Biomedical Engineering Reference
In-Depth Information
because they address only migration on fl at surfaces and rely on individual
cell tracking. They are primarily used in chemotaxis studies.
Under-agarose assay
The under-agarose migration assay is similar to the Dunn and Zigmond
chambers and is also frequently used in chemotaxis assays (Heit and Kubes,
2003; Rothman and Lauffenburger, 1983; Woznica and Knecht, 2006). The
primary difference is that in this confi guration the cells are migrating on a
rigid substrate but under a fl exible gel that contains the chemoattractant
gradient. The agarose gels are cast in molds with glass bottoms and two
wells are formed into the gel, one for the cells and one for the chemoat-
tractant. The chemoattractant diffuses through the gel, and the cells migrate
under the agarose from their starting well toward the chemoattractant
source. However, the gel matrix maintains the gradient for extended times,
and multiple gradients may be generated simultaneously.
3.5.2
In
/
ex vivo
methods
Several assays have been developed in attempts to mimic and characterize
cell migration
in vivo
. These assays are primarily 3D in nature and have pro-
vided valuable insights into processes including development, angiogenesis
and regeneration.
Transparent model organisms
There are numerous challenges to studying cell migration
in vivo
. The use
of model organisms has become a signifi cant tool in analyses of genetic and
molecular control in cell migration. Specifi cally, the embryos of zebrafi sh
(Ablooglu
et al.
, 2010; Kozlowski
et al.
, 1997; Lopez-Schier, 2010; Stoletov
et al.
, 2010), the nematode worm,
Caenorhabditis elegans
(
C. elegans
)
(Kubota
et al.
, 2008; Lee and Cram, 2009; Lehmann, 2001), and the fruit fl y,
Drosophila melanogaster (Lehmann, 2001; Lopez-Schier, 2010; McMahon
et al.
, 2010), are providing important insights into
in vivo
cell motility. The
analysis of cell migration in these model organisms is facilitated by the fact
that they are transparent and the cell sorting and development of their
organs can be visualized with standard light microscopy. Antibody-labeled
or GFP-expressing cells can easily be tracked as they travel to compart-
ments via genetically programmed tracks. Approaches using these model
organisms combine expression strategies with novel assays and screening
methods to identify genes that regulate cell migration. This is commonly
quantifi ed by the differences in the tracks or fi nal positions of labeled cells
in mutants versus the wild-type strain. The comprehensive use of these
