Biomedical Engineering Reference
In-Depth Information
FIGURE 4.2: Comparison between a cell section of (A) electron micrograph
and (B) compartmentalized CPM cells. In both cases, it is straightforward to
identify the nucleus, the nucleolus, the plasmamembrane, the Golgi apparatus,
some mitochondria, and some secretory granules.
the cytosolic region, the nucleus, and other intracellular organelles (mitochon-
dria, ribosomes, Golgi apparatus, secretory granules, . . . ) is mandatory to ac-
curately model most of the main intracellular phenomena. For instance, the
introduction of an explicit PM permits one to define the activity of surface
chemical receptors, as well as to better describe the cell adhesive properties,
i.e., to simulate the diffusion of adhesion molecules from the cell cytosol or
their clusterization within particular regions. Moreover, it is possible to re-
produce the active and continuous reorganization of the cytoskeleton, which
provides the mechanical support for cells and mediates their coordinated and
directed movements, in response to mechanical tensions and stresses from the
local environment or to internal biochemical signals. The explicit representa-
tion of the cell nucleus would instead be mandatory to model genetic mech-
anisms, such as DNA duplication, RNA synthesis and diffusion, or transport
of proteins through the nuclear membrane.
The compartmentalized approach is clearly flexible, since it allows the level
of details to be tuned by only increasing or decreasing the number of units
that form the clustered individual, or the number of lattice sites per functional
unit. However, it is obviously computationally expensive, and often such a level
of detail is neither required nor relevant for a good simulation of a number
of biological processes. The optimal strategy depends on the phenomenon of
interest, which therefore requires a preliminary analysis.
In particular, in the applications of the methods proposed in the next
chapters, we will use a simplified representation of cells, which will not be
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