Molecular interactions of neural chondroitin sulfate proteoglycans in the brain development

The Composition and Cellular Sources of CSPGs in the Glial Scar After Spinal Cord Injury in the Lamprey

Axon regrowth after spinal cord injury (SCI) is inhibited by several types of inhibitory extracellular molecules in the central nervous system (CNS), including chondroitin sulfate proteoglycans (CSPGs), which also are components of perineuronal nets (PNNs). The axons of lampreys regenerate following SCI, even though their spinal cords contain CSPGs, and their neurons are enwrapped by PNNs. Previously, we showed that by 2 weeks after spinal cord transection in the lamprey, expression of CSPGs increased in the lesion site, and thereafter, decreased to pre-injury levels by 10 weeks. Enzymatic digestion of CSPGs in the lesion site with chondroitinase ABC (ChABC) enhanced axonal regeneration after SCI and reduced retrograde neuronal death. Lecticans (aggrecan, versican, neurocan, and brevican) are the major CSPG family in the CNS. Previously, we cloned a cDNA fragment that lies in the most conserved link-domain of the lamprey lecticans and found that lectican mRNAs are expressed widely in lamprey glia and neurons. Because of the lack of strict one-to-one orthology with the jawed vertebrate lecticans, the four lamprey lecticans were named simply A, B, C, and D. Using probes that distinguish these four lecticans, we now show that they all are expressed in glia and neurons but at different levels. Expression levels are relatively high in embryonic and early larval stages, gradually decrease, and are upregulated again in adults. Reductions of lecticans B and D are greater than those of A and C. Levels of mRNAs for lecticans B and D increased dramatically after SCI. Lectican D remained upregulated for at least 10 weeks. Multiple cells, including glia, neurons, ependymal cells and microglia/macrophages, expressed lectican mRNAs in the peripheral zone and lesion center after SCI. Thus, as in mammals, lamprey lecticans may be involved in axon guidance and neuroplasticity early in development. Moreover, neurons, glia, ependymal cells, and microglia/macrophages, are responsible for the increase in CSPGs during the formation of the glial scar after 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.

Perineuronal Net Dynamics in the Pathophysiology of Epilepsy

Perineuronal nets (PNNs) are condensed extracellular matrix (ECM) assemblies of polyanionic chondroitin sulfate proteoglycans, hyaluronan, and tenascins that primarily wrap around GABAergic parvalbumin (PV) interneurons. During development, PNN formation terminates the critical period of neuroplasticity, a process that can be reversed by experimental disruption of PNNs. Perineuronal nets also regulate the intrinsic properties of the enclosed PV neurons thereby maintaining their inhibitory activity. Recent studies have implicated PNNs in central nervous system diseases as well as PV neuron dysfunction; consequently, they have further been associated with altered inhibition, particularly in the genesis of epilepsy. A wide range of seizure presentations in human and rodent models exhibit ECM remodeling with PNN disruption due to elevated protease activity. Inhibition of PNN proteolysis reduces seizure activity suggesting that PNN degrading enzymes may be potential novel therapeutic targets.

Perineuronal Nets and Their Role in Synaptic Homeostasis

Extracellular matrix (ECM) molecules that are released by neurons and glial cells form perineuronal nets (PNNs) and modulate many neuronal and glial functions. PNNs, whose structure is still not known in detail, surround cell bodies and dendrites, which leaves free space for synapses to come into contact. A reduction in the expression of many neuronal ECM components adversely affects processes that are associated with synaptic plasticity, learning, and memory. At the same time, increased ECM activity, e.g., as a result of astrogliosis following brain damage or in neuroinflammation, can also have harmful consequences. The therapeutic use of enzymes to attenuate elevated neuronal ECM expression after injury or in Alzheimer’s disease has proven to be beneficial by promoting axon growth and increasing synaptic plasticity. Yet, severe impairment of ECM function can also lead to neurodegeneration. Thus, it appears that to ensure healthy neuronal function a delicate balance of ECM components must be maintained. In this paper we review the structure of PNNs and their components, such as hyaluronan, proteoglycans, core proteins, chondroitin sulphate proteoglycans, tenascins, and Hapln proteins. We also characterize the role of ECM in the functioning of the blood-brain barrier, neuronal communication, as well as the participation of PNNs in synaptic plasticity and some clinical aspects of perineuronal net impairment. Furthermore, we discuss the participation of PNNs in brain signaling. Understanding the molecular foundations of the ways that PNNs participate in brain signaling and synaptic plasticity, as well as how they change in physiological and pathological conditions, may help in the development of new therapies for many degenerative and inflammatory diseases of the brain.

Class I and Class II small leucine-rich proteoglycans in human cutaneous pacinian corpuscles

Pacinian corpuscles are onion bulb-like multilayered mechanoreceptors that consist of a complicated structure of axon terminals, Schwann related cells (inner core), endoneural related cells (intermediate layer) and perineurial related cells (outer core-capsule). The cells forming those compartments are continuous and share the properties of that covering the nerve fibers. Small leucine-rich proteoglycans are major proteoglycans of the extracellular matrix and regulate collagen fibrillogenesis, cell signalling pathways and extracellular matrix assembly. Here we used immunohistochemistry to investigate the distribution of class I (biglycan, decorin, asporin, ECM2 and ECMX) and class II (fibromodulin, lumican, prolargin, keratocan and osteoadherin) small leucine-rich proteoglycans in human cutaneous Pacinian corpuscles. The distribution of these compounds was: the inner core express decorin, biglycan, lumican, fibromodulin, osteoadherin; the intermediate layer display immunoreactivity for osteoadherin; the outer core biglycan, decorin, lumican, fibromodulin and osteoadherin; and the capsule contains biglycan, decorin, fibromodulin, and lumican. Asporin, prolargin and keratocan were undetectable. These results complement our knowledge about the distribution of small leucine-rich proteoglycans in human Pacinian corpuscles, and help to understand the composition of the extracellular matrix in these sensory formations.

Cerebrospinal fluid markers of extracellular matrix remodelling, synaptic plasticity and neuroinflammation before and after cranial radiotherapy

BACKGROUND

Advances in the treatment of brain tumours have increased the number of long-term survivors, but at the cost of side effects following cranial radiotherapy ranging from neurocognitive deficits to outright tissue necrosis. At present, there are no tools reflecting the molecular mechanisms underlying such side effects, and thus no means to evaluate interventional effects after cranial radiotherapy. Therefore, fluid biomarkers are of great clinical interest.

OBJECTIVE

Cerebrospinal fluid (CSF) levels of proteins involved in inflammatory signalling, synaptic plasticity and extracellular matrix (ECM) integrity were investigated following radiotherapy to the brain.

