Hyaluronan Cables Research Articles

Abstract 4265: ZEB1-regulated hyaluronan network in the lung tumor microenvironment

Abstract In the tumor microenvironment, hyaluronan surrounds neighboring cells as one of the major components of the extracellular matrix and stimulates the epithelial-mesenchymal transition (EMT) of various epithelial cancer cells. However, the mechanism of how the hyaluronic network is formed by cancer cells and regulates cancer progression and metastasis has not been known in detail. Therefore, we investigated the role of the hyaluronan network built-up by cancer cells in regulating cancer progression and metastasis in the tumor microenvironment. Our study demonstrated that ZEB1, an EMT-inducing transcription factor, reconstructs the hyaluronan network to induce the expression of ITIH2, a hyaluronan-binding protein, and hyaluronic acid synthase-2 (HAS2), ZEB1 was also shown to control the isoform switching of CD44, a hyaluronan receptor. ITIH2 knockdown and HAS inhibition reduced the formation of hyaluronan cables and inhibited cancer cell migration and invasion. In addition, the treatment of a specific ITIH2 inhibitor identified through deep learning-based screening suppressed the formation of hyaluronan cables, cell migration, and metastasis. These findings suggest that targeting the hyaluronan network could be a novel strategy for suppressing lung cancer progression and metastasis in the tumor microenvironment. Citation Format: Sieun Lee, Jihye Park, Eun Ju Kim, Seongran Cho, Sungsoo Park, Jonathan M Kurie, Young-Ho Ahn. ZEB1-regulated hyaluronan network in the lung tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4265.

Monocyte adhesive hyaluronan matrix induced by hyperglycemia in diabetic lung injuries

Infiltrated pre-inflammatory monocytes and macrophages have important roles in the induction of diabetic lung injuries, but the mechanism mediating their infiltration is still unclear. Here, we showed that airway smooth muscle cells (SMCs) activated monocyte adhesion in response to hyperglycemic glucose (25.6mM) by significantly increasing hyaluronan (HA) in the cell matrix, with concurrent 2- to 4-fold increases in adhesion of U937 monocytic-leukemic cells. The HA-based structures were attributed directly to the high-glucose and not to increased extracellular osmolality, and they required growth stimulation of SMCs by serum. Treatment of SMCs with heparin in high-glucose induces synthesis of a much larger HA matrix, consistent with our observations in the glomerular SMCs. Further, we observed increases in tumor necrosis factor-stimulated gene-6 (TSG-6) expression in high-glucose and high-glucose plus heparin cultures, and the heavy chain (HC)-modified HA structures existed on the monocyte-adhesive cable structures in high-glucose and in high-glucose plus heparin-treated SMC cultures. Interestingly, these HC-modified HA structures were unevenly distributed along the HA cables. Further, the invitro assay with recombinant human TSG-6 and the HA14 oligo showed that heparin has no inhibitory activity on the TSG-6-induced HC-transfer to HA, consistent with the results from SMC cultures. These results support the hypothesis that hyperglycemia in airway smooth muscle induces the synthesis of a HA matrix that recruits inflammatory cells and establishes a chronic inflammatory process and fibrosis that lead to diabetic lung injuries.

Nitric oxide alters hyaluronan deposition by airway smooth muscle cells.

Asthma is a chronic inflammatory disease that is known to cause changes in the extracellular matrix, including changes in hyaluronan (HA) deposition. However, little is known about the factors that modulate its deposition or the potential consequences. Asthmatics with high levels of exhaled nitric oxide (NO) are characterized by greater airway reactivity and greater evidence of airway inflammation. Based on these data and our previous work we hypothesized that excessive NO promotes the pathologic production of HA by airway smooth muscle cells (SMCs). Exposure of cultured SMCs to various NO donors results in the accumulation of HA in the form of unique, cable-like structures. HA accumulates rapidly after exposure to NO and can be seen as early as one hour after NO treatment. The cable-like HA in NO-treated SMC cultures supports the binding of leukocytes. In addition, NO produced by murine macrophages (RAW cells) and airway epithelial cells also induces SMCs to produce HA cables when grown in co-culture. The modulation of HA by NO appears to be independent of soluble guanylate cyclase. Taken together, NO-induced production of leukocyte-binding HA by SMCs provides a new potential mechanism for the non-resolving airway inflammation in asthma and suggests a key role of non-immune cells in driving the chronic inflammation of the submucosa. Modulation of NO, HA and the consequent immune cell interactions may serve as potential therapeutic targets in asthma.

