Methods to Study Tight Junctions

Abstract

A cell in the ocean exchanges with a constant reservoir, that is not exhausted of nutrients consumed by the cell nor polluted by the wastes it excretes. On the contrary, when a cell belongs to a metazoan, the situation is completely different, as the ocean is now replaced by an extracellular milieu less than one micron thick, that would be quickly exhausted and spoiled, were it not by a circula- tory apparatus that continuously carries nutrients and wastes to and from to enormous areas of epithelia, where the exchange with the extracellular environment actually takes place. Thanks to this continuous puri fi cation and stability of the internal milieu performed mainly by “ transporting epithelia ”, metazoan cells can enormously simplify their housekeeping efforts, and engage instead in differentiation and multiple forms of organization (tissues, organs, systems) that enable them produce an astonishing diversity of higher organisms. Metazoan exist thanks to transporting epithelia. This chapter summarizes the main methods to study the structure and function of the tight junctions, with natural epithelia, as well as monolayers of cell lines grown in vitro on permeable supports