METHODS

Patients with small-cell lung cancer (SCLC) eligible for prophylactic cranial irradiation (PCI) were asked to participate in the study. PCI was prescribed either as 2 Gy/fraction to a total dose of 30 Gy (limited disease) or 4 Gy/fraction to 20 Gy (extensive disease). CSF was collected by lumbar puncture at baseline, 3 months and 1 year following PCI. Protein concentrations were measured using immunobased assays or mass spectrometry.

RESULTS

The inflammatory markers IL-15, IL-16 and MCP-1/CCL2 were elevated in CSF 3 months following PCI compared to baseline. The plasticity marker GAP-43 was elevated 3 months following PCI, and the same trend was seen for SNAP-25, but not for SYT1. The investigated ECM proteins, brevican and neurocan, showed a decline following PCI. There was a strong correlation between the progressive decline of soluble APPα and brevican levels.

CONCLUSION

To our knowledge, this is the first time ECM-related proteins have been shown to be affected by cranial radiotherapy in patients with cancer. These findings may help us to get a better understanding of the mechanisms behind side effects following radiotherapy.

ADAMTS-4 in oligodendrocytes contributes to myelination with an impact on motor function

Myelination is a late developmental process regulated by a set of inhibitory and stimulatory factors, including extracellular matrix components. Accordingly, chondroitin sulfate proteoglycans (CSPGs) act as negative regulators of myelination processes. A disintegrin and metalloproteinase with thrombospondin motifs type 4 (ADAMTS-4) is an extracellular protease capable of degrading CSPGs. Although exogenous ADAMTS-4 has been proven to be beneficial in several models of central nervous system (CNS) injuries, the physiological functions of endogenous ADAMTS-4 remain poorly understood. We first used Adamts4/LacZ reporter mice to reveal that ADAMTS-4 is strongly expressed in the CNS, especially in the white matter, with a cellular profile restricted to mature oligodendrocytes. Interestingly, we evidenced an abnormal myelination in Adamts4^-/- mice, characterized by a higher diameter of myelinated axons with a shifting g-ratio. Accordingly, lack of ADAMTS-4 is accompanied by motor deficits and disturbed nervous electrical activity. In conclusion, we demonstrate that ADAMTS-4 is a new marker of mature oligodendrocytes contributing to the myelination processes and thus to the control of motor capacities.

Amyloid plaques beyond Aβ: a survey of the diverse modulators of amyloid aggregation

Aggregation of the amyloid-β (Aβ) peptide is strongly correlated with Alzheimer's disease (AD). Recent research has improved our understanding of the kinetics of amyloid fibril assembly and revealed new details regarding different stages in plaque formation. Presently, interest is turning toward studying this process in a holistic context, focusing on cellular components which interact with the Aβ peptide at various junctures during aggregation, from monomer to cross-β amyloid fibrils. However, even in isolation, a multitude of factors including protein purity, pH, salt content, and agitation affect Aβ fibril formation and deposition, often producing complicated and conflicting results. The failure of numerous inhibitors in clinical trials for AD suggests that a detailed examination of the complex interactions that occur during plaque formation, including binding of carbohydrates, lipids, nucleic acids, and metal ions, is important for understanding the diversity of manifestations of the disease. Unraveling how a variety of key macromolecular modulators interact with the Aβ peptide and change its aggregation properties may provide opportunities for developing therapies. Since no protein acts in isolation, the interplay of these diverse molecules may differentiate disease onset, progression, and severity, and thus are worth careful consideration.

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.

Local Delivery of High-Dose Chondroitinase ABC in the Sub-Acute Stage Promotes Axonal Outgrowth and Functional Recovery after Complete Spinal Cord Transection

Chondroitin sulfate proteoglycans (CSPGs) are glial scar-associated molecules considered axonal regeneration inhibitors and can be digested by chondroitinase ABC (ChABC) to promote axonal regeneration after spinal cord injury (SCI). We previously demonstrated that intrathecal delivery of low-dose ChABC (1 U) in the acute stage of SCI promoted axonal regrowth and functional recovery. In this study, high-dose ChABC (50 U) introduced via intrathecal delivery induced subarachnoid hemorrhage and death within 48 h. However, most SCI patients are treated in the sub-acute or chronic stages, when the dense glial scar has formed and is minimally digested by intrathecal delivery of ChABC at the injury site. The present study investigated whether intraparenchymal delivery of ChABC in the sub-acute stage of complete spinal cord transection would promote axonal outgrowth and improve functional recovery. We observed no functional recovery following the low-dose ChABC (1 U or 5 U) treatments. Furthermore, animals treated with high-dose ChABC (50 U or 100 U) showed decreased CSPGs levels. The extent and area of the lesion were also dramatically decreased after ChABC treatment. The outgrowth of the regenerating axons was significantly increased, and some partially crossed the lesion site in the ChABC-treated groups. In addition, retrograde Fluoro-Gold (FG) labeling showed that the outgrowing axons could cross the lesion site and reach several brain stem nuclei involved in sensory and motor functions. The Basso, Beattie and Bresnahan (BBB) open field locomotor scores revealed that the ChABC treatment significantly improved functional recovery compared to the control group at eight weeks after treatment. Our study demonstrates that high-dose ChABC treatment in the sub-acute stage of SCI effectively improves glial scar digestion by reducing the lesion size and increasing axonal regrowth to the related functional nuclei, which promotes locomotor recovery. Thus, our results will aid in the treatment of spinal cord injury.

Extracellular matrix assembly: a multiscale deconstruction

The biochemical and biophysical properties of the extracellular matrix (ECM) dictate tissue-specific cell behaviour. The molecules that are associated with the ECM of each tissue, including collagens, proteoglycans, laminins and fibronectin, and the manner in which they are assembled determine the structure and the organization of the resultant ECM. The product is a specific ECM signature that is comprised of unique compositional and topographical features that both reflect and facilitate the functional requirements of the tissue.

Extracellular matrix assembly: a multiscale deconstruction

The biochemical and biophysical properties of the extracellular matrix (ECM) dictate tissue-specific cell behaviour. The molecules that are associated with the ECM of each tissue, including collagens, proteoglycans, laminins and fibronectin, and the manner in which they are assembled determine the structure and the organization of the resultant ECM. The product is a specific ECM signature that is comprised of unique compositional and topographical features that both reflect and facilitate the functional requirements of the tissue.

Extracellular matrix assembly: a multiscale deconstruction

The biochemical and biophysical properties of the extracellular matrix (ECM) dictate tissue-specific cell behaviour. The molecules that are associated with the ECM of each tissue, including collagens, proteoglycans, laminins and fibronectin, and the manner in which they are assembled determine the structure and the organization of the resultant ECM. The product is a specific ECM signature that is comprised of unique compositional and topographical features that both reflect and facilitate the functional requirements of the tissue.

