The inflammation-associated protein TSG-6 cross-links hyaluronan via hyaluronan-induced TSG-6 oligomers

Glycosaminoglycans: Mechanisms and therapeutic potential in neurological diseases: A mini-review

Glycosaminoglycans (GAGs) are vital polysaccharides that constitute key elements of the extracellular matrix (ECM), particularly within chondroitin sulfate proteoglycans (CSPGs). GAGs exhibit a dual role in neural tissue: they facilitate synaptic plasticity and cellular adhesion, essential for neural function, while posing as barriers to axonal regeneration following injury. Through interactions with diverse proteins, including enzymes, cytokines, and growth factors, GAGs critically influence neural development, repair, and homeostasis. Recent advancements have underscored the therapeutic potential of modulating GAG synthesis, degradation, and receptor interactions to address neuroinflammation, promote neural repair, and counteract inhibitory signals in the injured CNS. Furthermore, combining GAG-targeted therapies with complementary approaches, such as gene therapy or nanoparticle-based delivery systems, holds promise for achieving synergistic effects and enhancing treatment outcomes. This mini-review explores the multifaceted roles of GAGs in neural physiology and pathology, highlighting their emerging potential as therapeutic targets for neurological disorders.

The roles of hyaluronan in kidney development, physiology and disease

The hyaluronan (HA) matrix in the tissue microenvironment is crucial for maintaining homeostasis by regulating inflammatory signalling, endothelial-mesenchymal transition and cell migration. During development, covalent modifications and osmotic swelling of HA create mechanical forces that initiate midgut rotation, vascular patterning and branching morphogenesis. Together with its main cell surface receptor, CD44, HA establishes a physicochemical scaffold at the cell surface that facilitates the interaction and clustering of growth factors and receptors that is required for normal physiology. High-molecular-weight HA, tumour necrosis factor-stimulated gene 6, pentraxin 3 and CD44 form a stable pericellular matrix that promotes tissue regeneration and reduces inflammation. By contrast, breakdown of high-molecular-weight HA into depolymerized fragments by hyaluronidases triggers inflammatory signalling, leukocyte migration and angiogenesis, contributing to tissue damage and fibrosis in kidney disease. Targeting HA metabolism is challenging owing to its dynamic regulation and tissue-specific functions. Nonetheless, modulating HA matrix functions by targeting its binding partners holds promise as a therapeutic strategy for restoring tissue homeostasis and mitigating pathological processes. Further research in this area is warranted to enable the development of novel therapeutic approaches for kidney and other diseases characterized by dysregulated HA metabolism.

Hyaluronan and proteoglycan link protein 1 - A novel signaling molecule for rejuvenating aged skin

The skin seems to rejuvenate upon exposure to factors within the circulation of young organisms. Intrinsic factors that modulate skin aging are poorly understood. We used heterochronic parabiosis and aptamer-based proteomics to identify serum-derived rejuvenating factors. We discovered a novel extracellular function of hyaluronan and proteoglycan link protein 1 (HAPLN1). Its serum levels decreased with age, disturbing the integrity of the skin extracellular matrix, which is predominantly composed of collagen I and hyaluronan; levels of various markers, which decrease in aged skin, were significantly restored in vivo and in vitro by the administration of recombinant human HAPLN1 (rhHAPLN1). rhHAPLN1 protected transforming growth factor beta receptor 2 on the cell surface from endocytic degradation via mechanisms such as regulation of viscoelasticity, CD44 clustering. Moreover, rhHAPLN1 regulated the levels of nuclear factor erythroid 2-related factor 2, phosphorylated nuclear factor kappa B, and some cyclin-dependent kinase inhibitors such as p16 and p21. Therefore, rhHAPLN1 may act as a novel biomechanical signaling protein to rejuvenate aged skin.

Hyaluronan in lung, in plasma as pathogenic and prediction factor of acute respiratory distress syndrome: A systematic review

This investigation aims to study contemporary literature pertaining to the involvement of hyaluronate in the pathogenesis of diverse medical conditions, encompassing coronavirus-induced pulmonary injury, while also exploring its potential utility as a prognostic indicator for assessing the severity of COVID-19. This study conducted a comprehensive examination of hyaluronic acid’s multifaceted role in physiological processes and disease, with a specific focus on its implications in COVID-induced lung damage. The research provided an in-depth analysis of the intricate mechanisms and fundamental patterns governing these biological phenomena, elucidating essential interactions and pathways. Of particular significance in this investigation was the potential diagnostic utility of hyaluronic acid in assessing the severity of acute respiratory distress syndrome (ARDS), including COVID-19. Through a rigorous examination of hyaluronic acid concentration levels, researchers sought to assess its potential as an early prognostic indicator, thereby providing valuable insights for clinical diagnostics. Furthermore, the study explored the therapeutic prospects related to hyaluronic acid, emphasizing its involvement in various pathological processes. It suggested that targeting hyaluronic acid could represent a promising avenue for drug development, potentially leading to the creation of innovative pharmaceutical agents

Brain Ischemic Tolerance Triggered by Preconditioning Involves Modulation of Tumor Necrosis Factor-α-Stimulated Gene 6 (TSG-6) in Mice Subjected to Transient Middle Cerebral Artery Occlusion

Ischemic preconditioning (PC) induced by a sub-lethal cerebral insult triggers brain tolerance against a subsequent severe injury through diverse mechanisms, including the modulation of the immune system. Tumor necrosis factor (TNF)-α-stimulated gene 6 (TSG-6), a hyaluronate (HA)-binding protein, has recently been involved in the regulation of the neuroimmune response following ischemic stroke. Thus, we aimed at assessing whether the neuroprotective effects of ischemic PC involve the modulation of TSG-6 in a murine model of transient middle cerebral artery occlusion (MCAo). The expression of TSG-6 was significantly elevated in the ischemic cortex of mice subjected to 1 h MCAo followed by 24 h reperfusion, while this effect was further potentiated (p < 0.05 vs. MCAo) by pre-exposure to ischemic PC (i.e., 15 min MCAo) 72 h before. By immunofluorescence analysis, we detected TSG-6 expression mainly in astrocytes and myeloid cells populating the lesioned cerebral cortex, with a more intense signal in tissue from mice pre-exposed to ischemic PC. By contrast, levels of TSG-6 were reduced after 24 h of reperfusion in plasma (p < 0.05 vs. SHAM), but were dramatically elevated when severe ischemia (1 h MCAo) was preceded by ischemic PC (p < 0.001 vs. MCAo) that also resulted in significant neuroprotection. In conclusion, our data demonstrate that neuroprotection exerted by ischemic PC is associated with the elevation of TSG-6 protein levels both in the brain and in plasma, further underscoring the beneficial effects of this endogenous modulator of the immune system.

Biomimetic Hyaluronan Binding Biomaterials to Capture the Complex Regulation of Hyaluronan in Tissue Development and Function

Within native ECM, Hyaluronan (HA) undergoes remarkable structural remodeling through its binding receptors and proteins called hyaladherins. Hyaladherins contain a group of tandem repeat sequences, such as LINK domains, BxB7 homologous sequences, or 20-50 amino acid long short peptide sequences that have high affinity towards side chains of HA. The HA binding sequences are critical players in HA distribution and regulation within tissues and potentially attractive therapeutic targets to regulate HA synthesis and organization. While HA is a versatile and successful biopolymer, most HA-based therapeutics have major differences from a native HA molecule, such as molecular weight discrepancies, crosslinking state, and remodeling with other HA binding proteins. Recent studies showed the promise of HA binding domains being used as therapeutic biomaterials for osteoarthritic, ocular, or cardiovascular therapeutic products. However, we propose that there is a significant potential for HA binding materials to reveal the physiological functions of HA in a more realistic setting. This review is focused on giving a comprehensive overview of the connections between HA's role in the body and the potential of HA binding material applications in therapeutics and regenerative medicine. We begin with an introduction to HA then discuss HA binding molecules and the process of HA binding. Finally, we discuss HA binding materials anf the future prospects of potential HA binding biomaterials systems in the field of biomaterials and tissue engineering.

