Horisberger Monika, Fortuna Rafael, Leonard Timothy R, Valderrabano Victor, Herzog Walter
Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada.
Clin Biomech (Bristol). 2012 Mar;27(3):292-8. doi: 10.1016/j.clinbiomech.2011.09.012. Epub 2011 Oct 20.
Cartilage loading is associated with the onset and progression of osteoarthritis and cell death may play an important role in these processes. Although much is known about cell death in joint impact loading, there is no information on joints loaded by muscular contractions. The aim of this study was to evaluate the influence of muscle generated eccentric and concentric submaximal joint loading on chondrocyte viability. We hypothesised that eccentric muscle activation leads to increased cell death rates compared to concentric loading and to controls.
16 rabbits received either 50 min of uni-lateral, cyclic eccentric (n=8) or concentric (n=8) knee loading. Muscle activation for these dynamic conditions was equivalent to an activation level that produced 20% of maximum isometric force. Contralateral joints served as unloaded controls. Cell viability was assessed using confocal microscopy.
Eccentric contractions produced greater knee loading than concentric contractions. Sub-maximal contractions caused a significant increase in cell death in the loaded knees compared to the unloaded controls, and eccentric loading caused significantly more cell death than concentric loading.
Cyclic sub-maximal muscle loading of the knee caused increased chondrocyte death in rabbits. These findings suggest that low levels of joint loading for prolonged periods, as occurs in endurance exercise or physical labour, may cause chondrocyte death, thereby predisposing joints to degeneration.
软骨负荷与骨关节炎的发生和发展相关，细胞死亡可能在这些过程中起重要作用。尽管关于关节冲击负荷下的细胞死亡已有很多了解，但对于肌肉收缩所加载的关节尚无相关信息。本研究的目的是评估肌肉产生的离心和向心次最大关节负荷对软骨细胞活力的影响。我们假设与向心负荷及对照组相比，离心肌肉激活会导致细胞死亡率增加。
16只兔子接受50分钟的单侧、周期性离心（n = 8）或向心（n = 8）膝关节负荷。这些动态条件下的肌肉激活相当于产生最大等长力20%的激活水平。对侧关节作为未加载的对照。使用共聚焦显微镜评估细胞活力。
离心收缩产生的膝关节负荷比向心收缩更大。与未加载的对照相比，次最大收缩导致加载膝关节中的细胞死亡显著增加，且离心负荷导致的细胞死亡明显多于向心负荷。
膝关节的周期性次最大肌肉负荷导致兔子软骨细胞死亡增加。这些发现表明，耐力运动或体力劳动中出现的长时间低水平关节负荷可能会导致软骨细胞死亡，从而使关节易发生退变。
