title: Heat treatment of BMP-2 depots on implant materials generates an immobilized layer of BMP-2 with pronounced bioactivity.
abstract: Bone cells seeded directly on depots of bone morphogenetic protein-2 (BMP-2) increase alkaline phosphatase (ALP) expression. Heating of such BMP-2 depots to 100 degrees C augmented the intensity of this local ALP induction. To understand this unexpected finding, we investigated the effect of heat treatment on BMP-2 depots more closely. Using a novel bioassay based on ALP-induction of remote cells, we found that the amount of released bioactive BMP-2 from heat-treated depots decays within days and could be described by an exponential function. From this function, we expected that pre-incubation of BMP-2 depots in culture medium for 4 weeks renders them insufficient to induce ALP. However, preincubated, heat-treated depots still induced maximal ALP, unless treated with the selective BMP-2 inhibitor noggin. Furthermore, heat treatment of BMP-2 depots generated a layer of immunoreactive BMP-2 at the surface of the carrier. In contrast, BMP-2 was washed off completely if heat treatment of adsorbed protein was omitted. Results show that heat treatment generates both a soluble pool of BMP-2 and a material-bound layer of BMP-2 in which the protein is protected against degradation. Therefore, heat treatment appears useful to locally immobilize BMP-2 on various implant surfaces.
authors.affiliation: Institute of Physiology, University of Duisburg-Essen, Hufelandstr. 55, 45122 Essen, Germany.
authors.forename: Lars
authors.initials: L
authors.lastname: Winkler
authors.forename: Dieter
authors.initials: D
authors.lastname: Bingmann
authors.forename: Martin
authors.initials: M
authors.lastname: Wiemann
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis*; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000737:chemistry; D001842:Bone and Bones / Q000166:cytology / Q000201:enzymology*; D018929:Cell Culture Techniques / Q000379:methods; D002460:Cell Line; D020099:Coated Materials, Biocompatible; D003692:Delayed-Action Preparations / Q000737:chemistry; D010450:Endopeptidases / Q000096:biosynthesis*; D006358:Hot Temperature; D006801:Humans; D019736:Prostheses and Implants; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000737:chemistry
chemical_list: C525718:BMP2 protein, human; D001426:Bacterial Proteins; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D020099:Coated Materials, Biocompatible; D003692:Delayed-Action Preparations; D016212:Transforming Growth Factor beta; D010450:Endopeptidases; C087822:alkaline protease