The expression of cyclooxygenase-1, cyclooxygenase-2 and 5-lipoxygenase in inflammatory muscle tissue of patients with polymyositis and dermatomyositis

OBJECTIVE

To describe cyclooxygenase-1 (COX-1), cyclooxygenase-2 (COX-2) and 5-lipoxygenase (5-LOX) expression in muscle tissue in patients with idiopathic inflammatory myopathies (IIM) - dermatomyositis (DM) and polymyositis (PM) and to find out if any differences between affected and non-affected muscles detected by MRI exist.

METHODS

Samples of muscle tissue from 7 patients with dermatomyositis (DM) and from 4 with polymyositis (PM) were obtained by needle biopsy from affected and non-affected sites distinguished by magnetic resonance imaging. In situ hybridization with antisense mRNA probes was employed to detect COX-1, COX-2 and 5-LOX mRNA.

RESULTS

Expression of COX-1, COX-2, and 5-LOX mRNA was found in all samples - in the muscle cells, inflammatory cells and in vessels. COX-1 mRNA expression predominated in the inflammatory cells and vessels and was higher in affected than in non-affected sites detected by MRI (mean intensity 3.22+/-0.67 vs. 2.0+/-0.87; p = 0.0006). The expression of COX-2 mRNA was high mainly in inflammatory cells and/or vessels and was increased in MRI-detected affected tissues (3.5+/-0.88; 1.9+/-1.1; p = 0.003), as was the expression of COX-2 mRNA in muscle cells (2.1+/-1.0 vs. 1.3+/-1.0; p = 0.021). 5-LOX mRNA was largely expressed in muscle cells from MRI-detected affected sites and the signal intensity was higher in comparison with samples taken from non-affected tissues detected by MRI (3.22+/-0.7 vs. 1.67+/-0.7; p = 0.0007).

CONCLUSION

Expression of COX-1, COX-2 and 5-LOX mRNA was observed for the first time in muscle tissues from IIM patients. This expression was increased in affected tissues detected by MRI, which may suggest a role of COX-1, COX-2, and 5-LOX in the pathogenesis of IIM.

Membrane-type-1 matrix metalloproteinase is abundantly expressed in fibroblasts and osteoclasts at the bone-implant interface of aseptically loosened joint arthroplasties in situ

OBJECTIVE

To investigate the distribution pattern of membrane-type-1 matrix metalloproteinase (MT1-MMP) within the synovial-like interface membranes of failed prosthetic joints.

METHODS

Interface tissue around loose arthroplasties containing both fibrous membrane and attached bone was obtained from 6 patients at revision surgery. In situ hybridization with digoxigenin labeled RNA probes was applied to investigate MT1-MMP expression in paraffin sections of the samples. In addition, double labeling using immunohistochemistry was performed to characterize MT1-MMP producing cells.

RESULTS

Apart from being present in fibroblasts, MT1-MMP was also found expressed in osteoclasts at sites of bone resorption. Our results revealed no expression of MT1-MMP at parts of the membrane that originally had been located next to the prosthesis. In contrast, abundant staining for MT1-MMP was observed at sites attached to bone. MT1-MMP mRNA expression was more intense at those sites of bone resorption covered by a thicker interface membrane.

CONCLUSION

These results indicate a role for MT1-MMP not only in matrix degradation by fibroblasts but also in osteoclast mediated bone resorption. Given the ability of MT1-MMP to activate MMP2 and MMP13, they suggest also that osteoclasts might contribute to matrix degradation by activating these MMP. This could be of potential interest not only for other conditions in which bone resorption by fibroproliferative tissue plays a role, but also to design novel strategies to prevent loosening of prosthetic joints.