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Localisation of lysozyme mRNA in rheumatoid synovial membrane by in situ hybridisation
Y T Konttinen1, V Bergroth, M Kulomaa
1Fourth Department of Medicine, Helsinki University Central Hospital, Finland.
Abstract:
Type A synovial lining cells have been shown to contain lysozyme in their lysosomes. This might be phagocytosed because synovial fluid contains lysozyme originating from tissue macrophages and articular cartilage but in arthritides, in particular, from neutrophils. In situ hybridisation with 35S labelled cDNA was used to detect mRNA for lysozyme over synovial lining in patients with rheumatoid arthritis. No hybridisation was found with lactoferrin cDNA, which was used as a negative control. Computer search against the EMBL gene bank (release 14) did not show any significant cross hybridisation to a known sequence. In cytological specimens 35S-cDNA:mRNA hybrids were observed in positive but not in negative control cells. The presence of lysozyme and its mRNA suggests that type A synovial lining cells are of mononuclear phagocyte lineage.
Insights
Type A synovial lining cells contain lysozyme and its messenger RNA (mRNA), suggesting they originate from mononuclear phagocytes. This finding is particularly relevant in rheumatoid arthritis research.
Area of Science:
- Immunology
- Cell Biology
- Rheumatology
Background:
- Type A synovial lining cells are known to contain lysozyme within their lysosomes.
- Synovial fluid lysozyme can originate from macrophages, cartilage, and notably, neutrophils in arthritic conditions.
Purpose of the Study:
- To investigate the presence of lysozyme mRNA in Type A synovial lining cells.
- To determine if Type A synovial lining cells are of mononuclear phagocyte lineage.
Main Methods:
- In situ hybridization using 35S-labeled cDNA to detect lysozyme mRNA in synovial lining from rheumatoid arthritis patients.
- Lactoferrin cDNA was used as a negative control.
- Computer search against the EMBL gene bank for sequence homology.
Main Results:
- Lysozyme mRNA was detected in Type A synovial lining cells of rheumatoid arthritis patients.
- No hybridization was observed with lactoferrin cDNA.
- No significant cross-hybridization to known sequences was found in the gene bank search.
Conclusions:
- The presence of both lysozyme and its mRNA in Type A synovial lining cells supports their origin from the mononuclear phagocyte lineage.
- This cellular origin has implications for understanding the pathogenesis of arthritic conditions.