Proinflammatory stimuli regulate endothelial hyaluronan expression and CD44/HA-dependent primary adhesion

Orally-administered nanomedicine systems targeting colon inflammation for the treatment of inflammatory bowel disease: latest advances

Inflammatory bowel disease (IBD) is a chronic and idiopathic condition that results in inflammation of the gastrointestinal tract, leading to conditions such as ulcerative colitis and Crohn's disease. Commonly used treatments for IBD include anti-inflammatory drugs, immunosuppressants, and antibiotics. Fecal microbiota transplantation is also being explored as a potential treatment method; however, these drugs may lead to systemic side effects. Oral administration is preferred for IBD treatment, but accurately locating the inflamed area in the colon is challenging due to multiple physiological barriers. Nanoparticle drug delivery systems possess unique physicochemical properties that enable precise delivery to the target site for IBD treatment, exploiting the increased permeability and retention effect of inflamed intestines. The first part of this review comprehensively introduces the pathophysiological environment of IBD, covering the gastrointestinal pH, various enzymes in the pathway, transport time, intestinal mucus, intestinal epithelium, intestinal immune cells, and intestinal microbiota. The second part focuses on the latest advances in the mechanism and strategies of targeted delivery using oral nanoparticle drug delivery systems for colitis-related fields. Finally, we present challenges and potential directions for future IBD treatment with the assistance of nanotechnology.

Binding of different hyaluronan to CD44 mediates distinct cell adhesion dynamics under shear flow

As a known receptor-ligand pair for mediating cell-cell or cell-extracellular matrix adhesions, cluster of differentiation 44 (CD44)-hyaluronan (HA) interactions are not only determined by molecular weight (MW) diversity of HA, but also are regulated by external physical or mechanical factors. However, the coupling effects of HA MW and shear flow are still unclear. Here, we compared the differences between high molecular weight HA (HHA) and low molecular weight HA (LHA) binding to CD44 under varied shear stresses. The results demonstrated that HHA dominated the binding phase but LHA was in favour of the shear resistance phase, respectively, under shear stress range ≤ 1.0 dyne·cm-2 . This difference was attributed to the high binding strength of the CD44-HHA interaction, as well as the optimal distribution matching between both CD44 and HA sides. Activation of the intracellular signal pathway was sensitive to both HA MW and shear flow. Our findings also indicate that only CD44-HHA interaction under shear stress of 0.2 dyne·cm-2 could significantly enhance the clustering of CD44, as well as induce the increase in both CD44 and CD18 expression. The present study offers the basis for further quantification of the features of CD44-HA interactions and their biological functions.

EMD originates from hyaluronan-induced homophilic interactions of CD44 variant-expressing MM cells under shear stress

Extramedullary disease (EMD) is known to be associated with chemoresistance and poor prognosis in multiple myeloma (MM); however, the mechanisms of its development are not fully understood. Elucidating the mechanism of EMD development and its therapeutic targeting would greatly contribute to further improvement of treatment outcome in patients with MM. Here, we show that bone marrow stroma cell-derived hyaluronan (HA) elicits homophilic interactions of MM cells by binding to surface CD44, especially long-stretch variants, under physiological shear stress and generates cell clusters that might develop into EMD. We recapitulated the development of EMD via administration of HA in a syngeneic murine MM model in a CD44-dependent manner. HA-induced MM cell clusters exhibited the specific resistance to proteasome inhibitors (PIs) in vitro and in murine models via γ-secretase-mediated cleavage of the intracellular domains of CD44, which in turn transactivated PI resistance-inducible genes. Treatment of HA-injected mice with anti-CD44 antibody or γ-secretase inhibitors readily suppressed the development of EMD from transplanted MM cells and significantly prolonged the survival of recipients by overcoming PI resistance. The HA-CD44 axis represents a novel pathway to trigger EMD development and could be a target of the prediction, prevention, and treatment of EMD in patients with MM.

Oral hymecromone decreases hyaluronan in human study participants

BACKGROUNDHyaluronan (HA), an extracellular matrix glycosaminoglycan, has been implicated in the pathophysiology of COVID-19 infection, pulmonary hypertension, pulmonary fibrosis, and other diseases, but is not targeted by any approved drugs. We asked whether hymecromone (4-methylumbelliferone [4-MU]), an oral drug approved in Europe for biliary spasm treatment that also inhibits HA in vitro and in animal models, could be repurposed as an inhibitor of HA synthesis in humans.METHODSWe conducted an open-label, single-center, dose-response study of hymecromone in healthy adults. Subjects received hymecromone at 1200 (n = 8), 2400 (n = 9), or 3600 (n = 9) mg/d divided into 3 doses daily, administered orally for 4 days. We assessed safety and tolerability of hymecromone and analyzed HA, 4-MU, and 4-methylumbelliferyl glucuronide (4-MUG; the main metabolite of 4-MU) concentrations in sputum and serum.RESULTSHymecromone was well tolerated up to doses of 3600 mg/d. Both sputum and serum drug concentrations increased in a dose-dependent manner, indicating that higher doses lead to greater exposures. Across all dose arms combined, we observed a significant decrease in sputum HA from baseline after 4 days of treatment. We also observed a decrease in serum HA. Additionally, higher baseline sputum HA levels were associated with a greater decrease in sputum HA.CONCLUSIONAfter 4 days of exposure to oral hymecromone, healthy human subjects experienced a significant reduction in sputum HA levels, indicating this oral therapy may have potential in pulmonary diseases where HA is implicated in pathogenesis.TRIAL REGISTRATIONClinicalTrials.gov NCT02780752.FUNDINGStanford Medicine Catalyst, Stanford SPARK, Stanford Innovative Medicines Accelerator program, NIH training grants 5T32AI052073-14 and T32HL129970.

Skin inflammation activates intestinal stromal fibroblasts and promotes colitis

Inflammatory disorders of the skin are frequently associated with inflammatory bowel diseases (IBDs). To explore mechanisms by which these organs communicate, we performed single-cell RNA-Seq analysis on fibroblasts from humans and mice with IBD. This analysis revealed that intestinal inflammation promoted differentiation of a subset of intestinal stromal fibroblasts into preadipocytes with innate antimicrobial host defense activity. Furthermore, this process of reactive adipogenesis was exacerbated if mouse skin was inflamed as a result of skin wounding or infection. Since hyaluronan (HA) catabolism is activated during skin injury and fibroblast-to-adipocyte differentiation is dependent on HA, we tested the hypothesis that HA fragments could alter colon fibroblast function by targeted expression of human hyaluronidase-1 in basal keratinocytes from mouse skin. Hyaluronidase expression in the skin activated intestinal stromal fibroblasts, altered the fecal microbiome, and promoted excessive reactive adipogenesis and increased inflammation in the colon after challenge with dextran sodium sulfate. The response to digested HA was dependent on expression of TLR4 by preadipocytes. Collectively, these results suggest that the association between skin inflammation and IBD may be due to recognition by mesenchymal fibroblasts in the colon of HA released during inflammation of the skin.

Recent advances and prospects of hyaluronan as a multifunctional therapeutic system

Hyaluronan (HA) is a naturally occurring non-sulfated glycosaminoglycan (GAG), cell-surface-associated biopolymer and is the key component of tissue extracellular matrix (ECM). Along with remarkable physicochemical properties, HA also has multifaceted biological effects that include but not limited to ECM organization, immunomodulation, and various cellular processes. Environmental cues such as tissue injury, infection or cancer change downstream signaling functionalities of HA. Unlike native HA, the fragments of HA have diversified effects on inflammation, cancer, fibrosis, angiogenesis and autoimmune response. In this review, we aim to discuss HA as a therapeutic delivery system development process, source, biophysical-chemical properties, and associated biological pathways (especially via cell surface receptors) of native and fragmented HA. We also tried to address an overview of the potential role of HA (native HA vs fragments) in the modulation of inflammation, immune response and various cancer targeting delivery applications. This review will also highlight the HA based therapeutic systems, medical devices and future perspectives of various biomedical applications were discussed in detail.

