Decorin is produced by capillary endothelial cells in inflammation-associated angiogenesis

Oral Pyogenic Granuloma: A Narrative Review

Pyogenic granuloma (PG) is a benign vascular lesion found predominantly in the oral cavity. Characterized by rapid growth and propensity to bleed, PG presents diagnostic challenges due to its similarity and alarming proliferation. This narrative review synthesizes current knowledge on the epidemiology, etiopathogenesis, clinical manifestations, and management of oral PG, with emphasis on recent advances in diagnostic and therapeutic approaches. The epidemiology of the injury is meticulously analyzed, revealing a higher incidence in women and a wide range of ages of onset. It delves into the etiopathogenesis, highlighting the uncertainty surrounding the exact causal factors, although historical attributions suggest an infectious origin. It exhaustively analyzes the clinical and histopathological aspects of oral PG, offering information on its various presentations and the importance of an accurate diagnosis to guide effective treatment. It details treatment strategies, emphasizing the personalized approach based on individual patient characteristics. This comprehensive review consolidates current knowledge on oral PG, highlighting the need for further research to clarify its pathogenesis and optimize treatment protocols.

Mapping cardiac remodeling in chronic kidney disease

Patients with advanced chronic kidney disease (CKD) mostly die from sudden cardiac death and recurrent heart failure. The mechanisms of cardiac remodeling are largely unclear. To dissect molecular and cellular mechanisms of cardiac remodeling in CKD in an unbiased fashion, we performed left ventricular single-nuclear RNA sequencing in two mouse models of CKD. Our data showed a hypertrophic response trajectory of cardiomyocytes with stress signaling and metabolic changes driven by soluble uremia-related factors. We mapped fibroblast to myofibroblast differentiation in this process and identified notable changes in the cardiac vasculature, suggesting inflammation and dysfunction. An integrated analysis of cardiac cellular responses to uremic toxins pointed toward endothelin-1 and methylglyoxal being involved in capillary dysfunction and TNFα driving cardiomyocyte hypertrophy in CKD, which was validated in vitro and in vivo. TNFα inhibition in vivo ameliorated the cardiac phenotype in CKD. Thus, interventional approaches directed against uremic toxins, such as TNFα, hold promise to ameliorate cardiac remodeling in CKD.

The role of autoimmunity and autoinflammation in giant cell arteritis: A systematic literature review

Giant cell arteritis is the most common form of large vessel vasculitis and preferentially involves large and medium-sized arteries in patients over the age of 50. Aggressive wall inflammation, neoangiogenesis and consecutive remodeling processes are the hallmark of the disease. Though etiology is unknown, cellular and humoral immunopathological processes are well understood. Matrix metalloproteinase-9 mediated tissue infiltration occurs through lysis of basal membranes in adventitial vessels. CD4+ cells attain residency in immunoprotected niches, differentiate into vasculitogenic effector cells and enforce further leukotaxis. Signaling pathways involve the NOTCH1-Jagged1 pathway opening vessel infiltration, CD28 mediated T-cell overstimulation, lost PD-1/PD-L1 co-inhibition and JAK/STAT signaling in interferon dependent responses. From a humoral perspective, IL-6 represents a classical cytokine and potential Th-cell differentiator whereas interferon-γ (IFN- γ) has been shown to induce chemokine ligands. Current therapies involve glucocorticoids, tocilizumab and methotrexate application. However, new agents, most notably JAK/STAT inhibitors, PD-1 agonists and MMP-9 blocking substances, are being evaluated in ongoing clinical trials.

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.

Peripheral apoE4 enhances Alzheimer's pathology and impairs cognition by compromising cerebrovascular function

The ε4 allele of the apolipoprotein E (APOE) gene, a genetic risk factor for Alzheimer's disease, is abundantly expressed in both the brain and periphery. Here, we present evidence that peripheral apoE isoforms, separated from those in the brain by the blood-brain barrier, differentially impact Alzheimer's disease pathogenesis and cognition. To evaluate the function of peripheral apoE, we developed conditional mouse models expressing human APOE3 or APOE4 in the liver with no detectable apoE in the brain. Liver-expressed apoE4 compromised synaptic plasticity and cognition by impairing cerebrovascular functions. Plasma proteome profiling revealed apoE isoform-dependent functional pathways highlighting cell adhesion, lipoprotein metabolism and complement activation. ApoE3 plasma from young mice improved cognition and reduced vessel-associated gliosis when transfused into aged mice, whereas apoE4 compromised the beneficial effects of young plasma. A human induced pluripotent stem cell-derived endothelial cell model recapitulated the plasma apoE isoform-specific effect on endothelial integrity, further supporting a vascular-related mechanism. Upon breeding with amyloid model mice, liver-expressed apoE4 exacerbated brain amyloid pathology, whereas apoE3 reduced it. Our findings demonstrate pathogenic effects of peripheral apoE4, providing a strong rationale for targeting peripheral apoE to treat Alzheimer's disease.

Astrocyte depletion alters extracellular matrix composition in the demyelinating phase of Theiler's murine encephalomyelitis

Astrocytes produce extracellular matrix (ECM) glycoproteins contributing to the blood-brain barrier and regulating the immune response in the central nervous system (CNS). The aim of this study was to investigate the impact of astrocyte depletion upon the clinical outcome and the composition of ECM glycoproteins in a virus-induced animal model of demyelination. Glial fibrillary acidic protein (GFAP)-thymidine-kinase transgenic SJL (GFAP-knockout) and wildtype mice were infected with Theiler’s murine encephalomyelitis virus (TMEV). Astrocyte depletion was induced during the progressive, demyelinating disease phase by ganciclovir administration once daily between 56 and 77 days post infection (dpi). At 77 dpi GFAP-knockout mice showed a significant deterioration of clinical signs associated with a reduction of azan and picrosirius red stained ECM-molecules in the thoracic spinal cord. Basement-membrane-associated ECM-molecules including laminin, entactin/nidogen-1 and Kir4.1 as well as non-basement membrane-associated ECM-molecules like collagen I, decorin, tenascin-R and CD44 were significantly reduced in the spinal cord of GFAP-knockout mice. The reduction of the investigated ECM-molecules demonstrates that astrocytes play a key role in the production of ECM-molecules. The present findings indicate that the detected loss of Kir4.1 and CD44 as well as the disruption of the integrity of perineuronal nets led to the deterioration of clinical signs in GFAP-knockout mice.

An Autoantigen Atlas From Human Lung HFL1 Cells Offers Clues to Neurological and Diverse Autoimmune Manifestations of COVID-19

COVID-19 is accompanied by a myriad of both transient and long-lasting autoimmune responses. Dermatan sulfate (DS), a glycosaminoglycan crucial for wound healing, has unique affinity for autoantigens (autoAgs) from apoptotic cells. DS-autoAg complexes are capable of stimulating autoreactive B cells and autoantibody production. We used DS-affinity proteomics to define the autoantigen-ome of lung fibroblasts and bioinformatics analyses to study the relationship between autoantigenic proteins and COVID-induced alterations. Using DS-affinity, we identified an autoantigen-ome of 408 proteins from human HFL1 cells, at least 231 of which are known autoAgs. Comparing with available COVID data, 352 proteins of the autoantigen-ome have thus far been found to be altered at protein or RNA levels in SARS-CoV-2 infection, 210 of which are known autoAgs. The COVID-altered proteins are significantly associated with RNA metabolism, translation, vesicles and vesicle transport, cell death, supramolecular fibrils, cytoskeleton, extracellular matrix, and interleukin signaling. They offer clues to neurological problems, fibrosis, smooth muscle dysfunction, and thrombosis. In particular, 150 altered proteins are related to the nervous system, including axon, myelin sheath, neuron projection, neuronal cell body, and olfactory bulb. An association with the melanosome is also identified. The findings from our study illustrate a connection between COVID infection and autoimmunity. The vast number of COVID-altered proteins with high intrinsic propensity to become autoAgs offers an explanation for the diverse autoimmune complications in COVID patients. The variety of autoAgs related to mRNA metabolism, translation, and vesicles suggests a need for long-term monitoring of autoimmunity in COVID. The COVID autoantigen atlas we are establishing provides a detailed molecular map for further investigation of autoimmune sequelae of the pandemic, such as "long COVID" syndrome.

