Decorin potentiates interferon-γ activity in a model of allergic inflammation

Identification of cross-talk pathways and PANoptosis-related genes in periodontitis and Alzheimer's disease by bioinformatics analysis and machine learning

Background and objectives

Periodontitis (PD), a chronic inflammatory disease, is a serious threat to oral health and is one of the risk factors for Alzheimer's disease (AD). A growing body of evidence suggests that the two diseases are closely related. However, current studies have not provided a comprehensive understanding of the common genes and common mechanisms between PD and AD. This study aimed to screen the crosstalk genes of PD and AD and the potential relationship between cross-talk and PANoptosis-related genes. The relationship between core genes and immune cells will be analyzed to provide new targets for clinical treatment.

Materials and methods

The PD and AD datasets were downloaded from the GEO database and differential expression analysis was performed to obtain DEGs. Overlapping DEGs had cross-talk genes linking PD and OP, and PANoptosis-related genes were obtained from a literature review. Pearson coefficients were used to compute cross-talk and PANoptosis-related gene correlations in the PD and AD datasets. Cross-talk genes were obtained from the intersection of PD and AD-related genes, protein-protein interaction(PPI) networks were constructed and cross-talk genes were identified using the STRING database. The intersection of cross-talk and PANoptosis-related genes was defined as cross-talk-PANoptosis genes. Core genes were screened using ROC analysis and XGBoost. PPI subnetwork, gene-biological process, and gene-pathway networks were constructed based on the core genes. In addition, immune infiltration on the PD and AD datasets was analyzed using the CIBERSORT algorithm.

Results

366 cross-talk genes were overlapping between PD DEGs and AD DEGs. The intersection of cross-talk genes with 109 PANoptosis-related genes was defined as cross-talk-PANoptosis genes. ROC and XGBoost showed that MLKL, DCN, IL1B, and IL18 were more accurate than the other cross-talk-PANoptosis genes in predicting the disease, as well as better in overall characterization. GO and KEGG analyses showed that the four core genes were involved in immunity and inflammation in the organism. Immune infiltration analysis showed that B cells naive, Plasma cells, and T cells gamma delta were significantly differentially expressed in patients with PD and AD compared with the normal group. Finally, 10 drugs associated with core genes were retrieved from the DGIDB database.

Conclusion

This study reveals the joint mechanism between PD and AD associated with PANoptosis. Analyzing the four core genes and immune cells may provide new therapeutic directions for the pathogenesis of PD combined with AD.

Characterisation of colorectal cancer by hierarchical clustering analyses for five stroma-related markers

Evidence for the tumour-supporting capacities of the tumour stroma has accumulated rapidly in colorectal cancer (CRC). Tumour stroma is composed of heterogeneous cells and components including cancer-associated fibroblasts (CAFs), small vessels, immune cells, and extracellular matrix proteins. The present study examined the characteristics of CAFs and collagen, major components of cancer stroma, by immunohistochemistry and Sirius red staining. The expression status of five independent CAF-related or stromal markers, decorin (DCN), fibroblast activation protein (FAP), podoplanin (PDPN), alpha-smooth muscle actin (ACTA2), and collagen, and their association with clinicopathological features and clinical outcomes were analysed. Patients with DCN-high tumours had a significantly worse 5-year survival rate (57.3% versus 79.0%; p = 0.044). Furthermore, hierarchical clustering analyses for these five markers identified three groups that showed specific characteristics: a solid group (cancer cell-rich, DCNLowPDPNLow); a PDPN-dominant group (DCNMidPDPNHigh); and a DCN-dominant group (DCNHighPDPNLow), with a significant association with patient survival (p = 0.0085). Cox proportional hazards model identified the PDPN-dominant group (hazard ratio = 0.50, 95% CI = 0.26-0.96, p = 0.037) as a potential favourable factor compared with the DCN-dominant group. Of note, DCN-dominant tumours showed the most advanced pT stage and contained the lowest number of CD8+ and FOXP3+ immune cells. This study has revealed that immunohistochemistry and special staining of five stromal factors with hierarchical clustering analyses could be used for the prognostication of patients with CRC. Cancer stroma-targeting therapies may be candidate treatments for patients with CRC.

