Hyaluronan: Biosynthesis and signaling

Inhibitory effects of Aphanizomenon flos-aquae constituents on human UDP-glucose dehydrogenase activity

OBJECTIVE

The purpose of this study was to investigate the in vitro inhibitory effects of the edible microalga Aphanizomenon flos-aquae (AFA) on human UDP-α-d-glucose 6-dehydrogenase (UGDH) activity, a cytosolic enzyme involved both in tumor progression and in phytochemical bioavailability.

METHODS

Both the hydrophilic and ethanolic AFA extracts as well as the constitutive active principles phycocyanin (PC), phycocyanobilin (PCB) and mycosporine-like amino acids (MAAs) were tested.

RESULTS

Among AFA components, PCB presented the strongest inhibitory effect on UGDH activity, acting as a competitive inhibitor with respect to UDP-glucose and a non-competitive inhibitor with respect to NAD(+). In preliminary experiments, AFA PCB was also effective in reducing the colony formation capacity of PC-3 prostate cancer cells and FTC-133 thyroid cancer cells.

CONCLUSIONS

Overall, these findings confirmed that AFA and its active principles are natural compounds with high biological activity. Further studies evaluating the effects of AFA PCB in reducing tumor cell growth and phytochemical glucuronidation are encouraged.

Extracellular matrix component signaling in cancer

Cell responses to the extracellular matrix depend on specific signaling events. These are important from early development, through differentiation and tissue homeostasis, immune surveillance, and disease pathogenesis. Signaling not only regulates cell adhesion cytoskeletal organization and motility but also provides survival and proliferation cues. The major classes of cell surface receptors for matrix macromolecules are the integrins, discoidin domain receptors, and transmembrane proteoglycans such as syndecans and CD44. Cells respond not only to specific ligands, such as collagen, fibronectin, or basement membrane glycoproteins, but also in terms of matrix rigidity. This can regulate the release and subsequent biological activity of matrix-bound growth factors, for example, transforming growth factor-β. In the environment of tumors, there may be changes in cell populations and their receptor profiles as well as matrix constitution and protein cross-linking. Here we summarize roles of the three major matrix receptor types, with emphasis on how they function in tumor progression.

Characterisation of separated end hyaluronan oligosaccharides from leech hyaluronidase and evaluation of angiogenesis

Hyaluronan oligosaccharides (o-HAs), especially saturated o-HAs, have attracted intensive attention due to their potential applications in medical treatments. In this study, the hydrolysis process of leech hyaluronidase (LHase) towards the hyaluronan was investigated by HPLC and HPLC/ESI-MS. The proportions of hyaluronan tetrasaccharide (HA4) with hexasaccharide (HA6), end products, were illustrated to have a relationship with the amount of LHase. Higher yield of HA4 was achieved with higher activity of LHase. After optimisation of the packing resin and operation parameters (balanced pH, elution concentration, elution volume and elution flow rate), the highly pure HA4 and HA6 were efficiently separated and prepared by combining ion exchange Q-Sepharose Fast Flow and size exclusion column chromatography. Compared with o-HAs (average Mr of 4000 Da), HA4 and HA6 were demonstrated to show higher activity for promoting angiogenesis, which was similar with the corresponding HA4 and HA6 produced by bovine testicular hyaluronidase. The pure HA4 and HA6 that prepared from LHase will attract intensive studies and be used in potential applications in near future.

Impaired Synthesis of Stromal Components in Response to Minnelide Improves Vascular Function, Drug Delivery, and Survival in Pancreatic Cancer

PURPOSE

Pancreatic cancer stromal microenvironment is considered to be the major reason for failure of conventional and targeted therapy for this disease. The desmoplastic stroma, comprising mainly collagen and glycosaminoglycans like hyaluronan (HA), is responsible for compression of vasculature in the tumor resulting in impaired drug delivery and poor prognosis. Minnelide, a water-soluble prodrug of triptolide currently in phase I clinical trial, has been very effective in multiple animal models of pancreatic cancer. However, whether Minnelide will have efficacious delivery into the tumor despite the desmoplastic stroma has not been evaluated before.

