Polarized monolayers formed by epithelial cells on a permeable and translucent support

Area of Science:

• Cell Biology
• Epithelial Physiology
• Membrane Transport

Background:

• Transporting epithelia play vital roles in physiological processes.
• In vitro models are essential for studying epithelial cell behavior.
• Madin-Darby canine kidney (MDCK) cells are a widely used model for epithelial research.

Purpose of the Study:

• To characterize the in vitro properties of MDCK cell monolayers as a model for transporting epithelia.
• To investigate the ion and water transport mechanisms across MDCK monolayers.
• To elucidate the structural and functional basis of the MDCK epithelial barrier.

Main Methods:

• Culturing MDCK cells at high densities to form confluent monolayers on collagen-coated supports.
• Measuring electrical resistance and spontaneous potential across the monolayers.
• Assessing ion and water flux using electrophysiological and tracer techniques.
• Investigating the role of pH and calcium ions in barrier function.

Main Results:

• MDCK monolayers rapidly developed high electrical resistance and functional polarization.
• The barrier exhibited properties of a 'leaky' epithelium with selective Na+ and Cl- permeability.
• Negative charges on the barrier influenced ion selectivity, which was pH-dependent.
• Calcium ions were critical for maintaining junctional integrity and barrier function.

Conclusions:

• MDCK cell monolayers serve as a robust in vitro model for studying transporting epithelia.
• The study identified key characteristics of the MDCK epithelial barrier, including its charge selectivity and dependence on calcium.
• Findings provide insights into the mechanisms of ion and water transport in epithelial tissues.