In this study, the growth factors in COLLOSSE were analyzed, using ELISA tests, mass spectrometry, western blotting, and a 24-day cell culture experiment using osteoblast-like cells. The results of the ELISA testing, mass spectrometry, and western blotting all confirmed that TGF-beta1 was the main growth factor in COLLOSSE at 55 ng/mg. The results from the culture test showed that the cell proliferation, alkaline phosphatase activity, and matrix calcification were all drastically changed by the addition of COLLOSSE, mirroring the effects of addition of TGF-beta1. We conclude that COLLOSSE is not only a rich source of TGFbeta-1, but also contains the growth factors TGFbeta-2, BMP-2, BMP-3, BMP-7, IGF-1, and possibly VEGF. Other growth factors might be present in COLLOSSE, but were not identified due to inherent detection limits of the used ELISA and mass spectrometry techniques. The number of osteoinductive factors in COLLOSSE causes a synergistic effect, explaining the new bone formation found in previously described in vivo studies, with much lower growth factor concentrations when compared with recombinant BMPs.
(c) 2008 Wiley Periodicals, Inc.