The primary cilium of telocytes in the vasculature: electron microscope imaging

Abstract

Blood vessels are highly organized and complex structure, which are far more than simple tubes conducting the blood to almost any tissue of the body. The fine structure of the wall of blood vessels has been studied previously using the electron microscope, but the presence the telocytes associated with vasculature, a specific new cellular entity, has not been studied in depth. Interestingly, telocytes have been recently found in the epicardium, myocardium, endocardium, human term placenta, duodenal lamina propria and pleura. We show the presence of telocytes located on the extracellular matrix of blood vessels (arterioles, venules and capillaries) by immunohistochemistry and transmission electron microscopy. Also, we demonstrated the first evidence of a primary cilium in telocytes. Several functions have been proposed for these cells. Here, the telocyte-blood vessels cell proximity, the relationship between telocytes, exosomes and nervous trunks may have a special significance.

Fig 1

(A) Duodenal arteriole from Wistar rat. Positive immunostaining to CD117/c-kit in perivascular localization. Inset: Cell with fusiform body is intensely c-kit positive. (B) Positive control in rat jejunum. Nuclei were counterstained with Mayer haematoxylin. ar: arteriole.

Fig 2

Light microscopy of toluidine-blue stained semithin sections of the duodenum Wistar rats. A typical capillary (A) and arteriole (B) circumscribed by telocytes (arrows). Objective 40 × .

Fig 3

Electron micrograph showing the close relationship between arteriole and telocytes. (A) Telocyte covering collagen and elastic fibres present in the tunica adventitia. (B and C) Higher magnification of boxed areas in A. (B) Gap junction connecting the processes of two telopodes. (C) Two dilatations, podoms (pd1 and pd2) which accommodate rough endoplasmic reticulum. ar: arteriole; smcs: smooth muscle cells; tp: telopodes; nt: nervous trunk; TC: telocyte; pd: podom.

Fig 4

TEM images of telopodes next to a venule and capillary. (A) Several telopodes bordering the smooth muscle cells of a venule. (B) The capillary is partially surrounded by long telopodes. (C) Numerous telopodes encloses a capillary. smc: smooth muscle cell; tp: telopodes; nt: nervous trunk; TC: telocyte; c: capillary; ve: venule.

Fig 5

Transmission electron microscopy images of telocyte in close apposition to wall of venule. (A) A typical example of telocyte: long, thin and moniliform processes with dichotomous pattern (arrowhead) of branching. Black square illustrating a higher magnification of telocyte from A. (B) The perinuclear cytoplasm contains well-developed Golgi apparatus (G), mitochondria (m), numerous polyribosomes (asterisk) and intermediate filaments (f). Note the deep invagination (cilium-pit) corresponding to primary cilium. smc: smooth muscle cells; tp: telopodes; ax: axon; TC: telocyte; e: endothelial cell; cp: cilium-pit; pd: podom; ve: venule.

Fig 6

Duodenal venule. (A) Telocyte located in parallel between the cells of the vessel wall and a nerve trunk. Note as the cytoplasm of telocyte establishes interactions with vascular smooth muscle. Black rectangular illustrating the primary cilium. (B) Longitudinally section. Some telocytes exhibit a primary cilium. The basal body resides at the base of the cilium-pit and is associated with its membrane via the distal appendages (white arrow). Below the distal appendages are the subdistal appendages (black arrow). smc: smooth muscle cells; tp: telopodes; nt: nervous trunk; TC: telocyte; e: endothelial cell; ve: venule; G: golgi apparatus; m: mitochondria; rer: rough endoplasmic reticulum; li: lipid drop.

Fig 7

TEM. Isolated secretory vesicle with exosome morphology (arrow) from telocyte was located close to endothelial cell. nt: nervous trunk; TC: telocyte; c: capillary.