Figure 3.

Light microscopic detection of cartilage oligomeric protein (COMP) and its mRNA. (a) Staining for COMP is seen in the interterritorial matrix of the superficial and middle zones of healthy cartilage, whereas in the deeper zones a more pericellular pattern is found (arrow and inset). (b) In osteoarthritic (OA) cartilage of late disease stages, staining is seen mainly in clusters (arrow and inset). (c) In situ hybridization of COMP mRNA localizes it mainly in the cytoplasm of chondrocytes found in clusters of OA tissue (arrows); inset depicts a negative control of healthy cartilage. Bars, 70 μm in (a), (b), and inset (c) and 40 μm in (c) and insets (a) and (b).