Multiscale Approach to Understand the Multiphysics Phenomena in Bone Adaptation - Multiscale Computer Modeling in Biomechanics and Biomedical Engineering - page 38

deposit is made from the cement line to the central zone of the future secondary
osteon until the Haversian canal is formed.
2.3.5 Mineralization
Bone crystals composed of hydroxyapatite are transported within the collagen
matrix. The mineralization phenomenon starts after 13 days at an initial rate of
1 lm/day.
2.3.6 Quiescence
When the secondary osteon is achieved, osteoblasts gradually flatten and become
quiescent lining cells covering the Haversian surface. Some of the osteoblasts are
simply destroyed or differentiate into osteocytes when embedded in the bone
matrix.
The last three stages last longer than the first three ones. However, many
questions remain on hold concerning this remodelling process. What is the
physical signal pathway? If the effector cells are the lining cells that are activated
to initiate the remodelling process, what is the nature of the signal felt by the
mechano-sensitive cells?
2.4 Candidates for the Mechano-Sensitive Role
There are experimental evidences that most of the bone cells can sense a
mechanical solicitation (membrane deformation, fluid shear effects, etc.) and
consequently change their metabolic activity [ 31 ]. Anyway, two main scenarios,
that may occur in parallel, have been proposed to explain the mechanically
induced bone formation or resorption [ 30 ].
2.4.1 The Bone Surface Cells
On the one hand, the cells located at the bone surface (osteoblasts, lining cells and
osteoclasts) may simultaneously be mechano-sensors and senso-actors. Thus, these
cells would be able to sense the strain of their pericellular matrix in their imme-
diate environment.