Reprint of: A rapid increase in macrophage-derived versican and hyaluronan in infectious lung disease

Roles of extracellular matrix in lung diseases

Extracellular matrix (ECM) is a non-cellular constituent found in all tissues and organs. Although ECM was previously recognized as a mere "molecular glue" that supports the tissue structure of organs such as the lungs, it has recently been reported that ECM has important biological activities for tissue morphogenesis, inflammation, wound healing, and tumor progression. Proteoglycans are the main constituent of ECM, with growing evidence that proteoglycans and their associated glycosaminoglycans play important roles in the pathogenesis of several diseases. However, their roles in the lungs are incompletely understood. Leukocyte migration into the lung is one of the main aspects involved in the pathogenesis of several lung diseases. Glycosaminoglycans bind to chemokines and their interaction fine-tunes leukocyte migration into the affected organs. This review focuses on the role chemokine and glycosaminoglycan interactions in neutrophil migration into the lung. Furthermore, this review presents the role of proteoglycans such as syndecan, versican, and hyaluronan in inflammatory and fibrotic lung diseases.

Serum versican as a potential biomarker in patients with uterine fibroids: A study from Eastern India

Objective

Versican is a chondroitin sulphate proteoglycan with raised expression at site of inflammation, and uterine fibroids are associated with local inflammation. Hence, this study aimed to estimate serum Versican levels in pre-menopausal women with uterine fibroids to evaluate its diagnostic efficiency.

Materials and Methods

This case-control study included forty uterine fibroid cases and 40 healthy controls. Cases clinically evaluated with USG findings, that is number, location of fibroid and volume calculated by prolate ellipse formula a × b × c × 0.523 (a - height, b - width, c - depth). Biochemical investigations, that is serum Versican levels, were estimated by ELISA with total cholesterol, HDLc and LDLc. Triglycerides by fully automated chemistry analysers. Serum biochemical parameters were compared and correlated with volume of fibroid. Area under receiver operating characteristic curve was calculated along with cut-off value to determine diagnostic potential of Versican, differentiating women with fibroids.

Results

In the present study, patients with fibroids had decreased levels of serum Versican (79.43 ± 18.60) as compared to healthy controls (101.81 ± 28.24, P < 0.001). There was a statistically significant negative correlation (r = - 0. 307, P = 0.04) between serum Versican level and volume of fibroid. Area under ROC was 0.726 (95% CI: 0.616-0.836; P = 0.001). The best cut-off value for serum Versican level was 96.90 ng/ml with 90% sensitivity and 48% specificity.

Conclusion

Serum Versican levels were found significantly lower in women with fibroid with a negative correlation with volume of fibroid uterus. Furthermore, extensive study would help in substantiating diagnostic potential of serum Versican in fibroid uterus patients.

Knockdown of versican 1 in lung fibroblasts aggravates Lipopolysaccharide-induced acute inflammation through up-regulation of the SP1-Toll-like Receptor 2-NF-κB Axis: a potential barrier to promising Versican-targeted therapy

OBJECTIVE

Versican participates in various pathological processes like inflammation and fibrosis and is a potential therapeutic target for inflammatory diseases. Versican 1 (V1) has increased expression in inflammatory diseases, but its role is unclear. We explored the effects of V1 on acute lung inflammation to determine whether targeting V1 had therapeutic potential.

METHODS

Human fetal lung fibroblast (HFL1) was transfected with or without V1-inhibiting lentivirus and treated with LPS. The expression levels of inflammatory cytokines, V1, cellular signaling pathway and Toll-like receptors (TLRs) were detected by qPCR, ELISA and western blot. The migration and adhesion of neutrophils and monocytes to HFL1s were performed. The activity of transcriptional factors was determined by dual-luciferase reporter assay.

RESULTS

Inflammatory factors increased dramatically and continuously with V1 knockdown and LPS stimulation (P < 0.01), orchestrating migration of inflammatory cells and an enhanced inflammatory reaction. V1-knockdown increased TLR2 (P < 0.01) and activated the NF-κB pathway, which was partially reversed with a TLR2 neutralizing antibody and an NF-κB inhibitor. Explosion of LPS-induced inflammation was induced by knockdown of V1 via the SP1-TLR2-NF-κB axis.

