Comment les cellules de l'os ressentent-elles une contrainte mécanique?

Bone senses the 3D stress tensor to which it is subjected. Its cells react in the form of by constructing an anisotropic porous mineral/collagen composite structure that seems to be optimised with respect to its stress-carrying capacity. Cortical bone has two systems of interconnected channels. The largest of these is the vascular porosity consisting of Haversian and Volkmann's canals, with a diameter of some 50 microns, which contains a/o blood vessels and nerves, and have a preferential orientation that is clearly affected by the local principal stress directions. The smaller is the system, consisting of the canaliculi and lacunae is oriented perpendicularly to that: the canaliculi are at the submicron level and house the protrusions of the osteocytes. When bone is differentially loaded, fluids within the solid matrix sustain a pressure gradient that drives a flow [Cowin et al., 99]. It is generally assumed that the flow of extra-cellular fluid around osteocytes plays an important role not only in the nutrition of these cells, but also in the bone's mechanosensory system. The interaction between the deformation of the bone matrix and the flow of fluid can be modelled using Biot's theory of poroelasticity [Biot, 41]. As an extension of this theory, the electrochemomechanical theory opens the way to the evaluation of streaming potentials and streaming currents within the lacuno-canalicular porosity. Different options have been proposed as to what guides the osteoblasts and osteoclasts to construct the vascular anisotropic porosity along the principal stress directions. [Smit et al., 02] brought up fluid flow and concomitant prostaglandines and nitric oxide secretion as a potential signalling pathway. Alternatively, [Ferner et al., 86] showed that osteoclasts and osteoblasts can be regulated by electrical fields. In the case of bone remodelling, we suggest that streaming currents and streaming potentials induced by strain induced fluid flow might regulate this specific cellular activity.