Summary Sentence

An autoantigen-ome by dermatan sulfate affinity from human lung HFL1 cells may explain neurological and autoimmune manifestations of COVID-19.

Transcriptomic analysis of choroidal neovascularization reveals dysregulation of immune and fibrosis pathways that are attenuated by a novel anti-fibrotic treatment

Neovascular AMD (nAMD) leads to vision loss and is a leading cause of visual impairment in the industrialised world. Current treatments that target blood vessel growth have not been able to treat subretinal fibrosis and nAMD patients continue to lose vision. The molecular mechanisms involved in the development of fibrotic lesions in nAMD are not well understood. The aim of this study was to further understand subretinal fibrosis in the laser photocoagulation model of choroidal neovascularization (CNV) by studying the whole transcriptome of the RPE/choroid following CNV and the application of an anti-fibrotic following CNV. Seven days after laser induced CNV, RPE and choroid tissue was separated and underwent RNAseq. Differential expression analysis and pathway analysis revealed an over representation of immune signalling and fibrotic associated pathways in CNV compared to control RPE/choroid tissue. Comparisons between the mouse CNV model to human CNV revealed an overlap in upregulated expression for immune genes (Ccl2, Ccl8 and Cxcl9) and extracellular matrix remodeling genes (Comp, Lrcc15, Fndc1 and Thbs2). Comparisons between the CNV model and other fibrosis models showed an overlap of over 60% of genes upregulated in either lung or kidney mouse models of fibrosis. Treatment of CNV using a novel cinnamoyl anthranilate anti-fibrotic (OCX063) in the laser induced CNV model was selected as this class of drugs have previously been shown to target fibrosis. CNV lesion leakage and fibrosis was found to be reduced using OCX063 and gene expression of genes within the TGF-beta signalling pathway. Our findings show the presence of fibrosis gene expression pathways present in the laser induced CNV mouse model and that anti-fibrotic treatments offer the potential to reduce subretinal fibrosis in AMD.

Proangiogenic Collagen-Binding Glycan Therapeutic Promotes Endothelial Cell Angiogenesis

Stimulating angiogenesis during wound healing continues to present a significant clinical challenge, given the limitations of current strategies to maintain therapeutic doses of growth factors and endothelial cell efficacy. Incorporating a balance of specific cues to encourage endothelial cell engraftment and cytokines to facilitate angiogenesis is necessary for blood vessel growth in the proinflammatory wound environment. Here, we incorporate a previously designed peptide (LXW7) capable of binding to the αvβ3 integrin of endothelial cells with a dermatan sulfate glycosaminoglycan backbone grafted with collagen-binding peptides (SILY). By exploiting αvβ3 integrin-mediated VEGF signaling, we propose an alternative strategy to overcome shortcomings of traditional growth factor therapy while homing the peptide to the wound bed. In this study, we describe the synthesis and optimization of LXW7-DS-SILY (LDS) variants and evaluate their angiogenic potential in vitro and in vivo. LDS displayed binding to collagen and endothelial cells. In vitro, the LDS variant with six LXW7 peptides increased endothelial cell proliferation, migration, and tubule formation through increased VEGFR2 phosphorylation compared to nontreated controls. In an in vivo chick chorioallantoic membrane assay, LDS laden collagen hydrogels increased blood vessel formation by 43% in comparison to the organism matched blank hydrogels. Overall, these findings demonstrate the potential of a robust targeted glycan therapeutic for promoting angiogenesis during wound healing.

Post-stroke Delivery of Valproic Acid Promotes Functional Recovery and Differentially Modifies Responses of Peri-Infarct Microglia

The specific role of peri-infarct microglia and the timing of its morphological changes following ischemic stroke are not well understood. Valproic acid (VPA) can protect against ischemic damage and promote recovery. In this study, we first determined whether a single dose of VPA after stroke could decrease infarction area or improve functional recovery. Next, we investigated the number and morphological characteristic of peri-infarct microglia at different time points and elucidated the mechanism of microglial response by VPA treatment. Male Sprague-Dawley rats were subjected to distal middle cerebral artery occlusion (dMCAo) for 90 min, followed by reperfusion. Some received a single injection of VPA (200 mg/kg) 90 min after the induction of ischemia, while vehicle-treated animals underwent the same procedure with physiological saline. Infarction volume was calculated at 48 h after reperfusion, and neurological symptoms were evaluated. VPA didn’t significantly reduce infarct volume but did ameliorate neurological deficit at least partially compared with vehicle. Meanwhile, VPA reduced dMCAo-induced elevation of IL-6 at 24 h post-stroke and significantly decreased the number of CD11b-positive microglia within peri-infarct cortex at 7 days. Morphological analysis revealed that VPA therapy leads to higher fractal dimensions, smaller soma size and lower circularity index of CD11b-positive cells within peri-infarct cortex at both 2 and 7 days, suggesting that VPA has core effects on microglial morphology. The modulation of microglia morphology caused by VPA might involve HDAC inhibition-mediated suppression of galectin-3 production. Furthermore, qPCR analysis of CD11b-positive cells at 3 days post-stroke suggested that VPA could partially enhance M2 subset polarization of microglia in peri-infarct cortex. Analysis of VPA-induced changes to gene expressions at 3 days post-stroke implies that these alternations of the biomarkers and microglial responses are implicated in the upregulation of wound healing, collagen trimmer, and extracellular matrix genes within peri-infarct cortex. Our results are the first to show that a low dose of VPA promotes short-term functional recovery but does not alter infarct volume. The decreases in the expression of both IL-6 and galectin-3 might influence the morphological characteristics and transcriptional profiles of microglia and extracellular matrix remodeling, which could contribute to the improved recovery.

An Autoantigen Atlas from Human Lung HFL1 Cells Offers Clues to Neurological and Diverse Autoimmune Manifestations of COVID-19

COVID-19 is accompanied by a myriad of both transient and long-lasting autoimmune responses. Dermatan sulfate (DS), a glycosaminoglycan crucial for wound healing, has unique affinity for autoantigens (autoAgs) from apoptotic cells. DS-autoAg complexes are capable of stimulating autoreactive B cells and autoantibody production. Using DS affinity, we identified an autoantigenome of 408 proteins from human fetal lung fibroblast HFL11 cells, at least 231 of which are known autoAgs. Comparing with available COVID data, 352 proteins of the autoantigenome have thus far been found to be altered at protein or RNA levels in SARS-Cov-2 infection, 210 of which are known autoAgs. The COVID-altered proteins are significantly associated with RNA metabolism, translation, vesicles and vesicle transport, cell death, supramolecular fibrils, cytoskeleton, extracellular matrix, and interleukin signaling. They offer clues to neurological problems, fibrosis, smooth muscle dysfunction, and thrombosis. In particular, 150 altered proteins are related to the nervous system, including axon, myelin sheath, neuron projection, neuronal cell body, and olfactory bulb. An association with the melanosome is also identified. The findings from our study illustrate a strong connection between viral infection and autoimmunity. The vast number of COVID-altered proteins with propensity to become autoAgs offers an explanation for the diverse autoimmune complications in COVID patients. The variety of autoAgs related to mRNA metabolism, translation, and vesicles raises concerns about potential adverse effects of mRNA vaccines. The COVID autoantigen atlas we are establishing provides a detailed molecular map for further investigation of autoimmune sequelae of the pandemic.

