IMMUNOLOCALIZATION OF TYPE-X COLLAGEN IN NORMAL FETAL AND ADULT OSTEOARTHRITIC CARTILAGE WITH MONOCLONAL-ANTIBODIES

For studies on processing and tissue distribution of type X collagen, monoclonal antibodies were prepared against human recombinant collagen type X (hrCol X) and tested by ELISA, immunoblotting and immunohistol ogy. Forty-two clones were obtained which were grouped into four diffe rent subsets based on their reactivity against native and denatured hr Col X, pepsin-treated hrCol X, and the C-terminal NC-1 domain. Here we present results obtained with four monoclonal antibodies: Clone X 53, a representative of group I, binds with high affinity to both native and pepsin-digested hrColX but with low affinity to the NC-1 dimer; mo noclonal antibodies of group II and III recognized native and denature d hrColX but not NC-1; antibodies of group II, but not III, reacted to some extent with pepsin treated hrCol X; one antibody (X 34) was obta ined that reacted strongly with the isolated NC-1 dimer and native hrC ol X but not with the NC-1 monomer or pepsin-digested hrCol X (group I V). Antibodies of all groups stained specifically the hypertrophic zon e of fetal human epiphyseal cartilage. Mab X 53 stained the peri- and extracellular matrix of hypertrophic chondrocytes in the lower hypertr ophic zone and in the calcified cartilage core in endochondral bone tr abecules, while clone X 34 stained intracellularly and the pericellula r matrix. All other tissues or cells of the epiphysis were negative. A ntibody X 53 reacted also with canine, murine and guinea pig hypertrop hic cartilage in tissue sections, but not with bovine or porcine type X collagen. In sections of osteoarthritic cartilage, clusters of hyper trophic chondrocytes in the deep zone were stained, confirming previou s observations on enhanced chondrocyte hypertrophy and type X collagen expression in osteoarthritic articular cartilage.