Thyroid hormone treated astrocytes induce maturation of cerebral cortical neurons through modulation of proteoglycan levels

Proper brain neuronal circuitry formation and synapse development is dependent on specific cues, either genetic or epigenetic, provided by the surrounding neural environment. Within these signals, thyroid hormones (T3 and T4) play crucial role in several steps of brain morphogenesis including proliferation of progenitor cells, neuronal differentiation, maturation, migration, and synapse formation. The lack of thyroid hormones during childhood is associated with several impair neuronal connections, cognitive deficits, and mental disorders. Many of the thyroid hormones effects are mediated by astrocytes, although the mechanisms underlying these events are still unknown. In this work, we investigated the effect of 3, 5, 3′-triiodothyronine-treated (T3-treated) astrocytes on cerebral cortex neuronal differentiation. Culture of neural progenitors from embryonic cerebral cortex mice onto T3-treated astrocyte monolayers yielded an increment in neuronal population, followed by enhancement of neuronal maturation, arborization and neurite outgrowth. In addition, real time PCR assays revealed an increase in the levels of the heparan sulfate proteoglycans, Glypican 1 (GPC-1) and Syndecans 3 e 4 (SDC-3 e SDC-4), followed by a decrease in the levels of the chondroitin sulfate proteoglycan, Versican. Disruption of glycosaminoglycan chains by chondroitinase AC or heparanase III completely abolished the effects of T3-treated astrocytes on neuronal morphogenesis. Our work provides evidence that astrocytes are key mediators of T3 actions on cerebral cortex neuronal development and identified potential molecules and pathways involved in neurite extension; which might eventually contribute to a better understanding of axonal regeneration, synapse formation, and neuronal circuitry recover.

Chondroitin sulfate synthase-2 is necessary for chain extension of chondroitin sulfate but not critical for skeletal development

Chondroitin sulfate (CS) is a linear polysaccharide consisting of repeating disaccharide units of N-acetyl-D-galactosamine and D-glucuronic acid residues, modified with sulfated residues at various positions. Based on its structural diversity in chain length and sulfation patterns, CS provides specific biological functions in cell adhesion, morphogenesis, neural network formation, and cell division. To date, six glycosyltransferases are known to be involved in the biosynthesis of chondroitin saccharide chains, and a hetero-oligomer complex of chondroitin sulfate synthase-1 (CSS1)/chondroitin synthase-1 and chondroitin sulfate synthase-2 (CSS2)/chondroitin polymerizing factor is known to have the strongest polymerizing activity. Here, we generated and analyzed CSS2^−/− mice. Although they were viable and fertile, exhibiting no overt morphological abnormalities or osteoarthritis, their cartilage contained CS chains with a shorter length and at a similar number to wild type. Further analysis using CSS2^−/− chondrocyte culture systems, together with siRNA of CSS1, revealed the presence of two CS chain species in length, suggesting two steps of CS chain polymerization; i.e., elongation from the linkage region up to Mr ∼10,000, and further extension. There, CSS2 mainly participated in the extension, whereas CSS1 participated in both the extension and the initiation. Our study demonstrates the distinct function of CSS1 and CSS2, providing a clue in the elucidation of the mechanism of CS biosynthesis.

Altered expression pattern of testican-1 mRNA after brain injury

Testican, a chondroitin/heparan sulfate proteoglycan, is primarily expressed in neurons of the adult and embryonic mouse brain, suggesting its role in normal and/or proliferation and differentiation processes of neurons. However, the role of testican in injured brain remains unclear. In the present study we investigated testican-1 mRNA expression pattern after cryo-injury of the brain. In situ hybridization histochemistry revealed that testican-1 mRNA is induced in the region surrounding the necrotic tissue. Time course study of testican-1 mRNA showed the highest level of signal intensity at 7 days after the injury. To determine which cell types express testican-1 mRNA, we performed in situ hybridization histochemistry combined with immunohistochemistry of several cell markers. Testican-1 mRNA signals were detected in the proximal reactive astrocytes, whereas the distribution pattern of testican-1 mRNA positive cells was different from those of mature oligodendrocytes and activated microglia. In addition, signals for testican-1 mRNA overlapped with those of FGF-2 mRNA, showing that these molecules are coexpressed in reactive astrocytes. These results suggest a possibility that testican-1 plays a permissive role for regenerating axons in reactive astrocytes after injury.

Comprehensive tissue processing strategy for quantitative proteomics of formalin-fixed multiple sclerosis lesions

Formalin-fixed (FF) autopsy tissue comprises the bulk of existing Multiple Sclerosis (MSc) pathology archives, providing a rich pool of material for biomarker discovery and disease characterization. Here, we present the development of a heat-induced extraction protocol for the proteomic analysis of FF brain tissue, its application to the study of lesion remyelination and its failure in MSc. A 4-round extraction strategy was optimized using FF tissue leading to a 35% increase in the number of proteins identified compared to a single extraction; and a 65% increase in proteins identified with ≥4 peptides. Histological staining of sections with oil red O and luxol fast blue-periodic acid Schiff, required to characterize MSc lesions was found to have minimal effect on LC-MS/MS. The application of the optimized protocol to chronic demyelinated and remyelinated FF MSc lesions and the adjacent periplaque white matter, isolated through laser guided manual dissection from 3 patients, identified 428 unique proteins (0.2% FDR) using LC-MS/MS. Comparison of the lesion types using iTRAQ and 2-D LC-MS/MS revealed 82 differentially expressed proteins. Protein quantitation by iTRAQ and spectral counting was well-correlated (r(s)= 0.7653; p < 10(-30)). The data generated from this work illustrates the scope of the methodology and provides insights into the pathogenesis of MSc and remyelination.

Extracellular matrix abnormalities in schizophrenia

Emerging evidence points to the involvement of the brain extracellular matrix (ECM) in the pathophysiology of schizophrenia (SZ). Abnormalities affecting several ECM components, including Reelin and chondroitin sulfate proteoglycans (CSPGs), have been described in subjects with this disease. Solid evidence supports the involvement of Reelin, an ECM glycoprotein involved in corticogenesis, synaptic functions and glutamate NMDA receptor regulation, expressed prevalently in distinct populations of GABAergic neurons, which secrete it into the ECM. Marked changes of Reelin expression in SZ have typically been reported in association with GABA-related abnormalities in subjects with SZ and bipolar disorder. Recent findings from our group point to substantial abnormalities affecting CSPGs, a main ECM component, in the amygdala and entorhinal cortex of subjects with schizophrenia, but not bipolar disorder. Striking increases of glial cells expressing CSPGs were accompanied by reductions of perineuronal nets, CSPG- and Reelin-enriched ECM aggregates enveloping distinct neuronal populations. CSPGs developmental and adult functions, including neuronal migration, axon guidance, synaptic and neurotransmission regulation are highly relevant to the pathophysiology of SZ. Together with reports of anomalies affecting several other ECM components, these findings point to the ECM as a key component of the pathology of SZ. We propose that ECM abnormalities may contribute to several aspects of the pathophysiology of this disease, including disrupted connectivity and neuronal migration, synaptic anomalies and altered GABAergic, glutamatergic and dopaminergic neurotransmission.

