Signal Modification Research Articles

Superposition Property of the Ionospheric Scintillation S4 Index

S4 index is the rapid modification of signals when propagating through small-scale structures in the ionosphere, called ionospheric irregularities. The rapid modification of the signal causes the scintillation of the power. The purpose of this letter is to confirm the superposition property of the S4 index by using the ray-tracing method to simulate the signal propagation path through the ionospheric irregularities and then calculate the amplitude and S4 index of the received signal. The relation between the ionospheric scintillation S4 index and the signal propagation path can be understood. Then, the assimilation method for the S4 index can be developed to monitor the ionospheric irregularity in the future.

Comparison Between Contact Force Monitoring and Unipolar Signal Modification as a Guide for Catheter Ablation of Atrial Fibrillation: Prospective Multi-Center Randomized Study.

Both contact force monitoring (CFM) and unipolar signal modification (USM) are guides for ablation, which improve the efficacy of pulmonary vein isolation of atrial fibrillation. We sought to compare the outcomes of atrial fibrillation ablation guided by CFM or USM. A total of 136 patients with paroxysmal atrial fibrillation underwent a circumferential pulmonary vein isolation using CF sensing ablation catheters and were randomly assigned to undergo catheter ablation guided by either CFM (CFM-guided group: n=70) or USM (USM-guided group: n=66). In the USM-guided group, each radiofrequency application lasted until the development of completely positive unipolar electrograms. In the CFM-guided group, a CF of 20 g (range, 10-30 g) and minimum force-time integral of 400 g were the targets for each radiofrequency application. The primary end point was freedom from any atrial tachyarrhythmia recurrence without antiarrhythmic drugs at 12-months of follow-up. The cumulative freedom from recurrences at 12-months was 85% in the USM-guided group and 70% in the CFM-guided group (P=0.031). The incidence of time-dependent and ATP-provoked early electrical reconnections between the left atrium and PVs, procedural time, fluoroscopic time, and average force-time integral, did not significantly differ between the 2 groups. The radiofrequency time for the pulmonary vein isolation was shorter in the USM-guided group than CFM-guided group but was not statistically significant (P=0.077). USM was superior to CFM as an end point for radiofrequency energy deliveries during the pulmonary vein isolation in patients with paroxysmal atrial fibrillation in terms of the 12-month recurrence-free rate. URL: https://www.umin.ac.jp/ctr/index.htm. Unique identifier: UMIN000021127.

Predation and Crypsis in the Evolution of Electric Signaling in Weakly Electric Fishes

Eavesdropping by electroreceptive predators poses a conflict for weakly electric fish, which depend on their Electric Organ Discharge (EOD) signals both for navigation and communication in the dark. The EODs that allow weakly electric fish to electrolocate and communicate in the dark may attract electroreceptive predators such as catfishes and Electric Eels. These predators share with their prey the synapomorphy of passive electric sense supported by ampullary electroreceptors that are highly sensitive to low-frequency electric fields. Any low-frequency spectral components of the EOD make weakly electric fish conspicuous and vulnerable to attack from electroreceptive predators. Accordingly, most weakly electric fish shift spectral energy upwards or cloak low-frequency energy with compensatory masking signals. Subadults and females in particular emit virtually no low-frequency energy in their EODs, whereas courting males include a significant low-frequency component, which likely attracts females, but makes the signals conspicuous to predators. Males of species that coexist with the most predators tend to produce the least low-frequency signal energy, expressing sexual dimorphism in their signals in less risky ways. In these respects, electric signals follow the classic responses to opposing forces of natural and sexual selection, as exemplified in the visual signals of guppies and the acoustic signals of Tungara frogs. Unique to electric fish is that the electric signal modifications that help elude detection by electroreceptive predators are additions to the basal signal rather than losses of attractive components. These enhancements that enable crypsis are energetically costly, but have also provided the evolutionary substrates for subsequent sexual selection and species identity characters.

