An invasion assay is a laboratory technique used to study how cells move through a barrier or matrix, mimicking their movement within the body. This tool helps researchers understand the mechanisms that drive cell movement.
Understanding Cell Invasion
Cell invasion is a complex biological process involving the movement of cells through tissues and organs, often causing changes in normal tissue structure and function. This ability is naturally present in various physiological processes. For instance, during wound healing, fibroblasts and keratinocytes migrate to repair damaged tissue, and immune cells, such as leukocytes, invade infected areas to fight off pathogens.
While beneficial in normal bodily functions, cell invasion can become problematic when dysregulated. A prominent example is cancer metastasis, where cancer cells detach from a primary tumor and invade surrounding healthy tissues. These malignant cells degrade the extracellular matrix and then migrate through it to spread to distant organs. This uncontrolled invasion is a major factor in the progression of many diseases, including cancer and inflammatory disorders.
How Invasion Assays Are Performed
Invasion assays are performed using laboratory setups to simulate the body’s environment. One common method is the Transwell, or Boyden chamber, assay, which uses a two-chamber system separated by a porous membrane. In this setup, cells are placed in the upper chamber, and a chemoattractant, a substance that draws cells, is placed in the lower chamber.
To specifically measure invasion rather than just migration, the porous membrane in the Transwell system is coated with an extracellular matrix material, such as Matrigel. Matrigel acts as a reconstituted basement membrane, a dense layer that cells must degrade to pass through. Invasive cells secrete enzymes that break down this Matrigel, allowing them to move through the pores of the membrane into the lower chamber. After an incubation period, the cells that have successfully invaded the lower chamber are stained and counted.
Another method, the scratch assay, involves creating a “wound” or gap in a monolayer of cells grown in a dish. Cells then migrate to close this gap over time. While primarily a migration assay, it can be adapted to observe aspects of invasive behavior, particularly how cells move into an empty space. The progression of cells into the scratched area is monitored and quantified over time.
Key Applications in Medical Research
Invasion assays are widely used in medical research, particularly in understanding disease progression. A primary application is in cancer research, where these assays help scientists study metastasis, the process by which cancer cells spread throughout the body. By evaluating the invasive potential of different cancer cell lines, researchers can identify characteristics that contribute to aggressive tumor behavior. These assays also aid in testing the effectiveness of potential anti-cancer drugs designed to inhibit cell invasion, offering insights into new therapeutic strategies.
Beyond cancer, invasion assays contribute to immunology by studying the migration of immune cells. Understanding how immune cells move through tissues is relevant for researching inflammatory responses and autoimmune diseases. Similarly, in infectious disease research, these assays can be used to investigate how pathogens invade host cells, which is a fundamental step in many infections. The insights gained from these studies help in developing treatments that target these invasive mechanisms.
Interpreting and Utilizing Assay Results
Results from invasion assays are quantified by counting the number of cells that have successfully moved through the barrier. A higher number of invaded cells indicates greater invasive capacity, while a lower count suggests reduced invasiveness. For instance, in cancer research, a high invasion rate for a particular cell line might suggest a more aggressive tumor phenotype. Conversely, if a new drug treatment leads to a significant reduction in invaded cells, it suggests the compound has anti-invasive properties.
These findings directly contribute to drug discovery and the understanding of disease progression. By comparing the invasive potential of treated versus untreated cells, researchers can identify compounds that effectively block or reduce cell invasion. This information is then used to develop new therapies that target the spread of diseases like cancer. The data also helps to uncover the molecular mechanisms driving cell invasion, providing a deeper understanding of how diseases develop and advance.