TELOCYTES IN ENDOCARDIUM: Electron Microscope Evidence

Abstract

The term TELOCYTES was very recently introduced, for replacing the name Interstitial Cajal-Like Cells (ICLC). 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 (under the resolving power of light microscopy), extremely long (tens up to hundreds of micrometers), with a moniliform aspect (many dilations along), and having caveolae. The presence of telocytes in epicardium and myocardium was previously documented. We present here electron microscope images showing the existence of telocytes, with telopodes, at the level of mouse endocardium. Telocytes are located in the subendothelial layer of endocardium, and their telopodes are interposed in between the endocardial endothelium and the cardiomyocytes bundles. Some telopodes penetrate from the endocardium among the cardiomyocytes and surround them, eventually. Telopodes frequently establish close spatial relationships with myocardial blood capillaries and nerve endings. Because we may consider endocardium as a ‘blood–heart barrier’, or more exactly as a ‘blood–myocardium barrier’, telocytes might have an important role in such a barrier being the dominant cell population in subendothelial layer of endocardium.

Ultrastructural and immunohistochemical characteristics of telocytes in the skin and skeletal muscle of newborn rats

“…TCs are found to occupy certain sites in the tissue as they may be related to stem cell niches Luesma et al, 2013), blood capillaries (Ciontea et al, 2005;Gherghiceanu et al, 2010) and nerve bundles (Cretoiu et al, 2012a,b). In addition, they are found in close contacts with other cells including mast cells, fat cells, plasma cells, basophils, lymphocytes, or macrophages and also in non-cellular elements, e.g., collagen and elastic fibers (Popescu et al, 2005a,b).…”

Ultrastructural identification of telocytes in the muscularis of chicken ileum

“…F, fibroblast; N, nucleus; Nf, nerve fiber; Pd, podomer; Pm, podom; SMC, smooth muscle cell; Tc, telocyte; Tp, telopode. reporting the presence of TCs in other organs, including the epicardium (20), myocardium (21), endocardium (26), placenta (27) and skin (28). The role of TCs is unclear; however, based on the available data, numerous potential and relevant roles have been proposed.…”

A comprehensive guide to telocytes and their great potential in cardiovascular system

“…Multiple studies proved presence of three-dimensional spatial network of TCs in many parts of heart, such as: endocardium, myocardium, epicardium, valves and myocardial sleeves of pulmonary veins (7,31,32). However, the distribution of TCs is not homogenous in the whole heart -it is supposed that atria are more abundant in TCs than ventricles, but quantitative data is still missing (6).…”

“…TCs closely surround one third of endothelial cells in subendocardial tissue and thus, there is an assumption that TCs may be prerequisite component of endocardial blood-myocardium barrier (31).…”