EXPERIMENT DESIGN

Patient tumor-derived xenografts (PDX) and spontaneous pancreatic cancer mice were treated with 0.42 and 0.21 mg/kg body weight for 30 days. Stromal components were determined by IHC and ELISA-based assays. Vascular functionality and drug delivery to the tumor were assessed following treatment with Minnelide.

RESULT

Our current study shows that treatment with Minnelide resulted in reduction of ECM components like HA and collagen in the pancreatic cancer stroma of both the spontaneous KPC mice as well as in patient tumor xenografts. Furthermore, treatment with Minnelide improved functional vasculature in the tumors resulting in four times more functional vessels in the treated animals compared with untreated animals. Consistent with this observation, Minnelide also resulted in increased drug delivery into the tumor compared with untreated animals. Along with this, Minnelide also decreased viability of the stromal cells along with the tumor cells in pancreatic adenocarcinoma.

CONCLUSIONS

In conclusion, these results are extremely promising as they indicate that Minnelide, along with having anticancer effects is also able to deplete stroma in pancreatic tumors, which makes it an effective therapy for pancreatic cancer.

Multi-Functional Macromers for Hydrogel Design in Biomedical Engineering and Regenerative Medicine

Contemporary biomaterials are expected to provide tailored mechanical, biological and structural cues to encapsulated or invading cells in regenerative applications. In addition, the degradative properties of the material also have to be adjustable to the desired application. Oligo- or polymeric building blocks that can be further cross-linked into hydrogel networks, here addressed as macromers, appear as the prime option to assemble gels with the necessary degrees of freedom in the adjustment of the mentioned key parameters. Recent developments in the design of multi-functional macromers with two or more chemically different types of functionalities are summarized and discussed in this review illustrating recent trends in the development of advanced hydrogel building blocks for regenerative applications.

Deficiency of hyaluronan synthase 1 (Has1) results in chronic joint inflammation and widespread intra-articular fibrosis in a murine model of knee joint cartilage damage

OBJECTIVE

Articular cartilage defects commonly result from traumatic injury and predispose to degenerative joint diseases. To test the hypothesis that aberrant healing responses and chronic inflammation lead to osteoarthritis (OA), we examined spatiotemporal changes in joint tissues after cartilage injury in murine knees. Since intra-articular injection of hyaluronan (HA) can attenuate injury-induced osteoarthritis in wild-type (WT) mice, we investigated a role for HA in the response to cartilage injury in mice lacking HA synthase 1 (Has1(-/-)).

DESIGN

Femoral groove cartilage of WT and Has1(-/-) mice was debrided to generate a non-bleeding wound. Macroscopic imaging, histology, and gene expression were used to evaluate naïve, sham-operated, and injured joints.

RESULTS

Acute responses (1-2 weeks) in injured joints from WT mice included synovial hyperplasia with HA deposition and joint-wide increases in expression of genes associated with inflammation, fibrosis, and extracellular matrix (ECM) production. By 4 weeks, some resurfacing of damaged cartilage occurred, and early cell responses were normalized. Cartilage damage in Has1(-/-) mice also induced early responses; however, at 4 weeks, inflammation and fibrosis genes remained elevated with widespread cartilage degeneration and fibrotic scarring in the synovium and joint capsule.

CONCLUSIONS

We conclude that the ineffective repair of injured cartilage in Has1(-/-) joints can be at least partly explained by the markedly enhanced expression of particular genes in pathways linked to ECM turnover, IL-17/IL-6 cytokine signaling, and apoptosis. Notably, Has1 ablation does not alter gross HA content in the ECM, suggesting that HAS1 has a unique function in the metabolism of inflammatory HA matrices.

Hyaluronan's Role in Fibrosis: A Pathogenic Factor or a Passive Player?

