Observations on the Effect of BMP-2 on Rat Bone Marrow Cells Cultured on Titanium Substrates of Different Roughnesses

Observations on the Effect of BMP-2 on Rat Bone Marrow Cells Cultured on Titanium Substrates of Different Roughnesses
J. VAN DEN DOLDER, J.E. DE RUIJTER, P.H.M. SPAUWEN, and J.A. JANSEN, University Medical Center Nijmegen, Netherlands
2003
IADR
Objective: The objective of this study was (1) to examine the osteoinductive capacity of different concentrations of BMP-2 on rat bone marrow (RBM) stromal cells in vitro on surface roughened and machined titanium substrates. Methods: 20.000 RBM cells/ml were seeded and cultured on machined and grit-blasted titanium discs for 4, 8 and 16 days. Different concentrations of rhBMP-2 (0, 10, 100, 1000 ng/ml) were supplemented to the medium. DNA, alkaline phosphatase activity, and calcium content were measured to evaluate cellular proliferation and differentiation. Morphological appearance of the specimens at 8 and 16 days of incubation was evaluated using scanning electron microscopy. Results: The alkaline phosphatase and calcium measurements revealed that BMP-2 stimulated the early differentiation of osteogenic cells in a dose-dependent manner. For example, the machined surfaces showed a significant increase (P<0.05) in calcium deposition when 100 and 1000 ng/ml BMP-2 were supplemented to the medium. Roughened surfaces showed this significant enhancement (P<0.05) in calcium content only with 1000 ng/ml BMP-2. After 16 days of culture, no significant differences in calcium content could be observed anymore between machined and roughened surfaces. Also, SEM evaluation learned that increasing BMP-2 concentrations resulted in more calcified globular accretions on both surfaces than when no BMP-2 was added. Conclusion: (1) the addition of rhBMP-2 in the medium stimulates the early differentiation and matrix mineralization of osteogenic cells in a dose-responsive manner, and (2) the used roughened titanium surfaces had no additional effect on proliferation and differentiation of primary derived rat bone marrow cells. Acknowledgement: The authors are grateful to Genetics Institute (Cambridge, Massachusetts, USA) for the generous gift of rhBMP-2.