 promotes neurite outgrowth in the presence of Wnt-3a by down-regulating its canonical and non-canonical activities. Interestingly, treatment of PC12 cells with Wnt-5a, which formed a complex with NF-α1, induced neurite outgrowth that was enhanced by treatment with the combination of Wnt-5a, NGF, and NF-α1. These effects of NF-α1 on Wnt 3a's and Wnt 5a's regulation of neurite outgrowth in PC12 cells were also demonstrated in primary cultures of mouse cortical neurons. In addition, we showed in PC12 cells that NF-α1 acts by upregulating adenomatous polyposis coli (APC) accumulation at neurite tips, thereby providing positive and negative Wnt-3a/Wnt-5a mediated cues to modulate neurite outgrowth, a process important during neurodevelopment.

A review of organic and inorganic biomaterials for neural interfaces

Recent advances in nanotechnology have generated wide interest in applying nanomaterials for neural prostheses. An ideal neural interface should create seamless integration into the nervous system and performs reliably for long periods of time. As a result, many nanoscale materials not originally developed for neural interfaces become attractive candidates to detect neural signals and stimulate neurons. In this comprehensive review, an overview of state-of-the-art microelectrode technologies provided fi rst, with focus on the material properties of these microdevices. The advancements in electro active nanomaterials are then reviewed, including conducting polymers, carbon nanotubes, graphene, silicon nanowires, and hybrid organic-inorganic nanomaterials, for neural recording, stimulation, and growth. Finally, technical and scientific challenges are discussed regarding biocompatibility, mechanical mismatch, and electrical properties faced by these nanomaterials for the development of long-lasting functional neural interfaces.

Extracellular matrix components mark the territories of circumventricular organs

In the central nervous system the extracellular matrix has important roles, e.g. supporting the extracellular space, controlling the tissue hydration, binding soluble factors and influencing their diffusion. The distribution of the extracellular matrix components in the brain has been mapped but data on the circumventricular organs (CVOs) is not available yet. The CVOs lack the blood-brain barrier and have relatively large perivascular spaces. The present study investigates tenascin-R and the lecticans: aggrecan, brevican, neurocan, and versican in the median eminence, the area postrema, the vascular organ of the lamina terminalis, the subfornical organ, the pineal body and the subcommissural organ of the rat applying immunohistochemical methods, and lectin histochemistry, using Wisteria floribunda agglutinin (WFA). The extracellular matrix components were found intensely expressed in the CVOs with two exceptions: aggrecan immunoreactivity visualized only neurons in the arcuate nucleus, and the subcommissural organ was not labeled with either WFA, or lecticans, or tenascin-R. The different labelings usually overlapped each other. The distribution of the extracellular matrix components marked the territories of the CVOs. Considering these we suppose that the extracellular matrix is essential in the maintenance of CVO functions providing the large extracellular space which is required for diffusion and other processes important in their chemosensitive and neurosecretory activities. The decrease of extracellular matrix beyond the border of the organs may contribute to the control of the diffusion of molecules from the CVOs into the surrounding brain substance.

Traffic lights for axon growth: proteoglycans and their neuronal receptors

Axon growth is a central event in the development and post-injury plasticity of the nervous system. Growing axons encounter a wide variety of environmental instructions. Much like traffic lights in controlling the migrating axons, chondroitin sulfate proteoglycans (CSPGs) and heparan sulfate proteoglycans (HSPGs) often lead to "stop" and "go" growth responses in the axons, respectively. Recently, the LAR family and NgR family molecules were identified as neuronal receptors for CSPGs and HSPGs. These discoveries provided molecular tools for further study of mechanisms underlying axon growth regulation. More importantly, the identification of these proteoglycan receptors offered potential therapeutic targets for promoting post-injury axon regeneration.