TSG-6-Mediated Extracellular Matrix Modifications Regulate Hypoxic-Ischemic Brain Injury

Proteoglycans containing link domains modify the extracellular matrix (ECM) to regulate cellular homeostasis and can also sensitize tissues/organs to injury and stress. Hypoxic-ischemic (H-I) injury disrupts cellular homeostasis by activating inflammation and attenuating regeneration and repair pathways. In the brain, the main component of the ECM is the glycosaminoglycan hyaluronic acid (HA), but whether HA modifications of the ECM regulate cellular homeostasis and response to H-I injury is not known. In this report, employing both male and female mice, we demonstrate that link-domain-containing proteoglycan, TNFα-stimulated gene-6 (TSG-6), is active in the brain from birth onward and differentially modifies ECM HA during discrete neurodevelopmental windows. ECM HA modification by TSG-6 enables it to serve as a developmental switch to regulate the activity of the Hippo pathway effector protein, yes-associated protein 1 (YAP1), in the maturing brain and in response to H-I injury. Mice that lack TSG-6 expression display dysregulated expression of YAP1 targets, excitatory amino acid transporter 1 (EAAT1; glutamate-aspartate transporter) and 2 (EAAT2; glutamate transporter-1). Dysregulation of YAP1 activation in TSG-6-/- mice coincides with age- and sex-dependent sensitization of the brain to H-I injury such that 1-week-old neonates display an anti-inflammatory response in contrast to an enhanced proinflammatory injury reaction in 3-month-old adult males but not females. Our findings thus support that a key regulator of age- and sex-dependent H-I injury response in the mouse brain is modulation of the Hippo-YAP1 pathway by TSG-6-dependent ECM modifications.

Endogenous TSG-6 modulates corneal inflammation following chemical injury

PURPOSE

Tumor necrosis factor (TNF)-stimulated gene-6 (TSG-6) is upregulated in various pathophysiological contexts, where it has a diverse repertoire of immunoregulatory functions. Herein, we investigated the expression and function of TSG-6 during corneal homeostasis and after injury.

METHODS

Human corneas, eyeballs from BALB/c (TSG-6+/+), TSG-6+/- and TSG-6-/- mice, human immortalized corneal epithelial cells and murine corneal epithelial progenitor cells were prepared for immunostaining and real time PCR analysis of endogenous expression of TSG-6. Mice were subjected to unilateral corneal debridement or alkali burn (AB) injuries and wound healing assessed over time using fluorescein stain, in vivo confocal microscopy and histology.

RESULTS

TSG-6 is endogenously expressed in the human and mouse cornea and established corneal epithelial cell lines and is upregulated after injury. A loss of TSG-6 has no structural and functional effect in the cornea during homeostasis. No differences were noted in the rate of corneal epithelial wound closure between BALB/c, TSG-6+/- and TSG-6-/- mice. TSG-6-/- mice presented decreased inflammatory response within the first 24 h of injury and accelerated corneal wound healing following AB when compared to control mice.

CONCLUSION

TSG-6 is endogenously expressed in the cornea and upregulated after injury where it propagates the inflammatory response following chemical injury.

Inter-alpha-trypsin inhibitor (IαI) and hyaluronan modifications enhance the innate immune response to influenza virus in the lung

The inter-alpha-trypsin inhibitor (IαI) complex is composed of the bikunin core protein with a single chondroitin sulfate (CS) attached and one or two heavy chains (HCs) covalently linked to the CS chain. The HCs from IαI can be transferred to hyaluronan (HA) through a TNFα-stimulated gene-6 (TSG-6) dependent process to form an HC•HA matrix. Previous studies reported increased IαI, HA, and HC•HA complexes in mouse bronchoalveolar lavage fluid (BALF) post-influenza infection. However, the expression and incorporation of HCs into the HA matrix of the lungs during the clinical course of influenza A virus (IAV) infection and the biological significance of the HC•HA matrix are poorly understood. The present study aimed to better understand the composition of HC•HA matrices in mice infected with IAV and how these matrices regulate the host pulmonary immune response. In IAV infected mice bikunin, HC1-3, TSG-6, and HAS1-3 all show increased gene expression at various times during a 12-day clinical course. The increased accumulation of IαI and HA was confirmed in the lungs of infected mice using immunohistochemistry and quantitative digital pathology. Western blots confirmed increases in the IαI components in BALF and lung tissue at 6 days post-infection (dpi). Interestingly, HCs and bikunin recovered from BALF and plasma from mice 6 dpi with IAV, displayed differences in the HC composition by Western blot analysis and differences in bikunin's CS chain sulfation patterns by mass spectrometry analysis. This strongly suggests that the IαI components were synthesized in the lungs rather than translocated from the vascular compartment. HA was significantly increased in BALF at 6 dpi, and the HA recovered in BALF and lung tissues were modified with HCs indicating the presence of an HC•HA matrix. In vitro experiments using polyinosinic-polycytidylic acid (poly(I:C)) treated mouse lung fibroblasts (MLF) showed that modification of HA with HCs increased cell-associated HA, and that this increase was due to the retention of HA in the MLF glycocalyx. In vitro studies of leukocyte adhesion showed differential binding of lymphoid (Hut78), monocyte (U937), and neutrophil (dHL60) cell lines to HA and HC•HA matrices. Hut78 cells adhered to immobilized HA in a size and concentration-dependent manner. In contrast, the binding of dHL60 and U937 cells depended on generating a HC•HA matrix by MLF. Our in vivo findings, using multiple bronchoalveolar lavages, correlated with our in vitro findings in that lymphoid cells bound more tightly to the HA-glycocalyx in the lungs of influenza-infected mice than neutrophils and mononuclear phagocytes (MNPs). The neutrophils and MNPs were associated with a HC•HA matrix and were more readily lavaged from the lungs. In conclusion, this work shows increased IαI and HA accumulation and the formation of a HC•HA matrix in mouse lungs post-IAV infection. The formation of HA and HC•HA matrices could potentially create specific microenvironments in the lungs for immune cell recruitment and activation during IAV infection.

Structural insights into the biological functions of the long pentraxin PTX3

Soluble pattern recognition molecules (PRMs) are a heterogenous group of proteins that recognize pathogen- and danger-associated molecular patterns (PAMPs and DAMPs, respectively), and cooperate with cell-borne receptors in the orchestration of innate and adaptive immune responses to pathogenic insults and tissue damage. Amongst soluble PRMs, pentraxins are a family of highly conserved proteins with distinctive structural features. Originally identified in the early 1990s as an early inflammatory gene, PTX3 is the prototype of long pentraxins. Unlike the short pentraxin C reactive protein (CRP), whose expression is mostly confined to the liver, PTX3 is made by several immune and non-immune cells at sites of infection and inflammation, where it intercepts fundamental aspects of infection immunity, inflammation, and tissue remodeling. Of note, PTX3 cross talks to components of the complement system to control cancer-related inflammation and disposal of pathogens. Also, it is an essential component of inflammatory extracellular matrices (ECMs) through crosslinking of hyaluronic acid and turn-over of provisional fibrin networks that assemble at sites of tissue injury. This functional diversity is mediated by unique structural characteristics whose fine details have been unveiled only recently. Here, we revisit the structure/function relationships of this long pentraxin in light of the most recent advances in its structural biology, with a focus on the interplay with complement and the emerging roles as a component of the ECM. Differences to and similarities with the short pentraxins are highlighted and discussed.

The recombinant Link module of human TSG-6 suppresses cartilage damage in models of osteoarthritis: A potential disease-modifying OA drug

OBJECTIVE

To investigate the role of endogenous TSG-6 in human osteoarthritis (OA) and assess the disease-modifying potential of a TSG-6-based biological treatment in cell, explant and animal models of OA.

DESIGN

Knee articular cartilages from OA patients were analyzed for TSG-6 protein and mRNA expression using immunohistochemistry and RNAscope, respectively. The inhibitory activities of TSG-6 and its isolated Link module (Link_TSG6) on cytokine-induced degradation of OA cartilage explants were compared. Human mesenchymal stem/stromal cell-derived chondrocyte pellet cultures were used to determine the effects of Link_TSG6 and full-length TSG-6 on IL-1α-, IL-1β-, or TNF-stimulated ADAMTS4, ADAMTS5, and MMP13 mRNA expression. Link_TSG6 was administered i.a. to the rat ACLTpMMx model; cartilage damage and tactile allodynia were assessed.

RESULTS

TSG-6 is predominantly associated with chondrocytes in regions of cartilage damage where high TSG-6 expression aligns with low MMP13, the major collagenase implicated in OA progression. Link_TSG6 is more potent than full-length TSG-6 at inhibiting cytokine-mediated matrix breakdown in human OA cartilage explants;>50% of donor cartilages, from 59 tested, were responsive to Link_TSG6 treatment. Link_TSG6 also displayed more potent effects in 3D pellet cultures, suppressing ADAMTS4, ADAMTS5, and MMP13 gene expression, which was consistent with reduced aggrecanase and collagenase activities in explant cultures. Link_TSG6 treatment reduced touch-evoked pain behavior and dose-dependently inhibited cartilage damage in a rodent model of surgically-induced OA.

