Malassez-epithelial cells promote osteoblastic cell proliferation and migration in co-culture

Objectives: The periodontal ligament contains the epithelial rests of Malassez (ERM), derived from Hertwig's epithelial root sheath. Previous studies showed that ERM cells inhibited osteoblastic mineralization in co-culture systems. The present study investigated the effect of Malassez–epithelial cells on osteoblastic cell proliferation and migration in the co-culture system. Methods: ERM cells were isolated from the porcine periodontal ligament and cultured using an outgrowth method. Osteoblast-like cells, MC3T3-E1, were applied to 6-well transwell units coated with collagen I, and were co-cultured with ERM cells, fibroblasts or samples with no cells. The cells were incubated in keratinocyte growth medium (Cambrex) containing 1.8 mM Ca2+. After incubation for 24, 48, 72 and 96h, the number of the MC3T3-E1 cells stained with hematoxyline was counted under light microscope. The migration of MC3T3-E1 cells was determined based on the Boyden's chamber method. Non-migrating cells were removed with a flattened swab and migrating cells on the underside of the chamber were stained, and the extent of migration was determined by directly counting stained cells. The statistical significance of the difference was analyzed using one-way ANOVA test (n=5). Results: The growth number of MC3T3-E1 cells with a co-culture of ERM was significantly higher than MC3T3-E1 cells without ERM (p<0.01). The migrating number of MC3T3-E1 cells with a co-culture of ERM was significantly higher than MC3T3-E1 cells without ERM (p<0.01). Conclusion: These results indicate that ERM may be involved in cell proliferation and migration of osteoblasts and cementoblasts in the periodontal ligaments.