Selective solubilization of hyaluronic acid from fibroblast substratum adhesion sites

Final report of the safety assessment of hyaluronic acid, potassium hyaluronate, and sodium hyaluronate

Hyaluronic acid, sodium hyaluronate, and potassium hyaluronate function in cosmetics as skin conditioning agents at concentrations up to 2%. Hyaluronic acid, primarily obtained from bacterial fermentation and rooster combs, does penetrate to the dermis. Hyaluronic acid was not toxic in a wide range of acute animal toxicity studies, over several species and with different exposure routes. Hyaluronic acid was not immunogenic, nor was it a sensitizer in animal studies. Hyaluronic acid was not a reproductive or developmental toxicant. Hyaluronic acid was not genotoxic. Hyaluronic acid likely does not play a causal role in cancer metastasis; rather, increased expression of hyaluronic acid genes may be a consequence of metastatic growth. Widespread clinical use of hyaluronic acid, primarily by injection, has been free of significant adverse reactions. Hyaluronic acid and its sodium and potassium salts are considered safe for use in cosmetics as described in the safety assessment.

The effect of hyaluronate and its oligosaccharides on endothelial cell proliferation and monolayer integrity

Hyaluronidase treatment of hyaluronic acid produced a series of oligosaccharides. Those between 3 and 16 disaccharides in length stimulated angiogenesis in vivo and the proliferation of tissue cultured endothelial cells in vitro. This effect appears to be cell type specific, as no stimulation of fibroblasts or smooth muscle cells was observed. Endothelial cells were found to endocytose both high- and low-molecular-mass hyaluronate, which might be receptor mediated. Fibroblasts and smooth muscle cells, cultured under the same conditions, showed negligible uptake of hyaluronate. Thus, the cell-specific effects may be due to the differences in internalization of hyaluronate. High-molecular-weight hyaluronate both inhibited endothelial cell proliferation and disrupted newly formed monolayers. These data are consistent with the ability of hyaluronate to inhibit new blood vessel formation in vivo and also suggest that hyaluronate metabolism plays a pivotal role in the regulation of angiogenesis.

Heparan sulfate proteoglycans in the substratum adhesion sites of human neuroblastoma cells: modulation of affinity binding to fibronectin

Tissue culture substratum adhesion sites from EGTA-detached Platt human neuroblastoma cells were extracted with a buffer containing ocytlglucoside, NaCl, guanidine hydrochloride, and a variety of protease inhibitors, an extraction which resulted in quantitative solubilization of the 35SO4 = -radiolabeled proteoglycans and 3H-leucine-radiolabeled proteins. Of the sulfate-radiolabeled material, the vast majority was heparan sulfate proteoglycan (Kav = 0.15 on Sepharose C14B columns) and the remainder was chondroitin sulfate chains (no single chains of heparan sulfate were observed). This extract was then fractionated on DEAE-Sephadex columns under two different buffer elution conditions. Under DEAE-I conditions in low ionic strength acetate buffer, two major peaks of 35SO4 = -radiolabeled material (A,B) and a minor peak (C) could be resolved in the NaCl gradient; however, three-fourths of the material required 4 M guanidine hydrochloride to elute it from the column (peak D). Under DEAE-II conditions in acetate buffer supplemented with 8 M urea, the vast majority of the proteoglycan material could be eluted in the NaCl gradient as peak AB. Peak D material was shown to contain aggregated proteoglycan, along with nonproteoglycan protein, which high concentrations of urea or guanidine could dissociate, but not nonionic or zwitterionic detergents. Three different affinity chromatography systems were used to further characterize these components. Approximately 60% of peak A heparan sulfate proteoglycan from DEAE-I binds to the hydrophobic matrix, octyl-Sepharose, while 80% of the proteoglycan in DEAE-I peak D binds to this hydrophobic column. A sizable fraction of peak A proteoglycan fails to bind to plasma fibronectin but does bind to platelet factor-4 affinity columns. In contrast, peak AB proteoglycan from DEAE-II columns yields a much higher proportion of molecules which do bind to fibronectin. To examine the basis for these differences in affinity binding, nonproteoglycan protein from these adhesion sites was mixed with peak AB proteoglycan prior to affinity chromatography; proteoglycan binding to fibronectin decreased markedly while binding to platelet factor-4 was unaffected. This modulating activity involves the binding of nonproteoglycan protein in adhesion site extracts to both fibronectin on the column, as well as to heparan sulfate proteoglycan itself, and it could not be mimicked by a number of known proteins in adhesion site extracts or several other proteins. These results demonstrate selectivity and specificity in this modulation and indicate that a previously unidentified protein(s) is responsible.(ABSTRACT TRUNCATED AT 400 WORDS)

