The measurement of transepithelial electrical resistance (TEER) is a common technique to determine the barrier integrity of epithelial cell monolayers. However, it is remarkable that absolute TEER values of similar cell types cultured under comparable conditions show an immense heterogeneity. Based on previous observations, we hypothesized that the heterogeneity of absolute TEER measurements can not only be explained by maturation of junctional proteins but rather by dynamics in the absolute length of cell junctions within monolayers. Therefore, we analyzed TEER in epithelial cell monolayers of Caco2 cells during their differentiation, with special emphasis on both changes in the junctional complex and overall cell morphology within monolayers. We found that in epithelial Caco2 monolayers TEER increased until confluency, then decreased for some time, which was then followed by an additional increase during junctional differentiation. In contrast, permeability of macromolecules measured at different time points as 4 kDA fluorescein isothiocyanate (FITC)-dextran flux across monolayers steadily decreased during this time. Detailed analysis suggested that this observation could be explained by alterations of junctional length along the cell borders within monolayers during differentiation. In conclusion, these observations confirmed that changes in cell numbers and consecutive increase of junctional length have a critical impact on TEER values, especially at stages of early confluency when junctions are immature.

跨上皮电阻 (TEER) 的测量是确定上皮细胞单层屏障完整性的常用技术。然而，值得注意的是，在可比条件下培养的类似细胞类型的绝对 TEER 值显示出巨大的异质性。基于先前的观察，我们假设绝对 TEER 测量的异质性不仅可以通过连接蛋白的成熟来解释，还可以通过单层内细胞连接的绝对长度的动态来解释。因此，我们分析了 Caco2 细胞分化过程中上皮细胞单层中的 TEER，特别强调了单层内连接复合物和整体细胞形态的变化。我们发现在上皮 Caco2 单层中 TEER 增加直到汇合，然后下降一段时间，然后在连接分化期间进一步增加。相比之下，在不同时间点测量的大分子的渗透性，因为 4 kDA 异硫氰酸荧光素 (FITC)-葡聚糖跨单层通量在此期间稳步下降。详细分析表明，这种观察可以通过在分化过程中沿单层细胞边界的连接长度的变化来解释。总之，这些观察结果证实，细胞数量的变化和连接长度的连续增加对 TEER 值有重要影响，尤其是在连接不成熟的早期汇合阶段。随着 4 kDA 异硫氰酸荧光素 (FITC)-葡聚糖单层通量在此期间稳步下降，在不同时间点测量大分子的渗透性。详细分析表明，这种观察可以通过在分化过程中沿单层细胞边界的连接长度的变化来解释。总之，这些观察结果证实，细胞数量的变化和连接长度的连续增加对 TEER 值有重要影响，尤其是在连接不成熟的早期汇合阶段。随着 4 kDA 异硫氰酸荧光素 (FITC)-葡聚糖单层通量在此期间稳步下降，在不同时间点测量大分子的渗透性。详细分析表明，这种观察可以通过在分化过程中沿单层细胞边界的连接长度的变化来解释。总之，这些观察结果证实，细胞数量的变化和连接长度的连续增加对 TEER 值有重要影响，尤其是在连接不成熟的早期汇合阶段。详细分析表明，这种观察可以通过在分化过程中沿单层细胞边界的连接长度的变化来解释。总之，这些观察结果证实，细胞数量的变化和连接长度的连续增加对 TEER 值有重要影响，尤其是在连接不成熟的早期汇合阶段。详细分析表明，这种观察可以通过在分化过程中沿单层细胞边界的连接长度的变化来解释。总之，这些观察结果证实，细胞数量的变化和连接长度的连续增加对 TEER 值有重要影响，尤其是在连接不成熟的早期汇合阶段。