The small dermatan sulphate protein decorin interacts via its core protein with fibrillar collagens, and its glycosaminoglycan chains were proposed to be capable of self-association. It was therefore of interest to study the role of decorin in the contraction of cell-populated collagen lattices. Stable transfection of dihydrofolate reductase-deficient CHO cells with decorin cDNA resulted in impaired collagen lattice contraction. Using normal human skin fibroblasts in serum-free cultures, inclusion of 0.3 microM decorin in the culture medium also led to a delayed collagen gel contraction. Protein-free dermatan sulphate and the dermatan sulphate-degrading enzyme chondroitin ABC lyase were ineffective. Potential interactions between dermatan sulphate chains were studied by gel filtration. A shift in the elution position of [35S]sulphate-labelled decorin-derived glycosaminoglycans by unlabelled decorin could be observed only when the chains were prepared by trypsin. Chains liberated by beta-elimination or by cathepsin C were eluted at identical positions in the presence or absence of decorin. It is therefore unlikely, that the effect of decorin on collagen-gel retraction is brought about solely by glycosaminoglycan-glycosaminoglycan interactions.