A migration assay Transwell, also known as a Boyden chamber assay, is a laboratory tool designed to study how cells move. It provides a controlled environment to observe cell migration, the directed movement of cells from one location to another. This foundational technique quantifies cellular movement in response to various stimuli.
The Significance of Cell Migration
Studying cell migration is significant in biology and medicine because it underpins numerous processes in the body. For instance, during embryonic development, cells precisely move to form tissues and organs, establishing the body’s structure. In adults, cell migration is involved in normal physiological functions such as wound healing, where cells move to repair damaged tissue, and immune responses, where immune cells travel to sites of infection or inflammation to combat pathogens.
Conversely, uncontrolled cell migration contributes to the progression of many diseases. Cancer metastasis, for example, relies on the ability of cancer cells to detach from a primary tumor, move through the body, and establish new tumors in distant organs. Inflammatory diseases also involve the misguided migration of immune cells to healthy tissues, leading to damage and dysfunction. Therefore, understanding the factors that control cell movement is important for developing new treatments for these conditions.
How the Transwell Assay Operates
The Transwell assay system consists of a multi-well plate and a permeable Transwell insert. This insert has two chambers: an upper chamber where cells are initially placed, and a lower chamber that collects migrated cells. A porous membrane with specific pore sizes separates these chambers, selected based on the cell type being studied.
To perform the assay, cells are prepared, often by serum-starvation, to minimize random movement. A chemoattractant (a substance that attracts cells) is then added to the lower chamber, creating a chemical gradient that encourages cells to move towards it. Cells are then seeded into the upper chamber of the Transwell insert. The entire setup is incubated, allowing cells to migrate through the pores of the membrane towards the chemoattractant.
After incubation, non-migrated cells are removed from the upper surface of the membrane. Migrated cells, on its underside or in the lower chamber, are then fixed and stained. Common stains like crystal violet or DAPI color the cells for quantification. For adherent cells, images of the stained cells on the membrane’s underside are taken and counted. For non-adherent cells, the cells in the lower chamber are collected and counted.
Diverse Applications in Biomedical Research
The Transwell assay has broad applications in biomedical research. In cancer research, it studies cancer cell migration and invasion, which are hallmarks of metastasis (the spread of cancer throughout the body). It helps evaluate the invasive capacity of cancer cells and screen for potential anti-metastatic drugs.
It is also applied in immunology to investigate immune cell trafficking. For instance, it helps understand how immune cells, like T cells, respond to chemokines (chemical signals that guide their movement to sites of inflammation or infection). Researchers assess immune cell migration towards specific stimuli, shedding light on immune responses and inflammatory conditions.
The Transwell assay also contributes to wound healing studies by assessing cell migration and tissue repair. It allows observation of how cells, such as fibroblasts or epithelial cells, move to close a wound or regenerate damaged tissue. The assay also aids drug screening, evaluating how compounds affect cell migration, potentially leading to new therapeutic agents for diseases with dysregulated cell movement.