Chondroitin sulphate proteoglycans: key modulators of spinal cord and brain plasticity

Chondroitin sulphate proteoglycans (CSPGs) are a family of inhibitory extracellular matrix molecules that are highly expressed during development, where they are involved in processes of pathfinding and guidance. CSPGs are present at lower levels in the mature CNS, but are highly concentrated in perineuronal nets where they play an important role in maintaining stability and restricting plasticity. Whilst important for maintaining stable connections, this can have an adverse effect following insult to the CNS, restricting the capacity for repair, where enhanced synapse formation leading to new connections could be functionally beneficial. CSPGs are also highly expressed at CNS injury sites, where they can restrict anatomical plasticity by inhibiting sprouting and reorganisation, curbing the extent to which spared systems may compensate for the loss function of injured pathways. Modification of CSPGs, usually involving enzymatic degradation of glycosaminoglycan chains from the CSPG molecule, has received much attention as a potential strategy for promoting repair following spinal cord and brain injury. Pre-clinical studies in animal models have demonstrated a number of reparative effects of CSPG modification, which are often associated with functional recovery. Here we discuss the potential of CSPG modification to stimulate restorative plasticity after injury, reviewing evidence from studies in the brain, the spinal cord and the periphery.

Differential gene expression of multiple chondroitin sulfate modification enzymes among neural stem cells, neurons and astrocytes

Chondroitin sulfate/dermatan sulfate (CS/DS) polysaccharides have been reported to play a crucial role in the proliferation and maintenance of neural stem cells (NSCs). However, little is known about the structural changes and functional role of CS/DS chains in the differentiation of NSCs. Western blots of NSCs, neurons and astrocytes in culture, with three CS-polysaccharide antibodies of different specificities, revealed marked differences in CS structure among the three cell types. To confirm this finding, we measured gene expression levels of CS sulfotransferases and C5-epimerase in these cell types, as these are responsible for producing the high structural diversity of CS/DS. Expressions of chondroitin 4-O-sulfotransferase, chondroitin 6-O-sulfotransferase, and N-acetylgalactosamine 4-sulfate 6-O-sulfotransferase mRNAs were low in cultures of differentiated neural cells, such as neurons and astrocytes, in comparison to NSCs. In contrast, expressions of uronyl 2-O-sulfotransferase and C5-epimerase mRNAs were higher in the differentiated neural cells than NSCs. Thus, we first provide evidence to support the hypothesis that CS/DS undergoes structural changes during NSC differentiation. The structural changes in CS/DS may be implicated in the regulation of NSC differentiation through interactions with growth/neurotrophic factors and cytokines.

Lysophosphatidylcholine-mediated functional inactivation of syndecan-4 results in decreased adhesion and motility of dendritic cells

Following antigen contact, maturation and migration of DCs into lymphatic tissues are crucial to the developing immune response or maintenance of tolerance. Lysophosphatidylcholine (LysoPC) is generated during apoptosis of cells and acts as a "find-and-eat-me" signal thought to prevent autoimmunity. Moreover, LysoPC can activate PKCδ and initiates a signaling cascade that leads to phosphorylation and inactivation of syndecan-4 (SDC4), a heparansulfate proteoglycan integrin co-receptor. In human monocyte-derived DCs, we recently demonstrated that SDC4 is upregulated during maturation thereby stimulating DC motility. Here, we investigate the effects of LysoPC on DC motility as well as on the involvement of PKCδ phosphorylation-dependent regulation of DC motility by SDC4 and PKCα. Employing a static adhesion assay and videomicroscopy, we show that LysoPC inhibits adhesion of DCs to fibronectin and motility of DCs by decreasing podosome formation. Moreover, DC podosome formation and motility, which both are regulated by SDC4 and subject to control by PKCδ-dependent phosphorylation of SDC4, were inhibited in LysoPC-matured DCs. Thus, these DC are defective in adhesion and migration. Based on our results, we hypothesize that LysoPC released during apoptosis might delay DC migration to lymphoid organs and thus prevent autoimmunity.

Chondroitin sulfate synthase-2/chondroitin polymerizing factor has two variants with distinct function

Chondroitin sulfate (CS) is a polysaccharide consisting of repeating disaccharide units of N-acetyl-D-galactosamine and d-glucuronic acid residues, modified with sulfated residues at various positions. To date six glycosyltransferases for chondroitin synthesis have been identified, and the complex of chondroitin sulfate synthase-1 (CSS1)/chondroitin synthase-1 (ChSy-1) and chondroitin sulfate synthase-2 (CSS2)/chondroitin polymerizing factor is assumed to play a major role in CS biosynthesis. We found an alternative splice variant of mouse CSS2 in a data base that lacks the N-terminal transmembrane domain, contrasting to the original CSS2. Here, we investigated the roles of CSS2 variants. Both the original enzyme and the splice variant, designated CSS2A and CSS2B, respectively, were expressed at different levels and ratios in tissues. Western blot analysis of cultured mouse embryonic fibroblasts confirmed that both enzymes were actually synthesized as proteins and were localized in both the endoplasmic reticulum and the Golgi apparatus. Pulldown assays revealed that either of CSS2A, CSS2B, and CSS1/ChSy-1 heterogeneously and homogeneously interacts with each other, suggesting that they form a complex of multimers. In vitro glycosyltransferase assays demonstrated a reduced glucuronyltransferase activity in CSS2B and no polymerizing activity in CSS2B co-expressed with CSS1, in contrast to CSS2A co-expressed with CSS1. Radiolabeling analysis of cultured COS-7 cells overexpressing each variant revealed that, whereas CSS2A facilitated CS biosynthesis, CSS2B inhibited it. Molecular modeling of CSS2A and CSS2B provided support for their properties. These findings, implicating regulation of CS chain polymerization by CSS2 variants, provide insight in elucidating the mechanisms of CS biosynthesis.