Genome-wide identification of dysregulated alternative splicing and RNA-binding proteins involved in atopic dermatitis

Objectives: We explored the role and molecular mechanisms of RNA-binding proteins (RBPs) and their regulated alternative splicing events (RASEs) in the pathogenesis of atopic dermatitis (AD). Methods: We downloaded RNA-seq data (GSE121212) from 10 healthy control skin samples (healthy, Ctrl), 10 non-lesional skin samples with AD damage (non-lesional, NL), and 10 lesional skin samples with AD damage (lesional, LS). We performed the analysis of differentially expressed genes (DEGs), differentially expressed RBPs (DE-RBPs), alternative splicing (AS), functional enrichment, the co-expression of RBPs and RASEs, and quantitative polymerase chain reaction (qPCR). Results: We identified 60 DE-RBP genes by intersecting 2141 RBP genes from existing reports with overall 2697 DEGs. Most of the DE-RBP genes were found to be upregulated in the AD LS group and related to immune and apoptosis pathways. We observed different ASEs and RASEs among the healthy, AD NL, and AD LS groups. In particular, alt3p and alt5p were the main ASEs and RASEs in AD NL and AD LS groups, compared to the healthy group. Furthermore, we constructed co-expression networks of DE-RBPs and RAS, with particular enrichment in biological pathways including cytoskeleton organization, inflammation, and immunity. Subsequently, we selected seven genes that are commonly present in these three pathways to assess their expression levels in the peripheral blood mononuclear cells (PBMCs) from both healthy individuals and AD patients. The results demonstrated the upregulation of four genes (IFI16, S100A9, PKM, and ENO1) in the PBMCs of AD patients, which is highly consistent with DE-RBP genes analysis. Finally, we selected four RAS genes regulated by RBPs that were related to immune pathways and examined their RASEs in PBMCs from both AD patients and healthy controls. The results revealed an increased percentage of RASEs in the DDX60 gene in AD, which is highly consistent with AS analysis. Conclusion: Dysregulated RBPs and their associated RASEs may have a significant regulatory role in the development of AD and could be potential therapeutic targets in the future.

Control of tissue homeostasis by the extracellular matrix: Synthetic heparan sulfate as a promising therapeutic for periodontal health and bone regeneration

Proteoglycans are core proteins associated with carbohydrate/sugar moieties that are highly variable in disaccharide composition, which dictates their function. These carbohydrates are named glycosaminoglycans, and they can be attached to proteoglycans or found free in tissues or on cell surfaces. Glycosaminoglycans such as hyaluronan, chondroitin sulfate, dermatan sulfate, keratan sulfate, and heparin/heparan sulfate have multiple functions including involvement in inflammation, immunity and connective tissue structure, and integrity. Heparan sulfate is a highly sulfated polysaccharide that is abundant in the periodontium including alveolar bone. Recent evidence supports the contention that heparan sulfate is an important player in modulating interactions between damage associated molecular patterns and inflammatory receptors expressed by various cell types. The structure of heparan sulfate is reported to dictate its function, thus, the utilization of a homogenous and structurally defined heparan sulfate polysaccharide for modulation of cell function offers therapeutic potential. Recently, a chemoenzymatic approach was developed to allow production of many structurally defined heparan sulfate carbohydrates. These oligosaccharides have been studied in various pathological inflammatory conditions to better understand their function and their potential application in promoting tissue homeostasis. We have observed that specific size and sulfation patterns can modulate inflammation and promote tissue maintenance including an anabolic effect in alveolar bone. Thus, new evidence provides a strong impetus to explore heparan sulfate as a potential novel therapeutic agent to treat periodontitis, support alveolar bone maintenance, and promote bone formation.

Topical Decorin Reduces Corneal Inflammation and Imparts Neuroprotection in a Mouse Model of Benzalkonium Chloride-induced Corneal Neuropathy

Purpose

We evaluated the neuroprotective and immunomodulatory effects of topical decorin in a murine model of benzalkonium chloride (BAK)-induced corneal neuropathy.

Methods

Topical BAK (0.1%) was administered daily to both eyes of female C57BL/6J mice (n = 14) for 7 days. One group of mice received topical decorin (1.07 mg/mL) eye drops to one eye and saline (0.9%) to the contralateral eye; the other group received saline eye drops to both eyes. All eye drops were given three times daily over the experimental period. A control group (n = 8) received daily topical saline only, instead of BAK. Optical coherence tomography imaging was performed before (at day 0) and after (day 7) treatment to evaluate the central corneal thickness. Whole-mount immunofluorescence staining was performed to evaluate the density of corneal intraepithelial nerves and immune cells.

