TELOCYTES - A Novel Type of Interstitial Cells

摘要

We have recently described a novel type of interstitial (stromal) cells - Telocytes (TC) - in several cavitary and non-cavitary organs from humans and other mammalians. TC have a small cell body, but specific (unique) prolongations that we named Telopodes (Tp). Therefore, the simplest definition for TC is: cells with Tp. Tp are characterized by: a) number (1-5/cell, frequently 2 or 3); b) length (tens up to hundreds of μm); c) moniliform aspect - an alternation of thin segments, podomeres (with caliber under 200 nm, below the resolving power of light microscopy) and dilated segments, podoms, which accommodate mitochondria, (rough) endoplasmic-reticulum and caveolae, the so-called "Ca~(2+) uptake/release units"; d) dichotomous branching pattern forming a 3D network, a labyrinthine system with complex homo- and heterocellular junctions, revealed only by electron tomography. Significantly, TC (especially Tp) release shed vesicles and exosomes, sending macromolecular signals to neighbor cells, thus modifying their transcriptional activity, eventually. The lenghth and ramifications of Tp together with the intercellular junctions and the releasing of shed vesicles or exosomes suggest an essential role of TC in intercellular signaling and coordination. Noteworthy, at least in some organs (e.g. heart and lungs) TC and stem cells (SC) are located in tandem within the so called stem cell niches, where Tp surround stem cells (SC). TC heterocellular contacts, as well as the impulsion of shed vesicles assure TC - SC sinergy. Presumably, TC "nurse" SC in stem cell niches.