The Telocytes in the Subepicardial Niche

Abstract

A great interest has developed over the last several years in research on interstitial Cajal-like cells (ICLCs), later renamed to telocytes (TCs). Such studies are restricted by diverse limitations. We aimed to critically review (sub)epicardial ICLCs/TCs and to bring forward supplemental immunohistochemical evidence on (sub)epicardial stromal niche inhabitants. We tested the epicardial expressions of CD117/c-kit, CD34, Cytokeratin 7 (CK7), Ki67, Platelet-Derived Growth Factor Receptor (PDGFR)-α and D2-40 in adult human cardiac samples. The mesothelial epicardial cells expressed D2-40, CK7, CD117/c-kit and PDGFR-α. Subepicardial D2-40-positive lymphatic vessels and isolated D2-40-positive and CK7-positive subepicardial cells were also found. Immediate submesothelial spindle-shaped cells expressed Ki-67. Submesothelial stromal cells and endothelial tubes were PDGFR-α-positive and CD34-positive. The expression of CD34 was pan-stromal, so a particular stromal cell type could not be distinguished. The stromal expression of CD117/c-kit was also noted. It seems that epicardial TCs could not be regarded as belonging to a unique cell type until (pre)lymphatic endothelial cells are inadequately excluded. Markers such as CD117/c-kit or CD34 seem to be improper for identifying TCs as a distinctive cell type. Care should be taken when using the immunohistochemical method and histological interpretations, as they may not produce accurate results.

Two distinctive types of telocytes in gills of fish: A light, immunohistochemical and ultra‐structure study

“…CD117 activation is linked to cell adhesion, cell proliferation, differentiation, chemotaxis, and apoptosis (Margaritescu et al, 2011; Marjit, 2009). CD117 antibody is used to detect TCs in human heart (Iancu et al, 2019), human skin (Ceafalan et al, 2012), human scalp (Wang et al, 2020), human Placenta (Nizyaeva et al, 2018), human skeletal muscles (Bojin et al, 2011), human kidney (Rusu et al, 2018), bovine uterine tube (Abdelhafeez & Soliman, 2016), bovine teat (Wagener et al, 2018), mice heart (Li et al, 2015), mouse ovaries (Liu et al, 2016). CD117 may play a vital role in TCs functions involved in the transduction of intracellular signaling (Liang et al, 2013).…”

Morpho-functional changes of cardiac telocytes in isolated atrial amyloidosis in patients with atrial fibrillation

“…Since none of these markers is specific, a number of authors suggests using double immunohistochemical staining for identification of TCs: CD34 + /CD31 -, in contrast to CD34 + /CD31 + endothelial cells 27,29 , CD34 + /PDGFR-α +10 , CD34 + /S100 +59 , as well as C-kit + /vimentin +36 . The literature actively discusses the possibility of inaccurate identification of TCs at the light-optical level using different markers of IHC staining, in particular, during the differentiation of epicardial TCs, among which there may be cells expressing markers of lymphatic endothelial cells 72 . Thus, the absence of specific markers of TCs forces researchers to use various markers to identify these cells and, in our opinion, indicates the heterogeneity of their population or their ability to differentiate into other cell lines.…”

Lymphatic lacunae of the human eye conjunctiva embedded within a stroma containing CD34+ telocytes

“…26 Various studies regarding TCs have attempted to identify specific functional characteristics of these cells, but they often have not used unitary scientific methodology, as recently reported. 9,11,14,[27][28][29][30][31] However, despite the controversies regarding TCs, [9][10][11]32 they should be included in both the nomenclature and textbooks of histology. 33 Nevertheless, care should be taken on two-dimensional slices, as tangentially cut endothelial cells, or lymphatic capillaries, could generate false evidence of TCs.…”