Arylsulfatase B modulates neurite outgrowth via astrocyte chondroitin-4-sulfate: dysregulation by ethanol

In utero ethanol exposure causes fetal alcohol spectrum disorders, associated with reduced brain plasticity; the mechanisms of these effects are not well understood, particularly with respect to glial involvement. Astrocytes release factors that modulate neurite outgrowth. We explored the hypothesis that ethanol inhibits neurite outgrowth by increasing the levels of inhibitory chondroitin sulfate proteoglycans (CSPGs) in astrocytes. Astrocyte treatment with ethanol inhibited the activity of arylsulfatase B (ARSB), the enzyme that removes sulfate groups from chondroitin-4-sulfate (C4S) and triggers the degradation of C4S, increased total sulfated glycosaminoglycans (GAGs), C4S, and neurocan core-protein content and inhibited neurite outgrowth in neurons cocultured with ethanol-treated astrocytes in vitro, effects reversed by treatment with recombinant ARSB. Ethanol also inhibited ARSB activity and increased sulfate GAG and neurocan levels in the developing hippocampus after in vivo ethanol exposure. ARSB silencing increased the levels of sulfated GAGs, C4S, and neurocan in astrocytes and inhibited neurite outgrowth in cocultured neurons, indicating that ARSB activity directly regulates C4S and affects neurocan expression. In summary, this study reports two major findings: ARSB modulates sulfated GAG and neurocan levels in astrocytes and astrocyte-mediated neurite outgrowth in cocultured neurons; and ethanol inhibits the activity of ARSB, increases sulfated GAG, C4S, and neurocan levels, and thereby inhibits astrocyte-mediated neurite outgrowth. An unscheduled increase in CSPGs in the developing brain may lead to altered brain connectivity and to premature decrease in neuronal plasticity and therefore represents a novel mechanism by which ethanol can exert its neurodevelopmental effects.

Down-regulation of Nogo-A by collagen scaffolds impregnated with bone marrow stromal cell treatment after traumatic brain injury promotes axonal regeneration in rats

Nogo-A is a major form of growth inhibitory molecule (growth-IM) which inhibits axonal regeneration and neurite regrowth after neural injury. Bone marrow stromal cells (MSCs) have been shown to inhibit Nogo-A expression in vitro and in cerebral ischemic animal models. The present study was designed to investigate the effects of treatment with human MSCs (hMSCs) impregnated into collagen scaffolds on the expression of Nogo-A and axonal plasticity after traumatic brain injury (TBI). Adult male Wistar rats were injured with controlled cortical impact and treated either with saline, hMSCs-alone or hMSCs impregnated into collagen scaffolds (scaffold+hMSC) transplanted into the lesion cavity 7 days after TBI. Rats were sacrificed 14 days after TBI and brain tissues were harvested for immunohistochemical studies, Western blot analysis, laser capture microdissections and qRT-PCR to evaluate axonal density and Nogo-A protein and gene expressions. Our data showed that treatment of TBI with scaffold+hMSC significantly decreased TBI-induced Nogo-A protein expression and increased axonal density compared to saline and hMSC-alone treatments. In addition, scaffold+hMSC transplantation decreased Nogo-A transcription in oligodendrocytes after TBI. Scaffold+hMSC treatment was superior to hMSC-alone treatment in suppressing Nogo-A expression and enhancing axonal regeneration after TBI. Our data suggest that transplanting hMSCs with scaffolds down-regulates Nogo-A transcription and protein expression which may partially contribute to the enhanced axonal regeneration after TBI.

Epiphycan from salmon nasal cartilage is a novel type of large leucine-rich proteoglycan

Chum salmon (Oncorhynchus keta) nasal cartilage was examined by next-generation DNA sequencing and mass spectrometric analyses, and 14 types of proteoglycans including epiphycan (EPY) were found. A cDNA encoding EPY was cloned and sequenced. The cDNA encoded 589 amino acids comprised a glycosaminoglycan (GAG) domain containing 55 potential GAG-modified sites (Ser-Gly and/or Gly-Ser), a cysteine cluster and 6 leucine-rich repeats. EPY was purified from salmon nasal cartilage and the structure of the GAG was characterized. As a result of unsaturated disaccharide analysis, GAG was found to be composed of chondroitin 6-sulfate (58.0%), chondroitin 4-sulfate (26.5%) and non-sulfated chondroitin (15.3%). The average molecular weight of GAG was estimated to be 3.0 × 10(4). Ser-100 and Ser-103 were identified as serine residues substituted by GAG chains by chemical modification and mass spectrometric analysis. More than 50 serine residues were assumed to be substituted by GAG chains. EPY is heavily substituted by chondroitin sulfate, giving an overall molecular weight of just under 2 × 10(6). EPY from salmon nasal cartilage is a novel type of large leucine-rich proteoglycan.