CONCLUSION

Increased expression of V1 might be protective in acute inflammation, and an infection-induced cytokine storm might be a severe complication of V1-targeted interventions.

PSGL-1 Immune Checkpoint Inhibition for CD4+ T Cell Cancer Immunotherapy

Immune checkpoint inhibition targeting T cells has shown tremendous promise in the treatment of many cancer types and are now standard therapies for patients. While standard therapies have focused on PD-1 and CTLA-4 blockade, additional immune checkpoints have shown promise in promoting anti-tumor immunity. PSGL-1, primarily known for its role in cellular migration, has also been shown to function as a negative regulator of CD4+ T cells in numerous disease settings including cancer. PSGL-1 is highly expressed on T cells and can engage numerous ligands that impact signaling pathways, which may modulate CD4+ T cell differentiation and function. PSGL-1 engagement in the tumor microenvironment may promote CD4+ T cell exhaustion pathways that favor tumor growth. Here we highlight that blocking the PSGL-1 pathway on CD4+ T cells may represent a new cancer therapy approach to eradicate tumors.

Versican and Versican-matrikines in Cancer Progression, Inflammation, and Immunity

Versican is an extracellular matrix proteoglycan with key roles in multiple facets of cancer development, ranging from proliferative signaling, evasion of growth-suppressor pathways, regulation of cell death, promotion of neoangiogenesis, and tissue invasion and metastasis. Multiple lines of evidence implicate versican and its bioactive proteolytic fragments (matrikines) in the regulation of cancer inflammation and antitumor immune responses. The understanding of the dynamics of versican deposition/accumulation and its proteolytic turnover holds potential for the development of novel immune biomarkers as well as approaches to reset the immune thermostat of tumors, thus promoting efficacy of modern immunotherapies. This article summarizes work from several laboratories, including ours, on the role of this central matrix proteoglycan in tumor progression as well as tumor-immune cell cross-talk.

Versican in the Tumor Microenvironment

Versican is an extracellular matrix proteoglycan with nonredundant roles in diverse biological and cellular processes, ranging from embryonic development to adult inflammation and cancer. Versican is essential for cardiovascular morphogenesis, neural crest migration, and skeletal development during embryogenesis. In the adult, versican acts as an inflammation "amplifier" and regulator of immune cell activation and cytokine production. Increased versican expression has been observed in a wide range of malignant tumors and has been associated with poor patient outcomes. The main sources of versican production in the tumor microenvironment include accessory cells (myeloid cells and stromal components) and, in some contexts, the tumor cells themselves. Versican has been implicated in several classical hallmarks of cancer such as proliferative signaling, evasion of growth suppressor signaling, resistance to cell death, angiogenesis, and tissue invasion and metastasis. More recently, versican has been implicated in escape from tumor immune surveillance, e.g., through dendritic cell dysfunction. Versican's multiple contributions to benign and malignant biological processes are further diversified through the generation of versican-derived bioactive proteolytic fragments (matrikines), with versikine being the most studied to date. Versican and versican-derived matrikines hold promise as targets in the management of inflammatory and malignant conditions as well as in the development of novel predictive and prognostic biomarkers.

A complex interplay between the extracellular matrix and the innate immune response to microbial pathogens

