A comparison of techniques for the quantitative analysis of hyaluronic acid in equine synovial fluid. (1/2907)

A comparison of methods of preparing the hyaluronic acid of equine synovial fluid for quantitative spectrophotographic analysis is presented. A new method is proposed which appears superior to the previous methods.  (+info)

LYVE-1, a new homologue of the CD44 glycoprotein, is a lymph-specific receptor for hyaluronan. (2/2907)

The extracellular matrix glycosaminoglycan hyaluronan (HA) is an abundant component of skin and mesenchymal tissues where it facilitates cell migration during wound healing, inflammation, and embryonic morphogenesis. Both during normal tissue homeostasis and particularly after tissue injury, HA is mobilized from these sites through lymphatic vessels to the lymph nodes where it is degraded before entering the circulation for rapid uptake by the liver. Currently, however, the identities of HA binding molecules which control this pathway are unknown. Here we describe the first such molecule, LYVE-1, which we have identified as a major receptor for HA on the lymph vessel wall. The deduced amino acid sequence of LYVE-1 predicts a 322-residue type I integral membrane polypeptide 41% similar to the CD44 HA receptor with a 212-residue extracellular domain containing a single Link module the prototypic HA binding domain of the Link protein superfamily. Like CD44, the LYVE-1 molecule binds both soluble and immobilized HA. However, unlike CD44, the LYVE-1 molecule colocalizes with HA on the luminal face of the lymph vessel wall and is completely absent from blood vessels. Hence, LYVE-1 is the first lymph-specific HA receptor to be characterized and is a uniquely powerful marker for lymph vessels themselves.  (+info)

CD44 cleavage induced by a membrane-associated metalloprotease plays a critical role in tumor cell migration. (3/2907)

CD44 is a cell surface receptor for hyaluronate, a component of the extracellular matrix (ECM). Although CD44 has been implicated in tumor invasion and metastasis, the molecular mechanisms remain to be elucidated. Here we find that CD44 expressed in cancer cells is cleaved at the membrane-proximal region of the ectodomain and the membrane-bound cleavage product can be detected using an antibody against the cytoplasmic domain of CD44. Furthermore, we report that CD44 cleavage is mediated by a membrane-associated metalloprotease expressed in cancer cells. A tissue inhibitor of metalloproteases-1 (TIMP-1), as well as metalloprotease inhibitors, inhibit CD44 cleavage in the cell-free assay. Contrary, serine protease inhibitors enhance CD44 cleavage, and the enhancement can be prevented by pretreatment with a metalloprotease inhibitor. Thus, CD44 cleavage is regulated by an intricate balance between some proteases and their inhibitors. Interestingly, treatment with the metalloprotease blocker 1,10-phenanthroline, which strongly prevent the CD44 cleavage, suppressed RERF-LC-OK lung cancer cell migration on a hyaluronate substrate, but not on several other substrates. These results suggest that CD44 cleavage plays a critical role in an efficient cell-detachment from a hyaluronate substrate during the cell migration and consequently promotes CD44-mediated cancer cell migration. Our present data indicate that CD44, not only ECM per se, is one of the targets of pericellular proteolysis involved in tumor invasion and metastasis.  (+info)

Blockade of type beta transforming growth factor signaling prevents liver fibrosis and dysfunction in the rat. (4/2907)

We eliminated type beta transforming growth factor (TGF-beta) signaling by adenovirus-mediated local expression of a dominant-negative type II TGF-beta receptor (AdCATbeta-TR) in the liver of rats treated with dimethylnitrosamine, a model of persistent liver fibrosis. In rats that received a single application of AdCATbeta-TR via the portal vein, liver fibrosis as assessed by histology and hydroxyproline content was markedly attenuated. All AdCATbeta-TR-treated rats remained alive, and their serum levels of hyaluronic acid and transaminases remained at low levels, whereas all the AdCATbeta-TR-untreated rats died of liver dysfunction. The results demonstrate that TGF-beta does play a central role in liver fibrogenesis and indicate clearly in a persistent fibrosis model that prevention of fibrosis by anti-TGF-beta intervention could be therapeutically useful.  (+info)

Overproduction of hyaluronan by expression of the hyaluronan synthase Has2 enhances anchorage-independent growth and tumorigenicity. (5/2907)