Genome-wide scan of job-related exhaustion with three replication studies implicate a susceptibility variant at the UST gene locus

Job-related exhaustion is the core dimension of burnout, a work-related stress syndrome that has several negative health consequences. In this study, we explored the molecular genetic background of job-related exhaustion. A genome-wide analysis of job-related exhaustion was performed in the GENMETS subcohort (n = 1256) of the Finnish population-based Health 2000 study. Replication analyses included an analysis of the strongest associations in the rest of the Health 2000 sample (n = 1660 workers) and in three independent populations (the FINRISK population cohort, n = 10 753; two occupational cohorts, total n = 1451). Job-related exhaustion was ascertained using a standard self-administered questionnaire (the Maslach Burnout Inventory (MBI)-GS exhaustion scale in the Health 2000 sample and the occupational cohorts) or a single question (FINRISK). A variant located in an intron of UST, uronyl-2-sulfotransferase (rs13219957), gave the strongest statistical evidence in the initial genome-wide study (P = 1.55 × 10(-7)), and was associated with job-related exhaustion in all the replication sets (P < 0.05; P = 6.75 × 10(-7) from the meta-analysis). Consistent with studies of mood disorders, individual common genetic variants did not have any strong effect on job-related exhaustion. However, the nominally significant signals from the allelic variant of UST in four separate samples suggest that this variant might be a weak risk factor for job-related exhaustion. Together with the previously reported associations of other dermatan/chondroitin sulfate genes with mood disorders, these results indicate a potential molecular pathway for stress-related traits and mark a candidate region for further studies of job-related and general exhaustion.

Structural plasticity in the dentate gyrus- revisiting a classic injury model

The adult brain is in a continuous state of remodeling. This is nowhere more true than in the dentate gyrus, where competing forces such as neurodegeneration and neurogenesis dynamically modify neuronal connectivity, and can occur simultaneously. This plasticity of the adult nervous system is particularly important in the context of traumatic brain injury or deafferentation. In this review, we summarize a classic injury model, lesioning of the perforant path, which removes the main extrahippocampal input to the dentate gyrus. Early studies revealed that in response to deafferentation, axons of remaining fiber systems and dendrites of mature granule cells undergo lamina-specific changes, providing one of the first examples of structural plasticity in the adult brain. Given the increasing role of adult-generated new neurons in the function of the dentate gyrus, we also compare the response of newborn and mature granule cells following lesioning of the perforant path. These studies provide insights not only to plasticity in the dentate gyrus, but also to the response of neural circuits to brain injury.

Corneal sulfated glycosaminoglycans and their effects on trigeminal nerve growth cone behavior in vitro: roles for ECM in cornea innervation

PURPOSE

Sensory trigeminal nerve growth cones innervate the cornea in a highly coordinated fashion. The purpose of this study was to determine if extracellular matrix glycosaminoglycans (ECM-GAGs), including keratan sulfate (KS), dermatan sulfate (DS), and chondroitin sulfate A (CSA) and C (CSC), polymerized in developing eyefronts, may provide guidance cues to nerves during cornea innervation.

METHODS

Immunostaining using antineuron-specific-β-tubulin and monoclonal antibodies for KS, DS, and CSA/C was performed on eyefronts from embryonic day (E) 9 to E14 and staining visualized by confocal microscopy. Effects of purified GAGs on trigeminal nerve growth cone behavior were tested using in vitro neuronal explant cultures.

