Related Experiment Videos
Differential expression pattern of membrane-type matrix metalloproteinases in rheumatoid arthritis
1WHO Collaborating Center for Molecular Biology and Novel Therapeutic Strategies for Rheumatic Diseases, University Hospital, Zurich, Switzerland.
Objective:
To study the expression of messenger RNA (mRNA) for different membrane-type matrix metalloproteinases (MT-MMPs) and compare their expression pattern in rheumatoid arthritis (RA) and normal synovium.
Methods:
Polymerase chain reaction (PCR) with specific primers was performed to analyze the presence of MT1-, MT2-, MT3-, and MT4-MMP in synovial tissue and synovial fibroblasts from 10 patients with RA and 4 subjects without arthritis. In addition, in situ hybridization with digoxigenin-labeled RNA probes was used to investigate the expression pattern of MT-MMPs in the synovium of these subjects. MT-MMP-expressing cells were characterized by immunohistochemical double labeling with anti-CD68 monoclonal antibodies.
Results:
Reverse transcription-PCR revealed the expression of MT1-, MT2-, MT3-, and MT4-MMP mRNA in all tissues and cell cultures examined. However, in situ hybridization showed considerable differences in the expression pattern of the different MT-MMPs in RA synovium. MT1- and MT3-MMP mRNA were highly expressed in both the lining and the sublining layer, with more intense staining in the lining. Immunohistochemical double labeling demonstrated the presence of mRNA for MT1-MMP in fibroblasts and macrophages, as well as in osteoclast-like cells at sites of bone resorption. Expression of MT3-MMP mRNA was seen in fibroblasts and some macrophages. Expression of MT2- and MT4-MMP was characterized by staining of only a few CD68-negative fibroblasts, and no differences could be found between the lining and sublining. Normal synovial samples showed only limited staining for all MT-MMPs.
Conclusion:
Our results indicate a role for MT1-MMP not only in the matrix degradation by fibroblasts, but also in osteoclast-mediated bone resorption in RA. Given the ability of MT1-MMP to activate MMP-2 and MMP-13, the findings also point to a cooperation between fibroblasts and macrophages in degrading cartilage and bone. While MT3-MMP is also intensely expressed in RA synovium, MT2- and MT4-MMP appear not to be involved in rheumatoid joint destruction.
Insights
Matrix metalloproteinases (MMPs) play a role in rheumatoid arthritis (RA) joint destruction. MT1-MMP and MT3-MMP are highly expressed in RA synovium, suggesting their involvement in disease progression and bone resorption.
Area of Science:
- Rheumatology
- Molecular Biology
- Biochemistry
Background:
- Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by joint destruction.
- Matrix metalloproteinases (MMPs), particularly membrane-type MMPs (MT-MMPs), are implicated in extracellular matrix degradation and tissue remodeling.
- Understanding the specific roles of different MT-MMP subtypes in RA pathogenesis is crucial for developing targeted therapies.
Purpose of the Study:
- To investigate the expression patterns of messenger RNA (mRNA) for MT1-, MT2-, MT3-, and MT4-MMP in rheumatoid arthritis (RA) synovium.
- To compare the expression of these MT-MMPs in RA synovium versus normal synovium.
- To identify the cell types expressing MT-MMPs in RA synovial tissue.
Main Methods:
- Polymerase chain reaction (PCR) was used to detect MT-MMP mRNA in synovial tissue and fibroblasts from RA patients and controls.
- In situ hybridization was employed to visualize the spatial expression patterns of MT-MMPs within the synovium.
- Immunohistochemical double labeling with anti-CD68 antibodies identified MT-MMP-expressing cells, including fibroblasts and macrophages.
Main Results:
- All four MT-MMP subtypes (MT1-, MT2-, MT3-, and MT4-MMP) mRNA were detected in both RA and normal synovium.
- MT1- and MT3-MMP mRNA showed significantly higher expression in RA synovium, particularly in the lining layer.
- MT1-MMP mRNA was found in fibroblasts, macrophages, and osteoclast-like cells, while MT3-MMP mRNA was present in fibroblasts and macrophages. MT2- and MT4-MMP expression was limited.
Conclusions:
- MT1-MMP plays a significant role in RA, contributing to both fibroblast-mediated matrix degradation and osteoclast-driven bone resorption.
- The findings suggest a collaborative role between fibroblasts and macrophages in cartilage and bone destruction in RA, potentially mediated by MT1-MMP's ability to activate other MMPs.
- While MT3-MMP is also upregulated in RA, MT2- and MT4-MMP do not appear to be major contributors to rheumatoid joint destruction.