The influence of mechanical stimulus on nutrient transport and cell growth in engineered cartilage: A Finite element approach

Abstract

Osteoarthritis is a degenerative joint disease characterized by cartilage degeneration, which affects more people than any other joint disease. To overcome this problem, tissue engineering has been improving to restore tissue functionality developing new implantable cartilage. Bioreactors can provide an adequate nutrient transport to cells in the scaffold, a good mechanical stimuli and a hydrodynamic environment, which imposes a fluid flow to promote the cell proliferation. Finite element analysis of cartilage growth can be used to guide these tissue engineering experiments in order to produce cell scaffold constructs with specific biomechanical properties. In this work, a 3D finite element model was developed to simulate the diffusion and transport of nutrients and the cell growth kinetics in a porous scaffold when it is subject to different mechanical stimuli. The mass transport was defined by convection-diffusion equation, where the nutrient uptake was represented through the Michaelis-Menten kinetics and the fluid dynamics within the construct was modelled by Brinkman’s equation. Cell growth kinetics was modelled by the Contois equation, which includes the effect of glucose concentration and the cell density saturation. The objective of this study was to understand the effect of mechanical loading in nutrition and cell growth during culture. Different mechanical stimuli (5%, 10% and 15% of compressive strain with frequencies of 0.5Hz, 1Hz and 2Hz) were performed during a period of 48 hours of cell culture. The spatial-temporal evolution of the local glucose, oxygen and lactate concentrations, the pH level and the cell density within the scaffold was analysed. The numerical simulations of so- lutes concentrations and cell growth show a good agreement with experimental results. These results show that fluid shear stress promoted by fluid dynamics inside the scaffold is influenced by compression and consequently the solute transport and the chondrocyte activity is affected for altered levels of stimulation.