In vitro assessment of epithelial electrical resistance in human esophageal and jejunal mucosae and in Caco-2 cell layers

Abstract

Objective. There is a need for a technique allowing studies of human mucosal specimens collected during different clinical conditions. This study elucidates if square wave pulse analysis discriminates between epithelial and transmural electrical resistance and if there is an association with transepithelial permeability of molecular probes. Methods. Mucosae from esophagus (surgical resections: n = 14; endoscopic biopsies: n = 15) and jejunum (n = 12) and Caco-2 cell monolayers were investigated in Ussing chambers. Transmural and epithelial electrical resistance were recorded by the use of standardized current pulses. Permeability was assessed using two fluorescein-labeled probes (weight 376 and 4000 Da). Results. Baseline epithelial electrical resistance was higher in esophageal mucosa (∼280 Ω*cm²), than in jejunal (∼10 Ω*cm²) and Caco-2 cells (∼140 Ω*cm²). The subepithelial contribution to the transmural resistance was higher in jejunal preparations (+88%) and Caco-2 cells (+75%), than in esophageal (+30%). During hypoxia the subepithelial resistance was unchanged, whereas the epithelial resistance decreased significantly in jejunal mucosa and Caco-2 cells. These findings coincided with increased transepithelial probe permeability and signs of disturbed morphology. Esophageal epithelia were resistant to hypoxia. However, exposure to deoxycholic acid and trypsin abolished the esophageal epithelial resistance and increased probe permeability. Endoscopic esophageal biopsies from patients with erosive reflux disease exhibited significantly lower epithelial resistance and higher current than healthy subjects. Conclusion. Square wave pulse analysis in Ussing chambers is suitable for assessment of epithelial electrical resistance that can reflect transepithelial permeability of molecular probes with known size. Moreover, the technique discriminated between healthy and reflux-diseased esophageal mucosal biopsies.

Key Words::

• caco-2 cells
• epithelial electrical resistance
• esophageal epithelium
• jejunal epithelium
• the Ussing pulse method
• transmural electrical resistance

Acknowledgements

The authors would like to thank Prof. Herbert Helander for excellent contributions and sharing of knowledge regarding morphology and histological analyses. The authors also acknowledge laboratory assistant Christina Ek, the nurses and surgeons at or connected to the Department of Gastrosurgical Research who made this study possible. The study received financial support by the Swedish Research Council (Grant no. K2010-55X-21432-01-2), the University of Gothenburg and the Sahlgrenska University Hospital (ALF-grants).

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.