[Immunohistochemical localization of bone Gla protein and osteonectin in normal human bone and cartilage tissues, and in osteosarcomas and chondrosarcomas].

The immunohistochemical localization of bone Gla protein (BGP) and osteonectin (ON) was investigated in normal human bone and cartilage tissues, and in osteosarcomas and chondrosarcomas with their respective antibodies. In normal bone and heterotopic ossification tissues, BGP and ON were detected in preosteoblasts, osteoblasts and young osteocytes, the reaction of which was strongest in osteoblasts. They were also demonstrated in most osteosarcomas, and their reaction was stronger in osteosarcomas with higher differentiation. These observations suggested that BGP and ON were related to the formation of normal and tumoral osteoid. In contrast, the localization of ON in normal cartilage and chondrosarcoma tissues was markedly different from that of BGP in these tissues. In normal growth cartilage, ON reacted with chondrocytes in hypertrophic and calcifying zone and matrix in calcifying zone, whereas BGP did not react. ON was also demonstrated in the cytoplasm and calcifying portion of most chondrosarcomas. These findings indicated that ON plays an important role in calcification of normal and tumoral cartilage tissues. BGP was detected in poorly differentiated and dedifferentiated chondrosarcomas. Thus, these antibodies are expected to be useful for studying calcification of human bone and cartilage and for the diagnosis of human osteosarcomas and chondrosarcomas.