Stem cell therapies for spinal cord injury

Stem cell therapy is a potential treatment for spinal cord injury (SCI), and a variety of different stem cell types have been evaluated in animal models and humans with SCI. No consensus exists regarding the type of stem cell, if any, that will prove to be effective therapeutically. Most data suggest that no single therapy will be sufficient to overcome all the biological complications caused by SCI. Rationales for therapeutic use of stem cells for SCI include replacement of damaged neurons and glial cells, secretion of trophic factors, regulation of gliosis and scar formation, prevention of cyst formation, and enhancement of axon elongation. Most therapeutic approaches that use stem cells involve implantation of these cells into the spinal cord. The attendant risks of stem cell therapy for SCI--including tumor formation, or abnormal circuit formation leading to dysfunction--must be weighed against the potential benefits of this approach. This Review will examine the biological effects of SCI, the opportunities for stem cell treatment, and the types of stem cells that might be used therapeutically. The limited information available on the possible benefits of stem cell therapy to humans will also be discussed.

Extracellular matrix in multiple sclerosis lesions: Fibrillar collagens, biglycan and decorin are upregulated and associated with infiltrating immune cells

Extracellular matrix (ECM) proteins can modify immune reactions, e.g. by sequestering or displaying growth factors and by interacting with immune and glial cells. Here we quantified by quantitative polymerase chain reaction (qPCR) expression of 50 ECM components and 34 ECM degrading enzymes in multiple sclerosis (MS) active and inactive white matter lesions. COL1A1, COL3A1, COL5A1 and COL5A2 chains were induced strongly in active lesions and even more in inactive lesions. These chains interact to form collagen types I, III and V, which are fibrillar collagens. Biglycan and decorin, which can decorate fibrillar collagens, were also induced strongly. The fibrillar collagens, biglycan and decorin were largely found between the endothelium and astrocytic glia limitans in the perivascular space where they formed a meshwork which was closely associated with infiltrating immune cells. In active lesions collagen V was also seen in the heavily infiltrated parenchyma. Fibrillar collagens I and III inhibited in vitro human monocyte production of CCL2 (MCP-1), an inflammatory chemokine involved in recruitment of immune cells. Together, ECM changes in lesions with different activities were quantified and proteins forming a perivascular fibrosis were identified. Induced fibrillar collagens may contribute to limiting enlargement of MS lesions by inhibiting the production of CCL2 by monocytes.

Activity-dependent remodeling of chondroitin sulfate proteoglycans extracellular matrix in the hypothalamo-neurohypophysial system

The hypothalamo-neurohypophysial system (HNS) consisting of arginine vasopressin (AVP) and oxytocin (OXT) magnocellular neurons shows the structural plasticity including the rearrangement of synapses, dendrites, and neurovascular contacts during chronic physiological stimulation. In this study, we examined the remodeling of chondroitin sulfate proteoglycans (CSPGs), main extracellular matrix (ECM), in the HNS after salt loading known as a chronic stimulation to cause the structural plasticity. In the supraoptic nucleus (SON), confocal microscopic observation revealed that the immunoreactivity of 6B4 proteoglycans (PG) was observed mainly at AVP-positive magnocellular neurons but that of neurocan was seen chiefly at OXT-positive magnocellular neurons. The immunoreactivity of phosphacan and aggrecan was seen at both AVP- and OXT-positive magnocellular neurons. Electron microscopic observation further showed that the immunoreactivity of phosphacan and neurocan was observed at astrocytic processes to surround somata, dendrites, and terminals, but not synaptic junctions. In the neurohypophysis (NH), the immunoreactivity of phosphacan, 6B4 PGs, and neurocan was observed at AVP-positive magnocellular terminals, but the reactivity of Wisteria floribunda agglutinin lectin was seen at OXT-positive ones. The immunoreactivity of versican was found at microvessel and that of aggrecan was not detected in the NH. Quantitative morphometrical analysis showed that the chronic physiological stimulation by 7-day salt loading decreased the level of 6B4 PGs in the SON and the level of phosphacan, 6B4 PGs, and neurocan in the NH. These results suggest that the extracellular microenvironment of CSPGs is different between AVP and OXT magnocellular neurons and activity-dependent remodeling of CSPGs could be involved in the structural plasticity of the HNS.

Functional difference of receptor-type protein tyrosine phosphatase zeta/beta isoforms in neurogenesis of hippocampal neurons

Receptor-type protein tyrosine phosphatase zeta/beta (RPTPzeta) is a transmembrane chondroitin sulfate proteoglycan (CSPG) and has been shown to play crucial roles in controlling axonal growth and neuronal migration. The RPTPzeta has two transmembranous isoforms, shorter receptor form of RPTPzeta (sRPTPzeta) and full-length receptor form of RPTPzeta (fRPTPzeta), but no studies have been reported about functional difference of these two isoforms. In the present study, therefore, we examined whether or not two RPTPzeta isoforms have different role in controlling dendritic morphology and synaptic number in cultured hippocampal neurons using the quantitative morphometrical analysis. Confocal microscopic observation showed that the immunoreactivity of RPTPzeta was observed throughout cells such as axons, growth cones, and dendrites at the early stages of neuronal culture, while it was seen predominantly on dendrites at the late stages. Western blotting analysis revealed that fRPTPzeta was mainly expressed at the early stages of culture and both RPTPzeta isoforms were expressed at late stages of culture. The overexpression of sRPTPzeta in hippocampal neurons increased the dendritic arborization without altering the average length of dendritic branches, whereas that of fRPTPzeta decreased the dendritic arborization and increased the average length of dendritic branches. The RNA interference of fRPTPzeta expression increased the dendritic arborization without altering the average length of dendritic branches. The overexpression of fRPTPzeta decreased the density of hippocampal dendritic synapses, but that of sRPTPzeta had no effects. Pleiotrophin, a ligand for RPTPzeta to interfere the phosphatase activity, increased the density of hippocampal dendritic synapses. Thus, the present study demonstrates that two transmembranous RPTPzeta isoforms have different functions for regulating dendritogenesis and synaptogenesis.

Influence of aging on chondroitin sulfate proteoglycan expression and neural stem/progenitor cells in rat brain and improving effects of a herbal medicine, yokukansan

There is evidence of structural and functional deterioration in the brain, including the prefrontal cortex (PFC) and hippocampus, during the normal aging process in animals and humans. Extracellular matrix-associated glycoproteins, such as chondroitin sulfate proteoglycans (CSPGs), are involved in not only maintaining the structures and functions of adult neurons, but also regulating the proliferation, migration, and neurite outgrowth of neural stem cells in the brain. On the other hand, a herbal medicine, yokukansan (YKS), is used in a variety of clinical situations for treating symptoms associated with age-related neurodegenerative disorders such as Alzheimer's disease, but its pharmacological properties have not been fully understood. The present study was designed to clarify the influence of aging and the improving effects of YKS on the expression of aggrecan, a major molecule of CSPGs, and on the proliferation and migration of neural stem/progenitor cells identified by bromodeoxyuridine (BrdU) incorporation in the PFC and hippocampus including the dentate gyrus. Aged rats (24 months old) showed a significant increase in aggrecan expression throughout the PFC and in the hippocampus particularly in the CA3 subfield, but not the dentate gyrus compared to young rats (5 months old), evaluated by the immunohistochemical method. YKS treatment decreased the age-related increase in aggrecan expression as well as normal expression in young rats. Aged rats also showed a decreased number of BrdU-labeled cells in the PFC and hippocampus, and these decreases were improved by YKS treatment, which also increased the numbers in young rats. These results suggest that aging influences the microenvironment for adult and immature neurons in the brain, which may affect the proliferation and migration of neural stem/progenitor cells, and YKS has pharmacological potency for these age-related events. These findings help to understand the physiology and pathology of the aged brain and provide an anti-aging strategy for the brain.

