The effects of epithelial rests of Malassez cells on periodontal ligament fibroblasts against centrifugal forces in vitro

ObjectivesThe purpose of this study was to investigate the effects of epithelial rests of Malassez (ERM) cells on PDL fibroblasts in vitro against centrifugal forces using a co-culture system.Materials and methodsPDL fibroblasts and ERM cells derived from porcine were used. PDL fibroblasts were seeded in 6-well dishes. ERM cells plated in a chamber with a 0.4 μm pore membrane were placed into the wells for 5 days, and then were centrifuged as a mechanical stress. Vascular endothelial growth factor (VEGF), heat shock protein (HSP) 27, osteocalcin (OCN), bone sialoprotein (BSP), receptor activator of NF-κB ligand (RANKL) and osteoprotegerin (OPG) mRNA levels were analyzed, and RANKL expression was analyzed at the protein level.ResultsVEGF mRNA expression by PDL fibroblasts co-cultured with ERM cells with or without force was higher than those cultured without ERM cells. HSP27 mRNA expression by PDL fibroblasts cultured without ERM cells with force was higher than those co-cultured with ERM cells. OCN and BSP mRNA expression by PDL fibroblasts co-cultured with ERM cells was significantly lower than without ERM cells with or without force. The expressions of RANKL by PDL fibroblasts co-cultured with ERM cells with force were higher than those without ERM cells. OPG mRNA expression by PDL fibroblasts co-cultured with ERM cells without force were lower than those without ERM cells.ConclusionThese results demonstrate that ERM cells play an important role in preventing PDL cells from being susceptible to dento-alveolar ankylosis during compression of the PDL.