Contractile Fibers Research Articles

Investigation on the differentially expressed circular RNAs in myocardium of mice with diabetic cardiomyopathy

Objective: To identify the differentially expressed circular RNA (circRNA) in the myocardium of diabetic cardiomyopathy (DCM) mice, and analyze their possible biological functions and related regulatory network. Methods: C57BL/6 mice, aged 8 weeks, and weighing were 21-27 g. Eight mice were selected as the control group and 15 mice were selected as the experimental group. The diabetic mice model was established by intraperitoneal injection of streptozotocin in the experimental group. One week after injection, the fasting blood glucose level of mice was measured, and 12 diabetic mice were included in the final experimental group. All mice were fed for 12 weeks under the same laboratory conditions. The cardiac structure and function were detected by echocardiography. Diabetic mice with the left ventricular ejection fraction less than 60% and the E/A less than 1.6 were selected as DCM group (n=3). Mice in DCM group and control group were then sacrificed under deep anesthesia. RNA was extracted from myocardial tissue. High-throughput RNA sequencing technology was used to sequence and identify the RNA in the myocardial tissue of DCM group and normal control group, and the difference was analyzed by DeSeq2. The analysis results were verified at the tissue level by RT-qPCR, and the differential circRNA were analyzed by GO and KEGG pathway analysis. The differentially expressed circRNA-microRNA(miRNA) interaction was predicted by the miRNA target gene prediction software. Results: A total of 63 differentially expressed circRNAs were found in the myocardium of DCM mice. The results of RT-qPCR showed that the tissue level expression of 8 differentially expressed circRNAs was consistent with the sequencing results, of which 7 were up-regulated and 1 was down-regulated. KEGG pathway analysis showed that the up-regulated circRNAs was mainly related to AMPK signal pathway and intercellular adhesion junction pathway, and the down-regulated circRNA was mainly related to cardiomyopathy. Go analysis showed that the up-regulated circRNA was mainly related to the binding process of ions, proteins, kinases and other factors in terms of molecular function, and was involved in regulating the intracellular structure, especially the composition of organelles in terms of cell components. The functional analysis of molecular function and cell components showed that the up-regulated circRNA were related to the cell component origin, recruitment and tissue, and thus participated in the regulation of cell biological process. The down regulated circRNA was related to catalytic activity in terms of molecular function, protein kinase binding process, transferase and calmodulin activity, and was closely related to the components of contractile fibers and the composition of myofibrils. These differentially expressed circRNAs were also related to biological processes such as lysine peptide modification, sarcomere composition, myofibril assembly, morphological development of myocardial tissue, myocardial hypertrophy and so on. Conclusions: In this study, we detected the novel differentially expressed circRNAs in the myocardium of DCM mice, and bioinformatics analysis confirmed that these circRNAs are related to oxidative stress, fibrosis and death of cardiomyocytes, and finally participate in the pathophysiological process of DCM.

2021 winner: Lee Dolat

We are pleased to announce that the winner of the 2021 JCS Prize is Lee Dolat for his paper entitled ‘An endometrial organoid model of interactions between Chlamydia and epithelial and immune cells’ (Dolat and Valdivia, 2021).The prize of £1000 is awarded annually to the first author of the paper that is judged by the Editors to be the best eligible paper published in the Journal of Cell Science that year. To be considered for the prize, the first author must be a student or a postdoc of no more than five years standing.Lee grew up in Ledyard, Connecticut, and received his undergraduate degree from the University of Connecticut. After graduation, he worked as a research technician at 454 Life Sciences, a small biotech that was an early developer of next-generation DNA sequencing. He then moved to Boston, MA, where he worked as a research technician at Massachusetts General Hospital under the guidance of Dr Mason Freeman and Dr Michael Fitzgerald. Using stratified epidermal keratinocyte organotypic culture systems, he studied the role of the lipid transporter ABCA12 in epidermal lipid homeostasis and barrier function.For his graduate studies at Drexel University in Philadelphia, PA, Lee joined the laboratory of Dr Elias Spiliotis, whose research focuses on the cell biology of septins, filamentous GTPases that regulate the organization and dynamics of actin, microtubules and cell membranes. In his thesis work, he identified that septins directly bind and bundle actin filaments to regulate the assembly of a contractile stress fiber network, focal adhesion assembly and epithelial cell motility (Dolat et al., 2014; Smith et al., 2015). In a second study, he uncovered a role for septins in macropinocytosis, during which they assemble at contact sites between macropinosomes and endolysosomes in a phosphatidylinositol-specific manner to promote membrane fusion (Dolat and Spiliotis, 2016).Septins were shown by others to participate in cell autonomous immunity to intracellular pathogens, which inspired Lee to undertake a post-doc in the field of host–pathogen interactions. He then joined the laboratory of Dr Raphael Valdivia – an expert in the molecular genetics and cell biology of Chlamydia trachomatis infections at Duke University, Durham, North Carolina, USA. Chlamydia are obligate intracellular pathogens that employ an arsenal of secreted effector proteins to enter host epithelial cells and replicate within a membrane-bound vacuole, termed the inclusion. Owing to its unique intracellular lifecycle, however, Chlamydia has, until the past decade or so, been difficult to genetically manipulate.His research now leverages new techniques to genetically modify Chlamydia, and polarized 2D and 3D epithelial infection models to identify how Chlamydia effector proteins reprogramme epithelial organization, cytoskeletal function and innate immune responses (Dolat and Valdivia, 2021).

