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Expression of BMP-3, -7 and CDMP-1, -2 in normal and osteoarthritic human articular cartilage

With aging the responsiveness of articular cartilage to different growth factors is changed. Further, osteoarthritis is a joint disease affecting primarily the elderly. In this study we were interested in the expression of BMP-3, -7 and CDMP-1, -2 in normal articular cartilage (young people), in macroscopically normal articular cartilage of elderly people and in osteoarthritic cartilage. All these morphogenetic proteins are members of TGF-beta superfamily and are involved in bone and cartilage homeostasis. The cylindrical cartilage-bone samples were dissected from tibial condyles of donors with no history of joint disease during authopsy and from patients with knee joint osteoarthritis. The samples were decalcified and embedded in paraffin wax. Sections were processed for histology and immunohistochemistry. In normal articular cartilage we found the expression of CDMP-1, -2 only in the chondrocytes of all three uncalcified layers. The expression of BMP-3, -7 was negative. With aging the expression pattern of these morphogenic proteins was changed. In the tangential layer we found very strong pericellular reaction for BMP-7 and CDMP-1, -2. Deeper, in transitional layer we found strong expression intracellularly and pericellularly for the same proteins. Finally, in the radial layer positive expression was found in the chondrocytes with very pale reaction pericellularly. The expression pattern for BMP-3 was the same but the reaction was less effective. In osteoarthritis, articular cartilage lost its morphological structure and the chondrocytes were in the form of clusters. We still found the expression of BMP-3, -7 and CDMP-1, -2 but weaker and only intracellularly in the cells of clusters. Only for BMP-7 was found weak positive pericellular reaction. Our results show that with aging the expression pattern of these morphogenetic proteins is changed and the activity of these proteins increases. In osteoarthritis the expression still exists but was weaker and reminds as residual activity.

articular cartilage; osteoarthritis; BMPs; CDMPs

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