Delivering Antisense Oligonucleotides across the Blood-Brain Barrier by Tumor Cell-Derived Small Apoptotic Bodies

The blood-brain barrier (BBB) is the most restrictive and complicated barrier that keeps most biomolecules and drugs from the brain. An efficient brain delivery strategy is urgently needed for the treatment of brain diseases. Based on the studies of brain-targeting extracellular vesicles (EVs), the potential of using small apoptotic bodies (sABs) from brain metastatic cancer cells for brain-targeting drug delivery is explored. It is found that anti-TNF-α antisense oligonucleotide (ASO) combined with cationic konjac glucomannan (cKGM) can be successfully loaded into sABs via a transfection/apoptosis induction process and that the sABs generated by B16F10 cells have an extraordinarily high brain delivery efficiency. Further studies suggest that ASO-loaded sABs (sCABs) are transcytosed by b. End3 (brain microvascular endothelial cells, BMECs) to penetrate the BBB, which is mediated by CD44v6, and eventually taken up by microglial cells in the brain. In a Parkinson's disease (PD) mouse model, sCABs dramatically ameliorate PD symptoms via the anti-inflammatory effect of ASO. This study suggests that sABs from brain metastatic cancer cells are excellent carriers for brain-targeted delivery, as they have not only an extraordinary delivery efficiency but also a much higher scale-up production potential than other EVs.

The Effects of Resuscitative Fluid Therapy on the Endothelial Surface Layer

The goal of resuscitative fluid therapy is to rapidly expand circulating blood volume in order to restore tissue perfusion. Although this therapy often serves to improve macrohemodynamic parameters, it can be associated with adverse effects on the microcirculation and endothelium. The endothelial surface layer (ESL) provides a protective barrier over the endothelium and is important for regulating transvascular fluid movement, vasomotor tone, coagulation, and inflammation. Shedding or thinning of the ESL can promote interstitial edema and inflammation and may cause microcirculatory dysfunction. The pathophysiologic perturbations of critical illness and rapid, large-volume fluid therapy both cause shedding or thinning of the ESL. Research suggests that restricting the volume of crystalloid, or “clear” fluid, may preserve some ESL integrity and improve outcome based on animal experimental models and preliminary clinical trials in people. This narrative review critically evaluates the evidence for the detrimental effects of resuscitative fluid therapy on the ESL and provides suggestions for future research directions in this field.

Dendritic cell entry to lymphatic capillaries is orchestrated by CD44 and the hyaluronan glycocalyx

CD44 anchors the hyaluronan glycocalyx on migrating dendritic cells to permit docking to the endothelial receptor LYVE-1, thus orchestrating lymphatic trafficking through modulating glycocalyx density.

DCs play a vital role in immunity by conveying antigens from peripheral tissues to draining lymph nodes, through afferent lymphatic vessels. Critical to the process is initial docking to the lymphatic endothelial receptor LYVE-1 via its ligand hyaluronan on the DC surface. How this relatively weak binding polymer is configured for specific adhesion to LYVE-1, however, is unknown. Here, we show that hyaluronan is anchored and spatially organized into a 400–500 nm dense glycocalyx by the leukocyte receptor CD44. Using gene knockout and by modulating CD44-hyaluronan interactions with monoclonal antibodies in vitro and in a mouse model of oxazolone-induced skin inflammation, we demonstrate that CD44 is required for DC adhesion and transmigration across lymphatic endothelium. In addition, we present evidence that CD44 can dynamically control the density of the hyaluronan glycocalyx, regulating the efficiency of DC trafficking to lymph nodes. Our findings define a previously unrecognized role for CD44 in lymphatic trafficking and highlight the importance of the CD44:HA:LYVE-1 axis in its regulation.

The glycocalyx: a central regulator of vascular function

The endothelial glycocalyx is a specialized extracellular matrix that covers the apical side of vascular endothelial cells, projecting into the lumen of blood vessels. The composition of the glycocalyx has been studied in great detail, and it is known to be composed of a mixture of proteoglycans, glycosaminoglycans, and glycoproteins. Although this structure was once believed to be a passive physical barrier, it is now recognized as a multifunctional and dynamic structure that participates in many vascular processes, including but not limited to vascular permeability, inflammation, thrombosis, mechanotransduction, and cytokine signaling. Because of its participation in many physiological and pathophysiological states, comprehensive knowledge of the glycocalyx will aid future vascular biologists in their research. With that in mind, this review discusses the biochemical structure of the glycocalyx and its function in many vascular physiological processes. We also briefly review a more recent discovery in glycocalyx biology, the placental glycocalyx.

Hyaluronan and Its Receptors as Regulatory Molecules of the Endothelial Interface

On the surface of endothelial cells (ECs) lies the glycocalyx, a barrier of polysaccharides that isolates the ECs from the blood. The role of the glycocalyx is dynamic and complex, thanks to not only its structure, but its vast number of components, one being hyaluronan (HA). HA is a critical component of the glycocalyx, having been found to have a wide variety of functions depending on its molecular weight, its modification, and receptor-ligand interactions. As HA and viscous blood are in constant contact, HA can transmit mechanosensory information directly to the cytoskeleton of the ECs. The degradation and synthesis of HA directly alters the permeability of the EC barrier; HA modulation not only alters the physical barrier but also can signal the initiation of other pathways. EC proliferation and angiogenesis are in part regulated by HA fragmentation, HA-dependent receptor binding, and downstream signals. The interaction between the CD44 receptor and HA is a driving force behind leukocyte recruitment, but each class of leukocyte still interacts with HA in unique ways during inflammation. HA regulates a diverse repertoire of EC functions.

Location, Location, Location: How Vascular Specialization Influences Hematopoietic Fates During Development

During embryonic development, sequential waves of hematopoiesis give rise to blood-forming cells with diverse lineage potentials and self-renewal properties. This process must accomplish two important yet divergent goals: the rapid generation of differentiated blood cells to meet the needs of the developing embryo and the production of a reservoir of hematopoietic stem cells to provide for life-long hematopoiesis in the adult. Vascular beds in distinct anatomical sites of extraembryonic tissues and the embryo proper provide the necessary conditions to support these divergent objectives, suggesting a critical role for specialized vascular niche cells in regulating disparate blood cell fates during development. In this review, we will examine the current understanding of how organ- and stage-specific vascular niche specialization contributes to the development of the hematopoietic system.

Traditional Chinese Medicine Regulating Lymphangiogenesis: A Literature Review

Lymphatic vessels, as an important part of the lymphatic system, form a fine vascular system in humans and play an important role in regulating fluid homeostasis, assisting immune surveillance and transporting dietary lipids. Dysfunction of lymphatic vessels can cause many diseases, including cancer, cardiovascular diseases, lymphedema, inflammation, rheumatoid arthritis. Research on lymphangiogenesis has become increasingly important over the last few decades. Nevertheless, the explicit role of regulating lymphangiogenesis in preventing and treating diseases remains unclear owing to the lack of a deeper understanding of the cellular and molecular pathways of the specific and tissue-specific changes in lymphangiopathy. TCM, consisting of compound extracted from TCM, Injections of single TCM and formula, is an important complementary strategy for treating disease in China. Lots of valuable traditional Chinese medicines are used as substitutes or supplements in western countries. As one of the main natural resources, these TCM are widely used in new drug research and development in Asia. Moreover, as a historical and cultural heritage, TCM has been widely applied to clinical research on lymphangiogenesis leveraging new technologies recently. Available studies show that TCM has an explicit effect on the regulation of lymphatic regeneration. This review aims to clarify the function and mechanisms, especially the inhibitory effect of TCM in facilitating and inhibiting lymphatic regeneration.

