The structure and function of tenascins in the nervous system

Substrate-bound and soluble domains of tenascin-C regulate differentiation, proliferation and migration of neural stem and progenitor cells

Introduction

The lack of regenerative capacity of the central nervous system is one of the major challenges nowadays. The knowledge of guidance cues that trigger differentiation, proliferation, and migration of neural stem and progenitor cells is one key element in regenerative medicine. The extracellular matrix protein tenascin-C (Tnc) is a promising candidate to regulate cell fate due to its expression in the developing central nervous system and in the adult neural stem cell niches. Of special interest are the alternatively spliced fibronectin type III (FnIII) domains of Tnc whose combinatorial diversity could theoretically generate up to 64 isoforms in the mouse. A total of 27 isoforms have already been discovered in the developing brain, among others the domain combinations A1D, CD, and A124BCD.

Methods

In the present study, these domains as well as the combination of the constitutively expressed FnIII domains 7 and 8 (78) were expressed in Chinese hamster ovary cells as pseudo-antibodies fused to the Fc-fragment of a human immunoglobulin G antibody. The fusion proteins were presented to primary mouse neural stem/progenitor cells (NSPCs) grown as neurospheres, either as coated culture substrates or as soluble additives in vitro. The influence of the domains on the differentiation, proliferation and migration of NSPCs was analyzed.

Results

We observed that the domain combination A124BCD promoted the differentiation of neurons and oligodendrocytes, whereas the domain A1D supported astrocyte differentiation. The constitutively expressed domain 78 had a proliferation and migration stimulating impact. Moreover, most effects were seen only in one of the presentation modes but not in both, suggesting different effects of the Tnc domains in two- and three-dimensional cultures.

Discussion

This knowledge about the different effect of the Tnc domains might be used to create artificial three-dimensional environments for cell transplantation. Hydrogels spiked with Tnc-domains might represent a promising tool in regenerative medicine.

Biology of Tenascin C and its Role in Physiology and Pathology

Tenascin-C (TNC) is a multimodular extracellular matrix (ECM) protein hexameric with several molecular forms (180-250 kDa) produced by alternative splicing at the pre-mRNA level and protein modifications. The molecular phylogeny indicates that the amino acid sequence of TNC is a well-conserved protein among vertebrates. TNC has binding partners, including fibronectin, collagen, fibrillin-2, periostin, proteoglycans, and pathogens. Various transcription factors and intracellular regulators tightly regulate TNC expression. TNC plays an essential role in cell proliferation and migration. Unlike embryonic tissues, TNC protein is distributed over a few tissues in adults. However, higher TNC expression is observed in inflammation, wound healing, cancer, and other pathological conditions. It is widely expressed in a variety of human malignancies and is recognized as a pivotal factor in cancer progression and metastasis. Moreover, TNC increases both pro-and anti-inflammatory signaling pathways. It has been identified as an essential factor in tissue injuries such as damaged skeletal muscle, heart disease, and kidney fibrosis. This multimodular hexameric glycoprotein modulates both innate and adaptive immune responses regulating the expression of numerous cytokines. Moreover, TNC is an important regulatory molecule that affects the onset and progression of neuronal disorders through many signaling pathways. We provide a comprehensive overview of the structural and expression properties of TNC and its potential functions in physiological and pathological conditions.

Co-administration of extracellular matrix-based biomaterials with neural stem cell transplantation for treatment of central nervous system injury

Injuries and disorders of the central nervous system (CNS) present a particularly difficult challenge for modern medicine to address, given the complex nature of the tissues, obstacles in researching and implementing therapies, and barriers to translating efficacious treatments into human patients. Recent advancements in neural stem cell (NSC) transplantation, endogenous neurogenesis, and in vivo reprogramming of non-neural cells into the neuronal lineage represent multiple approaches to resolving CNS injury. However, we propose that one practice that must be incorporated universally in neuroregeneration studies is the use of extracellular matrix (ECM)-mimicking biomaterials to supply the architectural support and cellular microenvironment necessary for partial or complete restoration of function. Through consideration of developmental processes including neurogenesis, cellular migration, and establishment of functional connectivity, as well as evaluation of process-specific interactions between cells and ECM components, insights can be gained to harness and modulate native and induced neurobiological processes to promote CNS tissue repair. Further, evaluation of the current landscape of regenerative medicine and tissue engineering techniques external to the neurosciences provides key perspectives into the role of the ECM in the use of stem cell-based therapies, and the potential directions future neuroregenerative approaches may take. If the most successful of these approaches achieve wide-spread adoption, innovative paired NSC-ECM strategies for neuroregeneration may become prominent in the near future, and with the rapid advances these techniques are poised to herald, a new era of treatment for CNS injury may dawn.

Glycation Leads to Increased Invasion of Glioblastoma Cells

Glioblastoma (GBM) is a highly aggressive and invasive brain tumor with a poor prognosis despite extensive treatment. The switch to aerobic glycolysis, known as the Warburg effect, in cancer cells leads to an increased production of methylglyoxal (MGO), a potent glycation agent with pro-tumorigenic characteristics. MGO non-enzymatically reacts with proteins, DNA, and lipids, leading to alterations in the signaling pathways, genomic instability, and cellular dysfunction. In this study, we investigated the impact of MGO on the LN229 and U251 (WHO grade IV, GBM) cell lines and the U343 (WHO grade III) glioma cell line, along with primary human astrocytes (hA). The results showed that increasing concentrations of MGO led to glycation, the accumulation of advanced glycation end-products, and decreasing cell viability in all cell lines. The invasiveness of the GBM cell lines increased under the influence of physiological MGO concentrations (0.3 mmol/L), resulting in a more aggressive phenotype, whereas glycation decreased the invasion potential of hA. In addition, glycation had differential effects on the ECM components that are involved in the invasion progress, upregulating TGFβ, brevican, and tenascin C in the GBM cell lines LN229 and U251. These findings highlight the importance of further studies on the prevention of glycation through MGO scavengers or glyoxalase 1 activators as a potential therapeutic strategy against glioma and GBM.

Tenascin C+ papillary fibroblasts facilitate neuro-immune interaction in a mouse model of psoriasis

Dermal fibroblasts and cutaneous nerves are important players in skin diseases, while their reciprocal roles during skin inflammation have not been characterized. Here we identify an inflammation-induced subset of papillary fibroblasts that promotes aberrant neurite outgrowth and psoriasiform skin inflammation by secreting the extracellular matrix protein tenascin-C (TNC). Single-cell analysis of fibroblast lineages reveals a Tnc⁺ papillary fibroblast subset with pro-axonogenesis and neuro-regulation transcriptomic hallmarks. TNC overexpression in fibroblasts boosts neurite outgrowth in co-cultured neurons, while fibroblast-specific TNC ablation suppresses hyperinnervation and alleviates skin inflammation in male mice modeling psoriasis. Dermal γδT cells, the main producers of type 17 pathogenic cytokines, frequently contact nerve fibers in mouse psoriasiform lesions and are likely modulated by postsynaptic signals. Overall, our results highlight the role of an inflammation-responsive fibroblast subset in facilitating neuro-immune synapse formation and suggest potential avenues for future therapeutic research.

