Mechanical response of chondrocyte under intermittent hydrostatic pressure loading.-Regeneration of Articular Cartilage

软骨细胞分离自兔关节的关节软骨。将细胞暴露于0.5 Hz的间歇静水压力（IHP），范围为1-5 MPa，持续1 hr。压力加载30 min后，提取总RNA，并通过竞争性RT-PCR分析与软骨代谢相关的mRNA表达。蛋白多糖的表达在5 MPa的IHP作用下无明显变化，但II型胶原的表达明显增加。所有细胞均未检测到I型和X型胶原的表达。结果表明，5 MPa的IHP可抑制软骨细胞的终末分化，促进软骨代谢。将人牙周膜（hPDL）细胞置于0.5Hz的1-6 MPa的IHP中培养1h，6 MPa的IHP可促进IL-6、IL-8、RANKL和OPG的表达。IL-6和IL-8是炎性细胞因子，RANKL和OPG是与破骨细胞分化相关的细胞因子。据报道，6 MPa的静水压力是人类生理咬合压力水平。这些结果表明，生理性IHP对炎性细胞因子的表达和骨代谢有影响，为阐明骨关节炎的部分发病机制提供了线索。

Chondrocytes were isolated from the articular cartilage of rabbit joints. The cells were exposed to 0.5 Hz of intermittent hydrostatic pressure(IHP) ranging from 1-5 MPa for 1 hr. After 30 minutes of pressure loading, total RNA was extracted and analyzed by competitive RT-PCR for mRNA expression relating to cartilage metabolism. The expression of proteoglycan did not changed following the exposure to 5 MPa of IHP, but the expression of collagen type II markedly increased. The expression of collagen type I and X were not detected in all cells. These results showed that the exposure to 5 MPa of IHP could inhibit terminal differentiation of chondrocytes and enhance cartilage metabolism. Five MPa of IHP had positive effect on cartilage metabolism.Human periodontal ligament(hPDL) cells were also loaded to 0.5 Hz of IHP ranging from 1-6 MPa for 1 hr. The exposure to 6 MPa of IHP enhanced the expression of IL-6, IL-8, RANKL and OPG. IL-6 and IL-8 are inflammatory cytokines, and RANKL and OPG are cytokines relating to osteoclasts differentiation. Six MPa of hydrostatic pressure is reported as a human physiological occlusal pressure level. These results demonstrated that physiological IHP had effect on inflammatory cytokines expression and bone metabolism.These findings provide a clue to elucidation of a part of the pathogenesis of osteoarthritis.