Chapter 7 - The growth of biological tissues

Abstract

This chapter discusses how appropriate models and numerical simulations can be used as useful tools to discern the environmental factors affecting the surface kinetics of growing biological tissues, mechanisms of the absorption of nutrients available in the culture medium, a subsequent generation of new cells, and the production of extracellular matrix and their relative importance in determining growth. The attention is focused on fluid-dynamic aspects (in particular on computational fluid dynamics (CFD) moving-boundary methods). The potentialities of the proposed models and methods are illustrated by means of a prototype application designed to reproduce the landmark experiments of Freed et al. 1997 and to draw information about the intrinsic mechanisms of growth. It discusses working engineering CFD models and generalized functional correlations and provides a framework for deeper understanding and effective treatment of relevant phenomena encountered in the new field of tissue engineering. The chapter focuses on the ground conditions because most of the available experimental data for tissue engineering come from on the ground experimentation. To optimize suspension culture, the aforementioned aspects need to be expressed in simple mathematical relationships, quantities, and controlled. It also introduces an analogy with models for organic crystal growth, ignores the fact that, according to biomechanical growth laws proposed in the case of soft tissues, the rate of growth must depend on the stresses. For instance, the fluid shear stresses generated by blood flow in the vasculature can profoundly influence the phenotype of the endothelium by regulating the activity of certain flow-sensitive proteins (enzymes, for example) and by modulating gene expression.