The role of the host extracellular matrix (ECM) in infection tends to be neglected. However, the complex interactions between invading pathogens, host tissues and immune cells occur in the context of the ECM. On the pathogen side, a variety of surface and secreted molecules, including microbial surface components recognizing adhesive matrix molecules and tissue-degrading enzymes, are employed that interact with different ECM proteins to effectively establish an infection at specific sites. Microbial pathogens can also hijack or misuse host proteolytic systems to modify the ECM, evade immune responses or process biologically active molecules such as cell surface receptors and cytokines that direct cell behaviour and immune defence. On the host side, the ECM composition and three-dimensional ultrastructure undergo significant modifications, which have a profound impact on the specific signals that the ECM conveys to immune cells at the forefront of infection. Unexpectedly, activated immune cells participate in the remodelling of the local ECM by synthesizing ECM glycoproteins, proteoglycans and collagen molecules. The close interplay between the ECM and the innate immune response to microbial pathogens ultimately affects the outcome of infection. This review explores and discusses recent data that implicate an active role for the ECM in the immune response to infection, encompassing antimicrobial activities, microbial recognition, macrophage activation, phagocytosis, leucocyte population balance, and transcriptional and post-transcriptional regulation of inflammatory networks, and may foster novel antimicrobial approaches.

The CD44-HA axis and inflammation in atherosclerosis: A temporal perspective

Cardiovascular disease (CVD) due to atherosclerosis is a disease of chronic inflammation at both the systemic and the tissue level. CD44 has previously been implicated in atherosclerosis in both humans and mice. This multi-faceted receptor plays a critical part in the inflammatory response during the onset of CVD, though little is known of CD44's role during the latter stages of the disease. This review focuses on the role of CD44-dependent HA-dependent effects on inflammatory cells in several key processes, from disease initiation throughout the progression of atherosclerosis. Understanding how CD44 and HA regulate inflammation in atherogenesis is key in determining the utility of the CD44-HA axis as a therapeutic target to halt disease and potentially promote disease regression.

A Serological Biomarker of Versican Degradation is Associated with Mortality Following Acute Exacerbations of Idiopathic Interstitial Pneumonia

Background

Idiopathic interstitial pneumonia (IIP) is characterized by an increased rate of extracellular matrix (ECM) remodeling resulting in fibrosis. Acute exacerbations of IIP represent periods of increased disease activity, thus we hypothesized that ECM remodeling was altered during acute exacerbations and investigated this by serological neo-epitope biomarkers.

Methods

Patients who were sequentially admitted to the hospital with acute exacerbations of IIP were retrospectively analyzed for ECM remodeling at time of exacerbation (AE-IIP) and at clinical stability (S-IIP). Biomarkers released by matrix metalloproteinase-mediated degradation of collagen type I (C1M), III (C3M), IV (C4M), and VI (C6M), elastin (ELM7), versican (VCANM), biglycan (BGM), and C-reactive protein (CRPM) were assessed in serum by competitive ELISAs utilizing neo-epitope specific monoclonal antibodies.

Results

Sixty-eight patients at AE-IIP and 29 at S-IIP were included in this retrospective analysis. Of these, 28 and 11 patients, respectively, had idiopathic pulmonary fibrosis. At AE-IIP, serum levels of C4M (p = 0.002) and C6M (p = 0.024) were increased as compared with S-IIP, while ELM7 (p = 0.024) and VCANM (p < 0.0001) were decreased. Lower VCANM levels at AE-IIP were associated with increased risk of mortality (HR 0.64 [95% CI 0.43–0.94], p = 0.022).

Conclusions

The ECM remodeling profile was significantly altered during acute exacerbations of IIP, and a biomarker of versican degradation was related to mortality outcome. These results indicate that biomarkers of ECM remodeling may be useful in the non-invasive evaluation of acute exacerbations of IIP. Especially versican degradation, as measured serologically by VCANM, may have prognostic potential and help guide treatment for acute exacerbations.

The Versican G1 Fragment and Serum-Derived Hyaluronan-Associated Proteins Interact and Form a Complex in Granulation Tissue of Pressure Ulcers