Structural characterization of heparan sulfate proteoglycan subclasses isolated from bovine aortic endothelial cell cultures

Labeled heparan sulfate proteoglycans (HSPG) were isolated from wounded and confluent cultures of bovine aortic endothelial cells by nondegradative extraction with 4 M guanidine hydrochloride and detergent. HSPG were separated from more highly charged chondroitin or dermatan sulfate proteoglycans by ion-exchange chromatography, and subclasses of different hydrodynamic size were isolated by gel filtration. Three major subclasses of HSPG were characterized structurally with respect to the presence and relative size of protein core, the presence and amount of nonsulfated oligosaccharide, and size and structure of heparan sulfate (HS) chains. The largest (600-800-kDa) HSPG subclass (I), isolated from cell layers and media of confluent cultures, bears 38-kDa HS chains on an apparently heterogeneous class of relatively large glycoprotein cores. HSPG II (150-200 kDa), isolated from cell layer or media, has 22-kDa HS chains and smaller core glycoproteins (less than 50 kDa). HSPG III, the subclass of smallest hydrodynamic size, has 13-kDa HS chains and a glycopeptide core of less than 15 kDa. All subclasses bear varying proportions of non-sulfated oligosaccharides of similar sizes. Comparisons of HS chain structure indicated that the different subclasses have similar proportions (49-55%) of N-sulfate, with both O-sulfate and highly N-sulfated blocks of disaccharide distributed similarly along HS chains. In addition, HS chains from subclasses II and III contain sequences that are insensitive to periodate oxidation or heparitinase digestion, suggesting that they contain increased proportions of iduronate.(ABSTRACT TRUNCATED AT 250 WORDS)

Focal adhesions and cell-matrix interactions

Focal adhesions are areas of cell surfaces where specializations of cytoskeletal, membrane and extracellular components combine to produce stable cell-matrix interactions. The morphology of these adhesions and the components identified in them are discussed together with possible mechanisms of their formation.

The role of hyaluronic acid in joint stability--a hypothesis for hip dysplasia and allied disorders

The concentration of hyaluronic acid (HA) and proteins in synovial fluids of hip and shoulder joints of a variety of canine breeds has been investigated. In the Australian Kelpie, a working dog with a low incidence of hip dysplasia, shoulder synovial fluid viscosity and HA concentration were higher than in similar joints of Alsatians in which hip dysplasia is relatively common. Moreover, the HA levels and viscosity in shoulder fluids of animals with clinically defined hip dysplasia were substantially lower than in all other breeds studied. On the basis of these findings, we propose that hip dysplasia and other joint abnormalities may arise as a consequence of a deficiency in the levels of HA in synovial fluids.

