Prostromelysin and procollagenase genes are differentially UP-regulated in chondrocytes from the knees of rabbits with experimental osteoarthritis (original) (raw)
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Arthritis & Rheumatism, 2002
Objective. Osteoarthritic (OA) cartilage destruction depends on collagen-and aggrecan-degrading proteases such as collagenases (MMP-1 and MMP-13), stromelysin (MMP-3), MMP-14, as well as the so-called aggrecanases (ADAM-TS4 and ADAM-TS5). In this study, we tried to clarify whether these proteases are expressed in vivo in human normal and OA cartilage (and whether they are up-regulated or down-regulated during the disease process) and in interleukin-1 (IL-1)-stimulated chondrocytes in vitro. Methods. Quantitative polymerase chain reaction assays were developed and performed on RNA isolated directly from normal and degenerative cartilage tissue as well as from primary human articular chondrocytes cultured with and without IL-1. Results. In vivo, MMP-1 was detectable only at very low levels in any condition. MMP-13 expression was low in normal and early degenerative cartilage but was strongly up-regulated in late-stage OA specimens. MMP-1 and MMP-13 were expressed much higher in vitro than in vivo and were up-regulated by IL-1. Among all proteases, MMP-3 was by far the most strongly expressed, although it was strongly downregulated in late-stage OA specimens. Expression of MMP-3 was higher in vitro than in vivo and was up-regulated by IL-1. ADAM-TS5 and MMP-14 were expressed in all sample groups. Expression of ADAM-TS4 was very low in vivo and was induced in vitro after stimulation by IL-1. Conclusion. Our expression data clearly support MMP-13 as the major collagenase in OA cartilage. The most strongly expressed aggrecanase was ADAM-TS5. ADAM-TS4 was expressed only at a very low level in normal cartilage and was only slightly up-regulated in OA cartilage, casting doubt on this enzyme being the relevant aggrecanase of articular cartilage. Results of our study show that expression of many enzymes is significantly different in vitro and in vivo and suggest that IL-1 stimulation of articular chondrocytes might not be a good model for the matrix catabolism in OA cartilage.
Journal of Clinical Investigation, 1996
Proteolysis of triple-helical collagen is an important step in the progression toward irreversible tissue damage in osteoarthritis. Earlier work on the expression of enzymes in cartilage suggested that collagenase-1 (MMP-1) contributes to the process. Degenerate reverse transcription polymerase chain reaction experiments, Northern blot analysis, and direct immunodetection have now provided evidence that collagenase-3 (MMP-13), an enzyme recently cloned from human breast carcinoma, is expressed by chondrocytes in human osteoarthritic cartilage. Variable levels of MMP-13 mRNA were present in total RNA prepared from six osteoarthritic cartilage samples. Expression of both MMP-13 and MMP-1 in cartilage was significantly induced at both the message and protein levels by interleukin-1 ␣. Recombinant MMP-13 cleaved type II collagen to give characteristic 3/4 and 1/4 fragments; however, MMP-13 turned over type II collagen at least 10 times faster than MMP-1. Experiments with intact type II collagen as well as a synthetic peptide suggested that MMP-13 cleaved type II collagen at the same bond as MMP-1, but this was then followed by a secondary cleavage that removed three amino acids from the 1/4 fragment amino terminus. The expression of MMP-13 in osteoarthritic cartilage and its activity against type II collagen suggest that the enzyme plays a significant role in cartilage collagen degradation, and must consequently form part of a complex target for proposed therapeutic interventions based on collagenase inhibition.
Cell biology of osteoarthritis: the chondrocyte's response to injury
Current rheumatology reports, 2001
Cartilage is comprised of a large amount of functional extracellular matrix that is made and maintained by a small number of chondrocytes, the sole resident cell type. Normal cartilage exists in a relatively steady state: that is, the anabolic processes (those that result in the synthesis of cartilage matrix components) are in equilibrium with the catabolic processes (those that result in the normal turnover of matrix molecules). If the functional extracellular matrix is disturbed by physical or molecular means, the cells respond in an attempt to repair the matrix. This stimulated activity does not result in repair due to the extent and complexity of the extracellular matrix. Eventually, the newly synthesized and activated catabolic enzymes degrade the matrix components. This review presents the cellular and molecular mechanisms that account for this activity and provides some possible solutions.
Arthritis Research & Therapy, 2003
Japan Arthritis Res Ther 2003, 5(Suppl 3):1 (DOI 10.1186/ar800) Apoptosis is a principal mechanism in metazoans by which superfluous or potentially harmful cells are eliminated. Deregulation of this process leads to a variety of diseases such as cancer and autoimmune diseases. Stimuli that can induce apoptosis are relatively diverse, and include the death factors (Fas ligand, tumor necrosis factor and TRAIL), DNA damage, and oxidative stress. Regardless of the origin of the apoptotic stimulus, commitment to apoptosis leads to activation of caspases, a family of cysteine proteases. Cleavage of a select group of cellular substrates by caspases is responsible for the morphological and biochemical changes that characterize apoptotic cell death. The degradation of nuclear DNA into nucleosomal units is one of the features of apoptotic cell death, and is mediated by a caspase-activated DNase (CAD). Cells deficient in CAD undergo cell death without the DNA fragmentation, but CAD-null mice did not show any adverse phenotypes. A close examination of the apoptotic cells in these mice indicated that apoptotic cells are always in macrophages. It seems that at an early stage of apoptosis, the dying cells present an 'eat me signal' on their surface. This signal is recognized by macrophages for engulfment, and DNase II in the lysosomes of macrophages degrades DNA of apoptotic cells. Mice deficient in both CAD and DNase II genes were established, and the development of various organs was found to be severely impaired in these mutant mice. The mice accumulated a large amount of undigested DNA in macrophages in various tissues during development. This accumulation of DNA in macrophages activated the innate immunity to induce the expression of the interferon β gene. The interferon thus produced seems to be responsible for the impaired tissue development. These results indicate that the degradation of DNA during apoptotic cell death is an essential step of apoptosis to maintain mammalian homeostasis.
Modulating chondrocyte hypertrophy in growth plate and osteoarthritic cartilage
J Musculoskelet …, 2008
induce expression of active proteinases leading to increased matrix degradation . Other fragments increase matrix synthesis 14,15 and cellular proliferation . Several studies have suggested that type II collagen fragments might influence chondrocyte differentiation in endochondral ossification , and we hypothesise that collagen II fragments might also promote cellular hypertrophy when they are over-produced in OA.