Knee-loading modality drives molecular transport in mouse femur
Knee-loading modality drives molecular transport in mouse femur
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DOI：
10.1007/s10439-006-9171-z
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发表时间：
2006-10-01
影响因子：
3.8
通讯作者：
Yokota, Hiroki
中科院分区：
文献类型：
--
作者：
Su, Min;Jiang, Hui;Yokota, Hiroki
众所周知，机械负荷刺激骨重建。负载驱动的间质液流动和分子转运已被假定在骨形成的增强中发挥作用。为了评估负载驱动的分子运输在一个腔隙性神经网络，我们进行了荧光恢复后光漂白（FRAP）实验，使用陷窝染色的铀（376 Da）。采用新型膝关节加载模式对小鼠股骨进行离体加载，其中远端骨骺以2 Hz的正弦力加载。对位于负重部位近端25%（类似于4 mm）骨干中的骨陷窝进行光漂白和顺序成像，并在有和无膝关节负重的情况下确定荧光恢复的时间常数。使用最佳拟合指数曲线将时间常数估计为恢复63%荧光强度的时间。结果表明，施加的载荷将时间常数从无载荷对照的33 +/- 9 s缩短至膝关节载荷的25 +/- 11 s（p = 0.0014）。测量部位的应变沿股骨中段沿着< 100 mu应变，比骨重建的最小有效应变阈值小一个数量级。总之，目前的研究支持这样一种观点，即施加在骨骺上的载荷增强了皮质骨中的分子转运，而不会在骨干中诱导显著的原位应变。
Mechanical loading is well known to stimulate bone remodeling. Load-driven interstitial fluid flow and molecular transport have been postulated to play a role in the enhancement of bone formation. In order to evaluate load-driven molecular transport in a lacunocanalicular network, we conducted fluorescence recovery after photobleaching (FRAP) experiments using lacunae stained with uranine (376 Da). Loads were applied to a mouse femur ex vivo with a novel knee-loading modality, where the distal epiphysis was loaded with a sinusoidal force at 2 Hz. The lacunae in the diaphysis located 25% (similar to 4 mm) proximal to the loading site were photobleached and sequentially imaged, and a time constant for fluorescence recovery was determined both with and without knee loading. The time constant was estimated as the period to recover 63% of fluorescent intensity using a best-fit exponential curve. The results reveal that the applied loads shortened the time constant from 33 +/- 9 s with non-loading control to 25 +/- 11 s with knee loading (p = 0.0014). The strain in the measurement site was < 100 mu stain along the femoral midshaft, which was an order of magnitude smaller than the minimum effective strain threshold for bone remodeling. Taken together, the current study supports the notion that molecular transport in cortical bone is enhanced by the loads applied to the epiphysis without inducing significant in situ strain in the diaphysis.