Extracellular matrix and synapse formation

The extracellular matrix (ECM) is a complex molecular network distributed throughout the extracellular space of different tissues as well as the neuronal system. Previous studies have identified various ECM components that play important roles in neuronal maturation and signal transduction. ECM components are reported to be involved in neurogenesis, neuronal migration, and axonal growth by interacting or binding to specific receptors. In addition, the ECM is found to regulate synapse formation, the stability of the synaptic structure, and synaptic plasticity. Here, we mainly reviewed the effects of various ECM components on synapse formation and briefly described the related diseases caused by the abnormality of several ECM components.

Matricellular protein tenascin C: Implications in glioma progression, gliomagenesis, and treatment

Matricellular proteins are nonstructural extracellular matrix components that are expressed at low levels in normal adult tissues and are upregulated during development or under pathological conditions. Tenascin C (TNC), a matricellular protein, is a hexameric and multimodular glycoprotein with different molecular forms that is produced by alternative splicing and post-translational modifications. Malignant gliomas are the most common and aggressive primary brain cancer of the central nervous system. Despite continued advances in multimodal therapy, the prognosis of gliomas remains poor. The main reasons for such poor outcomes are the heterogeneity and adaptability caused by the tumor microenvironment and glioma stem cells. It has been shown that TNC is present in the glioma microenvironment and glioma stem cell niches, and that it promotes malignant properties, such as neovascularization, proliferation, invasiveness, and immunomodulation. TNC is abundantly expressed in neural stem cell niches and plays a role in neurogenesis. Notably, there is increasing evidence showing that neural stem cells in the subventricular zone may be the cells of origin of gliomas. Here, we review the evidence regarding the role of TNC in glioma progression, propose a potential association between TNC and gliomagenesis, and summarize its clinical applications. Collectively, TNC is an appealing focus for advancing our understanding of gliomas.

The Glial Cells Respond to Spinal Cord Injury

It is been over 100 years since glial cells were discovered by Virchow. Since then, a great deal of research was carried out to specify these further roles and properties of glial cells in central nervous system (CNS). As it is well-known that glial cells, such as astrocytes, microglia, oligodendrocytes (OLs), and oligodendrocyte progenitor cells (OPCs) play an important role in supporting and enabling the effective nervous system function in CNS. After spinal cord injury (SCI), these glial cells play different roles in SCI and repair. In this review, we will discuss in detail about the role of glial cells in the healthy CNS and how they respond to SCI.

Diversity of satellite glia in sympathetic and sensory ganglia

Satellite glia are the major glial type found in sympathetic and sensory ganglia in the peripheral nervous system, and specifically, contact neuronal cell bodies. Sympathetic and sensory neurons differ in morphological, molecular, and electrophysiological properties. However, the molecular diversity of the associated satellite glial cells remains unclear. Here, using single-cell RNA sequencing analysis, we identify five different populations of satellite glia from sympathetic and sensory ganglia. We define three shared populations of satellite glia enriched in immune-response genes, immediate-early genes, and ion channels/ECM-interactors, respectively. Sensory- and sympathetic-specific satellite glia are differentially enriched for modulators of lipid synthesis and metabolism. Sensory glia are also specifically enriched for genes involved in glutamate turnover. Furthermore, satellite glia and Schwann cells can be distinguished by unique transcriptional signatures. This study reveals the remarkable heterogeneity of satellite glia in the peripheral nervous system.

The expression of tenascin-C in neural stem/progenitor cells is stimulated by the growth factors EGF and FGF-2, but not by TGFβ1

Neural stem/progenitor cells (NSPCs) rely on internal and external cues determining their lineage decisions during brain development. The progenitor cells of the embryonic mammalian forebrain reside in the ventricular and subventricular zones of the lateral ventricles, where they proliferate, generate neurons and glial cells, and respond to external cues like growth factors. The extracellular matrix (ECM) surrounds NSPCs and influences the cell fate by providing mechanical scaffold, trophic support, and instructive signals. The ECM molecule tenascin-C (Tnc) is expressed in the proliferative zones of the developing forebrain and involved in the proliferation and maturation of NSPCs. Here, we analyzed the regulation of the Tnc gene expression by NSPCs cultivated under the influence of different growth factors. We observed that the epidermal growth factor (EGF) and the fibroblast growth factor (FGF)-2 strongly increased the expression of Tnc, whereas the transforming growth factor (TGF)β 1 had no effect on Tnc gene expression, in contrast to previous findings in cell cultures of neural and non-neural origin. The stimulation of the Tnc gene expression induced by EGF or FGF-2 was reversible and seen in constantly treated as well as short term stimulated NSPC cultures. The activation depended on the presence of the respective receptors, which was slightly different in cortical and striatal NSPC cultures. Our results confirm the influence of extracellular stimuli regulating the expression of factors that form a niche for NSPCs during embryonic forebrain development.

Elevated glucose alters global gene expression and tenascin-C alternative splicing in mesangial cells

Mesangial cells are the major extracellular matrix (ECM)-producing cells in the kidney glomerulus and, when exposed to elevated glucose levels, they up-regulate assembly of fibronectin (FN) and other ECM proteins. Increases in glucose concentration are known to alter gene expression; here we investigated the connection between increased ECM production and changes in gene expression in mesangial cells. Comparison of mesangial cells grown in normal or high glucose conditions by RNA-sequencing showed significant expression changes in over 6000 genes and, when grouped by KEGG pathway analysis, identified the ECM-receptor interaction and focal adhesion pathways among the top 5 upregulated pathways. Of note was the significant increase in expression of tenascin-C (TN-C), a known regulator of FN matrix assembly. Mouse TN-C has multiple isoforms due to alternative splicing of 6 FNIII repeat exons. In addition to the transcriptional increase with high glucose, exon inclusion via alternative splicing was also changed resulting in production of higher molecular weight isoforms of TN-C. Mesangial cells grown in normal glucose secreted small isoforms with 1–2 variable repeats included whereas in high glucose large isoforms estimated to include 5 repeats were secreted. Unlike the smaller isoforms, the larger TN-C was not detected in the FN matrix. This change in TN-C isoforms may affect the regulation of FN matrix assembly and in this way may contribute to increased ECM accumulation under high glucose conditions.

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Elevated glucose alters gene expression in cultured mesangial cells.

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RNA-sequencing identifies increased expression of ECM proteins and receptors.

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High glucose changes tenascin-C isoform expression by alternative splicing.

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Differential ECM localization is detected for large vs small tenascin-C isoforms.

