Bone formation in CaP-coated and noncoated titanium fiber mesh

The osteogenic activity of calcium phosphate (CaP)-coated and noncoated porous titanium (Ti) fiber mesh loaded with cultured syngeneic osteogenic cells after prolonged in situ culturing was compared in a syngeneic rat ectopic assay model. Rat bone marrow (RBM) cells were loaded onto the CaP-coated and noncoated Ti scaffolds using either a droplet or a suspension loading method. After loading, the RBM cells were cultured for 8 days in vitro. Thereafter, implants were subcutaneously placed in 39 syngeneic rats. The rats were euthanized and the implants retrieved at 2, 4, and 8 weeks postoperatively. Further, in the 8 week group fluorochrome bone markers were injected at 2, 4, and 6 weeks. Histological analysis demonstrated that only the CaP-coated meshes supported bone formation. The amount of newly formed bone varied between single and multiple spheres to filling a significant part of the mesh porosity. In the newly formed bone, osteocytes embedded in a mineralized matrix could be observed clearly. On the other hand, in the noncoated titanium implants, abundant deposition of calcium-containing material was seen. This deposit lacked a bonelike tissue organization. Further analysis revealed that the cell-loading method did not influence the final amount of bone formation. In CaP-coated implants the accumulation sequence of the fluorochrome markers showed that bone formation started on the mesh fibers. In conclusion, our results prove that the combination of a thin CaP coating, Ti-mesh, and RBM cells can indeed generate ectopic bone formation after prolonged in vitro culturing. No effect of the loading method was observed on the final amount of bone. (C) 2003 Wiley Periodicals, Inc.