Telocytes and putative stem cells in the lungs: electron microscopy, electron tomography and laser scanning microscopy

This study describes a novel type of interstitial (stromal) cell — telocytes (TCs) — in the human and mouse respiratory tree (terminal and respiratory bronchioles, as well as alveolar ducts). TCs have recently been described in pleura, epicardium, myocardium, endocardium, intestine, uterus, pancreas, mammary gland, etc. (see www.telocytes.com). TCs are cells with specific prolongations called telopodes (Tp), frequently two to three per cell. Tp are very long prolongations (tens up to hundreds of μm) built of alternating thin segments known as podomers (≤ 200 nm, below the resolving power of light microscope) and dilated segments called podoms, which accommodate mitochondria, rough endoplasmic reticulum and caveolae. Tp ramify dichotomously, making a 3-dimensional network with complex homo- and heterocellular junctions. Confocal microscopy reveals that TCs are c-kit- and CD34-positive. Tp release shed vesicles or exosomes, sending macromolecular signals to neighboring cells and eventually modifying their transcriptional activity. At bronchoalveolar junctions, TCs have been observed in close association with putative stem cells (SCs) in the subepithelial stroma. SCs are recognized by their ultrastructure and Sca-1 positivity. Tp surround SCs, forming complex TC-SC niches (TC-SCNs). Electron tomography allows the identification of bridging nanostructures, which connect Tp with SCs. In conclusion, this study shows the presence of TCs in lungs and identifies a TC-SC tandem in subepithelial niches of the bronchiolar tree. In TC-SCNs, the synergy of TCs and SCs may be based on nanocontacts and shed vesicles

The great screen anomaly—a new frontier in product discovery through functional metagenomics

Functional metagenomics, the study of the collective genome of a microbial community by expressing it in a foreign host, is an emerging field in biotechnology. Over the past years, the possibility of novel product discovery through metagenomics has developed rapidly. Thus, metagenomics has been heralded as a promising mining strategy of resources for the biotechnological and pharmaceutical industry. However, in spite of innovative work in the field of functional genomics in recent years, yields from function-based metagenomics studies still fall short of producing significant amounts of new products that are valuable for biotechnological processes. Thus, a new set of strategies is required with respect to fostering gene expression in comparison to the traditional work. These new strategies should address a major issue, that is, how to successfully express a set of unknown genes of unknown origin in a foreign host in high throughput. This article is an opinionating review of functional metagenomic screening of natural microbial communities, with a focus on the optimization of new product discovery. It first summarizes current major bottlenecks in functional metagenomics and then provides an overview of the general metagenomic assessment strategies, with a focus on the challenges that are met in the screening for, and selection of, target genes in metagenomic libraries. To identify possible screening limitations, strategies to achieve optimal gene expression are reviewed, examining the molecular events all the way from the transcription level through to the secretion of the target gene product

Telocytes: ultrastructural, immunohistochemical and electrophysiological characteristics in human myometrium.

Telocytes (TCs) have been described in various organs and species (www.telocytes.com) as cells with telopodes (Tps) - very long cellular extensions with an alternation of thin segments (podomers) and dilated portions (podoms). We examined TCs using electron microscopy (EM), immunohistochemistry (IHC), immunofluorescence (IF), time-lapse videomicroscopy and whole-cell patch voltage clamp. EM showed a three-dimensional network of dichotomous-branching Tps, a labyrinthine system with homocellular and heterocellular junctions. Tps release extracellular vesicles (mean diameter of 160.6\ub16.9\u200anm in non-pregnant myometrium and 171.6\ub14.6\u200anm in pregnant myometrium), sending macromolecular signals to neighbouring cells. Comparative measurements (non-pregnant and pregnant myometrium) of podomer thickness revealed values of 81.94\ub11.77 vs 75.53\ub11.81\u200anm, while the podoms' diameters were 268.6\ub18.27 vs 316.38\ub117.56\u200anm. IHC as well as IF revealed double c-kit and CD34 positive results. Time-lapse videomicroscopy of cell culture showed dynamic interactions between Tps and myocytes. In non-pregnant myometrium, patch-clamp recordings of TCs revealed a hyperpolarisation-activated chloride inward current with calcium dependence and the absence of L-type calcium channels. TCs seem to have no excitable properties similar to the surrounding smooth muscle cells (SMCs). In conclusion, this study shows the presence of TCs as a distinct cell type in human non-pregnant and pregnant myometrium and describes morphometric differences between the two physiological states. In addition, we provide a preliminary in vitro electrophysiological evaluation of the non-pregnant state, suggesting that TCs could influence timing of the contractile activity of SMCs

Telocytes, a distinct type of cell among the stromal cells present in the lamina propria of jejunum

Conventionally, cells described in the stroma of the intestinal wall are fibroblasts/fibrocytes, mast cells, plasma cells, eosinophils, macrophages and, interstitial cells of Cajal (ICCs), the latter being considered as the pacemakers of gastrointestinal rhythmicity. Recently, a new type of stromal cell called telocyte (TCs) was found in various cavitary and non-cavitary organs (www.telocytes.com). We show here direct electron microscopical evidence for the presence of TCs in the lamina propria of rat jejunum just beneath the epithelial layer of the mucosal crypts and in between the smooth muscle cells (SMCs) of muscularis mucosae. TCs are characterized by: several very long (tens to hundreds of µm) prolongations called telopodes (Tps). Tps (with caliber below the resolving power of light microscopy) display podomeres (thin segments ≤0.2 µm) and podoms (dilations accommodating caveolae, mitochondria, and endoplasmic reticulum). Tps present dichotomous branching and form a three dimensional network close to immune cells, SMCs or nerve bundles. TCs could play a role in intercellular signaling and control of local tissue homeostasi