The hyaluronan (HA)-rich extracellular matrix plays dynamic roles during tissue remodeling. Versican and serum-derived HA-associated protein (SHAP), corresponding to the heavy chains of inter-α-trypsin inhibitor, are major HA-binding molecules in remodeling processes, such as wound healing. Versican G1-domain fragment (VG1F) is generated by proteolysis and is present in either remodeling tissues or the mature dermis. However, the macrocomplex formation of VG1F has not been clarified. Therefore, we examined the VG1F-containing macrocomplex in pressure ulcers characterized by chronic refractory wounds. VG1F colocalized with SHAP-HA in specific regions of the granulation tissue but not with fibrillin-1. A unique VG1F-SHAP-HA complex was isolated from granulation tissues using gel filtration chromatography and subsequent cesium chloride-gradient ultracentrifugation under dissociating conditions. Consistent with this molecular composition, recombinant versican G1, but not versican G3, interacted with the two heavy chains of inter-α-trypsin inhibitor. The addition of recombinant VG1 in fibroblast cultures enhanced VG1F-SHAP-HA complex deposition in the pericellular extracellular matrix. Comparison with other VG1F-containing macrocomplexes, including dermal VG1F aggregates, versican-bound microfibrils, and intact versican, highlighted the tissue-specific organization of HA-rich extracellular matrix formation containing versican and SHAP. The VG1F-SHAP-HA complex was specifically detected in the edematous granulation tissues of human pressure ulcers and in inflamed stages in a mouse model of moist would healing, suggesting that the complex provides an HA-rich matrix suitable for inflammatory reactions.

Human mesenchymal stem cells secrete hyaluronan-coated extracellular vesicles

Extracellular vesicles (EVs) secreted by stem cells are potential factors mediating tissue regeneration. They travel from bone marrow stem cells into damaged tissues, suggesting that they can repair tissue injuries without directly replacing parenchymal cells. We have discovered that hyaluronan (HA) synthesis is associated with the shedding of HA-coated EVs. The aim of this study was to test whether bone marrow-derived hMSCs secrete HA-coated EVs. The EVs secreted by MSCs were isolated by differential centrifugation and characterized by nanoparticle tracking analysis. Their morphology and budding mechanisms were inspected by confocal microscopy and correlative light and electron microscopy. Hyaluronan synthesis of hMSCs was induced by lipopolysaccharide and inhibited by RNA interference and 4-methylumbelliferone. It was found that the MSCs have extremely long apical and lateral HA-coated filopodia, typical for cells with an active HA secretion. Additionally, they secreted HA-coated EVs carrying mRNAs for CD44 and all HAS isoforms. The results show that stem cells have a strong intrinsic potential for HA synthesis and EV secretion, and the amount of HA carried on EVs reflects the HA content of the original cells. These results show that the secretion of HA-coated EVs by hMSCs is a general process, that may contribute to many of the mechanisms of HA-mediated tissue regeneration. Additionally, an HA coat on EVs may regulate their interactions with target cells and participate in extracellular matrix remodeling.

Methods for Implant Acceptance and Wound Healing: Material Selection and Implant Location Modulate Macrophage and Fibroblast Phenotypes

This review focuses on materials and methods used to induce phenotypic changes in macrophages and fibroblasts. Herein, we give a brief overview on how changes in macrophages and fibroblasts phenotypes are critical biomarkers for identification of implant acceptance, wound healing effectiveness, and are also essential for evaluating the regenerative capabilities of some hybrid strategies that involve the combination of natural and synthetic materials. The different types of cells present during the host response have been extensively studied for evaluating the reaction to different materials and there are varied material approaches towards fabrication of biocompatible substrates. We discuss how natural and synthetic materials have been used to engineer desirable outcomes in lung, heart, liver, skin, and musculoskeletal implants, and how certain properties such as rigidity, surface shape, and porosity play key roles in the progression of the host response. Several fabrication strategies are discussed to control the phenotype of infiltrating macrophages and fibroblasts: decellularization of scaffolds, surface coatings, implant shape, and pore size apart from biochemical signaling pathways that can inhibit or accelerate unfavorable host responses. It is essential to factor all the different design principles and material fabrication criteria for evaluating the choice of implant materials or regenerative therapeutic strategies.

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.

