Proteins in the tensile region of adult bovine deep flexor tendon

Tendon proteoglycans and proteins (other than Type I collagen) were solubil ized by sequential extraction of powdered adult bovine deep flexor tendon, Only the proximal (tensile) region of this tendon was used. The experiments involved 24-hour extraction with phosphate buffered saline (to remove comp onents that are readily soluble), followed by repeated extraction with 4 mo l/L guanidine (to break noncovalent bonds holding components into the tissu e), and then extraction with 4 mol/L guanidine containing dithiothreitol (t o dissociate components held by disulfide bonds). Proteins accounting for a pproximately 5% of the tissue dry weight could be removed by the extraction protocol. Proteins were identified by Western blotting and correlation wit h stained gels, The major extracted components were identified as decorin, Type VI collagen, fibromodulin and a member of the leucine rich repeat prot ein family (PRELP), In addition an oligomeric matrix protein initially iden tified in cartilage (COMP), aggrecan, and biglycan mere present. Most of th ese proteins were entirely extracted in cold 4 mol/L guanidine. How ever, s ome Type VI collagen and cartilage oligomeric matrix protein could not be r emoved unless the tissue was reduced with dithiothreitol, Many of these pro teins have been considered as molecules that are primarily or exclusively c omponents of cartilage, Cartilage and tendon are tissues with different his tologic appearance and different function. However, the fact that the same biochemical components are found in cartilage and tendon show's the related ness of these connective tissues and the cells that produce them, Tissue en gineering attempts to reconstruct tendon using only its major or unique com ponents may omit significant aspects of the tissue's structure.