Integrins as mediators of epithelial cell-matrix interactions in the humansmall intestinal mucosa

The intestinal epithelium is a highly dynamic tissue, which depends on a va riety of factors for the regulation of its rapid renewal and expression of digestive functions. Over the last 10 years, it has become evident that amo ng these factors are cell interactions with the extracellular matrix, more specifically with the underlying basement membrane, through a series of spe cific cell membrane receptors, many of which are integrins. Integrins regul ate the assembly of adhesive junctions as well as the activation of various signaling pathways, leading to the modulation of gene expression. The anal ysis of the integrin repertoire along the crypt-villus axis in the human sm all intestinal epithelium identifies a number of beta 1 and beta 4 integrin s, showing differential patterns of expression relative to its two function al compartments. Among them are the integrins alpha 3 beta 1, alpha 7B beta 1 and the functional form of alpha 6 beta 4 that appear to be related, in concert with the distribution of their ligands, to the process of intestina l cell differentiation, and the integrins alpha 2 beta 1, alpha 1 beta 1, a lpha 5 beta 1, and the non-functional form of alpha 6 beta 4 that seem to b e coupled with the undifferentiated/proliferative status of crypt cells. Th ese observations delineate the potential complexity of the organization of epithelial cell-matrix interactions involved in the maintenance of the huma n intestinal crypt-villus axis. (C) 2000 Wiley-Liss, Inc.