FIGURE 13. Digitally Colored TEM Images of “Cotton”-Type Interactions Between Telocytes and Pacemaker Cells in the Sinoatrial Node.

(A to E) Close contacts between telopodes (blue) indicated by red arrows and PMC (brown). Violet arrows point to the exosomes and multivesicular bodies (pink) within the intercellular space enclosed by telopodes and PMC. There is an extracellular space of about ~200 nm between the membrane of the soma of the telocytes and of the telopodes and the plasma membrane of the PMC. Physical contact between the membranes of PMC and telocytes was never detected. Ectosomes, exosomes, and multivesicular bodies have been found in close contact to the plasma membrane of the PMC. High numbers of caveolae (white arrowheads), invaginations of the plasma membrane of the PMC, were found in the area in which exosomes and multivesicular bodies approached the plasma membrane of the PMC. B shows a virtually zoomed-in image of caveolae in the membrane of a pacemaker cell (brown). The nuclei of telocytes in the TEM images are indicated by the letter N. (F) Type of telocytes found in thin slices by TEM that has a cellular phenotype identical to that of the S100B⁺ telocytes in G found in immunolabeled whole-mount preparations. It is worth noting that this type of telocytes detected by TEM and immunohistochemistry have identical structures of telomeres, telopodes, and podoms. Vesicular-like structures detected by immunohistochemistry are indicated by violet arrows. Red arrows indicate to the regions in which vesicular release occurs. Abbreviations as in Figures 4 and 11.