Computational Methods in the Modeling of Scaffolds for Tissue Engineering - Computational Modeling in Tissue Engineering - page 114

Fig. 8 Mechano-regulation model. The tissue phenotype is determined for each element
dependent on its position in the mechano-regulation diagram (not drawn to scale) from Lacroix
et al. [ 37 ])

5 Simulation of Mechano-Biological Concepts

5.1 Cell Differentiation Studied Through Separated Phases

A mechanobiological concept was proposed by Prendergast et al. [ 29 ] to explain
the relation between mechanical stimuli with cell differentiation and tissue for-
mation. This concept was applied on various applications such as implant-bone
interface [ 30 ], fracture healing [ 31 ], osteochondral defect [ 32 ], bone chambers [ 30 ,
31 , 33 ], and bone distraction [ 34 , 35 ]. The first numerical application to tissue
engineering of this concept was performed by Kelly and Prendergast [ 32 ] in which
a mechanoregulation algorithm for tissue differentiation was used to determine the
influence of scaffold material properties on chondrogenesis in a finite element
model of an osteochondral defect.
The basis of the concept is that the stimulus S defined as a combination between
the octahedral shear strain SS and the fluid velocity FF can produce some dis-
tortion of the cell and therefore affects the cell differentiative activity. In the
stimuli equation (Eq. 8 ), a and b are empirical constants; a = 0.0375 and
b = 3 lms -1 .IfS [ 3, then fibrous tissue differentiation occurs; if 3 [ S [ 1,
then cartilage differentiation occurs; if 1 [ S [ 0.267, then immature bone
differentiation occurs; and if 0.267 [ S [ 0.01, then resorption occurs (Fig. 8 ).

S ¼ SS

a þ FF

ð 8 Þ

b

One example to illustrate the use of the mechano-regulation model on scaffold
analysis is the study performed by Sandino and Lacroix [ 36 ] on irregular CaP
scaffold morphology where tissue differentiation was simulated for mechanical
stimuli transmitted under compressive load and perfusion fluid. The properties of