Leppänen Olli V, Sievänen Harri, Jokihaara Jarkko, Pajamäki Ilari, Kannus Pekka, Järvinen Teppo L N
Medical School and the Institute of Medical Technology, University of Tampere, Tampere, Finland.
PLoS One. 2008 Jul 2;3(7):e2540. doi: 10.1371/journal.pone.0002540.
According to prevailing understanding, skeletal mechano-responsiveness declines with age and this apparent failure of the mechano-sensory feedback system has been attributed to the gradual bone loss with aging (age-related osteoporosis). The objective of this study was to evaluate whether the capacity of senescent skeleton to respond to increased loading is indeed reduced as compared to young mature skeleton.
108 male and 101 female rats were randomly assigned into Exercise and Control groups. Exercise groups were subjected to treadmill training either at peak bone mass between 47-61 weeks of age (Mature) or at senescence between 75-102 weeks of age (Senescent). After the training intervention, femoral necks and diaphysis were evaluated with peripheral quantitative computed tomography (pQCT) and mechanical testing; the proximal tibia was assessed with microcomputed tomography (microCT). The microCT analysis revealed that the senescent bone tissue was structurally deteriorated compared to the mature bone tissue, confirming the existence of age-related osteoporosis. As regards the mechano-responsiveness, the used loading resulted in only marginal increases in the bones of the mature animals, while significant exercise-induced increases were observed virtually in all bone traits among the senescent rats.
The bones of senescent rats displayed a clear ability to respond to an exercise regimen that failed to initiate an adaptive response in mature animals. Thus, our observations suggest that the pathogenesis of age-related osteoporosis is not attributable to impaired mechano-responsiveness of aging skeleton. It also seems that strengthening of even senescent bones is possible--naturally provided that safe and efficient training methods can be developed for the oldest old.
根据普遍的认识，骨骼的机械反应性会随着年龄增长而下降，而这种机械感觉反馈系统的明显衰退被认为是由于衰老过程中骨质逐渐流失（与年龄相关的骨质疏松症）所致。本研究的目的是评估与年轻成熟骨骼相比，衰老骨骼对增加负荷的反应能力是否确实降低。
将108只雄性和101只雌性大鼠随机分为运动组和对照组。运动组在47至61周龄（成熟阶段）的骨量峰值期或75至102周龄（衰老阶段）进行跑步机训练。训练干预后，使用外周定量计算机断层扫描（pQCT）和力学测试评估股骨颈和骨干；使用微型计算机断层扫描（microCT）评估胫骨近端。microCT分析显示，与成熟骨组织相比，衰老骨组织的结构有所恶化，证实了与年龄相关的骨质疏松症的存在。关于机械反应性，施加的负荷仅使成熟动物的骨骼有少量增加，而在衰老大鼠的几乎所有骨特征中均观察到运动诱导的显著增加。
衰老大鼠的骨骼表现出对运动方案做出反应的明显能力，而该运动方案在成熟动物中未能引发适应性反应。因此，我们的观察结果表明，与年龄相关的骨质疏松症的发病机制并非归因于衰老骨骼的机械反应性受损。似乎即使是衰老的骨骼也有可能得到强化——前提是能够为高龄老人开发出安全有效的训练方法。