Chitinase-3 like-protein-1 function and its role in diseases

Non-enzymatic chitinase-3 like-protein-1 (CHI3L1) belongs to glycoside hydrolase family 18. It binds to chitin, heparin, and hyaluronic acid, and is regulated by extracellular matrix changes, cytokines, growth factors, drugs, and stress. CHI3L1 is synthesized and secreted by a multitude of cells including macrophages, neutrophils, synoviocytes, chondrocytes, fibroblast-like cells, smooth muscle cells, and tumor cells. It plays a major role in tissue injury, inflammation, tissue repair, and remodeling responses. CHI3L1 has been strongly associated with diseases including asthma, arthritis, sepsis, diabetes, liver fibrosis, and coronary artery disease. Moreover, following its initial identification in the culture supernatant of the MG63 osteosarcoma cell line, CHI3L1 has been shown to be overexpressed in a wealth of both human cancers and animal tumor models. To date, interleukin-13 receptor subunit alpha-2, transmembrane protein 219, galectin-3, chemo-attractant receptor-homologous 2, and CD44 have been identified as CHI3L1 receptors. CHI3L1 signaling plays a critical role in cancer cell growth, proliferation, invasion, metastasis, angiogenesis, activation of tumor-associated macrophages, and Th2 polarization of CD4⁺ T cells. Interestingly, CHI3L1-based targeted therapy has been increasingly applied to the treatment of tumors including glioma and colon cancer as well as rheumatoid arthritis. This review summarizes the potential roles and mechanisms of CHI3L1 in oncogenesis and disease pathogenesis, then posits investigational strategies for targeted therapies.

Involvement of hyaluronan and CD44 in cancer and viral infections

Hyaluronan and its major receptor CD44 are ubiquitously distributed. They have important structural as well as signaling roles, regulating tissue homeostasis, and their expression levels are tightly regulated. In addition to signaling initiated by the interaction of the intracellular domain of CD44 with cytoplasmic signaling molecules, CD44 has important roles as a co-receptor for different types of receptors of growth factors and cytokines. Dysregulation of hyaluronan-CD44 interactions is seen in diseases, such as inflammation and cancer. In the present communication, we discuss the mechanism of hyaluronan-induced signaling via CD44, as well as the involvement of hyaluronan-engaged CD44 in malignancies and in viral infections.

Decreased erythrocyte CD44 and CD58 expression link e-waste Pb toxicity to changes in erythrocyte immunity in preschool children

Lead (Pb) toxicity damages blood cells and disturbs the immune micro-environment. When Pb enters the circulatory system, >95% of Pb accumulates in erythrocytes. We therefore conducted this study to explore the long-term effect of Pb exposure on expression of erythrocyte adhesion molecules (CD44 and CD58) and related downstream cytokine concentrations. We enrolled a total of 267 preschool children, 2-7 years of age, from Guiyu (e-waste-exposed group, n = 132) and Haojiang (reference group, n = 135) in November and December 2015. We measured child blood Pb, biomarkers including erythrocyte CD44 and CD58, erythrocyte count, leukocyte count and inflammatory cytokines (IL-1β, IL-12p70 and IFN-γ), and calculated erythrocyte Pb levels. Regression model demonstrated that higher erythrocyte Pb was associated with lower CD44 and CD58. Compared to low erythrocyte Pb levels (quartile 1), high erythrocyte Pb levels (quartile 4) were related to lower levels of erythrocyte CD44 and CD58. Elevated blood Pb correlated with higher IL-12p70 and IFN-γ, and lower IL-2. The mediation effect of erythrocyte CD44 on the relationship of erythrocyte Pb with IL-1β and IL-12p70 was significant, and the effect of erythrocyte Pb on IFN-γ was mediated by erythrocyte CD58. The data provides novel translational insight into the relationship between elevated Pb exposure and the change of erythrocyte immunity and downstream cytokine secretion in preschool children.

Damage-associated molecular patterns in inflammatory bowel disease: From biomarkers to therapeutic targets

The chronic inflammatory process underlying inflammatory bowel disease (IBD), comprising Crohn’s disease and ulcerative colitis, derives from the interplay of several components in a genetically susceptible host. These components include environmental elements and gut microbiota a dysbiosis. For decades, immune abnormalities have been investigated as critically important in IBD pathogenesis, and attempts to develop effective therapies have predominantly targeted the immune system. Nevertheless, immune events represent only one of the constituents contributing to IBD pathogenesis within the context of the complex cellular and molecular network underlying chronic intestinal inflammation. These factors need to be appreciated within the milieu of non-immune components. Damage-associated molecular patterns (DAMPs), which are essentially endogenous stress proteins expressed or released as a result of cell or tissue damage, have been shown to act as direct pro-inflammatory mediators. Excessive or persistent signalling mediated by such molecules can underlie several chronic inflammatory disorders, including IBD. The release of endogenous DAMPs amplifies the inflammatory response driven by immune and non-immune cells and promotes epigenetic reprogramming in IBD. The effects determine pathologic changes, which may sustain chronic intestinal inflammation and also underlie specific disease phenotypes. In addition to highlighting the potential use of DAMPs such as calprotectin as biomarkers, research on DAMPs may reveal novel mechanistic associations in IBD pathogenesis and is expected to uncover putative therapeutic targets.

Hyaluronidase inhibits reactive adipogenesis and inflammation of colon and skin

In this study we evaluated the role of hyaluronan (HA) in reactive adipogenesis, a local expansion of preadipocytes that provides host defense by release of antimicrobial peptides. We observed that HA accumulated during maturation of adipocytes in vitro and was associated with increased expression of preadipocyte factor 1, zinc finger protein 423, and early B cell factor 1. Although HA is normally abundant in the extracellular matrix, a further increase in HA staining occurred in mice at sites of reactive adipogenesis following injury of colon by dextran sodium sulfate or injury of skin from infection with Staphylococcus aureus. HA also abundantly accumulated around adipocytes seen in the colons of patients with inflammatory bowel disease. This HA was necessary for adipocyte maturation because digestion of HA by administration of soluble hyaluronidase or transgenic expression of hyaluronidase 1 inhibited adipogenesis in vitro and in vivo. Furthermore, hyaluronidase also suppressed inflammation of both skin and colon and decreased antimicrobial peptide expression by developing preadipocytes. This resulted in increased bacterial transit across the epithelial barrier despite decreased tissue injury from inflammation. These observations suggest HA plays an important role in reactive adipogenesis and host defense after injury.

Idiopathic pulmonary fibrosis: Epithelial-mesenchymal interactions and emerging therapeutic targets

Idiopathic pulmonary fibrosis (IPF) is a chronic fibrotic disease of the lung that is marked by progressive decline in pulmonary function and ultimately respiratory failure. Genetic and environmental risk factors have been identified that indicate injury to, and dysfunction of the lung epithelium is central to initiating the pathogenic process. Following injury to the lung epithelium, growth factors, matrikines and extracellular matrix driven signaling together activate a variety of repair pathways that lead to inflammatory cell recruitment, fibroblast proliferation and expansion of the extracellular matrix, culminating in tissue fibrosis. This tissue fibrosis then leads to changes in the biochemical and biomechanical properties of the extracellular matrix, which potentiate profibrotic mechanisms through a "feed-forward cycle." This review provides an overview of the interactions of the pathogenic mechanisms of IPF with a focus on epithelial-mesenchymal crosstalk and the extracellular matrix as a therapeutic target for idiopathic pulmonary fibrosis.

