Factors Affecting TEER Measurement in Cell Culture Studies
Transepithelial/Transendothelial Electrical Resistance (TEER) is a widely used quantitative technique to assess the integrity of tight junctions in cell monolayers. TEER is particularly valuable in studies involving drug transport, toxicology, inflammation, and organ-on-chip systems. TEER measurement provides fast and quantitative data and can be used as an efficient and cost-effective method for drug discovery and development. There are certain biological and technical factors that are known to affect TEER readings. This article reviews the key variables that influence TEER outcomes in cell culture studies and how to ensure consistent TEER measurement analysis can be done by minimizing or eliminate the effects of these factors.
Cell Type and Confluency
TEER values are highly dependent on the specific cell/tissue type used. For instance, Caco-2 cells, commonly used to model intestinal barriers, exhibit high resistance when fully differentiated, whereas endothelial cells typically show lower baseline resistance. Ensuring full confluency is essential. Incomplete monolayers introduce gaps that significantly reduce TEER readings. Only fully confluent, polarized monolayers should be evaluated for accurate results.
Culture Conditions
Cell culture media composition plays a crucial role in modulating tight junction formation. Variations in serum concentration, supplements, and pH can all affect TEER values. In addition, cells must be maintained in a stable environment, typically 37°C with 5% CO₂. TEER is sensitive to temperature fluctuations, and readings taken outside incubator conditions can rapidly decline. WPI recommends measuring samples on a warming plate or acclimating all samples to room temperature before measuring samples to compare. The duration of cell culture matters. Some cell types require several weeks to form tight junctions capable of yielding consistent TEER measurements.
Electrode Design and Placement
The type of electrode used impacts both the sensitivity and reproducibility of TEER data. Common designs include handheld "chopstick" electrodes and chamber-based systems. WPI offers a variety of TEER electrode solutions, each suited to different applications:
- STX4: An adjustable electrode with replaceable blades, for hands-free measurements in 24-well plates. It offers flexibility and durability.
- STX-HTS: Designed for high-throughput screening, this electrode is compatible with the EVOM manual meter for use in 24- and 96-well plate formats.
- EndOhm: A high-end chamber system for TEER measurement, providing uniform current density and improved accuracy. It is compatible with 6-, 12-, and 24-well plates for hands-free measurement.
Proper electrode positioning is vital to avoid edge effects and current leakage. Electrodes must also be properly disinfected and well-maintained to prevent biofilm formation or corrosion that could skew results.
WPI's EVOM™ Auto addresses many of the challenges associated with manual electrode placement by users. Designed for automated high-throughput TEER screening, the EVOM™ Auto features an integrated electrode head that plugs directly into the unit. Electrode heads are available for different plate types, including 24-well and 96-well formats, and are selected based on both well format and manufacturer compatibility. This automation eliminates user-dependent variability and enhances data reproducibility, making it ideal for high throughput screening applications.
Measurement Technique
WPI’s EVOM™ technology is the gold standard for TEER measurement. TEER measurements are typically performed using an AC signal at a standardized frequency (e.g., 12.5 Hz) to prevent electrode polarization and any adverse physiological effects on samples. WPI’s meters are designed with the option of subtracting the background resistance of the culture insert and medium automatically, delivering the true TEER value. This built-in capability ensures greater accuracy and minimizes the need for manual calculation. Data storage directly on the instrument eliminates the possibility of manual human data recording errors. Operator technique, including the timing and consistency of measurements, contributes significantly to data variability. Standardizing protocols across users can help improve reproducibility.
Membrane and Insert Properties
The physical characteristics of the membrane insert used in cell culture also influence TEER. Factors such as pore size, membrane material (polycarbonate vs. polyester), and thickness affect cell attachment and junction formation. Coatings with extracellular matrix proteins like collagen or fibronectin can enhance cell adhesion and promote tighter barriers, which can alter resistance/TEER measurements.
Contamination and Cell Health
TEER is highly sensitive to the physiological state of the cell monolayer. Contaminants such as mycoplasma or bacteria can compromise tight junctions and dramatically reduce resistance. Similarly, cell stress from nutrient depletion, overgrowth, or exposure to toxins can lower TEER. Routine checks for contamination and assessments of cell viability should be part of the TEER workflow.
Ready to Improve Your TEER Measurements?
Accurate TEER measurements require a holistic approach to experimental design. From choosing the right cell type to maintaining optimal culture conditions and employing precise measurement techniques, every step can influence the final readout. By understanding and controlling these variables—and incorporating advanced instrumentation like WPI’s EVOM™ Auto, EVOM™ Manual, STX-HTS series electrode, and EndOhm chambers—researchers can generate more reliable and reproducible TEER data crucial for barrier function studies and translational biomedical research.
Unlock the full potential of your barrier model research with WPI’s trusted lineup of TEER solutions. From manual precision to automated high-throughput screening, our EVOM™ systems and specialized electrodes are designed to deliver accurate, reproducible results every time.
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