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Switch in tenascin-C may contribute to ECM accumulation in the diabetic glomerulus.

Silencing myelin protein zero-like 1 expression suppresses cell proliferation and invasiveness of human glioma cells by inhibiting multiple cancer-associated signal pathways

Glioma is the most common primary malignant tumor of the adult central nervous system. It has high morbidity and poor survival. Myelin protein zero-like protein 1 (MPZL1) is a cell surface glycoprotein that activates numerous adhesion-dependent signaling pathways. MPZL1 plays important roles in human cancers that include metastatic process; however, it is not clear if MPZL1 plays a role in human glioma. Therefore, this study aimed to determine if silencing MPZL1 impacted the cell proliferative features of human glioma cells. First, MPZL1 expression was investigated in human glioma samples and tumor cell lines. Then the effects of small interfering RNA (siRNA)-targeting MPZL1 were analyzed on proliferation, colony formation, cell cycle progression, and invasion of human glioma cells. The results from this study demonstrated that MPZL1 was highly expressed in human glioma tissues and glioma cell lines. In addition, knockdown of MPZL1 significantly inhibited cell proliferation, colony formation, and invasiveness of glioma cells, and effectively induced cell cycle arrest at the G1 phase. Western blotting analysis indicated that silencing MPZL1 expression downregulated the expression of matrix metalloproteinase-2 (MMP-2), WNT1, caspase-3, cyclin A1, epidermal growth factor receptor (EGFR), and signal transducer and activator of transcription 3 (STAT3), and upregulated p53. The results from this study suggest that MPZL1 might be a marker for tumors and could be a potential therapeutic target for human glioma.

Extracellular Matrix in Neural Plasticity and Regeneration

The extracellular matrix (ECM) is a fundamental component of biological tissues. The ECM in the central nervous system (CNS) is unique in both composition and function. Functions such as learning, memory, synaptogenesis, and plasticity are regulated by numerous ECM molecules. The neural ECM acts as a non-specific physical barrier that modulates neuronal plasticity and axon regeneration. There are two specialized types of ECM in the CNS, diffuse perisynaptic ECM and condensed ECM, which selectively surround the perikaryon and initial part of dendritic trees in subtypes of neurons, forming perineuronal nets. This review presents the current knowledge about the role of important neuronal ECM molecules in maintaining the basic functions of a neuron, including electrogenesis and the ability to form neural circuits. The review mainly focuses on the role of ECM components that participate in the control of key events such as cell survival, axonal growth, and synaptic remodeling. Particular attention is drawn to the numerous molecular partners of the main ECM components. These regulatory molecules are integrated into the cell membrane or disposed into the matrix itself in solid or soluble form. The interaction of the main matrix components with molecular partners seems essential in molecular mechanisms controlling neuronal functions. Special attention is paid to the chondroitin sulfate proteoglycan 4, type 1 transmembrane protein, neural-glial antigen 2 (NG2/CSPG4), whose cleaved extracellular domain is such a molecular partner that it not only acts directly on neural and vascular cells, but also exerts its influence indirectly by binding to resident ECM molecules.

Loss of the Extracellular Matrix Molecule Tenascin-C Leads to Absence of Reactive Gliosis and Promotes Anti-inflammatory Cytokine Expression in an Autoimmune Glaucoma Mouse Model

Previous studies demonstrated that retinal damage correlates with a massive remodeling of extracellular matrix (ECM) molecules and reactive gliosis. However, the functional significance of the ECM in retinal neurodegeneration is still unknown. In the present study, we used an intraocular pressure (IOP) independent experimental autoimmune glaucoma (EAG) mouse model to examine the role of the ECM glycoprotein tenascin-C (Tnc). Wild type (WT ONA) and Tnc knockout (KO ONA) mice were immunized with an optic nerve antigen (ONA) homogenate and control groups (CO) obtained sodium chloride (WT CO, KO CO). IOP was measured weekly and electroretinographies were recorded at the end of the study. Ten weeks after immunization, we analyzed retinal ganglion cells (RGCs), glial cells, and the expression of different cytokines in retina and optic nerve tissue in all four groups. IOP and retinal function were comparable in all groups. Although RGC loss was less severe in KO ONA, WT as well as KO mice displayed a significant cell loss after immunization. Compared to KO ONA, less βIII-tubulin+ axons, and downregulated oligodendrocyte markers were noted in WT ONA optic nerves. In retina and optic nerve, we found an enhanced GFAP+ staining area of astrocytes in immunized WT. A significantly higher number of retinal Iba1+ microglia was found in WT ONA, while a lower number of Iba1+ cells was observed in KO ONA. Furthermore, an increased expression of the glial markers Gfap, Iba1, Nos2, and Cd68 was detected in retinal and optic nerve tissue of WT ONA, whereas comparable levels were observed in KO ONA. In addition, pro-inflammatory Tnfa expression was upregulated in WT ONA, but downregulated in KO ONA. Vice versa, a significantly increased anti-inflammatory Tgfb1 expression was measured in KO ONA animals. We conclude that Tnc plays an important role in glial and inflammatory response during retinal neurodegeneration. Our results provide evidence that Tnc is involved in glaucomatous damage by regulating retinal glial activation and cytokine release. Thus, this transgenic EAG mouse model for the first time offers the possibility to investigate IOP-independent glaucomatous damage in direct relation to ECM remodeling.

Hydrogels Derivatized With Cationic Moieties or Functional Peptides as Efficient Supports for Neural Stem Cells

The increasing incidence of neurodegenerative diseases such as Alzheimer's or Parkinson's disease represents a significant burden for patients and national health systems. The conditions are primarily caused by the death of neurons and other neural cell types. One important aim of current stem cell research is to find a way to replace the lost cells. In this perspective, neural stem cells (NSCs) have been considered as a promising tool in the field of regenerative medicine. The behavior of NSCs is modulated by environmental influences, for example hormones, growth factors, cytokines, and extracellular matrix molecules or biomechanics. These factors can be studied by using well-defined hydrogels, which are polymeric networks of synthetic or natural origin with the ability to swell in water. These gels can be modified with a variety of molecules and optimized with regard to their mechanical properties to mimic the natural extracellular environment. In particular modifications applying distinct units such as functional domains and peptides can modulate the development of NSCs with regard to proliferation, differentiation and migration. One well-known peptide sequence that affects the behavior of NSCs is the integrin recognition sequence RGD that has originally been derived from fibronectin. In the present review we provide an overview concerning the applications of modified hydrogels with an emphasis on synthetic hydrogels based on poly(acrylamides), as modified with either cationic moieties or the peptide sequence RGD. This knowledge might be used in tissue engineering and regenerative medicine for the therapy of spinal cord injuries, neurodegenerative diseases and traumata.

