The Transwell system is a widely used laboratory tool for culturing cells, particularly for studies mimicking conditions found within living organisms. This system creates a controlled environment where cells can interact and behave more naturally than in traditional flat culture dishes. It allows researchers to study cellular processes in a setting that more closely resembles the complex biological conditions of tissues and organs.
Components and Design
A Transwell system consists of a multi-well plate and a permeable membrane insert, often called the “Transwell.” The insert fits into the wells, creating two distinct compartments: an upper (apical) chamber and a lower (basolateral) chamber. The permeable membrane separates these compartments, allowing for the exchange of nutrients and soluble factors.
The membrane’s characteristics are important for specific experiments. Its pore size can range from 0.4 to 8.0 micrometers or more, influencing what can pass through. The material of the membrane also varies, with common options including polycarbonate, polyester (PET), and collagen-coated polytetrafluoroethylene (PTFE). These materials are often treated with extracellular matrix coatings like collagen or fibronectin to enhance cell attachment and growth, mimicking natural tissue environments.
Simulating Biological Environments
The Transwell system creates two interconnected yet separate environments for cell cultures. Cells can be grown on either side of the permeable membrane, allowing researchers to study interactions between different cell populations or observe how cells behave across a barrier. This setup is particularly useful for investigating how cells move, communicate, and transport substances in a controlled manner.
The system helps researchers model various in vivo conditions, such as epithelial or endothelial layers found in the body. For example, cells forming a barrier, like those lining the gut or blood vessels, can be grown on the membrane. This allows for studies of processes like nutrient absorption, where substances pass from one side of the cell layer to the other, or drug delivery, examining how compounds cross biological barriers. The design enables the creation of chemical gradients, guiding cell migration and providing a more lifelike chemical signaling environment.
Diverse Research Applications
Transwell systems are widely utilized across various fields of biological research, offering insights into cellular behavior. They are extensively used in cell migration and invasion studies, which are particularly relevant for understanding cancer metastasis and wound healing. In these assays, cells are placed in the upper chamber, and a chemoattractant is added to the lower chamber, prompting cells to migrate through the membrane’s pores towards the attractant.
For invasion studies, an additional layer of extracellular matrix, like Matrigel, is applied to the membrane, requiring cells to degrade this barrier before migrating through the pores, mimicking the invasive nature of tumor cells. The system also facilitates co-culture experiments, where different cell types can be grown in separate compartments but interact through secreted factors that pass through the membrane pores. This setup is valuable for studying organ-organ communication or immune responses, where various cell types influence each other without direct physical contact.
Transwell systems are also employed for transport and permeability studies, assessing how molecules, such as drugs or nutrients, pass across a cell layer grown on the membrane. This is relevant for drug absorption research in the gut or investigations into the permeability of the blood-brain barrier, providing insights into how substances are transported within the body.