Oxidative Stress and Left Ventricular Performance in Patients with Different Glycometabolic Phenotypes.

The aim of the present study was to evaluate the possible correlation between oxidative stress and subclinical myocardial damage, assessed with speckle tracking echocardiography (STE), in normal glucose tolerance (NGT) patients with one-hour plasma glucose values ≥ 155 mg/dL (NGT ≥ 155), comparing them to NGT < 155 subjects, impaired glucose tolerance (IGT) and type 2 diabetes mellitus (T2DM) newly diagnosed patients. We enrolled 100 Caucasian patients. All subjects underwent OGTT. The serum values of oxidative stress markers (8-isoprostane and Nox-2) were assessed with an ELISA test. Echocardiographic recordings were performed using an E-95 Pro ultrasound system. We observed significant differences, among the four groups, for fasting plasma glucose (p < 0.0001), one-hour postload (p < 0.0001), and two-hour postload plasma glucose (p < 0.0001). As compared with NGT < 155, NGT ≥ 155 exhibited significantly worse insulin sensitivity and higher values of hs-CRP. No significant differences were observed between NGT ≥ 155 and IGT patients. There was a significant increase in 8-isoprostane (p < 0.0001) and Nox-2 (p < 0.0001), from the first to fourth group, indicating an increase in oxidative stress with the worsening of the metabolic status. Serum levels of 8-isoprostane and Nox-2 were significantly increased in NGT ≥ 155 compared to the NGT < 155 group, but similar to IGT. The global longitudinal strain (GLS) appeared progressively lower proceeding from the NGT < 155 to T2DM group (p < 0.0001). For similar values of left ventricular ejection fraction (LVEF), NGT ≥ 155 exhibited reduced GLS compared to NGT < 155 (p = 0.001), but similar to IGT patients. Our study demonstrated that NGT ≥ 155 subjects exhibit early functional impairment of myocardial contractile fibres, these alterations are correlated with increased oxidative stress.

Automated Biomedical Signal Quality Assessment of Electromyograms: Current Challenges and Future Prospects

This work is an exposition of research supporting efforts to automate quality assessment in surface electromyography (sEMG). Electromyography measures electrical activity from skeletal muscles, which are the muscles associated with voluntary movements. Skeletal muscles can consist of tens to hundreds of thousands of contractile fibers which are grouped into functional units called Motor Units (MUs). Each MU is driven to contract its fibers by electrochemical impulses sent from a motor neuron, and a muscle may contain anywhere from tens to hundreds of MUs. When an MU is activated, all fibers associated with it are simultaneously activated. When fibers are activated, an electrochemical impulse propagates along each of them to cause contraction. This impulse is known as a Single Fiber Action Potential (SFAP). A Motor Unit Action Potential (MUAP) is the summation of all SFAPs corresponding to an activated MU. To generate a continuous contraction, MUs are repeatedly activated, producing a train of MUAPs, and this pulse train is called the Motor Unit Action Potential Train (MUAPT). The combined electrical activity of all of the MUAPTs associated with a contraction, as recorded on the surface of the skin using non-invasive electrodes, is a surface electromyography (sEMG) signal. In general, it is not possible to directly observe the SFAPs, MUAPs, and MUAPTs non-invasively (though there have been algorithmic efforts to decompose sEMG signals into its constituent MUAPTs). SFAPs and MUAPTs can be observed by inserting needle electrodes into specific muscle regions for high spatial selectivity; however, such techniques are invasive, making surface measurements a desirable alternative. sEMG signals have been used in a wide variety of applications, including fatigue assessment, myoelectric control, diagnosis of neuromuscular disorders, and tracking performance in sports.

Identification of Hub Genes Associated with Progression and Prognosis of Bladder Cancer by Integrated Bioinformatics Analysis.

