Objective: To investigate the effect of hypoxia on the expression of matrix metalloproteinase (MMP) and tissue inhibitors of matrix metalloproteinase (TIMP) in human periodontal ligament fibroblasts (HPDLF).
Methods: HPDLF were cultured in α-minima essential medium (α-MEM) and subcultured at confluence. In the hypoxic groups, cells were incubated in a humidified atmosphere of 1%O(2), 5%CO(2), 94%N(2) at 37°C for 12, 24 and 48 h, respectively. In the normoxic control group, cells were incubated under normoxic conditions of 20%O(2), 5%CO(2), 75%N(2). The mRNA expression of MMP and TIMP was measured using reverse transcription-polymerase chain reaction (RT-PCR). The data was analyzed by Student's t test, one-way ANOVA and LSD test with SPSS 13.0 software package.
Results: The expression of MMP-2, TIMP-1 and TIMP-2 mRNA in the hypoxia groups was higher than that in control. The expression of MMP-2 mRNA in hypoxic groups showed a significantly increasing trend. There was significant difference between the hypoxic group and the normoxic control group in the expression of MMP-2 mRNA in HPDLF (P < 0.01). The expression of TIMP-1, TIMP-2 mRNA in hypoxic groups of 12 h was momentarily increased. There was significant difference between the hypoxic 12 h group and the normoxic control group in the expression of TIMP-1, TIMP-2 mRNA in HPDLF (P < 0.05). However, with prolonged hypoxia time, the expression of TIMP-1, TIMP-2 mRNA in hypoxic groups showed a significantly declining trend, there were significant differences between the hypoxic 12, 24 and 48 h group and the normoxic control group in the expression of TIMP-2 mRNA in HPDLF (P < 0.05). The expression of MMP-1 mRNA in hypoxic groups of 12 h was momentarily decreased and then increased after 24 h of hypoxia. There were significant differences between the hypoxic 48 h group and the normoxic control group in the expression of MMP-1 mRNA in HPDLF (P < 0.05). There were significant differences between the hypoxic 12 h group and the normoxic control group in the ratio of MMP-1/TIMP-1 mRNA (P < 0.05). The ratio of MMP-2/TIMP-2 mRNA in the hypoxia group significantly increased compared with normoxic group. There were significant differences between the hypoxic group and the normoxic control group in the ratio of MMP-2/TIMP-2 mRNA (P < 0.05).
Conclusions: Hypoxia could change the expression of MMP and TIMP mRNA and other relevant growth factors and also lead to the imbalance of MMP-2/TIMP-2 mRNA expression. It is suggested that the imbalance of MMP-2/TIMP-2 expression may be closely correlated with the occurrence and development of periodontal disease and play an important role in the process of periodontal tissue destruction in periodontitis.