Collagen Type X: A Component of the Surface of Normal Human, Pig, and Rat Articular Cartilage

Collagen type X, a protein generally associated with hypertrophic chondrocytes of avian and mammalian growth plate during endochondral growth of long bones, has been previously shown to be present during disruption of normal metabolic status of articular cartilage during osteoarthritis. We have demonstrated that collagen type X is present as a component of normal articular cartilage in adult human, growing pig and new-born rat. The protein was immunolocalized in these tissues at the surface of the articular cartilage and for human tissue there was some staining of chondrocytes adjacent to the ‘tidemark’ zone. The presence of collagen type X was confirmed by isolating the protein from these tissues and its identification by SDS–PAGE and immunodetection with antibodies specific for collagen type X.