Bladder cancer (BLCA) is an extremely common carcinoma of the urinary system that has a high incidence of relapse. Although intensive studies have investigated its pathology in the past decades, there are significant knowledge gaps regarding the characterization of the molecular processes underlying the progression of disease and consequently its prognosis. The purpose of current research was to identify significant genes that could serve as prognostic and progression biomarkers. Gene expression profiles were downloaded from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) database. Differential gene expression analysis (DGEA) and weighted gene co-expression network analysis (WGCNA) were conducted to recognize differential co-expression genes. Gene Ontology (GO) enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed to explore gene function. Moreover, protein-protein interactions (PPI) network, overall survival (OS) and disease-free survival (DFS) were used to identify survival-related hub genes. Additionally, associations between these gene's expression and clinical parameters were determined. Finally, the Human Protein Atlas (HPA) database and qRT-PCR were used to validate gene's expression. About 124 differential co-expression genes were identified. These genes were mainly enriched in muscle system process and muscle contraction (biological process, BP), contractile fiber, myofibril, sarcomere, focal adhesion and cell-substrate junction (cellular component, CC) and actin binding (molecular function, MF) in GO enrichment analysis, while enriched in vascular smooth muscle contraction, focal adhesion, cardiac muscle contraction, hypertrophic cardiomyopathy, dilated cardiomyopathy and regulation of actin cytoskeleton in KEGG analysis. Furthermore, five survival-related hub genes (MYH11, ACTA2, CALD1, TPM1, MYLK) were identified via OS and DFS. In addition, these survival-related gene's expression was correlated with grade, stage and TNM stage. Finally, all survival-related hub genes were determined to be down-regulated in BLCA tissues by qRT-PCR and HPA databases. Our current study verified five new key genes in BLCA, which may participate in the prognosis and progression and serve as novel biomarkers of BLCA.

Cardiac ischemia on-a-chip to investigate cellular and molecular response of myocardial tissue under hypoxia

Tissue engineering has enabled the development of advanced and physiologically relevant models of cardiovascular diseases, with advantages over conventional 2D in vitro assays. We have previously demonstrated development of a heart on-a-chip microfluidic model with mature 3D anisotropic tissue formation that incorporates both stem cell-derived cardiomyocytes and cardiac fibroblasts within a collagen-based hydrogel. Using this platform, we herein present a model of myocardial ischemia on-a-chip, that recapitulates ischemic insult through exposure of mature 3D cardiac tissues to hypoxic environments. We report extensive validation and molecular-level analyses of the model in its ability to recapitulate myocardial ischemia in response to hypoxia, demonstrating the 1) induction of tissue fibrosis through upregulation of contractile fibers, 2) dysregulation in tissue contraction through functional assessment, 3) upregulation of hypoxia-response genes and downregulation of contractile-specific genes through targeted qPCR, and 4) transcriptomic pathway regulation of hypoxic tissues. Further, we investigated the complex response of ischemic myocardial tissues to reperfusion, identifying 5) cell toxicity, 6) sustained contractile irregularities, as well as 7) re-establishment of lactate levels and 8) gene expression, in hypoxic tissues in response to ischemia reperfusion injury.

Screening and Identification of Muscle-Specific Candidate Genes via Mouse Microarray Data Analysis.

Muscle tissue is involved with every stage of life activities and has roles in biological processes. For example, the blood circulation system needs the heart muscle to transport blood to all parts, and the movement cannot be separated from the participation of skeletal muscle. However, the process of muscle development and the regulatory mechanisms of muscle development are not clear at present. In this study, we used bioinformatics techniques to identify differentially expressed genes specifically expressed in multiple muscle tissues of mice as potential candidate genes for studying the regulatory mechanisms of muscle development. Mouse tissue microarray data from 18 tissue samples was selected from the GEO database for analysis. Muscle tissue as the treatment group, and the other 17 tissues as the control group. Genes expressed in the muscle tissue were different to those in the other 17 tissues and identified 272 differential genes with highly specific expression in muscle tissue, including 260 up-regulated genes and 12 down regulated genes. is the genes were associated with the myofibril, contractile fibers, and sarcomere, cytoskeletal protein binding, and actin binding. KEGG pathway analysis showed that the differentially expressed genes in muscle tissue were mainly concentrated in pathways for AMPK signaling, cGMP PKG signaling calcium signaling, glycolysis, and, arginine and proline metabolism. A PPI protein interaction network was constructed for the selected differential genes, and the MCODE module used for modular analysis. Five modules with Score > 3.0 are selected. Then the Cytoscape software was used to analyze the tissue specificity of differential genes, and the genes with high degree scores collected, and some common genes selected for quantitative PCR verification. The conclusion is that we have screened the differentially expressed gene set specific to mouse muscle to provide potential candidate genes for the study of the important mechanisms of muscle development.

