Focal cerebral ischemia induces changes in both MMP-13 and aggrecan around individual neurons

Extracellular Matrix Regulation in Physiology and in Brain Disease

The extracellular matrix (ECM) surrounds cells in the brain, providing structural and functional support. Emerging studies demonstrate that the ECM plays important roles during development, in the healthy adult brain, and in brain diseases. The aim of this review is to briefly discuss the physiological roles of the ECM and its contribution to the pathogenesis of brain disease, highlighting the gene expression changes, transcriptional factors involved, and a role for microglia in ECM regulation. Much of the research conducted thus far on disease states has focused on "omic" approaches that reveal differences in gene expression related to the ECM. Here, we review recent findings on alterations in the expression of ECM-associated genes in seizure, neuropathic pain, cerebellar ataxia, and age-related neurodegenerative disorders. Next, we discuss evidence implicating the transcription factor hypoxia-inducible factor 1 (HIF-1) in regulating the expression of ECM genes. HIF-1 is induced in response to hypoxia, and also targets genes involved in ECM remodeling, suggesting that hypoxia could contribute to ECM remodeling in disease conditions. We conclude by discussing the role microglia play in the regulation of the perineuronal nets (PNNs), a specialized form of ECM in the central nervous system. We show evidence that microglia can modulate PNNs in healthy and diseased brain states. Altogether, these findings suggest that ECM regulation is altered in brain disease, and highlight the role of HIF-1 and microglia in ECM remodeling.

The effects of CoQ10 supplement on matrix metalloproteinases, oxidative DNA damage and pro-inflammatory cytokines in testicular ischaemia/reperfusion injury in rats

We aimed to study the effect of coenzyme Q10 on pro-inflammatory cytokine, matrix metalloproteinase, oxidative DNA damage, caspase 3 and caspase 8 in ischaemia/reperfusion injury led to by testicular torsion/detorsion. Our research is a controlled experimental animal research using rats. This study was conducted with fifty-six adult male Albino Wistar rats. Interleucine-1β, 2, 6, 10, tumour necrosis factor-α, matrix metalloproteinase-2, 3, 9, 13, tissue inhibitor matrix metalloproteinase-1, 2, malondialdehyde and leucocyte 8-hydroxy-2-deoxy guanosine/10⁶ deoxyguanosine was detected in serum and tissue samples. In addition, immunohistochemical analysis of caspase 2 and caspase 8 was performed. In testicular I/R injury, especially 24 hr after detorsion, oxidative damage pro-inflammatory cytokines and matrix metalloproteinases were increased. At the coenzyme Q10 group, a meaningful decrease was observed in these parameters. In addition, a decrease in the expression of caspase3 and caspase 8 was viewed in coenzyme Q10-treated groups. The coenzyme Q10 has beneficial effects on oxidative damage, pro-inflammatory cytokine levels, remodelling of extracellular matrix and apoptosis in testicular I/R injury.

Spreading Depressions and Periinfarct Spreading Depolarizations in the Context of Cortical Plasticity

Studies of cortical function-recovery require a comparison between normal and post-stroke conditions that lead to changes in cortical metaplasticity. Focal cortical stroke impairs experience-dependent plasticity in the neighboring somatosensory cortex and usually evokes periinfarct depolarizations (PiDs) - spreading depression-like waves. Experimentally induced spreading depressions (SDs) affect gene expression and some of these changes persist for at least 30 days. In this study we compare the effects of non-stroke depolarizations that impair cortical experience-dependent plasticity to the effects of stroke, by inducing experience-dependent plasticity in rats with SDs or PiDs by a month of contralateral partial whiskers deprivation. We found that whiskers' deprivation after SDs resulted in normal cortical representation enlargement suggesting that SDs and PiDs depolarization have no influence on experience-dependent plasticity cortical map reorganization. PiDs and the MMP-9, -3, -2 or COX-2 proteins, which are assumed to influence metaplasticity in rats after stroke were compared between SDs induced by high osmolarity KCl solution and the PiDs that followed cortical photothrombotic stroke (PtS). We found that none of these factors directly caused cortical post-stroke metaplasticity changes. The only significant difference between stoke and induced SD was a greater imbalance in interhemispheric activity equilibrium after stroke. The interhemispheric interactions that were modified by stroke may therefore be promising targets for future studies of post-stroke experience-dependent plasticity and of recuperation studies.

