Ussing Chamber Models

A method to study several intestinal barrier related functions in an ex vivo (outside body) setup by use of physiologically active intestinal biopsies derived from various locations along the human intestinal tract.

The Ussingchamber system was introduced by the Danish scientist Hans Ussing in the early 1950s. The system is composed of a chamber, a water jacket to maintain physiological temperature, a gas stream system to maintain a physiological buffer while providing a gas lift circulation, and a linked data acquisition system. Although initially developed to study ion transport mechanisms across the epithelia, Ussing chambers have also been applied to drug and other compound permeation studies.

1. Sample collection and mounting
Human biopsies are collected either from the colon during colonoscopy, or from the duodenum during gastroscopy. One biopsy is mounted per chamber and oriented to recreate the equivalent of the apical- and the basolateral sides of the intestinal barrier.

2. Running the Ussing chamber models
The chambers are run with a circulatory flow of saline buffer preheated to 37 degrees and continuously saturated with oxygen and carbon dioxide.

3. Measuring intestinal barrier permeability and transport
TER (Trans-Epithelial Resistance) represents the chemical resistance between the apical- and basolateral side and is measured as an indicator of intestinal integrity.
Paracellular transport (between cells) is evaluated using Fluorescein isothiocyanate (FITC)–Dextran by measuring fluorescence level and correlating to concentration using a standard curve. Transcellular transport (through cells) is evaluated using Horseradish peroxidase (HRP) and measured by use of ELISA.

The method is utilized to study in particular:

Studying intestinal barrier integrity means either evaluation of the tight junction complex that regulate the paracellular transport route or assessing the transcellular transport route going through the actual cells.

Studying transport across the intestinal barrier means monitoring either passive or active transport mechanisms, and the passage of various nutritional substances, fibres, pharmaceuticals, or other exogenous substances.

Studying biological responses means to identify and assess activation of biological pathways when invoked by external stimuli or exogenous substances. Examples of such biological responses would be inflammatory responses, hormonal responses (ex. glp-1), or the release of extracellular vesicles (exosomes).

Results show the normal level of paracellular permeability in the control (untreated biopsy); a slight increase with the stressor (DCA), no increase with 0,5 mg/ml fibre added, and a slight increase with the stressor and the fibre together.

Results show the normal transcellular permeability in the control (untreated biopsy); a clear increase in permeability with the stressor (DCA); no increase in permeability with 0,5 mg/ml fibre added alone; and an attenuation of transcellular permeability with the fibre and the stressor together.

This indicates that the addition of fibre has a protective effect on intestinal barrier transcellular transport in these human subjects.