Identification and functional prediction of lncRNAs in response to PEG and ABA treatment in cassava

LncRNAs play crucial roles in plant drought stress, in which abscisic acid (ABA) was recognized as an essential signal molecule in stress regulatory networks. However, the mechanisms of lncRNAs participated in drought stress with or without the involvement of ABA signaling remain elusive in cassava, an important tropical and sub-tropical crop. In this study, a total of 1379 reliable lncRNAs were identified in cassava leaves using strand-specific RNA-seq method, of which 194 were differentially expressed between ABA or polyethylene glycol (PEG) treatment and the control condition. Trans-regulatory co-expression network revealed that ABA-uniquely-responsive DE lncRNAs were primarily participated in receptor kinases signaling, hormone metabolism, and cell wall modification; PEG-uniquely-responsive DE lncRNAs were mainly involved in jasmonate metabolism, biotic and abiotic stress, calcium signaling, and transport; and ABA/PEG-both-responsive DE lncRNAs were mainly referred to light reaction of photosynthesis, nitrogen metabolism, tetrapyrrole synthesis, secondary metabolism, RNA regulation of transcription, and calcium signaling. In addition, 41 lncRNA-mRNA pairs referred to cis-acting regulation were identified, and these lncRNAs regulated the expression of their neighboring genes through ABA signaling regulation, RNA regulation of transcriptions, and biotic and abiotic stress. Besides, 34 lncRNAs were identified as putative targets of cassava known miRNAs, and especially, TCONS_00129136, TCONS_00122745, TCONS_00088201, and TCONS_00067612 were targeted by functionally well-known miRNAs (such as miR156 and miR159) that involved in ABA- and drought-response, suggesting their roles in cassava drought response via ABA-dependent pathways with the participation of miRNA regulation. These findings provide a comprehensive view of cassava lncRNAs in response to PEG and ABA treatment, which will enable in-depth functional analysis in the near future.

Abstract 4496: Cytokine-induced post-translational modifications of FOXA1 affect enhancer selection and estrogen signaling in breast cancer cells

Abstract The pioneer transcription factor FOXA1 is a critical determinant for estrogen receptor (ER) function in hormone-dependent breast cancers. Upon estrogen stimulation, liganded ER binds to poised enhancer regions across the genome that are demarcated by FOXA1 and histone modifications such as H3K4me1 and H3K27ac. In a recent publication, we show that proinflammatory signaling, caused by the cytokine TNFa, drives FOXA1 to latent enhancer binding sites to promote chromatin accessibility for subsequent ER binding upon estrogen ligation. These latent enhancers, activated by the combined treatment of estrogen and TNFa, induced the expression of a unique transcriptome with clinical significance. The effects of TNFa treatment on FOXA1 chromatin redistribution and subsequent gene expression occur within 40 minutes, which points to a rapid signaling cascade that culminates in either changes in FOXA1's posttranslational modifications (PTMs) or its binding partners. To understand how proinflammatory TNFa signaling can redirect FOXA1 to new sites across the genome, we started by characterizing the posttranslational modifications (PTMs) of FOXA1. We immunoprecipitated FOXA1 from MCF-7 breast cancer cells that were treated by E2, TNFa or E2+ TNFa, and then examined their posttranslational status using semi-quantitative and quantitative mass spectrometry approaches. Several phosphorylation sites and acetylation sites have been identified near the DNA binding domain of FOXA1, and acetylation of lysine 295 (K295) was found specifically enriched in TNFa treatment. To test if acetylation of FOXA1 at K295 changes its binding preference and genomic distribution, we used the programmable properties of CRISPR/Cas9 to create specific knockin mutations to mimic or prevent acetylation of K295 in MCF-7 cells. More specifically, we mutated K295 to glutamine (K295Q) to mimic acetylation and essentially “lock” FOXA1 into a permanently acetylated state and, for comparison, we created another cell line where K295 was mutated to arginine (K295R) to prevent acetylation of FOXA1. Our preliminary data shows changes in the genomic redistribution of FOXA1 in the knock-in cell lines resulting in altered gene expression programs. These data suggest that inflammation-based acetylation of FOXA1 can affect estrogen signaling pathways in breast cancer cells by altering the enhancer landscape of FOXA1 and consequently the estrogen receptor. Supported by a grant from the NIH/NCI (R00 CA204628) to H.L.F Citation Format: Shen Li, Raul Mendez-Giraldez, Joseph P. Garay, Kamila Wisniewska, Colby A. Tubbs, Charles M. Perou, Hector L. Franco. Cytokine-induced post-translational modifications of FOXA1 affect enhancer selection and estrogen signaling in breast cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4496.

