Heart Wall - Tissue Functioning and Remodeling in the Circulatory and Ventilatory Systems - page 300

6.2.2 Telocytes

Telocyte, originally called interstitial Cajal-like cell, 47 localizes to the myocardial
interstitium, myocardial sleeves of pulmonary veins, as well as subendothelial layer
of endocardium [ 576 - 578 ]. This cell differs from other interstitial cell types, such
as fibroblasts, fibrocytes, fibroblast-like cells, and mesenchymal cells.
Telocyte is endowed with 2 or 5 long, slender, moniliform (many dilations
throughout the length) prolongations, the so-called telopodes (length 0.1-0.4 mm;
thickness 0.1-0.5

m) [ 578 ]. These cytoplasmic processes establish close contacts
between each other as well as with capillaries, nerve endings, cardiomyocytes, and
other connective tissue cells. Telopodes of endocardial telocytes can penetrate the
myocardium and extend among the cardiomyocytes and surround them. Telocyte
synthesizes stem cell factor receptor [ 577 ].
Telocytes may be involved in: (1) intercellular signaling; (2) cardiac repair
and remodeling; and (3) stem cell nursing, as it contacts cardiac stem cells in
subepicardial cardiogenic niches [ 579 ]. A heterogeneous population of round stem
and progenitor cells (size 6-10 m) lodges in mammalian adult heart, more

precisely in epicardial stem cell niches. Telocytes make a supportive interstitial
network for stem cells and progenitors in the stem cell niche.

6.2.3 Epicardial Adipose Tissue and Adipokines

The epicardial adipose tissue, a source of free fatty acid, generates various sub-
stances such as adipokines that include adiponectin , leptin , resistin , apelin ,and
visfatin . Adipokines exert cardiovascular effects either directly or by central stim-
ulation of the sympathetic nervous system. Epicardial adipose tissue may serve
as a cardiac risk marker and be implicated in the development of cardiac pathol-
ogy [ 580 ].

47 Interstitial cells of Cajal are considered to be pacemakers of the motility of the gastrointestinal
tract, where they have been discovered. Peculiar interstitial cells have also been detected in the
urinary tract, blood vessels, pancreas, male and female reproductive tracts, mammary glands,
placenta, and heart.