CONCLUSIONS

Link_TSG6 has enhanced chondroprotective activity compared to the full-length TSG-6 protein and shows potential as a disease modifying OA drug via its inhibition of aggrecanase and collagenase activity.

Characterization of the Involvement of Tumour Necrosis Factor (TNF)-α-Stimulated Gene 6 (TSG-6) in Ischemic Brain Injury Caused by Middle Cerebral Artery Occlusion in Mouse

The identification of novel targets to modulate the immune response triggered by cerebral ischemia is crucial to promote the development of effective stroke therapeutics. Since tumour necrosis factor (TNF)-α-stimulated gene 6 (TSG-6), a hyaluronate (HA)-binding protein, is involved in the regulation of immune and stromal cell functions in acute neurodegeneration, we aimed to characterize its involvement in ischemic stroke. Transient middle cerebral artery occlusion (1 h MCAo, followed by 6 to 48 of reperfusion) in mice resulted in a significant elevation in cerebral TSG-6 protein levels, mainly localized in neurons and myeloid cells of the lesioned hemisphere. These myeloid cells were clearly infiltrating from the blood, strongly suggesting that brain ischemia also affects TSG-6 in the periphery. Accordingly, TSG-6 mRNA expression was elevated in peripheral blood mononuclear cells (PBMCs) from patients 48 h after ischemic stroke onset, and TSG-6 protein expression was higher in the plasma of mice subjected to 1 h MCAo followed by 48 h of reperfusion. Surprisingly, plasma TSG-6 levels were reduced in the acute phase (i.e., within 24 h of reperfusion) when compared to sham-operated mice, supporting the hypothesis of a detrimental role of TSG-6 in the early reperfusion stage. Accordingly, systemic acute administration of recombinant mouse TSG-6 increased brain levels of the M2 marker Ym1, providing a significant reduction in the brain infarct volume and general neurological deficits in mice subjected to transient MCAo. These findings suggest a pivotal role of TSG-6 in ischemic stroke pathobiology and underscore the clinical relevance of further investigating the mechanisms underlying its immunoregulatory role.

Tumor Necrosis Factor (TNF)-α-Stimulated Gene 6 (TSG-6): A Promising Immunomodulatory Target in Acute Neurodegenerative Diseases

Tumor necrosis factor (TNF)-α-stimulated gene 6 (TSG-6), the first soluble chemokine-binding protein to be identified in mammals, inhibits chemotaxis and transendothelial migration of neutrophils and attenuates the inflammatory response of dendritic cells, macrophages, monocytes, and T cells. This immunoregulatory protein is a pivotal mediator of the therapeutic efficacy of mesenchymal stem/stromal cells (MSC) in diverse pathological conditions, including neuroinflammation. However, TSG-6 is also constitutively expressed in some tissues, such as the brain and spinal cord, and is generally upregulated in response to inflammation in monocytes/macrophages, dendritic cells, astrocytes, vascular smooth muscle cells and fibroblasts. Due to its ability to modulate sterile inflammation, TSG-6 exerts protective effects in diverse degenerative and inflammatory diseases, including brain disorders. Emerging evidence provides insights into the potential use of TSG-6 as a peripheral diagnostic and/or prognostic biomarker, especially in the context of ischemic stroke, whereby the pathobiological relevance of this protein has also been demonstrated in patients. Thus, in this review, we will discuss the most recent data on the involvement of TSG-6 in neurodegenerative diseases, particularly focusing on relevant anti-inflammatory and immunomodulatory functions. Furthermore, we will examine evidence suggesting novel therapeutic opportunities that can be afforded by modulating TSG-6-related pathways in neuropathological contexts and, most notably, in stroke.

Dysfunctional Extracellular Matrix Remodeling Supports Perianal Fistulizing Crohn's Disease by a Mechanoregulated Activation of the Epithelial-to-Mesenchymal Transition

BACKGROUND AND AIMS

Perianal fistula represents one of the most disabling manifestations of Crohn's disease (CD) due to complete destruction of the affected mucosa, which is replaced by granulation tissue and associated with changes in tissue organization. To date, the molecular mechanisms underlying perianal fistula formation are not well defined. Here, we dissected the tissue changes in the fistula area and addressed whether a dysregulation of extracellular matrix (ECM) homeostasis can support fistula formation.

METHODS

Surgical specimens from perianal fistula tissue and the surrounding region of fistulizing CD were analyzed histologically and by RNA sequencing. Genes significantly modulated were validated by real-time polymerase chain reaction, Western blot, and immunofluorescence assays. The effect of the protein product of TNF-stimulated gene-6 (TSG-6) on cell morphology, phenotype, and ECM organization was investigated with endogenous lentivirus-induced overexpression of TSG-6 in Caco-2 cells and with exogenous addition of recombinant human TSG-6 protein to primary fibroblasts from region surrounding fistula. Proliferative and migratory assays were performed.

RESULTS

A markedly different organization of ECM was found across fistula and surrounding fistula regions with an increased expression of integrins and matrix metalloproteinases and hyaluronan (HA) staining in the fistula, associated with increased newly synthesized collagen fibers and mechanosensitive proteins. Among dysregulated genes associated with ECM, TNFAI6 (gene encoding for TSG-6) was as significantly upregulated in the fistula compared with area surrounding fistula, where it promoted the pathological formation of complexes between heavy chains from inter-alpha-inhibitor and HA responsible for the formation of a crosslinked ECM. There was a positive correlation between TNFAI6 expression and expression of mechanosensitive genes in fistula tissue. The overexpression of TSG-6 in Caco-2 cells promoted migration, epithelial-mesenchymal transition, transcription factor SNAI1, and HA synthase (HAs) levels, while in fibroblasts, isolated from the area surrounding the fistula, it promoted an activated phenotype. Moreover, the enrichment of an HA scaffold with recombinant human TSG-6 protein promoted collagen release and increase of SNAI1, ITGA4, ITGA42B, and PTK2B genes, the latter being involved in the transduction of responses to mechanical stimuli.

CONCLUSIONS

By mediating changes in the ECM organization, TSG-6 triggers the epithelial-mesenchymal transition transcription factor SNAI1 through the activation of mechanosensitive proteins. These data point to regulators of ECM as new potential targets for the treatment of CD perianal fistula.

Noncovalent hyaluronan crosslinking by TSG-6: Modulation by heparin, heparan sulfate, and PRG4

The size, conformation, and organization of the glycosaminoglycan hyaluronan (HA) affect its interactions with soluble and cell surface-bound proteins. HA that is induced to form stable networks has unique biological properties relative to unmodified soluble HA. AlphaLISA assay technology offers a facile and general experimental approach to assay protein-mediated networking of HA in solution. Connections formed between two end-biotinylated 50 kDa HA (bHA) chains can be detected by signal arising from streptavidin-coated donor and acceptor beads being brought into close proximity when the bHA chains are bridged by proteins. We observed that incubation of bHA with the protein TSG-6 (tumor necrosis factor alpha stimulated gene/protein 6, TNFAIP/TSG-6) leads to dimerization or higher order multimerization of HA chains in solution. We compared two different heparin (HP) samples and two heparan sulfate (HS) samples for the ability to disrupt HA crosslinking by TSG-6. Both HP samples had approximately three sulfates per disaccharide, and both were effective in inhibiting HA crosslinking by TSG-6. HS with a relatively high degree of sulfation (1.75 per disaccharide) also inhibited TSG-6 mediated HA networking, while HS with a lower degree of sulfation (0.75 per disaccharide) was less effective. We further identified Proteoglycan 4 (PRG4, lubricin) as a TSG-6 ligand, and found it to inhibit TSG-6-mediated HA crosslinking. The effects of HP, HS, and PRG4 on HA crosslinking by TSG-6 were shown to be due to HP/HS/PRG4 inhibition of HA binding to the Link domain of TSG-6. Using the AlphaLISA platform, we also tested other HA-binding proteins for ability to create HA networks. The G1 domain of versican (VG1) effectively networked bHA in solution but required a higher concentration than TSG-6. Cartilage link protein (HAPLN1) and the HA binding protein segment of aggrecan (HABP, G1-IGD-G2) showed only low and variable magnitude HA networking effects. This study unambiguously demonstrates HA crosslinking in solution by TSG-6 and VG1 proteins, and establishes PRG4, HP and highly sulfated HS as modulators of TSG-6 mediated HA crosslinking.

