Abstract
Bone marrowโderived mesenchymal stem cells (BMโMSCs) are the popular seed cells for regenerative medicine, and there has been a rapid increase in the number of BMโMSCโbased clinical trials. However, the safety of these cells should also be closely studied. In this study, spontaneous calcification of BMโMSCs from rats was evaluated in normoxia (20% O~2~) without osteogenic medium after continuous culture for 21 days; obvious mineralized nodules were observed, which were positive for Alizarin Red, collagenโI (ColโI), osteocalcin (OC) and alkaline phosphatase (ALP), and mainly consisted of C, O and Ca elements. Interestingly, hypoxia (2% O~2~) significantly inhibited this spontaneous calcification. In addition, the ALP and calcium content of rBMโMSCs were sharply reduced. Based on RTโPCR results, the expression of osteogenic genes (Cbfa1/Runx2, ColโI, ALP, and OC) was reduced compared to that in normoxia. These results demonstrate a natural and unique characterization of rat BMโMSCs in normoxia after continuous culture and highlight the inhibiting effects of hypoxia. Finally, this study contributes to the information regarding the application of BMโMSCs in the regeneration of various tissues. J. Cell. Biochem. 113: 1407โ1415, 2012. ยฉ 2011 Wiley Periodicals, Inc.