Epithelial cell turnover - extracellular matrix relationship in the small intestine of human adults

In the human small intestine, proliferation, migration, differentiation and death of epithelial cells take place in separated compartments along the c rypt-villus axis. It has been shown in different cell systems that these ba sic biological activities are influenced by extracellular matrix proteins. To investigate possible relationships in the epithelium of the human adult small intestine we examined immunohistochemically the distribution of type IV collagen, laminin, fibronectin and tenascin, and compared the sites of t heir expression with the various cell activities. Epithelial cell prolifera tion and cell death have been detected by an antibody against Ki-67 and the TUNEL-assay, respectively. The results show that Ki-67 staining is restric ted to the crypts and TUNEL-positive cells are only present in the upper vi llus region. Type IV collagen is uniformly present in the epithelial baseme nt membrane along the crypt-villus axis providing a scaffold for other comp onents of the extracellular. p matrix. Laminin appears to be associated wit h epithelial cell differentiation, since it is strongly expressed in the vi lius basement membrane but only weakly underneath the crypt epithelium. Alt hough fibronectin displays a staining pattern similar to that of laminin, i t might rather be responsible for cell adhesion. Strong indications have be en found that tenascin could be related to epithelial cell death since it w as particularly expressed at the villus tip, where the cells undergo apopto sis.