Dental pulp cells promote the expression of receptor activator of nuclear factor-κB ligand, prostaglandin E2 and substance P in mechanically stressed periodontal ligament cells

• DP cells promote the response to mechanical stress in PDL cells.
• Co-culture system is useful to investigate the intercommunication between cells.
• DP cells affect PDL cells via soluble factor in medium.

ObjectiveThis 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) E2 and substance P (SP) by the PDL cells and by the DP cells were also examined.DesignPDL 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. PGE2 and SP expression levels by PDL cells and DP cells were characterized by ELISA analysis.ResultsThe expression of RANKL by PDL cells under mechanical stress increased by co-culture with DP cells. PGE2 and SP expressions were increased in the group of PDL cells subjected to mechanical stress and co-cultured with DP cells.ConclusionDP cells may facilitate the expression of RANKL in PDL cells under mechanical stress via PGE2 and SP.