Purification and characterization of two cartilage-inducing factors from bovine demineralized bone.

Abstract

Two naturally occurring peptides that induce chondrogenesis in culture were purified to apparent homogeneity. These cartilage-inducing factors (CIF-A and CIF-B) were isolated from bovine demineralized bone by dissociative extraction, gel filtration, cation-exchange chromatography and reversed-phase HPLC [high performance liquid chromatography]. CIF-A and CIF-B at concentrations of 1-10 ng/ml each induced embryonic rat mesenchymal cells in culture to assume a cartilage morphology and synthesize cartilage-specific proteoglycan and type II collagen. The amino acid compositions of CIF-A and CIF-B are similar but not identical. Both factors have an apparent MW of 26,000, as determined by NaDodSO4/PAGE [sodium dodecyl sulfate/polyacrylamide gel electrophoresis]. In the presence of 2-mercaptoethanol, both are converted to species of .apprx. 1/2 that MW, indicating that they are dimers of identical or very similar chains.