Hyaluronic Acid and Regenerative Medicine: New Insights into the Stroke Therapy

Stroke is known as one of the very important public health problems that are related to societal burden and tremendous economic losses. It has been shown that there are few therapeutic approaches for the treatment of this disease. In this regard, the present therapeutic platforms aim to obtain neuroprotection, reperfusion, and neuro recovery. Among these therapies, regenerative medicine-based therapies have appeared as new ways of stroke therapy. Hyaluronic acid (HA) is a new candidate, which could be applied as a regenerative medicine-based therapy in the treatment of stroke. HA is a glycosaminoglycan composed of disaccharide repeating elements (N-acetyl-Dglucosamine and D-glucuronic acid). Multiple lines of evidence demonstrated that HA has critical roles in normal tissues. It can be a key player in different physiological and pathophysiological conditions such as water homeostasis, multiple drug resistance, inflammatory processes, tumorigenesis, angiogenesis, and changed viscoelasticity of the extracellular matrix. HA has very important physicochemical properties i.e., availability of reactive functional groups and its solubility, which make it a biocompatible material for application in regenerative medicine. Given that HAbased bioscaffolds and biomaterials do not induce inflammation or allergies and are hydrophilic, they are used as soft tissue fillers and injectable dermal fillers. Several studies indicated that HA could be employed as a new therapeutic candidate in the treatment of stroke. These studies documented that HA and HA-based therapies exert their pharmacological effects via affecting stroke-related processes. Herein, we summarized the role of the extracellular matrix in stroke pathogenesis. Moreover, we highlighted the HA-based therapies for the treatment of stroke.

Deletion of the Nucleotide Exchange Factor Vav3 Enhances Axonal Complexity and Synapse Formation but Tampers Activity of Hippocampal Neuronal Networks In Vitro

Vav proteins activate GTPases of the RhoA subfamily that regulate the cytoskeleton and are involved in adhesion, migration, differentiation, polarity and the cell cycle. While the importance of RhoA GTPases for neuronal morphology is undisputed, their regulation is less well understood. In this perspective, we studied the consequences of the deletion of Vav2, Vav3 and Vav2 and 3 (Vav2^-/-, Vav3^-/-, Vav2^-/-/3^-/-) for the development of embryonic hippocampal neurons in vitro. Using an indirect co-culture system of hippocampal neurons with primary wild-type (WT) cortical astrocytes, we analysed axonal and dendritic parameters, structural synapse numbers and the spontaneous network activity via immunocytochemistry and multielectrode array analysis (MEA). Here, we observed a higher process complexity in Vav3^-/-, but not in Vav2^-/- neurons after three and five days in vitro (DIV). Furthermore, an enhanced synapse formation was observed in Vav3^-/- after 14 days in culture. Remarkably, Vav2^-/-/3^-/- double knockout neurons did not display synergistic effects. Interestingly, these differences were transient and compensated after a cultivation period of 21 days. Network analysis revealed a diminished number of spontaneously occurring action potentials in Vav3^-/- neurons after 21 DIV. Based on these results, it appears that Vav3 participates in key events of neuronal differentiation.

Demystifying the extracellular matrix and its proteolytic remodeling in the brain: structural and functional insights

The extracellular matrix (ECM) plays diverse roles in several physiological and pathological conditions. In the brain, the ECM is unique both in its composition and in functions. Furthermore, almost all the cells in the central nervous system contribute to different aspects of this intricate structure. Brain ECM, enriched with proteoglycans and other small proteins, aggregate into distinct structures around neurons and oligodendrocytes. These special structures have cardinal functions in the normal functioning of the brain, such as learning, memory, and synapse regulation. In this review, we have compiled the current knowledge about the structure and function of important ECM molecules in the brain and their proteolytic remodeling by matrix metalloproteinases and other enzymes, highlighting the special structures they form. In particular, the proteoglycans in brain ECM, which are essential for several vital functions, are emphasized in detail.

Site-specific HNK-1 epitope on alternatively spliced fibronectin type-III repeats in tenascin-C promotes neurite outgrowth of hippocampal neurons through contactin-1

The human natural killer-1 (HNK-1) carbohydrate epitope, composed of a unique sulfated trisaccharide (HSO₃–3GlcAβ1–3Galβ1–4GlcNAc-R), is highly expressed during brain development and regulates higher brain function. However, it remains unclear which glycoprotein carries the HNK-1 epitope in the embryonic brain and the functional role it plays. Here, we showed that one of the major HNK-1 carrier proteins in the embryonic brain is tenascin-C (TNC), an extracellular matrix protein that regulates neurite outgrowth by interacting with the GPI-anchored protein contactin-1 (CNTN). Because the alternatively spliced fibronectin type-III (FNIII) repeats in TNC give rise to many isoforms and affect neuronal function, we evaluated neurite outgrowth of primary hippocampal neurons on purified recombinant FNIII repeats with or without the HNK-1 epitope as a substrate. We found that the presence of the HNK-1 epitope on the C domain of TNC promoted neurite outgrowth, and that this signal was mediated by CNTN, which is an HNK-1-expressing neuronal receptor. The neurite-promoting activity of the HNK-1 epitope on TNC required neuronal HNK-1 expression, which was defective in neurons lacking the glucuronyltransferases GlcAT-P and GlcAT-S. These results suggest that the HNK-1 epitope is a key modifier of TNC and CNTN in the regulation of embryonic brain development.

Role of immune responses for extracellular matrix remodeling in the ischemic brain

Neuroinflammation is one of the key components contributing to the devastating outcome of ischemic stroke. Starting with stroke onset, inflammatory processes contribute both to cell damage and tissue remodeling. The early release of alarmins triggers the upregulation of multiple proinflammatory cytokines, resulting in the compromised integrity of the blood–brain barrier. From this moment on, the infiltration of peripheral immune cells, reactive gliosis and extracellular matrix (ECM) alterations become intricately intertwined and act as one unit during the tissue remodeling. While the mechanisms of leukocyte and glia activation are amply reviewed, the field of ECM modification remains as yet under explored. In this review, we focus on the interplay between neuroinflammatory cascades and ECM in the ischemic brain. By summarizing the currently available evidence obtained by in vitro research, animal experimentation and human studies, we aim to propose a new direction for the future investigation of stroke recovery.

Cell tracking in vitro reveals that the extracellular matrix glycoprotein Tenascin-C modulates cell cycle length and differentiation in neural stem/progenitor cells of the developing mouse spinal cord

Generation of astrocytes during the development of the mammalian spinal cord is poorly understood. Previously, we have shown that the glycoprotein of the extracellular matrix (ECM) tenascin-C (Tnc) modulates the expression territories of the patterning genes Nkx6.1 and Nkx2.2 in the developing ventral spinal cord, tunes the responsiveness of neural stem/progenitor cells towards the cytokines FGF2 and EGF and thereby promotes astrocyte maturation. In order to obtain further mechanistic insight into these processes, we have compared embryonic day-15 spinal cord neural progenitor cells (NPCs) from wild-type and Tnc knockout mice using continuous single-cell live imaging and cell lineage analysis in vitroTnc knockout cells displayed a significantly reduced rate of cell division both in response to FGF2 and EGF. When individual clones of dividing cells were investigated with regard to their cell lineage trees using the tTt tracking software, it appeared that the cell cycle length in response to growth factors was reduced in the knockout. Furthermore, when Tnc knockout NPCs were induced to differentiate by the removal of FGF2 and EGF glial differentiation was enhanced. We conclude that the constituent of the stem cell niche Tnc contributes to preserve stemness of NPCs.

