Alterations in sulfated chondroitin glycosaminoglycans following controlled cortical impact injury in mice

ArticleinThe Journal of Comparative Neurology 520(15):3295-313 · October 2012with11 Reads
DOI: 10.1002/cne.23156 · Source: PubMed
Abstract
Chondroitin sulfate proteoglycans (CSPGs) play a pivotal role in many neuronal growth mechanisms including axon guidance and the modulation of repair processes following injury to the spinal cord or brain. Many actions of CSPGs in the central nervous system (CNS) are governed by the specific sulfation pattern on the glycosaminoglycan (GAG) chains attached to CSPG core proteins. To elucidate the role of CSPGs and sulfated GAG chains following traumatic brain injury (TBI), controlled cortical impact injury of mild to moderate severity was performed over the left sensory motor cortex in mice. Using immunoblotting and immunostaining, we found that TBI resulted in an increase in the CSPGs neurocan and NG2 expression in a tight band surrounding the injury core, which overlapped with the presence of 4-sulfated CS GAGs but not with 6-sulfated GAGs. This increase was observed as early as 7 days post injury (dpi), and persisted for up to 28 dpi. Labeling with markers against microglia/macrophages, NG2+ cells, fibroblasts, and astrocytes showed that these cells were all localized in the area, suggesting multiple origins of chondroitin-4-sulfate increase. TBI also caused a decrease in the expression of aggrecan and phosphacan in the pericontusional cortex with a concomitant reduction in the number of perineuronal nets. In summary, we describe a dual response in CSPGs whereby they may be actively involved in complex repair processes following TBI.
    • "These data are consistent with those showing a lesion-induced up-regulation of NG2 protein in the first posttraumatic week(s) in response to punctate cerebellum lesions (Levine 1994), SCI (Jones et al., 2002) or entorhinal cortex lesion (Dehn et al., 2006). Using a similar CCI model as in our study, an enrichment of NG2 protein in the pericontusional tissue has been reported up to 4 weeks after injury (Yi et al., 2012) which corresponds to the latest time point in our study. NG2-expressing cells have been shown to proliferate 1d to 3d after experimental TBI (Susarla et al., 2014). "
    [Show abstract] [Hide abstract] ABSTRACT: Traumatic brain injury (TBI) is a major cause of death and disability. The underlying pathophysiology is characterized by secondary processes including neuronal death and gliosis. To elucidate the role of the NG2 proteoglycan we investigated the response of NG2-knockout mice (NG2-KO) to TBI. Seven days after TBI behavioral analysis, brain damage volumetry and assessment of blood brain barrier integrity demonstrated an exacerbated response of NG2-KO compared to wild-type (WT) mice. Reactive astrocytes and expression of the reactive astrocyte and neurotoxicity marker Lcn2 (Lipocalin-2) were increased in the perilesional brain tissue of NG2-KO mice. In addition, microglia/macrophages with activated morphology were increased in number and mRNA expression of the M2 marker Arg1 (Arginase 1) was enhanced in NG2-KO mice. While TBI-induced expression of pro-inflammatory cytokine genes was unchanged between genotypes, PCR array screening revealed a marked TBI-induced up-regulation of the C-X-C motif chemokine 13 gene Cxcl13 in NG2-KO mice. CXCL13, known to attract immune cells to the inflamed brain, was expressed by activated perilesional microglia/macrophages seven days after TBI. Thirty days after TBI, NG2-KO mice still exhibited more pronounced neurological deficits than WT mice, up-regulation of Cxcl13, enhanced CD45+ leukocyte infiltration and a relative increase of activated Iba-1+/CD45+ microglia/macrophages. Our study demonstrates that lack of NG2 exacerbates the neurological outcome after TBI and associates with abnormal activation of astrocytes, microglia/macrophages and increased leukocyte recruitment to the injured brain. These findings suggest that NG2 may counteract neurological deficits and adverse glial responses in TBI. GLIA 2015.
    Article · Dec 2015
    • "Right frontal ballistic injury was produced by the Dragonfly Variable Pressure Waveform Generator (model no. HPD-1700; Dragonfly Inc., Ridgeley, West Virginia, USA) as detailed (Yi et al. 2012). Injury was induced (10% brain volume) by a high speed, specially designed probe into the hippocampal region of the brain, and rapid inflation of an attached balloon mimicked the temporary cavity induced by a penetrating bullet. "
    [Show abstract] [Hide abstract] ABSTRACT: In an established rat model of penetrating ballistic-like brain injury (PBBI), arylsulfatase B (ARSB; N-acetylgalactosamine 4-sulfatase) activity was significantly reduced at the ipsilateral site of injury, but unaffected at the contralateral site or in sham controls. In addition, the ARSB substrate chondroitin 4-sulfate (C4S) and total sulfated glycosaminoglycans increased. The mRNA expression of chondroitin 4-sulfotransferase 1 (C4ST1; CHST11) and the sulfotransferase activity rose at the ipsilateral site of injury (PBBI-I), indicating contributions from both increased production and reduced degradation to the accumulation of C4S. In cultured, fetal rat astrocytes, following scratch injury, the ARSB activity declined and the nuclear hypoxia inducible factor (HIF)-1α increased significantly. In contrast, sulfotransferase activity and chondroitin 4-sulfotransferase expression increased following astrocyte exposure to TGF-β1, but not following scratch. These different pathways by which C4S increased in the cell preparations were both evident in the response to injury in the PBBI-I model. Hence, findings support effects of injury due to mechanical disruption inhibiting ARSB and to chemical mediation by TGF-β1 increasing CHST11 expression and sulfotransferase activity. The increase in C4S following TBI is due to contributions from impaired degradation and enhanced synthesis of C4S which combine in the pathogenesis of the glial scar. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
    Full-text · Article · May 2015
    • "TBI-reactive changes in CPSG production are not uniform throughout the lesion area. For example, while the lesion core of a cortical contusion contains and is immediately surrounded by deposits of sulfated proteoglycans, there is a significant decrease in CSPGs in the perilesion perimeter (Harris et al., 2009Harris et al., , 2010 Yi et al., 2012). Indeed, astrocytes surrounding traumatic brain lesions are highly immuno-reactive for the CSPGs versican, neurocan and aggrecan (Harris et al., 2009 ), but appear to downregulate their expression further from the injury site. "
    [Show abstract] [Hide abstract] ABSTRACT: Astrocytes sense changes in neural activity and extracellular space composition. In response, they exert homeostatic mechanisms critical for maintaining neural circuit function, such as buffering neurotransmitters, modulating extracellular osmolarity and calibrating neurovascular coupling. In addition to upholding normal brain activities, astrocytes respond to diverse forms of brain injury with heterogeneous and progressive changes of gene expression, morphology, proliferative capacity and function that are collectively referred to as reactive astrogliosis. Traumatic brain injury (TBI) sets in motion complex events in which noxious mechanical forces cause tissue damage and disrupt central nervous system (CNS) homeostasis, which in turn trigger diverse multi-cellular responses that evolve over time and can lead either to neural repair or secondary cellular injury. In response to TBI, astrocytes in different cellular microenvironments tune their reactivity to varying degrees of axonal injury, vascular disruption, ischemia and inflammation. Here we review different forms of TBI-induced astrocyte reactivity and the functional consequences of these responses for TBI pathobiology. Evidence regarding astrocyte contribution to post-traumatic tissue repair and synaptic remodeling is examined, and the potential for targeting specific aspects of astrogliosis to ameliorate TBI sequelae is considered. Copyright © 2015. Published by Elsevier Inc.
    Full-text · Article · Mar 2015
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