Ischemic-Reperfusion Injury Increases Matrix Metalloproteinases and Tissue Metalloproteinase Inhibitors in Fetal Sheep Brain

Hypoxic-ischemic brain injury is a leading cause of neurodevelopmental morbidities in preterm and full-term infants. Blood-brain barrier dysfunction represents an important component of perinatal hypoxic-ischemic brain injury. The extracellular matrix (ECM) is a vital component of the blood-brain barrier. Matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinases (TIMPs) are important ECM components. They contribute to brain development, blood-brain barrier maintenance, and to regenerative and repair processes after hypoxic-ischemic brain injury. We hypothesized that ischemia at different durations of reperfusion affects the ECM protein composition of MMPs and TIMPs in the cerebral cortex of fetal sheep. Cerebral cortical samples were snap-frozen from sham control fetuses at 127 days of gestation and from fetuses after exposure to 30-min carotid occlusion and 4-, 24-, and 48-h of reperfusion. Protein expression of MMP-2, -8, -9, and -13 and TIMP-1, -2, -3, and -4 was measured by Western immunoblotting along with the gelatinolytic activity of MMP-2 and MMP-9 by zymography. The expression of MMP-8 was increased (Kruskal-Wallis, p = 0.04) in fetuses 48 h after ischemia. In contrast, changes were not observed in the protein expression of MMP-2, -9, or -13. The gelatinolytic activity of pro-MMP-2 was increased (ANOVA, p = 0.02, Tukey HSD, p = 0.05) 24 h after ischemia. TIMP-1 and -3 expression levels were also higher (TIMP-1, ANOVA, p = 0.003, Tukey HSD, p = 0.01; TIMP-3, ANOVA, p = 0.006, Tukey HSD, p = 0.01) 24 h after ischemia compared with both the sham controls and with fetuses exposed to 4 h of reperfusion. The changes in the expression of TIMP-1, -2, and -3 correlated with the changes in the MMP-8 and -13 protein expression. We speculate that regulation of MMP-8, MMP-13, and TIMPs contributes to ECM remodeling after is chemic-reperfusion injury in the fetal brain.

Trajectory of Parvalbumin Cell Impairment and Loss of Cortical Inhibition in Traumatic Brain Injury

Many neuropsychiatric symptoms that follow traumatic brain injury (TBI), including mood disorders, sleep disturbance, chronic pain, and posttraumatic epilepsy (PTE) are attributable to compromised cortical inhibition. However, the temporal trajectory of cortical inhibition loss and its underlying mechanisms are not known. Using paired-pulse transcranial magnetic stimulation (ppTMS) and immunohistochemistry, we tracked functional and cellular changes of cortical inhibitory network elements after fluid-percussion injury (FPI) in rats. ppTMS revealed a progressive loss of cortical inhibition as early as 2 weeks after FPI. This profile paralleled the increasing levels of cortical oxidative stress, which was accompanied by a gradual loss of parvalbumin (PV) immunoreactivity in perilesional cortex. Preceding the PV loss, we identified a degradation of the perineuronal net (PNN)-a specialized extracellular structure enwrapping cortical PV-positive (PV+) inhibitory interneurons which binds the PV+ cell maintenance factor, Otx2. The trajectory of these impairments underlies the reduced inhibitory tone, which can contribute to posttraumatic neurological conditions, such as PTE. Taken together, our results highlight the use of ppTMS as a biomarker to track the course of cortical inhibitory dysfunction post-TBI. Moreover, the neuroprotective role of PNNs on PV+ cell function suggests antioxidant treatment or Otx2 enhancement as a promising prophylaxis for post-TBI symptoms.

