Partitioning a daily mechanical stimulus into discrete loading bouts improves the osteogenic response to loading
Partitioning a daily mechanical stimulus into discrete loading bouts improves the osteogenic response to loading
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DOI：
10.1359/jbmr.2000.15.8.1596
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发表时间：
2000-08-01
影响因子：
6.2
通讯作者：
Turner, CH
中科院分区：
文献类型：
--
作者：
Robling, AG;Burr, DB;Turner, CH
单次3分钟的机械负荷可增加大鼠胫骨的骨形成。我们假设更频繁、更短的负荷比单次3分钟的负荷能引起更大的成骨反应。36只成年雌性Sprague-Dawley大鼠的右胫骨每天承受360次54N力的弯曲循环，每次加载1、2、4或6次。6次/天组大鼠每次弯曲60次（60 × 6）；4次/天组大鼠每次弯曲90次（90 × 4）；2和1次/天组每回合分别进行180和360次弯曲循环（180 × 2和360 × 1）。一个无负荷，年龄匹配的对照组（0 × 0）和两个假弯曲组（60 × 6和360 × 1）也包括在内。荧光标记显示，在60 x 6弯曲组中，右胫骨皮质内板层骨形成率（BFR/骨表面[BS]）比左（无负荷）侧增加了10倍。4次、2次和1次弯曲组右胫骨皮质内BFR/BS分别比对照组增加8倍、4倍和4倍。与360 × 1弯曲组相比，90 × 4和60 × 6弯曲组皮质内BFR/BS、矿化表面（MS/BS）和矿物堆积率（MAR）的相对（右减左）值高出65-94%。假弯曲胫骨的相对皮质内骨形成值与对照组（0 × 0）相似。数据显示，360次每日加载周期间隔为60 x 6或90 x 4，比360次一次性加载周期表现出更强的成骨刺激，并且当将机械加载分为离散加载周期时，机械加载更具有成骨性。据推测，随着加载周期的持续不间断，骨细胞对机械刺激变得越来越“失聪”，并且通过在加载周期之间允许一段休息时间，可以增加后续周期的成骨有效性。
A single 3-minute bout of mechanical loading increases bone formation in the rat tibia. We hypothesized that more frequent, shorter loading bouts would elicit a greater osteogenic response than a single 3-minute bout. The right tibias of 36 adult female Sprague-Dawley rats were subjected to 360 bending cycles per day of a 54N force delivered in 1, 2, 4, or 6 bouts on each of the 3 loading days. Rats in the 6-bouts/day group received 60 bending cycles per bout (60 x 6); rats in the 4-bouts/day group received 90 bending cycles per bout (90 x 4); the 2- and 1-bouts/day groups received 180 and 360 bending cycles per bout, respectively (180 x 2 and 360 x 1). A nonloaded, age-matched control group (0 x 0) and two sham-bending groups (60 x 6 and 360 x 1) also were included. Fluorochrome labeling revealed a 10-fold increase in endocortical lamellar bone formation rate (BFR/bone surface [BS]) in the right tibia versus the left (nonloaded) side in the 60 x 6 bending group. Endocortical BFR/BS in the right tibia of the 4-, 2-, and 1-bout bending groups exhibited 8-, 4-, and 4-fold increases, respectively, over the control side. Relative (right minus left) values for endocortical BFR/BS, mineralizing surface (MS/BS), and mineral apposition rate (MAR) were 65-94% greater in the 90 x 4 and 60 x 6 bending groups compared to the 360 x 1 bending group. Sham-bending tibias exhibited relative endocortical bone formation values similar to those collected from the control (0 x 0) group. The data show that 360 daily loading cycles applied at intervals of 60 x 6 or 90 x 4 represent a more osteogenic stimulus than 360 cycles applied all at once, and that mechanical loading is more osteogenic when divided into discrete loading bouts. Presumably, bone cells become increasingly "deaf" to the mechanical stimulus as loading cycles persist uninterrupted, and by allowing a rest period between loading bouts, the osteogenic effectiveness of subsequent cycles can be increased.