Figure 4

In vitro osteogenesis of periodontal ligament stem cells. (A) Cells grown in osteogenic media stained positively for alkaline phosphatase (ALP) (A) and Alizarin red (B) after 28 days of culture and for osteocalcin (C) and type I collagen (D) using immunocytochemistry after 21 days of culture. (E) ALP activities in osteogenic condition increased significantly at day 7 when compared with that at day 3, but there was no significant difference in ALP activities at days 3 and 7 in the control group. *P <0.05 versus control group. Magnifications: 100× (A, C) and 200× (B, D). OD, optical density.