Cobalt Chloride Enhances the Stemness of Human Dental Pulp Cells.

INTRODUCTION: Hypoxia is a factor in controlling stem cell stemness. We investigated if cobalt chloride (CoCl2 ), a chemical agent that mimics hypoxia in vitro, affected human dental pulp cell (hDPC) stemness by examining cell proliferation, stem cell marker expression, and osteogenic differentiation.

METHODS: hDPCs were cultured with or without 25 or 50 μmol/L CoCl2 . The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was used to determine cell proliferation. The number of STRO-1+ cells was determined by flow cytometry. The messenger RNA expression of the stem cell markers REX1, OCT4, SOX2, and NANOG and the osteogenic-associated genes ALP, COLI, and RUNX2 were evaluated using reverse transcription polymerase chain reaction or real-time polymerase chain reaction. Osteogenic differentiation was assessed by alkaline phosphatase (ALP) activity and mineralization assays.

RESULTS: Although 25 and 50 μmol/L CoCl2 suppressed hDPC proliferation, 50 μmol/L CoCl2 increased the number of STRO-1+ cells. Moreover, CoCl2 dose dependently induced stem cell marker expression. Additionally, CoCl2 treatment suppressed osteogenic-associated gene expression, ALP activity, and calcium deposition. The addition of apigenin, a hypoxia-inducible factor 1-alpha inhibitor, reversed the inhibitory effect of CoCl2 on ALP activity.

CONCLUSIONS: This study indicated that CoCl2 may enhance hDPC stemness.