Isolation and properties of chondroitin sulphates from bovine heart valves

Exogenous hyaluronic acid and chondroitin sulfate crosslinking treatment for increasing the amount and stability of glycosaminoglycans in bioprosthetic heart valves

Glutaraldehyde (GLUT) crosslinked bioprosthetic heart valves (BHVs) might fail due to progressive degradation and calcification. GLUT cannot stabilize glycosaminoglycans (GAGs), which are important for BHVs' life time. In this current study we developed a new BHVs preparation strategy using exogenous hyaluronic acid (HA)/chondroitin sulfate (CS) supplement and sodium trimetaphosphate (STP) crosslinking method. Exogenous HA and CS provide additional GAGs for pericardiums. STP could link two GAGs by reacting with hydroxyl groups in GAGs' repeating polysaccharides units. The feeding ratios of HA/CS were optimized. The GAGs content and long-term stability in vitro, biocompatibility, the in vivo GAGs stability and anti-calcification potential of GLUT/HA/CS and STP treated pericardiums were characterized. We demonstrated that GLUT/HA/CS and STP treated pericardiums had sufficiently increased GAGs' amount and stability and decreased calcification. This new exogenous hyaluronic acid/chondroitin sulfate supplement and sodium trimetaphosphate crosslinking strategy would be a promising method to make BHVs with better structural stability and anti-calcification properties.

Neomycin and pentagalloyl glucose enhanced cross-linking for elastin and glycosaminoglycans preservation in bioprosthetic heart valves

Glutaraldehyde cross-linked bioprosthetic heart valves fail within 12-15 years of implantation due to limited durability. Glutaraldehyde does not adequately stabilize extracellular matrix components such as glycosaminoglycans and elastin, and loss of these components could be a major cause of degeneration of valve after implantation. We have shown earlier that neomycin-based cross-linking stabilizes glycosaminoglycans in the tissue but fails to stabilize elastin component. Here, we report a new treatment where neomycin and pentagalloyl glucose (PGG) were incorporated into glutaraldehyde cross-linking neomycin-PGG-Glutaraldehyde (NPG) to stabilize both glycosaminoglycans and elastin in porcine aortic valves. In vitro studies demonstrated a marked increase in extracellular matrix stability against enzymatic degradation after cross-linking and 10 month storage in NPG group when compared to glutaraldehyde controls. Tensile properties showed increased lower elastic modulus in both radial and circumferential directions in NPG group as compared to glutaraldehyde, probably due to increased elastin stabilization with no changes in upper elastic modulus and extensibility. The enhanced extracellular matrix stability was further maintained in NPG-treated tissues after rat subdermal implantation for three weeks. NPG group also showed reduced calcification when compared to glutaraldehyde controls. We conclude that NPG cross-linking would be an excellent alternative to glutaraldehyde cross-linking of bioprosthetic heart valves to improve its durability.

Induction of chondroitin sulfate proteoglycan synthesis and secretion in lymphocytes and monocytes

The ability of mononuclear leukocytes to synthesize and secrete proteoglycans was evaluated. Using radiolabeling with H2 35SO4, it is shown that peripheral blood mononuclear cells (PBMC) and their major subpopulations (B cells, T cells, and monocytes), as well as mouse spleen cells, all secreted easily detectable proteoglycan. After 24-h labeling periods, 90% of macromolecular 35S could be detected in culture media. This material was primarily (greater than 95%) chondroitin-4-sulfate proteoglycan (CSPG). Production and secretion of CSPG could be stimulated more than 200% in PBMC and 300% in T cell populations by high concentrations of concanavalin A and phorbol 12-myristate-13-acetate; lipopolysaccharide induced a small (twofold) but reproducible increase in CSPG secretion by adherent mononuclear leukocytes. The CSPG secreted by PBMC was relatively small in size compared to chondrocyte CSPG (130,000 daltons vs. 2-4 million daltons) but possessed similar sizes of glycosaminoglycan chains and greater solubility in low ionic strength solutions. This sulfated polyanion, which was produced endogenously by leukocytes and was actively secreted, might function as a co-mediator or "second messenger" in certain immune responses.