Biochemistry of hyaluronan

Hyaluronan (hyaluronic acid) is a linear polysaccharide formed from disaccharide units containing N-acetylglucosamine and glucuronic acid. It is ubiquitously distributed in the organism but is found in the highest concentrations in soft connective tissues. The molecular weight of hyaluronan is usually in the order of 10(6) to 10(7). Due to hydrogen bonding, the chain is rather stiff and the molecule behaves in solution as an extended, randomly kinked coil. Molecules of hyaluronan start to entangle already at concentrations of less than 1 g/l and form a continuous polymer network. Some of the functions of the polysaccharide have been connected with the unique physical chemical characteristics of the network such as its rheological properties, flow resistance, osmotic pressure, exclusion properties and filter effect. Hyaluronan is synthesized in the cell membrane by adding monosaccharides to the reducing end of the chain. The precursors are UDP-glucuronic acid and UDP-N-acetylglucosamine. The polysaccharide grows out from the cell surface and it can be shown that fibroblasts, for example, surround themselves with a coat of hyaluronan. The rate of biosynthesis is regulated by various factors, such as growth factors, hormones, inflammatory mediators, etc. The responsible enzyme, hyaluronan synthase, is a phosphoprotein and the regulation of the synthetic rate is apparently via phosphorylation. The hyaluronan is at least partly carried by lymph flow from the tissues. Part of the material is taken up and degraded in the lymph nodes. Another part is carried to the general circulation and taken up in the endothelial cells in the liver sinusoids. These cells have specific receptors for hyaluronan, which also recognize chondroitin sulphate. The uptake in the liver of high-molecular weight hyaluronan is very efficient and its normal half-life in serum is only in the order of 2 to 5 min. The polysaccharide is rapidly degraded in the lysosomes to low-molecular weight products, lactate and acetate. The total turnover of hyaluronan in serum is in the order of 10-100 mg/24 h. The normal concentration of hyaluronan in serum is less than 100 micrograms/l with a mean of 30-40 micrograms/l. High serum levels have been noted in liver cirrhosis (impaired uptake in the liver) and rheumatoid arthritis (increased synthesis in the tissues). Hyaluronan has been shown to interact specifically with certain proteins and cell surfaces. It binds to proteoglycans in cartilage and other tissues and fills an important structural role in the organization of the extra-cellular matrix.(ABSTRACT TRUNCATED AT 400 WORDS)

Proteoglycans in the substratum adhesion sites of human papillary or reticular dermal fibroblasts. Aging in vivo or in vitro

Sulfate-radiolabeled proteoglycans (PG) have been characterized from the tissue culture substratum adhesion sites of two human dermal fibroblast subpopulations, papillary (PAP) or reticular (RET), to determine the consequences of aging of these cells either in vivo or in vitro upon properties of these cells: matrix interfacing molecules. Cells were isolated from a 1-day-old male infant (patient 5) and a 78-year-old male (patient 8) and, after longterm radiolabeling in culture, detached from the substratum by EGTA treatment. The substratum adhesion sites were then extracted with a mixture of 1% octylglucoside, 1 M NaCl, and 0.5 M guanidine hydrochloride (GdnHCl) in acetate buffer with various protease inhibitors; these reagents quantitatively solubilize PG from adhesion sites and can be readily removed to test biological activities. PAP adhesion sites contained significantly more free chains of glycosaminoglycan than the sites of RET cells. Fractionation on DEAE-Sepharose columns under two different sets of gradient elution conditions [DEAE-I in which only acetate buffer was used; or DEAE-II in which acetate buffers were supplemented with 8 M urea] identified two major classes of PG in both PAP and RET cells - heparan sulfate proteoglycan (HS-PG) and chondroitin, dermatan sulfate proteoglycans (CS, DS-PG) - with an increased proportion of HS-PG in cells which had aged in vivo or in vitro (late-passage cells also generate a low molecular weight component that resolves on these columns). On DEAE-I columns, 70-80% of the PG forms high molecular weight aggregates that require high concentrations of urea or GdnHCl for further fractionation (DEAE-II conditions). Subsequent fractionation of the two PG classes was performed using three affinity chromatography systems. On platelet factor-4 (PF4) Sepharose columns, the HS-PGs from all cells studied bound completely and eluted with considerable heterodispersity. The CS, DS-PGs from middle-passage cells bound completely to PF4 as well but gave a more homodisperse pattern of elution; in contrast, late-passage (in vitro-aged) adhesion sites contained CS, DS-PGs that were more heterodisperse and that contained a high-avidity class. On plasma fibronectin (pFN)-Sepharose columns, the HS-PGs of middle or late-passage cells bound completely and eluted with a homodisperse pattern; in contrast, the HS-PGs from in vivo-aged cells contained 15-20% of their molecules which failed to bind to the column and a small subset which bound with greater avidity.(ABSTRACT TRUNCATED AT 400 WORDS)