Proteoglycans in the periodontium: A review with emphasis on specific distributions, functions, and potential applications

Proteoglycans (PGs) are largely glycosylated proteins, consisting of a linkage sugar, core proteins, and glycosaminoglycans (GAGs). To date, more than 40 kinds of PGs have been identified, and they can be classified as intracellular, cell surface, pericellular, and extracellular PGs according to cellular locations. To illustrate, extracellular PGs are known for regulating the homeostasis of the extracellular matrix; cell-surface PGs play a role in mediating cell adhesion and binding various growth factors. In the field of periodontology, PGs are implicated in cellular proliferation, migration, adhesion, contractility, and anoikis, thereby exerting a profound influence on periodontal tissue development, wound repair, the immune response, biomechanics, and pathological process. Additionally, the expression patterns of some PGs are dynamic and cell-specific. Therefore, determining the roles and spatial-temporal expression patterns of PGs in the periodontium could shed light on treatments for wound healing, tissue regeneration, periodontitis, and gingival overgrowth. In this review, close attention is paid to the distributions, functions, and potential applications of periodontal PGs. Related genetically modified animal experiments and involved signal transduction cascades are summarized for improved understanding of periodontal PGs. To date, however, there is a large amount of speculation on this topic that requires rigorous experiments for validation.

Oxidative stress and mitochondrial dysfunction in early-onset and late-onset preeclampsia

Preeclampsia is a pregnancy-specific syndrome with multisystem involvement which leads to foetal, neonatal, and maternal morbidity and mortality. This syndrome is characterized by the onset of clinical signs and symptoms and delivery before (early-onset preeclampsia, eoPE), or after (late-onset preeclampsia, loPE), the 34 weeks of gestation. Preeclampsia is a mitochondrial disorder where its differential involvement in eoPE and loPE is unclear. Mitochondria regulate cell metabolism and are a significant source of reactive oxygen species (ROS). The syncytiotrophoblast in eoPE and loPE show altered mitochondrial structure and function resulting in ROS overproduction, oxidative stress, and cell damage and death. Mitochondrial dysfunction in eoPE may result from altered expression of several molecules, including dynamin-related protein 1 and mitofusins, compared with loPE where these factors are either reduced or unaltered. Equally, mitochondrial fusion/fission dynamics seem differentially modulated in eoPE and loPE. It is unclear whether the electron transport chain and oxidative phosphorylation are differentially altered in these two subgroups of preeclampsia. However, the activity of complex IV (cytochrome c oxidase) and the expression of essential proteins involved in the electron transport chain are reduced, leading to lower oxidative phosphorylation and mitochondrial respiration in the preeclamptic placenta. Interventional studies in patients with preeclampsia using the coenzyme Q₁₀, a key molecule in the electron transport chain, suggest that agents that increase the antioxidative capacity of the placenta may be protective against preeclampsia development. In this review, the mitochondrial dysfunction in both eoPE and loPE is summarized. Therapeutic approaches are discussed in the context of contributing to the understanding of mitochondrial dysfunction in eoPE and loPE.

Peritoneal Proteoglycans: Much more than Ground Substance

Recent advances in the field of glycobiology have exposed a multitude of biological processes that are controlled or influenced by proteoglycans, in both physiological and pathological conditions ranging from early embryonic development, inflammation, and fibrosis to tumor invasion and metastasis. The first part of this article reviews the biosynthesis of proteoglycans and their multifunctional roles in health and disease; the second part of this review focuses on their putative roles in peritoneal homeostasis and peritoneal inflammation and fibrosis in the context of chronic peritoneal dialysis and peritonitis.

Mineralocorticoid receptor antagonism limits experimental choroidal neovascularization and structural changes associated with neovascular age-related macular degeneration

Choroidal neovascularization (CNV) is a major cause of visual impairment in patients suffering from wet age-related macular degeneration (AMD), particularly when refractory to intraocular anti-VEGF injections. Here we report that treatment with the oral mineralocorticoid receptor (MR) antagonist spironolactone reduces signs of CNV in patients refractory to anti-VEGF treatment. In animal models of wet AMD, pharmacological inhibition of the MR pathway or endothelial-specific deletion of MR inhibits CNV through VEGF-independent mechanisms, in part through upregulation of the extracellular matrix protein decorin. Intravitreal injections of spironolactone-loaded microspheres and systemic delivery lead to similar reductions in CNV. Together, our work suggests MR inhibition as a novel therapeutic option for wet AMD patients unresponsive to anti-VEGF drugs.

The immunoinhibitory PD-1/PD-L1 pathway in inflammatory blood vessel disease

Because of their vital function, the wall structures of medium and large arteries are immunoprivileged and protected from inflammatory attack. That vascular immunoprivilege is broken in atherosclerosis and in vasculitis, when wall-invading T cells and macrophages (Mϕ) promote tissue injury and maladaptive repair. Historically, tissue-residing T cells were studied for their antigen specificity, but recent progress has refocused attention to antigen-nonspecific regulation, which determines tissue access, persistence, and functional differentiation of T cells. The coinhibitory receptor PD-1, expressed on T cells, delivers negative signals when engaged by its ligand PD-L1, expressed on dendritic cells, Mϕ, and endothelial cells to attenuate T cell activation, effector functions, and survival. Through mitigating signals, the PD-1 immune checkpoint maintains tissue tolerance. In line with this concept, dendritic cells and Mϕs from patients with the vasculitic syndrome giant cell arteritis (GCA) are PD-L1^lo ; including vessel-wall-embedded DCs that guard the vascular immunoprivilege. GCA infiltrates in the arterial walls are filled with PD-1⁺ T cells that secrete IFN-γ, IL-17, and IL-21; drive inflammation-associated angiogenesis; and facilitate intimal hyperplasia. Conversely, chronic tissue inflammation in the atherosclerotic plaque is associated with an overreactive PD-1 checkpoint. Plaque-residing Mϕs are PD-L1^hi , a defect induced by their addiction to glucose and glycolytic breakdown. PD-L1^hi Mϕs render patients with coronary artery disease immunocompromised and suppress antiviral immunity, including protective anti-varicella zoster virus T cells. Thus, immunoinhibitory signals affect several domains of vascular inflammation; failing PD-L1 in vasculitis enables unopposed immunostimulation and opens the flood gates for polyfunctional inflammatory T cells, and excess PD-L1 in the atherosclerotic plaque disables tissue-protective T cell immunity.