G1 Domain of Versican Regulates Hyaluronan Organization and the Phenotype of Cultured Human Dermal Fibroblasts.

Variants of versican have wide-ranging effects on cell and tissue phenotype, impacting proliferation, adhesion, pericellular matrix composition, and elastogenesis. The G1 domain of versican, which contains two Link modules that bind to hyaluronan (HA), may be central to these effects. Recombinant human G1 (rhG1) with an N-terminal 8 amino acid histidine (His) tag, produced in Nicotiana benthamiana, was applied to cultures of dermal fibroblasts, and effects on proliferation and pericellular HA organization determined. rhG1 located to individual strands of cell surface HA which aggregated into structures resembling HA cables. On both individual and aggregated strands, the spacing of attached rhG1 was similar (~120 nm), suggesting interaction between rhG1 molecules. Endogenous V0/V1, present on HA between attached rhG1, did not prevent cable formation, while treatment with V0/V1 alone, which also bound to HA, did not induce cables. A single treatment with rhG1 suppressed cell proliferation for an extended period. Treating cells for 4 weeks with rhG1 resulted in condensed layers of elongated, differentiated α actin-positive fibroblasts, with rhG1 localized to cell surfaces, and a compact extracellular matrix including both collagen and elastin. These results demonstrate that the G1 domain of versican can regulate the organization of pericellular HA and affect phenotype.

Hyaluronan Rafts on Airway Epithelial Cells

Many cells, including murine airway epithelial cells, respond to a variety of inflammatory stimuli by synthesizing leukocyte-adhesive hyaluronan (HA) cables that remain attached to their cell surfaces. This study shows that air-liquid interface cultures of murine airway epithelial cells (AECs) also actively synthesize and release a majority of their HA onto their ciliated apical surfaces to form a heavy chain hyaluronan (HC-HA) matrix in the absence of inflammatory stimuli. These matrices do not resemble the rope-like HA cables but occur in distinct sheets or rafts that can capture and embed leukocytes from cell suspensions. The HC-HA modification involves the transfer of heavy chains from the inter-α-inhibitor (IαI) proteoglycan, which has two heavy chains (HC1 and HC2) on its chondroitin sulfate chain. The transesterification transfer of HCs from chondroitin sulfate to HA is mediated by tumor necrosis factor-induced gene 6 (TSG-6), which is up-regulated in inflammatory reactions. Because the AEC cultures do not have TSG-6 nor serum, the source of IαI, assays for HCs and TSG-6 were done. The results show that AECs synthesize TSG-6 and their own heavy chain donor (pre-IαI) with a single heavy chain 3 (HC3), which are also constitutively expressed by human renal proximal tubular epithelial cells. These leukocyte adhesive HC3-HA structures were also found in the bronchoalveolar lavage of naïve mice and were observed on their apical ciliated surfaces. Thus, these leukocyte-adhesive HA rafts are now identified as HC3-HA complexes that could be part of a host defense mechanism filling some important gaps in our current understanding of murine airway epithelial biology and secretions.