The Receptor for Hyaluronan-Mediated Motility (CD168) promotes inflammation and fibrosis after acute lung injury

Acute lung injury results in early inflammation and respiratory distress, and later fibrosis. The glycosaminoglycan hyaluronan (HA) and the Receptor for Hyaluronan-Mediated Motility (RHAMM, CD168) have been implicated in the response to acute lung injury. We hypothesized that, compared to wild type (WT) mice, RHAMM knockout (KO) mice would be protected from, whereas mice with macrophage-specific transgenic overexpression of RHAMM (TG) would have worse inflammation, respiratory distress and fibrosis after intratracheal (IT) bleomycin. Compared to WT mice, 10 days after IT bleomycin, RHAMM KO mice had less weight loss, less increase in respiratory rate, and fewer CD45+ cells in the lung. At day 28, compared to injured WT animals, injured RHAMM KO mice had lower M1 macrophage content, as well as decreased fibrosis as determined by trichrome staining, Ashcroft scores and lung HPO content. Four lines of transgenic mice with selective overexpression of RHAMM in macrophages were generated using the Scavenger Receptor A promoter driving a myc-tagged full length RHAMM cDNA. Baseline expression of RHAMM and CD44 was the same in WT and TG mice. By flow cytometry, TG bone marrow-derived macrophages (BMDM) had increased cell surface RHAMM and myc, but equal CD44 expression. TG BMDM also had 2-fold increases in both chemotaxis to HA and proliferation in fetal bovine serum. In TG mice, increased inflammation after thioglycollate-induced peritonitis was restricted to macrophages and not neutrophils. For lung injury studies, non-transgenic mice given bleomycin had respiratory distress with increased respiratory rates from day 7 to 21. However, TG mice had higher respiratory rates from 4 days after bleomycin and continued to increase respiratory rates up to day 21. At 21 days after IT bleomycin, TG mice had increased lung macrophage accumulation. Lavage HA concentrations were 6-fold higher in injured WT mice, but 30-fold higher in injured TG mice. At 21 days after IT bleomycin, WT mice had developed fibrosis, but TG mice showed exaggerated fibrosis with increased Ashcroft scores and HPO content. We conclude that RHAMM is a critical component of the inflammatory response, respiratory distress and fibrosis after acute lung injury. We speculate that RHAMM is a potential therapeutic target to limit the consequences of acute lung injury.

Single-Molecule Unbinding Forces between the Polysaccharide Hyaluronan and Its Binding Proteins

The extracellular polysaccharide hyaluronan (HA) is ubiquitous in all vertebrate tissues, where its various functions are encoded in the supramolecular complexes and matrices that it forms with HA-binding proteins (hyaladherins). In tissues, these supramolecular architectures are frequently subjected to mechanical stress, yet how this affects the intermolecular bonding is largely unknown. Here, we used a recently developed single-molecule force spectroscopy platform to analyze and compare the mechanical strength of bonds between HA and a panel of hyaladherins from the Link module superfamily, namely the complex of the proteoglycan aggrecan and cartilage link protein, the proteoglycan versican, the inflammation-associated protein TSG-6, the HA receptor for endocytosis (stabilin-2/HARE), and the HA receptor CD44. We find that the resistance to tensile stress for these hyaladherins correlates with the size of the HA-binding domain. The lowest mean rupture forces are observed for members of the type A subgroup (i.e., with the shortest HA-binding domains; TSG-6 and HARE). In contrast, the mechanical stability of the bond formed by aggrecan in complex with cartilage link protein (two members of the type C subgroup, i.e., with the longest HA-binding domains) and HA is equal or even superior to the high affinity streptavidin⋅biotin bond. Implications for the molecular mechanism of unbinding of HA⋅hyaladherin bonds under force are discussed, which underpin the mechanical properties of HA⋅hyaladherin complexes and HA-rich extracellular matrices.

Immune Responses in the Liver

The liver is a key, frontline immune tissue. Ideally positioned to detect pathogens entering the body via the gut, the liver appears designed to detect, capture, and clear bacteria, viruses, and macromolecules. Containing the largest collection of phagocytic cells in the body, this organ is an important barrier between us and the outside world. Importantly, as portal blood also transports a large number of foreign but harmless molecules (e.g., food antigens), the liver's default immune status is anti-inflammatory or immunotolerant; however, under appropriate conditions, the liver is able to mount a rapid and robust immune response. This balance between immunity and tolerance is essential to liver function. Excessive inflammation in the absence of infection leads to sterile liver injury, tissue damage, and remodeling; insufficient immunity allows for chronic infection and cancer. Dynamic interactions between the numerous populations of immune cells in the liver are key to maintaining this balance and overall tissue health.

Degradation of the endothelial glycocalyx is associated with chylomicron leakage in mouse cremaster muscle microcirculation

A thick endothelial glycocalyx contributes to the barrier function of vascular endothelium in macro- and microcirculation. We hypothesised in the current study that diet-induced hyperlipidaemia perturbs the glycocalyx, resulting in decreased dimensions of this layer and increased transendothelial lipoprotein leakage in capillaries. Glycocalyx thickness was measured in mouse cremaster muscle capillaries by intravital microscopy from the distance between flowing red blood cells and the endothelial surface. In control C57BL/6 mice on standard chow, glycocalyx thickness measured 0.58 ± 0.01 (mean ± SEM) μm, and no lipo-proteins were observed in the tissue. After three months administration of an either mild or severe high-fat / high-cholesterol diet (HFC) to C57BL/6 and ApoE3-Leiden mice, circulating large lipoproteins appeared into the subendothelial space in an increasing proportion of cre-master capillaries, and these capillaries displayed reduced glycocalyx dimensions of 0.40 ± 0.02 and 0.30 ± 0.01 μm (C57BL/6 mice), and 0.37 ± 0.01 and 0.28 ± 0.01 μm (ApoE3-Leiden mice), after the mild and severe HFC diet, respectively. The chylomicron nature of the accumulated lipoproteins was confirmed by observations of subendothelial deposition of DiI-labeled chylomicrons in capillaries after inducing acute glycocalyx degradation by heparitinase in normolipidaemic C57BL/6 mice. It is concluded that while under control conditions the endothelial glycocalyx contributes to the vascular barrier against transvascular lipoprotein leakage in the microcirculation, diet-induced hyperlipidaemia reduces the thickness of the glycocalyx, thereby facilitating leakage of chylomicrons across the capillary wall.

CD44 mediates the catch-bond activated rolling of HEPG2Iso epithelial cancer cells on hyaluronan

The attachment of cancer cells to the endothelium is an essential step during metastatic dissemination. The cell surface receptor CD44 is capable of binding to hyaluronan (HA) produced by tumor cells and by cells of the tumor microenvironment, including blood endothelial cells. Here, we investigated the role of CD44 in the interaction between the liver cancer cell line HepG2Iso and HA surfaces. The rolling interaction was quantitatively analyzed using a microfluidic shear force setup. It was found that rolling of the liver cancer cells on HA depends on CD44, which mediates a catch-bond interaction and thus a flow-induced rolling of the cells. Reduction of CD44 expression by means of siRNA, inhibition of the interaction of CD44 with HA by antibody blocking, and treatment with low molecular weight HA inhibited liver cancer cell rolling on HA-coated surfaces. The results not only clearly show the dependency of the shear-induced catch-bond interaction of HepG2Iso cells on CD44 and HA, but also for the first time demonstrate CD44-mediated rolling for epithelium-derived cells that are typically adherent.