Mice deficient in N-acetylgalactosamine 4-sulfate 6-O-sulfotransferase exhibit enhanced liver fibrosis and delayed recovery from fibrosis in carbon tetrachloride-treated mice

Background

Chondroitin/dermatan sulfate (CS/DS) rich in N-acetylgalactosamine 4,6-bissulfate (GalNAc(4,6SO₄)) residues is present as decorin and/or biglycan in mouse liver, and GalNAc(4,6SO₄) residues disappeared completely in N-acetylgalactosamine 4-sulfate 6-O-sulfotransferase (GalNAc4S-6ST) knockout (KO) mice. The aim of this study was to investigate whether CS/DS rich in GalNAc(4,6SO₄) residues participate in the progression or resolution of liver fibrosis.

Methods

Wild type (WT) and GalNAc4S-6ST KO mice were treated with CCl₄ for 5 weeks. After discontinuation of CCl₄ administration, histochemical and biochemical changes and expression of genes related to matrix components were compared between WT and GalNAc4S-6ST KO mice.

Results and conclusion

On 2 days after cessation of CCl₄ administration, higher fibrosis was observed in KO mice than in WT mice by Sirius Red staining. Serum alanine aminotransferase activity was higher in KO mice than in WT mice. Hydroxyproline contents and Sirius Red staining showed that repair of liver fibrosis in the recovery stages appeared to be delayed in KO mice. Expression of mRNA of matrix metalloproteinase (MMP)-2, MMP-13 and versican peaked at 2 days after cessation of CCl₄ administration and was higher in KO mice than in WT mice. Expression of MMP-9 in the recovery stage was lower in KO mice than in WT mice. Our findings demonstrate that defect in GalNAc4S-6ST, which resulted in disappearance of CS/DS containing GalNAc(4,6SO₄), appear to contribute to progression of liver fibrosis, delayed recovery from fibrosis, and various changes in the expression of proteoglycans and MMPs in carbon tetrachloride–treated mice.

Knockdown of versican V1 induces a severe inflammatory response in LPS-induced acute lung injury via the TLR2-NF-κB signaling pathway in C57BL/6J mice

The versican family is important in the modulation of inflammation, however, the role of versican V1 (V1) in lipo-polysaccharide (LPS)-induced acute lung injury (ALI) and the underlying mechanisms remain to be elucidated. To investigate this, the present study performed experiments in male C57BL/6J mice, which were randomly divided into a normal control group (control; n=6), an LPS-stimulated ALI group (LPS; n=6), a scramble small interfering (si)RNA group (scramble; n=6), a V1-siRNA group (V1-siRNA; n=6), a scramble siRNA and LPS-stimulated group (scramble+LPS; n=6) and a V1-siRNA and LPS-stimulated group (V1-siRNA+LPS; n=6). On day 1, the mice were anesthetized, and 5 nmol scramble siRNA or V1-siRNA were administered intratracheally. On day 3, LPS (1 mg/kg) or phosphate-buffered saline (50 µl per mouse) were injected intratracheally. All the mice were anesthetized and sacrificed on day 4, and samples were collected and analyzed. The mRNA and protein expression levels were examined using reverse transcription-quantitative polymerase chain reaction analysis, immunohistochemical staining and western blot analysis. ALI was evaluated based on lung injury scores, cell counts and total protein concentrations in the bronchoalveolar lavage fluid (BALF). Inflammatory mediators were detected using an enzyme-linked immunosorbend assay. V1 was increased by LPS in the mouse ALI model, whereas specific V1 knockdown induced higher lung injury scores, and higher total cell counts and protein concentrations in the BALF. Tumor necrosis factor-α (TNF)-α was upregulated, and interleukin-6 exhibited an increasing trend. The expression of toll-like receptor 2 (TLR2), but not TLR4, increased, and the nuclear factor (NF)-κB pathway subunit, P65, was phosphorylated. Taken together, the expression of V1 was upregulated by LPS, and V1 inhibition resulted in the aggravation of LPS-induced ALI via the activation of TLR2-NF-κB and release of TNF-α.

