Université Paris-Est, Laboratoire Modélisation et Simulation Multi Echelle, MSME UMR 8208 CNRS, 61 avenue du Général de Gaulle, 94010 Créteil Cedex, France.
J Theor Biol. 2012 Jun 21;303:75-86. doi: 10.1016/j.jtbi.2012.03.001. Epub 2012 Mar 8.
Bone reacts to local mechanical environment by adapting its structure. Bone is also a key source of calcium for the body homeostasis. Osteocytes, cells located within the bone tissue, are thought to play a major role in sensing mechanical signals and regulating bone remodeling. Interestingly, osteocytes were also shown to directly participate in the calcium homeostasis by regulating dissolution and deposition of calcium in the perilacuno-pericanalicular space. However, it is not known if osteocyte's roles in mechanoregulation and calcium homeostasis have any significant crosstalk. Previously, a multi-scale mathematical model of the interstitial fluid flow through the canaliculus was developed, which took into account physicochemical phenomena including hydraulic effects, formation of electrical double layer, osmosis and electro-osmosis. We extended this model to include the directional movement of calcium from and into the bone tissue, and assessed the shear stress at the osteocyte membrane. We have found that in the bulk of the canalicular space the fluid flow due to chemical gradient generated by deposition or dissolution of calcium is negligible compared to the fluid flow due to hydraulic pressure. However, at the osteocyte proximity, the presence of calcium gradient generated sufficient fluid flow to induce significant changes in the shear stress on the osteocyte membrane. Calcium deposition and dissolution on the canalicular wall resulted in increased or decreased shear stress on the osteocyte membrane respectively. Thus, our data demonstrate that strong calcium fluxes due to whole body calcium homeostasis may affect mechanical forces experienced by osteocytes.
骨骼通过适应其结构来对局部力学环境做出反应。骨骼也是身体钙稳态的关键来源。骨细胞是位于骨组织内的细胞，被认为在感知机械信号和调节骨重塑方面发挥着重要作用。有趣的是，骨细胞还通过调节在骨陷窝-骨小管间空间内钙的溶解和沉积，直接参与钙稳态的调节。然而，目前尚不清楚骨细胞在机械调节和钙稳态中的作用是否存在显著的相互作用。此前，我们开发了一个通过小管的间质液流动的多尺度数学模型，该模型考虑了包括水力效应、双电层形成、渗透和电渗等物理化学现象。我们将该模型扩展到包括钙从骨组织向骨组织内以及从骨组织向外的定向运动，并评估了骨细胞膜上的剪切应力。我们发现，在小管空间的大部分区域，由于钙沉积或溶解产生的化学梯度引起的流体流动与由于液压引起的流体流动相比可以忽略不计。然而，在骨细胞附近，钙梯度的存在产生了足够的流体流动，从而导致骨细胞膜上的剪切应力发生显著变化。小管壁上的钙沉积和溶解分别导致骨细胞膜上的剪切应力增加或减少。因此，我们的数据表明，由于全身钙稳态而产生的强烈钙通量可能会影响骨细胞所经历的机械力。