Role of Microenvironment in Glioma Invasion: What We Learned from In Vitro Models

The invasion properties of glioblastoma hamper a radical surgery and are responsible for its recurrence. Understanding the invasion mechanisms is thus critical to devise new therapeutic strategies. Therefore, the creation of in vitro models that enable these mechanisms to be studied represents a crucial step. Since in vitro models represent an over-simplification of the in vivo system, in these years it has been attempted to increase the level of complexity of in vitro assays to create models that could better mimic the behaviour of the cells in vivo. These levels of complexity involved: 1. The dimension of the system, moving from two-dimensional to three-dimensional models; 2. The use of microfluidic systems; 3. The use of mixed cultures of tumour cells and cells of the tumour micro-environment in order to mimic the complex cross-talk between tumour cells and their micro-environment; 4. And the source of cells used in an attempt to move from commercial lines to patient-based models. In this review, we will summarize the evidence obtained exploring these different levels of complexity and highlighting advantages and limitations of each system used.

Tenascins in Retinal and Optic Nerve Neurodegeneration

Tenascins represent key constituents of the extracellular matrix (ECM) with major impact on central nervous system (CNS) development. In this regard, several studies indicate that they play a crucial role in axonal growth and guidance, synaptogenesis and boundary formation. These functions are not only important during development, but also for regeneration under several pathological conditions. Additionally, tenascin-C (Tnc) represents a key modulator of the immune system and inflammatory processes. In the present review article, we focus on the function of Tnc and tenascin-R (Tnr) in the diseased CNS, specifically after retinal and optic nerve damage and degeneration. We summarize the current view on both tenascins in diseases such as glaucoma, retinal ischemia, age-related macular degeneration (AMD) or diabetic retinopathy. In this context, we discuss their expression profile, possible functional relevance, remodeling of the interacting matrisome and tenascin receptors, especially under pathological conditions.

Quantitative Visualization of Dynamic Tracer Transportation in the Extracellular Space of Deep Brain Regions Using Tracer-Based Magnetic Resonance Imaging

Background

This study assessed an innovative tracer-based magnetic resonance imaging (MRI) system to visualize the dynamic transportation of tracers in regions of deep brain extracellular space (ECS) and to measure transportation ability and ECS structure.

Material/Methods

Gadolinium-diethylene triamine pentaacetic acid (Gd-DTPA) was the chosen tracer and was injected into the caudate nucleus and thalamus. Real-time dynamic transportation of Gd-DTPA in ECS was observed and the results were verified by laser scanning confocal microscopy. Using Transwell assay across the blood-brain barrier, a modified diffusion equation was further simplified. Effective diffusion coefficient D* and tortuosity λ were calculated. Immunohistochemical staining and Western blot analysis were used to investigate the extracellular matrix contributing to ECS structure.

Results

Tracers injected into the caudate nucleus were transported to the ipsilateral frontal and temporal cortices away from the injection points, while both of them injected into the thalamus were only distributed on site. Although the caudate nucleus was closely adjacent to the thalamus, tracer transportation between partitions was not observed. In addition, D* and the λ showed statistically significant differences between partitions. ECS was shown to be a physiologically partitioned system, and its division is characterized by the unique distribution territory and transportation ability of substances located in it. Versican and Tenascin R are possible contributors to the tortuosity of ECS.

Conclusions

Tracer-based MRI will improve our understanding of the brain microenvironment, improve the techniques for local delivery of drugs, and highlight brain tissue engineering fields in the future.

Formation and remodeling of the brain extracellular matrix in neural plasticity: Roles of chondroitin sulfate and hyaluronan

BACKGROUND

The extracellular matrix (ECM) of the brain is rich in glycosaminoglycans such as chondroitin sulfate (CS) and hyaluronan. These glycosaminoglycans are organized into either diffuse or condensed ECM. Diffuse ECM is distributed throughout the brain and fills perisynaptic spaces, whereas condensed ECM selectively surrounds parvalbumin-expressing inhibitory neurons (PV cells) in mesh-like structures called perineuronal nets (PNNs). The brain ECM acts as a non-specific physical barrier that modulates neural plasticity and axon regeneration.

SCOPE OF REVIEW

Here, we review recent progress in understanding of the molecular basis of organization and remodeling of the brain ECM, and the involvement of several types of experience-dependent neural plasticity, with a particular focus on the mechanism that regulates PV cell function through specific interactions between CS chains and their binding partners. We also discuss how the barrier function of the brain ECM restricts dendritic spine dynamics and limits axon regeneration after injury.

MAJOR CONCLUSIONS

The brain ECM not only forms physical barriers that modulate neural plasticity and axon regeneration, but also forms molecular brakes that actively controls maturation of PV cells and synapse plasticity in which sulfation patterns of CS chains play a key role. Structural remodeling of the brain ECM modulates neural function during development and pathogenesis.

GENERAL SIGNIFICANCE

Genetic or enzymatic manipulation of the brain ECM may restore neural plasticity and enhance recovery from nerve injury. This article is part of a Special Issue entitled Neuro-glycoscience, edited by Kenji Kadomatsu and Hiroshi Kitagawa.

Matrix Metalloproteinases, Neural Extracellular Matrix, and Central Nervous System Pathology

The functionality and stability of the central nervous system (CNS) pabulum, called neural extracellular matrix (nECM), is paramount for the maintenance of a healthy network. The loosening or the damage of the scaffold disrupts synaptic transmission with the consequent imbalance of the neurotransmitters, reactive cells invasion, astrocytosis, new matrix deposition, digestion of the previous structure and ultimately, maladaptive plasticity with the loss of neuronal viability. nECM is constantly affected by CNS disorders, particularly in chronic modifying such as neurodegenerative disease, or in acute/subacute with chronic sequelae, like cerebrovascular and inflammatory pathology. Matrix metalloproteinases (MMPs) are the main interfering agent of nECM, guiding the balance of degradation and new deposition of proteins such as proteoglycans and glycoproteins, or glycosaminoglycans, such as hyaluronic acid. Activation of these enzymes is modulated by their physiologic inhibitors, the tissue inhibitors of MMPs or via other proteases inhibitors, as well as genetic or epigenetic up- or downregulation through molecular interaction or receptor activation. The appropriate understanding of the pathways underlying nECM modifications in CNS pathology is probably one of the pivotal future directions to identify the healthy brain network and subsequently design new therapies to interfere with the progression of the CNS disease and eventually find appropriate therapies.

