Biomedical subjects

D Heinegård

Publications and source records attributed to D Heinegård.

At least 19 recordsLinked to original sources

PubMed1992

COMP (cartilage oligomeric matrix protein) is structurally related to the thrombospondins.

Cloning and sequence analysis of cartilage oligomeric matrix protein (COMP) cDNA, representing a cartilage pentameric protein, revealed a protein of 755 amino acid residues with a calculated molecular mass of 82,700 Da. Expression of the cDNA in COS cells showed that COMP is a homopolymer composed of five identical disulfide-linked subunits. COMP is homologous to the carboxyl-terminal half of thrombospondin, and the homologies include 89% and 54% of the residues in COMP and thrombospondin, respectively. The similarities are most pronounced in the carboxyl-terminal domains and in the calcium binding type 3 repeat domains in which about 60% of the amino acid residues are identical. In the type 2/epidermal growth factor repeat domains the two proteins contain 41% identical residues. The sequence of the amino-terminal 84-amino acid residues is unique for COMP. Comparison of the amino acid sequences in the type 2 and type 3 repeat domains of COMP and the thrombospondins shows that COMP is the product of a unique gene and not the result of an alternatively spliced thrombospondin gene.

Amino Acid Sequence↗

PubMed1992

Proteoglycans from the swarm rat chondrosarcoma. Structure of the aggregates extracted with associative and dissociative solvents as revealed by electron microscopy.

Proteoglycan aggregates were extracted from Swarm rat chondrosarcoma tissue in the native state and compared with proteoglycan aggregates isolated dissociatively with 4 M guanidine HCl. Purified aggregates were examined with a variety of electron microscopic techniques. In some cases they showed a structure of the central filament identical to that of the link-stabilized central filament observed in earlier experiments where the separated constituents were allowed to reconstitute (Mörgelin, M., Paulsson, M., Hardingham, T. E., Heinegård, D., and Engel, J. (1988) Biochem. J. 253, 175-185). The tight packing of proteoglycan monomers along the hyaluronate with a minimum distance of 12 nm between adjacent E1 strands also could thus be confirmed for never dissociated aggregates. The results therefore show that the organization of proteoglycan aggregates assembled in vitro from the participating molecules is representative for conditions in situ. An additional structural type of central filament was observed in the preparations. This contained long stretches of free hyaluronate interspaced by short stretches of central filament with condensed arrays of link protein-proteoglycan. Chemical cross-linking in combination with low shear electron microscopical techniques showed that this discontinuous central filament structure is not an artifact of specimen preparation. The addition of suprastoichiometric amounts of exogenous link protein did not affect the central filament structure with the low packing density. Densely and loosely packed types of central filament were isolated in varying relative amounts with different associative and dissociative solvents.

Animals↗

PubMed1992

Cartilage matrix proteins. An acidic oligomeric protein (COMP) detected only in cartilage.

An Mr = 524,000 oligomeric protein was isolated from bovine cartilage and designated COMP (Cartilage Oligomeric Matrix Protein). The protein is composed of disulfide-bonded subunits with an apparent Mr of 100,000 each. It is markedly anionic, probably due to its high contents of aspartic acid and glutamic acid, as well as to its substitution with negatively charged carbohydrates. COMP was found in all cartilages analyzed, but could not be detected in other tissues by enzyme-linked immunosorbent assay of guanidine HCl extracts. Within a given cartilage, COMP shows a preferential localization to the territorial matrix surrounding the chondrocytes.

Amino Acids↗

PubMed1992

Electron microscopy of native cartilage oligomeric matrix protein purified from the Swarm rat chondrosarcoma reveals a five-armed structure.

Cartilage oligomeric matrix protein was isolated in the native state from the Swarm rat chondrosarcoma. A crucial step was its selective extraction with EDTA-containing buffer. The purified protein was subjected to electron microscopy using rotary shadowing and negative stain. The images allowed the construction of a structural model. The bouquet-like protein consists of five 28-nm-long arms containing a peripheral globular domain, a flexible strand, and a central assembly domain, where the five arms meet in a cylindrical structure.