E-selectin-mediated rolling facilitates pancreatic cancer cell adhesion to hyaluronic acid

Tumor cell extravasation is a multistep process preceded by cell rolling and arrest on the vessel wall via the formation of specific receptor-ligand bonds. The strength, availability, and number of receptor-ligand bonds regulate the rate by which tumor cells tether, roll, and adhere to vascular walls. Although the mechanics of selectin-mediated rolling have been extensively studied, little is known regarding how tumor cell rolling on selectins facilitates adhesion to a distinct substrate-bound protein with different kinetic properties. By using multicomponent protein patterning and a microfluidic system, we evaluated how E-selectin-dependent rolling modulates hyaluronic acid (HA) adhesion as a function of fluid shear, contact time, and the spacing between E-selectin and HA regions patterned on the substrate. We show that tumor cells rolling on E-selectin were ∼40-fold more likely to bind to HA than nonrolling cells in shear flow. Furthermore, E-selectin-dependent rolling promotes adhesion to HA by both physically slowing cells and enabling them to position proximal to the surface, thereby increasing the on rate of adhesion. A better understanding of tumor cell adhesion under physiologic shear would lead to the development of new diagnostic assays and pave the way to clinical approaches aimed ultimately to halt metastasis.-Shea, D. J., Li, Y. W., Stebe, K. J., Konstantopoulos, K. E-selectin-mediated rolling facilitates pancreatic cancer cell adhesion to hyaluronic acid.

Hyaluronan mediates the adhesion of porcine peripheral blood mononuclear cells to poly (I:C)-treated intestinal cells and modulates their cytokine production

Hyaluronan (HA), a major component of the extracellular matrix (ECM), has been increasingly recognized as a regulator of inflammation. Its role is complex since it has pro- and anti-inflammatory actions by modulating the expression of inflammatory genes, the recruitment of inflammatory cells and the production of inflammatory cytokines, but also by attenuating the course of inflammation and providing protection against tissue damage. Certain viruses and other inflammatory stimuli induce organization of HA into cable-like structures, which may be responsible for leukocyte recruitment and, on the other hand, low molecular weight fragments of HA have been shown to activate various inflammatory responses. The aim of the present study was to analyze the effects of a simulated infection with the viral mimetic Poly (I:C) on HA deposition on different porcine intestinal cells (primary colonic muscular smooth muscle cells (SMC), and epithelial IPEC-J2 and IPI-2I cell lines) and on the recruitment of peripheral blood mononuclear cells (PBMC) to intestinal cell layers. We show that Poly (I:C) treatment induces the formation of an HA-based pericellular matrix coat in muscular SMC and in intestinal epithelial cells (IECs) and that, on differentiated IPEC-J2 cells, HA accumulates in the basolateral membrane. Porcine PBMCs bind to Poly (I:C)-treated cells and this binding is dependent on HA, since the increase in adhesion is abolished by hyaluronidase treatment of the cell layers. A second goal was to study the effect of different molecular weight HA forms on the production of pro-inflammatory cytokines and chemokines (TNF-α, IL-1β and IL-8) by porcine PBMCs. Low molecular weight HA fragments (100-150kDa), in contrast to high molecular weight HA (2500kDa), stimulate the release of these pro-inflammatory mediators by porcine PBMCs. Our results suggest that HA is involved in the inflammatory response against pathogenic insults to the porcine gut.

Versican Deficiency Significantly Reduces Lung Inflammatory Response Induced by Polyinosine-Polycytidylic Acid Stimulation

Viral infection is an exacerbating factor contributing to chronic airway diseases, such as asthma, via mechanisms that are still unclear. Polyinosine-polycytidylic acid (poly(I:C)), a Toll-like receptor 3 (TLR3) agonist used as a mimetic to study viral infection, has been shown to elicit inflammatory responses in lungs and to exacerbate pulmonary allergic reactions in animal models. Previously, we have shown that poly(I:C) stimulates lung fibroblasts to accumulate an extracellular matrix (ECM), enriched in hyaluronan (HA) and its binding partner versican, which promotes monocyte adhesion. In the current study, we aimed to determine the in vivo role of versican in mediating inflammatory responses in poly(I:C)-induced lung inflammation using a tamoxifen-inducible versican-deficient mouse model (Vcan^-/- mice). In C57Bl/6 mice, poly(I:C) instillation significantly increased accumulation of versican and HA, especially in the perivascular and peribronchial regions, which were enriched in infiltrating leukocytes. In contrast, versican-deficient (Vcan^-/-) lungs did not exhibit increases in versican or HA in these regions and had strikingly reduced numbers of leukocytes in the bronchoalveolar lavage fluid and lower expression of inflammatory chemokines and cytokines. Poly(I:C) stimulation of lung fibroblasts isolated from control mice generated HA-enriched cable structures in the ECM, providing a substrate for monocytic cells in vitro, whereas lung fibroblasts from Vcan^-/- mice did not. Moreover, increases in proinflammatory cytokine expression were also greatly attenuated in the Vcan^-/- lung fibroblasts. These findings provide strong evidence that versican is a critical inflammatory mediator during poly(I:C)-induced acute lung injury and, in association with HA, generates an ECM that promotes leukocyte infiltration and adhesion.

A single molecule assay to probe monovalent and multivalent bonds between hyaluronan and its key leukocyte receptor CD44 under force

Glycosaminoglycans (GAGs), a category of linear, anionic polysaccharides, are ubiquitous in the extracellular space, and important extrinsic regulators of cell function. Despite the recognized significance of mechanical stimuli in cellular communication, however, only few single molecule methods are currently available to study how monovalent and multivalent GAG·protein bonds respond to directed mechanical forces. Here, we have devised such a method, by combining purpose-designed surfaces that afford immobilization of GAGs and receptors at controlled nanoscale organizations with single molecule force spectroscopy (SMFS). We apply the method to study the interaction of the GAG polymer hyaluronan (HA) with CD44, its receptor in vascular endothelium. Individual bonds between HA and CD44 are remarkably resistant to rupture under force in comparison to their low binding affinity. Multiple bonds along a single HA chain rupture sequentially and independently under load. We also demonstrate how strong non-covalent bonds, which are versatile for controlled protein and GAG immobilization, can be effectively used as molecular anchors in SMFS. We thus establish a versatile method for analyzing the nanomechanics of GAG·protein interactions at the level of single GAG chains, which provides new molecular-level insight into the role of mechanical forces in the assembly and function of GAG-rich extracellular matrices.

CD44 induced enhancement of phosphatase activity and calcium influx: Modifications of EGR-1 expression and cell proliferation

The purpose of this study was to investigate how CD44 impaired Akt phosphorylation, EGR-1 expression and cell proliferation. E6.1 Jurkat cells, which lack endogenous CD44 expression, were engineered to express CD44. Previously we showed that Akt is hypophosphorylated, EGR-1 expression is reduced and proliferation is impaired in CD44 expressing E6.1 Jurkat cells. The cell cycle was studied using flow cytometry and the role of calcium (Ca²⁺) in Akt phosphorylation and EGR-1 expression was investigated using Western blotting. Phosphatase activity was assessed using a commercially available kit. CD44 expressing cells showed disruption at the G₁ to S transition. Chelation of Ca²⁺ from the culture media impaired Akt phosphorylation and EGR-1 expression in both CD44 expressing cells and the open vector control. Moreover, Ni²⁺ disrupted cell proliferation in both cell types suggesting Ca²⁺ import through calcium release activated calcium channels (CRAC). Staining of cells with fura-2 AM showed significantly higher Ca²⁺ in CD44 expressing cells as compared with the vehicle control. Finally, non-calcium mediated phosphatase activity was significantly greater in CD44 expressing cells. We propose that the enhanced phosphatase activity in the CD44 cells increased the dephosphorylation rate of Akt; at the same time, the increased intracellular concentration of Ca²⁺ in the CD44 cells ensured that the phosphorylation of Akt remains intact albeit at lower concentrations as compared with the vector control. Reduced Akt phosphorylation resulted in lowered expression of EGR-1 and hence, reduced the cell proliferation rate.

