Epithelial Reactions to Hydroxyapatite: An in Vivo and in Vitro Study

The intention of this study was to investigate the epithelial reactions to hydroxyapatite ceramic in vivo and in vitro. Shortly after implantation in the rat middle ear, hydroxyapatite was found covered by a mucosal layer. In the early postoperative period the implant was almost completely covered by epithelial cells, which were found to proliferate and also showed migratory activity. After longer intervals the implant was completely covered by epithelium, which was composed predominantly of flat polygonal cells and a relatively small number of ciliated epithelium and goblet cells. All cells showed normal morphology. In vitro experiments showed preservation of the morphology of rat middle-ear mucosa explants with good outgrowth of epithelial cells. In these outgrows, the majority of the cells were flat polygonal, but ciliated epithelium was also seen. No difference was found between the absence and presence of hydroxyapatite. Serially cultured cells displayed normal polygonal morphology, but no ciliated cells were found. Ciliated cells were also absent in control experiments without hydroxyapatite. Growth curves obtained in the absence and presence of hydroxyapatite did not differ significantly from each other.