טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentGoldstein Diana
SubjectThe Distribution of Active Forces in Living Cells in vitro
DepartmentDepartment of Biomedical Engineering
Supervisor Professor Daphne Weihs
Full Thesis textFull thesis text - English Version


Abstract

Cell function and specifically processes related to cancer rely heavily on cell mechanics. Understanding the unique mechanical properties of living metastatic cancer cells, can lead to major developments in treatment and prevention. The cell interior is constructed of different compartments with a specific role and tasks for each of them, constantly being regulated and remodeled. This highly regulated dynamics is a necessity in different fundamental functions such as maintains of cell shape and morphology, cell division, cell motility and more. Mechanics of living cells can be measured dynamically using time-resolved particle tracking. Cell activity together with thermal fluctuation generates observed particle dynamics and can also reveal differences between cell types.  Activity in the cell typically results from the dynamics of polymerization/depolymerization of the cytoskeleton and molecular motor motion. Measured cell mechanics are thus directly linked to the fluctuation of active forces generated by the molecular motors and the cytoskeleton.

In this study, we have evaluated the origin of active forces in two human epithelial breast cancer cell lines, with low and high-metastatic potentials. To distinguish between relative contributions of the mechanical elements in the cell we have targeted each element in the cell separately and monitored cell response and compensation. Specifically, we have evaluated changes in mechanics, viability, and cytoskeletal structure. Statistical motion analysis in the form of mean square displacement has been initially employed to evaluate and study the driving mechanism of active transport in the cells. In living cells, the MSD is a good first estimator of mode-of-motion and micromechanics, however it does not provide enough information to fully characterize this complex intracellular microenvironment or reveal underlying transport mechanisms. Therefore, additional analysis approaches have been employed in the evaluation of probe particles motion, such as trajectory’s radius of gyration and other orders of displacement. Our founding indicates that the cells with the higher metastatic potential are softer, exhibit enhanced intracellular dynamics and particle transport is mostly driven by MTs dynamics, while the driving mechanism for active particle transport in cells with low metastatic potential are the molecular motors directly. Our work provides a basis for improved understanding of intracellular particle tracking results in general. Moreover, we are able to distinguish dominant mechanisms that drive particle transport as well as revealing different mechanics between the two cell types, which could relate to their metastatic capabilities.