Ischemic injury leads to extracellular matrix alterations in retina and optic nerve

Retinal ischemia occurs in a variety of eye diseases. Restrained blood flow induces retinal damage, which leads to progressive optic nerve degeneration and vision loss. Previous studies indicate that extracellular matrix (ECM) constituents play an important role in complex tissues, such as retina and optic nerve. They have great impact on de- and regeneration processes and represent major candidates of central nervous system glial scar formation. Nevertheless, the importance of the ECM during ischemic retina and optic nerve neurodegeneration is not fully understood yet. In this study, we analyzed remodeling of the extracellular glycoproteins fibronectin, laminin, tenascin-C and tenascin-R and the chondroitin sulfate proteoglycans (CSPGs) aggrecan, brevican and phosphacan/RPTPβ/ζ in retinae and optic nerves of an ischemia/reperfusion rat model via quantitative real-time PCR, immunohistochemistry and Western blot. A variety of ECM constituents were dysregulated in the retina and optic nerve after ischemia. Regarding fibronectin, significantly elevated mRNA and protein levels were observed in the retina following ischemia, while laminin and tenascin-C showed enhanced immunoreactivity in the optic nerve after ischemia. Interestingly, CSPGs displayed significantly increased expression levels in the optic nerve. Our study demonstrates a dynamic expression of ECM molecules following retinal ischemia, which strengthens their regulatory role during neurodegeneration.

Increased metalloproteinase activity in the hippocampus following status epilepticus

Increased neuronal plasticity and neuronal cell loss has been implicated in the development of epilepsy following injury. Parvalbumin fast spiking inhibitory interneurons have a robust extracellular matrix coating their cell bodies and the proximal dendrites called the perineuronal net (PNN). The role of the PNN is not clear but it has been implicated in closing of the critical period, altering seizure thresholds and providing neuronal protection from oxidative stress. The PNN is susceptible to degradation following a prolonged seizure and there is an increase in proteolytic-fragments of the PNN enriched proteoglycan aggrecan (Dzwonek et al., 2004). Here we demonstrate an increase in matrix metalloproteinase (MMP) activity in the hippocampus following status epilepticus (SE). We further assessed MMP3 and 13, two of 24 identified MMPs, both MMP3 and 13 mRNA increase in the hippocampus after SE and MMP13 activity increases by functional assay as well as it co-localizes with PNN in rat brain. In contrast, two of the brain expressed ADAMTS (A Disintegrin And Metalloproteinase with ThromboSpondin motifs) also implicated in aggrecan degradation, did not consistently increase following SE though ADAMTS4 is highly expressed in glia and ADAMTS5 in neuronal cell bodies and their processes. The increase in MMP activity following SE suggests that in the future studies, MMP inhibitors are candidates for blocking PNN degradation and assessing the role of the PNN loss in epileptogenesis and cellular function.

Loss of Interneuron-Derived Collagen XIX Leads to a Reduction in Perineuronal Nets in the Mammalian Telencephalon

Perineuronal nets (PNNs) are lattice-like supramolecular assemblies of extracellular glycoproteins that surround subsets of neuronal cell bodies in the mammalian telencephalon. PNNs emerge at the end of the critical period of brain development, limit neuronal plasticity in the adult brain, and are lost in a variety of complex brain disorders diseases, including schizophrenia. The link between PNNs and schizophrenia led us to question whether neuronally expressed extracellular matrix (ECM) molecules associated with schizophrenia contribute to the assembly of these specialized supramolecular ECM assemblies. We focused on collagen XIX-a minor, nonfibrillar collagen expressed by subsets of telencephalic interneurons. Genetic alterations in the region encoding collagen XIX have been associated with familial schizophrenia, and loss of this collagen in mice results in altered inhibitory synapses, seizures, and the acquisition of schizophrenia-related behaviors. Here, we demonstrate that loss of collagen XIX also results in a reduction of telencephalic PNNs. Loss of PNNs was accompanied with reduced levels of aggrecan (Acan), a major component of PNNs. Despite reduced levels of PNN constituents in collagen XIX-deficient mice ( col19a1-/-), we failed to detect reduced expression of genes encoding these ECM molecules. Instead, we discovered a widespread upregulation of extracellular proteases capable of cleaving Acan and other PNN constituents in col19a1-/- brains. Taken together, these results suggest a mechanism by which the loss of collagen XIX speeds PNN degradation and they identify a novel mechanism by which the loss of collagen XIX may contribute to complex brain disorders.

Plasma Matrix Metalloproteinases in Patients With Stroke During Intensive Rehabilitation Therapy

OBJECTIVE

To study plasma levels of matrix metalloproteinases (MMPs) as potential markers of recovery during intensive rehabilitation therapy (IRT) after stroke.