Heparan sulfate proteoglycans of human neuroblastoma cells: affinity fractionation on columns of platelet factor-4+

Human neuroblastoma cells (Platt) were detached from tissue culture substrata with a Ca2+ chelating agent, and then the suspended cells were extracted with a sodium dodecyl sulfate (SDS)-containing buffer to maximally solubilize their sulfate-radiolabeled proteoglycans. The majority of the high-molecular-weight material in these dissociative extracts was heparan sulfate proteoglycan, which resolves into two heterodisperse size classes upon gel filtration on columns of Sepharose CL4B. After removal of SDS from these extracts by hydrophobic chromatography on Sep-Pak C18 cartridges, extracts were further fractionated on various affinity matrices. All of the sulfate-radiolabeled material eluted as one peak from DEAE-Sephadex ion-exchange columns. In contrast, affinity fractionation on Sepharose columns derivatized with the heparan sulfate-binding protein, platelet factor-4, resolved three major and one minor subsets of these components. The nonbinding fraction contained some heparan sulfate proteoglycan and some chondroitin sulfate. The weak-binding fraction contained principally heparan sulfate proteoglycan, as well as a small amount of chondroitin sulfate proteoglycan; the gel-filtration properties of these proteoglycans before or after alkaline borohydride treatment indicated that they were small in size, containing perhaps 2 to 4 glycosaminoglycan chains. The high-affinity fraction eluted from platelet factor 4-Sepharose was composed entirely of "single-chain" heparan sulfate. A portion of the heparan sulfate proteoglycan of the original extract bound to the hydrophobic affinity matrix, octyl-Sepharose, and this hydrophobic proteoglycan partitioned into the nonbinding and weak-binding fractions of the platelet factor 4-Sepharose affinity columns. These studies reveal that the majority of the proteoglycan made by these neuronal cells in culture is of the heparan sulfate class, is small in size when compared to other characterized proteoglycans, and can be resolved into several overlapping subsets when fractionated on affinity matrices.

Proteoglycans and cell adhesion. Their putative role during tumorigenesis

In this review, evidence that proteoglycans are involved in cell adhesion and related behavior is considered, together with their putative role(s) during tumorigenesis. Proteoglycans are large, carboxylated and/or sulfated structures that interact with specific binding sites on cell surfaces. Their distribution and synthesis in tissues alter with the onset of tumorigenesis so that hyaluronic acid is generally increased and heparan sulfate decreased in the developing tumor and surrounding tissue. However, the precise role of proteoglycans during the tumorigenic process is far from clarified. Data suggest any putative roles will be related to the adhesive properties that these molecules confer to cells. Hyaluronic acid and chondroitin sulfate appear to be weakly adhesive molecules that may promote 'transformed' characteristics when they occur on cells in large amounts. These characteristics include reduced cell spreading, increased cell motility, as well as reduced contact inhibition. Consistent with such properties, neither hyaluronic acid nor chondroitin sulfate are localized in specialized adhesion sites such as focal or close contacts. In contrast, heparan sulfate is associated with increased cell-substratum adhesion and is involved in the spreading of cells onto fibronectin and other substrata. Its presence is generally associated with reduced motility and with a well-spread morphology. Unlike hyaluronate and chondroitin sulfate, heparan sulfate is found in specialized contacts. These adhesive properties of proteoglycans predict an instructive role in tumor development, and recent experiments have defined an involvement of these molecules in metastatic arrest. Additional studies utilizing invasive and metastatic tumor variants including tumor cells that employ different mechanisms to invade are required to clarify the role of proteoglycans in tumor progression.