Animals↗

PubMed1992

Synovial fluid analysis of two groups of proteoglycan epitopes distinguishes early and late cartilage lesions.

OBJECTIVE: To investigate whether fragmentation of proteoglycans in arthritis results in domains that have different levels of release from cartilage at different stages of the disease. METHODS: Two regions of the proteoglycan, the hyaluronan-binding region and the glycosaminoglycan-rich region of the core protein, were measured, by immunoassay, in knee joint synovial fluids of patients with rheumatoid arthritis or reactive arthritis. RESULTS: Synovial fluid concentrations of the glycosaminoglycan-rich region were highest in rheumatoid arthritis patients who had little cartilage damage as determined by radiography, whereas release of the hyaluronan-binding region predominated in patients with advanced cartilage destruction. In reactive arthritis, release of the glycosaminoglycan-rich region predominated. CONCLUSION: These findings indicate that the hyaluronan-binding region is initially retained in the tissue during the development of cartilage destruction. The combined analysis of these markers offers a new avenue for assessment of the degree of cartilage damage in arthritis.

Adult↗

PubMed1992

RGD-directed attachment of isolated rat osteoclasts to osteopontin, bone sialoprotein, and fibronectin.

Osteoclasts isolated from the long bones of 5-day-old rats were seeded onto glass surfaces coated with osteopontin, bone sialoprotein, or fibronectin. Cell binding was promoted by all three proteins and inhibited in a dose-dependent manner by an RGD-containing peptide, while an RGE-containing peptide was ineffective. Immunocytochemistry of bone tissue showed enhanced concentration of osteopontin in bone opposite the clear zone of the osteoclasts, whereas immunolocalization of bone sialoprotein and fibronectin showed no accumulation on bone surfaces facing cells. The observations corroborate previous findings that the osteoclast is attached via an integrin to osteopontin on the bone surface. Although bone sialoprotein and fibronectin can mediate osteoclast binding in vitro, such a role in vivo is not supported by the immunocytochemical observations.

Amino Acid Sequence↗

PubMed1992

The contents of macromolecule solutes in flexor tendon sheath fluid and their relation to synovial fluid. A quantitative analysis.

The importance of synovial environment for minimal adhesion formation in flexor tendon healing has recently gained attention. Various techniques have been used to restore an injured synovial tendon sheath. Therefore a quantitative analysis of flexor tendon sheath fluid is of interest to increase our knowledge about the specific synovial milieu and to evaluate the success of different types of sheath reconstructions from a biochemical point of view. Samples of tendon sheath fluid from trigger digits and tendon sheaths containing ganglions have been assayed for contents of hyaluronic acid and proteins of different molecular weights. The results show concentrations of hyaluronate and several proteins similar to those in normal joint fluid. These results indicate that flexor tendon sheath fluid has a character similar to synovial fluid of joints and apparently has specific functions such as soft tissue lubrication and nutrition of avascular tendon tissue.

Adult↗

PubMed1992

A new method for sequence analysis of glycosaminoglycans from heavily substituted proteoglycans reveals non-random positioning of 4- and 6-O-sulphated N-acetylgalactosamine in aggrecan-derived chondroitin sulphate.

We have developed a new procedure for the sequence analysis of glycosaminoglycans, which is particularly suitable for the analysis of chains from heavily substituted proteoglycans. The procedure has been applied to various aggrecan-derived chondroitin sulphates. The glycans are released from the core protein by alkaline scission of the xylose-serine bond, subjected to reductive amination using p-aminobenzoic acid and finally radioiodinated at an acidic pH. Sequence analysis is performed by using various enzymic degradations, partial or complete, followed by high-resolution polyacrylamide gel electrophoresis, blotting and autoradiography to identify segments extending from the labelled reducing end to the point of cleavage. By using chondroitin C lyase to identify the location of 6-O-sulphated hexosamines, we find that chondroitin sulphate from tracheal cartilage has its 6-O-sulphated repeats concentrated to the extreme non-reducing terminal portion of the chain. In chondroitin sulphates derived from intervertebral discs (nucleus pulposus), the 6-O-sulphated repeats have a biphasic distribution; they occur mostly near the linkage region (i.e. the reducing end), but also in the non-reducing portion of the chain. Chondroitin sulphate from nasal cartilage, which is mostly 4-O-sulphated, displays considerable heterogeneity in the linkage region. Three or possibly more charge variants are observed.

