2.4. Cell Migration Assay
An in vitro scratch wound healing model was used to assess cell migration. HaCaT cells were plated in a 12-well plate and grown to complete fusion. Next, they were scraped in a straight line with a 100-μL pipette tip to create a uniform cell-free zone and rinsed three times with PBS. Then the cells were treated with normal medium or medium containing EGF or RHC/EGF. The images of the cells at the beginning and at regular intervals during cell migration to close the scratch were captured and compared through quantifying the migration rate of the cells.