OBJECTIVE: The objective of this study was to investigate the effects of hypoxia on osteoblast cell gene expression. The genes evaluated included: growth factors (such as BMPs and TGF©¬), internal cell signaling (the smads), and osteoblast matrix and associated protein production (osteocalcin, MMPs, osteopontin).
METHODS: For this study, a well-characterized human osteoblastic cell line, MG-63, was utilized. Cells were cultured in flasks and grown under hypoxic, and for comparison, normal atmospheric conditions over two different lengths of exposure (2 and 4 days). To evaluate osteogenic gene expression, cDNA expression arrays that contained cDNA fragments from genes associated with osteogenesis and inflammation were utilized. Comparing the signal intensity of different osteogenesis-related genes with that of the positive control housekeeping genes imprinted in several positions on the array membrane, the relative abundance of particular transcript was estimated.
RESULTS: There was a change in gene expression under hypoxia; some genes were down-regulated while others were up-regulated. Overall, however, the results indicated a net down-regulation in gene expression. For example, BMP-2 gene expression of cells exposed to hypoxia was decreased 34% by day 2 and 41% by day 4. Similarly, TNFa gene expression was decreased 53% by day 2 and 74% in day 4 cultures.
CONCLUSION: Thus, it appears that hypoxia influences osteogenic gene expression in this cell line. More studies are currently underway to examine further the role of hypoxia on bone cells and osteogenesis, including the influence of various chemotherapeutic agents. These studies may help us to develop more effective treatments against various bone diseases, including periodontitis.