Kinetics of versican-expressing macrophages in bone marrow after cord blood stem cell transplantation for treatment of acute myelogenous leukaemia

Aims

To determine versican-producing cells in normocellular bone marrow and to evaluate chronological alteration in the number of versican-producing macrophages in bone marrow of patients with acute myelogenous leukaemia (AML) after cord blood stem cell transplantation (CBSCT) to gain insight in the significance of versican in recovery of haematopoiesis.

Methods

We enrolled seven age-matched unrelated patients with normocellular bone marrow for determining versican-producing cells in bone marrow, CBSCT-treated patients with AML, 18 with fine and other four with poor engraftment, for determining chronological alteration of versican-expressing and CD68-expressing cells in transplanted bone marrow in reference to the total cells. Clot samples of patients with AML were collected from the +16 to +55 day after transplantation and separated into four groups. We included an AML case whose specimen was obtained on the +9 day. Cells positive in immunohistochemistry using antibodies to versican and CD68 were counted to obtain the mean±SD in a unit area of the bone marrow, plotted chronologically and compared with the numbers from the age-matched normocellular group.

Results

We determined by a double immunohistochemistry that the versican-expressing cells in bone marrow are macrophages. The time-course curve demonstrated an inverse relationship between the versican-positive macrophages and the total cells in the transplanted bone marrow for over 55 days. In bone marrow of poor engraftment cases, versican-positive macrophages appeared to be decreased in comparison with age-matched and sampling day-matched patients.

Conclusions

These results suggest that versican and/or versican-expressing macrophages positively contribute to bone marrow regeneration of patients with AML after CBSCT.

The Rise and Fall of Hyaluronan in Respiratory Diseases

In normal airways, hyaluronan (HA) matrices are primarily located within the airway submucosa, pulmonary vasculature walls, and, to a lesser extent, the alveoli. Following pulmonary injury, elevated levels of HA matrices accumulate in these regions, and in respiratory secretions, correlating with the extent of injury. Animal models have provided important insight into the role of HA in the onset of pulmonary injury and repair, generally indicating that the induction of HA synthesis is an early event typically preceding fibrosis. The HA that accumulates in inflamed airways is of a high molecular weight (>1600 kDa) but can be broken down into smaller fragments (<150 kDa) by inflammatory and disease-related mechanisms that have profound effects on HA pathobiology. During inflammation in the airways, HA is often covalently modified with heavy chains from inter-alpha-inhibitor via the enzyme tumor-necrosis-factor-stimulated-gene-6 (TSG-6) and this modification promotes the interaction of leukocytes with HA matrices at sites of inflammation. The clearance of HA and its return to normal levels is essential for the proper resolution of inflammation. These data portray HA matrices as an important component of normal airway physiology and illustrate its integral roles during tissue injury and repair among a variety of respiratory diseases.

Regulated Hyaluronan Synthesis by Vascular Cells

Cellular microenvironment plays a critical role in several pathologies including atherosclerosis. Hyaluronan (HA) content often reflects the progression of this disease in promoting vessel thickening and cell migration. HA synthesis is regulated by several factors, including the phosphorylation of HA synthase 2 (HAS2) and other covalent modifications including ubiquitination and O-GlcNAcylation. Substrate availability is important in HA synthesis control. Specific drugs reducing the UDP precursors are able to reduce HA synthesis whereas the hexosamine biosynthetic pathway (HBP) increases the concentration of HA precursor UDP-N-acetylglucosamine (UDP-GlcNAc) leading to an increase of HA synthesis. The flux through the HBP in the regulation of HA biosynthesis in human aortic vascular smooth muscle cells (VSMCs) was reported as a critical aspect. In fact, inhibiting O-GlcNAcylation reduced HA production whereas increased O-GlcNAcylation augmented HA secretion. Additionally, O-GlcNAcylation regulates HAS2 gene expression resulting in accumulation of its mRNA after induction of O-GlcNAcylation with glucosamine treatments. The oxidized LDLs, the most common molecules related to atherosclerosis outcome and progression, are also able to induce a strong HA synthesis when they are in contact with vascular cells. In this review, we present recent described mechanisms involved in HA synthesis regulation and their role in atherosclerosis outcome and development.