Transforming growth factor-beta1 upregulates keratan sulfate and chondroitin sulfate biosynthesis in microglias after brain injury

After injury to the adult central nervous system, levels of extracellular matrix molecules increase at the injury site and may inhibit the repair of injured axons. Among these molecules, the importance of proteoglycans, particularly their chondroitin sulfate chains, has been highlighted. We have recently reported that keratan sulfate-deficient mice show better axonal regeneration after injury. Here, we investigated the regulation of keratan sulfate and chondroitin sulfate biosynthesis after neuronal injuries. Several key enzymes required for glycosaminoglycan biosynthesis (beta3GlcNAcT-7 and GlcNAc6ST-1 for keratan sulfate; CS synthase-1 and C6ST-1 for chondroitin sulfate) were expressed at significantly higher levels in the lesion 7 days after a knife-cut injury was made to the cerebral cortex in adult mice. These increases were accompanied by increased expression of TGF-beta(1) and bFGF. Since microglias at the injury sites expressed both keratan sulfate and chondroitin sulfate, the effects of these cytokines were examined in microglias. TGF-beta(1) induced the expression of the above-named enzymes in microglias, and consequently induced keratan sulfate and chondroitin sulfate biosynthesis as well as the expression of the chondroitin/keratan sulfate proteoglycan aggrecan in these cells. TGF-beta(1) also induced bFGF expression in microglias. bFGF in turn induced TGF-beta(1) expression in astrocytes. Astrocyte-conditioned medium following bFGF stimulation indeed induced keratan sulfate and chondroitin sulfate production in microglias. This production was blocked by TGF-beta(1)-neutralizing antibody. Taken together, our data indicate that the biosyntheses of keratan sulfate and chondroitin sulfate are upregulated in common by TGF-beta(1) in microglias after neuronal injuries.

Glial and axonal regeneration following spinal cord injury

Spinal cord injury (SCI) has been regarded clinically as an irreversible damage caused by tissue contusion due to a blunt external force. Past research had focused on the analysis of the pathogenesis of secondary injury that extends from the injury epicenter to the periphery, as well as tissue damage and neural cell death associated with secondary injury. Recent studies, however, have proven that neural stem (progenitor) cells are also present in the brain and spinal cord of adult mammals including humans. Analyses using spinal cord injury models have also demonstrated active dynamics of cells expressing several stem cell markers, and methods aiming at functional reconstruction by promoting the potential self-regeneration capacity of the spinal cord are being explored. Furthermore, reconstruction of the neural circuit requires not only replenishment or regeneration of neural cells but also regeneration of axons. Analysis of the tissue microenvironment after spinal cord injury and research aiming to remove axonal regeneration inhibitors have also made progress. SCI is one of the simplest central nervous injuries, but its pathogenesis is associated with diverse factors, and further studies are required to elucidate these complex interactions in order to achieve spinal cord regeneration and functional reconstruction.

Glycosaminoglycan in cerebrum, cerebellum and brainstem of young sheep brain with particular reference to compositional and structural variations of chondroitin-dermatan sulfate and hyaluronan

Recent advances in the structural biology of chondroitin sulfate chains have suggested important biological functions in the development of the brain. Several studies have demonstrated that the composition of chondroitin sulfate chains changes with aging and normal brain maturation. In this study, we determined the concentration of all glycosaminoglycan types, i.e. chondroitin sulfate, dermatan sulfate, keratan sulfate, heparan sulfate, hyaluronan and chondroitin in cerebrum, cerebellum and brainstem of young sheep brain. In all cases, chondroitin sulfate was the predominant glycosaminoglycan type, comprising about 54-58% of total glycosaminoglycans, with hyaluronan being present also in significant amounts of about 19-28%. Of particular interest was the increased presence of the disulfated disaccharides and dermatan sulfate in cerebellum and brainstem, respectively, as well as the detectable and measurable occurrence of chondroitin in young sheep brain. Among the three brain areas, cerebrum was found to be significantly richer in chondroitin sulfate and hyaluronan, two major extracellular matrix components. These findings imply that the extracellular matrix of the cerebrum is different from those of cerebellum and brainstem, and probably this fact is related to the particular histological and functional characteristics of each anatomic area of the brain.

Reduction of brain injury in neonatal hypoxic-ischemic rats by intracerebroventricular injection of neural stem/progenitor cells together with chondroitinase ABC

Perinatal hypoxia-ischemia (HI) remains a critical issue. Cell transplantation therapy could be a potent treatment for many neurodegenerative diseases, but limited works on this kind of therapy have been reported for perinatal HI. In this study, the therapeutic effect of transplantation with neural stem/ progenitor cells (NSPCs) and chondrotinase ABC (ChABC) in a neonatal HI rat model is evaluated. Histological studies showed that the unaffected area of the brain in animals treated with NSPCs together with ChABC was significantly larger than that in the animals treated with vehicle or NSPCs alone. The wet weight of the brain that received the combined treatment was also significantly higher than those of the vehicle and their individual treatments. These results indicate that intracerebroventricular injection of NSPCs with ChABC reduces brain injury in a rat neonatal HI model.

Distribution and synthesis of extracellular matrix proteoglycans, hyaluronan, link proteins and tenascin-R in the rat spinal cord

Perineuronal nets (PNNs) are dense extracellular matrix (ECM) structures that form around many neuronal cell bodies and dendrites late in development. They contain several chondroitin sulphate proteoglycans (CSPGs), hyaluronan, link proteins and tenascin-R. Their time of appearance correlates with the ending of the critical period for plasticity, and they have been implicated in this process. The distribution of PNNs in the spinal cord was examined using Wisteria floribunda agglutinin lectin and staining for chondroitin sulphate stubs after chondroitinase digestion. Double labelling with the neuronal marker, NeuN, showed that PNNs were present surrounding approximately 30% of motoneurons in the ventral horn, 50% of large interneurons in the intermediate grey and 20% of neurons in the dorsal horn. These PNNs formed in the second week of postnatal development. Immunohistochemical staining demonstrated that the PNNs contain a mixture of CSPGs, hyaluronan, link proteins and tenascin-R. Of the CSPGs, aggrecan was present in all PNNs while neurocan, versican and phosphacan/RPTPbeta were present in some but not all PNNs. In situ hybridization showed that aggrecan and cartilage link protein (CRTL 1) and brain link protein-2 (BRAL 2) are produced by neurons. PNN-bearing neurons express hyaluronan synthase, and this enzyme and phosphacan/RPTPbeta may attach PNNs to the cell surface. During postnatal development the expression of link protein and aggrecan mRNA is up-regulated at the time of PNN formation, and these molecules may therefore trigger their formation.

