Migration Assays for Oligodendrocyte Precursor Cells - Methods in Molecular Biology: Extracellular Matrix Protocols - page 254

1.1. Advantages and Disadvantages of the Migration Assays
1.1.1. Chemotaxis Chamber
The advantages of the microchemotaxis assay are that it allows for the
simultaneous assay of 48 wells per chamber, allowing either several different
chemotactic agent concentrations to be assayed in a single experiment, or
chemotactic and haptotactic stimuli to be assayed together. It is a quick assay,
with significant migration often being seen within 8 h (or less) allowing large
numbers of experiments to be conducted in a relatively short period of time.
An added bonus is the small volume required for each well, reducing the cost
of experiments involving blocking antibodies and growth factors. Although
counting the migrated cells is labor-intensive, it is a precise and objective pro-
cess with low-error rates of less than 10% between operators. The major disad-
vantage of this assay is that it requires large numbers of cells to be prepared
(1.5-2.0

10 6 cells per chamber), which may present problems when primary
cells are being studied.

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1.1.2. Agarose Drop Assay
The advantages of the agarose drop assay are that it allows migratory behav-
ior of the same starting population of cells to be examined under many differ-
ent conditions, e.g., with different extracellular matrix (ECM) substrates and
inhibitors. It also enables the extent of cell migration to be examined at more
time-points, e.g., a single experiment with removal of the plate from the incu-
bator and cell migration measured from each drop before the plate is returned
to incubator. This assay permits interventions to be made with the introduction
and subsequent removal of inhibitors or blocking antibodies after the start of
the assay, thus examining the reversible nature of blocking agents during the
course of one experiment. Information about the morphology of migrating cells
on different substrates and under different conditions, can also be determined
using this assay. The disadvantages of this assay are that it takes several days,
during which time cells may synthesize and secrete their own ECM in addition
to the ECM molecule under investigation. Promigratory agents, which are also
mitogenic such as growth factors, will result in an increase in cell numbers,
which may be misinterpreted as cells actively migrating out of the drop. Finally,
the assay is conducted in larger volumes, i.e., a 24-well plate, and therefore
also requires larger volumes of growth factors and or blocking antibodies.

2. Materials
2.1. The Chemotaxis Chamber
1. Nucleo Pore™ 48-well chemotaxis chambers (Corning Costar, Cambridge, MA,

Cat. No. AP48) ( see Note 1 ).