Effects of parathyroid hormone and cytokines on prostaglandin E synthesis and bone resorption by human periodontal ligament fibroblasts.

Cultured human periodontal ligament fibroblasts showed synergistic elevations in the synthesis of prostaglandin E and production of cAMP by the administration of parathyroid hormone and cytokines (interleukin 1 alpha, -1 beta, or tumour necrosis factor-alpha). Unstimulated conditioned media derived from these fibroblasts contained bone-resorbing activity. In addition, conditioned media generated by cytokine-or parathyroid hormone-treated fibroblasts showed further increases in bone-resorbing activity. The effects were additive when the hormone was combined with either one of the cytokines in stimulating bone resorption. These findings suggest that the effect of parathyroid hormones and cytokines together on bone resorption can be mediated in part by human periodontal ligament fibroblasts via PGE production and subsequent PGE action on the osteoclasts.