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localization of type VI collagen in the lining cell layer of normal and rheumatoid synovium
1Department of Pathology, School of Medicine, Kanazawa University, Japan.
Insights
Type VI collagen supports synovial lining cells in normal and rheumatoid joints. It forms structures in the extracellular matrix and resists degradation by matrix metalloproteinases, unlike other collagens.
Area of Science:
- Biochemistry
- Immunology
- Rheumatology
Background:
- Collagen is crucial for connective tissue structure and function.
- The specific roles of different collagen types in synovial tissue, particularly the lining layer, are not fully understood.
- Synovial lining cells secrete matrix metalloproteinases that degrade collagen.
Purpose of the Study:
- To immunolocalize collagens types I-VI in normal and rheumatoid synovium.
- To investigate the structural organization and resistance of collagens to matrix metalloproteinases in synovial lining cells.
Main Methods:
- Immunofluorescence and immunogold staining using monospecific antibodies against collagen types I-VI.
- Treatment of rheumatoid synovial tissue with bacterial collagenase.
- Assessing the susceptibility of collagen types I-VI to matrix metalloproteinases 1, 2, and 3.
Main Results:
- Type VI collagen was localized to the extracellular matrix of the lining cell layer, forming filamentous material.
- Type III collagen was found in both lining and sublining cell layers.
- Type VI collagen filaments showed potential for periodic structure formation after collagenase treatment.
- Type VI collagen was completely resistant to degradation by matrix metalloproteinases 1, 2, and 3.
Conclusions:
- Type VI collagen plays a significant role in supporting synovial lining cells in both normal and rheumatoid synovium.
- Its unique resistance to matrix metalloproteinases suggests a specialized function in maintaining synovial integrity.
Abstract:
Types I to VI collagens were immunolocalized in normal and rheumatoid synovium using monospecific antibodies. Immunofluorescence studies showed type VI in the extracellular matrix of the lining cell layer, whereas positive staining for type III collagen was observed in both the lining and sublining cell layers. All other collagens could not be detected in the lining cell layer. Immunogold staining of the rheumatoid synovium localized type VI collagen to filamentous material, which was the major extracellular structure of the lining cell layer. Type III collagen was associated with thin cross-striated collagen fibrils. A brief treatment of rheumatoid synovial tissue with bacterial collagenase produced in the lining cell layer numerous broad-banded fibrils with 100-nm periodicity; these fibrils could be labeled with the antibody against type VI collagen. This suggests that type VI collagen filaments have the potential to form periodic structures under certain conditions. We further studied the susceptibility of type I to VI collagens to matrix metalloproteinase 1, 2 and 3 (collagenase, gelatinase of molecular weight 72,000, stromelysin), which are secreted by synovial lining cells in rheumatoid synovium, and found only type VI collagen to be completely resistant to all these metalloproteinases. These data indicate that type VI collagen, which has the ability to bind to cells and to interstitial collagens, plays an important role in supporting the synovial lining cells in the normal and rheumatoid synovium.