Extracellular Signal-Regulated Kinase 1/2 Is Involved in Ascorbic Acid–Induced Osteoblastic Differentiation in Periodontal Ligament Cells

Background: Periodontal ligament (PDL) cells possess osteoblast-like properties and play key roles in periodontal regeneration. Previously, we have reported that ascorbic acid promotes the osteoblastic differentiation of PDL cells by modulating the type I collagen–integrin interaction. However, the signaling pathway activated following collagen–integrin interaction is still unclear. In this study, we examined the involvement of extracellular signal-regulated kinase (ERK)1/2 in the expression of osteoblastic marker genes such as the osteoblast-specific transcriptional factor runt-related transcription factor 2 (Runx2), alkaline phosphatase (ALP), and osteocalcin (OCN) in PDL cells.Methods: PDL cells were cultured on a conventional or type I collagen–coated dish in the presence or absence of ascorbic acid and examined for ALP activity and osteoblastic marker genes. For detection of ERK1/2, cells were plated on a petri (non-adhesive) dish or type I collagen–coated dish, and Western blot analysis was performe...