Cell adhesion is the process by which cells attach to each other or to a substrate, such as a culture surface. Cell adhesion is essential for many biological functions, such as tissue formation, wound healing, immune response, and cancer metastasis. In mammalian cell culture, cell adhesion can affect the growth, differentiation, and survival of the cells. Therefore, understanding and controlling the factors that influence cell adhesion is important for optimizing cell culture conditions and applications.
In this blog post, I will discuss some of the main factors that affect cell adhesion in mammalian cell culture, and provide some tips on how to improve cell attachment and performance.
Factors that affect cell adhesion in mammalian cell culture
There are many factors that can affect cell adhesion in mammalian cell culture, but they can be broadly classified into two categories: biological factors and physical factors.
Biological factors
Biological factors include the type and quality of the cells, the composition and concentration of the media and supplements, and the presence or absence of extracellular matrix (ECM) proteins.
- Cell type and quality: Different types of cells have different adhesion properties and preferences. For example, epithelial cells tend to adhere strongly to each other and to substrates, while mesenchymal cells are more motile and less adhesive. Moreover, the quality of the cells can affect their adhesion behavior. Cells that are healthy, viable, and in an appropriate growth phase will attach better than cells that are stressed, damaged, or senescent.
- Media and supplements: The media and supplements provide the nutrients, hormones, growth factors, and other molecules that support cell growth and function. However, they can also affect cell adhesion by modulating the interactions between cells and substrates. For example, serum is a common supplement that contains many ECM proteins, such as fibronectin, collagen, and laminin, that can enhance cell attachment. However, serum can also introduce variability and contamination to the culture system. Therefore, some researchers prefer to use serum-free media or defined supplements that provide more control over the culture conditions.
- Extracellular matrix proteins: ECM proteins are a complex network of molecules that provide structural and biochemical support to cells in vivo. They also mediate cell adhesion by binding to specific receptors on the cell surface, such as integrins. In vitro, ECM proteins can be used to coat culture surfaces or added to media to improve cell attachment and function. Some common ECM proteins used in cell culture are collagen, fibronectin, laminin, vitronectin, gelatin, and Matrigel.
Physical factors
Physical factors include the type and quality of the culture surface or substrate, the temperature and gas mixture of the incubator, and the mechanical forces applied to the cells.
- Culture surface or substrate: The culture surface or substrate is the material that supports the cells in vitro. It can be made of plastic, glass, metal, or other materials. The properties of the culture surface or substrate can affect cell adhesion by influencing the availability and orientation of ECM proteins, the charge and hydrophobicity of the surface, and the roughness and porosity of the surface. For example, tissue culture-treated plastic is a common surface that is modified to increase its hydrophilicity and protein-binding capacity. However, some cells may require more specialized surfaces that mimic their natural environment better. For example,
- 3D scaffolds or hydrogels can provide more structural support and mimic tissue architecture better than 2D surfaces.
- Nanofibers or microcarriers can increase the surface area and enhance cell attachment and proliferation.
- Bioactive surfaces can provide specific signals or stimuli to modulate cell behavior.
- Incubator temperature and gas mixture: The incubator provides a controlled environment for cell culture by maintaining a constant temperature and gas mixture. The optimal temperature for most mammalian cells is 37°C (98.6°F), but some cells may require lower or higher temperatures depending on their origin. The optimal gas mixture for most mammalian cells is 5% CO2 (carbon dioxide) in air (95% O2), but some cells may require lower or higher CO2 levels depending on their metabolism. Deviations from these optimal conditions can cause stress to the cells and affect their adhesion behavior.
- Mechanical forces: Mechanical forces are physical stimuli that are applied to the cells by external sources or generated by the cells themselves. They can include shear stress (caused by fluid flow), compression (caused by weight or pressure), tension (caused by stretching or pulling), or vibration (caused by shaking or oscillation). Mechanical forces can affect cell adhesion by altering the shape and cytoskeleton of the cells, the expression and activation of adhesion molecules on the cell surface, and the remodeling and deposition of ECM proteins around the cells.
Tips for improving cell adhesion in mammalian cell culture
Based on these factors that affect cell adhesion in mammalian cell culture, here are some tips for improving cell attachment and performance:
- Choose the appropriate cell type and quality: Select the cell type that suits your research goals and applications. Use fresh and healthy cells that are in an exponential growth phase. Avoid using cells that are overgrown, contaminated, or senescent.
- Optimize the media and supplements: Choose the media and supplements that provide the optimal nutrients, hormones, growth factors, and other molecules for your cell type. Use serum-free media or defined supplements if possible to reduce variability and contamination. Add ECM proteins or other attachment factors to the media or coat the culture surface with them if needed to enhance cell attachment.
- Select the suitable culture surface or substrate: Choose the culture surface or substrate that matches the adhesion preferences and requirements of your cell type. Use tissue culture-treated plastic or other modified surfaces if your cells are adherent and do not require special signals or stimuli. Use 3D scaffolds, hydrogels, nanofibers, microcarriers, or bioactive surfaces if your cells are poorly adherent or require more complex or specific environments.
- Maintain the optimal incubator temperature and gas mixture: Keep the incubator temperature and gas mixture constant and within the optimal range for your cell type. Monitor the temperature and CO2 levels regularly and adjust them if needed. Avoid opening the incubator door frequently or for long periods of time to prevent fluctuations in temperature and gas mixture.
- Apply mechanical forces carefully: Apply mechanical forces to your cells only if they are relevant to your research goals and applications. Choose the appropriate type, magnitude, frequency, and duration of mechanical forces for your cell type. Monitor the effects of mechanical forces on your cells regularly and adjust them if needed. Avoid applying excessive or inappropriate mechanical forces to your cells that may cause damage or detachment.
Conclusion
Cell adhesion is a complex and dynamic process that is influenced by many biological and physical factors in mammalian cell culture. By understanding and controlling these factors, you can improve cell attachment and performance in vitro. I hope this blog post has provided you with some useful information and tips on how to optimize cell adhesion in mammalian cell culture.