Decorin mimic promotes endothelial cell health in endothelial monolayers and endothelial-smooth muscle co-cultures

Non-specific cytotoxins, including paclitaxel and sirolimus analogues, currently utilized as anti-restenotic therapeutics, affect not only smooth muscle cells (SMCs) but also neighbouring vascular endothelial cells (ECs). These drugs inhibit the formation of an intact endothelium following vessel injury, thus emphasizing the critical need for new candidate therapeutics. Utilizing our in vitro models, including EC monolayers and both hyperplastic and quiescent EC-SMC co-cultures, we investigated the ability of DS-SILY₂₀ , a decorin mimic, to promote EC health. DS-SILY₂₀ increased EC proliferation and migration by 1.5- and 2-fold, respectively, which corresponded to increased phosphorylation of ERK-1/2. Interestingly, IL-6 secretion and the production of both E-selectin and P-selectin were reduced in the presence of 10 μm DS-SILY₂₀ , even in the presence of the potent pro-inflammatory cytokine platelet-derived growth factor (PDGF). In hyperplastic and quiescent EC-SMC co-cultures, DS-SILY₂₀ treatment reduced the secretion of IFNγ, IL-1β, IL-6 and TNFα, corresponding to a 23% decrease in p38 phosphorylation. E-selectin and P-selectin expression was further reduced following DS-SILY₂₀ treatment in both co-culture models. These results indicate that DS-SILY₂₀ promotes EC health and that this decorin mimic could serve as a potential therapeutic to promote vessel healing following percutaneous coronary intervention (PCI). Copyright © 2015 John Wiley & Sons, Ltd.

Rare Case of Spindle Cell Haemangioma

Spindle cell haemangioma (SCH) is a benign vascular lesion which usually occurs on distal extremities. It was previously regarded as haemangioendothelioma and was initially perceived to be low grade angiosarcoma.They are characterized by cavernous blood vessels and spindle cell proliferation. It is now considered as a reactive lesion and conservative surgical excision is preferred treatment. Intraoral occurrence is rare; hence we present a case of SCH in a 33-year-old male that presented as a swelling below the tongue. Histopathology showed well circumscribed proliferating spindle cells attached to vessel walls, dilated vascular spaces. The lesion was positive for CD31 and CD34 markers suggesting it to be of endothelial cell origin.

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.

Altered decorin leads to disrupted endothelial cell function: a possible mechanism in the pathogenesis of fetal growth restriction?

OBJECTIVE

Fetal growth restriction (FGR) is a key cause of adverse pregnancy outcome where maternal and fetal factors are identified as contributing to this condition. Idiopathic FGR is associated with altered vascular endothelial cell functions. Decorin (DCN) has important roles in the regulation of endothelial cell functions in vascular environments. DCN expression is reduced in FGR. The objectives were to determine the functional consequences of reduced DCN in a human microvascular endothelial cell line model (HMVEC), and to determine downstream targets of DCN and their expression in primary placental microvascular endothelial cells (PLECs) from control and FGR-affected placentae.

APPROACH

Short-interference RNA was used to reduce DCN expression in HMVECs and the effect on proliferation, angiogenesis and thrombin generation was determined. A Growth Factor PCR Array was used to identify downstream targets of DCN. The expression of target genes in control and FGR PLECs was performed.

RESULTS

DCN reduction decreased proliferation and angiogenesis but increased thrombin generation with no effect on apoptosis. The array identified three targets of DCN: FGF17, IL18 and MSTN. Validation of target genes confirmed decreased expression of VEGFA, MMP9, EGFR1, IGFR1 and PLGF in HMVECs and PLECs from control and FGR pregnancies.

CONCLUSIONS

Reduction of DCN in vascular endothelial cells leads to disrupted cell functions. The targets of DCN include genes that play important roles in angiogenesis and cellular growth. Therefore, differential expression of these may contribute to the pathogenesis of FGR and disease states in other microvascular circulations.

Microarray analysis for genes associated with angiogenesis in diabetic OLETF keratocytes

The purpose of this study was to identify the differences in angiogenesis gene expression between normal and diabetic keratocytes stimulated with interleukin-1α (IL-1α) and tumor necrosis factor-α (TNF-α). Primarily cultured normal and diabetic keratocytes were treated with 20 ng/mL of IL-1a and TNF-α for 6 hr. cDNA was hybridized to an oligonucleotide microarray. Microarray analysis was used to identify differentially expressed genes that were further evaluated by real-time polymerase chain reaction (RT-PCR). Diabetes keratocytes overexpressed vital components of angiogenesis including Agtr1, and under-expressed components related to the blood vessel maturation, including Dcn. Cytokine-treated diabetic keratocytes differentially expressed components of angiogenesis. OLETF keratocytes after treatment with IL-1α and TNF-α showed the newly expressed 15 and 14 genes, respectively. Newly and commonly under-expressed five genes followed by treatment with both IL-1α and TNF-α were also evident. RT-PCR showed results similar to the microarray results. Agtr1 and Itga1 showed an increased expression in diabetic keratocytes compared with normal corneal keratocytes, especially after TNF-α treatment. Il6 appeared strong expression after interleukin-1α treatment, but showed down expression after TNF-α treatment. Further studies to analyze and confirm the significance of the identified angiogenetic genes of diabetes are needed.

An essential role for decorin in bladder cancer invasiveness

Muscle-invasive forms of urothelial carcinomas are responsible for most mortality in bladder cancer. Finding new treatments for invasive bladder tumours requires adequate animal models to decipher the mechanisms of progression, in particular the way tumours interact with their microenvironment. Herein, using the murine bladder tumour cell line MB49 and its more aggressive variant MB49-I, we demonstrate that the adaptive immune system efficiently limits progression of MB49, whereas MB49-I has lost tumour antigens and is insensitive to adaptive immune responses. Furthermore, we unravel a parallel mechanism developed by MB49-I to subvert its environment: de novo secretion of the proteoglycan decorin. We show that decorin overexpression in the MB49/MB49-I model is required for efficient progression, by promoting angiogenesis and tumour cell invasiveness. Finally, we show that these results are relevant to muscle-invasive human bladder carcinomas, which overexpress decorin together with angiogenesis- and adhesion/migration-related genes, and that decorin overexpression in the human bladder carcinoma cell line TCCSUP is required for efficient invasiveness in vitro. We thus propose decorin as a new therapeutic target for these aggressive tumours.

MT1-MMP cleavage of the antiangiogenic proteoglycan decorin: role in corneal angiogenesis

PURPOSE

Decorin is a small chondroitin sulfate proteoglycan that inhibits vascular endothelial cell migration and tube formation. Membrane type 1-matrix metalloproteinase (MT1-MMP) has been shown to be an important angiogenic enzyme in the cornea. We evaluated the specific role of MT1-MMP in decorin cleavage in the cornea.

METHODS

Western blotting was used to evaluate decorin degradation by MT1-MMP. Aortic ring tube formation assays were used to assay the inhibitory effect of decorin and the stimulatory effect of MT1-MMP on vascular endothelial cells in vitro. Corneal micropocket assays using basic fibroblast growth factor (bFGF) were used to assess changes in the levels of decorin and MT1-MMP.

RESULTS

MT1-MMP cleaves decorin in a time- and concentration-dependent manner in vitro. MT1-MMP levels were upregulated after in vivo bFGF pellet implantation in the cornea, and decorin cleavage products were detected in bFGF-implanted corneas but not in normal corneas. MT1-MMP reduced the inhibitory effects of decorin on aortic ring tube formation in vitro.

CONCLUSION

MT1-MMP may play an essential role in angiogenesis through proteolytic processing of decorin in the cornea.

