Comparative immunohistochemical evaluation of the zonal distribution of extracellular matrix and inflammation markers in human meniscus in osteoarthritis and rheumatoid arthritis.

Unlabelled: The purpose of our study was to analyze the distribution of the major extracellular matrix glycosaminoglycan hyaluronan (HA), its receptor CD44 and cells which influence (re)modeling of the extracellular matrix (T- and B-cells, macrophages, endothelial cells) in menisci obtained from patients suffering from rheumatoid arthritis or osteoarthritis in order to analyze whether these markers could be useful to differentiate between both arthropathies. Human menisci were sampled from patients undergoing total knee arthroplasty. Histological staining (H&E, PAS/Alcian Blue for neutral and charged carbohydrate residues) and (immuno)histochemistry were performed for detection of HA, CD44, sphingosine-1-phosphate receptor 1 (EDG-1) as a marker for endothelial cells, CD3 as a marker for T-cells, CD20 as a marker for B-cells and CD68 as a marker for macrophages. The extracellular matrix in the vascularized zone showed higher amounts of HA as well as acid carbohydrate residues in comparison to the poorly vascularized zones of the meniscus in both disease entities. EDG-1 positive endothelial cells were present in all zones, with fewer cells being detected in the inner zones of the rheumatoid menisci than in the osteoarthritic ones. Macrophages, T- and B-cells as well as CD44-positive cells were more prominent in the vascularized zone of the meniscus than in the poorly vascularized central zone. The distribution patterns of the extracellular matrix components as well as the CD44-positive cells and the inflammation markers in the peripheral zone resembled the distribution in synovial tissue, indicating that both synovia and meniscus were involved in pathological changes in osteoarthritis and rheumatoid arthritis.

In Conclusion: the distribution of extracellular glycoconjugates and of cells modulating their synthesis showed similar results in both arthropathies, not enabling a differentiation between rheumatoid arthritis and osteoarthritis but underlining the role of these markers in inflammation and degradation in human meniscus.