Immunohistochemical detection of cathepsin D, K, and L in the process of endochondral ossification in the human

Cathepsins D, K, and L were immunolocalized in tissue undergoing endochondr al ossification in the human. Cathepsins D, K, and L were localized in oste oclasts and chondroclasts attached to bone matrix and cartilage matrix, res pectively. Cathepsins D and L were immunostained in chondrocytes. Immunoloc alization of cathepsin D was limited to hypertrophic chondrocytes adjacent to the osteochondral junction. In contrast, cathepsin L was immunolocalized in both proliferating and hypertrophic chondrocytes. In the bone marrow sp ace, cathepsins D, K, and L were localized in multinucleated cells. Catheps in D was diffusely detected in mononuclear bone marrow cells which were neg ative fur cathepsins K and L. The present findings indicated that cathepsin s K, D, and L were associated with the process of endochondral ossification in the human, and suggested that these cathepsins share roles in bone and cartilage turnover in the human.