Telocytes in pleura: two- and three-dimensional imaging by transmission electron microscopy

Abstract

Information about the ultrastructure of connective (interstitial) cells supporting the pleural mesothelium is scarce. Our aim has been to examine whether telocytes (TCs) are present in pleura, as in epicardium and mesentery. TCs are a distinct type of cell, characterized by specific prolongations named telopodes (Tp). We have used transmission electron microscopy (TEM) and electron tomography (ET) to determine whether ultrastructural diagnostic criteria accepted for TCs are fulfilled by any of the cell subpopulations existing in the sub-mesothelial layer in mouse and human pleura. TCs have been identified with TEM by their characteristic prolongations. Tp appear long and moniliform, because of the alternation of podomeres (thin segments of less than 0.2 μm) and podoms (small dilations accommodating caveolae, mitochondria, and endoplasmic reticulum). Tp ramifications follow a dichotomic pattern and establish specialized cell-to-cell junctional complexes. TCs, via their Tp, seem to form an interstitial network beneath the mesothelium, covering about two-thirds of the abluminal mesothelial layer. ET has revealed complex junctional structures and tight junctions connecting pleural TCs, and small vesicles at this level in Tp. Thus, pleural TCs share significant similarities with TCs described in other serosae. Whether TCs are a (major) player in mesothelial-cell-induced tissue repair remains to be established. Nevertheless, the extremely long thin Tp and complex junctional structures that they form and the release of vesicles (or exosomes) indicate the participation of TCs in long-distance homo- or heterocellular communication.Electronic supplementary materialThe online version of this article (doi:10.1007/s00441-010-1095-0) contains supplementary material, which is available to authorized users.

Wt1-expressing progenitors contribute to multiple tissues in the developing lung

“…In late gestational stages, CD34 expression is observed in CD31-negative, fibroblast-like cells, with long prolongations. These CD34 ϩ cells have been called "telocytes," and they had been described in the trachea and lungs (16,34,44). However, different from what has been described for telocytes, we could not find c-Kit expression in these CD34 ϩ cells.…”

Satellite Cells and the Muscle Stem Cell Niche

“…These findings also raise several interesting questions including: How do satellite cells respond to increased adipocytes and fibroblasts in the aforementioned physiological and pathological conditions? Recent observations regarding the effect of fibrosis on the stiffness of the ECM raise the question as to whether increased depositions from fibroblasts or adipocytes can alter myofiber stiffness and therefore affect the physiological roles attributed to satellite cells (152; (230,414,543). Although their exact role in muscle regeneration is still unknown, the finding that these cells secrete VEGF suggests telocytes are an important player in promoting satellite cells self-renewal, facilitating vasculogenesis, and preventing fibrosis (132; further discussed in sect.…”

Upregulation of ULK1 expression in PC-3 cells following tumor protein P53 transfection by sonoporation

“…The assay was conducted as follows: 50 µl MTT Transmission electron microscopy. PC3 cells from the three groups were sliced into ultra-thin specimens according to the conventional method (29). Specimens were then observed and images were captured using transmission electron microscopy (Hitachi S-4800; Hitachi, Ltd., Tokyo, Japan) at magnification, x24,500.…”