RESULTS

At E9 to E10, nerves exiting the pericorneal nerve ring grew as tight fascicles, advancing straight toward the corneal stroma. In contrast, upon entering the stroma, nerves bifurcated repeatedly as they extended anteriorly toward the epithelium. KS was localized in the path of trigeminal nerves, whereas DS and CSA/C-rich areas were avoided by growth cones. When E10 trigeminal neurons were cultured on different substrates comprised of purified GAG molecules, their neurite growth cone behavior varied depending on GAG type, concentration, and mode of presentation (immobilized versus soluble). High concentrations of immobilized KS, DS, and CSA/C inhibited neurite growth to varying degrees. Neurites traversing lower, permissive concentrations of immobilized DS and CSA/C displayed increased fasciculation and decreased branching, whereas KS caused decreased fasciculation and increased branching. Enzymatic digestion of sulfated GAGs canceled their effects on trigeminal neurons.

CONCLUSIONS

Data herein suggest that GAGs may direct the movement of trigeminal nerve growth cones innervating the cornea.

Cooperative effect of heparan sulfate and laminin mimetic peptide nanofibers on the promotion of neurite outgrowth

Extracellular matrix contains an abundant variety of signals that are received by cell surface receptors contributing to cell fate, via regulation of cellular activities such as proliferation, migration and differentiation. Cues from extracellular matrix can be used for the development of materials to direct cells into their desired fate. Neural extracellular matrix (ECM) is rich in axonal growth inducer proteins, and by mimicking these permissive elements in the cellular environment, neural differentiation as well as neurite outgrowth can be induced. In this paper, we used a synthetic peptide nanofiber system that can mimic not only the activity of laminin, an axonal growth-promoting constituent of the neural ECM, but also the activity of heparan sulfate proteoglycans in order to induce neuritogenesis. Heparan sulfate mimetic groups that were utilized in our system have an affinity to growth factors and induce the neuroregenerative effect of laminin mimetic peptide nanofibers. The self-assembled peptide nanofibers with heparan sulfate mimetic and laminin-derived epitopes significantly promoted neurite outgrowth by PC-12 cells. In addition, these scaffolds were even effective in the presence of chondroitin sulfate proteoglycans (CSPGs), which are the major inhibitory components of the central nervous system. In the presence of these nanofibers, cells could overcome CSPG inhibitory effect and extend neurites on peptide nanofiber scaffolds.

Four steps to optic nerve regeneration

The failure of the optic nerve to regenerate after injury or in neurodegenerative disease remains a major clinical and scientific problem. Retinal ganglion cell (RGC) axons course through the optic nerve and carry all the visual information to the brain, but after injury, they fail to regrow through the optic nerve and RGC cell bodies typically die, leading to permanent loss of vision. There are at least 4 hurdles to overcome in preserving RGCs and regenerating their axons: 1) increase RGC survival, 2) overcome the inhibitory environment of the optic nerve, 3) enhance RGC intrinsic axon growth potential, and 4) optimize the mapping of RGC connections back into their targets in the brain.

Influence of glial-derived matrix molecules, especially chondroitin sulfates, on neurite growth and survival of cultured mouse embryonic motoneurons

Mechanisms controlling neuronal survival and regeneration play an important role during development, after birth, and under lesion conditions. Isolated embryonic mouse motoneurons have been a useful tool for studying such basic mechanisms. These cultured motoneurons depend on extracellular matrix (ECM) molecules, which are potent mediators of survival and axonal growth and guidance in the CNS and in vitro, exhibiting either attractive or repellent guidance cues. Additionally, ECM proteoglycans and glycoproteins are components of the glial scar acting as a growth barrier for regenerating axons. Compared with CNS axon outgrowth, less is known about the cues that guide motoneurons toward their peripheral targets. Because we are interested in the effects of glial-derived chondroitin sulfate proteoglycans (CSPGs), we have worked out a model system for investigating the influences of glial-derived matrix molecules on motoneuron outgrowth and survival. We used cultured embryonic mouse motoneurons to investigate axon growth effects of matrix molecules produced by the glial-derived cell lines A7, Neu7, and Oli-neu primary astrocytes as well as the immortalized Schwann cell line IMS32. The results indicate that molecules of the ECM, especially chondroitin sulfates, play an important role as axon growth-promoting cues. We could demonstrate a modifying effect of the matrix components on motoneuron survival and caspase3-induced apoptosis.

