RECIPROCAL EXPRESSION OF LAMININ A-CHAIN ISOFORMS ALONG THE CRYPT-VILLUS AXIS IN THE HUMAN SMALL-INTESTINE

Background/Aims: Intestinal epithelial cell proliferation, migration, and differentiation are susceptible to various influences along the cr ypt-villus axis including compositional changes in the basement membra ne and differential expression of receptors for these components. Howe ver, laminin has been consistently detected at the epithelial basement membrane without significant variation in relation to the crypt-villu s functional unit. The aim of this study was to examine the distributi on of individual laminin chains. Methods: The patterns of distribution of laminin A, M (an A-chain variant), B1, and B2 chains as well as th e integrins alpha6beta1 and alpha6beta4, two laminin receptors, were d etermined by indirect immunofluorescence in the adult human small inte stine. Results: Markedly distinct patterns of laminin chain expression were observed along the crypt-villus axis. The A chain was found pred ominantly associated with the differentiated epithelial cells on the v illus whereas the M chain was restricted to the basement membrane of c rypts. However, both B1 and B2 chains were detected all along the inte stinal basement membrane. Furthermore, alpha6beta1 and alpha6beta4 int egrins were found to be expressed by all enterocytes. Conclusions: The se observations show a reciprocal expression of laminin isoforms along the crypt-villus axis and support the concept that the intestinal epi thelial basement membrane is subjected to intricate compositional chan ges.