Hyaluronan (HA) has long been implicated in malignant transformation and tumor progression. However, due to the lack of molecular tools to directly manipulate production of HA, which does not require a core protein for its synthesis, our understanding of the role of HA in tumor cells has been largely circumstantial. In this study, we genetically manipulated the production of HA by transfection of a mammalian HA synthase Has2 into human HT1080 cells and examined the malignant phenotype of transfected cells. We found that increased production of HA promotes anchorage-independent growth and tumorigenicity of the cells. Has2-transfected cells formed greater numbers of colonies in semisolid medium. Tumors in nude mice derived from Has2-transfected cells grew more rapidly and were 2-4 times larger than those derived from control cells at termination of experiments. Histological and biochemical analyses of tumors revealed no significant differences in cell density and tissue structures between them, indicating that the larger size of the tumors was due to enhanced cell proliferation, not to increased accumulation of tumor stroma or increased angiogenesis. These results demonstrate that HA production by tumor cells per se promotes proliferation of these cells in tissues and provides direct evidence for the role of HA in tumorigenicity.  (+info)

Hyaluronan expression in gastric cancer cells is associated with local and nodal spread and reduced survival rate. (6/2907)

Hyaluronan (HA), an extracellular high-molecular-mass polysaccharide, is supposed to be involved in the growth and progression of malignant tumours. We studied the cellular expression of HA in 215 operated stage I-IV gastric cancer patients using a specific biotinylated probe. Most (93%) of the tumours showed HA staining in their parenchyma, whereas the stroma inside and around the tumour was stained in every case. When HA expression was compared with the clinical and histological features of the tumours, a strong staining intensity in the tumour parenchyma was found to be associated with deep tumour invasion (pT3 or 4) and with mixed type of Lauren. A high proportion of HA-positive cells of all neoplastic cells was significantly associated with deep tumour invasion, nodal metastasis, positive lymphatic invasion, poor differentiation grade, as well as with inferior prognosis in univariate survival analysis. However, in multivariate analysis, only pT, pN, and vascular and lymphatic invasion emerged as independent predictors of survival in gastric cancer. The results indicate that ectopic HA expression is a frequent feature of gastric adenocarcinoma, and is associated with tumour progression and poor survival rate.  (+info)

Formation of hyaluronan- and versican-rich pericellular matrix is required for proliferation and migration of vascular smooth muscle cells. (7/2907)

The accumulation of hyaluronan (HA) and the HA-binding proteoglycan versican around smooth muscle cells in lesions of atherosclerosis suggests that together these molecules play an important role in the events of atherogenesis. In this study we have examined the formation of HA- and versican-rich pericellular matrices by human aortic smooth muscle cells in vitro, using a particle-exclusion assay, and the role of the pericellular matrix in cell proliferation and migration. The structural dependence of the pericellular matrix on HA can be demonstrated by the complete removal of the matrix with Streptomyces hyaluronidase. The presence of versican in the pericellular matrix was confirmed immunocytochemically. By electron microscopy, the cell coat was seen as a tangled network of hyaluronidase-sensitive filaments decorated with ruthenium red-positive proteoglycan granules. Ninety percent of migrating cells in wounded cultures, and virtually all mitotic cells, displayed abundant HA- and versican-rich coats. Time-lapse video imaging revealed that HA- and versican-rich pericellular matrix formation is dynamic and rapid, and coordinated specifically with cell detachment and mitotic cell rounding. HA oligosaccharides, which inhibit the binding of HA to the cell surface and prevent pericellular matrix formation, significantly reduced proliferation and migration in response to platelet-derived growth factor, whereas larger HA fragments and high molecular weight HA had no effect. Treatment with HA oligosaccharides also led to changes in cell shape from a typical fusiform morphology to a more spread and flattened appearance. These data suggest that organization of HA- and versican-rich pericellular matrices may facilitate migration and mitosis by diminishing cell surface adhesivity and affecting cell shape through steric exclusion and the viscous properties of HA proteoglycan gels.  (+info)

Regulation of the apoptotic response to radiation damage in B cell development. (8/2907)

B lymphocyte precursor cells are ultrasensitive to DNA damage induced by irradiation and drugs and die by apoptosis at very low levels of exposure. Previous studies have shown that this high level sensitivity is p53-dependent, associated with very low level expression of Bcl-2 protein and can be reversed by expression of a bcl-2 transgene. We show here that transition from the pro-B to pre-B and then mature B cell stages of murine lymphopoiesis is accompanied by changes in proliferating cells in sensitivity to X-irradiation induced apoptosis and that this is paralleled by variation in the ratio of anti-(Bcl-2/Bcl-chiL) to pro-(Bax) apoptotic proteins. These are however not fixed or invariant features of developmental stage as they can be modulated by interactions via adhesive interactions with stromal cells, stromal proteins and growth factors. We interpret these data in the context of the stringent developmental regulation of clonal lymphopoiesis and the contingency programming of cells that have extensive proliferative potential with a very low threshold for apoptosis following DNA damage.  (+info)