DESIGN

Prospective and descriptive 3-month follow-up study.

SETTING

Rehabilitation unit and research center.

PARTICIPANTS

Patients with first-ever ischemic stroke (n=15) enrolled to IRT (≥3h/d and 5d/wk) and healthy volunteers (n=15) (N=30).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

The primary outcome was to measure plasma MMP3, MMP12, and MMP13 levels and evaluate potential associations with motor/functional scales using a battery of tests (National Institutes of Health Stroke Scale, modified Rankin scale, Barthel Index, Fugl-Meyer Assessment, Functional Ambulation Categories, Medical Research Council scale, Chedoke Arm and Hand Activity Inventory, and the 10-m walk test) before IRT and at 1- and 3-month follow-ups. The secondary outcome was to evaluate the use of these MMPs as biomarkers as predictors of patient's outcome.

RESULTS

MMP levels remained stable during the study period and were similar to those in the healthy volunteer group. However, baseline MMP12 and MMP13 levels were strongly associated with stroke severity and were found to be elevated in those patients with the poorest outcomes. Interestingly, plasma MMP3 was independent of baseline stroke characteristics but was found to be increased in patients with better motor/functional recovery and in patients with larger improvements during rehabilitation.

CONCLUSIONS

MMPs might act as biologic markers of recovery during rehabilitation therapy related to their roles in both injury and tissue remodeling. Future confirmatory investigations in multicenter studies are warranted by our data.

Matrix metalloproteinases as promising regulators of axonal regrowth in the injured adult zebrafish retinotectal system

Overcoming the failure of axon regeneration in the mammalian central nervous system (CNS) after injury remains a major challenge, which makes the search for proregenerative molecules essential. Matrix metalloproteinases (MMPs) have been implicated in axonal outgrowth during CNS development and show increased expression levels during vertebrate CNS repair. In mammals, MMPs are believed to alter the suppressive extracellular matrix to become more permissive for axon regrowth. We investigated the role of MMPs in axonal regeneration following optic nerve crush (ONC) in adult zebrafish, which fully recover from such injuries due to a high intrinsic axon growth capacity and a less inhibitory environment. Lowering general retinal MMP activity through intravitreal injections of GM6001 after ONC strongly reduced retinal ganglion cell (RGC) axonal regrowth, without influencing RGC survival. Based on a recently performed transcriptome profiling study, the expression pattern of four MMPs after ONC was determined via combined use of western blotting and immunostainings. Mmp-2 and -13a were increasingly present in RGC somata during axonal regrowth. Moreover, Mmp-2 and -9 became upregulated in regrowing RGC axons and inner plexiform layer (IPL) synapses, respectively. In contrast, after an initial rise in IPL neurites and RGC axons during the injury response, Mmp-14 expression decreased during regeneration. Altogether, a phase-dependent expression pattern for each specific MMP was observed, implicating them in axonal regrowth and inner retina remodeling after injury. In conclusion, these data suggest a novel, neuron-intrinsic function for multiple MMPs in axon regrowth that is distinct from breaking down environmental barriers. J. Comp. Neurol. 524:1472-1493, 2016. © 2015 Wiley Periodicals, Inc.

Analysis of the expression of nine secreted matrix metalloproteinases and their endogenous inhibitors in the brain of mice subjected to ischaemic stroke

Matrix metalloproteinases (MMPs) are a family of more than twenty secreted and cell-surface endopeptidases. Among them, MMP2, MMP3 and MMP9 are involved in blood-brain barrier injury and neuronal death after cerebral ischaemia. On the other hand, very little is known about the expression of the other secreted MMPs. Herein, we compared the global changes in MMP1, MMP2, MMP3, MMP7, MMP8, MMP9, MMP10, MMP12 and MMP13, and their endogenous inhibitors TIMP1 and TIMP2, both at the mRNA and protein levels, during the hyperacute (6 h), acute (24 h) and subacute (72 h) stages following transient focal cerebral ischaemia and treatment with recombinant tissue plasminogen activator (rtPA). We observed a significant increase in MMP1, MMP2, MMP9, MMP10, MMP13 and TIMP1 levels during the acute stage of reperfusion, which was further amplified during the subacute stage for MMP1, MMP2, MMP10 and TIMP1. In general, no change of MMP3, MMP7, MMP8, MMP12 and TIMP2 was observed. However, rtPA treatment induced a rapid increase in MMP1/TIMP2, MMP2/TIMP2, MMP8/TIMP2 and MMP9/TIMP2 ratios during the hyperacute stage of reperfusion compared to saline treatment, which may have potential implications in the early disruption of the blood-brain barrier after rtPA treatment.