Construction of tissue engineered nerve grafts and their application in peripheral nerve regeneration

Surgical repair of severe peripheral nerve injuries represents not only a pressing medical need, but also a great clinical challenge. Autologous nerve grafting remains a golden standard for bridging an extended gap in transected nerves. The formidable limitations related to this approach, however, have evoked the development of tissue engineered nerve grafts as a promising alternative to autologous nerve grafts. A tissue engineered nerve graft is typically constructed through a combination of a neural scaffold and a variety of cellular and molecular components. The initial and basic structure of the neural scaffold that serves to provide mechanical guidance and optimal environment for nerve regeneration was a single hollow nerve guidance conduit. Later there have been several improvements to the basic structure, especially introduction of physical fillers into the lumen of a hollow nerve guidance conduit. Up to now, a diverse array of biomaterials, either of natural or of synthetic origin, together with well-defined fabrication techniques, has been employed to prepare neural scaffolds with different structures and properties. Meanwhile different types of support cells and/or growth factors have been incorporated into the neural scaffold, producing unique biochemical effects on nerve regeneration and function restoration. This review attempts to summarize different nerve grafts used for peripheral nerve repair, to highlight various basic components of tissue engineered nerve grafts in terms of their structures, features, and nerve regeneration-promoting actions, and finally to discuss current clinical applications and future perspectives of tissue engineered nerve grafts.

Differential involvement of the extracellular 6-O-endosulfatases Sulf1 and Sulf2 in brain development and neuronal and behavioural plasticity

The extracellular sulfatases Sulf1 and Sulf2 remove specific 6-O-sulfate groups from heparan sulfate, thereby modulating numerous signalling pathways underlying development and homeostasis. In vitro data have suggested that the two enzymes show functional redundancy. To elucidate their in vivo functions and to further address the question of a putative redundancy, we have generated Sulf1- and Sulf2-deficient mice. Phenotypic analysis of these animals revealed higher embryonic lethality of Sulf2 knockout mice, which can be associated with neuroanatomical malformations during embryogenesis. Sulf1 seems not to be essential for developmental or postnatal viability, as mice deficient in this sulfatase show no overt phenotype. However, neurite outgrowth deficits were observed in hippocampal and cerebellar neurons of both mutant mouse lines, suggesting that not only Sulf2 but also Sulf1 function plays a role in the developing nervous system. Behavioural analysis revealed differential deficits with regard to cage activity and spatial learning for Sulf1- and Sulf2-deficient mouse lines. In addition, Sulf1-specific deficits were shown for synaptic plasticity in the CA1 region of the hippocampus, associated with a reduced spine density. These results reveal that Sulf1 and Sulf2 fulfil non-redundant functions in vivo in the development and maintenance of the murine nervous system.

Induction of perlecan expression and neural cell proliferation by FGF-2 in the developing cerebral cortex: an in vivo study

Fibroblast growth factor has been implicated in cerebral cortical cell proliferation, migration, survival and differentiation. In the nervous system, proteoglycans (PGs) modulate growth factor activities and cell proliferation. Perlecan is a large PG and is expressed during the prenatal stages of brain development. Perlecan can promote fibroblast growth factor-2 (FGF-2) activity. In this study the effects of FGF-2 on neurogenesis and perlecan expression in the cerebral cortex have been studied. FGF-2 and anti-FGF-2 antibody were administered to 1-day-old mouse pups through the cisterna magna. Two days after injection, the pups were harvested and brains were removed for further analysis. We used western blotting and immunohistochemistry in order to analyze perlecan expression and neurogenesis in the cerebral cortex. We showed that the thickness of cerebral cortex, the number of cells produced in the cerebral cortex and perlecan expression are increased in response to injection of FGF-2 and decreased in response to infusion of anti-FGF-2 antibody as compared to controls. In conclusion, the results from this study suggest that FGF-2 increases neural cell production and perlecan expression in the developing cerebral cortex. It is also concluded that FGF-2 is an important factor in the cerebral cortical development, stimulating neuronal precursor proliferation.