Defining the versican interactome in lung health and disease

The extracellular matrix (ECM) imparts critical mechanical and biochemical information to cells in the lungs. Proteoglycans are essential constituents of the ECM and play a crucial role in controlling numerous biological processes, including regulating cellular phenotype and function. Versican, a chondroitin sulfate proteoglycan required for embryonic development, is almost absent from mature, healthy lungs and is reexpressed and accumulates in acute and chronic lung disease. Studies using genetically engineered mice show that the versican-enriched matrix can be pro- or anti-inflammatory depending on the cellular source or disease process studied. The mechanisms whereby versican develops a contextual ECM remain largely unknown. The primary goal of this review is to provide an overview of the interaction of versican with its many binding partners, the "versican interactome," and how through these interactions, versican is an integrator of complex extracellular information. Hopefully, the information provided in this review will be used to develop future studies to determine how versican and its binding partners can develop contextual ECMs that control select biological processes. Although this review focuses on versican and the lungs, what is described can be extended to other proteoglycans, tissues, and organs.

A quartz crystal microbalance method to quantify the size of hyaluronan and other glycosaminoglycans on surfaces

Hyaluronan (HA) is a major component of peri- and extra-cellular matrices and plays important roles in many biological processes such as cell adhesion, proliferation and migration. The abundance, size distribution and presentation of HA dictate its biological effects and are also useful indicators of pathologies and disease progression. Methods to assess the molecular mass of free-floating HA and other glycosaminoglycans (GAGs) are well established. In many biological and technological settings, however, GAGs are displayed on surfaces, and methods to obtain the size of surface-attached GAGs are lacking. Here, we present a method to size HA that is end-attached to surfaces. The method is based on the quartz crystal microbalance with dissipation monitoring (QCM-D) and exploits that the softness and thickness of films of grafted HA increase with HA size. These two quantities are sensitively reflected by the ratio of the dissipation shift (ΔD) and the negative frequency shift (- Δf) measured by QCM-D upon the formation of HA films. Using a series of size-defined HA preparations, ranging in size from ~ 2 kDa tetrasaccharides to ~ 1 MDa polysaccharides, we establish a monotonic yet non-linear standard curve of the ΔD/ - Δf ratio as a function of HA size, which reflects the distinct conformations adopted by grafted HA chains depending on their size and surface coverage. We demonstrate that the standard curve can be used to determine the mean size of HA, as well as other GAGs, such as chondroitin sulfate and heparan sulfate, of preparations of previously unknown size in the range from 1 to 500 kDa, with a resolution of better than 10%. For polydisperse samples, our analysis shows that the process of surface-grafting preferentially selects smaller GAG chains, and thus reduces the average size of GAGs that are immobilised on surfaces comparative to the original solution sample. Our results establish a quantitative method to size HA and other GAGs grafted on surfaces, and also highlight the importance of sizing GAGs directly on surfaces. The method should be useful for the development and quality control of GAG-based surface coatings in a wide range of research areas, from molecular interaction analysis to biomaterials coatings.

Hyaluronan network: a driving force in cancer progression

Hyaluronan is one of the most abundant macromolecules of the extracellular matrix and regulates several physiological cell and tissue properties. However, hyaluronan has been shown to accumulate together with its receptors in various cancers. In tumors, accumulation of hyaluronan system components (hyaluronan synthesizing/degrading enzymes and interacting proteins) associates with poor outcomes of the patients. In this article, we review the main roles of hyaluronan in normal physiology and cancer, and further discuss the targeting of hyaluronan system as an applicable therapeutic strategy.

The role of Hyaluronan synthesis and degradation in the critical respiratory illness COVID-19

Hyaluronan (HA) is a polysaccharide found in all tissues as an integral component of the extracellular matrix (ECM) that plays a central regulatory role in inflammation. In fact, HA matrices are increasingly considered as a barometer of inflammation. A number of proteins specifically recognize the HA structure and these interactions modify cell behavior and control the stability of the ECM. Moreover, inflamed airways are remarkably rich with HA and are associated with various inflammatory diseases including cystic fibrosis, influenza, sepsis, and more recently coronavirus disease 2019 (COVID-19). COVID-19 is a worldwide pandemic caused by a novel coronavirus called SARS-CoV-2, and infected individuals have a wide range of disease manifestations ranging from asymptomatic to severe illness. Critically ill COVID-19 patient cases are frequently complicated by development of acute respiratory distress syndrome (ARDS), which typically leads to poor outcomes with high mortality rate. In general, ARDS is characterized by poor oxygenation accompanied with severe lung inflammation, damage, and vascular leakage and has been suggested to be linked to an accumulation of HA within the airways. Here, we provide a succinct overview of known inflammatory mechanisms regulated by HA in general, and those both observed and postulated in critically ill patients with COVID-19.

Influence of Hyaluronan Density on the Behavior of Breast Cancer Cells with Different CD44 Expression

Molecular gradients are common in biosystems and play an essential role in physiological and pathological processes. During carcinogenesis, for example, hyaluronan (HA) homeostasis is dysregulated by cancer cells and the altered synthesis and degradation processes result in the formation of HA gradients within the tumor microenvironment. Herein, a platform is developed to study the biological role of HA gradient in breast cancer cells. Cells with different aggressiveness and expression of CD44-the main HA receptor usually overexpressed in breast cancers, are selected for this study. The developed platform is compatible with several imaging modalities and allows assessment of cell density, morphology, CD44 expression, and cell motility in a function of HA density. Using high-throughput analysis, it is shown that cells that do not express CD44 do not change along the gradient, while CD44 positive cells respond differently to the HA gradient depending on the level of CD44 expression and HA density. This different response is associated with the activation of different signaling pathways by the CD44-HA interactions.

Deletion of TNFAIP6 Gene in Human Keratinocytes Demonstrates a Role for TSG-6 to Retain Hyaluronan Inside Epidermis

TSG-6 is a soluble protein secreted in the extracellular matrix by various cell types in response to inflammatory stimuli. TSG-6 interacts with extracellular matrix molecules, particularly hyaluronan (HA), and promotes cutaneous wound closure in mice. Between epidermal cells, the discrete extracellular matrix contains HA and a tiny amount of TSG-6. However, challenges imposed to keratinocytes in reconstructed human epidermis revealed strong induction of TSG-6 expression, after exposure to T helper type 2 cytokines to recapitulate the atopic dermatitis phenotype or after fungal infection that causes secretion of cytokines and antimicrobial peptides. After both types of challenge, enhanced release of TSG-6 happens simultaneously with increased HA production. TSG-6 deficiency in N/TERT keratinocytes was created by inactivating TNFAIP6 using CRISPR/Cas9. Some TSG-6 -/- keratinocytes analyzed through scratch assays tend to migrate more slowly but produce reconstructed human epidermis that exhibits normal morphology and differentiation. Few significant alterations were noticed by transcriptomic analysis. Nevertheless, reduced HA content in TSG-6 -/- reconstructed human epidermis was observed, along with enhanced HA release into the culture medium, and this phenotype was even more pronounced after the challenging conditions. Reintroduction of cells producing TSG-6 in reconstructed human epidermis reduced HA leakage. Our results show a role for TSG-6 in sequestering HA between epidermal cells in response to inflammation.

Epidermal Hyaluronan in Barrier Alteration-Related Disease

In skin, although the extracellular matrix (ECM) is highly developed in dermis and hypodermis, discrete intercellular spaces between cells of the living epidermal layers are also filled with ECM components. Herein, we review knowledge about structure, localization and role of epidermal hyaluronan (HA), a key ECM molecule. HA is a non-sulfated glycosaminoglycan non-covalently bound to proteins or lipids. Components of the basal lamina maintain some segregation between the epidermis and the underlying dermis, and all epidermal HA is locally synthesized and degraded. Functions of HA in keratinocyte proliferation and differentiation are still controversial. However, through interactions with partners, such as the TSG-6 protein, HA is involved in the formation, organization and stabilization of the epidermal ECM. In addition, epidermal HA is involved in the formation of an efficient epidermal barrier made of cornified keratinocytes. In atopic dermatitis (AD) with profuse alterations of the epidermal barrier, HA is produced in larger amounts by keratinocytes than in normal skin. Epidermal HA inside AD lesional skin is located in enlarged intercellular spaces, likely as the result of disease-related modifications of HA metabolism.