498 Oxidative stress and left ventricular performance in patients according to different glycometabolic phenotypes

Abstract Recent studies demonstrated that in normoglucose-tolerant subjects (NGT), 1-h post load plasma glucose value ≥155 mg/dL, during OGTT, identifies a worse cardio-metabolic risk profile with increased risk for Type 2 Diabetes Mellitus (T2DM). T2DM patients present increased oxidative stress, due to high blood glucose levels, which plays a central role in the development of CV events. The aim of our study was to evaluate the correlation between oxidative stress and subclinical myocardial damage, assessed with speckle tracking echocardiography, in NGT patients with 1-h post load ≥155 mg/dL vs. NGT &amp;lt; 155 subjects, impaired glucose tolerance (IGT) and T2DM patients. We enrolled 100 Caucasian patients (61 M, 39 W, mean age 61.4 ± 10.7) afferent to CATAMERI study. Main exclusion criteria were CV complications, history of malignant or chronic respiratory disease, alcohol, drug influencing glucose metabolism or smoking abuse. All subjects underwent clinical and laboratory evaluation, OGTT and HOMA-IR. The serum values of the markers of oxidative stress (8-isoprostane and NOX-2) were assessed with ELISA sandwich. Statistical analysis was performed with ANOVA test, linear correlation analysis and stepwise multivariate linear regression model. According to OGTT results, subjects were divided into 4 groups: NGT &amp;lt; 155 (n = 30), NGT ≥ 155 (n = 24), IGT (n = 28), T2DM (n = 18). Serum levels of 8-isoprostane and NOX-2 were significantly increased (P &amp;lt; 0.0001) in NGT ≥ 155 compared to NGT &amp;lt; 155 group, but similar with IGT, indicating an increase in oxidative stress with the worsening of the metabolic status. The left global systolic function, evaluated as myocardial deformation and global longitudinal strain (GLS), appeared progressively lower proceeding from the NGT &amp;lt; 155 group to the T2DM group (P &amp;lt; 0.0001). Moreover, for similar values of ejection fraction (EF), NGT ≥ 155 subjects presented reduced GLS compared to NGT &amp;lt; 155 (P = 0.001), but similar to IGT patients. The linear correlation analysis showed that endo/epi ratio was significantly and inversely correlated with 1 h post load glycaemia (r = −0.632, P &amp;lt; 0.0001), NOX-2 (r = −0.638, P &amp;lt; 0.0001), 8-isoprostane (r = −0.508, P &amp;lt; 0.0001); GLS was inversely correlated with 1 h post load glycaemia (r = −0.734, P &amp;lt; 0.0001) and directly and significantly correlated with 8-isoprostane (r = 0.564, P &amp;lt; 0.0001), NOX-2 (r = 0.625, P &amp;lt; 0.0001). From stepwise multivariate linear regression model, NOX-2 resulted the major predictor of endo/epi ratio, justifying 40.7% of its variation. 1-h post load glycaemia was the second predictor of endo/epi ratio justifying another 9.2% of its variation. Similarly 1-h post load glycaemia was the strongest predictor of the GLS, explaining 53.9% of its variation. Our study demonstrated that NGT ≥ 155 subjects present functional alterations of myocardial contractile fibres, compared to NGT &amp;lt; 155 subjects, but similar to IGT, and these alterations are correlated with oxidative stress. Moreover, GLS is able to identify early alterations in the contractility of subendocardial longitudinal fibres long before the alteration of EF. This data have a central role in ongoing research on the association between hyperglycaemia at 1-h post load and CV risk.

Abstract 11091: Failure of Right Ventricular Adaptation to Pressure Overload Due to a Profound Deficiency in Adenylate Kinase 1 and Impaired Ventricular Energetics

