New trends in tissue engineered cartilage: microfluid dynamics in 3-D engineered cell systems

Bioreactors allowing culture medium direct-perfusion overcome diffusion limitations associated with static culturing and provide flow-mediated mechanical stimuli. The hydrodynamic stress imposed on chondrocytes will depend not only on the culture medium flow rate, but also on the scaffold three-dimensional (3D) micro-architecture. We performed computational fluid-dynamic (CFD) simulations of the flow of culture medium through a 3D porous scaffold, with the aim of predicting the shear stress acting on the cells as a function of parameters that can be set in a tissue-engineering experiment, such as the medium flow rate and the diameter of the perfused scaffold section. We developed two CFD models: the first model (Model 1) was built from micro-computed tomography reconstruction of the actual scaffold geometry, while the second model (Model 2) was based on a simplification of the actual scaffold microstructure. The two models showed comparable results in terms of the distribution of the shear stresses acting on the inner surfaces of the scaffold walls. Models 1 and 2 gave a median shear stress of 3 mPa at a flow rate of 0.5 cm(3) min(-1) through a 15 mm diameter scaffold. Our results provide a basis for the completion of more exhaustive quantitative studies to further assess the relationship between perfusion at known micro-fluid dynamic conditions and tissue growth in vitro.