Identification of telocytes in the lamina propria of rat duodenum: transmission electron microscopy

Abstract

Recently the new term 'telocytes' has been proposed for cells formerly known as interstitial Cajal-like cells. In fact, telocytes are not really Cajal-like cells, they being different from all other interstitial cells by the presence of telopodes, which are cell-body prolongations, very thin, extremely long with a moniliform aspect. The identification of these cells is based on ultrastructural criteria. The presence of telocytes in others organs was previously documented. We reported for the first time, an ultrastructural study of telocytes in the lamina propria of rat duodenum. Our findings show that typical telocytes are present in the rat duodenum. Telocytes are located in the lamina propria, immediately below mucosal crypts. Telopodes frequently establish close spatial relationships with immune cells, blood vessels and nerve endings. On the basis of their distribution and morphology, we suggest that these cells may be involved in immune response and in our opinion, it may be possible that different locations of telocytes could be associated with different roles.

Fig 1

Rat duodenum. Non-conventional light microscopy; objective 100×. Tissue fixed with glutaraldehyde–paraformaldehyde and post-fixed in OsO4. Thin section of Aradilte-embedded material was stained with toluidine blue. At least three telocytes (asterisks) are present in the interstitium among crypt (cr).

Fig 2

Telocyte typical ultrastructural features. (A) Telocytes are found in close opposition to nervous trunks (nt) and blood vessels (v). Square marked area in (A) are enlarged in (B) and (C). (B, C) The perinuclear cytoplasm contains a small Golgi complex (arrows), elements of rough endoplasmic reticulum (rer) and distally, presents abundant mitochondria (m) and polyribosomes (asterisks). In this case, the surface cell membranes not covered with a basal lamina. TC: telocyte; MEC: mucosal epithelial cell.

Fig 3

The shape of the telocytes is according to the number of their telopodes (tp). (A) Piriform for one prolongation. Inset: gap junction connecting the processes of two telopodes (tp1, tp2). (B) Triangular shape for two telopodes in the vicinity of a blood vessel (v). TC: telocytes; MEC: mucosal epithelial cell.

Fig 4

Relation of telocytes with other cells in the lamina propria. (A) The processes of a telocyte establish numerous interactions with adjacent cells in the lamina propria. A multicontact synapsis between an eosinophil and a telopode indicated by black rectangular area. Blue and red square illustrating higher magnification of telopodes (tp) from (A) in (B) and (C), respectively. (B) Distinctive dichotomous pattern of branching (arrows). (C) Direct cellular contact (arrowhead) between two telopodes (tp1, tp2) showing junctional complexes. MEC: mucosal epithelial cell; LY: lymphocyte; E: eosinophile cells; e: endothelial cell.

Fig 5

Electron micrographs show details of telopodes (tp) from lamina propria of rat duodenum. Exosomes (arrowhead) emerge from telopodes in the interstitial space.

Fig 6

Close contact between telocyte (TC) and enterochromaffin cells (EC). Inset: electron-dense reinforcements in telocyte membrane (arrows). Note the enterochromaffin cell with large amounts of pleomorphic secretory granules. MEC: mucosal epithelial cell; m: mitochondria.