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 (CoCl), 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 CoCl. 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 CoCl suppressed hDPC proliferation, 50 μmol/L CoCl increased the number of STRO-1 cells. Moreover, CoCl dose dependently induced stem cell marker expression. Additionally, CoCl 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 CoCl on ALP activity.

Conclusions: This study indicated that CoCl may enhance hDPC stemness.