Inflammation modulates expression of laminin in the central nervous system following ischemic injury

BACKGROUND

Ischemic stroke induces neuronal death in the core of the infarct within a few hours and the secondary damage in the surrounding regions over a long period of time. Reduction of inflammation using pharmacological reagents has become a target of research for the treatment of stroke. Cyclooxygenase 2 (COX-2), a marker of inflammation, is induced during stroke and enhances inflammatory reactions through the release of enzymatic products, such as prostaglandin (PG) E2.

METHODS

Wild-type (WT) and COX-2 knockout (COX-2KO) mice were subjected to middle cerebral artery occlusion (MCAO). Additionally, brain slices derived from these mice or brain microvascular endothelial cells (BMECs) were exposed to oxygen-glucose deprivation (OGD) conditions. The expression levels of extracellular matrix (ECM) proteins were assessed and correlated with the state of inflammation.

RESULTS

We found that components of the ECM, and specifically laminin, are transiently highly upregulated on endothelial cells after MCAO or OGD. This upregulation is not observed in COX-2KO mice or WT mice treated with COX-2 inhibitor, celecoxib, suggesting that COX-2 is associated with changes in the levels of laminins.

CONCLUSIONS

Taken together, we report that transient ECM remodeling takes place early after stroke and suggest that this increase in ECM protein expression may constitute an effort to revascularize and oxygenate the tissue.

Matrix metalloproteinases at key junctions in the pathomechanism of stroke

Matrix metalloproteinases play a crucial role in the remodelling of the extracellular matrix through direct degradation of its structural proteins and control of extracellular signalling. The most common cause of ischemic brain damage is an atherothrombotic lesion in the supplying arteries. The progress of the atherosclerotic plaque development and the related thrombotic complications are mediated in part by matrix metalloproteinases. In addition to their role in the underlying disease, various members of this protease family are upregulated in the acute phase of ischemic brain damage as well as in the post-ischemic brain recovery following stroke. This review summarizes the current understanding of the matrix metalloproteinase-related molecular events at three stages of the ischemic cerebrovascular disease (in the atherosclerotic plaque, in the neurovascular unit of the brain and in the regenerating brain tissue).

Matrix metalloproteinases as drug targets in ischemia/reperfusion injury

Deficient blood supply (ischemia) is a common consequence of some surgical procedures and certain pathologies. Once blood circulation is re-established (reperfusion), a complex series of events results in recruitment of inflammatory cells, rearrangement of the extracellular matrix and induction of cell death, which lead to organ dysfunction. Although ischemia/reperfusion (I/R) injury is an important cause of death, there is no effective therapy targeting the molecular mechanism of disease progression. Matrix metalloproteinases (MMPs), which are important regulators of many cellular activities, have a central role in disease progression after I/R injury, as suggested by numerous studies using MMP inhibitors or MMP-deficient mice. Here, we review the involvement of MMP activity in the various processes following I/R injury and the therapeutic potential of MMP inhibition.

Disturbance of perineuronal nets in the perilesional area after photothrombosis is not associated with neuronal death

Perineuronal nets (PNNs) are a condensed form of extracellular matrix that covers the surface of a subset of neurons. Their presence limits neuronal plasticity and may protect neurons against harmful agents. Here we analyzed the relationship between spatiotemporal changes in PNN expression and cell death markers after focal cortical photothrombotic stroke in rats. We registered a substantial decrease in PNN density using Wisteria floribunda agglutinin staining and CAT-315 and brevican immunoreactivity; the decrease occurred not only in the lesion core but also in the perilesional and remote cortex as well as in homotopic contralateral cortical regions. Fluoro Jade C and TUNEL staining in perilesional and remote areas, however, showed a low density of dying cells. Our results suggest that the PNN reduction was not a result of cellular death and could be considered an attempt to create conditions favorable for synaptic remodeling.

