Dental pulp and periodontal ligament cells support osteoclastic differentiation

Odontoclasts and cementoclasts are considered to play major roles in the internal resorption of dentin and the external resorption of tooth roots. In this study, we evaluated the osteoclast-inducing ability of human dental pulp and periodontal ligament cells, which are mesenchymal cells in dental tissues. These cells expressed RANKL and OPG mRNA constitutively. As osteoclast precursors, CD14(+) monocytes derived from human peripheral blood were isolated, and incubated together with human dental pulp or periodontal ligament cells. Both cell types spontaneously induced the differentiation of CD14(+) monocytes into osteoclasts without osteotropic factors. These results suggest that dental pulp and periodontal ligament cells are involved in regulating the differentiation and function of osteoclasts.