Effects of low concentration BMP-7 on human osteoarthritic chondrocytes: comparison of different applications.

While BMP-7 (OP-1) is one of the most potent growth factors in cartilage tissue engineering, the effects of exogenous low concentration BMP-7 on osteoarthritic chondrocytes are still unknown. Human osteoarthritic chondrocytes obtained from the femoral condyles of 10 patients were grown either in monolayer or in 3D collagen type-I gel culture in vitro. The growth factor was either given as a single dose of 50 ng/mL, a repeated dose, or continuously released from PGLA microspheres. Matrix formation was monitored by immunohistochemical staining and real-time PCR. In contrast to monolayer culture, the differentiated phenotype was prevailed in 3D culture. Collagen type-II protein production in the 3D group with a continuous BMP-7 release was enhanced in comparison to all other groups. Gene expression of collagen type-II and aggrecan was elevated in all treatment groups, with the highest extent in the BMP-7 microsphere group. In summary, treatment of articular chondrocytes with a low dose of BMP-7 leads to an elevated production of extracellular matrix components. This effect is further increased when BMP-7 is given repeatedly or continuously, which proved to be the most effective form of application.