Hyaluronan cable formation by ocular trabecular meshwork cells

Hyaluronan (HA) in the ocular trabecular meshwork (TM) is a critical modulator of aqueous humor outflow. Individual HA strands in the pericellular matrix can coalesce to form cable-like structures, which have different functional properties. Here, we investigated HA structural configuration by TM cells in response to various stimuli known to stimulate extracellular matrix (ECM) remodeling. In addition, the effects of HA cable induction on aqueous outflow resistance was determined. Primary TM cell cultures grown on tissue culture-treated plastic were treated for 12–48 h with TNFα, IL-1α, or TGFβ2. TM cells grown on silicone membranes were subject to mechanical stretch, which induces synthesis and activation of ECM proteolytic enzymes. HA structural configuration was investigated by HA binding protein (HAbp) staining and confocal microscopy. HAbp-labeled cables were induced by TNFα, TGFβ2 and mechanical stretch, but not by IL-1α. HA synthase (HAS) gene expression was quantitated by quantitative RT-PCR and HA concentration was measured by ELISA assay. By quantitative RT-PCR, HAS-1, -2, and -3 genes were differentially up-regulated and showed temporal differences in response to each treatment. HA concentration was increased in the media by TNFα, TGFβ2 and IL-1α, but mechanical stretch decreased pericellular HA concentrations. Immunofluorescence and Western immunoblotting were used to investigate the distribution and protein levels of the HA-binding proteins, tumor necrosis factor-stimulated gene-6 (TSG-6) and inter-α-inhibitor (IαI). Western immunoblotting showed that TSG-6 and IαI were increased by TNFα, TGFβ2 and IL-1α, but mechanical stretch reduced their levels. The underlying substrate appears to affect the identity of IαI·TSG-6·HA complexes since different complexes were detected when TM cells were grown on a silicone substrate compared to a rigid plastic surface. Porcine anterior segments were perfused with 10 μg/ml polyinosinic:polycytidylic acid (polyI:C), a potent inducer of HA cables, and outflow rates were monitored for 72 h. PolyI:C had no significant effect on outflow resistance in porcine anterior segments perfused at physiological pressure. Collectively, HAS gene expression, HA concentration and configuration are differentially modified in response to several treatments that induce ECM remodeling in TM cells. In ocular TM cells, our data suggests that the most important determinant of HA cable formation appears to be the ratio of HA chains produced by the different HAS genes. However, the act of rearranging pericellular HA into cable-like structures does not appear to influence aqueous outflow resistance.

Increased hyaluronan levels in HABP1/p32/gC1qR overexpressing HepG2 cells inhibit autophagic vacuolation regulating tumor potency.

Tumor growth and development is influenced by its microenvironment. A major extracellular matrix molecule involved in cancer progression is hyaluronan (HA). Hyaluronan and expression of a number of hyaladherin family proteins are dramatically increased in many cancer malignancies. One such hyaladherin, hyaluronan-binding protein 1 (HABP1/p32/gC1qR) has been considered to be a biomarker for tumor progression. Interestingly, overexpression of HABP1 in fibroblast has been shown to increase autophagy via generation of excess reactive oxygen species (ROS) and depletion of HA leading to apoptosis. Cancerous cells are often found to exhibit decreased rate of proteolysis/autophagy in comparison to their normal counterparts. To determine if HABP1 levels alter tumorigenicity of cancerous cells, HepR21, the stable transfectant overexpressing HABP1 in HepG2 cell line was derived. HepR21 has been shown to have increased proliferation rate than HepG2, intracellular HA cable formation and enhanced tumor potency without any significant alteration of intracellular ROS. In this paper we have observed that HepR21 cells containing higher endogenous HA levels, have downregulated expression of the autophagic marker, MAP-LC3, consistent with unaltered levels of endogenous ROS. In fact, HepR21 cells seem to have significant resistance to exogenous ROS stimuli and glutathione depletion. HepR21 cells were also found to be more resilient to nutrient starvation in comparison to its parent cell line. Decline in intracellular HA levels and HA cables in HepR21 cells upon treatment with HAS inhibitor (4-MU), induced a surge in ROS levels leading to increased expression of MAP-LC3 and tumor suppressors Beclin 1 and PTEN. This suggests the importance of HABP1 induced HA cable formation in enhancing tumor potency by maintaining the oxidant levels and subsequent autophagic vacuolation.