Decorin antagonizes the angiogenic network: concurrent inhibition of Met, hypoxia inducible factor 1α, vascular endothelial growth factor A, and induction of thrombospondin-1 and TIMP3

Decorin, a small leucine-rich proteoglycan, inhibits tumor growth by antagonizing multiple receptor tyrosine kinases including EGFR and Met. Here, we investigated decorin during normoxic angiogenic signaling. An angiogenic PCR array revealed a profound decorin-evoked transcriptional inhibition of pro-angiogenic genes, such as HIF1A. Decorin evoked a reduction of hypoxia inducible factor (HIF)-1α and vascular endothelial growth factor A (VEGFA) in MDA-231 breast carcinoma cells expressing constitutively-active HIF-1α. Suppression of Met with decorin or siRNA evoked a similar reduction of VEGFA by attenuating downstream β-catenin signaling. These data establish a noncanonical role for β-catenin in regulating VEGFA expression. We found that exogenous decorin induced expression of thrombospondin-1 and TIMP3, two powerful angiostatic agents. In contrast, decorin suppressed both the expression and enzymatic activity of matrix metalloprotease (MMP)-9 and MMP-2, two pro-angiogenic proteases. Our data establish a novel duality for decorin as a suppressor of tumor angiogenesis under normoxia by simultaneously down-regulating potent pro-angiogenic factors and inducing endogenous anti-angiogenic agents.

Decorin in atherosclerosis

Atherosclerotic cardiovascular disease is a major cause of morbidity and mortality in the Western world. Despite tremendous strides in understandings its pathogenesis, it still remains a challenge because of gaps in our understanding of its initiation, progression and complications leading to the clinical syndromes of angina, acute coronary syndrome, cerebrovascular disease and peripheral vascular disease. Recent studies have provided impetus on the shift from models of atherosclerosis based on cellular interactions to models where the important role of extracellular matrix is recognized. Proteoglycans, especially those belonging to the small leucine-rich proteoglycan family of which decorin is a representative example, have come under close scrutiny for their role in atherogenesis. There is evidence from in vitro and in vivo animal models as well as humans to suggest an important role of decorin in attenuating progression of atherosclerosis. Decorin distribution in different blood vessels has been shown to inversely correlate with the tendency to develop atherosclerosis. Decorin seems to interact closely with different cellular components of the plaque milieu, thereby suggesting its role in influencing atherogenesis at different steps. Here we review the current understanding of the role of decorin in the pathogenesis of atherosclerosis.

The role for decorin in delayed-type hypersensitivity

Decorin, a small leucine-rich proteoglycan, regulates extracellular matrix organization, growth factor-mediated signaling, and cell growth. Because decorin may directly modulate immune responses, we investigated its role in a mouse model of contact allergy (oxazolone-mediated delayed-type hypersensitivity [DTH]) in decorin-deficient (Dcn(-/-)) and wild-type mice. Dcn(-/-) mice showed a reduced ear swelling 24 h after oxazolone treatment with a concurrent attenuation of leukocyte infiltration. These findings were corroborated by reduced glucose metabolism, as determined by (18)fluordeoxyglucose uptake in positron emission tomography scans. Unexpectedly, polymorphonuclear leukocyte numbers in Dcn(-/-) blood vessels were significantly increased and accompanied by large numbers of flattened leukocytes adherent to the endothelium. Intravital microscopy and flow chamber and static adhesion assays confirmed increased adhesion and reduced transmigration of Dcn(-/-) leukocytes. Circulating blood neutrophil numbers were significantly increased in Dcn(-/-) mice 24 h after DTH elicitation, but they were only moderately increased in wild-type mice. Expression of the proinflammatory cytokine TNF-α was reduced, whereas syndecan-1 and ICAM-1 were overexpressed in inflamed ears of Dcn(-/-) mice, indicating that these adhesion molecules could be responsible for increased leukocyte adhesion. Decorin treatment of endothelial cells increased tyrosine phosphorylation and reduced syndecan-1 expression. Notably, absence of syndecan-1 in a genetic background lacking decorin rescued the attenuated DTH phenotype of Dcn(-/-) mice. Collectively, these results implicated a role for decorin in mediating DTH responses by influencing polymorphonuclear leukocyte attachment to the endothelium. This occurs via two nonmutually exclusive mechanisms that involve a direct antiadhesive effect on polymorphonuclear leukocytes and a negative regulation of ICAM-1 and syndecan-1 expression.

Decorin gene expression and its regulation in human keratinocytes

In various cell types, including cancer cells, decorin is involved in regulation of cell attachment, migration and proliferation. In skin, decorin is seen in dermis, but not in keratinocytes. We show that decorin gene (DCN) is expressed in the cultured keratinocytes, and the protein is found in the cytoplasm of differentiating keratinocytes and in suprabasal layers of human epidermis. RT-PCR experiments showed that DCN expression is regulated by pro-inflammatory and proliferative cytokines. Our data suggest that decorin should play a significant role in keratinocyte terminal differentiation, cutaneous homeostasis and dermatological diseases.

An isoform of decorin is a resistin receptor on the surface of adipose progenitor cells

Adipose stromal cells (ASCs) serve as mesenchymal progenitors in white adipose tissue (WAT). Intercellular interactions involving ASCs have remained obscure. By merging phage display technology with fluorescence-activated cell sorting (FACS), we screened a combinatorial library for peptides that target mouse ASCs in vivo. We isolated peptide CSWKYWFGEC that specifically homes to ASCs, used it as bait to purify the corresponding ASC surface receptor, and identified it as a previously unreported cleavage product of decorin (DCN) lacking the glycanation site (termed ΔDCN). We demonstrate that ΔDCN is differentially expressed on ASC surface. In a screen for ΔDCN-binding proteins, we identified resistin, an adipokine for which the receptor has been unknown. Expression of ΔDCN in 3T3-L1 cells promoted proliferation and migration but suppressed lipid accumulation upon adipogenesis induction, which was resistin dependent. We conclude that ΔDCN serves as a functional receptor of resistin in adipocyte progenitors and may regulate WAT expansion.

Isolation of interstitial fluid in skin during volume expansion: evaluation of a method in pigs

The ability to isolate interstitial fluid (IF) from skin would make it possible to study the microcirculation and proteins in this environment both during normal and pathophysiological conditions. Traditional IF sampling using implanted wicks suffer from low volumes with risk of contamination by local inflammatory, intracellular, and vascular proteins. To sample larger volumes of true IF, a recently described tissue centrifugation method was compared with dry and wet wicks from porcine skin under normal conditions and following volume expansion. With all three methods, volume expansion caused a significant lowering of interstitial colloid osmotic pressure as expected, and the fluid was similar to plasma when compared using size-exclusion HPLC. The centrifugation method was superior with respect to isolating larger amounts of true IF for further studies. Mass spectrometry of IF sampled with centrifugation showed that most of the proteins reflected the major plasma proteins with some tissue-specific proteins like decorin, gelsolin, and orosomucoid-1. Lumican, pigment epithelium-derived factor, and fatty acid-binding protein 4 were only identified in IF after volume expansion, possibly reflecting a local response to increased fluid filtration. Tissue centrifugation to collect IF from skin should be applicable to both clinical and experimental studies on IF balance during different pathophysiological conditions and interventions.