Modification of N-glycosylation sites allows secretion of bacterial chondroitinase ABC from mammalian cells

Although many eukaryotic proteins have been secreted by transfected bacterial cells, little is known about how a bacterial protein is treated as it passes through the secretory pathway when expressed in a eukaryotic cell. The eukaryotic N-glycosylation system could interfere with folding and secretion of prokaryotic proteins whose sequence has not been adapted for glycosylation in structurally appropriate locations. Here we show that such interference does indeed occur for chondroitinase ABC from the bacterium Proteus vulgaris, and can be overcome by eliminating potential N-glycosylation sites. Chondroitinase ABC was heavily glycosylated when expressed in mammalian cells or in a mammalian translation system, and this process prevented secretion of functional enzyme. Directed mutagenesis of selected N-glycosylation sites allowed efficient secretion of active chondroitinase. As these proteoglycans are known to inhibit regeneration of axons in the mammalian central nervous system, the modified chondroitinase gene is a potential tool for gene therapy to promote neural regeneration, ultimately in human spinal cord injury.

Determination of sulfation pattern in brain glycosaminoglycans by chip-based electrospray ionization ion trap mass spectrometry

Chondroitin sulfate (CS) and dermatan sulfate (DS) glycosaminoglycans display variability of sulfation in their constituent disaccharide repeats during chain elongation. Since a large proportion of the extracellular matrix of the central nervous system (CNS) is composed of proteoglycans, CS/DS disaccharide degree and profile of sulfation play important roles in the functional diversity of neurons, brain development, and some of its pathological states. To investigate the sulfation pattern of CS/DS structures expressed in CNS, we introduced here a novel method based on an advanced system encompassing fully automated chip nanoelectrospray ionization (nanoESI) in the negative ion mode and high capacity ion trap multistage mass spectrometry (MS(2)-MS(3)) by collision-induced dissociation (CID). This method, introduced here for the first time in glycomics of brain glycosaminoglycans, was particularly applied to structural investigation of disaccharides obtained by beta-elimination and digestion with chondroitin B and AC I lyase of hybrid CS/DS chains from wild-type mouse brain. Screening in the chip-MS mode of DS disaccharide fraction resulting after depolymerization with chondroitin B lyase revealed molecular ions assigned to monosulfated disaccharide species having a composition of 4,5-Delta-[IdoA-GalNAc]. By optimized CID MS(2)-MS(3), fragment ions supporting the localization of sulfate ester group at C4 within GalNAc were produced. Chip ESI MS profiling of CS disaccharide fraction obtained by depolymerization of the same CS/DS chain using chondroitin AC I lyase indicated the occurrence of mono- and bisulfated 4,5-Delta-[GlcA-GalNAc]. The site of oversulfation was determined by MS(2)-MS(3), which provided sequence patterns consistent with a rare GlcA-3-sulfate-GalNAc-6-sulfate structural motif. Figure Mouse brain GlcA-3-sulfate-GalNAc-6-sulfate structural motif.

Mechanisms involved in suppression of NGF-induced neuronal differentiation of PC12 cells by hyaluronic acid

In the present study, we found that hyaluronic acid (HA) suppressed the neuronal differentiation mediated by nerve growth factor (NGF). In addition, we examined the mechanism by which HA inhibits the NGF-induced neurite outgrowth of PC12 cells. We elucidated the direct interaction between NGF and HA, and found that HA did not bind to NGF directly using a quartz-crystal microbalance. Western blot analysis revealed that HA suppressed NGF-induced phosphorylation of p38 MAPK, ERKs, and transcriptional factor CREB in PC12 cells. Furthermore, HA inhibited the luciferase activity of pCRE-Luc transfected PC12 cells in the presence of NGF. We confirmed that the p38 MAPK inhibitor SB203580 and ERK inhibitor U0126 suppressed NGF-induced neurite outgrowth of PC12 cells, and found that the inhibitory effects of HA on phosphorylation of ERKs, but not of p38 MAPK, were restored by the anti-RHAMM antibody. The number of PC12 cells with neurites increased remarkably when pre-cultured with the anti-RHAMM antibody, then treated with NGF and HA. Our findings indicate that HA inhibits NGF-induced neuronal differentiation of PC12 cells partially by inhibiting ERK phosphorylation through RHAMM, and suggest that the binding of HA to RHAMM modifies the signaling pathways in PC12 cells treated with NGF.