Fibrosis is a debilitating condition that can lead to impairment of the affected organ's function. Excessive deposition of extracellular matrix (ECM) molecules is characteristic of most fibrotic tissues. Fibroblasts activated by cytokines or growth factors differentiate into myofibroblasts that drive fibrosis by depositing ECM molecules, such as collagen, fibronectin, and connective tissue growth factor. Transforming growth factor-β (TGF-β) is one of the major profibrotic cytokines which promotes fibrosis by signaling abnormal ECM regulation. Hyaluronan (HA) is a major ECM glycosaminoglycan that is regulated by TGF-β and whose role in fibrosis is emerging. Aside from its role as a hydrating, space filling polymer, HA regulates different cellular functions and is known to have a role in wound healing and inflammation. Importantly, HA deposition is increased in multiple fibrotic diseases. In this review we highlight studies that link HA to fibrosis and discuss what is known about the role of HA, its receptors, and its anabolic and catabolic enzymes in different fibrotic diseases.

The Rise and Fall of Hyaluronan in Respiratory Diseases

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

Regulated Hyaluronan Synthesis by Vascular Cells

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

Hyaluronan Synthesis, Catabolism, and Signaling in Neurodegenerative Diseases

The glycosaminoglycan hyaluronan (HA), a component of the extracellular matrix, has been implicated in regulating neural differentiation, survival, proliferation, migration, and cell signaling in the mammalian central nervous system (CNS). HA is found throughout the CNS as a constituent of proteoglycans, especially within perineuronal nets that have been implicated in regulating neuronal activity. HA is also found in the white matter where it is diffusely distributed around astrocytes and oligodendrocytes. Insults to the CNS lead to long-term elevation of HA within damaged tissues, which is linked at least in part to increased transcription of HA synthases. HA accumulation is often accompanied by elevated expression of at least some transmembrane HA receptors including CD44. Hyaluronidases that digest high molecular weight HA into smaller fragments are also elevated following CNS insults and can generate HA digestion products that have unique biological activities. A number of studies, for example, suggest that both the removal of high molecular weight HA and the accumulation of hyaluronidase-generated HA digestion products can impact CNS injuries through mechanisms that include the regulation of progenitor cell differentiation and proliferation. These studies, reviewed here, suggest that targeting HA synthesis, catabolism, and signaling are all potential strategies to promote CNS repair.

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.

Xanthophylls lutein and zeaxanthin modify gene expression and induce synthesis of hyaluronan in keratinocyte model of human skin

Background

Clinical trials report benefits of the xanthophylls lutein and zeaxanthin for skin health. Here a keratinocyte culture was used to investigate the effects of in vitro xanthophyll treatment on gene expression and biochemical pathways.

Methods

We employed the EpiDerm tissue model, Affymetrix Human Genome Array U113, bioinformatics analyses, qPCR validation and biochemical assays for glycosaminoglycans.

Results

We discovered 176 genes were significantly (p<0.05) down-regulated (log 2FC>2) and 47 genes were significantly up-regulated. Among the down-regulated genes we validated by qPCR marked reduction in expression of peptidase inhibitors. Bioinformatic analysis of the up-regulated genes implicated biosynthetic pathways for glycosaminoglycans. We assayed but found no increase in production of sulfated glycosaminoglycans, however there was a significant increase in biosynthesis of hyaluronic acid, a non-sulfated glycan.

Conclusions

The pattern of xanthophyll-regulated genes and the resulting biochemical responses can be linked with the responses observed in clinic trials.

General significance

Skin health benefits from xanthophyll supplementation and this study reveals molecular mechanisms for some of the effects.