Results

BAK-exposed eyes showed corneal epithelial thinning, infiltration of inflammatory macrophages and neutrophils, and a lower density of intraepithelial nerves. No change to the corneal stromal thickness or dendritic cell density was observed. After BAK exposure, decorin-treated eyes had a lower density of macrophages and less neutrophil infiltration and a higher nerve density than the saline-treated group. Contralateral eyes from the decorin-treated animals showed fewer macrophages and neutrophils relative to saline-treated animals. A negative correlation was found between corneal nerve density and macrophage or neutrophil density.

Conclusions

Topical decorin provides neuroprotective and anti-inflammatory effects in a chemical model of BAK-induced corneal neuropathy. The attenuation of corneal inflammation by decorin may contribute to decreasing corneal nerve degeneration induced by BAK.

The Role of Decorin in Autoimmune and Inflammatory Diseases

Decorin is an extracellular matrix protein that belongs to the family of small leucine-rich proteoglycans. As a matrix protein, the first discovered role of decorin is participating in collagen fibril formation. Many other functions of decorin in various biological processes have been subsequently identified. Decorin is involved in an extensive signaling network and can interact with other extracellular matrix components, growth factors, receptor tyrosine kinases, and various proteases. Decorin has been shown to be involved in wound repair, cell cycle, angiogenesis, tumor metastasis, and autophagy. Recent evidence indicates that it also plays a role in immune regulation and inflammatory diseases. This review summarizes the characteristics of decorin in immune and inflammatory diseases, including inflammatory bowel disease (IBD), Sjögren's syndrome (SS), chronic obstructive pulmonary disease (COPD), IgA nephropathy, rheumatoid arthritis (RA), spondyloarthritis (SpA), osteoarthritis, multiple sclerosis (MS), idiopathic inflammatory myopathies (IIM), and systemic sclerosis (SSc) and discusses the potential role in these disorders.

Decorin mediated biomimetic PCL-gelatin nano-framework to impede scarring

Scars occur as a result of fibrosis after tissue damage or surgery and reports suggest that excessive Transforming growth factor-β (TGF-β) activity during the process of wound healing leads to progressive fibrosis. Decorin is an extracellular matrix (ECM) protein which regulates collagen fibrillogenesis. However, targeted delivery and effective protein therapy remains a challenge owing to degradation byproteases. Hence, we aimed to deliver Decorin in a sustainable mode for the reduction of TGF-β levels and subsequent scar formation. Herein, we have fabricated PCL-Gelatin bio-mimetic scaffolds to optimize the bio-activity and provide localized delivery of recombinant Decorin. The degradation and drug release patterns reveals that this biomaterial is biodegradable and offers sustained release of the recombinant Decorin. Decorin loaded nanofiber displayed lower adhesion and proliferation rates in in-vitro conditions. Moreover, Decorin loaded scaffolds demonstrated morphological changes in cells, specifically targeting the myofibroblast. The expression of TGF-β was also scrutinized to understand the effect of Decorin loaded nanofibers. Besides, in the in-vitro fibrotic model, Decorin loaded nanofibers efficiently reduced the expression of ECM related proteins. Therefore, we report the sustained delivery of the recombinant Decorin from nanofiber dressing to potentially obstruct scar formation during the process of wound healing.

Asthma reduces glioma formation by T cell decorin-mediated inhibition of microglia

To elucidate the mechanisms underlying the reduced incidence of brain tumors in children with Neurofibromatosis type 1 (NF1) and asthma, we leverage Nf1 optic pathway glioma (Nf1^OPG) mice, human and mouse RNAseq data, and two different experimental asthma models. Following ovalbumin or house dust mite asthma induction at 4-6 weeks of age (WOA), Nf1^OPG mouse optic nerve volumes and proliferation are decreased at 12 and 24 WOA, indicating no tumor development. This inhibition is accompanied by reduced expression of the microglia-produced optic glioma mitogen, Ccl5. Human and murine T cell transcriptome analyses reveal that inhibition of microglia Ccl5 production results from increased T cell expression of decorin, which blocks Ccl4-mediated microglia Ccl5 expression through reduced microglia NFκB signaling. Decorin or NFκB inhibitor treatment of Nf1^OPG mice at 4-6 WOA inhibits tumor formation at 12 WOA, thus establishing a potential mechanistic etiology for the attenuated glioma incidence observed in children with asthma.