Cortical reactive balance responses to unexpected slippages while walking: a pilot study.

Understanding how the human brain cortex behaves when the dynamical balance is unexpectedly challenged can be useful to enable fall prevention strategies during daily activities. In this respect, we designed and tested a novel methodological approach to early detect modifications of the scalp-level signals when steady walking is perturbed. Four young adults were asked to manage unexpected bilateral slippages while steadily walking at their self-selected speed. Lower limb kinematics, electromyographic (EMG) and electroencephalographic (EEG; 13 channels from motor and sensory-motor cortex areas) signals were synchronously recorded. EMG signals from Vastus Medialis (both sides) were used to trigger the analysis of the EEG before and after the perturbation onset. Cortical activity was then assessed and compared pre vs. post perturbation. Specifically, for each gait cycle, the rate of variation of the EEG power spectrum density, named m, was used to describe the cortical responsiveness in five bands of interests: ϑ (4-7 Hz), α (8-12 Hz), β I, β II, β III rhythms (13-15, 15-20, 18-28 Hz). Results revealed a sharp increment of m early after the onset of the perturbation (perturbed step) compared to steady locomotion, for all rhythms. This cortical behavior disappeared during the recovery step. This study promisingly supports the evidence that the proposed approach can distinguish between steady walking and early reactive balance recovery, paving the way for the EEG-based monitoring of the fall risk during daily activities.

Abstract 4742: The influence of cellular developmental state on response to therapeutics in glioblastoma

Abstract Glioblastoma (GBM) is an aggressive tumor treated with ionizing radiation (IR) and temozolomide (TMZ). Here we investigate how developmental state of glioblastoma cells: cancer stem cells (CSC) or differentiated cells, influences cellular response to treatment. Tissue from untreated primary GBM tumors representing diverse genotype were dissociated and cultured in conditions selective for CSCs, which were subsequently differentiated into an astrocytic phenotype by culturing in media supplemented with 2% FBS. Stemness index was evaluated using a machine learning predictive algorithm. Sensitivity of both isogenic CSC and serum differentiated cell (SDC) populations to TMZ and IR was determined by non-linear fitting of dose-response curves, using CellTiterGlo to measure cell viability (n=5) . CSCs and SDCs were then subjected to sub-lethal TMZ, IR (4 Gy), or control treatments, in triplicate. Cells were harvested, and DNA was isolated and Illumina 450k DNA methylation array data was analyzed by using the Methylumi package in R software. RNA was isolated for sequencing, and differentially expressed genes were determined by NOISeq R package. Our results show that GBM CSCs are more vulnerable to both TMZ and IR treatment than the isogenic SDCs. Transcriptome profiling show that IR leads to increase in p53 mediated expression of pro-apoptotic genes such as MDM2, PUMA and BCL2 binding protein relative to control in CSCs. In differentiated cells, IR lead to an increase in WNT signaling, DNA-repair activity and histone modification /remodeling proteins. Enrichment analysis using Fisher’s exact test identified significant enrichment in lipid, fatty acid and metabolic processes as well as receptor tyrosine signaling. Globally, CSCs exhibited a decrease in protein coding genes and increase in regulatory RNA expression. DNA methylation show a global increase in CpG promoter methylation in differentiated cells relative to isogenic stem-like counterparts. We recovered significant differentially methylated probes between treatment groups (Wilcoxon signed rank test) as well as a global increase in CpG promoter methylation in IR treated cells relative to control. These findings underscore the challenge of treating a highly heterogeneous tumor and challenge a strategy of inducing differentiation to increase GBM sensitivity to treatment. Citation Format: Oluwademilade Nuga, Ana deCarvalho, Douglas Ruden, Stephen Brown, Indrani Datta, Tathianne Malta. The influence of cellular developmental state on response to therapeutics in glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4742.

