Periodontal ligament (PDL) cells appear to play important functional roles in response to mechanical stress. We hypothesized that
hypoxia caused by a deformation of blood vessels and the following ischaemia may play a crucial role in differential gene expression in PDL cells affected by mechanical stress. Gene induction in cultured human PDL cells by
hypoxia was analyzed using
cDNA array, followed by RT-PCR analysis. Eleven
hypoxia-responsive genes were found differentially expressed under low-
oxygen conditions in PDL cells. Among them, CCR2,
CC chemokine ligand 2 (CCL2) receptor was studied in more detail since little information is available on the role of
chemokines in adaptive responses of PDL cells under
hypoxia. Here we investigate whether CCR2 mediates the signalling to maintain the homeostasis of PDL cells. We found that cell death of PDL cells was induced under
hypoxia with down-regulation of CCL2
mRNA expression. However, the exogenous CCL2 prevented PDL cell death under
oxygen shortage with the increment of cellular inhibitor of apoptosis (cIAP)
mRNA expression. The present study demonstrated substantial effects of
hypoxia on gene expression of CCL2 and CCR2 in PDL cells, indicating that mechanical loading accompanied with mild
hypoxia allows PDL cells to elicit adaptive responses with up-regulation of CCR2.