Optimized Scratch Assay for In Vitro Testing of Cell Migration with an Automated Optical Camera

The main advantage of this technique is that you can look at the cells real time in the automatic optical microscope. The implications of this treatment extends to a therapy of chronic wounds or cancer where migration plays a crucial role in these diseases. Begin by washing a confluent culture of HaCaT cells two times with five milliliters of sterile magnesium and calcium free PBS per wash.

Next, incubate the cells with one milliliter of trypsin in a 37 degree Celsius incubator for five to eight minutes. After confirming detachment under a light microscope stop the enzymatic reaction with nine milliliters of culture medium supplemented with FBS. And dilute the cells to a 7.5 times 10 to the fourth cells per 250 microliters of medium plus FBS concentration.

Next, seed 250 microliters of cells to each well of a round-bottomed 48-well tissue culture plate, and gently slide the plate from side to side to ensure the cells are equally distributed across the well bottoms. Then transfer the plate to a cell culture incubator. When the cultures have reached a 90 to 95%confluency, replace the supernatant in each well with 250 microliters of freshly prepared medium supplemented with 10 micrograms per milliliter of mitomycin C, and return the plate to the incubator for another two hours.

At the end of the incubation wash the cells with 250 microliters of PBS and add 250 microliters of fresh PBS to each well. Then use a 200 microliter micropipette tip to make one vertical scratch in each cell monolayer. When all of the monolayers have been scratched replace the PBS in each well with 250 microliters with the peptide stimulus of interest and mount the plate into an optical camera system with the lid intact.

To set up the optical camera open the acquire window and select wound healing. Select the plate type and unselect the wells not in use. Next click enable and right click on one of the wells to adjust the focus to fit the position of the cells.

Set the time period for the images under picture interval and set the number of repetitions to fit the desired period. Then select the appropriate analysis type. Then click start to begin imaging the cells.

When a wound occurs the skin cells begin to proliferate and to migrate across the wound bed to close the wound, a process that can be observed through the optical camera. After a 48-hour incubation endothelial growth factor treatment induces a nearly 95%closure of the wound, compared to a 38%closure in the untreated control wells, and 33 and 62%closures in the lactoferrin and lactoferricin cultures respectively. The percentage of wound closure determined from changes in gap width from the initial scratch can also be plotted for each growth stimulus.

This video describes a straightforward and efficient protocol for studying migration of keratinocytes across a scratch made in a monolayer of healthy cells. Though the cells used in this assay is HaCaT cells, the method can also be applied on other cell lines, fungi, or even bacteria, as long as they are adherent to the bottom of the microtiter plate.