Tetrandrine and cepharanthine induce apoptosis through caspase cascade regulation, cell cycle arrest, MAPK activation and PI3K/Akt/mTOR signal modification in glucocorticoid resistant human leukemia Jurkat T cells

Tetrandrine (TET) and cepharanthine (CEP) are two bisbenzylisoquinoline alkaloids isolated from the traditional herbs. Recent molecular investigations firmly supported that TET or CEP would be a potential candidate for cancer chemotherapy. Prognosis of patients with glucocorticoid resistant T cell acute lymphoblastic leukemia (T-ALL) remains poor; here we examined the anti-T-ALL effects of TET and CEP and the underlying mechanism by using the glucocorticoid resistant human leukemia Jurkat T cell line in vitro. TET and CEP significantly inhibited cell viabilities and induced apoptosis in dose- and time-dependent manner. Further investigations showed that TET or CEP not only upregulated the expression of initiator caspases such as caspase-8 and 9, but also increased the expression of effector caspases such as caspase-3 and 6. As the important markers of apoptosis, p53 and Bax were both upregulated by the treatment of TET and CEP. However, TET and CEP paradoxically increased the expression of anti-apoptotic proteins such as Bcl-2 and Mcl-1, and activated the survival protein NF-κB, leading to high expression of p–NF–κB. Cell cycle arrest at S phase accompanied by increase in the amounts of cyclin A2 and cyclin B1, and decrease in cylcin D1 amount in cells treated with TET or CEP will be another possible mechanism. During the process of apoptosis in Jurkat T cells, treatment with TET or CEP also increased the phosphorylation of JNK and p38. The PI3K/Akt/mTOR signaling pathway modification appears to play significant role in the Jurkat T cell apoptosis induced by TET or CEP. Moreover, TET and CEP seemed to downregulate the expressions of p-PI3K and mTOR in an independent way from Akt, since these two drugs strongly stimulated the p-Akt expression. These results provide fundamental insights into the clinical application of TET or CEP for the treatment of patients with relapsed T-ALL.

Linearisation of RF PA by even-order nonlinear baseband signal processed in digital domain

ABSTRACTThis paper represents, for the first time, the linearisation method of RF power amplifiers, which is based on using the second- and fourth-order nonlinear signals shaped by digital signal processing in a baseband domain. The linearisation signals are generated by the second- and fourth-order nonlinear modifications of the baseband signal in the proposed manners. The composite second- and fourth-order linearisation signals modulate carrier second harmonics, and the modulated signals are then driven to the gate and drain of the amplifier transistor. The linearisation effects of the proposed method are evaluated on a single stage power amplifier for the simulated QAM and OFDM digitally modulated signals at diverse input power levels up to the 1 dB compression point. Moreover, the FPGA implementation of a system for the generation and processing of the fundamental signal, and the second-order linearisation signals is presented in the paper, and the proposed technique is verified for the generated QAM signal. In addition, the linearisation of the two-way asymmetrical Doherty amplifier is performed in the experiment by using software defined radio platforms for synthesising the fundamental signal and the second-order linearisation signals.

Dampening of mast cell secondary responses to allergen involves specific signalling and epigenetic changes

Allergic diseases are increasing worldwide. Allergen and IgE dependent mast cell (MC) activation is the major initiator of these clinical symptoms. During this study, the effect of multiple exposures to the same allergen, on MC degranulation was studied. First, MC recovery in terms of surface expression of high affinity receptor FcεRI, and granule content after a primary allergen challenge was confirmed. Overall, previous exposure of MCs to allergen challenge led to a significant reduction in pre-stored mediator release during the secondary challenge at various time points and with various doses of allergen in vitro. The dampened response was not due to any defects in very early steps in signalling involving FcεRI activation. Inhibition of dampening response during secondary challenge by various inhibitors like wortmannin, tranylcypromine and pargyline, indicated the involvement of PI3K signalling and chromatin modifications. Our study provides insight into new therapeutic avenues for treating allergic disorders targeting MCs.

