Dental pulp cells promote the expression of receptor activator of nuclear factor-κB ligand, prostaglandin E and substance P in mechanically stressed periodontal ligament cells.

Objective: This study investigated the expression of receptor activator of nuclear factor-κB ligand (RANKL) in periodontal ligament (PDL) cells co-cultured with dental pulp (DP) cells following mechanical stress in vitro. Furthermore, the expression of prostaglandin (PG) E and substance P (SP) by the PDL cells and by the DP cells were also examined.

Design: PDL and DP cells were obtained from 10 rats. The experimental group consisted of PDL cells subjected to centrifugal force as mechanical stress and co-cultured with DP cells. The 3 control groups of PDL cells were: 1) PDL cells without mechanical stress, 2) PDL cells treated with mechanical stress and 3) PDL cells co-cultured with DP cells. The 2 control groups of DP cells were: 1) DP cells without mechanical stress and 2) DP cells co-cultured with PDL cells. In each group, both cells were examined at day 1 and day 3, and mRNA levels of RANKL by PDL cells were analyzed using Real time quantitative Reverse Transcription (RT)-PCR. Furthermore, RANKL expression was observed using Immunofluorescence staining. PGE and SP expression levels by PDL cells and DP cells were characterized by ELISA analysis.

Results: The expression of RANKL by PDL cells under mechanical stress increased by co-culture with DP cells. PGE and SP expressions were increased in the group of PDL cells subjected to mechanical stress and co-cultured with DP cells.

Conclusion: DP cells may facilitate the expression of RANKL in PDL cells under mechanical stress via PGE and SP.