Thrombospondin 1 is present in articular cartilage and is synthesized by chondrocytes. Adult bovine articular chondrocytes in serum-free medium were evaluated in a solid-phase assay for their ability to attach to thrombospondin 1 isolated from human platelets. The chondrocytes attached to the thrombospondin 1 by a mechanism that was inhibited by a synthetic linear GRGDSP but not a GRGESP peptide. The cells, however, did not spread on thrombospondin 1, but did spread on fibronectin and Pep-Tite 2000, a synthetic RGD-containing peptide. Preincubation of thrombospondin 1 with EDTA irreversibly inhibited its capacity to attach to chondrocytes. We conclude that thrombospondin 1 binds to chondrocytes by its RGD sequence.
