Objective. To investigate the effects of the hypoxia inducible factor-1 (HIF-1) activation–mimicking agent cobalt chloride (CoCl2) on the osteogenic differentiation of human mesenchy-mal stem cells (hMSCs) and elucidate the underlying mole-cular mechanisms. Study design. The dose and exposure periods for CoCl2 in hMSCs were optimized by cell viability assays. After confirmation of CoCl2-induced HIF-1α and vas-cular endothelial growth factor expression in these cells by RT-PCR, the effects of temporary preconditioning with CoCl2 on hMSC osteogenic differentiation were evaluated by RT- PCR analysis of osteogenic gene expression, an alkaline phos-phatase (ALP) activity assay and by alizarin red S staining. Results. Variable CoCl2 dosages (up to 500 µM) and exposure times (up to 7 days) on hMSC had little effect on hMSC survival. After CoCl2 treatment of hMSCs at 100 µM for 24 or 48 hours, followed by culture in osteogenic differentiating media, several osteogenic markers such as Runx-2, osteocal-cin and osteopontin, bone sialoprotein mRNA expression level were found to be up-regulated. Moreover, ALP acti-vity was increased in these treated cells in which an accele-rated osteogenic capacity was also verified by alizarin red S staining. Conclusions. The osteogenic differentiation poten-tial of hMSCs could be preserved and even enhanced by CoCl2 treatment.

• Yeon-Hee Moon(Dental Science Research Institute, School of Dentistry, Chonnam National University)
• Jung-Wan Son(Dental Science Research Institute, School of Dentistry, Chonnam National University)
• Jung-Sun Moon(Dental Science Research Institute, School of Dentistry, Chonnam National University)
• Jee-Hae Kang(Dental Science Research Institute, School of Dentistry, Chonnam National University)
• Sun-Hun Kim(Dental Science Research Institute, School of Dentistry, Chonnam National University)
• Min-Seok Kim(Dental Science Research Institute, School of Dentistry, Chonnam National University) Correspondence