Involvement of the guanine nucleotide exchange factor Vav3 in central nervous system development and plasticity

Small GTP-hydrolyzing enzymes (GTPases) of the RhoA family play manifold roles in cell biology and are regulated by upstream guanine nucleotide exchange factors (GEFs). Herein, we focus on the GEFs of the Vav subfamily. Vav1 was originally described as a proto-oncogene of the hematopoietic lineage. The GEFs Vav2 and Vav3 are more broadly expressed in various tissues. In particular, the GEF Vav3 may play important roles in the developing nervous system during the differentiation of neural stem cells into the major lineages, namely neurons, oligodendrocytes and astrocytes. We discuss its putative regulatory roles for progenitor differentiation in the developing retina, polarization of neurons and formation of synapses, migration of oligodendrocyte progenitors and establishment of myelin sheaths. We propose that Vav3 mediates the response of various neural cell types to environmental cues.

Proteome and Secretome Characterization of Glioblastoma-Derived Neural Stem Cells

Glioblastoma multiforme (GBM) (grade IV astrocytoma) is the most common and aggressive primary brain tumor. GBM consists of heterogeneous cell types including a subset of stem cell-like cells thought to sustain tumor growth. These tumor-initiating glioblastoma multiforme-derived neural stem (GNS) cells as well as their genetically normal neural stem (NS) counterparts can be propagated in culture as relatively pure populations. Here, we perform quantitative proteomics to globally characterize and compare total proteome plus the secreted proteome (secretome) between GNS cells and NS cells. Proteins and pathways that distinguish malignant cancer (GNS) stem cells from their genetically normal counterparts (NS cells) might have value as new biomarkers or therapeutic targets. Our analysis identified and quantified ∼7,500 proteins in the proteome and ∼2,000 in the secretome, 447 and 138 of which were differentially expressed, respectively. Notable tumor-associated processes identified using gene set enrichment analysis included: extracellular matrix interactions, focal adhesion, cell motility, and cell signaling. We focused on differentially expressed surface proteins, and identified 26 that participate in ligand-receptor pairs that play a prominent role in tumorigenesis. Immunocytochemistry and immunoblotting confirmed that CD9, a recently identified marker of adult subventricular zone NS cells, was consistently enriched across a larger set of primary GNS cell lines. CD9 may, therefore, have value as a GNS-specific surface marker and a candidate therapeutic target. Altogether, these findings support the notion that increased cell-matrix and cell-cell adhesion molecules play a crucial role in promoting the tumor initiating and infiltrative properties of GNS cells. Stem Cells 2017;35:967-980.

Crosstalk between glia, extracellular matrix and neurons

Extracellular matrix (ECM) molecules in the central nervous system form highly organized ECM structures around cell somata, axon initial segments, and synapses and play prominent roles in early development by guiding cell migration, neurite outgrowth and synaptogenesis, and by regulating closure of the critical period of development, synaptic plasticity and stability, cognitive flexibility, and axonal regeneration in adults. Major components of neural ECM, including chondroitin sulfate proteoglycans (CSPGs), tenascin-R and hyaluronic acid, are synthesized by both neurons and glial cells. The expression of these molecules is dynamically regulated during brain development in physiological conditions, shaping both neuronal and glial functions through multitude of molecular mechanisms. Upregulation of particular CSPGs and other ECM molecules, in particular by reactive astrocytes, after CNS injuries, during aging, neuroinflammation, and neurodegeneration on the one hand results in formation of growth-impermissive environment and impaired synaptic plasticity. On the other hand, ECM appeared to have a neuroprotective effect, at least in the form of perineuronal nets. CSPGs-degrading matrix metalloproteinases (MMPs) and several members of the disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) family of proteases are secreted by neurons and glia and may drive neural ECM remodeling in physiological conditions as well as after brain injury and other brain disorders. Thus, targeting expression of specific ECM molecules, associated glycans and degrading enzymes may lead to development of new therapeutic strategies promoting regeneration and synaptic plasticity.

Neural tissue engineering: Bioresponsive nanoscaffolds using engineered self-assembling peptides

Rescuing or repairing neural tissues is of utmost importance to the patient's quality of life after an injury. To remedy this, many novel biomaterials are being developed that are, ideally, non-invasive and directly facilitate neural wound healing. As such, this review surveys the recent approaches and applications of self-assembling peptides and peptide amphiphiles, for building multi-faceted nanoscaffolds for direct application to neural injury. Specifically, methods enabling cellular interactions with the nanoscaffold and controlling the release of bioactive molecules from the nanoscaffold for the express purpose of directing endogenous cells in damaged or diseased neural tissues is presented. An extensive overview of recently derived self-assembling peptide-based materials and their use as neural nanoscaffolds is presented. In addition, an overview of potential bioactive peptides and ligands that could be used to direct behaviour of endogenous cells are categorized with their biological effects. Finally, a number of neurotrophic and anti-inflammatory drugs are described and discussed. Smaller therapeutic molecules are emphasized, as they are thought to be able to have less potential effect on the overall peptide self-assembly mechanism. Options for potential nanoscaffolds and drug delivery systems are suggested.

STATEMENT OF SIGNIFICANCE

Self-assembling nanoscaffolds have many inherent properties making them amenable to tissue engineering applications: ease of synthesis, ease of customization with bioactive moieties, and amenable for in situ nanoscaffold formation. The combination of the existing knowledge on bioactive motifs for neural engineering and the self-assembling propensity of peptides is discussed in specific reference to neural tissue engineering.

Early remodelling of the extracellular matrix proteins tenascin-C and phosphacan in retina and optic nerve of an experimental autoimmune glaucoma model

Glaucoma is characterized by the loss of retinal ganglion cells (RGCs) and optic nerve fibres. Previous studies noted fewer RGCs after immunization with ocular antigens at 28 days. It is known that changes in extracellular matrix (ECM) components conduct retina and optic nerve degeneration. Here, we focused on the remodelling of tenascin‐C and phosphacan/receptor protein tyrosine phosphatase β/ζ in an autoimmune glaucoma model. Rats were immunized with optic nerve homogenate (ONA) or S100B protein (S100). Controls received sodium chloride (Co). After 14 days, no changes in RGC number were noted in all groups. An increase in GFAPmRNA expression was observed in the S100 group, whereas no alterations were noted via immunohistochemistry in both groups. Extracellular matrix remodelling was analyzed after 3, 7, 14 and 28 days. Tenascin‐C and 473HD immunoreactivity in retinae and optic nerves was unaltered in both immunized groups at 3 days. At 7 days, tenascin‐C staining increased in both tissues in the ONA group. Also, in the optic nerves of the S100 group, an intense tenascin‐C staining could be shown. In the retina, an increased tenascin‐C expression was also observed in ONA animals via Western blot. 473HD immunoreactivity was elevated in the ONA group in both tissues and in the S100 optic nerves at 7 days. At 14 days, tenascin‐C and 473HD immunoreactivity was up‐regulated in the ONA retinae, whereas phosphacan expression was up‐regulated in both groups. We conclude that remodelling of tenascin‐C and phosphacan occurred shortly after immunization, already before RGC loss. We assume that both ECM molecules represent early indicators of neurodegeneration.