Endogenous signals initiating inflammation in the injured nervous system

Glial cells are known to respond to a variety of neural injuries and play an important role in tissue damage and repair in the injured nervous system. This glial response, which is initially characterized by the expression of proinflammatory cytokines and chemokines and the attraction of microglial cells toward sites of injury, literally occurs within seconds to minutes of the injury. This suggests that signals that are endogenous to the nervous system are responsible for initiating neuroinflammation. In this review, we summarize the most recent advances made in the identification of these endogenous signals and describe the receptors and signaling pathways by which these ligands stimulate the production of cytokines and chemokines. Among these endogenous damage signals are ligands for toll-like receptors, including several heat shock proteins and extracellular matrix components, as well as self-derived RNA and DNA and associated proteins. Growing evidence also suggests that nucleotides released upon injury and acting through P2 receptors, such as ATP and UTP or their analogues, could serve as endogenous signals for the rapid response of glial cells.

In vivo injection of fibroblast growth factor-2 into the cisterna magna induces glypican-6 expression in mouse brain tissue

The proteoglycans (PGs) are multifunctional macromolecules composed of a core polypeptide and a variable number of glycosaminoglycan chains. In the nervous system, PGs regulate the structural organization of the extracellular matrix (ECM) and modulate growth factor activities and cell proliferation and migration. Most cortical neurons are generated from neural precursor cells that reside in the ventricular zone of the embryonic brain. The proliferation and differentiation of neural precursor cells are regulated by various growth and neurotrophic factors. Fibroblast growth factor-2 (FGF-2) is an important mitogen for cortical neural precursor cells, and glypicans regulate the action of FGF-2 on neural precursor cells. Glypican-6 is one of the most abundant ECM molecules in the brain. In this study the effects of FGF-2 on glypican-6 expression in brain tissue have been investigated. FGF-2 was injected into the cerebrospinal fluid (CSF) through the cisterna magna of mouse pups. Using Western blotting, it was shown that the expression of glypican-6 is increased in response to infusion of FGF-2 into the CSF. The injection of anti-FGF-2 antibody into the cisterna magna decreased glypican-6 expression in brain tissue. The results from this study suggest that glypican-6 is important in regulating FGF-2 activity during cerebral cortical development.

Heparin activates Wnt signaling for neuronal morphogenesis

Wnt factors are secreted ligands that affect different aspects of the nervous system behavior like neurodevelopment, synaptogenesis and neurodegeneration. In different model systems, Wnt signaling has been demonstrated to be regulated by heparan sulfate proteoglycans (HSPGs). Whether HSPGs modulate Wnt signaling in the context of neuronal behavior is currently unknown. Here we demonstrate that activation of Wnt signaling with the endogenous ligand Wnt-7a results in an increased of neurite outgrowth in the neuroblastoma N2a cell line. Interestingly, heparin induces glycogen synthase kinase-3beta (GSK-3beta) inhibition, beta-catenin stabilization and morphological differentiation in both N2a cells and in rat primary hippocampal neuronal cultures. We also show that heparin modulates Wnt-3a-induced stabilization of beta-catenin. Several extracellular matrix and membrane-attached HSPGs were found to be expressed in both in vitro neuronal models. Changes in the expression of specific HSPGs were observed upon differentiation of N2a cells. Taken together, our findings suggest that HSPGs may modulate canonical Wnt signaling for neuronal morphogenesis.