Ph.D Thesis

Ph.D StudentTzezana Roey
SubjectBio-Mimetic Interactive Scaffolds for Tissue Engineering
DepartmentDepartment of Nanoscience and Nanotechnology
Supervisors PROF. Eyal Zussman
PROF. Shulamit Levenberg


In this research we developed a novel process that utilizes methods common in tissue engineering to supply revelations about developmental biology of embryos and the differentiation process of stem cells. We aim at understanding the process of embryonic development as guided by concentration gradients of growth factors and emulating it in the lab. To that purpose, we constructed novel scaffolds that housed human embryonic stem cells and murine embryonic carcinoma cells, using a technique termed hydrospinning. The scaffolds released all-trans-retinoic acid, a potent growth factor, from different areas. Convection was operated on the scaffold to ensure that a gradient of the growth factor is maintained for at least a few initial hours. The distribution of retinoic acid throughout the scaffold, in time and in space, was described by a physical model.

The resulting gradient brought about an altered differentiation pattern of the cells located at different points along its path. There was a significant increase in the concentration of neural markers such as TAU and β3-tubulin in locations that experienced high concentrations of all-trans-retinoic-acid, as expected. The concentration of another neural lineage marker, N-Cadherin, was decreased in the same locations, signifying the existence of a different regulatory path for N-Cadherin in the cells.

These results strengthen the hypothesis according which embryonic development is largely dependent on spatially and temporally distributed concentration gradients. By applying the methods and the physical model described herein, developmental biologists can now test their theories in a quantifiable, in-vitro manner.

The results obtained from our experiments also supply new information regarding the differentiation patterns of embryonic carcinoma cells when affected by all-trans-retinoic acid, and monitor the activation of at least three different proteins prevalent in different phases of the differentiation process.