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.

Enhancement of interferon gamma stability as an anticancer therapeutic protein against hepatocellular carcinoma upon interaction with calycosin

The stability of IFN-γ as a therapeutic protein can play a key role on its anticancer effects. Herein, we explored the thermodynamic parameters and conformational stability of IFN-γ in the presence of calycosin, the main active compound of Radix astragali, by different biophysical and theoretical analysis. Afterwards, the improved anticancer effects of IFN-γ-calycosin interaction relative to IFN-γ alone were assessed on hepatocellular carcinoma (HepG2) cell line by MTT and caspase assays. ITC data indicated that upon interaction of calycosin with IFN-γ the binding and thermodynamic parameters were as follows: K_d = 1.9 μM, ΔG° = -32.45 kJ/mol, ΔH° = -11.91 kJ/mol, and TΔS° = 20.54 kJ/mol. ANS/synchronous fluorescence, CD and UV-Vis spectroscopy studies indicated that the interaction between calycosin and IFN-γ caused the folding of the IFN-γ backbone in to a more packed structure with enhanced α-helix content and higher melting temperature (Tm) value. The spectroscopic outcomes were then verified by molecular docking and molecular dynamic analysis. It was also shown that after incubation of the IFN-γ samples at 50 °C for 60 min in the presence of calycosin (5 μM), the IFN-γ-calycosin system showed a significant antiproliferative effects against hepatocellular carcinoma (HepG2) cells through caspase-9/3 activation and this anticancer effect was more pronounced than free IFN-γ. This data may provide useful information about the development of IFN-γ-based therapeutic platforms.

Communications via the Small Leucine-rich Proteoglycans: Molecular Specificity in Inflammation and Autoimmune Diseases

Inflammation is a highly regulated biological response of the immune system that is triggered by assaulting pathogens or endogenous alarmins. It is now well established that some soluble extracellular matrix constituents, such as small leucine-rich proteoglycans (SLRPs), can act as danger signals and trigger aseptic inflammation by interacting with innate immune receptors. SLRP inflammatory signaling cascade goes far beyond its canonical function. By choosing specific innate immune receptors, coreceptors, and adaptor molecules, SLRPs promote a switch between pro- and anti-inflammatory signaling, thereby determining disease resolution or chronification. Moreover, by orchestrating signaling through various receptors, SLRPs fine-tune inflammation and, despite their structural homology, regulate inflammatory processes in a molecule-specific manner. Hence, the overarching theme of this review is to highlight the molecular and functional specificity of biglycan-, decorin-, lumican-, and fibromodulin-mediated signaling in inflammatory and autoimmune diseases.

A novel chemotactic factor derived from the extracellular matrix protein decorin recruits mesenchymal stromal cells in vitro and in vivo

Soft tissue is composed of cells surrounded by an extracellular matrix that is made up of a diverse array of intricately organized proteins. These distinct components work in concert to maintain homeostasis and respond to tissue damage. During tissue repair, extracellular matrix proteins and their degradation products are known to influence physiological processes such as angiogenesis and inflammation. In this study we developed a discovery platform using a decellularized extracellular matrix biomaterial to identify new chemotrophic factors derived from the extracellular matrix. An in vitro culture of RAW.264 macrophage cells with the biomaterial ovine forestomach matrix led to the identification of a novel ~12 kDa chemotactic factor, termed ‘MayDay’, derived from the N-terminal 31–188 sequence of decorin. The recombinant MayDay protein was shown to be a chemotactic agent for mesenchymal stromal cells in vitro and in vivo. We hypothesize that the macrophage-induced cleavage of decorin, via MMP-12, leads to the release of the chemotactic molecule MayDay, that in turn recruits cells to the site of damaged tissue.

