Torzilli P A, Grigiene R
Laboratory for Soft Tissue Research, Hospital for Special Surgery, New York, New York 10021-4892, USA.
Osteoarthritis Cartilage. 1998 Jul;6(4):260-8. doi: 10.1053/joca.1998.0119.
To study the effect of a continuous cyclic mechanical load on the release of newly synthesized proteoglycans (PGs) from mature bovine articular cartilage.
Viable cartilage explants were continuously loaded with 1 MPa cyclic stress at 1 Hz frequency for 24 h, and the release of labeled (35SO4) PGs measured before, during and after application of the compressive load. To separate the effect of active chondrocyte catabolism from that of passive PG release, PG release in live explants, with and without protease inhibitors to inhibit PG breakdown, was compared to PG release in explants whose chondrocytes were killed prior to loading.
In live explants, a continuous cyclic load significantly reduced PG release by as much as 50% compared to unloaded explants. In killed explants which were unloaded, the PG release increased five to 10 times, while a cyclic load reduced PG release to that found in viable, loaded explants. Twenty-four hours after load removal PG release in all loaded explants returned (increased) to that of the unloaded explants.
These results indicate that PG release from the cartilage matrix is inhibited by continuous cyclic mechanical loading, independent of cellular metabolism, and suggest that a primary mechanism for reducing PG release is by decreasing the interstitial porosity through which the PGs can escape.
研究持续循环机械负荷对成熟牛关节软骨新合成蛋白聚糖（PGs）释放的影响。
将活的软骨外植体以1Hz频率持续施加1MPa循环应力24小时，并在施加压缩负荷之前、期间和之后测量标记的（35SO4）PGs的释放。为了区分活性软骨细胞分解代谢与被动PG释放的影响，将添加和不添加蛋白酶抑制剂以抑制PG分解的活外植体中的PG释放，与加载前软骨细胞已死亡的外植体中的PG释放进行比较。
在活的外植体中，与未加载的外植体相比，持续循环负荷显著降低PG释放多达50%。在未加载的死亡外植体中，PG释放增加了五到十倍；而循环负荷使PG释放降低到活的、加载的外植体中的水平。负荷去除24小时后，所有加载外植体中的PG释放恢复（增加）到未加载外植体的水平。
这些结果表明，软骨基质中PG的释放受到持续循环机械负荷的抑制，与细胞代谢无关，并提示减少PG释放的主要机制是通过降低PG可逸出的间质孔隙率。
