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Over the last twenty years chondroitin sulfate (CS) has become a focus of interest of neuroscience due to its indubitable role in shaping axonal growth, synaptic plasticity and glial scar forming. Various patterns of sulfation give rise to various CS molecules with different properties that are capable of interactions with a plethora of molecules, including growth factors, receptors and guidance molecules. The involvement of CS chains has been implicated in visual critical period regulation, memory formation, spinal cord regeneration. As part of proteoglycan molecules, they are widely expressed in the central nervous system, however, little is known about the enzymatic machinery responsible for CS synthesis and degradation. In this review we attempt to extract and collect the available information concerning the expression and function of enzymes of CS metabolism in the brain.
INTRODUCTION: Perineuronal nets (PNNs) are brain extracellular matrix (ECM) formations enveloping selected neurons. They stabilize synaptic connections, thus limiting plasticity. Decrease in PNNs densities was observed after stroke and may be considered an attempt to create favorable conditions for neuroplasticity. PNNs are composed mainly of sugar moieties, therefore we hypothesize the role of polysaccharide modifying enzymes in observed phenomenon. AIM(S): We investigated the changes in gene expression and protein localization of enzymes involved in hyaluronic acid and chondroitin sulfate metabolism. METHOD(S): The expression of genes was analyzed in the remote area at 7 days (d), 1 and 3 months (m) after unilateral photothrombosis. To investigate spatiotemporal mRNA expression qPCR method was employed. Immunohistochemical staining was used to analyze cellular localization of investigated enzymes. RESULTS: We observed increased expression of hyaluronan synthase 2 (HAS2) 7d post-stroke within both hemispheres. Also, changes in mRNA level of chondroitin sulfate synthesis-mediating enzymes occurred, namely, elevation of beta-1,3-glucuronyltransferase 2 (B3GAT2) and simultaneous decrease in B3GAT1 and B3GAT3 expression. Progressive reduction of chondroitin sulfate N-acetylgalactosaminyltransferase 1 (ChGn-1) expression was observed from 7d to 1 month in the contralateral homotopic area. Moreover, 7d after stroke decrease in chondroitin-4-sulfotranseferase 1 (C4ST1) accompanied by increase in arylsulfatase B (ARSB) mRNA level was observed. Importantly, protein of investigated enzymes, which mRNA level alteration occurred at shorter time point, were still observed 1m after stroke. CONCLUSIONS: Obtained data indicate prolonged time window for modification of polysaccharide components of the brain ECM that may affect rearrangement of synaptic connections after stroke. FINANCIAL SUPPORT: This work was supported by National Science Centre (Poland) grants: 2012/05/B/ NZ3/00851 and 2015/17/N/NZ3/02244.
BACKGROUND AND AIMS: Perineuronal nets (PNNs) are complex structures of the nervous system extracellular matrix, composed of hyaluronic acid and chondroitin sulfate proteoglycans. PNNs surround mostly the subset of parvalbumin-expressing interneurons by enwrapping their cell body and proximal dendrites. Their presence stabilizes existing synapses and limits neuronal plasticity. Mechanisms that regulate PNNs expression remain unclear. Changes in PNNs expression are observed in perilesional area after photothrombosis and can be considered an attempt to create conditions favorable for synaptic remodeling. We hypothesize that they may result from the activity of endogenous glycolytic enzymes. METHODS: In the present study, employing quantitative RT-qPCR, we analyzed the expression of genes coding for hyaluronic acid synthesizing and degrading enzymes in cortical region of the perilesional area at 1 h, 24 h and 7 days after photothrombotic stroke. RESULTS: Analysis revealed substantial increase in hyaluronidase 1 (HYAL1) expression level in comparison to homotopic contralateral cortical region and control animals. The rise was recognized at 24 h after stroke and maintained up to 7 days after stroke. No change in expression level of HYAL2 was detected. While 24 h after photothrombosis the elevation in hyaluronic acid synthase 2 (HAS2) expression level was observed, the decrease in HAS3 expression level occurred. The expression level of HAS1 maintained unchanged after stroke. CONCLUSIONS: The obtained data indicate photothrombotic stroke-evoked modification of hyaluronic acid component of PNNs in perilesional area. The results show parallel processes of degradation and synthesis at 24 h, which may exert different effects on neuronal plasticity.  This work was supported by NCN grant 2012/05/B/NZ3/00851.
The distribution and density of cells enwrapped with perineuronal nets (PNs) were examined in the neocortex after unilateral photothrombotic stroke. After different survival times PNs was visualized using Wisteria fl oribunda aglutinin (WFA) staining in the infarct core, peri-infarct and remote cortical areas. Sham operated rats and contralateral hemisphere to the stroke site from experimental rats served as controls. In the infarct core, 4 h after stroke only few cells enwrapped with PNs could be detected and none of numerous dying cells present showed PNs, as revealed by double staining (WFA and FJ-C). No cells with PNs were found 24 h after stroke. In the peri-infarct area, dramatic loss of PNs-enwrapped cells occurred (96%) as compared with the contralateral site, and such cells were almost absent after 24 h. However, 30 days after stroke, a signifi cant number of cells with PNs reappeared. In remote cortical areas, 4h after stroke a reduction in the number of cells with PNs was observed. After 24 h the loss of PNs-enwrapped cells was profound (63%) in comparison to intact hemisphere. However, 7d after stroke complete restoration of the number of cells enwrapped with PNs took place. The density of cells with PNs was similar to that found in the contralateral site and in sham operated rats. These results showed the wide spreading and transient effect of photothrombosis on PNs in remote cortical areas. Supported by MNiSW Grant N3030300832/0474 and statutory funds.
Perineuronal net (PN), a lattice-like structure surrounding certain neurons, represents a special form of extracellular matrix of the brain. The role of this structure remains elusive. It has been suggested to regulate neuronal plasticity, accumulate trophic molecules and protect neurons from damaging factors. Here we studied whether PN-enwrapped neurons are protected against ischemic injury. To this aim we performed cortical photothrombotic stroke in rats and investigated PNs and their co-localization with Fluoro Jade C (FJ), a marker of rapid cell death. We found that in the ischemic core 4 h after the stroke still PNs were observable, none of them around FJ-positive neurons. No PNs were detected after 24 h. In the peri-infarct area, a huge loss of PNs was observed 24 h after stroke, followed by a partial restoration 30 days post-infarct. Similar effect was found in remote cortical areas, except that in this case the restoration was almost complete already 7 days after stroke. No FJ staining was observed outside ischemic core. These results suggest that in areas that are not directly damaged, ischemic insult disrupts PNs but the neurons survive this disruption. Supported by MNiSW Grant N3030300832/0474.
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