Introduction: Interindividual heterogeneity in the ability of the right ventricular (RV) to adapt to pressure overload in pulmonary hypertension (PH) is likely influenced by genetic determinants. We took advantage of strain-dependent, maladaptive RV remodeling in Fischer compared to Sprague-Dawley (SD) rats to define the molecular and genetic mechanisms that predispose to development of RV failure in PH. Methods/Results: In the SU5416/hypoxia(SUHx) PH model, Fischer rats exhibited RV failure and 100% mortality by 5-weeks, whereas SD rats showed preserved RV function and 88% survival beyond 9 weeks (p&lt;0.0001). In vivo oxidative metabolism, assessed by [ 11 C]acetate PET, was increased in Fischer rats at 4 weeks (p&lt;0.05), associated with impaired RV efficiency compared to SD (work metabolic index: 58±12 vs 102±20 mmHg·mL/cm 2 , respectively; p&lt;0.001), but no differences were observed in mitochondrial complex activity in permeabilized RV cardiac fibers. Adenylate Kinase 1 (AK1) was among the top ten differentially expressed genes between Fischer and SD rats by unbiased transcriptomic analysis, with markedly lower expression in the RV of Fischer rats (FC:3.36, P&lt;0.05). Profound AK1 deficiency was confirmed by proteomics and validated by Western blotting (&gt;10-fold reduction, P&lt;0.001). Fischer rats also exhibited evidence of hemolysis, recapitulating the hemolytic phenotype seen in patients with rare AK1 coding region mutations. While whole genome sequencing failed to reveal any coding region mutations in Fischer rats, there was a unique variant in a highly conserved upstream flanking region. AK1 levels were also reduced in the RV of PH patients with decompensated RV function and right heart failure. Conclusion: Fischer rats with AK1 deficiency have inefficient energetics likely related to reduced ATP shuttling from the mitochondria to the contractile fibers, which represents a novel mechanism for RV failure in response to chronic increases in afterload.

Transcriptome profiling of lncRNA and co-expression network in the vaginal epithelial tissue of women with lubrication disorders.

BackgroundVaginal lubrication is a crucial physiological response that occurs at the beginning of sexual arousal. However, research on lubrication disorders (LD) is still in its infancy, and the role of long non-coding RNAs (lncRNAs) in LD remains unclear. This study aimed to explore the function of lncRNAs in the pathogenesis of vaginal LD.MethodsThe expression profiles of LD and normal control (NC) lncRNAs were examined using next-generation sequencing (NGS), and eight selected differentially expressed lncRNAs were verified by quantitative real-time PCR. We conducted GO annotation and KEGG pathway enrichment analyses to determine the principal functions of significantly deregulated genes. LncRNA-mRNA co-expression and protein-protein interaction (PPI) networks were constructed and the lncRNA transcription factors (TFs) were predicted.ResultsFrom the results, we identified 181,631 lncRNAs and 145,224 mRNAs in vaginal epithelial tissue. Subsequently, our preliminary judgment revealed a total of 499 up-regulated and 337 down-regulated lncRNAs in LD. The top three enriched GO items of the dysregulated lncRNAs included the following significant terms: “contractile fiber part,” “actin filament-based process,” and “contractile fiber”. The most enriched pathways were “cell-extracellular matrix interactions,” “muscle contraction,” “cell-cell communication,” and “cGMP-PKG signaling pathway”. Our results also showed that the lncRNA-mRNA co-expression network was a powerful platform for predicting lncRNA functions. We determined the three hub genes, ADCY5, CXCL12, and NMU, using PPI network construction and analysis. A total of 231 TFs were predicted with RHOXF1, SNAI2, ZNF354C and TBX15 were suspected to be involved in the mechanism of LD.ConclusionIn this study, we constructed the lncRNA-mRNA co-expression network, predicted the lncRNA TFs, and comprehensively analyzed lncRNA expression profiles in LD, providing a basis for future studies on LD clinical biomarkers and therapeutic targets. Further research is also needed to fully determine lncRNA’s role in LD development.

Shear flow of active matter in thin channels.

We study the shear flow of active filaments confined in a thin channel for extensile and contractile fibers. We apply the Ericksen-Leslie equations of liquid crystal flow with an activity source term. The dimensionless form of this system includes the Ericksen, activity, and Reynolds numbers, together with the aspect ratio of the channel, as the main driving parameters. We perform a normal mode stability analysis of the base shear flow. For both types of fibers, we arrive at a comprehensive description of the stability properties and their dependence on the parameters of the system. The transition to unstable frequencies in extensile fibers occurs at a positive threshold value of the activity parameter, whereas for contractile ones a complex behavior is found at low absolute value of the activity number. The latter might be an indication of the biologically relevant plasticity and phase transition issues. In contrast with extensile fibers, flows of contractile ones are also found to be highly sensitive to the Reynolds number. The work on extensile fibers is guided by experiments on active filaments in confined channels and aims at quantifying their findings in the prechaotic regime.

WNT/β-Catenin Signaling Promotes TGF-β-Mediated Activation of Human Cardiac Fibroblasts by Enhancing IL-11 Production.