Bronchial epithelial injury in the context of alloimmunity promotes lymphocytic bronchiolitis through hyaluronan expression.

Epithelial injury is often detected in lung allografts, however, its relation to rejection pathogenesis is unknown. We hypothesized that sterile epithelial injury can lead to alloimmune activation in the lung. We performed adoptive transfer of mismatched splenocytes into recombinant activating gene 1 (Rag1)-deficient mice to induce an alloimmune status and then exposed these mice to naphthalene to induce sterile epithelial injury. We evaluated lungs for presence of alloimmune lung injury, endoplasmic reticulum (ER) stress, and hyaluronan expression, examined the effect of ER stress induction on hyaluronan expression and lymphocyte trapping by bronchial epithelia in vitro, and examined airways from patients with bronchiolitis obliterans syndrome and normal controls histologically. We found that Rag1-deficient mice that received mismatched splenocytes and naphthalene injection displayed bronchial epithelial ER stress, peribronchial hyaluronan expression, and lymphocytic bronchitis. Bronchial epithelial ER stress led to the expression of lymphocyte-trapping hyaluronan cables in vitro. Blockade of hyaluronan binding ameliorated naphthalene-induced lymphocytic bronchitis. ER stress was present histologically in >40% of bronchial epithelia of BOS patients and associated with subepithelial hyaluronan deposition. We conclude that sterile bronchial epithelial injury in the context of alloimmunity can lead to sustained ER stress and promote allograft rejection through hyaluronan expression.

Hyaluronan rafts in airway epithelial cells (1007.6)

Hyaluronan (HA) is a linear, non‐sulfated glycosaminoglycan that is normally formed as a unmodified structure but uniquely modified during inflammation. This modification involves the transfer of heavy chains (HC) from IαI to form HC‐HA complexes mediated by TSG‐6. These complexes are identified in bronchial secretions from asthmatics that also show an up‐regulation in their pulmonary TSG‐6 expression. HC‐HA matrices are leukocyte adhesive as demonstrated in many other pathological conditions including idiopathic arterial pulmonary hypertension, asthma and cystic fibrosis. In all cell types studied to date, the leukocyte‐adhesive HA cables synthesized by these cells remain attached to the cell surface. However, while airway epithelial cells (AECs) also form HA cables on their cell surface in response to a variety of inflammatory stimuli, we have identified that they can also actively release a majority of their leukocyte‐adhesive HA structures into the extracellular space from their apical surface even when cells are not treated with inflammatory stimuli. These matrices do not resemble the rope‐like HA cables, but occur in distinct clumps or rafts of HA that can capture and embed leukocytes from cell suspensions. Not only were these leukocyte adhesive structures observed in vitro but also in the bronchoalveolar lavage of naïve mice. Furthermore, we have been able to identify the synthesis of heavy chain 3, previously reported to be constitutively expressed by human proximal tubular epithelial cells as urinary trypsin inhibitor (UTI), which may directly contribute to heavy chain modification of the HA matrix in lung inflammation. This provides evidence that AECs can manufacture their own HC‐donor. By characterizing the structure of these cell‐free HA rafts, the mechanism by which they are synthesized and their effect on leukocyte activation and behavior, we will have a better understanding of their role in human health and disease.

A silk fibroin based hepatocarcinoma model and the assessment of the drug response in hyaluronan-binding protein 1 overexpressed HepG2 cells

Microenvironment around tumor cells plays an important role in its malignancy or invasiveness. Hyaluronan (HA), a major component of extracellular matrix is found to be elevated in most of cancerous niche/microenvironment and performs regulatory role in the progression of tumors and metastasis. Overexpression of the hyaladherin, hyaluronan-binding protein 1 (HABP1) in the hepatocarcinoma cells (HepG2) termed as HepR21 leads to enhanced cell proliferation with increased HA ‘pool’ associated with HA ‘cables’ indicating elevated tumorous potential under 2D culture conditions. For in vitro experimentation, scaffold based three dimensional niche modeling may have greater acceptance than conventional 2D culture condition. Thus, we have examined the influence of intrinsic properties of non-mulberry tropical tasar silk fibroin on the HepR21 cells in order to develop a 3D hepatocarcinoma construction to act as model. The scaffold of tasar silk fibroin of Antheraea mylitta when efficiently loaded with transformed hepatocarcinoma cells, HepR21; exhibits enhanced adhesiveness, viability, metabolic activity, proliferation and enlarged cellular morphology in 3D compared to its parent cell line HepG2, supporting the earlier observation made in 2D system. In addition, formation of multicellular aggregates, the indicator of tumor progression is also revealed in silk based 3D culture conditions. Further, the use of 4-MU (a hyaluronan synthase inhibitor) on HepR21 cells reduces the HA level and downregulates the expression of growth promoting factors like pAKT and PKC; while upregulating the expression of the tumor suppressor p53. Thus, 4-MU efficiently reduces the tumor potency associated with increased HA pool as well as HA cables and the effect of 4-MU doubling up as an anticancer agent in 2D and 3D are also comparable. The in vitro 3D multicellular model demonstrates the insight of hepatocarcinoma progression and offers the predictability of cellular response to transfection efficacy, drug treatment and therapeutic intervention.

Tumor Necrosis Factor-stimulated Gene-6 (TSG-6) Amplifies Hyaluronan Synthesis by Airway Smooth Muscle Cells

We tested the hypothesis that the artificial addition of heavy chains from inter-α-inhibitor to hyaluronan (HA), by adding recombinant TSG-6 (TNF-stimulated gene-6) to the culture medium of murine airway smooth muscle (MASM) cells, would enhance leukocyte binding to HA cables produced in response to poly(I:C). As predicted, the addition of heavy chains to HA cables enhanced leukocyte adhesion to these cables, but it also had several unexpected effects. (i) It produced thicker, more pronounced HA cables. (ii) It increased the accumulation of HA in the cell-associated matrix. (iii) It decreased the amount of HA in the conditioned medium. Importantly, these effects were observed only when TSG-6 was administered in the presence of poly(I:C), and TSG-6 did not exert any effect on its own. Increased HA synthesis occurred during active, poly(I:C)-induced HA synthesis and did not occur when TSG-6 was added after poly(I:C)-induced HA synthesis was complete. MASM cells derived from TSG-6(-/-), HAS1/3(-/-), and CD44(-/-) mice amplified HA synthesis in response to poly(I:C) + TSG-6 in a manner similar to WT MASM cells, demonstrating that they are expendable in this process. We conclude that TSG-6 increases the accumulation of HA in the cell-associated matrix, partially by preventing its dissolution from the cell-associated matrix into the conditioned medium, but primarily by inducing HA synthesis.

Melanoma cell-derived factors stimulate hyaluronan synthesis in dermal fibroblasts by upregulating HAS2 through PDGFR-PI3K-AKT and p38 signaling

In many cancers hyaluronan content is increased, either by tumor cells or the surrounding stromal cells and this increased hyaluronan content correlates with unfavorable clinical prognosis. In the present work, we studied the effects of melanoma cell (aggressive melanoma cell line C8161)-derived factors on fibroblast hyaluronan synthesis, intracellular signaling, MMP expression and invasion. Treatment of the fibroblast cultures with melanoma cell conditioned medium (CM) caused accumulation of hyaluronan in the culture medium and formation of thick pericellular hyaluronan coat and hyaluronan cables. The expression of Has2 was increased approximately 20-fold by the C8161 melanoma cell CM, while Has1 and Has3 were increased twofold. Knock-down of Has2 expression with siRNA showed that Has2 was responsible for the increased hyaluronan synthesis induced by the melanoma cell CM. To find out the signaling routes, which led to Has2 upregulation, the phosphorylation profiles of 46 kinases were screened with phosphokinase array kit. Melanoma cell CM treatment strongly induced a rapid phosphorylation of p38, JNK, AKT, CREB, HSP27, STAT3 and cJUN. Treatment of the fibroblasts with specific inhibitors of PI3K, AKT and p38 reduced the melanoma cell CM-induced hyaluronan secretion, while the inhibitor of PDGFR totally blocked it. In addition, siRNA for PDGFRα/β inhibited Has2 upregulation in melanoma cell CM-treated fibroblasts. In parallel with the increased hyaluronan synthesis the melanoma cell CM-treated fibroblasts showed spindle shape, numerous long cell protrusions, enhanced MMP expression and increased invasion into collagen-Cultrex matrix. siRNA blocking of Has2 or PDGFRα/β expression reversed the stimulatory effect of melanoma cell CM on fibroblast invasion. PDGF secreted by melanoma cells thus mediated fibroblasts activation, with HAS2 upregulation as a major factor in the fibroblast response. This effect on stromal matrix is suggested to favor tumor growth.

Tumour necrosis factor-stimulated gene (TSG)-6 controls epithelial–mesenchymal transition of proximal tubular epithelial cells

Progressive renal disease is characterized by accumulation of extracellular matrix in the renal cortex. Proximal tubular cells (PTC) may contribute to disease through a process of epithelial–mesenchymal-transition (EMT): phenotypic change, disruption of the tubular basement membrane and migration into the interstitium. Hyaluronan (HA) synthesis and its extracellular organization by hyaladherins affect cell fate in other systems: this study investigated the role of the hyaladherin, tumour necrosis factor-stimulated gene (TSG)-6, in PTC EMT triggered in vitro by transforming growth factor (TGF)β1. TGFβ1 triggered the loss of PTC epithelial phenotype with 60% decreased expression of E-cadherin and 2–3-fold induction of alpha-smooth muscle actin (α-sma). It also increased the expression of TSG-6, HA-synthase-(HAS)2 and the HA-receptor, CD44, to a peak at 8–12 h, remaining elevated thereafter. Immuno-localization of HA demonstrated that unstimulated PTC assembled HA in cables and that treatment with TGFβ1 initiated cable disassembly with formation of dense HA-pericellular coats. Stable knockdown of TSG-6 with short-hairpin-RNA increased E-cadherin and HAS2 expression, produced loose HA-pericellular coats, HA cables were absent and cell migration was slowed. Treatment of transfectants with TGFβ1 did not induce α-sma, alter E-cadherin, pericellular-HA or migration but did induce HAS2. This was dependent on the expression of CD44 and was inhibited by CD44-specific siRNA. In summary, TSG-6 was central to EMT through effects on HA macromolecular structure and through CD44-dependent triggering of cell responses. These findings suggest that controlling the assembly of HA by proximal tubular cells may be a novel approach towards intervention in renal disease.

Inhibition of the Phosphatidylinositol-3-Kinase Pathway Abrogates Polyinosinic:Polycytidylic Acid–Stimulated Hyaluronan-Mediated Human Mucosal Smooth Muscle Cell Binding of U937 Monocytic Cells

The origin of inflammatory bowel disease (IBD) is unknown and likely to be multifactorial. Our laboratory has established that in human mucosal smooth muscle cells (M-SMCs), cellular stress induced by virus or the viral mimic double-stranded RNA (polyinosinic:polycytidylic acid [poly I:C]) increases cell surface hyaluronan (HA) deposition and the formation of long cable-like structures of HA that are important for leukocyte attachment. Since leukocyte accumulation and hyperplasia of the M-SMCs are characteristic pathological changes observed in IBD patients, and phosphatidylinositol-3-kinase (PI3K)/Akt signaling pathways play established roles in cell survival, we investigated whether this pathway is involved in this unique HA-mediated leukocyte attachment. Poly I:C-stimulated M-SMCs bind significantly more monocytic cells than untreated cells and this response was inhibited in a dose-dependent manner by treatment with the PI3K inhibitor, LY294002. Since Akt is a critical downstream regulator of PI3K, we investigated the phosphorylation status of Akt in M-SMCs after treatment with poly I:C for 1 h and found that Akt was phosphorylated, but the phosphorylated Akt band was undetectable in LY294002 plus poly I:C-treated cultures. Confocal microscopy of M-SMCs stained for HA revealed that HA cable formation after poly I:C treatment was abrogated by LY294002. These results demonstrate that poly I:C-stimulated M-SMCs phosphorylate Akt, produce HA cables, and promote HA-mediated leukocyte adhesion through a PI3K/Akt-dependent manner.

Airway Smooth Muscle Cells Synthesize Hyaluronan Cable Structures Independent of Inter-α-inhibitor Heavy Chain Attachment

The covalent association of inter-alpha-inhibitor-derived heavy chains (HCs) with hyaluronan was first described in synovial fluid from arthritic patients and later described as a structural and functional component of hyaluronan "cable" structures produced by many different cells and stimuli. HC transfer has been shown to be mediated by the protein product of TSG-6 (tumor necrosis factor-stimulated gene 6). Considering the accumulation of hyaluronan in airways following asthmatic attacks and the subsequent infiltration of leukocytes, we sought to characterize HC substitution of hyaluronan "cables" in primary mouse airway smooth muscle cells (MASM) and primary human airway smooth muscle cells (HASM). We found that cells derived from mice lacking TSG-6 had no defect in hyaluronan production or hyaluronan-mediated leukocyte adhesion when treated with the viral mimic poly(I,C). Functional hyaluronan cables were induced by cycloheximide in the confirmed absence of protein synthesis, with or without simultaneous treatment with poly(I,C). We characterized the species specificity of the antibody other investigators used to describe the HC-hyaluronan complex of hyaluronan cables and found minimal affinity to bovine-derived HCs in contrast to HCs from mouse and human sera. Thus, we cultured MASM and HASM cells in serum from these three sources and analyzed hyaluronan extracts for HCs and other hyaluronan-binding proteins, using parallel cumulus cell-oocyte complex (COC) extracts as positive controls. We conclude that, if hyaluronan cables derived from MASM and HASM cells are substituted with HCs, the amount of substitution is significantly below the limit of detection when compared with COC extracts of similar hyaluronan mass.

Induction of Hyaluronan Cables and Monocyte Adherence in Epidermal Keratinocytes

Hyaluronan attached to cell surface can form at least two very different structures; a pericellular coat close to plasma membrane and hyaluronan chains coalesced into “cables” that can span several cell lengths. The hyaluronan in cables, induced by many inflammatory agents, can bind leukocytes, whereas that in the pericellular coat does not contribute to leukocyte binding. Therefore, this structural change seems to have a major role in inflammation. In the present study we checked whether cells of squamous epithelium, like epidermal keratinocytes, can form hyaluronan cables and bind leukocytes. In addition, we checked whether hyaluronan synthesis is affected during the induction of cables. Control keratinocytes expressed pericellular hyaluronan as small patches on plasma membrane. But when treated with inflammatory agents or stressful conditions (tunicamycin, interleukin-1β, tumor necrosis factor-α, and high glucose concentration), hyaluronan organization changed into cable-like structures that avidly bound monocytes. Simultaneously, the total amount of secreted hyaluronan was slightly decreased, and the expression levels of hyaluronan synthases (Has1–3) and CD44 were not significantly changed. The results show that epidermal keratinocytes can form cables and bind leukocytes under inflammatory provocation and that these effects are not dependent on stimulation of hyaluronan secretion.

