Effect of conditioned medium derived from a clone cell of epithelial rests of Malassez on enamel crystallization in...

We have previously isolated the epithelial rests of Malassez (ERM) clone cells with strong Amelx expression, named as ERM-2, from the crude ERM cells. In the present study, we examined whether conditioned medium (CM) derived from cultured ERM-2 promotes the crystallization of immature enamel in tooth germs. Tooth germs from postnatal day 3 mice were incubated with ERM-2 conditional medium (CM). ERM-2 cells were transfected with si-RNA targeting specific enamel matrix proteins (EMPs). After 2 days of incubation, each CM was collected and employed to culture the tooth germs. The surface layers of the enamel structure were examined with a scanning electron microscope (SEM). Tooth germs cultured with ERM-2 CM on days 3 and 7 showed elongation and densification of the columnar structures in SEM analysis. The columnar structures became denser and aggregated forming a HAP-like hexagonal columnar structure 14 days after culture in ERM-2 CM. In contrast, no clear columnar structures were observed in ERM-2 CM with si-RNA of each EMPs. In conclusion, the present study demonstrated that CM derived from ERM-2 could form enamel-like structures on the surface of the tooth germ. ERM-2 may provide the possibility for the clinical use of enamel regeneration.