Hydrostatic pressure induces expression of interleukin 6 and tumour necrosis factor α mRNAs in a chondrocyte-like cell line

Objective - To clarify the effect of pressure on the expressions of proteoglycan core protein and metabolism related cytokines in a chondrocyte- like cell line, HCS-2/8. Methods - HCS-2/8 cells were exposed to 1, 5, 10, or 50 MPa of hydrostatic pressure (HP) for two hours, and mRNA expressions of interleukin 6 (IL6) and tumour necrosis factor α (TNFα) were examined by using reverse transcription-polymerase chain reaction (RT-PCR) method with specific primer sets; and mRNA of proteoglycan core protein, stromelysin, and tissue inhibitor of metalloproteinase 1 (TIMP1) were measured with northern blotting. Results - HP exposure caused temporal morphological changes of the cells, but did not affect cellular viability. IL6 and TNFα mRNA expressions were not observed in the control cells under the atmospheric pressure, whereas in the cells treated with HP, pressure dependent enhancement of IL6 mRNA expression was observed between 30 minutes and four hours after the HP release. TNFα mRNA expression also increased 30 minutes after the exposure to 50 MPa of HP and disappeared four hours later. Proteoglycan core protein mRNA levels increased between 30 minutes and four hours after the exposure to 1 or 5 MPa of HP, whereas the levels decreased after 10 or 50 MPa of HP. Stromelysin and TIMP1 mRNA signals did not respond to HP. Conclusions - HP at excessively high levels induced IL6 and TNFα expression and reduced the expression of proteoglycan core protein, while physiological levels of HP increased the expression of proteoglycan core protein. These findings are important when considering the pathology of osteoarthritis.