Analysis of Total Human Urinary Glycosaminoglycan Disaccharides by Liquid Chromatography-Tandem Mass Spectrometry

The determination of complex analytes, present at low concentrations, in biological fluids poses a difficult challenge. This study relies on an optimized method of recovery, enzymatic treatment, and disaccharide analysis by liquid chromatography-tandem mass spectrometry to rapidly determine low concentrations of glycosaminoglycans in human urine. The approach utilizes multiple reaction monitoring (MRM) of glycosaminoglycan disaccharides obtained from treating urine samples with recombinant heparin lyases and chondroitin lyase. This rapid and sensitive method allows the analysis of glycosaminoglycan content and disaccharide composition in urine samples having concentrations 10- to 100-fold lower than those typically analyzed from patients with metabolic diseases, such as mucopolysaccharidosis. The current method facilitates the analysis low (ng/mL) levels of urinary glycosaminoglycans present in healthy individuals and in patients with pathological conditions, such as inflammation and cancers, that can subtly alter glycosaminoglycan content and composition.

Hyaluronan based hydrogels provide an improved model to study megakaryocyte-matrix interactions

Hyaluronan (HA) is a glycosamminoglican involved in cell biology as well as a relevant polymer for tissue engineering and regenerative medicine. Megakaryocytes (Mks) are immersed in a mesh of extracellular matrix (ECM) components that regulate their maturation in the bone marrow (BM) and the release of platelets into the bloodstream. While fibrous ECMs such as collagens and fibronectin have been demonstrated to differently regulate Mk function and platelet release, the role of HA, that fills the majority of the BM extracellular interstitial space, has not been investigated so far. Here we demonstrated that, although human Mks express HA receptors, they are not affected by HA in terms of in vitro differentiation, maturation and platelet formation. Importantly, chemical properties of HA were exploited to generate hydrogels with entrapped ECMs that represent a useful model to more closely mimic the tridimensional characteristics of the BM environment for studying Mk function. In conclusion, in this work we demonstrated that HA is an ideal candidate for a 3D ex vivo model of human BM ECM component environment.

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.

Biology and biotechnology of hyaluronan

The hyaluronan (HA) polymer is a critical component of extracellular matrix with a remarkable structure: is a linear and unbranched polymer without sulphate or phosphate groups. It is ubiquitous in mammals showing several biological functions, ranging from cell proliferation and migration to angiogenesis and inflammation. For its critical biological functions the amount of HA in tissues is carefully controlled by different mechanisms including covalent modification of the synthetic enzymes and epigenetic control of their gene expression. The concentration of HA is also critical in several pathologies including cancer, diabetes and inflammation. Beside these biological roles, the structural properties of HA allow it to take advantage of its capacity to form gels even at concentration of 1 % producing scaffolds with very promising applications in regenerative medicine as biocompatible material for advanced therapeutic uses. In this review we highlight the biological aspects of HA addressing the mechanisms controlling the HA content in tissues as well as its role in important human pathologies. In the second part of the review we highlight the different use of HA polymers in the modern biotechnology.

Synthesis of a hexasaccharide partial sequence of hyaluronan for click chemistry and more

In the present work, the synthesis of a hexasaccharide partial sequence of hyaluronan equipped with a terminal azido moiety is reported. This hexasaccharide can be used for the attachment on surfaces by means of click chemistry and after suitable deprotection for biophysical studies.

Regulation of hyaluronan synthesis in vascular diseases and diabetes

Cell microenvironment has a critical role determining cell fate and modulating cell responses to injuries. Hyaluronan (HA) is a ubiquitous extracellular matrix glycosaminoglycan that can be considered a signaling molecule. In fact, interacting with several cell surface receptors can deeply shape cell behavior. In vascular biology, HA triggers smooth muscle cells (SMCs) dedifferentiation which contributes to vessel wall thickening. Furthermore, HA is able to modulate inflammation by altering the adhesive properties of endothelial cells. In hyperglycemic conditions, HA accumulates in vessels and can contribute to the diabetic complications at micro- and macrovasculature. Due to the pivotal role in favoring atherogenesis and neointima formation after injuries, HA could be a new target for cardiovascular pathologies. This review will focus on the recent findings regarding the regulation of HA synthesis in human vascular SMCs. In particular, the effects of the intracellular HA substrates availability, adenosine monophosphate-activated protein kinase (AMPK), and protein O-GlcNAcylation on the main HA synthetic enzyme (i.e., HAS2) will be discussed.