4-Aminobenzoic Acid↗

PubMed1992

Cartilage oligomeric matrix protein: a novel marker of cartilage turnover detectable in synovial fluid and blood.

Cartilage oligomeric matrix protein (COMP) is a tissue specific non-collagenous matrix protein. We have developed an enzyme-linked immunosorbent assay for the detection of this protein in synovial fluid and serum. The protein has been quantified in these fluids in patients with rheumatoid arthritis (RA), reactive arthritis, juvenile chronic arthritis, osteoarthritis and in sera of control subjects. The protein was detectable in all fluids and the synovial fluid levels were always higher than in serum in paired samples. The highest knee joint synovial fluid levels were found in reactive arthritis patients and the lowest in RA patients with advanced destruction of the knee joint. However, the relative synovial fluid content of COMP was higher in these RA patients than in patients with advanced osteoarthritis. In patients with long-standing reactive synovitis the concentrations decreased. This decrease, however, was less marked than for proteoglycan concentrations. The serum concentrations were low in patients with juvenile chronic arthritis and in patients with RA with advanced cartilage destruction of the studied knee joint. In the other groups serum levels did not differ between groups or from controls.

Adult↗

PubMed1992

Cellular immunity to cartilage proteoglycans: relevance to the pathogenesis of ankylosing spondylitis.

Cellular immunity to cartilage proteoglycans may be responsible for sustaining chronic inflammation in ankylosing spondylitis. This hypothesis was examined by measuring peripheral blood and synovial fluid mononuclear cell proliferation in five preparations of human cartilage proteoglycan monomer in vitro. Peripheral blood mononuclear cells from 25 patients and synovial fluid mononuclear cells from five patients were compared with those from normal and disease control subjects matched for age. No significant differences were found between the three groups. This suggests that autoimmune responses to cartilage proteoglycans are unlikely to play a significant part in the pathogenesis of ankylosing spondylitis.

Adult↗

PubMed1992

Immunohistochemical localization of matrix proteins in the femoral joint cartilage of growing commercial pigs.

The immunocytochemical localization of several matrix macromolecules, including collagen type II and proteoglycans, in the distal femoral articular-epiphyseal cartilage complex of 15 commercial pigs between the age of 6 and 18 weeks was studied. Early osteochondrotic lesions, i.e., chondronecrosis in the resting region of the growth cartilage, as well as extensions of necrotic cartilage into the subchondral bone, were present in all animals, except those 6 weeks old. A battery of antibodies were used for identification of macromolecules in the matrix at different stages of the disease. Chondrocyte involvement in the process could be studied by identifying the sequence of alterations in matrix macromolecules as the lesion developed. The immunostaining for aggrecan (large aggregating proteoglycans), cartilage oligomeric matrix protein, fibronectin, collagen type II, fibromodulin, and biglycan was more prominent in the areas of chondronecrosis, extending into the subchondral bone, than in the normal resting region. This altered pattern of matrix macromolecules resembled that of the matrix of the proliferative chondrocytes and suggests that the chondrocyte maturation had stopped in the proliferative zone. The matrix in the areas of chondronecrosis in the resting region resembled that in the normal resting region. Thus the chondronecrosis appears to have preceded alterations of the matrix composition. The antibody reactivity pattern was, however, altered in the matrix of the clustered chondrocytes in areas of chondronecrosis. Staining in these regions suggested a more prominent appearance of fibronectin and collagen type II than in the normal matrix of the resting region. These changes are suggestive of attempt to repair.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Proteoglycan fragments in joint fluid. Influence of arthrosis and inflammation.

