Telocytes in invertebrates

Vertebrate telocytes (TCs) are stromal cells described in humans and rodens cavitary and non cavitary organs such as heart, gut, gallblader, uterus, lung, pancreas, mammary gland, skeletal muscles. Telocytes, present in many types of tissues, are strategically located among specific resident cells, close to the capillaries and to the nerve endings. TCs are always characterized by a small cell body, containing the nucleus and very thin, long tubular processes named telopodes (TPs) that are considered the ultrastructural peculiar trait of these cells. Each telopode, long and convoluted is moniliform showing thin tubes (podomers) alternated with dilations (podoms). TCs may contact with each other and with virtually all type of cells forming a close network. The cross talk among TCs and the other cells can be direct via gap junctions, and/or indirect via the release of extracellular vesicles (multivescicular bodies, exosomes). TCs are hypothesized as an extensive intercellular information transmission system able to modulate homeostasis, stem cell activity, and other functions working as a primitive nervous system at the cellular level. Our study shows the existence of these type of cells in invertebrate body wall and we firstly identified telocytes in medicinal leech body. An ultrastructural portrait and immunophenotypic characteristics as well as the possible role played by invertebrate telocytes has been proposed.