Hyaluronan fragments as mediators of inflammation in allergic pulmonary disease

Asthma is frequently caused and/or exacerbated by sensitization to allergens, which are ubiquitous in many indoor and outdoor environments. Severe asthma is characterized by airway hyperresponsiveness and bronchial constriction in response to an inhaled allergen, leading to a disease course that is often very difficult to treat with standard asthma therapies. As a result of interactions among inflammatory cells, structural cells, and the intercellular matrix of the allergic lung, patients with sensitization to allergens may experience a greater degree of tissue injury followed by airway wall remodeling and progressive, accumulated pulmonary dysfunction as part of the disease sequela. In addition, turnover of extracellular matrix (ECM) components is a hallmark of tissue injury and repair. This review focuses on the role of the glycosaminoglycan hyaluronan (HA), a component of the ECM, in pulmonary injury and repair with an emphasis on allergic asthma. Both the synthesis and degradation of the ECM are critical contributors to tissue repair and remodeling. Fragmented HA accumulates during tissue injury and functions in ways distinct from the larger native polymer. There is gathering evidence that HA degradation products are active participants in stimulating the expression of inflammatory genes in a variety of immune cells at the injury site. In this review, we will consider recent advances in the understanding of the mechanisms that are associated with HA accumulation and inflammatory cell recruitment in the asthmatic lung.

Hyaluronan and cardiac regeneration

Hyaluronan (HA) is abundantly expressed in several human tissues and a variety of roles for HA has been highlighted. Particularly relevant for tissue repair, HA is actively produced during tissue injury, as widely evidenced in wound healing investigations. In the heart HA is involved in physiological functions, such as cardiac development during embryogenesis, and in pathological conditions including atherosclerosis and myocardial infarction. Moreover, owing to its relevant biological properties, HA has been widely used as a biomaterial for heart regeneration after a myocardial infarction. Indeed, HA and its derivatives are biodegradable and biocompatible, promote faster healing of injured tissues, and support cells in relevant processes including survival, proliferation, and differentiation. Injectable HA-based therapies for cardiovascular disease are gaining growing attention because of the benefits obtained in preclinical models of myocardial infarction. HA-based hydrogels, especially as a vehicle for stem cells, have been demonstrated to improve the process of cardiac repair by stimulating angiogenesis, reducing inflammation, and supporting local and grafted cells in their reparative functions. Solid-state HA-based scaffolds have been also investigated to produce constructs hosting mesenchymal stem cells or endothelial progenitor cells to be transplanted onto the infarcted surface of the heart. Finally, applying an ex-vivo mechanical stretching, stem cells grown in HA-based 3D scaffolds can further increase extracellular matrix production and proneness to differentiate into muscle phenotypes, thus suggesting a potential strategy to create a suitable engineered myocardial tissue for cardiac regeneration.

Hyaluronan-phosphatidylethanolamine polymers form pericellular coats on keratinocytes and promote basal keratinocyte proliferation

Aged keratinocytes have diminished proliferative capacity and hyaluronan (HA) cell coats, which are losses that contribute to atrophic skin characterized by reduced barrier and repair functions. We formulated HA-phospholipid (phosphatidylethanolamine, HA-PE) polymers that form pericellular coats around cultured dermal fibroblasts independently of CD44 or RHAMM display. We investigated the ability of these HA-PE polymers to penetrate into aged mouse skin and restore epidermal function in vivo. Topically applied Alexa(647)-HA-PE penetrated into the epidermis and dermis, where it associated with both keratinocytes and fibroblasts. In contrast, Alexa(647)-HA was largely retained in the outer cornified layer of the epidermis and quantification of fluorescence confirmed that significantly more Alexa(647)-HA-PE penetrated into and was retained within the epidermis than Alexa(647)-HA. Multiple topical applications of HA-PE to shaved mouse skin significantly stimulated basal keratinocyte proliferation and epidermal thickness compared to HA or vehicle cream alone. HA-PE had no detectable effect on keratinocyte differentiation and did not promote local or systemic inflammation. These effects of HA-PE polymers are similar to those reported for endogenous epidermal HA in youthful skin and show that topical application of HA-PE polymers can restore some of the impaired functions of aged epidermis.