Reciprocal regulation of TORC signaling and tRNA modifications by Elongator enforces nutrient-dependent cell fate

Nutrient availability has a profound impact on cell fate. Upon nitrogen starvation, wild-type fission yeast cells uncouple cell growth from cell division to generate small, round-shaped cells that are competent for sexual differentiation. The TORC1 (TOR complex 1) and TORC2 complexes exert opposite controls on cell growth and cell differentiation, but little is known about how their activity is coordinated. We show that transfer RNA (tRNA) modifications by Elongator are critical for this regulation by promoting the translation of both key components of TORC2 and repressors of TORC1. We further identified the TORC2 pathway as an activator of Elongator by down-regulating a Gsk3 (glycogen synthase kinase 3)-dependent inhibitory phosphorylation of Elongator. Therefore, a feedback control is operating between TOR complex (TORC) signaling and tRNA modification by Elongator to enforce the advancement of mitosis that precedes cell differentiation.

High-Power (40-50 W) Radiofrequency Ablation Guided by Unipolar Signal Modification for Pulmonary Vein Isolation: Experimental Findings and Clinical Results.

Background Although proposed to facilitate pulmonary vein isolation (PVI), high-power ablation may favor extracardiac damage. Negative component abolition of the unipolar signal reflects lesion transmurality. The present study sought to evaluate the safety and efficacy of high-power ablation using unipolar signal modification as a local end point. Methods High power and standard power were compared in 4 swine and 100 consecutive patients referred for PVI. The first 50 patients were included in the control group (25-30 W) and the last 50 patients in the study group (40-50 W). Atrial radiofrequency applications were stopped 2 s (study group and swine) or 5 s (control group) after unipolar signal modification. Ventricular radiofrequency applications of 500 J (25 W·20 s versus 50 W·10 s) were performed at the swine epicardium. Results Swine gross necropsy did not show any extracardiac damage related to atrial lesions. At equal energy of 500 J, 50 W lesions were deeper (3±0.9 versus 2.6±1.1 mm; P=0.03) and wider (6.2±2 versus 5±2.3 mm; P=0.006) than 25 W lesions. No complications occurred during the clinical study, whatever the power output used for PVI. For a similar sinus rhythm maintenance at 12 months (90% versus 88%; P=0.75), the study group displayed higher first-pass PVI (92% versus 73%; P<0.001), lower acute pulmonary vein reconnection (2% versus 17%; P<0.001), reduced procedure time (73.1±18.2 versus 107.4±21.2 min; P<0.001), and ablation time (13±2.9 versus 30.3±8.8 min; P<0.001). Conclusions High-power PVI guided by unipolar signal modification safely decreases procedural burden while ensuring robust 12-month outcomes.

Is Experimental Evolution of an Increased Aerobic Exercise Performance in Bank Voles Mediated by Endocannabinoid Signaling Pathway?

The level of physical activity achieved in a given situation depends on both physiological abilities and behavioral characteristics (motivation). We used a unique animal model to test a hypothesis that evolution of an increased aerobic exercise performance can be facilitated by evolution of motivation to undertake physical activity, mediated by brain endocannabinoid system. Bank voles (Myodes glareolus) from “aerobic” A lines selected for 22 generations for high swim-induced aerobic metabolism (VO2swim) achieved 65% higher “voluntary maximum” VO2swim than voles from unselected, “control” C lines. In C lines, VO2swim was 24% lower than the maximum forced-running aerobic metabolism (VO2run), while in A lines VO2swim and VO2run were practically the same. Thus, the selection changed both the aerobic capacity and motivation to exercise at the top performance level. We applied a pharmacological treatment manipulation to test a hypothesis that the endocannabinoid signaling pathway 1) affects the voles performance in the aerobic exercise trials, and 2) has been modified in the selection process. Administration of the CB1 receptor antagonist (Rimonabant) did not affect the level of metabolism, but administration of the endocannabinoid reuptake inhibitor (AM404) decreased VO2swim both in A and C lines (4%, p = 0.03) and tended to decrease VO2run (2%, p = 0.07). The significant effect of AM404 suggests the involvement of endocannabinoids in signaling pathways controlling the motivation to be active. However, the response to AM404 did not differ between A and C lines (interaction effect, p ≥ 0.29). Thus, the results did not provide a support to the hypothesis that modifications of endocannabinoid signaling have played a role in the evolution of increased aerobic exercise performance in our experimental evolution model system.Summary StatementThe results corroborated involvement of endocannabinoids in the regulation of physical activity, but did not support the hypothesis that modification of endocannabinoid signaling played a role in the evolution of increased aerobic exercise performance in our experimental evolution model.