Role of the Extracellular Matrix in Alzheimer's Disease

Alzheimer’s disease (AD) is a neurodegenerative disease with complex pathological characteristics, whose etiology and pathogenesis are still unclear. Over the past few decades, the role of the extracellular matrix (ECM) has gained importance in neurodegenerative disease. In this review, we describe the role of the ECM in AD, focusing on the aspects of synaptic transmission, amyloid-β-plaque generation and degradation, Tau-protein production, oxidative-stress response, and inflammatory response. The function of ECM in the pathological process of AD will inform future research on the etiology and pathogenesis of AD.

Hyaluronic acid synthesis, degradation, and crosslinking in equine osteoarthritis: TNF-α-TSG-6-mediated HC-HA formation

BACKGROUND

TNF-α-stimulated gene 6 (TSG-6) protein, a TNF-α-responsive hyaladherin, possesses enzymatic activity that can catalyze covalent crosslinks of the polysaccharide hyaluronic acid (HA) to another protein to form heavy chain-hyaluronic acid (HC-HA) complexes in pathological conditions such as osteoarthritis (OA). Here, we examined HA synthase and inflammatory gene expression; synovial fluid HA, TNF-α, and viscosity; and TSG-6-mediated HC-HA complex formation in an equine OA model. The objectives of this study were to (1) evaluate the TNF-α-TSG-6-HC-HA signaling pathway across multiple joint tissues, including synovial membrane, cartilage, and synovial fluid, and (2) determine the impact of OA on synovial fluid composition and biophysical properties.

METHODS

HA and inflammatory cytokine concentrations (TNF-α, IL-1β, CCL2, 3, 5, and 11) were analyzed in synovial fluid from 63 OA and 25 control joints, and HA synthase (HAS1-3), TSG-6, and hyaluronan-degrading enzyme (HYAL2, HEXA) gene expression was measured in synovial membrane and cartilage. HA molecular weight (MW) distributions were determined using agarose gel electrophoresis and solid-state nanopore measurements, and HC-HA complex formation was detected via immunoblotting and immunofluorescence. SEC-MALS was used to evaluate TSG-6-mediated HA crosslinking, and synovial fluid and HA solution viscosities were analyzed using multiple particle-tracking microrheology and microfluidic measurements, respectively.

RESULTS

TNF-α concentrations were greater in OA synovial fluid, and TSG6 expression was upregulated in OA synovial membrane and cartilage. TSG-6-mediated HC-HA complex formation was greater in OA synovial fluid and tissues than controls, and HC-HA was localized to both synovial membrane and superficial zone chondrocytes in OA joints. SEC-MALS demonstrated macromolecular aggregation of low MW HA in the presence of TSG-6 and inter-α-inhibitor with concurrent increases in viscosity.

CONCLUSIONS

Synovial fluid TNF-α concentrations, synovial membrane and cartilage TSG6 gene expression, and HC-HA complex formation were increased in equine OA. Despite the ability of TSG-6 to induce macromolecular aggregation of low MW HA with resultant increases in the viscosity of low MW HA solutions in vitro, HA concentration was the primary determinant of synovial fluid viscosity rather than HA MW or HC-HA crosslinking. The TNF-α-TSG-6-HC-HA pathway may represent a potential therapeutic target in OA.

Immune response against the biomaterials used in 3D bioprinting of organs

Regenerative medicine has developed promising approaches for healing and replacing defective and damaged organs or tissues with functional ones. Three-dimensional (3D) bioprinting innovation has integrated a potential to design organs or tissues specific to the patient with the capability of rapid construction to fulfill the storage of organs and the need for transplantation. 3D bioprinting of organs has the main goal to develop a structural and functional organ or tissue mimic to the original one. The highly complex fabrication of tissue engineering scaffolds containing biomaterials, tissue models, and biomedical devices has made it possible to print small blood vessels to mimic organs to reduce organ or tissue rejection. 3D bioprinting has the concept of bioinks containing biomaterials that may trigger the immune responses in the body. Nevertheless, foreign body response (FBR) is mediated by various cell types such as B-cells, dendritic cells, macrophages, natural killer cells, neutrophils, and T-cells, and molecular signals such as antibodies (Abs), cytokines, and reactive radical species. Typically, the biomaterial is shielded by the fibrous encapsulation that is regulated by molecular signals. This review explored the progress in 3D bioprinting of vital organs and basic immune response against the biomaterials used in this approach. Thus, evaluating immune response against biomaterials used in 3D printed organs is necessary to mitigate tissue rejection after the transplantation.

Anti-inflammatory protein TNFα-stimulated gene-6 (TSG-6) reduces inflammatory response after brain injury in mice

BACKGROUND

Current research suggests that the glial scar surrounding penetrating brain injuries is instrumental in preserving the surrounding uninjured tissue by limiting the inflammatory response to the injury site. We recently showed that tumor necrosis factor (TNF)-stimulated gene-6 (TSG-6), a well-established anti-inflammatory molecule, is present within the glial scar. In the present study we investigated the role of TSG-6 within the glial scar using TSG-6 null and littermate control mice subjected to penetrating brain injuries.

RESULTS

Our findings show that mice lacking TSG-6 present a more severe inflammatory response after injury, which was correlated with an enlarged area of astrogliosis beyond the injury site.

CONCLUSION

Our data provides evidence that TSG-6 has an anti-inflammatory role within the glial scar.

Corrosion Behaviour and J774A.1 Macrophage Response to Hyaluronic Acid Functionalization of Electrochemically Reduced Graphene Oxide on Biomedical Grade CoCr

Improvements in the lubrication of metal–metal joint prostheses are of great clinical interest in order to minimize the particles released during wear–corrosion processes. In this work, electrochemically reduced graphene oxide (ErGO) on CoCr was functionalized with hyaluronic acid (ErGOHA). Functionalization was carried out by soaking for 24 h in phosphate buffer saline (PBS) solution containing 3 g/L hyaluronic acid (HA). The corrosion performance of CoCrErGO and CoCrErGOHA surfaces was studied by electrochemical impedance spectroscopy (EIS) for 7 days in PBS. Biocompatibility and cytotoxicity were studied in mouse macrophages J774A.1 cell line by the measurement of mitochondrial activity (WST-1 assay) and plasma membrane damage (LDH assay). The inflammatory response was examined through TNF-α and IL-10 cytokines in macrophages culture supernatants, used as indicators of pro-inflammatory and anti-inflammatory responses, respectively. EIS diagrams of CoCrErGOHA revealed two time constants: the first one, attributed to the hydration and diffusion processes of the HA layer adsorbed on ErGO, and the second one, the corrosion resistance of ErGOHA/CoCr interface. Macrophage assays showed better behavior on CoCrErGOHA than CoCr and CoCrErGO surfaces based on their biocompatible, cytotoxic, and inflammatory responses. Comparative analysis of IL-10 showed that functionalization with HA induces higher values of anti-inflammatory cytokine, suggesting an improvement in inflammatory behavior.

Abundance and size of hyaluronan in naked mole-rat tissues and plasma

Large amounts of ultra-high molecular weight hyaluronan (HA) have been described as the main cause of cancer resistance in naked mole-rats (Heterocephalus glaber, NMR). Our work examined HA metabolism in these rodents more closely. HA was localized and quantified using HA binding proteins. Its molecular weight was determined using size exclusion chromatography and gel electrophoresis, HA family gene expression using RNAseq analysis, and hyaluronidase activity using zymography. Guinea pigs (Cavia porcellus) and mice (Mus musculus) were used as controls for some experiments. We found that HA localization was similar in NMR, guinea pig, and mouse tissues but NMR had larger amounts and higher molecular weight (maximum, around 2.5 MDa) of HA in serum and almost all tissues tested. We could not find ultra-high molecular weight HA (≥ 4 MDa) in NMR samples, in contrast to previous descriptions. Hyaluronidase-1 had lower expression and activity in NMR than mouse lymph nodes. RNAseq results showed that, among HA family genes, Tnfaip6 and hyaluronidase-3 (Hyal3) were systematically overexpressed in NMR tissues. In conclusion, NMR samples, contrary to expectations, do not harbor ultra-high molecular weight HA, although its amount and average molecular weight are higher in NMR than in guinea pig tissues and serum. Although hyaluronidase expression and activity are lower in NMR than mouse lymph nodes, this not sufficient to explain the presence of high molecular weight HA. A different activity of the NMR HA synthases remains possible. These characteristics, together with extremely high Hyal3 and Tnfaip6 expression, may provide the NMR with a bespoke, and perhaps protective, HA metabolism.

