Finite element modeling of cells in response to loading [electronic resource] : effect of cytoskeleton /

by Loke, Chee Wui.

Finite Element Modeling of Cells in Response to Loading - Effect of Cytoskeleton Chee Wui Loke Osteoarthritis is a type of arthritis marked by degeneration of the cartilage and bone in joints, which causes severe joint pain associated with daily activities. Articular cartilage is one of the major load bearing tissue that transfers load across joints and with synovial fluid provides a bearing surface for the diarthrodial joints. It is made up of highly specialized cells called chondrocytes that are responsible for its growth and maintenance. Mechanical loading and cell-matrix interactions have been shown experimentally to influence the biological behavior of chondrocytes. Biological behavior of the chondrocytes is important because they are highly associative with the collagen secretion, which is one of the building blocks of Extra Cellular Matrix. While there are many numerical models which had tried to mimic the behavior of the live cell, they do not represent the actual live cell architectures. Therefore a 3-D finite element model was built based on major structural components of a live cell, which consisted of cytoskeleton elements (actins and microtubules networks), cell membrane and internal fluid pressure in the analysis. As a result, the behavior of this cell model has shown good agreement with the live cell under compressive loading. Since the relationship between physical parameters, properties and overall cell structural stability are poorly understood, a series of parametric studies were performed by changing the agarose gel stiffness in the cell-gel construct model, increasing layers of interconnected actins filaments, changing actins stiffness and pre-stress effects of actins. A 2-D finite element model was also constructed, based on the real structure elements and composition of a live cell that are comprised of different structural combinations (microtubules and actins) at different locations within the cell. Using the volume fraction approach and treating each structural combination as a composite element, we concluded that there are four categories of composite elements in the cell and they are orthotropic. Using similar compressive strain of 15% and 30% in both the finite element and the experimental cell-gel construct model, the radial deformation, Ur, or shape change, are found to be within a good agreement. Replying on good predictions from ABAQUS, we are able to change the mechanical properties of each element accordingly to the structural combinations from the live cell and obtained the equivalent shape change, without performing experiments. This thesis is dedicated to Nelson Loke and Emily Cheong iii