Telocyte

Telocytes are a type of interstitial (stromal) cells with very long (tens to hundreds of micrometres) and very thin prolongations (mostly below the resolving power of light microscopy) called telopodes.

Figure 1. Human non-pregnant myometrium in cell culture; day 3; the first passage. Giemsa staining. One TC establishing contacts with a myocyte by a Tp of about 65 mm long. Photographic composition of 4 serial phase contrast images; original magnification 40x. In red rectangles, a higher magnification clearly shows the moniliform aspect; at least 40 specific dilations (podoms) interconnected by thin segments (podomeres) are visible in a ‘beadlike’ fashion.

Figure 2. Digitally coloured TEM image shows TC (blue) in human subepicardium, bordering the peripheral cardiomyocytes (CM, highlighted in brown). The TC has three telopodes, illustrating: a) the distinctive dichotomous pattern of branching (arrows); b) Tp are very thin at the emergence of the cell body; c) alternating podoms and podomeres. Note that some portions of podomeres have the same thickness as collagen fibrills, which make them impossible to be observed under light microscopy. E - elastin Scale bar - 2 mm.

Figure 3. Human exocrine pancreas. TC (blue) form with their typical Tp a network around acini. Note the stromal synapse (red arrows) between a mast cell and the Tp of a TC. Courtesy of Dr. M.I. Nicolescu, Department of Cellular and Molecular Medicine, ‘Carol Davila’ University of Medicine and Pharmacy, Bucharest, Romania.

Figure 4. Human resting mammary gland stroma. One TC hallmark, namely Tp, appears very long and convoluted. Note homocellular junctions marked by red circles, as well as shed vesicles (blue) and an exosome (violet).

Figure 5. Human term placenta. The TC (blue) has few organelles in the perinuclear area and 3 emerging Tp (red arrows); black arrowheads mark the dichotomic branching points. Note the podoms and podomeres. Black arrow points the junction between a Tp and a smooth muscle cell (SMC, colored in brown). Reproduced with permission from [2].

Figure 6. Non-pregnant myometrium. Digitally colored TC (blue) with 3 Tp that encircle bundles of cross-cut smooth muscle cells (SMC, Sienna brown); N - nuclei. Reproduced with permission from [1].

Figure 7. Rat jejunum. A typical Tp (blue) located between smooth muscle cells (SMC) and nerve endings. Note a large podom and the corresponding podomeres. TC body is not captured in the image. Courtesy of Dr. D. Cretoiu, Department of Cellular and Molecular Medicine, ‘Carol Davila’ University of Medicine and Pharmacy, Bucharest, Romania.

Figure 8. Rat stomach, multicontact stromal synapses between two TC, a plasma cell and an eosinophil, respectively. 3-D image computer-aided reconstruction from 9 serial ultrathin sections; original magnification 1,500x. The upper inset shows contact points where the distance between both cell membranes (Tp membrane and plasma-cell membrane) is 15 nm or less (in violet), seen from the plasma cell cytoplasm. In the lower inset Tp were rendered transparent in order to depict the same synapse. Reproduced with permission from [22].