Catch bond interaction allows cells to attach to strongly hydrated interfaces

Hyaluronans are a class of glycosaminoglycans that are widespread in the mammalian body and serve a variety of functions. Their most striking characteristic is their pronounced hydrophilicity and their capability to inhibit unspecific adhesion when present at interfaces. Catch-bond interactions are used by the CD44 receptor to interact with this inert material and to roll on the surfaces coated with hyaluronans. In this minireview, the authors discuss the general properties of hyaluronans and the occurrence and relevance of the CD44 catch-bond interaction in the context of hematopoiesis, cancer development, and leukemia.

CD44 increases the efficiency of distant metastasis of breast cancer

Metastasis is the predominant cause of death from cancer yet we have few biomarkers to predict patients at increased risk of metastasis and are unable to effectively treat disseminated disease. Analysis of 448 primary breast tumors determined that expression of the hylauronan receptor CD44 associated with high grade (p = 0.046), ER- (p = 0.001) and PR-negative tumors (p = 0.029), and correlated with increased distant recurrence and reduced disease-free survival in patients with lymph-node positive or large tumors. To determine its functional role in distant metastasis, CD44 was knocked-down in MDA-MB-231 cells using two independent shRNA sequences. Loss of CD44 attenuated tumor cell adhesion to endothelial cells and reduced cell invasion but did not affect proliferation in vitro. To verify the importance of CD44 to post-intravasation events, tumor formation was assessed by quantitative in vivo imaging and post-mortem tissue analysis following an intra-cardiac injection of transfected cells. CD44 knock-down increased survival and decreased overall tumor burden at multiple sites, including the skeleton in vivo. We conclude that elevated CD44 expression on tumour cells within the systemic circulation increases the efficiency of post-intravasation events and distant metastasis in vivo, consistent with its association with increased distant recurrence and reduced disease-free survival in patients.

Role of Hematopoietic Stem Cells in Inflammation of the Pancreas during Diabetes Mellitus

The model of streptozotocin-induced diabetes mellitus in C57Bl/6 mice was employed to study the role of precursors of insulin-producing β-cells, hematopoietic stem cells, and progenitor hematopoietic cells in inflammation. In addition to provoking hyperglycemia, streptozotocin elevated serum levels of IL-1β and hyaluronic acid, induced edema in the pancreatic insular tissue and its infiltration by inflammatory cells (neutrophils, lymphocytes, and macrophages) and fibroblasts. Inflammation in pancreatic islets was accompanied by necrotic processes and decreasing counts of multipotent progenitor β-cells (CD45(-), TER119(-), c-kit-1(-), and Flk-1(-)), oligopotent progenitor β-cells (CD45(-), TER119(-), CD133(+), and CD49f(low)), and insulinproducing β-cells (Pdx1(+)). Pancreatic infl ammation was preceded by elevation of the number of short-term hematopoietic stem cells (Lin-Sca-1(+)c-kit(+)CD34(+)) relative to long-term cells (Lin(-)Sca-1(+)c-kit(+)CD34(-)) in the bone marrow as well as recruitment of hematopoietic stem and progenitor cells into circulation. Transplantation of bone marrow hematopoietic stem and progenitor cells from diabetic C57Bl/6 donor mice to recipient CBA mice with 5-fluorouracilinduced leukopenia accelerated regeneration of granulocytopoiesis in recipient mice.

CD44 promotes the migration of bone marrow-derived mesenchymal stem cells toward glioma

Previous in vivo and in vitro studies have shown that human mesenchymal stem cells (MSCs) exhibit tropism for gliomas. However, the mechanism underlying this directed migration remains unclear. The aim of the present study was to investigate the possible mechanism underlying platelet-derived growth factor-BB (PDGF-BB)-induced chemotactic migration of bone marrow-derived MSCs (BMSCs) toward glioma. Rat glioma C6 cell-conditioned medium was utilized to evaluate the chemotactic response of BMSCs toward glioma using an in vitro migration assay. Recombinant rat PDGF-BB was added to C6 cell-conditioned medium to assess its effect on the tropism of BMSCs. The effect of PDGF-BB on the expression levels of cluster of differentiation (CD)44 in BMSCs was evaluated by reverse transcription-polymerase chain reaction (RT-PCR) and immunofluorescence assays. The results revealed that chemotactic migration was induced in BMSCs by rat glioma C6 cell-conditioned medium, which was enhanced by PDGF-BB treatment in a dose-dependent manner. Furthermore, RT-PCR and immunofluorescence assays showed that CD44 expression was upregulated in BMSCs following treatment with 40 ng/ml PDGF-BB for 12 h. Additionally, 3-h pretreatment with the anti-CD44 neutralizing antibody OX-50 was observed to attenuate the tropism of BMSCs toward glioma in the presence or absence of PDGF-BB. The results of the present study indicate that CD44 mediates the tropism of BMSCs toward glioma, and PDGF-BB promotes the migration of BMSCs toward glioma via the upregulation of CD44 expression in BMSCs. These findings suggest CD44 inhibition may be a potential therapeutic target for the treatment of glioma.

Treatment with the hyaluronic Acid synthesis inhibitor 4-methylumbelliferone suppresses LPS-induced lung inflammation

Exposure to bacterial endotoxins, such as lipopolysaccharide (LPS), can lead to the induction of acute lung injury/acute respiratory distress syndrome (ALI/ARDS). To date, there are no known effective treatments for LPS-induced inflammation. In the current study, we investigated the potential use of the hyaluronic acid (HA) synthesis inhibitor 4-methylumbelliferone (4-MU) on LPS-induced acute lung inflammation. Culturing LPS-activated immune cells with 4-MU led to reduced proliferation, reduced cytokine production, and an increase in apoptosis when compared to untreated cells. Treatment of mice with 4-MU led to protection from LPS-induced lung injury. Specifically, 4-MU treatment led to a reduction in LPS-induced hyaluronic acid synthase (HAS) messenger RNA (mRNA) levels, reduction in lung permeability, and reduction in proinflammatory cytokine production. Taken together, these results suggest that use of 4-MU to target HA production may be an effective treatment for the inflammatory response following exposure to LPS.

Binding of Hyaluronan to the Native Lymphatic Vessel Endothelial Receptor LYVE-1 Is Critically Dependent on Receptor Clustering and Hyaluronan Organization

The lymphatic endothelial receptor LYVE-1 has been implicated in both uptake of hyaluronan (HA) from tissue matrix and in facilitating transit of leukocytes and tumor cells through lymphatic vessels based largely on in vitro studies with recombinant receptor in transfected fibroblasts. Curiously, however, LYVE-1 in lymphatic endothelium displays little if any binding to HA in vitro, and this has led to the conclusion that the native receptor is functionally silenced, a feature that is difficult to reconcile with its proposed in vivo functions. Nonetheless, as we reported recently, LYVE-1 can function as a receptor for HA-encapsulated Group A streptococci and mediate lymphatic dissemination in mice. Here we resolve these paradoxical findings and show that the capacity of LYVE-1 to bind HA is strictly dependent on avidity, demanding appropriate receptor self-association and/or HA multimerization. In particular, we demonstrate the prerequisite of a critical LYVE-1 threshold density and show that HA binding may be elicited in lymphatic endothelium by surface clustering with divalent LYVE-1 mAbs. In addition, we show that cross-linking of biotinylated HA in streptavidin multimers or supramolecular complexes with the inflammation-induced protein TSG-6 enables binding even in the absence of LYVE-1 cross-linking. Finally, we show that endogenous HA on the surface of macrophages can engage LYVE-1, facilitating their adhesion and transit across lymphatic endothelium. These results reveal LYVE-1 as a low affinity receptor tuned to discriminate between different HA configurations through avidity and establish a new mechanistic basis for the functions ascribed to LYVE-1 in matrix HA binding and leukocyte trafficking in vivo.

