FIB‐SEM tomography of human skin telocytes and their extracellular vesicles

We have shown in 2012 the existence of telocytes (TCs) in human dermis. TCs were described by transmission electron microscopy (TEM) as interstitial cells located in non‐epithelial spaces (stroma) of many organs (see www.telocytes.com ). TCs have very long prolongations (tens to hundreds micrometers) named Telopodes (Tps). These Tps have a special conformation with dilated portions named podoms (containing mitochondria, endoplasmic reticulum and caveolae) and very thin segments (below resolving power of light microscopy), called podomers. To show the real 3D architecture of TC network, we used the most advanced available electron microscope technology: focused ion beam scanning electron microscopy (FIB‐SEM) tomography. Generally, 3D reconstruction of dermal TCs by FIB‐SEM tomography revealed the existence of Tps with various conformations: (i) long, flattened irregular veils (ribbon‐like segments) with knobs, corresponding to podoms, and (ii) tubular structures (podomers) with uneven calibre because of irregular dilations (knobs) – the podoms. FIB‐SEM tomography also showed numerous extracellular vesicles (diameter 438.6 ± 149.1 nm, n = 30) released by a human dermal TC. Our data might be useful for understanding the role(s) of TCs in intercellular signalling and communication, as well as for comprehension of pathologies like scleroderma, multiple sclerosis, psoriasis, etc.     

Energetic metabolism during acute stretch-related atrial fibrillation

Background and methods Perturbations in energetic metabolism and impaired atrial contractility may play an important role in the pathogenesis of atrial fibrillation (AF). Besides, atrial stretch is commonly associated with AF. However, the atrial energetics of stretch-related AF are poorly understood. Here, we measured indicators of energy metabolism during acute stretch-related AF. PCr, adenine nucleotides, and derivatives concentrations as well as the activity of the F₀F₁-ATPase and Na,K-ATPase were obtained after 1 h of stretch and/or AF in isolated rabbit hearts and compared to control hearts without stretch and AF. Results After 1 h of stretch-related AF, the total adenine nucleotides’ pool was significantly lower (42.2 ± 2.6 vs. 63.7 ± 8.3 μmol/g protein in control group, P < 0.05) and the PCr/ATP ratio significantly higher (2.3 ± 0.3 vs. 1.1 ± 0.1 in control group P < 0.05), because of ATP, ADP, and AMP decrease and PCr increase. The sum of high-energy phosphate compounds did not change. There were no significant differences in F₀F₁-ATPase nor Na,K-ATPase activity between the groups. Conclusions Results show that in this experimental model, acute stretch-related AF induces specific modifications of atrial myocytes energetics that may play a pivotal role in the perpetuation of the arrhythmia.     

A C-terminal fragment of Cyclin E, generated by caspase-mediated cleavage, is degraded in the absence of a recognizable phosphodegron

We have previously shown that caspase-mediated cleavage of Cyclin E generates p18-Cyclin E in hematopoietic tumor cells. Its expression can induce apoptosis or sensitize to apoptotic stimuli in many cell types. However, p18-cyclin E has a much shorter half-life than Cyclin E, being more effectively ubiquitinated and degraded by the 26 S proteasome. A two-step process has emerged that regulates accelerated degradation of Cyclin E, with a caspase-mediated cleavage followed by enhanced proteasome-mediated degradation. We show that recognition of p18-Cyclin E by the Skp1-Cul1-Fbw7 (SCF) complex and its interaction with the Fbw7 protein isoforms can take place independently of phosphorylation of p18-Cyclin E at a C-terminal phosphodegron. In addition to the SCF(Fbw7) pathway, Ku70 binding that facilitates Hdm2 recruitment may also be implicated in p18-Cyclin E ubiquitination. Blocking p18-Cyclin E degradation with proteasome inhibitors increases levels of p18-Cyclin E and enhances its association with Ku70, thus leading to Bax release, its activation, and apoptosis. Moreover, cells expressing p18-Cyclin E are more sensitive to treatment with proteasome inhibitors, such as Bortezomib. By preventing its proteasomal degradation, p18-Cyclin E, but not Cyclin E, may become an effective therapeutic target for Bortezomib and apoptotic effectors in hematopoietic malignancies.     