We determined the concentration of proteoglycan fragments in knee joint fluid collected from knee-ligament injured patients more than 6 months after the trauma and from patients with acute pyrophosphate arthritis and arthrosis or with arthrosis only. Injured patients with normal or only mildly altered cartilage at arthroscopy and with normal radiographs, had twice the average concentration of healthy volunteers. Other injured patients with advanced, radiographic signs of arthrosis, had synovial fluid proteoglycan fragment concentrations within the range of healthy volunteers. Patients with pyrophosphate arthritis had the highest concentrations, substantially increased compared with both arthrosis patients, with or without knee injury and healthy volunteers. Likewise, there was an inverse relation between the degree of arthrosis and the concentration of proteoglycan fragments in the joint fluid in patients with pyrophosphate arthritis and arthrosis or with arthrosis only. We conclude that synovial fluid levels of proteoglycan fragments are influenced by the mass of cartilage matrix remaining in the joint, the inflammatory activity in the joint, and the metabolic activity of the cartilage cells.

Adult↗

PubMed1991

Cartilage matrix proteins. A basic 36-kDa protein with a restricted distribution to cartilage and bone.

A non-collagenous quantitatively prominent protein was purified from guanidine hydrochloride extracts of bovine tracheal cartilage. Purification was achieved by cesium chloride density gradient centrifugation and chromatography on DEAE-cellulose at pH 7.0 followed by CM-cellulose at pH 5.0. The protein has a marked tendency to form aggregates in denaturing solutions of high ionic strength, e.g. 6 M guanidine hydrochloride. The purified protein contains a single, Mr 36,000 polypeptide chain, with a particularly high content of leucine. It contains about 1% carbohydrate with a remarkable absence of hexosamines and sialic acid, whereas xylose, galactose, mannose, and fucose were identified in the preparation. The protein was identified in extracts of cartilage and bone and could be shown to be primarily extracellular. Tendon may contain trace amounts of the protein, whereas extracts of several other tissues showed no immunoreactivity in enzyme-linked immunosorbent assay.

Animals↗

PubMed1991

Posttranslational modifications of fibromodulin.

Tyrosine sulfate residues were identified in fibromodulin produced by tracheal chondrocytes, by tendon and sclera fibroblasts in primary culture, as well as in Chinese hamster ovary cells transfected with a construct containing fibromodulin cDNA. The tyrosine sulfate residues were located in the N-terminal part of fibromodulin. Thus, Chinese hamster ovary cells expressing a deleted variant of fibromodulin lacking the N-terminal 52 amino acids following the predicted signal peptide did not contain any tyrosine sulfate residues. The substitution with keratan sulfate chains was not restricted to chondrocytes, but was also identified in fibromodulin synthesized by bovine tendon fibroblasts and sclera fibroblasts, as well as in fibromodulin isolated from tendon. Digestion of fibromodulin with N-glycosidase F reduced the apparent size of fibromodulin to that of the core protein, as predicted from sequence analysis (Oldberg, A., Antonsson, P., Lindblom, K., and Heinegård, D. (1989) EMBO J.8, 2601-2604). Thus fibromodulin from cartilage, tendon, and sclera contains N-glycosidically linked oligosaccharides, some of which are extended to keratan sulfate chains.

Animals↗

PubMed1991

Proteoglycan alterations during developing experimental osteoarthritis in a novel hip joint model.

Degenerative hip joint disease was induced in dogs by extra-articular surgery that created a condition that mimics hip dysplasia. Decreased acetabular coverage of the femoral head gave altered mechanical load, with ensuing cartilage degeneration. For comparison, degenerative knee joint disease was induced in other dogs by transection of the anterior cruciate ligament of the knee. The femoral head articular cartilage showed macroscopic signs of degeneration within a month. No macroscopical changes of synovitis were present. Chemical analysis of cartilage samples showed loss of proteoglycans. Guanidine hydrochloride extracts of the cartilage contained proteoglycan fragments that could be separated by equilibrium density gradient centrifugation in cesium chloride. The data indicate that proteoglycans are fragmented by proteolytic cleavage and lost from the cartilage. The proteoglycans remaining in the tissue are smaller and have lost the ability to aggregate with hyaluronic acid. Similarly, in experimental knee joint osteoarthritis, the proteoglycan content of the cartilage decreased. The structural changes of those proteoglycans remaining were of a different nature, with no changes in proteoglycan size or aggregation properties, possibly indicating that both degradation and repair took place in the knee articular cartilage and/or that fragments were rapidly lost from the tissue. This may follow from different surgical procedures, only the one used for the hip joint being extra-articular, or from the different anatomy and physiology of the hip joint and the knee joint.