Cardiac fibrosis is a pathological process associated with the development of heart failure. TGF-β and WNT signaling have been implicated in pathogenesis of cardiac fibrosis, however, little is known about molecular cross-talk between these two pathways. The aim of this study was to examine the effect of exogenous canonical WNT3a and non-canonical WNT5a in TGF-β-activated human cardiac fibroblasts. We found that WNT3a and TGF-β induced a β-catenin-dependent response, whereas WNT5a prompted AP-1 activity. TGF-β triggered profibrotic signatures in cardiac fibroblasts, and co-stimulation with WNT3a or co-activation of the β-catenin pathway with the GSK3β inhibitor CHIR99021 enhanced collagen I and fibronectin production and development of active contractile stress fibers. In the absence of TGF-β, neither WNT3a nor CHIR99021 exerted profibrotic responses. On a molecular level, in TGF-β-activated fibroblasts, WNT3a enhanced phosphorylation of TAK1 and production and secretion of IL-11 but showed no effect on the Smad pathway. Neutralization of IL-11 activity with the blocking anti-IL-11 antibody effectively reduced the profibrotic response of cardiac fibroblasts activated with TGF-β and WNT3a. In contrast to canonical WNT3a, co-activation with non-canonical WNT5a suppressed TGF-β-induced production of collagen I. In conclusion, WNT/β-catenin signaling promotes TGF-β-mediated fibroblast-to-myofibroblast transition by enhancing IL-11 production. Thus, the uncovered mechanism broadens our knowledge on a molecular basis of cardiac fibrogenesis and defines novel therapeutic targets for fibrotic heart diseases.

What's all the hype with fibre type? Selective single fibre adaptations with lifelong endurance exercise.

What's all the hype with fibre type? Selective single fibre adaptations with lifelong endurance exercise.

From Microspikes to Stress Fibers: Actin Remodeling in Breast Acini Drives Myosin II-Mediated Basement Membrane Invasion.

The cellular mechanisms of basement membrane (BM) invasion remain poorly understood. We investigated the invasion-promoting mechanisms of actin cytoskeleton reorganization in BM-covered MCF10A breast acini. High-resolution confocal microscopy has characterized actin cell protrusion formation and function in response to tumor-resembling ECM stiffness and soluble EGF stimulation. Traction force microscopy quantified the mechanical BM stresses that invasion-triggered acini exerted on the BM–ECM interface. We demonstrate that acini use non-proteolytic actin microspikes as functional precursors of elongated protrusions to initiate BM penetration and ECM probing. Further, these microspikes mechanically widened the collagen IV pores to anchor within the BM scaffold via force-transmitting focal adhesions. Pre-invasive basal cells located at the BM–ECM interface exhibited predominantly cortical actin networks and actin microspikes. In response to pro-invasive conditions, these microspikes accumulated and converted subsequently into highly contractile stress fibers. The phenotypical switch to stress fiber cells matched spatiotemporally with emerging high BM stresses that were driven by actomyosin II contractility. The activation of proteolytic invadopodia with MT1-MMP occurred at later BM invasion stages and only in cells already disseminating into the ECM. Our study demonstrates that BM pore-widening filopodia bridge mechanical ECM probing function and contractility-driven BM weakening. Finally, these EMT-related cytoskeletal adaptations are critical mechanisms inducing the invasive transition of benign breast acini.

Dietary Supplementation of Octacosanol Improves Exercise-Induced Fatigue and Its Molecular Mechanism.

Several publications report that octacosanol (OCT) has different biological functions. This study was designed to evaluate the antifatigue effect and molecular mechanism of octacosanol (200 mg/(kg day)) in forced exercise-induced fatigue models of trained male C57BL/6 mice. Results showed that octacosanol ameliorated the mice's autonomic activities, forelimb grip strength, and swimming endurance, and the levels of liver glycogen (LG), muscle glycogen (MG), blood lactic acid (BLA), lactate dehydrogenase (LDH), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) were also regulated. Gene analysis results showed that treatment with OCT upregulated 29 genes, while 38 genes were downregulated in gastrocnemius tissue. Gene ontology (GO) analyses indicated that these genes enriched functions in relation to myofibril, contractile fiber, and calcium-dependent adenosinetriphosphatase (ATPase) activity. Octacosanol supplementation significantly adjusted the messenger RNA (mRNA) and protein expression levels related to fatigue performance. Octacosanol has an observably mitigating effect in exercise-induced fatigue models, and its molecular mechanism may be related to the regulation of tripartite motif-containing 63 (Trim63), periaxin (Prx), calcium voltage-gated channel subunit α1 H (Cacna1h), and myosin-binding protein C (Mybpc3) expression.