Could Ex Vivo Lung Perfusion Be a Platform to Decrease the Incidence of Chronic Lung Allograft Dysfunction?

The number of patients requiring lung transplantation is increasing, with a significant unmet demand for grafts. Ex vivo lung perfusion has been developed to increase graft recruitment. The major complications of lung transplantation include chronic allograft dysfunction (CLAD) whose cumulative incidence ranges from 43-80% within the first 5 years of transplantation. Many risk factors are listed for development of CLAD and almost all of those risk factors would involve activation of Toll-like receptors. This paper represents the author's overview regarding the development of CLAD as a complication of lung transplantation and the possible protective potential of ex vivo lung perfusion in this regard.

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.

Hyaluronan synthase 1: a mysterious enzyme with unexpected functions

Hyaluronan synthase 1 (HAS1) is one of three isoenzymes responsible for cellular hyaluronan synthesis. Interest in HAS1 has been limited because its role in hyaluronan production seems to be insignificant compared to the two other isoenzymes, HAS2 and HAS3, which have higher enzymatic activity. Furthermore, in most cell types studied so far, the expression of its gene is low and the enzyme requires high concentrations of sugar precursors for hyaluronan synthesis, even when overexpressed in cell cultures. Both expression and activity of HAS1 are induced by pro-inflammatory factors like interleukins and cytokines, suggesting its involvement in inflammatory conditions. Has1 is upregulated in states associated with inflammation, like atherosclerosis, osteoarthritis, and infectious lung disease. In addition, both full length and splice variants of HAS1 are expressed in malignancies like bladder and prostate cancers, multiple myeloma, and malignant mesothelioma. Interestingly, immunostainings of tissue sections have demonstrated the role of HAS1 as a poor predictor in breast cancer, and is correlated with high relapse rate and short overall survival. Utilization of fluorescently tagged proteins has revealed the intracellular distribution pattern of HAS1, distinct from other isoenzymes. In all cell types studied so far, a high proportion of HAS1 is accumulated intracellularly, with a faint signal detected on the plasma membrane and its protrusions. Furthermore, the pericellular hyaluronan coat produced by HAS1 is usually thin without induction by inflammatory agents or glycemic stress and depends on CD44–HA interactions. These specific interactions regulate the organization of hyaluronan into a leukocyte recruiting matrix during inflammatory responses. Despite the apparently minor enzymatic activity of HAS1 under normal conditions, it may be an important factor under conditions associated with glycemic stress like metabolic syndrome, inflammation, and cancer.

Deletion of ADORA2B from myeloid cells dampens lung fibrosis and pulmonary hypertension

Idiopathic pulmonary fibrosis (IPF) is a lethal, fibroproliferative disease. Pulmonary hypertension (PH) can develop secondary to IPF and increase mortality. Alternatively, activated macrophages (AAMs) contribute to the pathogenesis of both IPF and PH. Here we hypothesized that adenosine signaling through the ADORA2B on AAMs impacts the progression of these disorders and that conditional deletion of ADORA2B on myeloid cells would have a beneficial effect in a model of these diseases. Conditional knockout mice lacking ADORA2B on myeloid cells (Adora2B(f/f)-LysM(Cre)) were exposed to the fibrotic agent bleomycin (BLM; 0.035 U/g body weight, i.p.). At 14, 17, 21, 25, or 33 d after exposure, SpO2, bronchoalveolar lavage fluid (BALF), and histologic analyses were performed. On day 33, lung function and cardiovascular analyses were determined. Markers for AAM and mediators of fibrosis and PH were assessed. Adora2B(f/f)-LysM(Cre) mice presented with attenuated fibrosis, improved lung function, and no evidence of PH compared with control mice exposed to BLM. These findings were accompanied by reduced expression of CD206 and arginase-1, markers for AAMs. A 10-fold reduction in IL-6 and a 5-fold decrease in hyaluronan, both linked to lung fibrosis and PH, were also observed. These data suggest that activation of the ADORA2B on macrophages plays an active role in the pathogenesis of lung fibrosis and PH.