Evidence for a mechanical coupling of glycoprotein microfibrils with collagen fibrils in Wharton's jelly

Wharton's jelly of human umbilical cord is known to contain hyaluronic acid and sulphated glycosaminoglycans (probably as proteoglycans) immobilized in an insoluble collagen fibril network. A secondary, independent, insoluble network based on glycoprotein microfibrils of 13 nm diameter and interpenetrated with the collagen network has now been found in amounts corresponding to 9% of the weight of collagen. Elastin, however, is absent. Tissue slices placed in physiological buffer swell to two-fold their in vivo volume. This is due to the influence of the polysaccharides since treatment with either testicular hyaluronidase, Streptomyces hyaluronidase or chondroitinase ABC, causes their quantitative removal and abolishes the swelling tendency of tissue. Tissue so treated remains close to its in vivo volume indicating that for this state the fibrillar network, overall, is in its relaxed unstressed configuration. Subsequent treatment with a protease causes the degradation of the glycoprotein microfibril network and a two-fold increase in tissue volume while treatment with bacterial collagenase, resulting in the solubilization of 46% of the collagen, causes only a slight deswelling. These results suggest that the unstressed configuration of the network system at the in vivo volume of tissue is due to the collagen network being held in compression by the microfibril network. With intact tissue protease digestion with trypsin, in addition, causes a preferential release of sulphated glycosaminoglycans. Hyaluronic acid, however, remains largely immobilized.

Proteoglycans of bovine periodontal ligament and skin. Occurrence of different hybrid-sulphated galactosaminoglycans in distinct proteoglycans

A proteoglycan purified from 4 M-guanidinium chloride extracts of bovine periodontal ligament closely resembled that of bovine skin, except for a rather lower protein content and a higher molecular weight (120 000 compared with about 90 000) by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. The latter difference was explained by the molecular weights (29 000 and 16 000) of the respective dermatan sulphate components, each of which was rich in L-iduronate (about 75% of the total hexuronate). Significant amounts of other glycosaminoglycans did not occur in these proteoglycans, which were homogenous on gel chromatography and agarose/polyacrylamide-gel electrophoresis. Polydispersity was observed in sedimentation equilibrium experiments, but proteolysis or self-association of the proteodermatan sulphates may have affected these results. Ligament proteoglycans that were almost completely extracted with 0.1 M-NaCl contained less protein of a completely different amino acid composition than the proteodermatan sulphates. They were heterogeneous in size but generally smaller than cartilage proteoglycans and L-iduronate was a component, comprising about 7% of the total hexuronate of the sulphated galactosaminoglycan chains. The latter consisted of two fractions differing in molecular weight, but a dermatan sulphate with a high L-iduronate content was not present. These proteoglycans had some resemblance to D-glucuronate-rich proteoglycans of other non-cartilaginous tissues. Such compounds, however, are difficult to categorize at present.

The collagen of heart valve

A hydroxylysine-rich type I collagen has been isolated from pepsin-digested porcine heart valve. The ratio of alpha1 to alpha2 in the isolated molecule was 2:1. The component alpha chains exhibited unusual chromatographic behavior in comparison to corresponding chains from human dermis and lathyritic rat skin collagen. The composition of component cyanogen bromide peptides identified the alpha chains as authentic type I chains and demonstrated hydroxylysine enrichment throughout the length of the chain. delta6-Dehydro-5,5'dihydroxylysinonorleucine, a collagen cross-link derived from two hydroxylysyl residues and ordinarily found in hard tissue collagens was found to be the predominant cross-link in heart valve.

Aging and the interstitial content of loose connective tissue. A brief note

The concentration of hyaluronic acid which is the fixed loose connective tissue component determining water and other potentials in the interstitium remains constant with age. Since the collagen fiber network in the native tissue state is unstressed, changes in collagen fiber morphology and in collagen content with age have no influence.

Comparative biochemistry of chondroitin sulphate-proteins of cartilage and notochord

Fragments that consisted mainly of two polysaccharide chains joined by a short polypeptide bridge (doublets) were prepared from chondroitin sulphate-proteins of lamprey, sturgeon, elasmobranch and ox connective tissues after hydrolysis with trypsin and chymotrypsin. Consideration of molecular parameters, compositions and behaviour on gel electrophoresis and density-gradient fractionation leads to a proposed parent structure for chondroitin sulphate-proteins. A single polypeptide chain of about 2000 amino acid residues contains alternating short and long repeating sequences. A short sequence consists of less than 10 amino acid residues with one N-terminal and one C-terminal serine residue, each of which carries a polysaccharide chain linked glycosidically to its hydroxyl group. This structure constitutes the doublet subunit. Some variation is introduced when the doublet subunit carries only a single polysaccharide chain. The long sequence contains about 35 amino acid residues and is subject to cleavage by trypsin and chymotrypsin. The main polypeptide is probably homologous in the vertebrate sub-phylum with strong conservation of structure suggested for the short sequence. However, polymorphism of polypeptide structures cannot be excluded.