121
for this cell type in Terminologia Histologica [ 38 ]. Díaz-Flores et al. [ 39 ] originally
defined the telocyte cell population as stromal fibroblastic cells enriched for CD34.
Meanwhile, Ivey and Tallquist [ 12 ] used “cardiac telocyte” interchangeably with
“cardiac fibroblast.” Furthermore, Bei et al. [ 35 ] showed that cardiac telocytes have
distinct morphologies and immunohistochemical properties when compared to
fibroblasts cultured in vitro. Rusu et al. [ 40 ] also demonstrated that a subpopulation
of cardiac telocytes are endothelial derived. Thus, whether telocytes represent a
discrete cell population or whether are a special subtype of fibroblasts or endothelial
cells remains to be determined.
Cardiac telocytes form a three-dimensional network and are connected to eachother at cell-cell junctions. They also form these junctions with other cardiac cell
types including cardiomyocytes, cardiomyocyte progenitors, mastocytes, pericytes,
immune reactive cells, macrophages, Schwann cells, fibroblasts, and endothelial
Fig. 8.1 Human myocardium visualized by transmission electron microscopy. Telocytes display
long cytoplasmic prolongations in the loose connective tissue with collagen fibers (CF) between
cardiac muscle cells (CMC). Thin segments are called podomers (1), and the thicker dilated seg-
ments containing membrane-bound cell organelles are podoms (2). Between the cardiac muscle
cell and the prolongation of the telocyte, a direct junction (nanocontact) is visible (arrow) (Orig.
Magn. 8900×)
8 The Non-cardiomyocyte Cells of the Heart. Their Possible Roles...