Telocytes transfer extracellular vesicles loaded with micro RNA s to stem cells

Telocytes ( TC s) are cells ubiquitously distributed in the body and characterized by very long and thin prolongations named telopodes (Tps). Cardiac TC s are the best characterized TC s for the moment. Tps release extracellular vesicles ( EV s) in vivo and in vitro suggesting that TC s regulate the activity of other cells by vesicular paracrine signals. TC s have been found within the stem cell niche of several organs. Electron microscopy or electron tomography has shown that Tps are located in close vicinity of stem cells ( SC ). Since stem cell regulation by niche components involves paracrine signalling, we have investigated if TC s could be part of this mechanism. Using fluorescent labelling of cells and EV s with calcein and Cy5‐miR‐21 oligos, we provide evidence that TC s can modulate SC through EV s loaded with micro RNA s. TC s deliver micro RNA to cardiac stem cells ( CSC s), as well as to other types of SC s ( e.g . hematopoietic SC ) indicating that this mechanism is not restricted to cardiac tissue. We also found that CSC s deliver micro RNA loaded EV s to TC s, suggesting that there is a continuous, post‐transcriptional regulatory signal back and forth between TCs and SC . In conclusion, our data reveal the existence of a reciprocal (bidirectional) epigenetic signalling between TC s and SC .