Immunofluorescence localization of fibronectin in chondrosarcoma cartilage matrix

In this study, we have compared the extracellular matrix components and the in vitro adhesion characteristics of normal rat epiphysial chondrocytes with those from the Swarm rat chondrosarcoma, which has many of the biochemical characteristics of normal cartilage. With the use of immunofluorescence techniques, tissue slices and chondrocytes in culture were tested for the presence of collagen types I and II, cartilage-characteristic proteoglycan, and fibronectin. Both normal and tumor matrix contained type II collagen and cartilage proteoglycan, but only the tumor matrix contained fibronectin. In culture, tumor-derived chondrocytes continued to accumulate fibronectin in their matrix, even after deposition of type II collagen and proteoglycans, while normal chondrocytes did not. When the attachment characteristics of both types of chondrocytes were compared, tumor chondrocytes required fibronectin for attachment, while normal chondrocytes used another attachment factor that had been identified previously as chondronectin. These studies suggest that, although biochemically similar to normal chondrocytes, tumor chondrocytes are no longer able to express the regulatory mechanisms for fibronectin accumulation.