M.Sc Thesis

M.Sc StudentToume Samer
SubjectMechanobiology of cell- substrate interactions during cell
migration and morphological changes
DepartmentDepartment of Biomedical Engineering
Supervisor ASSOCIATE PROF. Daphne Weihs
Full Thesis textFull thesis text - English Version


This work includes three different projects which study the mechanobiology of cell-substrate interactions from different aspects. In the main project we study the effect of tensile strains on the collective cell migration in gap closure process associated with wound healing. The additional two projects are side projects paving the way for future research. These projects are based on traction force microscope for evaluating forces and changes in force application by cells in two different domains: ultrasound effect on force application and forces applied during extravasation of metastatic cancer cells.

In our main work, we observe that radially stretching cell monolayers at a low level (3%) increases the rate at which they close a gap formed by in vitro injury. Wound healing has recently been treated topically by applying deformations at the wound site, e.g. by negative pressure wound therapy. However, the direct effect of deformations on cell migration during gap closure is still unknown. Thus, we have evaluated the effect of radially applied, sustained (static) tensile strain on the kinematics of en mass cell migration. Monolayers of murine fibroblasts were cultured on stretchable linear-elastic substrates that were subjected to different tensile strains, using a custom-designed 3D printed stretching apparatus. We developed this novel apparatus to apply either sustained or dynamic-cyclic tensile strains on cells cultured on elastic, stretchable substrata. Most of the apparatus parts are three-dimensionally printed (excluding motors), and stretching is automatically performed by two direct current geared motors that are controlled by a programmable microcontroller platform. Our apparatus is designed to be low-cost, rapidly manufactured at a university or small-company setting, and simple to use and control, where its flexible, versatile design allows users to experimentally induce different stretching regimes with varying amplitudes and frequencies. Following stretching, the monolayer was “wounded” at its center and the cell migration during gap closure was monitored and quantitatively evaluated. We observe a significant increase in gap-area normalized migration rates and reduction of gap closure time under stretching of 3%, relative to unstretched controls. The effect was reduced under 6% stretch. Interestingly, the initial gap area was linearly correlated with the maximum migration rates, especially under applied stretch. Therefore, small deformations applied to cell monolayers during gap closure enhance en mass cell migration associated with wound healing, and can be used to fine-tune treatment protocols.