The effects of high magnitude cyclic tensile load on cartilage matrix metabolism in cultured chondrocytes

Immunohistochemical study of matrilin-1 in arthritic articular cartilage of the mandibular condyle

BACKGROUND

The objective of this study was to investigate the expression of matrilin-1 in arthritic articular cartilage of the mandibular condyle by means of immunohistochemical methods.

METHODS

Condylar cartilage specimens were obtained from temporomandibular joints (TMJs) of 12 patients with arthritis (osteoarthritis and internal derangement) (mean age 51.8 years; age range 28-71 years) and four patients with TMJ ankylosis (mean age 44.0 years; age range 16-64 years), diagnosed clinically and with imaging examinations. Paraffin sections were immunostained with anti-matrilin-1 antibodies.

RESULTS

Matrilin-1 expression was detected in both patient groups with TMJ ankylosis and arthritis, and the level was remarkably higher in arthritic cartilage. The mean percentage of matrilin-1-producing cells to the total chondrocytes was significantly (P < 0.05) greater in the arthritic group (43.9 +/- 19.2%) than in subjects with TMJ ankylosis (28.0 +/- 8.7%).

CONCLUSIONS

Articular chondrocytes in the TMJ condyle can express matrilin-1 and the expression is enhanced in arthritic cartilage, suggesting a presence of functional or adaptive remodeling in the condyle in response to degenerative changes in the TMJ structures.

Mitochondrial stress-induced calcium signaling, phenotypic changes and invasive behavior in human lung carcinoma A549 cells

We have investigated mechanisms of mitochondrial stress-induced phenotypic changes and cell invasion in tumorigenic but poorly invasive human pulmonary carcinoma A549 cells that were partly depleted of mitochondrial DNA (mtDNA). Depletion of mtDNA (genetic stress) caused a markedly lower electron transport-coupled ATP synthesis, loss of mitochondrial membrane potential, elevation of steady state [Ca(2+)](c), and notably induction of both glycolysis and gluconeogenic pathway enzymes. Markers of tumor invasion, cathepsin L and TGFbeta1, were overexpressed; calcium-dependent MAP kinases (ERK1 and ERK2) and calcineurin were activated. The levels of anti-apoptotic proteins Bcl2 and Bcl-X(L) were increased, and the cellular levels of pro-apoptotic proteins Bid and Bax were reduced. Both mtDNA-depleted cells (genetic stress) and control cells treated with carbonyl cyanide m-chlorophenylhydrazone (metabolic stress) exhibited higher invasive behavior than control cells in a Matrigel basement membrane matrix assay system. MtDNA-depleted cells stably expressing anti-sense cathepsin L RNA, TGFbeta1 RNA, or treated with specific inhibitors showed reduced invasion. Reverted cells with 80% of control cell mtDNA exhibited marker protein levels, cell morphology and invasive property closer to control cells. Our results suggest that the mitochondria-to-nucleus signaling pathway operating through increased [Ca(2+)](c) plays an important role in cancer progression and metastasis.

Mechanical strain regulation of the chicken glypican-4 gene expression in the avian eggshell gland

Comparison of RNA fingerprinting of the avian eggshell gland (ESG) without and with an egg revealed upregulation of a 382-bp cDNA fragment that showed high homology to the mammalian glypican 4 (GPC-4). The gene sequence revealed a conserved glypican signature, a glycosyl phosphatidyl inositol-anchorage site, and cystein residues, most of which were conserved. GPC-4 was expressed in the ESG in a circadian fashion only during the period of eggshell calcification, when maximal mechanical strain was imposed. Removal of the egg just before to its entry into the ESG, with consequent elimination of the mechanical strain, caused reduction in the gene expression. Artificial application of the mechanical strain induced expression of the GPC-4 gene that was related to the level of the strain. GPC-4 expression was strain dependent in other parts of the oviduct. In the ESG, GPC-4 was expressed exclusively by the glandular epithelium and not by the pseudostratified epithelium facing the lumen. In summary, we cloned the avian homologue of GPC-4, established its pattern of expression in the avian ESG, and demonstrated for the first time that this gene is regulated by mechanical strain.

Reduction of cytokine-induced expression and activity of MMP-1 and MMP-13 by mechanical strain in MH7A rheumatoid synovial cells

Excessive mechanical load induces harmful outcomes for joint diseases, such as osteoarthritis and rheumatoid arthritis, but physical stimuli at appropriate intensity are essential for growth and maintenance of bone and articular cartilage. Using a fibroblast-like synoviocyte cell line derived from a patient with rheumatoid arthritis, we examined the effects of gentle cyclic strain, focusing on the expression and activity of matrix metalloproteinase-1 (MMP-1) and MMP-13. Synovial cells were cultured on a collagen-coated agar block and exposed to 2% cyclic strain at 6 rev./min for 1 h. Expression of MMP-1 and MMP-13 was assayed using semi-quantitative and real-time PCR, as well as immunoblotting. Their activity was measured using spectrofluorometry and zymography. The results showed that the cyclic strain reduced the mRNA and protein levels of MMP-1 and MMP-13, and that both collagenase and gelatinase activity was decreased under the strain. The reduction in MMP activity by the cyclic strain was not achieved by the transcriptional inhibitor, actinomycin D. In the presence of proinflammatory cytokines, such as IL-1 beta and TNF-alpha, the strain reduced the cytokine-induced expression and activities of MMPs. Interestingly, the strain elevated the mRNA level of tissue inhibitor of metalloproteinase-1 (TIMP-1) and TIMP-2. These results support a potential role of mechanical strain in down-regulating the cytokine-mediated proteolytic processes in synoviocytes.

Cell biology of osteoarthritis: the chondrocyte's response to injury

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.