Fig. 6. Expression of CHL2 mRNA in diseased cartilage. (A) In situ hybridization for CHL2 in human adult knee joints, depicted in paired bright-field (left) and dark-field (middle) panels, and accompanied by a higher magnification view (bright field panel, right). Expression of CHL2 mRNA in normal knee cartilage (femur, 55-year old female). Note that CHL2 is localized on articular chondrocytes (right). However, CHL2⁺ chondrocytes are scattered throughout the cartilage. Weak signals are also visible in superficial zone chondrocytes. (B,C) Expression of CHL2 in osteoarthritic (OA) knee cartilage (B: 73-year-old male with OA, degenerative joint disease (DJD), and chronic proliferative synovitis; C: 48-year-old female with DJD). Signal is strongly induced in middle zone chondrocytes, but absent in superficial zone chondrocytes. (D) Expression of CHL2 in rheumatoid arthritic knee cartilage (80-year-old female with RA). Weakly positive chondrocytes are scattered throughout the cartilage. (E,F) Expression of CHL2 mRNA in hind paws of rats with collagen-induced arthritis, depicted in paired bright-field (left) and dark-field (middle) panels. CHL2 signal is weakly expressed in normal chondrocytes (E), and is not substantially elevated in animals with severe immune-mediated disease (F). Arrowheads indicate CHL2-positive chondrocytes. sz, superficial zone; mz, middle zone; dz, deep zone.