3D tissue formation: the kinetics of human mesenchymal stem cells

The main thesis in this book proposes that physical phenomena underlies the formation of three-dimensional (3D) tissue. In this thesis, tissue regeneration with mesenchymal stem cells was studied through the law of conservation of mass. MSCs proliferation and 3D tissue formation were explored from 2D to 3D conditions. The kinetics of proliferation was the unifying principle to compare and analyze the behavior of human MSCs (hMSCs) through the quantification of the movement or conversion of mass during proliferation. This thesis focuses on the kinetics of proliferation of hMSCs under two physical phenomena (Diffusive mass transport and shear stress). hMSCs were shown to have different kinetics when cultured at different seeding densities (Chapter 1). On the other hand, a kinetic pattern was maintained under both diffusive mass transport and shear stress (Chapter 2). The importance of these two chapters lies in identifying the metabolic processes during hMSCs proliferation that are in/dependent of physical parameters. The shear stress characterization of 3D scaffolds provided Darcian permeability constants to include in the design and analysis of 3D scaffolds. Based on the findings of chapters 1- 3, the main purpose of chapter 4 was to explore 3D tissue formation with hMSCs under diffusive mass transport (static) and shear stress (bioreactor). These results showed that 3D tissue formation correlates with concentration gradients that were estimated through computational fluid dynamics. The kinetics of proliferation of hMSCs under both 2D and 3D showed that hMSCs proliferate slower in 3D than in 2D, but achieve a higher degree of organization in 3D. The practical application of 3D tissue formation by hMSCs was further explored in chapter 5 towards the development of an in vivo high throughput screening (HTS) system. This HTS system offers the possibility to screen multiple conditions in animal models, thereby significantly decreasing the costs and lives sacrificed in animal experiments.