Recombinant human osteogenic protein 1 is a potent stimulator of the synthesis of cartilage proteoglycans and collagens by human articular chondrocytes

Objective. To study the effects of recombinant human osteogenic protein-1 (rHuOP-1; bone morphogenetic protein-7) on proteoglycan and collagen synthesis by human articular chondrocytes. Methods. Articular chondrocytes from fetal, adolescent, and adult human donors were cultured in alginate beads for 4 days in a mixture of Ham's F-12, Dulbecco's modified Eagle's medium, 10% fetal bovine serum (FBS), then for an additional 3-10 days in the presence and absence of rHuOP-1, with and without FBS, Chondrocyte synthetic activity was measured as the amount of incorporation of S-35-sulfate into proteoglycans and H-3-proline into hydroxyproline. Sieve chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis were performed to identify specific proteoglycans and collagens. Results. Recombinant human OP-1 markedly stimulated the synthesis of proteoglycans (mostly aggrecan) and collagens (predominantly type II) by all chondrocyte preparations, This did not require the presence of FBS and was associated with continued expression of the chondrocyte phenotype. Conclusion. Recombinant human OP-1 is a more potent stimulator of the synthesis of cartilage-specific molecules by human articular chondrocytes than are other factors tested far comparison, including TGF beta 1 and activin A.