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.