Clathrin Heavy Chain Knockdown Impacts CXCR4 Signaling and Post-translational Modification.

Recent research has implicated endocytic pathways as important regulators of receptor signaling. However, the role of endocytosis in regulating chemokine CXC receptor 4 (CXCR4) signaling remains largely unknown. In the present work we systematically investigate the impact of clathrin knockdown on CXCR4 internalization, signaling, and receptor post-translational modification. Inhibition of clathrin-mediated endocytosis (CME) significantly reduced CXCR4 internalization. In contrast to other receptors, clathrin knockdown increased CXCL12-dependent ERK1/2 signaling. Simultaneous inhibition of CME and lipid raft disruption abrogated this increase in ERK1/2 phosphorylation suggesting that endocytic pathway compensation can influence signaling outcomes. Interestingly, using an antibody sensitive to CXCR4 post-translational modification, we also found that our ability to detect CXCR4 was drastically reduced upon clathrin knockdown. We hypothesize that this effect was due to differences in receptor post-translational modification as total CXCR4 protein and mRNA levels were unchanged. Lastly, we show that clathrin knockdown reduced CXCL12-dependent cell migration irrespective of an observed increase in ERK1/2 phosphorylation. Altogether, this work supports a complex model by which modulation of endocytosis affects not only receptor signaling and internalization but also receptor post-translational modification.

Meta-analysis of drought-tolerant genotypes in Oryza sativa: A network-based approach.

BackgroundDrought is a severe environmental stress. It is estimated that about 50% of the world rice production is affected mainly by drought. Apart from conventional breeding strategies to develop drought-tolerant crops, innovative computational approaches may provide insights into the underlying molecular mechanisms of stress response and identify drought-responsive markers. Here we propose a network-based computational approach involving a meta-analytic study of seven drought-tolerant rice genotypes under drought stress.ResultsCo-expression networks enable large-scale analysis of gene-pair associations and tightly coupled clusters that may represent coordinated biological processes. Considering differentially expressed genes in the co-expressed modules and supplementing external information such as resistance/tolerance QTLs, transcription factors, network-based topological measures, we identify and prioritize drought-adaptive co-expressed gene modules and potential candidate genes. Using the candidate genes that are well-represented across the datasets as ‘seed’ genes, two drought-specific protein-protein interaction networks (PPINs) are constructed with up- and down-regulated genes. Cluster analysis of the up-regulated PPIN revealed ABA signalling pathway as a central process in drought response with a probable crosstalk with energy metabolic processes. Tightly coupled gene clusters representing up-regulation of core cellular respiratory processes and enhanced degradation of branched chain amino acids and cell wall metabolism are identified. Cluster analysis of down-regulated PPIN provides a snapshot of major processes associated with photosynthesis, growth, development and protein synthesis, most of which are shut down during drought. Differential regulation of phytohormones, e.g., jasmonic acid, cell wall metabolism, signalling and posttranslational modifications associated with biotic stress are elucidated. Functional characterization of topologically important, drought-responsive uncharacterized genes that may play a role in important processes such as ABA signalling, calcium signalling, photosynthesis and cell wall metabolism is discussed. Further transgenic studies on these genes may help in elucidating their biological role under stress conditions.ConclusionCurrently, a large number of resources for rice functional genomics exist which are mostly underutilized by the scientific community. In this study, a computational approach integrating information from various resources such as gene co-expression networks, protein-protein interactions and pathway-level information is proposed to provide a systems-level view of complex drought-responsive processes across the drought-tolerant genotypes.