Unraveling the ECM-Immune Cell Crosstalk in Skin Diseases

The extracellular matrix (ECM) is a complex network of proteins and proteoglycans secreted by keratinocytes, fibroblasts and immune cells. The function of the skin ECM has expanded from being a scaffold that provides structural integrity, to a more dynamic entity that is constantly remodeled to maintain tissue homeostasis. The ECM functions as ligands for cell surface receptors such as integrins, dystroglycans, and toll-like receptors (TLRs) and regulate cellular signaling and immune cell dynamics. The ECM also acts as a sink for growth factors and cytokines, providing critical cues during epithelial morphogenesis. Dysregulation in the organization and deposition of ECMs lead to a plethora of pathophysiological conditions that are exacerbated by aberrant ECM-immune cell interactions. In this review, we focus on the interplay between ECM and immune cells in the context of skin diseases and also discuss state of the art therapies that target the key molecular players involved.

Melanoma Cell Adhesion and Migration Is Modulated by the Uronyl 2-O Sulfotransferase

Although the vast majority of melanomas are characterized by a high metastatic potential, if detected early, melanoma can have a good prognostic outcome. However, once metastasised, the prognosis is bleak. We showed previously that uronyl-2-O sulfotransferase (Ust) and 2-O sulfation of chondroitin/dermatan sulfate (CS/DS) are involved in cell migration. To demonstrate an impact of 2-O sulfation in metastasis we knocked-down Ust in mouse melanoma cells. This significantly reduced the amount of Ust protein and enzyme activity. Furthermore, in vitro cell motility and adhesion were significantly reduced correlating with the decrease of cellular Ust protein. Single cell migration of B16V^shUst(16) cells showed a decreased cell movement phenotype. The adhesion of B16V cells to fibronectin depended on α5β1 but not αvβ3 integrin. Inhibition of glycosaminoglycan sulfation or blocking fibroblast growth factor receptor (FgfR) reduced α5 integrin in B16V cell lines. Interestingly, FgfR1 expression and activation was reduced in Ust knock-down cells. In vivo, pulmonary metastasis of B16V^shUst cells was prevented due to a reduction of α5 integrin. As a proof of concept UST knock-down in human melanoma cells also showed a reduction in ITGa5 and adhesion. This is the first study showing that Ust, and consequently 2-O sulfation of the low affinity receptor for FgfR CS/DS, reduces Itga5 and leads to an impaired adhesion and migration of melanoma cells.

Proteoglycan neofunctions: regulation of inflammation and autophagy in cancer biology

Inflammation and autophagy have emerged as prominent issues in the context of proteoglycan signaling. In particular, two small, leucine-rich proteoglycans, biglycan and decorin, play pivotal roles in the regulation of these vital cellular pathways and, as such, are intrinsically involved in cancer initiation and progression. In this minireview, we will address novel functions of biglycan and decorin in inflammation and autophagy, and analyze new emerging signaling events triggered by these proteoglycans, which directly or indirectly modulate these processes. We will critically discuss the dual role of proteoglycan-driven inflammation and autophagy in tumor biology, and delineate the potential mechanisms through which soluble extracellular matrix constituents affect the microenvironment associated with inflammatory and neoplastic diseases.

T Cell Interstitial Migration: Motility Cues from the Inflamed Tissue for Micro- and Macro-Positioning

Effector T cells exit the inflamed vasculature into an environment shaped by tissue-specific structural configurations and inflammation-imposed extrinsic modifications. Once within interstitial spaces of non-lymphoid tissues, T cells migrate in an apparent random, non-directional, fashion. Efficient T cell scanning of the tissue environment is essential for successful location of infected target cells or encounter with antigen-presenting cells that activate the T cell's antimicrobial effector functions. The mechanisms of interstitial T cell motility and the environmental cues that may promote or hinder efficient tissue scanning are poorly understood. The extracellular matrix (ECM) appears to play an important scaffolding role in guidance of T cell migration and likely provides a platform for the display of chemotactic factors that may help to direct the positioning of T cells. Here, we discuss how intravital imaging has provided insight into the motility patterns and cellular machinery that facilitates T cell interstitial migration and the critical environmental factors that may optimize the efficiency of effector T cell scanning of the inflamed tissue. Specifically, we highlight the local micro-positioning cues T cells encounter as they migrate within inflamed tissues, from surrounding ECM and signaling molecules, as well as a requirement for appropriate long-range macro-positioning within distinct tissue compartments or at discrete foci of infection or tissue damage. The central nervous system (CNS) responds to injury and infection by extensively remodeling the ECM and with the de novo generation of a fibroblastic reticular network that likely influences T cell motility. We examine how inflammation-induced changes to the CNS landscape may regulate T cell tissue exploration and modulate function.