Hyperglycemia-Induced Changes in Hyaluronan Contribute to Impaired Skin Wound Healing in Diabetes: Review and Perspective

Ulcers and chronic wounds are a particularly common problem in diabetics and are associated with hyperglycemia. In this targeted review, we summarize evidence suggesting that defective wound healing in diabetics is causally linked, at least in part, to hyperglycemia-induced changes in the status of hyaluronan (HA) that resides in the pericellular coat (glycocalyx) of endothelial cells of small cutaneous blood vessels. Potential mechanisms through which exposure to high glucose levels causes a loss of the glycocalyx on the endothelium and accelerates the recruitment of leukocytes, creating a proinflammatory environment, are discussed in detail. Hyperglycemia also affects other cells in the immediate perivascular area, including pericytes and smooth muscle cells, through exposure to increased cytokine levels and through glucose elevations in the interstitial fluid. Possible roles of newly recognized, cross-linked forms of HA, and interactions of a major HA receptor (CD44) with cytokine/growth factor receptors during hyperglycemia, are also discussed.

Roles of Proteoglycans and Glycosaminoglycans in Wound Healing and Fibrosis

A wound is a type of injury that damages living tissues. In this review, we will be referring mainly to healing responses in the organs including skin and the lungs. Fibrosis is a process of dysregulated extracellular matrix (ECM) production that leads to a dense and functionally abnormal connective tissue compartment (dermis). In tissues such as the skin, the repair of the dermis after wounding requires not only the fibroblasts that produce the ECM molecules, but also the overlying epithelial layer (keratinocytes), the endothelial cells, and smooth muscle cells of the blood vessel and white blood cells such as neutrophils and macrophages, which together orchestrate the cytokine-mediated signaling and paracrine interactions that are required to regulate the proper extent and timing of the repair process. This review will focus on the importance of extracellular molecules in the microenvironment, primarily the proteoglycans and glycosaminoglycan hyaluronan, and their roles in wound healing. First, we will briefly summarize the physiological, cellular, and biochemical elements of wound healing, including the importance of cytokine cross-talk between cell types. Second, we will discuss the role of proteoglycans and hyaluronan in regulating these processes. Finally, approaches that utilize these concepts as potential therapies for fibrosis are discussed.

Hyaluronan-induced VEGF-C promotes fibrosis-induced lymphangiogenesis via Toll-like receptor 4-dependent signal pathway

Hyaluronan (HA), a component of the extracellular matrix, modulates cellular behavior including angiogenesis. However, little is known about the effect of HA on lymphangiogenesis in fibrosis model. In this study, we investigated the roles of HA in lymphangiogenesis of unilateral ureteral obstruction (UUO). We found that HA cooperated synergistically with vascular endothelial cell growth factor-C to stimulate capillary-like tube formation and increase migration of cells in a haptotaxis assay. Accumulation of HA in the cortical interstitial space was positively correlated with the number of lymphatic vessels after UUO. Depletion of macrophages with clodronate decreased UUO-induced HA accumulation and lymphangiogenesis. Additionally, hyaluronan synthase (HAS) mRNA expression and HA production were increased in bone marrow-derived macrophages upon stimulation with TGF-β1. Transfer of mHAS2 and mHAS3 knock-down CD11b-positive macrophages to SCID mice resulted in a partial decrease in UUO-induced lymphangiogenesis. HA increased expression of vascular endothelial cell growth factor-C in macrophages. Vascular endothelial cell growth factor-C expression and LYVE-1-positive lymphatic area was significantly lower in the UUO-kidney from TLR4 null mice than that from TLR4 wild-type mice. Collectively, these results suggest that HA increases lymphangiogenesis in renal fibrosis model and also stimulates vascular endothelial cell growth factor-C production from macrophages through Toll-like receptor 4-dependent signal pathway.

Sugars in the microenvironment: the sticky problem of HA turnover in tumors

The properties and behavior of tumor cells are closely regulated by their microenvironment. Accordingly, stromal cells and extracellular matrix components can have a pronounced effect on cancer initiation, growth, and progression. The linear glycosaminoglycan hyaluronan (HA) is a major component of the extracellular matrix. Altered synthesis and degradation of HA in the tumor context has been implicated in many aspects of tumor biology. In particular, the accumulation of small HA oligosaccharides (sHA) in the tumor interstitial space may play a decisive role, due to the ability of sHA to activate a number of biological processes that are not modulated by high molecular weight (HMW)-HA. In this article, we review the normal physiological role and metabolism of HA and then survey the evidence implicating HA in tumor growth and progression, focusing in particular on the potential contribution of sHA to these processes.

Tertiary Lymphoid Structures in Rheumatoid Arthritis: NF-κB-Inducing Kinase-Positive Endothelial Cells as Central Players

Tertiary lymphoid structures (TLSs) in chronic inflammation, including rheumatoid arthritis (RA) synovial tissue (ST), often contain high endothelial venules and follicular dendritic cells (FDCs). Endothelial cell (EC)-specific lymphotoxin β (LTβ) receptor signaling is critical for the formation of lymph nodes and high endothelial venules. FDCs arise from perivascular platelet-derived growth factor receptor β(+) precursor cells (preFDCs) that require specific group 3 innate lymphoid cells (ILC3s) and LTβ for their expansion. Previously, we showed that RA ST contains ECs that express NF-κB-inducing kinase (NIK), which is pivotal in LTβ-induced noncanonical NF-κB signaling. We studied the relation between NIK(+) ECs, (pre)FDCs, and ILC3s with respect to TLSs in RA ST. TLS(+) tissues exhibited a significantly increased expression of genes involved in noncanonical NF-κB signaling, including NIK, and immunohistochemical analysis revealed that NIK was almost exclusively expressed by ECs. ILC3s were present in human RA ST in very low numbers, but not differentially in TLS(+) tissues. In contrast, TLS(+) tissues contained significantly more NIK(+) ECs and perivascular platelet-derived growth factor receptor β(+) preFDCs, which correlated significantly with the quantity of FDCs. We established a strong link between NIK(+) ECs, (pre)FDCs, and the presence of TLSs, indicating that NIK(+) ECs may not only be important orchestrators of lymph node development but also contribute to the formation of TLSs in chronic inflammation.

IL-17 and insulin/IGF1 enhance adhesion of prostate cancer cells to vascular endothelial cells through CD44-VCAM-1 interaction

BACKGROUND

Extravasation is a critical step in cancer metastasis, in which adhesion of intravascular cancer cells to the vascular endothelial cells is controlled by cell surface adhesion molecules. The role of interleukin-17 (IL-17), insulin, and insulin-like growth factor 1 (IGF1) in adhesion of prostate cancer cells to the vascular endothelial cells is unknown, which is the subject of the present study.

METHODS

Human umbilical vein endothelial cells (HUVECs) and human prostate cancer cell lines (PC-3, DU-145, LNCaP, and C4-2B) were analyzed for expression of vascular cell adhesion molecule 1 (VCAM-1), integrins, and cluster of differentiation 44 (CD44) using flow cytometry and Western blot analysis. The effects of IL-17, insulin, and IGF1 on VCAM-1 expression and adhesion of prostate cancer cells to HUVECs were examined. The interaction of VCAM-1 and CD44 was assessed using immunoprecipitation assays.

