what is the teer for in vitro bbb model

3 min read 22-01-2025

The transendothelial electrical resistance (TEER) value is a crucial parameter in assessing the integrity and functionality of an in vitro blood-brain barrier (BBB) model. Understanding TEER is essential for researchers working with these models, as it provides a direct measure of the barrier's tightness and its ability to restrict the passage of molecules. This article will explore the significance of TEER in the context of in vitro BBB models.

Understanding TEER and its Significance in BBB Models

TEER measures the electrical resistance across a cell monolayer. In the context of an in vitro BBB model, this monolayer is formed by cells that mimic the endothelial cells lining the blood vessels in the brain. A high TEER value indicates a tight barrier with low permeability, closely resembling the in vivo BBB. Conversely, a low TEER value suggests a leaky barrier, indicating compromised integrity and reduced functionality.

How TEER Reflects BBB Integrity

The tight junctions (TJs) between endothelial cells are the primary determinants of BBB permeability. These TJs restrict the passage of many substances from the blood into the brain. The TEER value is directly correlated with the number and functionality of these TJs. A well-formed BBB model with strong, functional TJs will exhibit high TEER, reflecting the barrier's ability to selectively control the passage of molecules.

Monitoring TEER During BBB Model Development

Monitoring TEER throughout the in vitro BBB model's development is critical. It allows researchers to track the formation and maturation of the cell monolayer. Changes in TEER over time can provide insights into the model's stability and functionality. A consistent high TEER value over several days confirms the establishment of a robust BBB model suitable for subsequent experiments.

TEER as a Quality Control Measure

TEER serves as a vital quality control measure for in vitro BBB models. Before conducting any experiments, researchers must ensure the model exhibits an acceptable TEER value. This ensures the model accurately reflects the in vivo BBB's properties and produces reliable experimental results. Inconsistently low TEER values indicate a flawed model unsuitable for reliable data generation.

TEER and Drug Permeability Studies

The TEER value is essential in drug permeability studies. By measuring the rate at which a drug molecule crosses the BBB model at a known TEER, researchers can estimate the molecule's ability to penetrate the blood-brain barrier in vivo. This is crucial for predicting the drug's potential efficacy in treating neurological disorders.

Factors Influencing TEER Values

Several factors influence TEER values, including:

Cell type: Different cell lines exhibit varying TEER values. Immortalized cell lines like hCMEC/D3 are commonly used and have well-established TEER ranges.
Culture conditions: Factors like cell seeding density, culture medium composition, and temperature all impact TEER.
Maturation time: The TEER value typically increases over time as the cell monolayer matures and forms tight junctions.
Experimental manipulations: Treatments or experimental interventions may transiently alter TEER, highlighting their effects on BBB integrity.

Interpreting TEER Results

While TEER provides valuable information, it's crucial to interpret results in the context of other parameters. A high TEER does not definitively guarantee a perfectly functional BBB model. Additional assessments, such as permeability assays and immunocytochemistry, are necessary for comprehensive characterization.

Ideal TEER Values

The ideal TEER value varies depending on the specific in vitro BBB model used. However, values generally exceeding 200 Ω·cm² are considered indicative of a relatively tight barrier. These values are usually observed after several days of cell culture, allowing time for TJ formation and monolayer maturation. Always consult published literature specific to the cell line and model used for appropriate TEER benchmarks.

Conclusion: TEER's Crucial Role in In Vitro BBB Models

TEER is a critical parameter for assessing the integrity and functionality of in vitro BBB models. It provides a readily measurable indicator of barrier tightness, reflecting the presence and function of tight junctions between endothelial cells. By monitoring TEER during model development and using it as a quality control measure, researchers can ensure the reliability and physiological relevance of their in vitro BBB models for drug permeability studies and other investigations related to the central nervous system. Continuous monitoring and interpretation of TEER, along with other supportive assays, is paramount for successful in vitro BBB research.