Characterization of hyaluronan cable structure and function in renal proximal tubular epithelial cells

Alteration in the glycosaminoglycan hyaluronan (HA) has been demonstrated in numerous renal diseases. We have demonstrated that renal proximal tubular epithelial cells (PTCs) surround themselves in vitro with HA in an organized pericellular matrix or 'coat', which is associated with cell migration, and also form pericellular HA cable-like structures which modulate PTC-mononuclear leukocytes interactions. The aim of this study was to characterize potential regulatory mechanism in the assembly of PTC-HA into pericellular cables. HA cables are generated by PTCs in the absence of serum. Immunohistochemical analysis demonstrates the incorporation of components of the inter-alpha-inhibitor (IalphaI) family of proteins and versican into HA cables. Addition of an antibody to IalphaI/PalphaI (pre-alpha-inhibitor) inhibits cable formation. In contrast, inhibition of tumor necrosis factor-alpha-stimulated gene 6 (TSG-6) has no effect on cable formation, suggesting that their generation is independent of the known heavy-chain transfer activity of TSG-6. Overexpression of HAS3 is associated with induction of HA cable formation, and also increased incorporation of HA into pericellular coats. Functionally, this resulted in enhanced HA-dependent monocyte binding and cell migration, respectively. Cell surface expression of CD44 and trypsin-released cell-associated HA were increased in HAS3-overexpressing cells. In addition, hyaluronidase (hyal1 and hyal2) and bikunin mRNA expression were increased, whereas PalphaI HC3 mRNA expression was unchanged in the transfected cells. The data demonstrate the importance of IalphaI/PalphaI in cable formation and suggest that expression of HAS3 may be critical for HA cable assembly.

Hyaluronan: a simple polysaccharide with structural plasticity and functional diversity

Hyaluronan (HA) is a high‐molecular weight glycosaminoglycan that is involved in an extracellular matrix (ECM) organization and cell adhesion, essential to a wide range of normal physiological processes (e.g. development, immunology and reproduction). Its diverse biological activities may seem surprising for a simple linear polysaccharide composed solely of a repeating disaccharide of glucuronic acid and N‐acetylglucosamine. However, HA is likely to be able to take up many different conformational states, which are transient and rapidly interchanging in solution (Day & Sheehan 2001). It has been suggested that the interaction of HA with different HA‐binding proteins (hyaladherins) may stabilize particular conformations of the polysaccharide leading to HA‐protein complexes with distinct architectures and unique biological properties (Day & Sheehan 2001). Consistent with this hypothesis, recent studies on TSG‐6 (Blundell et al. 2003) and CD44 (Teriete et al. 2004) and molecular modelling of other members of the Link module superfamily reveal significant structural diversity in the HA‐binding domains in these related hyaladherins. Furthermore, there is evidence emerging that the complexes formed between polymeric HA and proteins can exhibit a wide range of higher order structures depending on the hyaladherin(s) involved. In some cases, these complexes may play mainly a structural role in ECM (e.g. the link protein/aggrecan/HA aggregates that provide load bearing function to cartilage), while in other cases they act as cell binding/activation sites (e.g. HA cables formed during inflammation). There is evidence that the function of HA can be modulated by its interaction with proteins. For example, preincubation of HA with TSG‐6 enhances/induces the binding of HA to cell surface CD44 on constitutive/inducible lymphocyte backgrounds (Lesley et al.); these activities are probably caused by the formation of cross‐linked HA fibrils that lead to receptor clustering. HA can also become modified by the covalent attachment of heavy chains (HCs), derived from the interα‐inhibitor, where TSG‐6 plays an essential role in this process (Mukhopadhyay et al.); this reaction is critical for the formation of a HA‐rich ECM required for successful ovulation and fertilization. HC‐HA complexes are also formed during inflammation but their function is not yet clear.