Vascular MMP-9/TIMP-2 and neuronal MMP-10 up-regulation in human brain after stroke: a combined laser microdissection and protein array study

Matrix Metalloproteinases (MMPs) play an important role in brain injury after ischemic stroke. In the present study, we aimed to assess the global expression of MMP-Family proteins in the human brain after stroke by using a combination of Searchlight Protein Array and Laser Microdissection to determine their cellular origin. This study demonstrated that MMP-1, MMP-2, MMP-3, MMP-8, MMP-9, MMP-10, MMP-13, and TIMP-1 were upregulated in the infarcted tissue compared to healthy control areas. Using laser microdissection we obtained specific neuronal and vascular populations from both infarcted and control areas. From these fractions, we showed that MMP-9 and TIMP-2 were highly produced in brain microvessels while MMP-10 was notably increased in neurons of the ischemic brain but not in healthy areas. These findings demonstrate a selective cell-dependent MMP secretion, opening the possibility of selectively targeting specific MMPs for neuroprotection or vasculoprotection following stroke.

Matrix metalloproteinase-13 is activated and is found in the nucleus of neural cells after cerebral ischemia

Matrix metalloproteinases (MMPs) have been implicated in the pathophysiology of ischemic stroke. In this study, we investigated the time course of gelatinolytic activation in a rat model of permanent ischemia. We observed an activation of MMPs as early as 30 mins after the ischemic insult, mainly in the nuclei of brain cells. Besides, we explored MMP-13 expression in brain samples of the animal model and stroke deceased patients. We observed an upregulation of active MMP-13 in rat brains (P<0.05) after 90 mins of cerebral ischemia. Human infarct/periinfarct samples also showed higher levels of active MMP-13 (P<0.05) compared with contralateral ones. Interestingly, we found that MMP-13 colocalized with 46-diamidino-2-phenyl indole signal by immunohistochemistry in both humans and rats, suggesting an intranuclear localization for MMP-13. Immunohistochemistry also revealed that MMP-13 was mainly produced by neurons, in both species, but also by oligodendrocytes in rats, and by astrocytes in humans. Finally we subjected a rat primary neuronal culture to oxygen and glucose deprivation (OGD) and we reproduced the nuclear translocation of MMP-13 in vitro. Nuclear extracts from cells confirmed upregulation of active MMP-13 after OGD (P<0.05). These results suggest that MMP-13 activation and its nuclear translocation is an early consequence of an ischemic stimulus.

Endocannabinoid regulation of matrix metalloproteinases: implications in ischemic stroke

Stroke is a major cause of morbidity and mortality and follows heart disease and cancer as the third leading cause of death in Western societies [1]. Despite many advances in stroke research and pharmacotherapy, clinical treatment of this debilitating disorder is still inadequate. Recent findings from several laboratories have identified the endocannabinoid signaling pathway, comprised of the endocannabinoid agonist anandamide and its pharmacological targets, CB1 and CB2 cannabinoid receptors and associated anandamide receptors, as a physiological system with capacity to mitigate cardiovascular and cerebrovascular disorders through neuronal and endothelial actions. Variability in experimental stroke models and modes of outcome evaluation, however, have provoked controversy regarding the precise roles of endocannabinoid signals in mediating neural and/or vascular protection versus neurovascular damage. Clinical trials of the CB1 antagonist rimonabant demonstrate that modulation of endocannabinoid signaling during metabolic regulation of vascular disorders can significantly impact clinical outcomes, thus providing strong argument for therapeutic utility of endocannabinoids and/or cannabinoid receptors as targets for therapeutic intervention in cases of stroke and associated vascular disorders. The purpose of this review is to provide updated information from basic science and clinical perspectives on endocannabinoid ligands and their effects in the pathophysiologic genesis of stroke. Particular emphasis will be placed on the endocannabinoids anandamide and 2-arachidonylglycerol and CB1 receptor-mediated mechanisms in the neurovascular unit during stroke pathogenesis. Deficiencies in our knowledge of endocannabinoids in the etiology and pathogenesis of stroke, caveats and limitations of existing studies, and future directions for investigation will be addressed.

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.