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- Lark, Michael W., et al.
(författare)
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Aggrecan degradation in human cartilage : Evidence for both matrix metalloproteinase and aggrecanase activity in normal, osteoarthritic, and rheumatoid joints
- 1997
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Ingår i: Journal of Clinical Investigation. - 0021-9738. ; 100:1, s. 93-106
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Tidskriftsartikel (refereegranskat)abstract
- To examine the activity of matrix metalloproteinases (MMPs) and aggrecanase in control and diseased human articular cartilage, metabolic fragments of aggrecan were detected with monospecific antipeptide antibodies. The distribution and quantity of MMP-generated aggrecan G1 fragments terminating in VDIPEN341 were compared with the distribution of aggrecanase-generated G1 fragments terminating in NITEGE373. Both types of G1 fragments were isolated from osteoarthritic cartilage. The sizes were consistent with a single enzymatic cleavage in the interglobular domain region, with no further proteolytic processing of these fragments. Both neoepitopes were also detected by immunohistochemistry in articular cartilage from patients undergoing joint replacement for osteoarthritis (OA), rheumatoid arthritis (RA), and in cartilage from adults with no known joint disease. In control specimens, the staining intensity for both G1 fragments increased with age, with little staining in cartilage from 22-wk-old fetal samples. There was also an increase with age in the extracted amount of MMP- generated neoepitope in relation to both aggrecan and collagen content, confirming the immunohistochemical results. After the age of 20-30 yr this relationship remained at a steady state. The staining for the MMP-generated epitope was most marked in control cartilage exhibiting histological signs of damage, whereas intense staining for the aggrecanase-generated fragment was often noted in adult cartilage lacking overt histological damage. Intense staining for both neoepitopes appeared in the more severely fibrillated, superficial region of the tissue. Intense immunostaining for both VDIPEN- and NITEGE-neoepitopes was also detected in joint cartilage from patients with OA or RA. Cartilage in these specimens was significantly more degraded and high levels of staining for both epitopes was always seen in areas with extensive cartilage damage. The levels of extracted VDIPEN neoepitope relative to collagen or aggrecan in both OA and RA samples were similar to those seen in age-matched control specimens. Immunostaining for both types of aggrecan fragments was seen surrounding the cells but also further removed in the interterritorial matrix. In some regions of the tissue, both neoepitopes were found while in others only one was detected. Thus, generation and/or turnover of these specific catabolic aggrecan fragments is not necessarily coordinated. Our results are consistent with the presence in both normal and arthritic joint cartilage of proteolytic activity against aggrecan based on both classical MMPs and 'aggrecanase'.
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| 2. |
- Lark, Michael W., et al.
(författare)
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Aggrecan degradation in osteoarthritis and rheumatoid arthritis
- 1995
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Ingår i: Acta Orthopaedica. - : Informa UK Limited. - 1745-3674 .- 0001-6470. ; 66:S266, s. 92-97
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Tidskriftsartikel (refereegranskat)abstract
- Aggrecan turnover is critically important to maintain extracellular matrix homeostasis in articular cartilage. Cartilage aggrecan metabolism has been studied in chondrocyte cell cultures, cartilage explant cultures, and in whole animal models. In many of these studies, matrix metalloproteinases (MMPs) are proposed to degrade cartilage aggrecan. MMP expression appears elevated in joint tissues from patients with osteoarthritis (OA) and rheumatoid arthritis (RA) (Dean et al. 1989, Wolfe et al. 1993) and inhibitors of both MMPs and thiol proteinases have been shown to block aggrecan (Buttle et al. 1992) and type II collagen (Mort et al. 1993) degradation in cartilage explant cultures. Using antibodies and cDNA probes, elevations in expression and concentration of many of these enzymes in animal models and in OA and RA have been described. Human cartilage aggrecan has now been cloned and sequenced (Doege et al. 1991). This information, in combination with the ability to sequence aggrecan and aggrecan fragments at the protein level, has resulted in the identification of several aggrecan fragments which appear to result from proteinase degradation. In this report, we describe data which suggest that MMPs may in part be responsible for aggrecan catabolism in normal articular cartilage, as well as in the elevated catabolism seen in OA and RA.
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