2-o-phosphorylation of xylose and 6-o-sulfation of galactose in the protein linkage region of glycosaminoglycans influence the glucuronyltransferase-I activity involved in the linkage region synthesis

Sulfated glycosaminoglycans (GAGs), including heparan sulfate and chondroitin sulfate, are synthesized on the so-called common GAG-protein linkage region (GlcUAbeta1-3Galbeta1-3Galbeta1-4Xylbeta1-O-Ser) of core proteins, which is formed by the stepwise addition of monosaccharide residues by the respective specific glycosyltransferases. Glucuronyltransferase-I (GlcAT-I) is the key enzyme that completes the synthesis of this linkage region, which is a prerequisite for the conversion of core proteins to functional proteoglycans bearing GAGs. The Xyl and Gal residues in the linkage region can be modified by phosphorylation and sulfation, respectively, although the biological significance of these modifications remains to be clarified. Here we present evidence that these modifications can significantly influence the catalytic activity of GlcAT-I. Enzyme assays showed that the synthetic substrates, Gal-Gal-Xyl(2-O-phosphate)-O-Ser and Gal-Gal(6-O-sulfate)-Xyl(2-O-phosphate)-O-Ser, served as better substrates than the unmodified compound, whereas Gal(6-O-sulfate)-Gal-Xyl(2-O-phosphate)-O-Ser exhibited no acceptor activity. The crystal structure of the catalytic domain of GlcAT-I with UDP and Gal-Gal(6-O-sulfate)-Xyl(2-O-phosphate)-O-Ser bound revealed that the Xyl(2-O-phosphate)-O-Ser is disordered and the 6-O-sulfate forms interactions with Gln(318) from the second GlcAT-I monomer in the dimeric enzyme. The results indicate the possible involvement of these modifications in the processing and maturation of the growing linkage region oligosaccharide required for the assembly of GAG chains.

Endoplasmic reticulum stress upregulates the chondroitin sulfate level which thus prevents neurite extension in C6 glioma cells and primary cultured astrocytes

Chondroitin sulfate (CS), which is known to be a neurite-preventing molecule, is a major component of the extracellular matrix (ECM) in the central nervous system (CNS). The CS expression is upregulated around damaged areas. Endoplasmic reticulum (ER) stress causes neuronal cell death in numerous neurodegenerative diseases. However, the effects of ER stress on glial cells remain to be clarified. The present study examined whether direct ER stress to glial cells can upregulate CS expression in C6 glioma cells and primary cultured mouse astrocytes, and also whether the expression of CS prevents neurite extension. ER stressors tunicamycin (TM) and thapsigargin (TG) significantly increased CS expression in both C6 cells and primary cultured astrocytes, while NO donor sodium nitroprusside (SNP) did not significantly alter the CS expression. The dosage of TM and TG treatment used in this study did not significantly induce cell death but upregulated the ER chaperone molecule Grp78 in C6 glioma cells and primary astrocytes. The ECM of glial cells exposed to ER stress prevented neurite extension in primary cultured mouse cortical neurons, and chondroitinase ABC (ChABC) treatment diminished the inhibitory effect on neurite extension. These findings suggest that direct ER stress to glial cells increases the CS expression, which thus prevents neurite extension.

[Regulation of neuronal cell function by glyco-signals]

Gangliosides and proteoglycans with various sugar chains exist abundantly in the brain. They participate in intercellular recognition by revealing the sugar chains on the cell surface, and some of them show neurite-extension activity. Several recognition features that are mediated by the sugar chains are known such as saccharide-saccharide interaction and cell-surface sugar-chain receptor-mediated recognition. Experiments on animals lacking the sugar-chain synthetic system with the technique of gene targeting suggest that phylogenetically "old" sugar chains such as chondroitin sulfate appear necessary for early development of the organism while relatively "new" sugar chains such as gangliosides, which appear with further development of the brain, are necessary for differentiation maturity processes. On the other hand, research using primary cultured neurons showed similar effects of the gangliosides and chondroitin sulfate on cell differentiation. It is possible that these sugar chains share the glyco-receptor-mediated signal transduction system.

Hyaluronan is organized into fiber-like structures along migratory pathways in the developing mouse cerebellum

Hyaluronan is a free glycosaminoglycan which is abundant in the extracellular matrix of the developing brain. Although not covalently linked to any protein it can act as a backbone molecule forming aggregates with chondroitin sulfate proteoglycans of the lectican family and link proteins. Using neurocan-GFP as a direct histochemical probe we analyzed the distribution and organization of hyaluronan in the developing mouse cerebellum, and related its fine structure to cell types of specified developmental stages. We observed a high affinity of this probe to fiber-like structures in the prospective white matter which are preferentially oriented parallel to the cerebellar cortex during postnatal development suggesting a specially organized form of hyaluronan. In other layers of the cerebellar cortex, the hyaluronan organization seemed to be more diffuse. During the second postnatal week, the overall staining intensity of hyaluronan in the white matter declined but fiber-like structures were still present at the adult stage. This type of hyaluronan organization is different from perineuronal nets e.g. found in deep cerebellar nuclei. Double staining experiments with cell type specific markers indicated that these fiber-like structures are predominantly situated in regions where motile cells such as Pax2-positive inhibitory interneuron precursors and MBP-positive oligodendroglial cells are located. In contrast, more stationary cells such as mature granule cells and Purkinje cells are associated with lower levels of hyaluronan in their environment. Thus, hyaluronan-rich fibers are concentrated at sites where specific neural precursor cell types migrate, and the anisotropic orientation of these fibers suggests that they may support guided neural migration during brain development.

Ectodomain shedding of neuroglycan C, a brain-specific chondroitin sulfate proteoglycan, by TIMP-2- and TIMP-3-sensitive proteolysis

Neuroglycan C (NGC) is a transmembrane-type of chondroitin sulfate proteoglycan with an epidermal growth factor (EGF)-like module that is exclusively expressed in the CNS. Because ectodomain shedding is a common processing step for many transmembrane proteins, we examined whether NGC was subjected to proteolytic cleavage. Western blotting demonstrated the occurrence of a soluble form of NGC with a 75 kDa core glycoprotein in the soluble fraction of the young rat cerebrum. In contrast, full-length NGC with a 120 kDa core glycoprotein and its cytoplasmic fragment with a molecular size of 35 kDa could be detected in the membrane fraction. The soluble form of NGC was also detectable in culture media of fetal rat neurons, and the full-length form existed in cell layers. The amount of the soluble form in culture media was decreased by adding a physiological protease inhibitor such as a tissue inhibitor of metalloproteinase (TIMP)-2 or TIMP-3, but not by adding TIMP-1. Both EGF-like and neurite outgrowth-promoting activity of the NGC ectodomain may be regulated by this proteolytic processing.

