Ligamentum arteriosum and its telocytes: An ultrastructure description

Results from my study have shown in 2022 the existence of telocytes (TCs) in mice ligamentum arteriosum (LA). Telocytes (TCs) are unique interstitial or stromal cells of mesodermal origin, defined by long cellular extensions called telopodes (Tps) which form a network, connecting them to surrounding cells. These Tps have dilated portions named podoms (usually containing mitochondria, endoplasmic reticulum and caveolae) and very thin segments (below resolving power of light microscopy), called podomers. Generally, transmission electron microscope revealed the existence of Tps with various conformations: (a) long, flattened irregular veils (ribbon-like segments) with knobs, corresponding to podoms, and (b) tubular structures (podomers) with uneven caliber because of irregular dilations (knobs)-the podoms. Also shown were numerous extracellular vesicles and exosomes released by the TCs which sometimes made direct contact with telopodes. Telopodes were observed communicating with each other through adherens junctions. Telopodes sandwiched between myocytes or in close proximity (0.01 μm) from nerve terminals were also observed. These data might be useful for understanding the role(s) of TCs in intercellular signaling and communication, neuromodulation as well as comprehension of pathologies like structural remodeling within the LA.