Bloomfield S A, Allen M R, Hogan H A, Delp M D
Department of Health and Kinesiology,Texas A&M University, College Station, TX 77843-4243, USA.
Bone. 2002 Jul;31(1):149-57. doi: 10.1016/s8756-3282(02)00785-8.
The purpose of this study was to examine site- and compartment-specific changes in bone induced by hindlimb unloading (HU) in the mature adult male rat (6 months old). Tibiae, femora, and humeri were removed after 14, 21, and 28 days of HU for determination of bone mineral density (BMD) and geometry by peripheral quantitative computed tomography (pQCT), mechanical properties, and bone formation rate (BFR), and compared with baseline (0 day) and aging (28 day) controls. HU resulted in 20%-21% declines in cancellous BMD at the proximal tibia and femoral neck after 28 day HU vs. 0 day controls (CON). Cortical shell BMD at these sites was greater (by 4%-6%) in both 28 day HU and 28 day CON vs. 0 day CON animals, and nearly identical to that gain seen in the weight-bearing humerus. Mechanical properties at the proximal tibia exhibited a nonsignificant decline after HU vs. those of 0 day CON rats. At the femoral neck, a 10% decrement was noted in ultimate load in 28 day HU rats vs. 28 day CON animals. Middiaphyseal tibial bone increased slightly in density and area during HU; no differences in structural and material properties between 28 day HU and 28 day CON rats were noted. BFR at the tibial midshaft was significantly lower (by 90%) after 21 day HU vs. 0 day CON; this decline was maintained throughout 28 day HU. These results suggest there are compartment-specific differences in the mature adult skeletal response to hindlimb unloading, and that the major impact over 28 days of unloading is on cancellous bone sites. Given the sharp decline in BFR for midshaft cortical bone, it appears likely that deficits in BMD, area, or mechanical properties would develop with longer duration unloading.
本研究的目的是检测成熟成年雄性大鼠（6月龄）后肢卸载（HU）诱导的特定部位和骨室的骨骼变化。在HU 14、21和28天后取出胫骨、股骨和肱骨，通过外周定量计算机断层扫描（pQCT）测定骨密度（BMD）和几何形态、力学性能及骨形成率（BFR），并与基线（0天）和衰老（28天）对照组进行比较。与0天对照组（CON）相比，28天HU后，胫骨近端和股骨颈的松质骨BMD下降了20%-21%。与0天CON动物相比，28天HU组和28天CON组这些部位的皮质骨壳BMD更高（高4%-6%），且与负重肱骨中观察到的增加几乎相同。与0天CON大鼠相比，HU后胫骨近端的力学性能出现不显著下降。在股骨颈，28天HU大鼠的极限负荷比28天CON动物降低了10%。HU期间，胫骨骨干中部的骨密度和面积略有增加；28天HU和28天CON大鼠之间的结构和材料性能没有差异。与0天CON相比，21天HU后胫骨骨干中部的BFR显著降低（降低90%）；在整个28天HU期间，这种下降一直持续。这些结果表明，成熟成年骨骼对后肢卸载的反应存在骨室特异性差异，并且卸载28天的主要影响在于松质骨部位。鉴于骨干皮质骨的BFR急剧下降，随着卸载时间延长，BMD、面积或力学性能可能会出现不足。