Extracellular matrix in multiple sclerosis lesions: Fibrillar collagens, biglycan and decorin are upregulated and associated with infiltrating immune cells

Extracellular matrix (ECM) proteins can modify immune reactions, e.g. by sequestering or displaying growth factors and by interacting with immune and glial cells. Here we quantified by quantitative polymerase chain reaction (qPCR) expression of 50 ECM components and 34 ECM degrading enzymes in multiple sclerosis (MS) active and inactive white matter lesions. COL1A1, COL3A1, COL5A1 and COL5A2 chains were induced strongly in active lesions and even more in inactive lesions. These chains interact to form collagen types I, III and V, which are fibrillar collagens. Biglycan and decorin, which can decorate fibrillar collagens, were also induced strongly. The fibrillar collagens, biglycan and decorin were largely found between the endothelium and astrocytic glia limitans in the perivascular space where they formed a meshwork which was closely associated with infiltrating immune cells. In active lesions collagen V was also seen in the heavily infiltrated parenchyma. Fibrillar collagens I and III inhibited in vitro human monocyte production of CCL2 (MCP-1), an inflammatory chemokine involved in recruitment of immune cells. Together, ECM changes in lesions with different activities were quantified and proteins forming a perivascular fibrosis were identified. Induced fibrillar collagens may contribute to limiting enlargement of MS lesions by inhibiting the production of CCL2 by monocytes.

Influence of adult mesenchymal stem cells on in vitro vascular formation

The effective delivery of bioactive molecules to wound sites hasten repair. Cellular therapies provide a means for the targeted delivery of a complex, multiple arrays of bioactive factors to wound sites. Thus, the identification of ideal therapeutic populations is an essential aspect of this approach. In vitro assays can provide an important first step toward this goal by selecting populations that are likely suitable for more expensive and time-consuming in vivo assays. In this study, bone marrow-derived mesenchymal stem cells (BM-MSCs) were integrated into a three-dimensional coculture system that supports the development and stabilization of vascular tube-like structures. The presence of a limited number of BM-MSCs resulted in their coalignment with vascular structures, and it further resulted in increased tubule numbers and complexity. Thus, these studies suggest that BM-MSCs functionally interacted with and were attracted to in vitro formed vascular structures. Further, these cells also provided sufficient bioactive factors and matrix molecules to support the formation of tubular arrays and the stabilization of these arrays. This in vitro system provides a means for assessing the function of BM-MSCs in aspects of the angiogenic component of wound repair.

MT1-MMP-mediated cleavage of decorin in corneal angiogenesis

BACKGROUND/AIMS

Decorin has been shown to have antiangiogenic properties. In this study, we evaluate the involvement of membrane type 1-matrix metalloproteinase (MT1-MMP), a proangiogenic enzyme, in decorin cleavage in the cornea.

METHODS

MT1-MMP expression was confirmed immunohistochemically in keratocytes and immortalized corneal fibroblast cell lines. Corneal micropockets of bFGF were used to assess the expression of decorin and MT1-MMP. Western blotting was used to evaluate decorin degradation by MT1-MMP. Aortic ring tube formation assays were used to assay the inhibitory effect of decorin and stimulatory effect of MT1-MMP on vascular endothelial cells in vitro.

RESULTS

We show that MT1-MMP expression is upregulated following bFGF pellet implantation in the cornea in vivo, and that MT1-MMP cleaves decorin in a time- and concentration-dependent manner in vitro. Furthermore, the addition of MT1-MMP reduces the inhibitory effects of decorin on aortic ring tube formation in vitro. Cleavage of decorin by MT1-MMP-deficient corneal cell lysates is diminished relative to that by wild-type corneal cell lysates, and an MT1-MMP knockin restores decorin processing in vitro.

CONCLUSION

The proangiogenic role of MT1-MMP in the cornea may be mediated, in part, by facilitated cleavage of corneal decorin.

Decorin regulates endothelial cell-matrix interactions during angiogenesis

Interactions between endothelial cells and the surrounding extracellular matrix are continuously adapted during angiogenesis, from early sprouting through to lumen formation and vessel maturation. Regulated control of these interactions is crucial to sustain normal responses in this rapidly changing environment, and dysfunctional endothelial cell behaviour results in angiogenic disorders. The proteoglycan decorin, an extracellular matrix component, is upregulated during angiogenesis. While it was shown previously that the absence of decorin leads to dysregulated angiogenesis in vivo, the molecular mechanisms were not clear. These abnormal endothelial cell responses have been attributed to indirect effects of decorin; however, our recent data provides evidence that decorin directly regulates endothelial cell-matrix interactions. This data will be discussed in conjunction with findings from previous studies, to better understand the role of this proteoglycan in angiogenesis.

Proteomic profiling in early venous stenosis formation in a porcine model of hemodialysis graft

PURPOSE

To use proteomic analysis to identify up- and downregulated proteins in early venous stenosis formation in a porcine model of hemodialysis graft failure.

MATERIALS AND METHODS

Pigs had chronic renal insufficiency created by subtotal renal infarction caused by renal artery embolization. Arteriovenous polytetrafluoroethylene grafts were placed 28 days later and the animals were killed after a further 3 days (n = 4), 7 days (n = 4), or 14 days (n = 4). Proteomic analysis with isotope-coded affinity tags and multidimensional liquid chromatography followed by tandem mass spectrometry was performed on the venous stenosis and control vessels. Expression of proteins was further confirmed by Western blot analysis. The blood urea nitrogen (BUN) and creatinine levels were determined before renal artery embolization and at the time of graft placement.

RESULTS

At graft placement, mean BUN and creatinine levels were significantly higher than before embolization (P < .05). Six proteins were identified that were common to all four animals at the same time point. Five proteins (alpha-fetoprotein, fetuin A, macrophage migration inhibitory factor, pyruvate dehydrogenase E1 component, and lactoferrin) were upregulated and one protein (decorin) was downregulated. Expression of macrophage migration inhibitory factor, alpha-fetoprotein, and lactoferrin was further validated with Western blotting. By day 14, lactoferrin and fetuin-A expression were increased significantly in early venous stenosis formation.

CONCLUSIONS

Significantly increased expression of lactoferrin and fetuin-A were observed in early venous stenosis by day 14. Understanding the role of lactoferrin and fetuin-A in hemodialysis vascular access failure could help in improving outcomes in patients undergoing hemodialysis.

Decorin is a secreted protein associated with obesity and type 2 diabetes

OBJECTIVE

To characterize the expression of the small leucine-rich glycoprotein decorin in adipose tissue.

DESIGN

Real-time PCR was used to measure decorin gene expression in adipose tissue from normal glucose tolerant (NGT), impaired glucose tolerant and type 2 diabetic (T2D) Psammomys obesus. Adipose tissue was fractionated to determine which cells were responsible for decorin expression. The location of decorin protein expression in adipose tissue was determined using immunohistochemistry. Real-time PCR was used to measure decorin mRNA levels in human adipose tissue from 16 insulin-sensitive, 16 insulin-resistant and 6 T2D human subjects. Circulating plasma decorin concentrations were measured by enzyme-linked immunosorbent assay in 145 NGT and 141 T2D human individuals from a large-scale epidemiological study in Mauritius.

RESULTS

Decorin mRNA was found to be highly expressed in adipose tissue, and decorin gene expression was significantly higher in visceral than that in subcutaneous adipose tissue depots in both P. obesus and human subjects (P=0.002 and P=0.001, respectively). Decorin mRNA was predominantly expressed by stromal/vascular cells of adipose tissue, and decorin protein in adipose tissue was primarily detected adjacent to blood vessels. Circulating plasma decorin levels in humans were elevated by 12% in T2D (P=0.049) compared to NGT subjects. There was a significant independent correlation between plasma decorin levels and waist-to-hip ratio (WHR, P=0.024). In male subjects, plasma decorin levels were significantly correlated with WHR (P=0.006), and fasting and 2-h glucose levels in an oral glucose tolerance test (P=0.027 and P=0.001, respectively).

CONCLUSIONS

Decorin expression in adipose tissue was markedly upregulated in the obese state and may therefore play a role in adipose tissue homeostasis or in pathophysiology associated with obesity.