Animals↗

PubMed1991

Fibronectin-immunoglobulin complexes in the early course of IgA and Henoch-Schönlein nephritis.

We have previously reported the presence of circulating IgA-fibronectin complexes in adult patients with primary IgA nephropathy. In the present study five children were serially investigated during the early course of IgA nephropathy and Henoch-Schönlein glomerulonephritis. Using affinity chromatography procedures and enzyme-linked immuno-sorbent assay, IgA, IgG and IgM in complex with fibronectin were repeatedly demonstrated during the follow-up period in both groups of patients. Most patients had, at the same time, IgA, IgG, as well as IgM deposits in the glomerular mesangium. The simultaneous presence of IgA and IgG in complexes purified from serum was furthermore demonstrated. The results are thus in contrast to the findings in adults with IgA nephropathy, in whom the immunoglobulin-fibronectin complexes only contained IgA. Whether this reflects different subgroups of patients or a different pathophysiology in children and adults remains to be elucidated.

Adolescent↗

PubMed1991

Computer-controlled mechanical testing machine for small samples of biological viscoelastic materials.

Time dependency in the mechanical properties of viscoelastic materials means that a variety of tests is often required to fully characterize their properties. Computer control is the best way of controlling loads and displacements and the rate at which they are applied, as well as recording and analysing the data produced. This paper describes apparatus for measuring the viscoelastic properties of articular cartilage in compression which is readily adaptable to any small sample in which accurate strain measurements require small, carefully controlled displacements. An IBM-type microcomputer is used to control a stepper motor driving a ball screw with a positional accuracy of about 1 micron.

Biomechanical Phenomena↗

PubMed1991

The synthesis of a family of structurally related proteoglycans in fibroblasts is differently regulated by TFG-beta.

Fibroblasts synthesize a variety of proteoglycans among which is a family of structurally related small proteoglycans, i.e. PG-S1 (biglycan) and PG-S2 (decorin). Fibromodulin, which is present in some tissues as a keratan sulfate proteoglycan, also belongs to this family. We have used primary fibroblasts from fetal skin and bovine sclera in culture to study the metabolism of proteoglycans. In particular the regulatory effect of transforming growth factor-beta (TGF-beta), interleukin-1 (IL-1) platelet-derived growth factor (PDGF) and dexamethasone was determined by studies of mRNA levels for these structurally related proteoglycans. Furthermore the synthesis and secretion of these macromolecules was studied using radioactive precursors. TGF-beta induced a 3-fold increase of mRNA for PG-S1, collagen I and III in both types of fibroblasts. mRNA for PG-S2 increased only slightly (1.7-fold) in human skin fibroblasts; while no effect was noticed in sclera fibroblasts. The expression of fibromodulin mRNA was not effected in any of the cells investigated. IL-1, PDGF and dexamethasone had no significant effects on the levels of proteoglycan and collagen mRNA, respectively. Synthesis and secretion of PG-S1, -S2 and fibromodulin wa studied by labeling with [3H]-leucine and [35S]-sulfate. Final separation of PG-S1 and -S2 was achieved by hydrophobic interaction chromatography. TGF-beta induced a 3- to 6-fold increase of [3H]- and [35S]-labeled PG-S1; while PG-S2 only increased 1.3- to 1.4-fold in both types of fibroblasts. No effect on synthesis and secretion of immunoprecipitated fibromodulin was noted.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