Glycosaminoglycan-Protein Interactions and Their Roles in Human Disease

Glycosaminoglycans (GAGs) are a family of linear and negatively charged polysaccharides that exist ubiquitously on the human cell surface as well as in the extracellular matrix. GAGs interact with a wide range of proteins, including proteases, growth factors, cytokines, chemokines and adhesion molecules, enabling them to mediate many physiological processes, such as protein function, cellular adhesion and signaling. GAG-protein interactions participate in and intervene in a variety of human diseases, including cardiovascular disease, infectious disease, neurodegenerative diseases and tumors. The breakthrough in analytical tools and approaches during the last two decades has facilitated a greater understanding of the importance of GAG-protein interactions and their roles in human diseases. This review focuses on aspects of the molecular basis and mechanisms of GAG-protein interactions involved in human disease. The most recent advances in analytical tools, especially mass spectrometry-based GAG sequencing and binding motif characterization methods, are introduced. An update of selected families of GAG binding proteins is presented. Perspectives on development of novel therapeutics targeting specific GAG-protein interactions are also covered in this review.

Extracellular Matrix in Calcific Aortic Valve Disease: Architecture, Dynamic and Perspectives

Calcific Aortic Valve Disease (CAVD) is the most common valvular heart disease in developed countries and in the ageing population. It is strongly correlated to median age, affecting up to 13% of the population over the age of 65. Pathophysiological analysis indicates CAVD as a result of an active and degenerative disease, starting with sclerosis and chronic inflammation and then leaflet calcification, which ultimately can account for aortic stenosis. Although CAVD has been firstly recognized as a passive event mostly resulting from a degenerative aging process, much evidences suggests that calcification arises from different active processes, involving both aortic valve-resident cells (valve endothelial cells, valve interstitial cells, mesenchymal stem cells, innate immunity cells) and circulating cells (circulating mesenchymal cells, immunity cells). Moreover, a role for the cell-derived "matrix vesicles" and extracellular matrix (ECM) components has also been recognized. The aim of this work is to review the cellular and molecular alterations occurring in aortic valve during CAVD pathogenesis, focusing on the role of ECM in the natural course of the disease.

Basic Biology of Extracellular Matrix in the Cardiovascular System, Part 1/4: JACC Focus Seminar

The extracellular matrix (ECM) is the noncellular component of tissues in the cardiovascular system and other organs throughout the body. It is formed of filamentous proteins, proteoglycans, and glycosaminoglycans, which extensively interact and whose structure and dynamics are modified by cross-linking, bridging proteins, and cleavage by matrix degrading enzymes. The ECM serves important structural and regulatory roles in establishing tissue architecture and cellular function. The ECM of the developing heart has unique properties created by its emerging contractile nature; similarly, ECM lining blood vessels is highly elastic in order to sustain the basal and pulsatile forces imposed on their walls throughout life. In this part 1 of a 4-part JACC Focus Seminar, we focus on the role, function, and basic biology of the ECM in both heart development and in the adult.

A Role for HAPLN1 During Phenotypic Modulation of Human Lung Fibroblasts In Vitro

Hyaluronan and proteoglycan link protein 1 (HAPLN1) stabilizes interactions between two important extracellular matrix (ECM) macromolecules, versican and hyaluronan, which facilitate proliferation of fibroblasts and their conversion to myofibroblasts. However, the role of HAPLN1 in these events has not been studied. Using immunocytochemistry, cellular and ECM locations of HAPLN1 were evaluated in cultured human lung fibroblasts during proliferation and conversion to myofibroblasts. HAPLN1 localized to pericellular matrices, associating with both versican and hyaluronan in the ECM and on the cell surface. Nuclear and total HAPLN1 immunostaining increased after myofibroblast induction. Confocal microscopy showed HAPLN1 predominant in the ECM under cells while versican predominated above cells. Versican and HAPLN1 were also juxtaposed in columnar inclusions in the cytoplasm and nucleus. Nuclear HAPLN1 staining in interphase cells redistributed to the cytosol during mitosis. In the absence of TGF-β1, addition of exogenous bovine HAPLN1 (together with aggrecan G1) facilitated myofibroblast formation, as seen by significant upregulation of α-smooth muscle actin (SMA) staining, while adding full-length bovine versican had no effect. Increased compaction of hyaluronan-rich ECM suggests that HAPLN1 plus G1 addition affects hyaluronan networks and myofibroblast formation. These observations demonstrate changes in both extracellular and intracellular localization of HAPLN1 during fibroblast proliferation and myofibroblast conversion suggesting a possible role in fibrotic remodeling.

The microvascular extracellular matrix in brains with Alzheimer's disease neuropathologic change (ADNC) and cerebral amyloid angiopathy (CAA)

BACKGROUND

The microvasculature (MV) of brains with Alzheimer's disease neuropathologic change (ADNC) and cerebral amyloid angiopathy (CAA), in the absence of concurrent pathologies (e.g., infarctions, Lewy bodies), is incompletely understood.

OBJECTIVE

To analyze microvascular density, diameter and extracellular matrix (ECM) content in association with ADNC and CAA.

METHODS

We examined samples of cerebral cortex and isolated brain microvasculature (MV) from subjects with the National Institute on Aging-Alzheimer's Association (NIA-AA) designations of not-, intermediate-, or high ADNC and from subjects with no CAA and moderate-severe CAA. Cases for all groups were selected with no major (territorial) strokes, ≤ 1 microinfarct in screening sections, and no Lewy body pathology. MV density and diameter were measured from cortical brain sections. Levels of basement membrane (BM) ECM components, the protein product of TNF-stimulated gene-6 (TSG-6), and the ubiquitous glycosaminoglycan hyaluronan (HA) were assayed by western blots or HA ELISA of MV lysates.

RESULTS

We found no significant changes in MV density or diameter among any of the groups. Levels of BM laminin and collagen IV (col IV) were lower in MV isolated from the high ADNC vs. not-ADNC groups. In contrast, BM laminin was significantly higher in MV from the moderate-severe CAA vs. the no CAA groups. TSG-6 and HA content were higher in the presence of both high ADNC and CAA, whereas levels of BM fibronectin and perlecan were similar among all groups.

CONCLUSIONS

Cortical MV density and diameter are not appreciably altered by ADNC or CAA. TSG-6 and HA are increased in both ADNC and CAA, with laminin and col IV decreased in the BM of high ADNC, but laminin increased in moderate-severe CAA. These results show that changes in the ECM occur in AD and CAA, but independently of one another, and likely reflect on the regional functioning of the brain microvasculature.

Diverse Roles for Hyaluronan and Hyaluronan Receptors in the Developing and Adult Nervous System

Hyaluronic acid (HA) plays a vital role in the extracellular matrix of neural tissues. Originally thought to hydrate tissues and provide mechanical support, it is now clear that HA is also a complex signaling molecule that can regulate cell processes in the developing and adult nervous systems. Signaling properties are determined by molecular weight, bound proteins, and signal transduction through specific receptors. HA signaling regulates processes such as proliferation, differentiation, migration, and process extension in a variety of cell types including neural stem cells, neurons, astrocytes, microglia, and oligodendrocyte progenitors. The synthesis and catabolism of HA and the expression of HA receptors are altered in disease and influence neuroinflammation and disease pathogenesis. This review discusses the roles of HA, its synthesis and breakdown, as well as receptor expression in neurodevelopment, nervous system function and disease.

An in vitro study to assess the effect of hyaluronan-based gels on muscle-derived cells: Highlighting a new perspective in regenerative medicine

Hyaluronan (HA) is a nonsulfated glycosaminoglycan that has been widely used for biomedical applications. Here, we have analyzed the effect of HA on the rescue of primary cells under stress as well as its potential to recover muscle atrophy and validated the developed model in vitro using primary muscle cells derived from rats. The potentials of different HAs were elucidated through comparative analyses using pharmaceutical grade a) high (HHA) and b) low molecular weight (LHA) hyaluronans, c) hybrid cooperative complexes (HCC) of HA in three experimental set-ups. The cells were characterized based on the expression of myogenin, a muscle-specific biomarker, and the proliferation was analyzed using Time-Lapse Video Microscopy (TLVM). Cell viability in response to H₂O₂ challenge was evaluated by 3-[4,5-dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay, and the expression of the superoxide dismutase enzyme (SOD-2) was assessed by western blotting. Additionally, in order to establish an in vitro model of atrophy, muscle cells were treated with tumor necrosis factor-alpha (TNF-α), along with hyaluronans. The expression of Atrogin, MuRF-1, nuclear factor kappa-light-chain-enhancer of activated B-cells (NF-kB), and Forkhead-box-(Fox)-O-3 (FoxO3a) was evaluated by western blotting to elucidate the molecular mechanism of atrophy. The results showed that HCC and HHA increased cell proliferation by 1.15 and 2.3 folds in comparison to un-treated cells (control), respectively. Moreover, both pre- and post-treatments of HAs restored the cell viability, and the SOD-2 expression was found to be reduced by 1.5 fold in HA-treated cells as compared to the stressed condition. Specifically in atrophic stressed cells, HCC revealed a noteworthy beneficial effect on the myogenic biomarkers indicating that it could be used as a promising platform for tissue regeneration with specific attention to muscle cell protection against stressful agents.

