A re-examination of the cellular reticulum of fibroblast-like cells in the rat small intestine by scanning electron microscopy.

The organization and arrangement of fibroblast-like cells in the rat small intestine were re-examined by scanning electron microscopy after removal of the epithelium and underlying connective tissue components by HCl hydrolysis. In the villi, the fibroblast-like cells had numerous slender processes, and formed a dense and elaborate network like a sieve. It consisted of a large number of circular structures (circles) with various diameters ranging from 0.3 microm to 5 microm formed by the twining of slender processes. In the upper area of villi, numerous fragmental protrusions which were considered to be mainly parts of immune-related cells such as lymphocytes, eosinophils and macrophages extended from the circles. The cells around each tubular gland enclosed it like a basket. These findings suggest that in addition to the function as a skeleton for the villi and glands, the fibroblast-like cells in the upper area of villi may play an important role in regulating the migration of the immune-related cells between the epithelial layer and the underlying lamina propria by their cellular sieve-like structure and contractile ability.