First person – Alessandro A. Bailetti

ABSTRACTFirst Person is a series of interviews with the first authors of a selection of papers published in Disease Models & Mechanisms (DMM), helping early-career researchers promote themselves alongside their papers. Alessandro Bailetti is first author on ‘Enhancer of polycomb/Tip60 represses hematological tumor initiation by negatively regulating JAK/STAT pathway activity’, published in DMM. Alessandro conducted the research described in this article while a graduate assistant in Dr Erika A. Bach's lab at New York University (NYU) School of Medicine, New York, USA. He is now a postdoctoral fellow in the lab of Dr Anthony Oro at Program in Epithelial Biology, Department of Dermatology, Stanford University, Stanford, USA, investigating development, genetics, genomics, cell signaling, gene transcription and chromatin modification.

Generation of a nitric oxide signaling pathway in mesenchymal stem cells promotes endothelial lineage commitment.

Enhancing differentiation of mesenchymal stem cells (MSCs) to endothelial cells may improve their ability to vascularize tissue and promote wound healing. This study describes a novel role for nitric oxide (NO) in reprogramming MSCs towards an endothelial lineage and highlights the role of Wnt signaling and epigenetic modification by NO. Rat MSCs were transduced with lentiviral vectors expressing endothelial nitric oxide synthase (pLV-eNOS) and a mutated caveolin gene (pLV-CAV-1F92A ) to enhance NO generation resulting in increased in vitro capillary tubule formation and endothelial marker gene expression. An exogenous source of NO could also stimulate CD31 expression in MSCs. NO was associated with an arterial-specific endothelial gene expression profile of Notch1, Dll4, and Hey2 and significantly reduced expression of venous markers. Wnt signaling associated with NO was evident through increased gene expression of Wnt3a and β-catenin protein, and expression of the endothelial marker Pecam-1 could be significantly reduced by treatment with the Wnt signaling inhibitor Dkk-1. The role of NO as an epigenetic modifier was evident with reduced gene expression of the methyltransferase, DNMT1, and bisulfite sequencing of the endothelial Flt1 promoter region in NO-producing MSCs showed significant demethylation compared to control cells. Finally, subcutaneous implantation of NO-producing MSCs seeded in a biomaterial scaffold (NovoSorb®) resulted in survival of transplanted cells and the formation of blood vessels. In summary, this study describes, NO as a potent endothelial programming factor which acts as an epigenetic modifier in MSCs and may provide a novel platform for vascular regenerative therapy.

Pathological mechanisms and therapeutic outlooks for arthrofibrosis

Arthrofibrosis is a fibrotic joint disorder that begins with an inflammatory reaction to insults such as injury, surgery and infection. Excessive extracellular matrix and adhesions contract pouches, bursae and tendons, cause pain and prevent a normal range of joint motion, with devastating consequences for patient quality of life. Arthrofibrosis affects people of all ages, with published rates varying. The risk factors and best management strategies are largely unknown due to a poor understanding of the pathology and lack of diagnostic biomarkers. However, current research into the pathogenesis of fibrosis in organs now informs the understanding of arthrofibrosis. The process begins when stress signals stimulate immune cells. The resulting cascade of cytokines and mediators drives fibroblasts to differentiate into myofibroblasts, which secrete fibrillar collagens and transforming growth factor-β (TGF-β). Positive feedback networks then dysregulate processes that normally terminate healing processes. We propose two subtypes of arthrofibrosis occur: active arthrofibrosis and residual arthrofibrosis. In the latter the fibrogenic processes have resolved but the joint remains stiff. The best therapeutic approach for each subtype may differ significantly. Treatment typically involves surgery, however, a pharmacological approach to correct dysregulated cell signalling could be more effective. Recent research shows that myofibroblasts are capable of reversing differentiation, and understanding the mechanisms of pathogenesis and resolution will be essential for the development of cell-based treatments. Therapies with significant promise are currently available, with more in development, including those that inhibit TGF-β signalling and epigenetic modifications. This review focuses on pathogenesis of sterile arthrofibrosis and therapeutic treatments.