Redox-Responsive Coordination Polymers of Dopamine-Modified Hyaluronic Acid with Copper and 6-Mercaptopurine for Targeted Drug Delivery and Improvement of Anticancer Activity against Cancer Cells

Dopamine-modified hyaluronic acid (HA-DOP) was chosen as the drug carrier in this study, and Cu²⁺ was selected from among Cu²⁺, Zn²⁺, Fe²⁺, and Ca²⁺ as the central atom. 6-Mercaptopurine (6-MP) was conjugated with HA through a coordination reaction. HA-DOP-copper-MP (HA-DOP-Cu-MP), a redox-responsive coordination polymer prodrug, was prepared. The drug loading was 49.5 mg/g, the encapsulation efficiency was 70.18%, and the particle size was 173.5 nm. HA-DOP-Cu-MP released rapidly in the release medium containing reduced glutathione (GSH), and the accumulated release exceeded 94% in 2 h. In the release medium without GSH, the drug release rate was slow, with only 15% of the 6-MP released in 24 h. Cell uptake experiments revealed the CD44 targeting of HA. Cell viability assays showed that the cytotoxicity of HA-DOP-Cu-MP was higher than that of free 6-MP. Indeed, HA-DOP-Cu-MP is very toxic to cancer cells. In this paper, the redox-responsive drug delivery system was synthesized by a coordination reaction. The tumour targeting and tumour cytotoxicity of 6-MP were improved.

Enhanced avidin binding to lipid bilayers using PDP-PE lipids with PEG-biotin linkers

Two of the most important aspects of lipid bilayers that have increased their popularity in the field of nanotechnology and biosensors are their fluid nature, which is highly beneficial in ensuring the spatial organization of attached molecules, and the relative ease in which they can be manipulated to change the surface chemistry. Here we have used two different types of functionalized lipids to study the interaction of avidin, which is a common approach to attach further ligands for study. We have tested the commonly used Biotinyl-Cap-PE lipids at different molar percentages and reveal that avidin is not evenly distributed, but forms what looks like clusters even at low percentage occupancy which hampers the level of avidin that can be associated with the surface. We have then successfully employed the novel strategy of using PDP-PE lipids which contain a reducible disulphide to which we added maleamide-PEG-biotin spacers of different lengths. There is a more even distribution of avidin on these layers and thereby increasing the amount and efficiency of avidin association. The reduced levels of avidin that was being associated with the Biotinyl-Cap-PE layers as compared to the PDP-PE lipids could be analysed with QCM-D and interferometry approaches, but it was only with SEEC microscopy that the reason for the reduced occupancy was resolved.

Proteomics reveals different pathological processes of adipose tissue, liver, and skeletal muscle under insulin resistance

Type 2 diabetes mellitus is the most common type of diabetes, and insulin resistance (IR) is its core pathological mechanism. Proteomics is an ingenious and promising Omics technology that can comprehensively describe the global protein expression profiling of body or specific tissue, and is widely applied to the study of molecular mechanisms of diseases. In this paper, we focused on insulin target organs: adipose tissue, liver, and skeletal muscle, and analyzed the different pathological processes of IR in these three tissues based on proteomics research. By literature studies, we proposed that the main pathological processes of IR among target organs were diverse, which showed unique characteristics and focuses. We further summarized the differential proteins in target organs which were verified to be related to IR, and discussed the proteins that may play key roles in the emphasized pathological processes, aiming at discovering potentially specific differential proteins of IR, and providing new ideas for pathological mechanism research of IR.

Hyaluronan Accelerates Intestinal Mucosal Healing through Interaction with TSG-6

Hyaluronan (HA) has proven to be beneficial in the treatment of several diseases. Recently, it has been shown that the local application of HA (IBD98E) improves endoscopic and clinical outcomes in subjects with active distal ulcerative colitis (UC). However, the mechanisms by which this polysaccharide exerts its beneficial effects are unclear. Here, we demonstrated that HA treatment in vitro and in vivo improved mucosal healing by accelerating intestinal epithelial regeneration. Indeed, mice treated with HA showed a faster recovery from colitis and reduced endoscopic signs of mucosal inflammation compared to those receiving saline. Furthermore, histological analysis revealed less ulcerated mucosa in mice treated with HA, characterized by re-epithelialized areas. TSG-6, the secreted product of TNF-stimulated gene-6, is an HA-binding protein shown previously to have tissue-protective properties and promote wound healing. Mucosal levels of TSG-6 increased in UC patients compared to the healthy controls and also after wounding in mice. TSG-6 deletion prevented the beneficial properties of HA in mucosal wound repair, suggesting that the interaction of HA with TSG-6 is crucial for intestinal epithelial regeneration. Overall these results are consistent with HA having a therapeutic effect via the promotion of mucosal healing in patients with ulcerative colitis.

The extracellular matrix of the blood-brain barrier: structural and functional roles in health, aging, and Alzheimer's disease

There is increasing interest in defining the location, content, and role of extracellular matrix (ECM) components in brain structure and function during development, aging, injury, and neurodegeneration. Studies in vivo confirm brain ECM has a dynamic composition with constitutive and induced alterations that impact subsequent cell-cell and cell-matrix interactions. Moreover, it is clear that for any given ECM component, the brain region, and cell type within that location, determines the direction, magnitude, and composition of those changes. This review will examine the ECM at the neurovascular unit (NVU) and the blood-brain barrier (BBB) within the NVU. The discussion will begin at the glycocalyx ECM on the luminal surface of the vasculature, and progress to the abluminal side with a focus on changes in basement membrane ECM during aging and neurodegeneration.

TNF-Stimulated Gene-6 Is a Key Regulator in Switching Stemness and Biological Properties of Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) are well established to have promising therapeutic properties. TNF-stimulated gene-6 (TSG-6), a potent tissue-protective and anti-inflammatory factor, has been demonstrated to be responsible for a significant part of the tissue-protecting properties mediated by MSCs. Nevertheless, current knowledge about the biological function of TSG-6 in MSCs is limited. Here, we demonstrated that TSG-6 is a crucial factor that influences many functional properties of MSCs. The transcriptomic sequencing analysis of wild-type (WT) and TSG-6^-/- -MSCs shows that the loss of TSG-6 expression leads to the perturbation of several transcription factors, cytokines, and other key biological pathways. TSG-6^-/- -MSCs appeared morphologically different with dissimilar cytoskeleton organization, significantly reduced size of extracellular vesicles, decreased cell proliferative rate, and loss of differentiation abilities compared with the WT cells. These cellular effects may be due to TSG-6-mediated changes in the extracellular matrix (ECM) environment. The supplementation of ECM with exogenous TSG-6, in fact, rescued cell proliferation and changes in morphology. Importantly, TSG-6-deficient MSCs displayed an increased capacity to release interleukin-6 conferring pro-inflammatory and pro-tumorigenic properties to the MSCs. Overall, our data provide strong evidence that TSG-6 is crucial for the maintenance of stemness and other biological properties of murine MSCs.

Effect of calcium ions and pH on the morphology and mechanical properties of hyaluronan brushes

Hyaluronan (HA) is a linear, regular polysaccharide that plays as a chief structural and functional component in peri- and extracellular matrices, thus contributing significantly to many basic cellular processes. To understand more comprehensively the response of the supramolecular organization of HA polymers to changes in their aqueous environment, we study the effects of Ca2+ concentration and pH on the morphology and rigidity of films of end-grafted HA polymers on planar supports (HA brushes), as a well-defined in vitro model system of HA-rich matrices, by reflection interference contrast microscopy and quartz crystal microbalance. The thickness and softness of HA brushes decrease significantly with Ca2+ concentration but do not change with pH, within the physiological ranges of these parameters. The effect of Ca2+ on HA brush thickness is virtually identical to the effect of Na+ at 10-fold higher concentrations. Moreover, the thickness and softness of HA brushes decrease appreciably upon HA protonation at pH less than 6. Effects of pH and calcium ions are fully reversible over large parameter ranges. These findings are relevant for understanding the supramolecular organization and dynamics of HA-rich matrices in biological systems and will also benefit the rational design of synthetic HA-rich materials with tailored properties.