Decorin interacting network: A comprehensive analysis of decorin-binding partners and their versatile functions

Decorin, a prototype small leucine-rich proteoglycan, regulates a vast array of cellular processes including collagen fibrillogenesis, wound repair, angiostasis, tumor growth, and autophagy. This functional versatility arises from a wide array of decorin/protein interactions also including interactions with its single glycosaminoglycan side chain. The decorin-binding partners encompass numerous categories ranging from extracellular matrix molecules to cell surface receptors to growth factors and enzymes. Despite the diversity of the decorin interacting network, two main roles emerge as prominent themes in decorin function: maintenance of cellular structure and outside-in signaling, culminating in anti-tumorigenic effects. Here we present contemporary knowledge regarding the decorin interacting network and discuss in detail the biological relevance of these pleiotropic interactions, some of which could be targeted by therapeutic interventions.

Changes in dermal matrix in the absence of Rac1 in keratinocytes

Keratinocytes, in response to irritants, secrete pro-inflammatory mediators which recruit and activate immune and mesenchymal cells, including fibroblasts, to repair the skin. Fibroblasts respond by synthesising collagen and promoting the crosslinking extracellular matrix (ECM). We recently showed that the deletion of Rac1 in keratinocytes causes heightened inflammation due to aberrant crosstalk with immune cells. Indeed, the skin of these mice shows a higher inflammatory response to the induction of irritant contact dermatitis (ICD), and also even to treatment with a vehicle alone, compared with controls. As inflammation is intimately linked with fibrotic disease in the skin, this raised the question as to whether this deletion may also affect the deposition and arrangement of the dermal ECM. This study assessed the effects of Rac1 deletion in keratinocytes and of the heightened inflammatory status by induction of ICD on the tissue localisation and arrangements of dermal collagen. Qualitative analysis did not reveal evidence for the formation of pathologies in the dermis. However, quantitative analysis did reveal some perturbations in the dermal matrix, namely that only the combination of the lack of Rac1 and ICD affects the architectural organisation of the dermal collagen, and that a higher inflammatory state in the tissue (i.e. when Rac1 is deleted in the keratinocytes or ICD is induced in the skin, or a combination of both) influences the diameter of the collagen fibrils. It is proposed that this increase in the diameter of collagen fibrils due to inflammation may serve as pre-fibrotic marker enabling earlier determination of fibrosis and earlier treatment. This study has revealed previously unknown effects on the ECM due to the deletion of Rac1 in keratinocytes.

Decorin as a multivalent therapeutic agent against cancer

Decorin is a prototypical small leucine-rich proteoglycan that epitomizes the multifunctional nature of this critical gene family. Soluble decorin engages multiple receptor tyrosine kinases within the target-rich environment of the tumor stroma and tumor parenchyma. Upon receptor binding, decorin initiates signaling pathways within endothelial cells downstream of VEGFR2 that ultimately culminate in a Peg3/Beclin 1/LC3-dependent autophagic program. Concomitant with autophagic induction, decorin blunts capillary morphogenesis and endothelial cell migration, thereby significantly compromising tumor angiogenesis. In parallel within the tumor proper, decorin binds multiple RTKs with high affinity, including Met, for a multitude of oncosuppressive functions including growth inhibition, tumor cell mitophagy, and angiostasis. Decorin is also pro-inflammatory by modulating macrophage function and cytokine secretion. Decorin suppresses tumorigenic growth, angiogenesis, and prevents metastatic lesions in a variety of in vitro and in vivo tumor models. Therefore, decorin would be an ideal therapeutic candidate for combating solid malignancies.