Decorin regulates endothelial cell motility on collagen I through activation of insulin-like growth factor I receptor and modulation of alpha2beta1 integrin activity

The proteoglycan decorin is expressed by sprouting but not quiescent endothelial cells, and angiogenesis is dysregulated in its absence. Previously, we have shown that decorin core protein can bind to and activate insulin-like growth factor-I receptor (IGF-IR) in endothelial cells. In this study, we show that decorin promotes alpha2beta1 integrin-dependent endothelial cell adhesion and migration on fibrillar collagen type I. We provide evidence that decorin modulates cell-matrix interaction in this context by stimulating cytoskeletal and focal adhesion reorganization through activation of the IGF-IR and the small GTPase Rac. Further, the glycosaminoglycan moiety of decorin interacts with alpha2beta1, but not alpha1beta1 integrin, at a site distinct from the collagen I-binding A-domain, to allosterically modulate collagen I-binding activity of the integrin. We propose that induction of decorin expression in angiogenic, as opposed to quiescent, endothelial cells promotes a motile phenotype in an interstitial collagen I-rich environment by both signaling through IGF-IR and influencing alpha2beta1 integrin activity.

Differential expression of decorin by human malignant and benign vascular tumors

An increasing amount of evidence indicates that a small extracellular chondroitin/dermatan sulfate proteoglycan, decorin, is indirectly involved in angiogenesis. Given that angiogenesis is a sine qua non for tumor growth and progression, we attempted to examine whether human malignant vascular tumors differ from human benign vascular tumors in terms of their decorin expression and synthesis. CD31 immunostaining demonstrated that the human malignant vascular tumors Kaposi's sarcoma and angiosarcoma were filled with capillary-like structures, whereas in benign cavernous and capillary hemangiomas, blood vessels were not as abundantly present. By utilizing in situ hybridization and immunocytochemical assays for decorin, we showed that there was no detectable decorin mRNA expression or immunoreactivity within the tumor mass in the Kaposi's sarcoma or angiosarcoma group. Instead, decorin was expressed in the connective tissue stroma lining the sarcoma tissue. In contrast to sarcomas, in hemangiomas, decorin mRNA expression and immunoreactivity were observed also within the tumor mass, particularly in the connective tissue stroma surrounding the clusters of intratumoral blood vessels. Finally, distribution of type I collagen was found to be similar to that of decorin in these tumor tissues. Our findings can be explained with different states of angiogenesis in dissimilar growths. In sarcomas, angiogenesis is extremely powerful, whereas in hemangiomas, angiogenesis has ceased. Thus, decorin is likely to possess a suppressive effect on human tumor angiogenesis in vivo, as previously described by studies using different experimental models. Decorin certainly provides a usable biomarker for distinguishing between benign and malignant vascular tumors in patients.

Bioactive glass-derived hydroxyapatite-coating promotes granulation tissue growth in subcutaneous cellulose implants in rats

Granulation tissue was induced in hydroxyapatite-coated cellulose sponges with subcutaneous implantation in rats. A massive inflammatory reaction with an intense foreign body reaction and an increased invasion of fibrovascular tissue was observed by days 1-3 post-operation, whereas tissue growth into the uncoated control implants was much slower and took place mainly on their surfaces. The foreign body reaction in apatite-coated sponges declined after post-operative day 14, and no obvious differences were seen between the two cellulose sponges from 1 month up to 1 year after implantation. The apatite-coated implants attracted macrophages and fibroblasts, and favored angiogenesis. The excessive connective tissue formation was histologically normal, synthesized the major extracellular matrix molecules in a normal ratio and did not seem to disturb the animals in any way. These results warrant further investigations on clinical applicability of hydroxyapatite-coated cellulose sponges, when fast proliferation of connective tissue is desirable.

Ectopic decorin expression up-regulates VEGF expression in mouse cerebral endothelial cells via activation of the transcription factors Sp1, HIF1alpha, and Stat3

We demonstrate that a proteoglycan decorin (DCN) up-regulates the vascular endothelial growth factor (VEGF) expression with activation of VEGF regulating transcription factors Sp1, hypoxia-inducible factor 1alpha (HIF1alpha), and signal transducer and activator of transcription 3 (Stat3) via epidermal growth factor receptor (EGFR), mitogen-activated protein kinase extracellular signal-regulated kinase 1/2 (ERK1/2), and protein kinase B (AKT) pathways in DCN transfected mouse cerebral endothelial (MCE) cells. Treatment with pharmacological inhibitors and small interfering RNAs reveal that induction and activation of Sp1, HIF1alpha, and Stat3 facilitate their nuclear localization and binding to their specific motifs of the VEGF promoter and induce VEGF expression via two independent pathways, DCN/EGFR/phosphoinositide-3 kinase/AKT and DCN/EGFR/ERK1/2, respectively, in DCN synthesizing MCE cells. The cell type specific glycosylation protects Sp1 and HIF1alpha from proteosome degradation and plays an important and novel role in the regulation of VEGF in DCN transfected MCE cells. Induction of gelatinases (matrix metalloproteinase 2 and 9), the serine protease tissue plasminogen activator and plasmin by DCN transfection in MCE cells leads to extracellular proteolysis and to release of matrix-bound VEGF and activation of angiogenesis. In this study, we demonstrate that two independent downstream signal pathways, DCN/EGFR/ERK1/2 and DCN/EGFR/phosphoinositide-3 kinase/AKT, mediate up-regulation and activation of transcription factors of VEGF such as HIF1alpha, Stat3, and Sp1 and increase VEGF transcription and angiogenesis in MCE cells.

Vascular endocan is preferentially expressed in tumor endothelium

Endothelial cell phenotypes are differentially regulated between different sites of the vascular tree. We tested the hypothesis that endocan, a novel soluble dermatan sulfate proteoglycan, is differentially expressed in the intact endothelium and that site-specific expression is mediated by signals in the local microenvironment. Using a combination of Northern blot analyses, Taqman RT-PCR, and in situ hybridizations, endocan was shown to be preferentially expressed in the endothelial lining of tumor xenografts, including human non-small cell lung cancer, rat glioma, and human renal cell carcinoma. In contrast, endocan mRNA was expressed at low levels in embryos between E4.5 and E18.5. Under in vitro conditions, endocan expression in human umbilical vein endothelial cells (HUVEC) was upregulated by tumor cell-conditioned medium, an effect that was inhibited by the addition of neutralizing antibody to vascular endothelial growth factor (VEGF). Moreover, treatment of HUVEC with VEGF resulted in a dose- and time-dependent increase in endocan mRNA. The results suggest that endocan is preferentially expressed in tumor endothelium in vivo and that its expression is regulated by tumor-derived factors.

Tissue inhibitor of metalloproteinases 4 (TIMP4) is involved in inflammatory processes of human cardiovascular pathology

Tissue inhibitors of matrix metalloproteinases (TIMPs) comprise a family of four members, of which TIMP4 is characterized by being primarily restricted to cardiovascular structures. We demonstrate with immunohistochemical analysis of healthy human tissue that TIMP4 is present in medial smooth muscle cells and adventitial capillaries of arteries as well as in cardiomyocytes. Animal studies have suggested a role for TIMP4 in several inflammatory diseases and cardiovascular pathologies. We therefore examined whether TIMP4 is involved in human inflammatory cardiovascular disorders, specifically atherosclerosis, giant cell arteritis and chronic rejection of heart allografts. TIMP4 was most clearly visible in cardiovascular tissue areas populated by abundant inflammatory cells, mainly macrophages and CD3+ T cells. Using western blotting and immunocytochemistry, human blood derived lymphocytes, monocytes/macrophages and mast cells were shown to produce TIMP4. In advanced atherosclerotic lesions, TIMP4 was detected around necrotic lipid cores, whereas TIMP3 and caspase 3 resided within and around the core regions, indicating different roles for TIMP3 and TIMP4 in inflammation-induced apoptosis and in matrix turnover. In conclusion, the data demonstrate upregulation of TIMP4 in human cardiovascular disorders exhibiting inflammation, suggesting its future use as a novel systemic marker for vascular inflammation.