Natural antisense transcript for hyaluronan synthase 2 (HAS2-AS1) induces transcription of HAS2 via protein O-GlcNAcylation

Changes in the microenvironment organization within vascular walls are critical events in the pathogenesis of vascular pathologies, including atherosclerosis and restenosis. Hyaluronan (HA) accumulation into artery walls supports vessel thickening and is involved in many cardiocirculatory diseases. Excessive cytosolic glucose can enter the hexosamine biosynthetic pathway, increase UDP-N-acetylglucosamine (UDP-GlcNAc) availability, and lead to modification of cytosolic proteins via O-linked attachment of the monosaccharide β-N-GlcNAc (O-GlcNAcylation) from UDP-GlcNAc by the enzyme O-GlcNAc transferase. As many cytoplasmic and nuclear proteins can be glycosylated by O-GlcNAc, we studied whether the expression of the HA synthases that synthesize HA could be controlled by O-GlcNAcylation in human aortic smooth muscle cells. Among the three HAS isoenzymes, only HAS2 mRNA increased after O-GlcNAcylation induced by glucosamine treatments or by inhibiting O-GlcNAc transferase with PUGNAC (O-(2-acetamido-2-deoxy-d-glucopyranosylidene)amino-N-phenylcarbamate). We found that the natural antisense transcript of HAS2 (HAS2-AS1) was absolutely necessary to induce the transcription of the HAS2 gene. Moreover, we found that O-GlcNAcylation modulated HAS2-AS1 promoter activation by recruiting the NF-κB subunit p65, but not the HAS2 promoter, whereas HAS2-AS1 natural antisense transcript, working in cis, regulated HAS2 transcription by altering the chromatin structure around the HAS2 proximal promoter via O-GlcNAcylation and acetylation. These results indicate that HAS2 transcription can be finely regulated not only by recruiting transcription factors to the promoter as previously described but also by modulating chromatin accessibility by epigenetic modifications.

Hyaluronan and RHAMM in wound repair and the "cancerization" of stromal tissues

Tumors and wounds share many similarities including loss of tissue architecture, cell polarity and cell differentiation, aberrant extracellular matrix (ECM) remodeling (Ballard et al., 2006) increased inflammation, angiogenesis, and elevated cell migration and proliferation. Whereas these changes are transient in repairing wounds, tumors do not regain tissue architecture but rather their continued progression is fueled in part by loss of normal tissue structure. As a result tumors are often described as wounds that do not heal. The ECM component hyaluronan (HA) and its receptor RHAMM have both been implicated in wound repair and tumor progression. This review highlights the similarities and differences in their roles during these processes and proposes that RHAMM-regulated wound repair functions may contribute to “cancerization” of the tumor microenvironment.

Collagen VI and hyaluronan: the common role in breast cancer

Collagen VI and hyaluronan are widely distributed extracellular matrix macromolecules that play a crucial role in tissue development and are highly expressed in cancers. Both hyaluronan and collagen VI are upregulated in breast cancer, generating a microenvironment that promotes tumour progression and metastasis. A growing number of studies show that these two molecules are involved in inflammation and angiogenesis by recruiting macrophages and endothelial cells, respectively. Additionally, collagen VI induces epithelial-mesenchymal transition that is correlated to increased synthesis of hyaluronan in mammary cells. Hyaluronan has also a specific role in cellular functions that depends mainly on the size of the polymer, whereas the effect of collagen VI in tumour progression may be the result of the intact molecule or the C5 peptide of α3(VI) chain, known as endotrophin. Collectively, these findings strongly support the parallel role of these molecules in tumour progression and suggest that they may be used as prognostic factors for the breast cancer treatment.