EFFECTS OF HYDROXYAPATITE PARTICLES ON PERIODONTAL-LIGAMENT FIBROBLAST-LIKE CELL BEHAVIOR

ALTHOUGH HYDROXYAPATITE (HA), a synthetic calcium phosphate, is used i n restoring bone defects associated with periodontal diseases, its spe cific effect on the periodontal ligament fibroblast population during the regeneration process is unclear. To determine the cellular events occurring in the presence of HA, human periodontal ligament fibroblast s (HPLF) were isolated and maintained in culture. The specificity of t he cells was evidenced by their morphology, deposition of extracellula r matrix components, and alkaline phosphatase (ALP) activity (as a mar ker of osteoblastic differentiation of HPLF). Phase-contrast investiga tions revealed morphological alterations of cells in contact with HA p articles. Transmission electron microscopy demonstrated the phagocytot ic process of HPLF toward HA particles. Moreover, the presence of HA p articles was significantly related to an increase in the protein synth esis activity and a decrease in the proliferation and ALP-specific act ivity of HPLF. These results provide new information on the phenotypic expression of HPLF, which is comparable to that of osteoblastic cells . A subpopulation of HPLF may be influenced by the presence of HA to u ndergo transient dedifferentiation prior to redifferentiating into ost eoblasts. This process may be important as a means by which HA acts as an osteoconductive material. This experimental study improves our und erstanding of the cellular processes which occur during healing and re generation of periodontal defects after implantation of biomaterials.