Increased Hyaluronan and TSG-6 in Association with Neuropathologic Changes of Alzheimer's Disease

Little is known about the extracellular matrix (ECM) during progression of AD pathology. Brain ECM is abundant in hyaluronan (HA), a non-sulfated glycosaminoglycan synthesized by HA synthases (HAS) 1-3 in a high molecular weight (MW) form that is degraded into lower MW fragments. We hypothesized that pathologic severity of AD is associated with increases in HA and HA-associated ECM molecules. To test this hypothesis, we assessed HA accumulation and size; HA synthases (HAS) 1-3; and the HA-stabilizing hyaladherin, TSG-6 in parietal cortex samples from autopsied research subjects with not AD (CERAD = 0, Braak = 0- II, n = 12-21), intermediate AD (CERAD = 2, Braak = III-IV, n = 13-18), and high AD (CERAD = 3, Braak = V-VI, n = 32-40) neuropathologic change. By histochemistry, HA was associated with deposits of amyloid and tau, and was also found diffusely in brain parenchyma, with overall HA quantity (measured by ELSA) significantly greater in brains with high AD neuropathology. Mean HA MW was similar among the samples. HAS2 and TSG-6 mRNA expression, and TSG-6 protein levels were significantly increased in high AD and both molecules were present in vasculature, NeuN-positive neurons, and Iba1-positive microglia. These results did not change when accounting for gender, advanced age (≥ 90 years versus <90 years), or the clinical diagnosis of dementia. Collectively, our results indicate a positive correlation between HA accumulation and AD neuropathology, and suggest a possible role for HA synthesis and metabolism in AD progression.

In vitro analysis of the role of tumor necrosis factor‑stimulated gene‑6 in keloid

An increasing number of studies have demonstrated that tumor necrosis factor-stimulated gene-6 (TSG-6) has a key role in the progression of fibrosis; however, the exact effects of TSG-6 in keloid fibroblasts (KFs) remain unknown. The aim of the current study was to investigate the role of TSG-6 in the pathogenesis of keloids. Primary fibroblasts from 10 patients with keloid were cultured and transfected with pLVX-Puro or pLVX-Puro-TSG-6. Alterations of TSG-6 expression were then determined by reverse transcription-polymerase chain reaction (RT-PCR) and regulation was observed in KFs transfected with pLVX-Puro-TSG-6. Compared with the control group, transfection with pLVX-Puro-TSG-6 induced growth suppression, cell apoptosis and G2/M arrest in KFs. In addition, the mitochondrial apoptosis pathway was activated in KFs transfected with pLVX-Puro-TSG-6. These findings indicate that TSG-6 is a novel regulator of keloid fibrogenesis, and thus could be used/targeted TSG-6 as a promising treatment for keloid.

Hyaluronan and Its Interactions With Immune Cells in the Healthy and Inflamed Lung

Hyaluronan is a hygroscopic glycosaminoglycan that contributes to both extracellular and pericellular matrices. While the production of hyaluronan is essential for mammalian development, less is known about its interaction and function with immune cells. Here we review what is known about hyaluronan in the lung and how it impacts immune cells, both at homeostasis and during lung inflammation and fibrosis. In the healthy lung, alveolar macrophages provide the first line of defense and play important roles in immunosurveillance and lipid surfactant homeostasis. Alveolar macrophages are surrounded by a coat of hyaluronan that is bound by CD44, a major hyaluronan receptor on immune cells, and this interaction contributes to their survival and the maintenance of normal alveolar macrophage numbers. Alveolar macrophages are conditioned by the alveolar environment to be immunosuppressive, and can phagocytose particulates without alerting an immune response. However, during acute lung infection or injury, an inflammatory immune response is triggered. Hyaluronan levels in the lung are rapidly increased and peak with maximum leukocyte infiltration, suggesting a role for hyaluronan in facilitating leukocyte access to the injury site. Hyaluronan can also be bound by hyaladherins (hyaluronan binding proteins), which create a provisional matrix to facilitate tissue repair. During the subsequent remodeling process hyaluronan concentrations decline and levels return to baseline as homeostasis is restored. In chronic lung diseases, the inflammatory and/or repair phases persist, leading to sustained high levels of hyaluronan, accumulation of associated immune cells and an inability to resolve the inflammatory response.

Practical guide to characterize biomolecule adsorption on solid surfaces (Review)

The control over the adsorption or grafting of biomolecules from a liquid to a solid interface is of fundamental importance in different fields, such as drug delivery, pharmaceutics, diagnostics, and tissue engineering. It is thus important to understand and characterize how biomolecules interact with surfaces and to quantitatively measure parameters such as adsorbed amount, kinetics of adsorption and desorption, conformation of the adsorbed biomolecules, orientation, and aggregation state. A better understanding of these interfacial phenomena will help optimize the engineering of biofunctional surfaces, preserving the activity of biomolecules and avoiding unwanted side effects. The characterization of molecular adsorption on a solid surface requires the use of analytical techniques, which are able to detect very low quantities of material in a liquid environment without modifying the adsorption process during acquisition. In general, the combination of different techniques will give a more complete characterization of the layers adsorbed onto a substrate. In this review, the authors will introduce the context, then the different factors influencing the adsorption of biomolecules, as well as relevant parameters that characterize their adsorption. They review surface-sensitive techniques which are able to describe different properties of proteins and polymeric films on solid two-dimensional materials and compare these techniques in terms of sensitivity, penetration depth, ease of use, and ability to perform "parallel measurements."

Long Pentraxin-3 Modulates the Angiogenic Activity of Fibroblast Growth Factor-2

Angiogenesis, the process of new blood vessel formation from pre-existing ones, plays a key role in various physiological and pathological conditions. Alteration of the angiogenic balance, consequent to the deranged production of angiogenic growth factors and/or natural angiogenic inhibitors, is responsible for angiogenesis-dependent diseases, including cancer. Fibroblast growth factor-2 (FGF2) represents the prototypic member of the FGF family, able to induce a complex “angiogenic phenotype” in endothelial cells in vitro and a potent neovascular response in vivo as the consequence of a tight cross talk between pro-inflammatory and angiogenic signals. The soluble pattern recognition receptor long pentraxin-3 (PTX3) is a member of the pentraxin family produced locally in response to inflammatory stimuli. Besides binding features related to its role in innate immunity, PTX3 interacts with FGF2 and other members of the FGF family via its N-terminal extension, thus inhibiting FGF-mediated angiogenic responses in vitro and in vivo. Accordingly, PTX3 inhibits the growth and vascularization of FGF-dependent tumors and FGF2-mediated smooth muscle cell proliferation and artery restenosis. Recently, the characterization of the molecular bases of FGF2/PTX3 interaction has allowed the identification of NSC12, the first low molecular weight pan-FGF trap able to inhibit FGF-dependent tumor growth and neovascularization. The aim of this review is to provide an overview of the impact of PTX3 and PTX3-derived molecules on the angiogenic, inflammatory, and tumorigenic activity of FGF2 and their potential implications for the development of more efficacious anti-FGF therapeutic agents to be used in those clinical settings in which FGFs play a pathogenic role.

Defective lung function following influenza virus is due to prolonged, reversible hyaluronan synthesis

Little is known about the impact of viral infections on lung matrix despite its important contribution to mechanical stability and structural support. The composition of matrix also indirectly controls inflammation by influencing cell adhesion, migration, survival, proliferation and differentiation. Hyaluronan is a significant component of the lung extracellular matrix and production and degradation must be carefully balanced. We have discovered an imbalance in hyaluronan production following resolution of a severe lung influenza virus infection, driven by hyaluronan synthase 2 from epithelial cells, endothelial cells and fibroblasts. Furthermore hyaluronan is complexed with inter-α-inhibitor heavy chains due to elevated TNF-stimulated gene 6 expression and sequesters CD44-expressing macrophages. We show that intranasal administration of exogenous hyaluronidase is sufficient to release inter-α-inhibitor heavy chains, reduce lung hyaluronan content and restore lung function. Hyaluronidase is already used to facilitate dispersion of co-injected materials in the clinic. It is therefore feasible that fibrotic changes following severe lung infection and inflammation could be overcome by targeting abnormal matrix production.

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Influenza causes prolonged changes in hyaluronan due to increased synthase activity

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Influenza induces persistent hyaluronan cross-linking by inter-alpha-inhibitor heavy chains

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Pockets of persistent hyaluronan are associated with CD44-expressing macrophages

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Digestion of hyaluronan with intranasal hyaluronidase restores lung function but upon cessation of treatment post-viral complications return