CARTILAGE OLIGOMERIC MATRIX PROTEIN AND THROMBOSPONDIN-1 - PURIFICATION FROM ARTICULAR-CARTILAGE, ELECTRON-MICROSCOPIC STRUCTURE, AND CHONDROCYTE BINDING

Cartilage oligomeric matrix protein (COMP) and thrombospondin 1 (TSP1) were purified in a native form from normal bovine articular cartilage . The key step in the purification scheme was selective extraction wit h EDTA-containing buffer. Final separation of these two molecules was achieved by heparin affinity chromatography. Particles viewed by elect ron microscopy after rotary shadowing and negative staining revealed s tructures similar to their prototype molecules; from the Swarm rat cho ndrosarcoma for COMP, or from platelets for TSP1. Attachment of primar y bovine chondrocytes to purified matrix proteins was investigated. Ce lls attached to COMP but not to the structurally related TSP1 indicati ng separate functions for these proteins in cartilage.