Chronic intermittent hypobaric hypoxia attenuates ischemic limb injury by promoting angiogenesis in mice.

This study aimed to evaluate the protective effect of chronic intermittent hypobaric hypoxia (CIHH) against limb ischemic injury. C57BL/6 mice were randomly divided into three groups: limb ischemic injury group (Ischemia, induced by ligation and excision of the left femoral artery), limb ischemia following CIHH pretreatment group (CIHH+Ischemia, simulated a 5000 m altitude hypoxia, 6h per day for 28days, before induction of hind-limb ischemia), and sham group (Sham). The blood flow in the mouse models of hind-limb ischemia was examined using laser doppler imaging. The functional and morphological performance of ischemic muscle was evaluated using contraction force and hematoxylin-eosin and Masson's trichrome staining. Angiogenesis was determined by immunohistochemistry staining of the endothelial markers CD31 and CD34. The protein expressions of angiogenesis-related genes were detected using Western blot assay. Chronic ischemia resulted in reduced blood perfusion, decreased contraction tension, and morphological destruction in gastrocnemius muscle. CIHH pretreatment increased the contractile force and muscle fiber diameter and decreased necrosis and fibrosis of the ischemic muscle. Also, CIHH significantly increased the density of CD31+ and CD34+ cells and promoted the expression of angiogenesis-related molecules in ischemic muscle. These data demonstrate that CIHH has a protective effect against chronic limb ischemia by promoting angiogenesis.

Proleg retractor muscles in Manduca sexta larvae are segmentally different, suggesting anteroposterior specialization.

Manduca sexta larvae are an important model system for studying the neuromechanics of soft body locomotion. They climb on plants using the abdominal prolegs to grip and maneuver in any orientation and on different surfaces. The prolegs grip passively with an array of cuticular hooks, and grip release is actively controlled by retractor muscles inserted into the soft planta membrane at the proleg tip. Until now, the principal planta retractor muscles (PPRMs) in each body segment were thought to be a single fiber bundle originating on the lateral body wall. Here, using high resolution X-ray microtomography of intact animals, we show that the PPRM is a more complex muscle consisting of multiple contractile fibers originating at several distinct sites on the proleg. Furthermore, we show that there are segmental differences in the number and size of some of these fiber groups which suggests that the prolegs may operate differently along the anterior-posterior axis.

Sex differences in systemic bone and muscle loss following femur fracture in mice.

Fracture induces systemic bone loss in mice and humans, and a first (index) fracture increases the risk of future fracture at any skeletal site more in men than women. The etiology of this sex difference is unknown, but fracture may induces a greater systemic bone loss response in men. Also sex differences in systemic muscle loss after fracture have not been examined. We investigated sex differences in systemic bone and muscle loss after transverse femur fracture in 3-month-old male and female C57BL/6 J mice. Whole-body and regional bone mineral content and density (BMC and BMD), trabecular and cortical bone microstructure, muscle contractile force, muscle mass, and muscle fiber size were quantified at multiple time points postfracture. Serum concentrations of inflammatory cytokines (IL-1β, IL-6, and TNF-α) were measured 1-day postfracture. One day postfracture, IL-6 and Il-1B were elevated in fracture mice of both sexes, but TNF-α was only elevated in male fracture mice. Fracture reduced BMC, BMD, and trabecular bone microstructural properties in both sexes 2 weeks postfracture, but declines were greater in males. Muscle contractile force, mass, and fiber size decreased primarily in the fractured limb at 2 weeks postfracture and females showed a trend toward greater muscle loss. Bone and muscle properties recovered by 6 weeks postfracture. Overall, postfracture systemic bone loss is greater in men, which may contribute to sex differences in subsequent fracture risk. In both sexes, muscle loss is primarily confined to the injured limb and fracture may induce greater inflammation in males.

MO074TILVESTAMAB, A FUNCTION-BLOCKING MONOCLONAL ANTIBODY INHIBITOR OF AXL RTK SIGNALLING, LIMITS THE ONSET OF RENAL FIBROTIC CHANGES IN HUMAN KIDNEYS EX VIVO

