Adam-10 protein is present in human articular cartilage primarily in the membrane-bound form and is upregulated in osteoarthritis and in response to IL-1α in bovine nasal cartilage

The objective of our study was to determine the tissue distribution and localization of ADAM-10 protein in human and bovine cartilage and the changes it undergoes with cartilage degeneration seen in osteoarthritis (OA) and under the influence of interleukin-1 (IL-1). Human normal and OA articular cartilage and bovine nasal cartilage cultured in the presence of IL-1 were processed for histology and immunohistochemistry. ADAM-10 protein was extracted from human cartilage and analyzed by Western blotting using anti-ADAM-10 antibodies. Fluor S Image analyzer and Quantity One software program were applied to quantify the total amount of ADAM-10. ADAM-10 protein was detected in both human and bovine cartilage. The strongest immunostaining was found in the cytoplasm and/or cell membranes of the superficial and upper middle layer of normal adult human cartilage, in the clusters and fibrillated areas of OA cartilage, and in IL-1α-stimulated bovine nasal cartilage. The distribution of ADAM-10 protein in bovine nasal cartilage was dependent on the length of exposure to IL-1α and corresponded to the areas of proteoglycan depletion. By Western blotting analysis of human cartilage, ADAM-10 was primarily detected in the membrane-enriched fraction and its levels were increased in degenerated and OA cartilage compared to normal cartilage. The results of this study suggest that ADAM-10 might be an important factor associated with cartilage degenerative processes.