Tenascin-C in Chronic Canine Hepatitis: Immunohistochemical Localization and Correlation with Necro-Inflammatory Activity, Fibrotic Stage, and Expression of Alpha-Smooth Muscle Actin, Cytokeratin 7, and CD3+ Cells

During fibrosis, the extracellular matrix (ECM) is continuously remodeled and increases in volume due to the production of various proteins. We studied the distribution of tenascin-C (TN-C) and the correlation of TN-C with the necro-inflammatory activity and expression of alpha–smooth muscle actin (α-SMA), cytokeratin 7 (CK7), and CD3+ T-lymphocytes in canine chronic hepatitis. This was analyzed using immunohistochemistry and semiquantitative scoring. We used 3 groups ( n = 19) of dogs: group 1 ( n = 5) with neonatal hepatitis/lobular dissecting hepatitis (NH/LDH), group 2 ( n = 8) with chronic hepatitis/cirrhosis (CH/CIRR), and group 3 ( n = 6) consisting of healthy animals. In normal livers, TN-C was localized in Disse's space and around bile ducts and blood vessels. In CH/CIRR livers, TN-C was localized at the periphery of the regenerating nodules and was conspicuous in the bridging fibrous bands. In NH/LDH, TN-C was diffusely distributed along the reticular fibers that dissected between single cells or groups of hepatocytes. α-SMA in the normal hepatic parenchyma showed an irregular distribution along the perisinusoidal linings. In other groups, α-SMA was increased in fibrotic septa and perisinusoidal linings. In normal livers, CK7 was positive in bile ducts. In other groups, CK7-expressing cells were conspicuous in the portal-parenchymal interface, the periphery of the regenerative nodules, and the degenerated parenchyma. The pattern of CD3+ lymphocytes was inversely proportional to that of TN-C. These results also showed that TN-C is strongly correlated with increased fibrotic stage, inflammatory activity, and expression of CK7 and α-SMA. TN-C, CK7, and CD3 expression did not differ between diagnostic groups.

The expression pattern and inhibitory influence of Tenascin-C on the growth of spiral ganglion neurons suggest a regulatory role as boundary formation molecule in the postnatal mouse inner ear

Sensorineural hearing loss, as a consequence of acoustic trauma, aging, genetic defects or ototoxic drugs, is highly associated with irreversible damage of cochlear hair cells (HCs) and secondary degeneration of spiral ganglion (SG) cells. Cochlear implants (CIs), which bypass the lost HC function by direct electrical stimulation of the remaining auditory neurons, offer an effective therapy option. Several studies imply that components of the extracellular matrix (ECM) have a great impact on the adhesion and growth of spiral ganglion neurons (SGNs) during development. Based on these findings, ECM proteins might act as bioactive CI substrates to optimize the electrode-nerve interface and to improve efficacy of these implants. In the present study, we focused on the ECM glycoproteins Tenascin-C (TN-C), Laminin (LN), and Fibronectin (FN), which show a prominent expression along the growth route of SGNs and the niche around HCs during murine postnatal development in vivo. We compared their influence on adhesion, neurite length, and neurite number of SGNs in vitro. Moreover, we studied the expression of the chondroitin sulfate proteoglycan (CSPG) dermatan sulfate-dependent proteoglycan-1 (DSD-1-PG), an interaction partner of TN-C. In sum, our in vitro data suggest that TN-C acts as an anti-adhesive and inhibitory factor for the growth of SGNs. The DSD-1 carbohydrate epitope is specifically localized to HC stereocilia and SG fibers. Interestingly, TN-C and the DSD-1-PG exhibit a mutually exclusive expression pattern, with the exception of a very restricted region beneath the habenula perforata, where SG neurites grow through the basilar membrane (BM) toward the HCs. The complementary expression of TN-C, LN, FN, and the DSD-1 epitope suggests that TN-C may act as an important boundary formation molecule in the developing postnatal mouse inner ear, which makes it a promising candidate to regulate neurite outgrowth in the light of CIs.

Neuron-Glia Interactions in Neural Plasticity: Contributions of Neural Extracellular Matrix and Perineuronal Nets

Synapses are specialized structures that mediate rapid and efficient signal transmission between neurons and are surrounded by glial cells. Astrocytes develop an intimate association with synapses in the central nervous system (CNS) and contribute to the regulation of ion and neurotransmitter concentrations. Together with neurons, they shape intercellular space to provide a stable milieu for neuronal activity. Extracellular matrix (ECM) components are synthesized by both neurons and astrocytes and play an important role in the formation, maintenance, and function of synapses in the CNS. The components of the ECM have been detected near glial processes, which abut onto the CNS synaptic unit, where they are part of the specialized macromolecular assemblies, termed perineuronal nets (PNNs). PNNs have originally been discovered by Golgi and represent a molecular scaffold deposited in the interface between the astrocyte and subsets of neurons in the vicinity of the synapse. Recent reports strongly suggest that PNNs are tightly involved in the regulation of synaptic plasticity. Moreover, several studies have implicated PNNs and the neural ECM in neuropsychiatric diseases. Here, we highlight current concepts relating to neural ECM and PNNs and describe an in vitro approach that allows for the investigation of ECM functions for synaptogenesis.

Transcriptional regulation of tenascin genes

Extracellular matrix proteins of the tenascin family resemble each other in their domain structure, and also share functions in modulating cell adhesion and cellular responses to growth factors. Despite these common features, the 4 vertebrate tenascins exhibit vastly different expression patterns. Tenascin-R is specific to the central nervous system. Tenascin-C is an “oncofetal” protein controlled by many stimuli (growth factors, cytokines, mechanical stress), but with restricted occurrence in space and time. In contrast, tenascin-X is a constituitive component of connective tissues, and its level is barely affected by external factors. Finally, the expression of tenascin-W is similar to that of tenascin-C but even more limited. In accordance with their highly regulated expression, the promoters of the tenascin-C and -W genes contain TATA boxes, whereas those of the other 2 tenascins do not. This article summarizes what is currently known about the complex transcriptional regulation of the 4 tenascin genes in development and disease.