Decoding the Matrix: Instructive Roles of Proteoglycan Receptors

The extracellular matrix is a dynamic repository harboring instructive cues that embody substantial regulatory dominance over many evolutionarily conserved intracellular activities, including proliferation, apoptosis, migration, motility, and autophagy. The matrix also coordinates and parses hierarchical information, such as angiogenesis, tumorigenesis, and immunological responses, typically providing the critical determinants driving each outcome. We provide the first comprehensive review focused on proteoglycan receptors, that is, signaling transmembrane proteins that use secreted proteoglycans as ligands, in addition to their natural ligands. The majority of these receptors belong to an exclusive subset of receptor tyrosine kinases and assorted cell surface receptors that specifically bind, transduce, and modulate fundamental cellular processes following interactions with proteoglycans. The class of small leucine-rich proteoglycans is the most studied so far and constitutes the best understood example of proteoglycan-receptor interactions. Decorin and biglycan evoke autophagy and immunological responses that deter, suppress, or exacerbate pathological conditions such as tumorigenesis, angiogenesis, and chronic inflammatory disease. Basement membrane-associated heparan sulfate proteoglycans (perlecan, agrin, and collagen XVIII) represent a unique cohort and provide proteolytically cleaved bioactive fragments for modulating cellular behavior. The receptors that bind the genuinely multifactorial and multivalent proteoglycans represent a nexus in understanding basic biological pathways and open new avenues for therapeutic and pharmacological intervention.

Proteoglycan form and function: A comprehensive nomenclature of proteoglycans

We provide a comprehensive classification of the proteoglycan gene families and respective protein cores. This updated nomenclature is based on three criteria: Cellular and subcellular location, overall gene/protein homology, and the utilization of specific protein modules within their respective protein cores. These three signatures were utilized to design four major classes of proteoglycans with distinct forms and functions: the intracellular, cell-surface, pericellular and extracellular proteoglycans. The proposed nomenclature encompasses forty-three distinct proteoglycan-encoding genes and many alternatively-spliced variants. The biological functions of these four proteoglycan families are critically assessed in development, cancer and angiogenesis, and in various acquired and genetic diseases where their expression is aberrant.

Pivotal role for decorin in angiogenesis

Angiogenesis, the formation of new blood vessels from preexisting vessels, is a highly complex process. It is regulated in a finely-tuned manner by numerous molecules including not only soluble growth factors such as vascular endothelial growth factor and several other growth factors, but also a diverse set of insoluble molecules, particularly collagenous and non-collagenous matrix constituents. In this review we have focused on the role and potential mechanisms of a multifunctional small leucine-rich proteoglycan decorin in angiogenesis. Depending on the cellular and molecular microenvironment where angiogenesis occurs, decorin can exhibit either a proangiogenic or an antiangiogenic activity. Nevertheless, in tumorigenesis-associated angiogenesis and in various inflammatory processes, particularly foreign body reactions and scarring, decorin exhibits an antiangiogenic activity, thus providing a potential basis for the development of decorin-based therapies in these pathological situations.

Plasticity of fibroblasts demonstrated by tissue-specific and function-related proteome profiling

Background

Fibroblasts are mesenchymal stromal cells which occur in all tissue types. While their main function is related to ECM production and physical support, they are also important players in wound healing, and have further been recognized to be able to modulate inflammatory processes and support tumor growth. Fibroblasts can display distinct phenotypes, depending on their tissue origin, as well as on their functional state.

Results

In order to contribute to the proteomic characterization of fibroblasts, we have isolated primary human fibroblasts from human skin, lung and bone marrow and generated proteome profiles of these cells by LC-MS/MS. Comparative proteome profiling revealed characteristic differences therein, which seemed to be related to the cell’s tissue origin. Furthermore, the cells were treated in vitro with the pro-inflammatory cytokine IL-1beta. While all fibroblasts induced the secretion of Interleukins IL-6 and IL-8 and the chemokine GRO-alpha, other inflammation-related proteins were up-regulated in an apparently tissue-dependent manner. Investigating fibroblasts from tumorous tissues of skin, lung and bone marrow with respect to such inflammation-related proteins revealed hardly any conformity but rather individual and tumor type-related variations. However, apparent up-regulation of IGF-II, PAI-1 and PLOD2 was observed in melanoma-, lung adenocarcinoma- and multiple myeloma-associated fibroblasts, as well as in hepatocellular carcinoma-associated fibroblasts.

