Wound healing assay

A wound healing assay is a laboratory technique used to study cell migration and cell–cell interaction. This is also called a scratch assay because it is done by making a scratch on a cell monolayer and capturing images at regular intervals by time lapse microscope. A wound healing assay is a laboratory technique used to study cell migration and cell–cell interaction. This is also called a scratch assay because it is done by making a scratch on a cell monolayer and capturing images at regular intervals by time lapse microscope. It is specifically a 2D cell migration approach to semi-quantitatively measure cell migration of a sheet of cells. This scratch can be made through various approaches, such as mechanical, thermal, or chemical damage. The purpose of this scratch is to produce a cell-free area in hopes of inducing cells to migrate and close the gap.  The scratch test is only ideal for cell types that migrate as a collective epithelial sheets and not useful for non-adherent cells. Specifically, this assay isn't ideal for chemotaxis studies. This laboratory technique has various advantages.  First, these tests are relatively cheap, relatively straightforward and allow for real-time measurements. Additionally, the testing conditions can be easily adjusted to fit different experimental objectives. This approach also allows for a strong directional migratory response making quantifying data simple. To measure the cell migration rate, one can use a standard microscope or there are other more sophisticated live-imaging software such as MetaMorphTM or IncuCyteTM. This software isn’t necessary but it does ensure more accurate results as it captures the same location in each well for each timepoint and is much more convenient than having to do it manually with a standard microscope. One limitation of this assay is that there could be inconsistencies with the depth and size of the scratch.  When the scratch is done manually, it's susceptible to 'ragged' edge boundaries, which make analyzing data more difficult. Also, the damage could physically damage the cells adjacent to the wound and create inaccurate wound size areas. This limitation is slowly becoming less of an issue with automated technologies.  The Electric Cell Impendance Sensing assays utilize to prevent damage to the cells in the underlying extracellular matrix that can likely happen with the manual scratching approaches. Additionally, the WoundmakerTM makes fast and uniform wounds across various numbered well-plates options (96 or 384) and allows for high throughput screening, which is a major advantage for various medical research studies. Despite the new technology that is increasing this assay's accuracy and efficacy, there are still confounding factors that can skew the assay results, such as cell 'crowding', cell/cell adhesion effects and matrix effects. Additionally, there is still mention with the problem of accumulation of cells at the edge of the scratch, making the cell densities uneven. There are some skeptics who think that the scratch created for the assay isn't a very accurate representation of an actual wound. This is very likely true as real wounds are inherently more complex, but this assay does allow for collective cell movements under defined experimental conditions to provide some insight. Despite it being described as straightforward, the technique has been criticized because of inconsistencies in its application from one experiment to another. Outlined is a standard approach to carry-out this assay without the advanced technology: Rate of cell migration: