The influence of scaffold deformation and fluid mechanical stimuli on bone tissue differentiation.

Bone tissue engineering enables the self-healing of bone fractures avoiding the graft surgery risks. Scaffolds are designed to transfer global mechanical load to cells, and the structure-blood flow interaction is crucial for cell differentiation, proliferation, and migration. Numerical models often consider the effect of solid on the fluid or vice-versa, nevertheless, fluid-structure interactions (FSI) are not usually explored. The present study aims to develop in-silico FSI models to evaluate tissue differentiation capability of different scaffold designs. This is accomplished by analyzing the relation between scaffold strain deformation and fluid mechanical stimuli developed at the cell microscopic level. Cubic regular structures with cylinder and sphere pore based of 60%, 70% and 80% porosity were modelled in finite element analysis. Static or dynamic compression and inlet steady state or transient state fluid profile were considered. Fluid-structure interactions have been performed, and cell differentiation studies considering the octahedral shear strain and fluid shear stress have been compared. Results indicate that high porous scaffold with low compression and fluid perfusion rates promote bone tissue proliferation. Moreover, mechanical stimulation seems to help bone formation and to inhibit cartilage phenotype. Results showed that neglecting the interaction between the scaffold and fluid flow could lead to substantial overestimation of bone differentiation. This study enhances our understanding of the role of dynamic mechanical simulations in tissue formation; allowing the improvement of scaffold design to face complex bone fractures.