A role for decorin in cutaneous wound healing and angiogenesis

Decorin is known to influence tissue tensile strength and cellular phenotype. Therefore, decorin is likely to have an impact on tissue repair, including cutaneous wound healing. In this study, cutaneous healing of both excisional and incisional full-thickness dermal wounds was studied in decorin-deficient (Dcn(-/-)) animals. A statistically significant delay in excisional wound healing in the Dcn(-/-) mice occurred at 4 and 10 days postwounding and, in incisional wounds at 4, 10, and 18 days when compared with wild-type (Dcn(-/-)) controls. Fibrovascular invasion into polyvinylalcohol sponges was significantly increased by day 18 in Dcn(-/-) mice relative to Dcn(+/+) mice. The 18-day sponge implants in the Dcn(-/-) mice showed a marked accumulation of biglycan when compared with the corresponding implants in Dcn(+/+) mice. Thus, regulated production of decorin may serve as an excellent therapeutic approach for modifying impaired wound healing and harmful foreign body reactions.

Upregulated genes in sporadic, idiopathic pulmonary arterial hypertension

Background

To elucidate further the pathogenesis of sporadic, idiopathic pulmonary arterial hypertension (IPAH) and identify potential therapeutic avenues, differential gene expression in IPAH was examined by suppression subtractive hybridisation (SSH).

Methods

Peripheral lung samples were obtained immediately after removal from patients undergoing lung transplant for IPAH without familial disease, and control tissues consisted of similarly sampled pieces of donor lungs not utilised during transplantation. Pools of lung mRNA from IPAH cases containing plexiform lesions and normal donor lungs were used to generate the tester and driver cDNA libraries, respectively. A subtracted IPAH cDNA library was made by SSH. Clones isolated from this subtracted library were examined for up regulated expression in IPAH using dot blot arrays of positive colony PCR products using both pooled cDNA libraries as probes. Clones verified as being upregulated were sequenced. For two genes the increase in expression was verified by northern blotting and data analysed using Student's unpaired two-tailed t-test.

Results

We present preliminary findings concerning candidate genes upregulated in IPAH. Twenty-seven upregulated genes were identified out of 192 clones examined. Upregulation in individual cases of IPAH was shown by northern blot for tissue inhibitor of metalloproteinase-3 and decorin (P < 0.01) compared with the housekeeping gene glyceraldehydes-3-phosphate dehydrogenase.

Conclusion

Four of the up regulated genes, magic roundabout, hevin, thrombomodulin and sucrose non-fermenting protein-related kinase-1 are expressed specifically by endothelial cells and one, muscleblind-1, by muscle cells, suggesting that they may be associated with plexiform lesions and hypertrophic arterial wall remodelling, respectively.

Colocalization of the collagen-binding proteoglycans decorin, biglycan, fibromodulin and lumican with different cells in human gingiva

BACKGROUND AND OBJECTIVE

Decorin, biglycan, fibromodulin and lumican are structurally related molecules that belong to the family of small leucine-rich proteoglycans (SLRPs). These SLRPs are secreted extracellular matrix molecules that interact with type I collagen and regulate collagen fibrillogenesis. They may also modulate cell functions that are important in maintenance of connective tissue structure. The aim of this study was to localize decorin, biglycan, fibromodulin and lumican in human gingiva.

METHODS

Localization of decorin and its proform (prodecorin), biglycan, fibromodulin and lumican and mature and proform of type I collagen was studied by immunohistochemical staining of frozen tissue sections from healthy human attached gingiva. Double immunostaining with anti-SLRP or anti-type I procollagen antibodies and specific markers for different connective tissue cells was used to study association of these molecules with cells.

RESULTS

The mature and proforms of decorin and collagen and biglycan, fibromodulin and lumican showed distinct localization in the extracellular matrix, where they associated with type I collagen fiber bundles. Prodecorin also localized to the epithelial basement membrane zone. Fibroblasts, myofibroblasts, endothelial cells and pericytes showed immunoreactivity for procollagen, prodecorin, biglycan and fibromodulin, whereas lumican associated with fibroblasts and myofibroblasts only. Biglycan and fibromodulin were also associated with macrophages. Basal epithelial cells of the gingival epithelium showed immunoreactivity for biglycan, fibromodulin and lumican.

CONCLUSIONS

Decorin, biglycan, fibromodulin and lumican associate with type I collagen and may collaborate to regulate collagen fibrillogenesis in human gingiva. Each of the SLRPs showed a distinct association with different connective tissue cells, suggesting that the cells produce these molecules and/or that the cells interact with them. Localization of biglycan, fibromodulin and lumican at the epithelial cells suggests novel functions for these SLRPs in human gingival epithelium.

Characterization of chondroitin/dermatan sulfate proteoglycans synthesized by bovine retinal pericytes in culture

Pericytes associate with the outside of endothelial cells in microvessels. Previous studies have shown that these cells synthesize glycosaminoglycans (GAGs) but the nature of the core proteins to which these GAGs are attached is unknown. In the present study, cultured bovine retinal pericytes were metabolically labeled with [(3)H]glucosamine, [(35)S]sodium sulfate or (35)S-labeled amino acids and the proteoglycans synthesized by these cells were purified by DEAE-Sephacel ion exchange and molecular sieve Sepharose CL-4B chromatography. Separated proteoglycans were digested with papain, heparitinase or chondroitin ABC lyase and the GAGs characterized by Sepharose CL-6B chromatography. Proteoglycans were also assessed by sodium dodecyl sulfate polyacrylamide gel electrophoresis before and after digestion with chondroitin ABC lyase. Pericytes predominantly synthesize and secrete chondroitin or dermatan sulfate proteoglycans (CS/DS PGs) rather than heparan sulfate proteoglycans (HSPGs). Two subclasses of CS/DS PGs are synthesized by pericytes; one is a high M(r) subclass with high charge density. This subclass eluted at the void volume of a Sepharose CL-4B molecular sieve column, was susceptible to chondroitin ABC lyase, and contained core proteins of ca. 550 and 450 kD which were recognized by antibody to versican. The other major subclass eluted at a K(av) ca. 0.45 on a Sepharose CL-4B molecular sieve column, was susceptible to chondroitin ABC lyase, and contained core proteins recognized by antibodies to either biglycan or decorin that separated as a broad band of ca. 50 kDa in SDS-PAGE. A small amount of HSPG was also synthesized by these cells and could be separated from the CS/DS PGs by DEAE-Sephacel chromatography using a linear gradient of 0.1-0.7 M NaCl. Release of GAG chains by protease digestion indicated that the length of GAG chains was approximately M(r) 45000 in biglycan and decorin, approximately M(r) 48000 in the small amount of HSPGs and approximately M(r) 66000 in versican. These proteoglycans resemble those synthesized by vascular smooth muscle cells but differ markedly from those synthesized by vascular endothelial cells.