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cells of the capillaries. Telocytes secrete a range of vesicles containing signaling
molecules to facilitate intercellular communication, which has been well-
documented in vitro [ 41 ]. These secreted factors likely regulate nearby cells (espe-
cially cardiac stem cells) via paracrine signaling [ 42 ].
Telocytes with different morphologies are found in various layers of the heart,and this cell type has discrete functions in different anatomical regions. For exam-
ple, epicardial telocytes secrete microvesicles as exosomes into the extracellular
matrix [ 43 ]. Endocardial telocytes are the most abundant cells in the sub-endothelial
layer of the endocardium, and they extend telopodes into the myocardium to form
direct connections with cells in this region [ 44 ]. In fact, the abundance of cardiac
telocytes in the subepicardium of rats is significantly higher when compared to the
endocardium. The density is higher in the atria compared to the ventricles [ 45 ].
Electron microscopy and immunohistochemistry was used to show that telocytes
are also present in the valves of the heart [ 46 ]. The telocyte meshwork that is formed
inside the heart valves likely provides mechanical support and confers flexibility to
this tissue, in addition to mediating communication amongst cells.
Faussone-Pellegrini and Bani [ 37 ] showed that telocytes are required during pre-natal heart development. Immature cardiac muscle cells are interconnected and they
are surrounded by telocytes, which provide a three-dimensional scaffold for the
myocardium during morphogenesis. After birth, the number of telocytes steadily
decrease until adulthood [ 47 ].
Fig. 8.2 Human myocardium visualized by light microscopy. Spindle-shaped cardiac telocytes
(anti-CD117 antibody, brown color) between cardiomyocytes and different connective tissue cells
inside a scar after a myocardial infarction. Diaminobenzidine was used as a chromogen. Cell
nuclei were stained with Mayer’s hematoxylin (Orig. Magn. 400×)
I. Varga et al.