Conclusions

Inflammation-related proteome alterations of primary human fibroblasts were determined by the analysis of IL-1beta treated cells. Tumor-associated fibroblasts from different tissue types hardly showed signs of acute inflammation but displayed characteristic functional aberrations potentially related to chronic inflammation. The present data suggest that the state of the tumor microenvironment is relevant for tumor progression and targeted treatment of tumor-associated fibroblasts may support anti-cancer strategies.

Electronic supplementary material

The online version of this article (doi:10.1186/1559-0275-11-41) contains supplementary material, which is available to authorized users.

Extracellular matrix regulation of inflammation in the healthy and injured spinal cord

Throughout the body, the extracellular matrix (ECM) provides structure and organization to tissues and also helps regulate cell migration and intercellular communication. In the injured spinal cord (or brain), changes in the composition and structure of the ECM undoubtedly contribute to regeneration failure. Less appreciated is how the native and injured ECM influences intraspinal inflammation and, conversely, how neuroinflammation affects the synthesis and deposition of ECM after CNS injury. In all tissues, inflammation can be initiated and propagated by ECM disruption. Molecules of ECM newly liberated by injury or inflammation include hyaluronan fragments, tenascins, and sulfated proteoglycans. These act as "damage-associated molecular patterns" or "alarmins", i.e., endogenous proteins that trigger and subsequently amplify inflammation. Activated inflammatory cells, in turn, further damage the ECM by releasing degradative enzymes including matrix metalloproteinases (MMPs). After spinal cord injury (SCI), destabilization or alteration of the structural and chemical compositions of the ECM affects migration, communication, and survival of all cells - neural and non-neural - that are critical for spinal cord repair. By stabilizing ECM structure or modifying their ability to trigger the degradative effects of inflammation, it may be possible to create an environment that is more conducive to tissue repair and axon plasticity after SCI.

A decorin-deficient matrix affects skin chondroitin/dermatan sulfate levels and keratinocyte function

Decorin is a small leucine-rich proteoglycan harboring a single glycosaminoglycan chain, which, in skin, is mainly composed of dermatan sulfate (DS). Mutant mice with targeted disruption of the decorin gene (Dcn(-/-)) exhibit an abnormal collagen architecture in the dermis and reduced tensile strength, collectively leading to a skin fragility phenotype. Notably, Ehlers-Danlos patients with mutations in enzymes involved in the biosynthesis of DS display a similar phenotype, and recent studies indicate that DS is involved in growth factor binding and signaling. To determine the impact of the loss of DS-decorin in the dermis, we analyzed the glycosaminoglycan content of Dcn(-/-) and wild-type mouse skin. The total amount of chondroitin/dermatan sulfate (CS/DS) was increased in the Dcn(-/-) skin, but was overall less sulfated with a significant reduction in bisulfated ΔDiS2,X (X=4 or 6) disaccharide units, due to the reduced expression of uronyl 2-O sulfotransferase (Ust). With increasing age, sulfation declined; however, Dcn(-/-) CS/DS was constantly undersulfated vis-à-vis wild-type. Functionally, we found altered fibroblast growth factor (Fgf)-7 and -2 binding due to changes in the micro-heterogeneity of skin Dcn(-/-) CS/DS. To better delineate the role of decorin, we used a 3D Dcn(-/-) fibroblast cell culture model. We found that the CS/DS extracts of wild-type and Dcn(-/-) fibroblasts were similar to the skin sugars, and this correlated with the lack of uronyl 2-O sulfotransferase in the Dcn(-/-) fibroblasts. Moreover, Ffg7 binding to total CS/DS was attenuated in the Dcn(-/-) samples. Surprisingly, wild-type CS/DS significantly reduced the binding of Fgf7 to keratinocytes in a concentration dependent manner unlike the Dcn(-/-) CS/DS that only affected the binding at higher concentrations. Although binding to cell-surfaces was quite similar at higher concentrations, keratinocyte proliferation was differentially affected. Higher concentration of Dcn(-/-) CS/DS induced proliferation in contrast to wild-type CS/DS. 3D co-cultures of fibroblasts and keratinocytes showed that, unlike Dcn(-/-) CS/DS, wild-type CS/DS promoted differentiation of keratinocytes. Collectively, our results provide novel mechanistic explanations for the reported defects in wound healing in Dcn(-/-) mice and possibly Ehlers-Danlos patients. Moreover, the lack of decorin-derived DS and an altered CS/DS composition differentially influence keratinocyte behavior.