The role of chondroitin sulfate proteoglycans in regeneration and plasticity in the central nervous system

Chondroitin sulfate proteoglycans (CSPGs) consist of a core protein and glycosaminoglycan (GAG) chains. There is enormous structural diversity among CSPGs due to variation in the core protein, the number of GAG chains and the extent and position of sulfation. Most CSPGs are secreted from cells and participate in the formation of the extracellular matrix (ECM). CSPGs are able to interact with various growth-active molecules and this may be important in their mechanism of action. In the normal central nervous system (CNS), CSPGs have a role in development and plasticity during postnatal development and in the adult. Plasticity is greatest in the young, especially during critical periods. CSPGs are crucial components of perineuronal nets (PNNs). PNNs have a role in closure of the critical period and digestion of PNNs allows their re-opening. In the adult, CSPGs play a part in learning and memory and the hypothalamo-neurohypophysial system. CSPGs have an important role in CNS injuries and diseases. After CNS injury, CSPGs are the major inhibitory component of the glial scar. Removal of CSPGs improves axonal regeneration and functional recovery. CSPGs may also be involved in the pathological processes in diseases such as epilepsy, stroke and Alzheimer's disease. Several possible methods of manipulating CSPGs in the CNS have recently been identified. The development of methods to remove CSPGs has considerable therapeutic potential in a number of CNS disorders.

Novel sulfated octa- and decasaccharides from squid cartilage chondroitin sulfate E: sequencing and application for determination of the epitope structure of the monoclonal antibody MO-225

A mixture of octa- and decasaccharides obtained by the digestion with the hyaluronidase of chondroitin sulfate E derived from squid cartilage was subfractionated into 20 and 23 different components, respectively, by anion-exchange HPLC. MALDI-TOF/MS was used to assign the sugar and sulfate composition of the putative octa- and decasaccharides, and a disaccharide composition analysis revealed the building blocks to be A- [GlcUAbeta1-3GalNAc(4S)], C- [GlcUAbeta1-3GalNAc(6S)], and E- [GlcUAbeta1-3GalNAc(4S,6S)] units, where 4S and 6S represent 4-O- and 6-O-sulfate, respectively. The sequences of these octa- and decasaccharides were determined at low picomole amounts by a combination of enzymatic digestions with chondroitinases in conjunction with anion-exchange HPLC. Sequencing revealed that each fraction is a mixture of a major component together with one to three minor components, reflecting the heterogeneity of the parent polysaccharide. Among the 11 different octasaccharide sequences reported here, 8 are novel, while all of the 6 decasaccharide sequences are novel, and this is the first report of the sequencing of CS oligosaccharides longer than octasaccharides. The reactivity of the monoclonal antibody MO-225 with octa- and decasaccharides tested with an oligosaccharide microarray revealed that a CS-E decasaccharide is the minimal requirement for antibody recognition. Among the 6 decasaccharides, only E-E-E-E-C was recognized by MO-225, suggesting the requirement of a C-unit at the reducing end and also the importance of chain length, which in turn may indicate the importance of the conformation acquired by this specific sequence for antibody recognition.

Conformational Studies on Five Octasaccharides Isolated from Chondroitin Sulfate Using NMR Spectroscopy and Molecular Modeling

Chondroitin sulfate proteoglycans (CS-PG) are involved in the regulation of the central nervous system in vertebrates due to their presence on cell surfaces and in the extracellular matrix of tissues. The CS moieties are built up from repeating -4)GlcA(beta1-3)GalNAc(beta1- disaccharide units, partly O-sulfated at different positions. The presence of the disulfated disaccharide D-unit, GlcA2S(beta1-3)GalNAc6S, in the CS moiety of the proteoglycan DSD-1-PG/phosphacan, correlates with neurite outgrowth promotion. The binding of monoclonal antibody (mAb) 473HD to DSD-1-PG, reducing neuronal stimulation, is inhibited by shark cartilage CS-D. CS-D is also recognized by two other mAbs, MO-225 and CS-56. Conformational studies were performed using NMR spectroscopy and molecular modeling on five octasaccharides isolated from shark cartilage CS-D. These octasaccharides present different binding properties toward the three mAbs. The combination of the experimental and theoretical approaches revealed that the sulfate group at position 2 of GlcA in disaccharide D and the presence of an exocyclic negative tail in disaccharides C [GlcA(beta1-3)GalNAc6S] and DeltaC [Delta4,5HexA(alpha1-3)GalNAc6S] are important for antibody recognition.

Acceptor specificity of the Pasteurella hyaluronan and chondroitin synthases and production of chimeric glycosaminoglycans

The hyaluronan (HA) synthase, PmHAS, and the chondroitin synthase, PmCS, from the Gram-negative bacterium Pasteurella multocida polymerize the glycosaminoglycan (GAG) sugar chains HA or chondroitin, respectively. The recombinant Escherichia coli-derived enzymes were shown previously to elongate exogenously supplied oligosaccharides of their cognate GAG (e.g. HA elongated by PmHAS). Here we show that oligosaccharides and polysaccharides of certain noncognate GAGs (including sulfated and iduronic acid-containing forms) are elongated by PmHAS (e.g. chondroitin elongated by PmHAS) or PmCS. Various acceptors were tested in assays where the synthase extended the molecule with either a single monosaccharide or a long chain (approximately 10(2-4) sugars). Certain GAGs were very poor acceptors in comparison to the cognate molecules, but elongated products were detected nonetheless. Overall, these findings suggest that for the interaction between the acceptor and the enzyme (a) the orientation of the hydroxyl at the C-4 position of the hexosamine is not critical, (b) the conformation of C-5 of the hexuronic acid (glucuronic versus iduronic) is not crucial, and (c) additional negative sulfate groups are well tolerated in certain cases, such as on C-6 of the hexosamine, but others, including C-4 sulfates, were not or were poorly tolerated. In vivo, the bacterial enzymes only process unsulfated polymers; thus it is not expected that the PmCS and PmHAS catalysts would exhibit such relative relaxed sugar specificity by acting on a variety of animal-derived sulfated or epimerized GAGs. However, this feature allows the chemoenzymatic synthesis of a variety of chimeric GAG polymers, including mimics of proteoglycan complexes.