Stimulation of bone resorption and cell proliferation in vitro by human gingival fibroblasts from patients with periodontal disease

Abstract

In the present communication we report that fibroblasts, isolated from human gingiva obtained from 13 different patients, secreted soluble product(s) which can promote bone resorption in vitro. Fibroblasts were isolated from explants of human gingiva, subcultured, grown to confluent monolayers, subsequently cultured in growth arrest media for 0-72 h and conditioned media harvested. Bone resorption was assessed in cultured mouse calvarial bone by quantifying the mobilization of minerals and the release of lysosomal enzymes. Human fibroblast-conditioned media (HFCM) dose-dependently stimulated the release of 45Ca from prelabelled bones and the mobilization of stable calcium and inorganic phosphate from unlabelled bones. In addition, HFCM increased the release of beta-glucuronidase and beta-N-acetylglucosaminidase from the calvaria. No effect of HFCM on the release of 45Ca from dead bones could be seen. HFCM caused a dose-dependent increased degradation of bone matrix proteins, as assessed by the release of 3H from [3H]proline-labelled calvaria. The stimulation of 45Ca release could already be seen after 3-12 h of treatment. Treatment of the bones with HFCM for 12 h was sufficient to obtain a prolonged stimulation of 45Ca release. Bones cultured in the presence of HFCM showed an increased number of osteoclasts. Calcitonin, but not indomethacin, inhibited 45Ca release stimulated by HFCM. Ultrafiltration of HFCM did not cause any loss of the 45Ca release response. The amount of bone-resorbing activity produced by the gingival cells was proportional to the number of cells. In addition, HFCM stimulated the proliferation of human fibroblasts and osteoblast-enriched mouse calvarial bone cells. It is concluded that human gingival fibroblasts secrete one or several factors that can stimulate osteoclastic bone resorption in vitro by a prostaglandin-independent pathway.