Protein Kinase C: Targets to Regenerate Brain Injuries?

Acute or chronic injury to the central nervous system (CNS), causes neuronal death and irreversible cognitive deficits or sensory-motor alteration. Despite the capacity of the adult CNS to generate new neurons from neural stem cells (NSC), neuronal replacement following an injury is a restricted process, which does not naturally result in functional regeneration. Therefore, potentiating endogenous neurogenesis is one of the strategies that are currently being under study to regenerate damaged brain tissue. The insignificant neurogenesis that occurs in CNS injuries is a consequence of the gliogenic/non-neurogenic environment that inflammatory signaling molecules create within the injured area. The modification of the extracellular signals to generate a neurogenic environment would facilitate neuronal replacement. However, in order to generate this environment, it is necessary to unearth which molecules promote or impair neurogenesis to introduce the first and/or eliminate the latter. Specific isozymes of the protein kinase C (PKC) family differentially contribute to generate a gliogenic or neurogenic environment in injuries by regulating the ADAM17 mediated release of growth factor receptor ligands. Recent reports describe several non-tumorigenic diterpenes isolated from plants of the Euphorbia genus, which specifically modulate the activity of PKC isozymes promoting neurogenesis. Diterpenes with 12-deoxyphorbol or lathyrane skeleton, increase NPC proliferation in neurogenic niches in the adult mouse brain in a PKCβ dependent manner exerting their effects on transit amplifying cells, whereas PKC inhibition in injuries promotes neurogenesis. Thus, compounds that balance PKC activity in injuries might be of use in the development of new drugs and therapeutic strategies to regenerate brain injuries.

Bioactive glass granules for mastoid and epitympanic surgical obliteration: CT and MRI appearance.

To evaluate the appearance of mastoid and epitympanic obliteration using S53P4 bioactive glass (BG) granules in high-resolution computed tomography (HRCT) and MRI. Patients undergoing mastoid and epitympanic obliteration between May 2013 and December 2015 were prospectively included in an uncontrolled clinical study. All patients underwent a temporal HRCT scan 1year after surgery, aimed at evaluating the attenuation, homogeneity, and osseointegration of the BG granules, as well as the ventilation of the middle ear and the volume of the obliterated paratympanic spaces. If a cholesteatoma was found during surgery, additional MRI, including at least pre- and post-contrast T1-weighted, T2-weighted, and axial non-echo-planar diffusion-weighted (DW) sequences, was performed 1year after surgery, to study the normal signal of the BG granules and the presence of residual cholesteatoma and/or other temporal bone pathologies. Seventy cases were included. On 1-year HRCT, the mean attenuation of the BG granules was 888.34 ± 166.10HU. The obliteration was found to be mostly homogeneous with partial osseointegration. The appearance of the BG granules having a low-intensity signal in T2-weighted imaging and DW MRI was always different from the appearance of cholesteatoma. A longer follow-up has shown no attenuation or signal modification of the BG granules compared with the 1-year imaging. Radiological follow-up of patients operated on with mastoid and epitympanic obliteration using BG granules is effective using both HRCT and MRI. A cholesteatoma and/or other potential complications could easily be detected due to the specific radiological appearance of the BG granules. • The appearance of mastoid and epitympanic obliteration by S53P4 bioactive glass (BG) granules on high-resolution computed tomography (HRCT) scans was homogeneous with an attenuation significantly higher than the attenuation of cholesteatoma and lower than mastoid bone attenuation. • The granules have a low-intensity signal on non-echo-planar diffusion-weighted sequences and on T2-weighted images and present contrast enhancement allowing the differential diagnosis with cholesteatoma and effective for the detection of other underlying temporal bone pathologies. • The volume and radiological appearance of the obliteration appear to be stable with time.