Epithelial vs mesenchymal contribution to the extracellular matrix in the human intestine

The basement membrane (BM) underlying the epithelium of the intestine is generally believed to be of both epithelial and mesenchymal origin but the exact contribution of each tissue has not been directly examined in the human. In this study, we have used a newly described procedure to dissociate the human intestine into pure epithelial and corresponding mesenchymal fractions. Northern blot and RT-PCR analyses of the fractions for the presence of transcripts encoding extracellular matrix molecules revealed that the epithelium produces the formal BM molecules such as the alpha 1, alpha 2, and beta 1 chains of laminin-1 and laminin-2 and the alpha 5(IV) and alpha 6(IV) chains of collagen as well as fibronectin, a BM-associated molecule. Interestingly, the alpha 1(IV) chain of collagen, which associates with the alpha 2(IV) chain to form the main BM collagen network, as well as tenascin-C and decorin, two BM-associated molecules, was found to be exclusively of mesenchymal origin. Taken together, these data support the concept that in the human, as in experimental animals, the intestinal BM is composed of components produced from both the epithelium and the mesenchyme.