RESULTS

Insulin and IGF1 acted with IL-17 to increase VCAM-1 expression in HUVECs. PC-3, DU-145, LNCaP, and C4-2B cells expressed β1 integrin but not α4 integrin. CD44 was expressed by PC-3 and DU-145 cells but not by LNCaP or C4-2B cells. When HUVECs were treated with IL-17, insulin or IGF1, particularly with a combination of IL-17 and insulin (or IGF1), adhesion of PC-3 and DU-145 cells to HUVECs was significantly increased. In contrast, adhesion of LNCaP and C4-2B cells to HUVECs was not affected by treatment of HUVECs with IL-17 and/or insulin/IGF1. CD44 expressed in PC-3 cells physically bound to VCAM-1 expressed in HUVECs.

CONCLUSIONS

CD44-VCAM-1 interaction mediates the adhesion between prostate cancer cells and HUVECs. IL-17 and insulin/IGF1 enhance adhesion of prostate cancer cells to vascular endothelial cells through increasing VCAM-1 expression in the vascular endothelial cells. These findings suggest that IL-17 may act with insulin/IGF1 to promote prostate cancer metastasis.

Osthole promotes anti-tumor immune responses in tumor-bearing mice with hepatocellular carcinoma

Osthole, a natural coumarin derivative, has been shown to have anti-tumor and anti-inflammatory activity. However, the effect of osthole on anti-tumor immune responses in tumor-bearing mice has not yet been reported. In the present study, osthole treatment did not affect the weight and the coefficient of thymus and spleen in tumor-bearing mice with hepatocellular carcinoma (HCC). However, osthole administration significantly elevated the proportion and number of the splenic CD8(+) T cells, the proportion of CD4(+) T and CD8(+) T cells in tumor tissues, and the levels of IL-2 and TNF-α in the serum of HCC tumor-bearing mice. Our results suggested that osthole could promote the activation of the tumor-infiltrating CD4(+) T and CD8(+) T cells, and elevate the proportion of CD4(+) and CD8(+) effector T cells. Osthole treatment also significantly decreased the proportion of CD4(+)CD25(+)Foxp3(+) regulatory T cells in the spleen. Taken together, osthole could enhance the T cell mediated anti-tumor immune responses in the tumor-bearing mice with HCC.

Hyaluronan - a functional and structural sweet spot in the tissue microenvironment

Transition from homeostatic to reactive matrix remodeling is a fundamental adaptive tissue response to injury, inflammatory disease, fibrosis, and cancer. Alterations in architecture, physical properties, and matrix composition result in changes in biomechanical and biochemical cellular signaling. The dynamics of pericellular and extracellular matrices, including matrix protein, proteoglycan, and glycosaminoglycan modification are continually emerging as essential regulatory mechanisms underlying cellular and tissue function. Nevertheless, the impact of matrix organization on inflammation and immunity in particular and the consequent effects on tissue healing and disease outcome are arguably under-studied aspects of adaptive stress responses. Herein, we review how the predominant glycosaminoglycan hyaluronan (HA) contributes to the structure and function of the tissue microenvironment. Specifically, we examine the evidence of HA degradation and the generation of biologically active smaller HA fragments in pathological settings in vivo. We discuss how HA fragments versus nascent HA via alternate receptor-mediated signaling influence inflammatory cell recruitment and differentiation, resident cell activation, as well as tumor growth, survival, and metastasis. Finally, we discuss how HA fragmentation impacts restoration of normal tissue function and pathological outcomes in disease.

The where, when, how, and why of hyaluronan binding by immune cells

Hyaluronan is made and extruded from cells to form a pericellular or extracellular matrix (ECM) and is present in virtually all tissues in the body. The size and form of hyaluronan present in tissues are indicative of a healthy or inflamed tissue, and the interactions of hyaluronan with immune cells can influence their response. Thus, in order to understand how inflammation is regulated, it is necessary to understand these interactions and their consequences. Although there is a large turnover of hyaluronan in our bodies, the large molecular mass form of hyaluronan predominates in healthy tissues. Upon tissue damage and/or infection, the ECM and hyaluronan are broken down and an inflammatory response ensues. As inflammation is resolved, the ECM is restored, and high molecular mass hyaluronan predominates again. Immune cells encounter hyaluronan in the tissues and lymphoid organs and respond differently to high and low molecular mass forms. Immune cells differ in their ability to bind hyaluronan and this can vary with the cell type and their activation state. For example, peritoneal macrophages do not bind soluble hyaluronan but can be induced to bind after exposure to inflammatory stimuli. Likewise, naïve T cells, which typically express low levels of the hyaluronan receptor, CD44, do not bind hyaluronan until they undergo antigen-stimulated T cell proliferation and upregulate CD44. Despite substantial knowledge of where and when immune cells bind hyaluronan, why immune cells bind hyaluronan remains a major outstanding question. Here, we review what is currently known about the interactions of hyaluronan with immune cells in both healthy and inflamed tissues and discuss how hyaluronan binding by immune cells influences the inflammatory response.

Lymphocyte 'homing' and chronic inflammation

Chronic inflammation is a response to prolonged exposure to injurious stimuli that harm and destroy tissues and promote lymphocyte infiltration into inflamed sites. Following progressive accumulation of lymphocytes, the histology of inflamed tissue begins to resemble that of peripheral lymphoid organs, which can be referred to as lymphoid neogenesis or formation of tertiary lymphoid tissues. Lymphocyte recruitment to inflamed tissues is also reminiscent of lymphocyte homing to peripheral lymphoid organs. In the latter, under physiological conditions, homing receptors expressed on lymphocytes adhere to vascular addressin expressed on high endothelial venules (HEVs), initiating a lymphocyte migration process composed of sequential adhesive interactions. Intriguingly, in chronic inflammation, HEV-like vessels are induced de novo, despite the fact that the inflamed site is not originally lymphoid tissue, and these vessels contribute to lymphocyte recruitment in a manner similar to physiological lymphocyte homing. In this review, we first describe physiological lymphocyte homing mechanisms focusing on vascular addressins. We then describe HEV-like vessel-mediated pathogenesis seen in various chronic inflammatory disorders such as Helicobacter pylori gastritis, inflammatory bowel disease (IBD), autoimmune pancreatitis and sclerosing sialadenitis, as well as chronic inflammatory cell neoplasm MALT lymphoma, with reference to our work and that of others.

The role of hyaluronan in innate defense responses of the intestine

Hyaluronan is an abundant extracellular matrix component prevalent in the vertebrate intestinal tract. Here we discuss what is known about hyaluronan distribution during homeostasis and inflammatory diseases of the gut and discuss ways in which this glycosaminoglycan can participate in regulating innate host defense mechanisms. These natural responses include mechanisms promoting rapid leukocyte recruitment after bacterial challenge/colon tissue damage as well as promoting epithelial defense mechanisms in the intestine.

Interactions between CD44 and Hyaluronan in Leukocyte Trafficking

Recruitment of leukocytes from the bloodstream to inflamed tissues requires a carefully regulated cascade of binding interactions between adhesion molecules on leukocytes and endothelial cells. Adhesive interactions between CD44 and hyaluronan (HA) have been implicated in the regulation of immune cell trafficking within various tissues. In this review, the biology of CD44–HA interactions in cell trafficking is summarized, with special attention to neutrophil recruitment within the liver microcirculation. We describe the molecular mechanisms that regulate adhesion between neutrophil CD44 and endothelial HA, including recent evidence implicating serum-derived hyaluronan-associated protein as an important co-factor in the binding of HA to CD44 under flow conditions. CD44–HA-mediated neutrophil recruitment has been shown to contribute to innate immune responses to invading microbes, as well as to the pathogenesis of many inflammatory diseases, including various liver pathologies. As a result, blockade of neutrophil recruitment by targeting CD44–HA interactions has proven beneficial as an anti-inflammatory treatment strategy in a number of animal models of inflammatory diseases.