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. Author manuscript; available in PMC: 2022 Nov 14.
Published in final edited form as: JACC Clin Electrophysiol. 2022 Sep 28;8(10):1191–1215. doi: 10.1016/j.jacep.2022.07.003

FIGURE 11. Interstitial Cells Within Mouse SAN Imaged by TEM.

FIGURE 11

Telocytes were identified by high-resolution transmission electron microscopy (TEM) and were found near pacemaker cells (PMC). (A) Semi-thin sections of sinoatrial nodal (SAN) stained with toluidine blue illustrate the heterogeneous shapes of interstitial cells. Black arrows indicate the nuclei of the interstitial cells. AI and AII present bipolar cells, and piriform/fusiform unipolar cells are shown in AIII and AIV. An interstitial cell with branching cellular extensions is shown in AI. The long and thin cytoplasmic extensions of interstitial cells (telopodes) are shown in AII and AIII. A flattened interstitial cell is illustrated in AIV. (B) Digitally colored TEM images that illustrate the ultrastructure of different types of telocytes (blue) located near PMC (brown), as well as exosomes shed from telocytes (pink). The “bead”-like regions of telopodes, defined as podoms, are indicated by black arrowheads. Scarce organelles (mitochondria, endoplasmic reticulum, caveolae, and larger membranous vesicles) can be visualized in the soma and in the podoms of telocytes. Telocyte nuclei in the TEM images are indicated by the letter N. The regions of interest highlighted by red dot boxes are shown in (C) and (E) at higher zoom.