The Roles of RUNX1 in the Proliferation and Osteogenic and Adipogenic Differentiation of Dental Pulp Stem Cells

  Objective  To investigate the influence of Runt-related transcription factor 1 (RUNX1) on the proliferation, osteogenic differentiation and adipogenic differentiation of dental pulp stem cells (DPSC) in vitro.

  Methods  DPSCs were transfected through lentiviral vector carrying the target gene RUNX1 and green fluorescent protein (GFP). After 48 h, transfection efficiency was determined with the fluorescent marking of GFP and Western blot. The effect of the overexpression of RUNX1 on DPSC proliferation and colony formation was determined with CCK-8 and colony formation assay; cell cycle of DPSC was detected by flow cytometry. RUNX1 siRNA was transfected into the DPSCs. After mineralized induction, the effect of RUNX1 overexpression/silencing on the osteogenetic differentiation of DPSC was tested by alkaline phosphatase (ALP) staining and alizarin red staining. After adipogenic induction, oil red O staining was done in order to observe the effect of overexpression/silencing of RUNX1 on the adipogenic differentiation of DPSC.

  Results  RUNX1 protein was overexpressed in DPSC after lentiviral transfection. Fluorescent test showed successful transfection of lentiviral transfection and over 70% of the cells showed stable expression of GFP protein. The proliferation and colony-formation efficiency of DPSC was enhanced significantly and the proportion of DPSCs in the S phase was significantly increased in the RUNX1-overexpessed group (P<0.05). ALP activity and mineralized nodule formation ability increased, while lipid droplets decreased in the RUNX1-overexpessed group (P<0.05). ALP activity and mineralized nodule formation ability decreased, while lipid droplets increased in the RUNX1 knockdown group (P<0.05).

  Conclusion  RUNX1 promotes DPSC proliferation and osteogenic differentiation while it inhibits DPSC adipogenic differentiation.