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Age-related changes in protein-related epitopes of human articular-cartilage proteoglycans.

ABSTRACT: Monoclonal antibodies were prepared that recognize different age-related epitopes on proteoglycan subunits of high buoyant density isolated from human epiphysial and articular cartilages. Antibody EFG-4 (IgG1) recognizes a proteinase-sensitive segment associated with the core protein. Antibody BCD-4 (IgG1) reacts with keratan sulphate bound to core protein. Both epitopes are minimally expressed in foetal cartilage and increase with age after birth to become maximally expressed in adult cartilage by about 30 years of age. In contrast, monoclonal antibody alpha HFPG-846 (IgM) recognizes a core-protein-related epitope that is maximally expressed in young foetal cartilage, declines up to birth and thereafter and is almost absent after about 30 years of age. Antibody alpha HFPG-846 was used to isolate by immuno-affinity chromatography two subpopulations of proteoglycan subunits from a 16-year-old-human cartilage proteoglycan subunit preparation. Only the antibody-unbound population showed a significant reaction with antibodies EGF-4 and BCD-4. The amino acid and carbohydrate compositions of these proteoglycan fractions were different, and one (antibody-bound) resembled those of foetal and the other (antibody-unbound) resembled those of adult proteoglycans isolated from 24-27-week-old-foetal and 52-56-year-old-adult cartilage respectively. These observations demonstrate that human cartilages contain at least two chemically and immunochemically distinct populations of proteoglycans, the proportions and content of which are age-dependent. It is likely that these populations represent the products of different genes, though their heterogeneity may be compounded by the result of different post-translation modifications.

SUBMITTER: Glant TT

PROVIDER: S-EPMC1146787 | biostudies-other | 1986 May

REPOSITORIES: biostudies-other

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Project description:Proteoglycans were extracted from the articular cartilage of foetal, calf and adult bovine metacarpal-phalangeal joints with 4m-guanidinium chloride. After extraction, the high-density proteoglycans (PG-I fractions) were prepared by sedimentation in two sequential CsCl-density-gradient procedures [Swann, Powell & Sotman (1979) J. Biol. Chem.254, 945-954]. The PG-I fractions from foetal, calf and adult tissues accounted for 75%, 52% and 46% respectively of the extracted components. The glucosamine, galactose, N-acetylneuraminic acid and protein contents increased with age. The overall amino acid compositions of PG-I fractions were similar. Fractionation of PG-I-fraction samples on a Bio-Gel A-50m column indicated that the molecular weight decreased with age. The PG-I fractions were specifically (3)H-labelled by treatment with galactose oxidase followed by reduction with NaB(3)H(4). The (3)H radioactivity was incorporated into both galactose and galactosamine residues of different carbohydrate side chains. The elution profiles of alkaline borohydride-treated foetal, calf and adult PG-I-fraction samples on a Sepharose 6B column showed that the molecular weights of chondroitin sulphate chains were 13500, 12000 and 10500 in foetal, calf and adult tissues respectively. Fractionation of the alkaline borohydride-treated foetal, calf and adult PG-I-fraction samples and (3)H-labelled calf and adult PG-I-fraction samples on a Bio-Gel P-10 column showed that there was an inverse relationship between the low-molecular-weight O-linked oligosaccharides and the higher-molecular-weight sialic acid-containing constituents at different ages. The oligosaccharide components of foetal, calf and adult PG-I-fraction samples represented 79%, 69% and 36% respectively of the total sialic acid content of the proteoglycans. Similarly in the (3)H-labelled calf and adult samples 75% and 30% of the total radioactivity were present in the oligosaccharide components respectively. Digestion with chondroitinase AC-II and infrared analyses showed that the PG-I-fraction F and C samples contained primarily chondroitin 4-sulphate chains whereas PG-I-fraction sample A was 6-sulphated. These studies show that the major proteoglycans (PG-I fractions) in the articular cartilage of foetal, calf and adult animals differ in the content, types and structure of the chondroitin sulphate, keratan sulphate and oligosaccharide constituents. These changes in proteoglycan structure reflect the gross age-related changes in the chemical composition of the tissue.

Project description:Hui2014 - Age-related changes in articular cartilage This model is described in the article: Oxidative changes and signalling pathways are pivotal in initiating age-related changes in articular cartilage Wang Hui1, David A Young1, Andrew D Rowan1, Xin Xu2, Tim E Cawston1, Carole J Proctor1,3 Annals of the Rheumatic Diseases Abstract: Objective: To use a computational approach to investigate the cellular and extracellular matrix changes that occur with age in the knee joints of mice. Methods: Knee joints from an inbred C57/BL1/6 (ICRFa) mouse colony were harvested at 3–30?months of age. Sections were stained with H&E, Safranin-O, Picro-sirius red and antibodies to matrix metalloproteinase-13 (MMP-13), nitrotyrosine, LC-3B, Bcl-2, and cleaved type II collagen used for immunohistochemistry. Based on this and other data from the literature, a computer simulation model was built using the Systems Biology Markup Language using an iterative approach of data analysis and modelling. Individual parameters were subsequently altered to assess their effect on the model. Results: A progressive loss of cartilage matrix occurred with age. Nitrotyrosine, MMP-13 and anaplastic lymphoma kinase (ALK1) staining in cartilage increased with age with a concomitant decrease in LC-3B and Bcl-2. Stochastic simulations from the computational model showed a good agreement with these data, once transforming growth factor-? signalling via ALK1/ALK5 receptors was included. Oxidative stress and the interleukin 1 pathway were identified as key factors in driving the cartilage breakdown associated with ageing. Conclusions: A progressive loss of cartilage matrix and cellularity occurs with age. This is accompanied with increased levels of oxidative stress, apoptosis and MMP-13 and a decrease in chondrocyte autophagy. These changes explain the marked predisposition of joints to develop osteoarthritis with age. Computational modelling provides useful insights into the underlying mechanisms involved in age-related changes in musculoskeletal tissues. This model is hosted on BioModels Database and identified by: BIOMD0000000560. To cite BioModels Database, please use: BioModels Database: An enhanced, curated and annotated resource for published quantitative kinetic models. To the extent possible under law, all copyright and related or neighbouring rights to this encoded model have been dedicated to the public domain worldwide. Please refer to CC0 Public Domain Dedication for more information.

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Age-related changes in protein-related epitopes of human articular-cartilage proteoglycans.

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