Structural and functional characterization of the interaction between cyclophilin B and a heparin-derived oligosaccharide

The chemotaxis and integrin-mediated adhesion of T lymphocytes triggered by secreted cyclophilin B (CypB) depend on interactions with both cell surface heparan sulfate proteoglycans (HSPG) and the extracellular domain of the CD147 membrane receptor. Here, we use NMR spectroscopy to characterize the interaction of CypB with heparin-derived oligosaccharides. Chemical shift perturbation experiments allowed the precise definition of the heparan sulfate (HS) binding site of CypB. The N-terminal extremity of CypB, which contains a consensus sequence for heparin-binding proteins was modeled on the basis of our experimental NMR data. Because the HS binding site extends toward the CypB catalytic pocket, we measured its peptidyl-prolyl cis-trans isomerase (PPIase) activity in the absence or presence of a HS oligosaccharide toward a CD147-derived peptide. We report the first direct evidence that CypB is enzymatically active on CD147, as it is able to accelerate the cis/trans isomerization of the Asp(179)-Pro(180) bond in a CD147-derived peptide. However, HS binding has no significant influence on this PPIase activity. We thus conclude that the glycanic moiety of HSPG serves as anchor for CypB at the cell surface, and that the signal could be transduced by CypB via its PPIase activity toward CD147.     

Virtual screening,synthesis and biological evaluation of DNA intercalating antiviral agents

This paper describes computer-aided design of new anti-viral agents against Vaccinia virus (VACV) potentially acting as nucleic acid intercalators. Earlier obtained experimental data for DNA intercalation affinities and activities against Vesicular stomatitis virus (VSV) have been used to build, respectively, pharmacophore and QSAR models. These models were used for virtual screening of a database of 245 molecules generated around typical scaffolds of known DNA intercalators. This resulted in 12 hits which then were synthesized and tested for antiviral activity against VaV together with 43 compounds earlier studied against VSV. Two compounds displaying high antiviral activity against VaV and low cytotoxicity were selected for further antiviral activity investigations.     

Human myometrium – the ultrastructural 3D network of telocytes

Telocytes (TCs), a novel type of interstitial cells, were recently described in the interstitial space of tissues ( www.telocytes.com ). Telocytes TCs have several very long, moniliform extensions, namely telopodes (Tps). However, the functional role(s) of TCs is not yet understood. Successive photomicrographs of ultrathin sections were concatenated to capture the entire length of Tps which usually measure tens to hundreds of micrometres. Besides the podoms (dilations) and podomers (thin segments), ultrastructural features of Tps include the dichotomous branching and establishing homo‐ and heterocellular contacts. Telopodes make a labyrinthine system by 3D convolution and overlapping, their number being roughly estimated at approximately 20 per 1000 μm². Moreover, the presence of extracellular vesicles (shedding vesicles/exosomes) along the Tps suggests an active intercellular signalling (micro‐ and macromolecules), with possible significance in regulating uterine contractility.     

Telocytes of the human adult trigeminal ganglion

Telocytes (TCs) are typically defined as cells with telopodes by their ultrastructural features. Their presence was reported in various organs, however little is known about their presence in human trigeminal ganglion. To address this issue, samples of trigeminal ganglia were tested by immunocytochemistry for CD34 and examined by transmission electron microscopy (TEM). We found that TCs are CD34 positive and form networks within the ganglion in close vicinity to microvessels and nerve fibers around the neuronal–glial units (NGUs). TEM examination confirmed the existence of spindle-shaped and bipolar TCs with one or two telopodes measuring between 15 to 53 μm. We propose that TCs are cells with stemness capacity which might contribute in regeneration and repair processes by: modulation of the stem cell activity or by acting as progenitors of other cells present in the normal tissue. In addition, further studies are needed to establish if they might influence the neuronal circuits.     

Gene expression analysis of in vivo fluorescent cells

Background

The analysis of gene expression for tissue homogenates is of limited value because of the considerable cell heterogeneity in tissues. However, several methods are available to isolate a cell type of interest from a complex tissue, the most reliable one being Laser Microdissection (LMD). Cells may be distinguished by their morphology or by specific antigens, but the obligatory staining often results in RNA degradation. Alternatively, particular cell types can be detected in vivo by expression of fluorescent proteins from cell type-specific promoters.

Methodology/Principal Findings

We developed a technique for fixing in vivo fluorescence in brain cells and isolating them by LMD followed by an optimized RNA isolation procedure. RNA isolated from these cells was of equal quality as from unfixed frozen tissue, with clear 28S and 18S rRNA bands of a mass ratio of ∼2∶1. We confirmed the specificity of the amplified RNA from the microdissected fluorescent cells as well as its usefulness and reproducibility for microarray hybridization and quantitative real-time PCR (qRT-PCR).

Conclusions/Significance

Our technique guarantees the isolation of sufficient high quality RNA obtained from specific cell populations of the brain expressing soluble fluorescent marker, which is a critical prerequisite for subsequent gene expression studies by microarray analysis or qRT-PCR.