Three-dimensional distribution of extracellular matrix in the mouse small intestinal villi. Laminin and tenascin.

To investigate the three-dimensional distribution of laminin and tenascin in the villi of the mouse small intestine, we designed a new tissue preparation procedure for confocal laser scanning microscopy. Fixed tissue was pretreated with sodium deoxycholate and immunostained. The specimens displayed intense immunofluorescence even in the deeper sites of the lamina propria. Laminin was distributed like a sheet in the basement membrane of the epithelium as well as that of the capillaries. Additionally, it was associated with some tubular structures in the lamina propria. Many pores were found in the laminin sheet. By comparison, tenascin was distributed at the epithelial basement membrane and in the underlying connective tissue exhibiting a striped pattern. Tenascin was observed wrapping around the capillary wall in a spiral but was absent at the tip of the villi except in the capillary wall. Pores in the staining pattern of tenascin were also found as was the case for laminin. This three-dimensional reconstruction made it possible to observe more clearly the localization of these two extracellular matrix molecules.