ABSTRACT
Periodontal tissue has a unique structure in that the human periodontal ligament (hPDL) lies between the hard tissues of cementum and alveolar bone. Although the role of cytokines in hPDL function is not clearly understood, we investigated the effect of mechanical stress as hydrostatic pressure (HP) on cytokine expression in hPDL cells.The hPDL cells were obtained from a healthy maxillary third molar. After the 3rd to 4th passage, the cells were exposed to HP ranging from 1 MPa to 6 MPa as previously described. The expression of cytokine mRNA was determined by RT-PCR and cytokines in the culture supernatants were assessed by enzyme-linked immunosorbent assay (ELISA).The exposure to 6 MPa of HP caused no morphological changes of hPDL cells, and did not affect cellular viability. No expression of IL-1β, IL-6, IL-8, TNF-α, RANK, RANKL or OPG mRNA was observed in the control cells under atmospheric pressure, whereas in hPDL cells treated with HP, enhancement of IL-6, IL-8, RANKL and OPG mRNA expression was observed between 10 and 60 minutes after the exposure to HP. After the exposure to HP, the production of IL-6 and TNF-α were induced significantly in hPDL cells, but IL-1β and IL-8 were not produced.These results suggest that hPDL cells may play a role in the production of cytokines in response to mechanical stress <i>in vivo</i>.