Apoptosis in the intestinal epithelium: Its relevance in normal and pathophysiological conditions

Apoptosis is now recognized as an important process responsible for mainten ance of the cellular balance between proliferation and death. Apoptosis is distinct from necrosis in that it is a programmed form of cell death and oc curs without any accompanying inflammation. This form of cell death can be induced by a wide range of cellular signals, which leads to activation of c ell death machinery within the cell and is characterized by distinct morpho logical changes. Apoptosis is especially relevant in the gastrointestinal t ract, as the mammalian intestinal mucosa undergoes a process of continual c ell turnover that is essential for maintenance of normal function. Cell pro liferation is confined to the crypts, while differentiation occurs during a rapid, orderly migration up to the villus. The differentiated enterocytes, which make up the majority of the cells, then undergo a process of program med cell death (apoptosis). Although apoptosis is essential for the mainten ance of normal gut epithelial function, dysregulated apoptosis is seen in a number of pathological conditions in the gastrointestinal tract. The cellu lar mechanisms regulating this tightly regimented process have not been cle arly defined and this topic represents an area of active investigation as d elineation of this process will lead to a better understanding of normal gu t mucosal growth. (C) 2000 Blackwell Science Asia Pty Ltd.