Tenascin-C: Form versus function

Tenascin-C is a large, multimodular, extracellular matrix glycoprotein that exhibits a very restricted pattern of expression but an enormously diverse range of functions. Here, we discuss the importance of deciphering the expression pattern of, and effects mediated by, different forms of this molecule in order to fully understand tenascin-C biology. We focus on both post transcriptional and post translational events such as splicing, glycosylation, assembly into a 3D matrix and proteolytic cleavage, highlighting how these modifications are key to defining tenascin-C function.

Expression of genes encoding extracellular matrix proteins: a macroarray study

Endometrial cancer (EC) is one of the most common gynecological malignancies in Poland, with well-established risk factors. Genetic instability and molecular alterations responsible for endometrial carcinogenesis have been systematically investigated. The aim of the present study was to investigate, by means of cDNA macroarrays, the expression profiles of genes encoding extracellular matrix (ECM) proteins in ECs. Tissue specimens were collected during surgical procedures from 40 patients with EC, and control tissue was collected from 9 patients with uterine leiomyomas. RNA was isolated and RT-PCR with radioisotope-labeled cDNA was performed. The levels of ECM protein gene expression in normal endometrial tissues were compared to the expression of these genes in EC specimens. Statistically significant differences in gene expression, stratified by clinical stage of the ECs, were detected for aggrecan, vitronectin, tenascin R, nidogen and two collagen proteins: type VIII chain α1 and type XI chain α2. All of these proteins were overexpressed in stage III endometrial carcinomas compared to levels in stage I and II uterine neoplasms. In conclusion, increased expression of genes encoding ECM proteins may play an important role in facilitating accelerated disease progression of human ECs.

Influence of the extracellular matrix on endogenous and transplanted stem cells after brain damage

The limited regeneration capacity of the adult central nervous system (CNS) requires strategies to improve recovery of patients. In this context, the interaction of endogenous as well as transplanted stem cells with their environment is crucial. An understanding of the molecular mechanisms could help to improve regeneration by targeted manipulation. In the course of reactive gliosis, astrocytes upregulate Glial fibrillary acidic protein (GFAP) and start, in many cases, to proliferate. Beside GFAP, subpopulations of these astroglial cells coexpress neural progenitor markers like Nestin. Although cells express these markers, the proportion of cells that eventually give rise to neurons is limited in many cases in vivo compared to the situation in vitro. In the first section, we present the characteristics of endogenous progenitor-like cells and discuss the differences in their neurogenic potential in vitro and in vivo. As the environment plays an important role for survival, proliferation, migration, and other processes, the second section of the review describes changes in the extracellular matrix (ECM), a complex network that contains numerous signaling molecules. It appears that signals in the damaged CNS lead to an activation and de-differentiation of astrocytes, but do not effectively promote neuronal differentiation of these cells. Factors that influence stem cells during development are upregulated in the damaged brain as part of an environment resembling a stem cell niche. We give a general description of the ECM composition, with focus on stem cell-associated factors like the glycoprotein Tenascin-C (TN-C). Stem cell transplantation is considered as potential treatment strategy. Interaction of transplanted stem cells with the host environment is critical for the outcome of stem cell-based therapies. Possible mechanisms involving the ECM by which transplanted stem cells might improve recovery are discussed in the last section.

A neurocentric perspective on glioma invasion

Malignant gliomas are devastating tumours that frequently kill patients within 1 year of diagnosis. The major obstacle to a cure is diffuse invasion, which enables tumours to escape complete surgical resection and chemo- and radiation therapy. Gliomas use the same tortuous extracellular routes of migration that are travelled by immature neurons and stem cells, frequently using blood vessels as guides. They repurpose ion channels to dynamically adjust their cell volume to accommodate to narrow spaces and breach the blood-brain barrier through disruption of astrocytic endfeet, which envelop blood vessels. The unique biology of glioma invasion provides hitherto unexplored brain-specific therapeutic targets for this devastating disease.

The rat striatum responds to nigro-striatal degeneration via the increased expression of proteins associated with growth and regeneration of neuronal circuitry

BACKGROUND

Idiopathic Parkinson's disease is marked by degeneration of dopamine neurons projecting from the substantia nigra to the striatum. Although proteins expressed by the target striatum can positively affect the viability and growth of dopaminergic neurons, very little is known about the molecular response of the striatum as nigro-striatal denervation progresses. Here, iTRAQ labelling and MALDI TOF/TOF mass spectrometry have been used to quantitatively compare the striatal proteome of rats before, during, and after 6-OHDA induced dopamine denervation.

RESULTS

iTRAQ analysis revealed the differential expression of 50 proteins at 3 days, 26 proteins at 7 days, and 34 proteins at 14 days post-lesioning, compared to the unlesioned striatum. While the denervated striatum showed a reduced expression of proteins associated with the loss of dopaminergic input (e.g., TH and DARPP-32), there was an increased expression of proteins associated with regeneration and growth of neurites (e.g., GFAP). In particular, the expression of guanine deaminase (GDA, cypin) - a protein known to be involved in dendritic branching - was significantly increased in the striatum at 3, 7 and 14 days post-lesioning (a finding verified by immunohistochemistry).

CONCLUSIONS

Together, these findings provide evidence to suggest that the response of the normal mammalian striatum to nigro-striatal denervation includes the increased expression of proteins that may have the capacity to facilitate repair and growth of neuronal circuitry.

L-serine treatment may improve neurorestoration of rats after permanent focal cerebral ischemia potentially through improvement of neurorepair

The present study was conducted to clarify whether treatment with L-serine can improve the brain repair and neurorestoration of rats after permanent middle cerebral artery occlusion (pMCAO). After pMCAO, the neurological functions, brain lesion volume, and cortical injury were determined. GDNF, NGF, NCAM L1, tenascin-C, and Nogo-A levels were measured. Proliferation and differentiation of the neural stem cells (NSCs) and proliferation of the microvessels in the ischemic boundary zone of the cortex were evaluated. Treatment with L-serine (168 mg/kg body weight, i.p.) began 3 h after pMCAO and was repeated every 12 h for 7 days or until the end of the experiment. L-Serine treatment: 1) reduced the lesion volume and neuronal loss; 2) improved the recovery of neurological functions; 3) elevated the expression of nerve growth-related factors; and 4) facilitated the proliferation of endogenous NSCs and microvessels activated after pMCAO and increased the number of new-born neurons. 5) D-cycloserine, an inhibitor of serine hydroxymethyltransferase, blunted the effects of L-serine on NSC proliferation, differentiation, microvascular proliferation. In conclusions, L-serine treatment in pMCAO rats can reduce brain injury and facilitate neurorestoration which is partly associated with the improvement of proliferation of NSCs and microvessels, reconstruction of neurovascular units and resultant neurorepair. The effects of L-serine on endogenous NSC proliferation and microvascular proliferation are partly mediated by the action of L-serine as a substrate for the production of one-carbon groups used for purine and pyrimidine synthesis and modulation of the expression of some nerve growth-related factors.