Abstract Background and Aims Interstitial fibrosis, characterised by the accumulation of extracellular matrix in the cortical interstitium, is directly correlated with progressive chronic kidney disease secondary to inflammatory, immunologic, obstructive or metabolic causes. An invariant histologic marker of this progression is the accumulation of fibroblasts, with the phenotypic appearance of activated myofibroblasts expressing alpha smooth muscle actin (αSMA) within intracellular contractile stress fibres. Once present, these myofibroblasts are prognostic indicators of expansion of fibrotic matrix and progressive tubular atrophy, leading towards end-stage disease. The Receptor Tyrosine Kinase AXL is involved in a range of kidney pathologies, with increased activity associated with Epithelial to Mesenchymal Transition (EMT) and tubular proliferation following podocyte loss. In mice treated with an angiotensin-converting enzyme (ACE) inhibitor, enhancement of AXL expression is localised to tubular segments within the medulla and there is evidence of parallel regulatory control of ACE and AXL. We have demonstrated enhanced expression of AXL and the mesenchymal marker, vimentin in diseased human kidney tissue secondary to diabetes or hypertension. Targeting AXL with a small-molecule inhibitor has previously been reported to attenuate fibrosis and reduce inflammation in the unilateral ureteric-outflow obstruction (UUO) model of kidney fibrosis in mice (Landolt et al., 2019). Tilvestamab is a novel function blocking humanized anti-AXL antibody. Tilvestamab blocks GAS6-mediated AXL receptor activation in fibroblasts and renal tubule epithelial cells and mediates AXL receptor internalization and degradation. In this study we aimed to further characterise AXL as a target in CKD and to investigate anti-fibrotic efficacy of tilvestamab. Method Eight weeks old male C57BL/6 mice underwent UUO operation. After 15 days, kidneys were dissociated and stained with a high dimensional single cell mass cytometry 33 markers antibody panel. Data were analysed using JMP Genomics (v.8.2). Precision Cut Kidney Slices (PCKSs) from explanted human kidney tissue were propagated in a bioreactor (Paish et al., 2019, FibroFind, UK). PCKS were incubated for 72hrs in the presence of investigational drugs. Secreted collagen1a1 were quantified by ELISA. RNA was reverse transcribed to cDNA and used in qPCRs to measure Col1a1 and αSMA. FFPE sections were stained for αSMA. High magnification images were taken of each slide and analysed for surface area covered by the stain. Results Expression pattern of AXL during development of kidney fibrosis in the UUO model was investigated using a mass cytometry antibody panel designed for identifying subpopulations of immune cells as well as cell populations of the fibrotic stroma. Two predominant cell populations were affected by ligation; the mesenchymal and the immune island. AXL was a marker characterising several of the key populations that expanded upon ligation supporting a role for AXL in kidney fibrosis pathogenesis. In an ex vivo model of human PCKS, tilvestamab dose-dependently reduced the levels of αSMA. When combined with the lower of two doses of the ACE inhibitor enalapril, the lowest dose of tilvestamab synergized to reduce αSMA levels further as well as reducing secreted Collagen 1a1. Conclusion AXL expression is induced in key cell populations during development of kidney fibrosis supporting AXL as a novel target in CKD. Tilvestamab represents a promising strategy for the pharmacologic intervention of kidney fibrosis, and the potential synergy with current reno-protective therapies warrants further exploration.

Angiotensin 1-7 protects against ventilator-induced diaphragm dysfunction.

Mechanical ventilation (MV) is a life‐saving instrument used to provide ventilatory support for critically ill patients and patients undergoing surgery. Unfortunately, an unintended consequence of prolonged MV is the development of inspiratory weakness due to both diaphragmatic atrophy and contractile dysfunction; this syndrome is labeled ventilator‐induced diaphragm dysfunction (VIDD). VIDD is clinically important because diaphragmatic weakness is an important contributor to problems in weaning patients from MV. Investigations into the pathogenesis of VIDD reveal that oxidative stress is essential for the rapid development of VIDD as redox disturbances in diaphragm fibers promote accelerated proteolysis. Currently, no standard treatment exists to prevent VIDD and, therefore, developing a strategy to avert VIDD is vital. Guided by evidence indicating that activation of the classical axis of the renin‐angiotensin system (RAS) in diaphragm fibers promotes oxidative stress and VIDD, we hypothesized that activation of the nonclassical RAS signaling pathway via angiotensin 1‐7 (Ang1‐7) will protect against VIDD. Using an established animal model of prolonged MV, our results disclose that infusion of Ang1‐7 protects the diaphragm against MV‐induced contractile dysfunction and fiber atrophy in both fast and slow muscle fibers. Further, Ang1‐7 shielded diaphragm fibers against MV‐induced mitochondrial damage, oxidative stress, and protease activation. Collectively, these results reveal that treatment with Ang1‐7 protects against VIDD, in part, due to diminishing oxidative stress and protease activation. These important findings provide robust evidence that Ang1‐7 has the therapeutic potential to protect against VIDD by preventing MV‐induced contractile dysfunction and atrophy of both slow and fast muscle fibers.