0106: Influence of the ratio of co-expressed cardiac connexins Cx43 and Cx45 in the formation of gap junction channels and their electrical properties

The cardiac action potential (AP) propagation is regulated to permit the coordinated and rhythmic atrial and ventricular contractions. This regulation requires several factors, especially gap junctions, which ensure a direct pathway for electrical and biochemical signaling. They are clusters of few to hundred intercellular gap junction channels (GJC) made of two hemichannels docked in the membrane of adjacent cells, which are composed of six connexins (Cxs). Their distinct electrical properties are a key factor regulating the propagation of the AP. Four cardiac Cxs, Cx40, Cx43, Cx45 and Cx30.2, exhibit specific patterns of expression that change in the healthy and diseased heart, which leads to different possible configurations of GJC. The aim of this study is to investigate the function of the distinct ratio of co-expressed Cxs in regulating the formation and function of GJC. Electrical properties of GJC (junctional coupling, voltage dependence, unitary conductance) are determined by performing electrical recordings on cell pair by applying the dual voltage-clamp method. Rat Liver Epithelial cells stably transfected to induce accurate Cx43:Cx45 ratios of 0 (single Cx43 expression), 0.5, 1 and 2, are used. The ongoing recordings show distinct electrical properties before and after the induction of Cx45: induction of Cx45 decreases the cell-to-cell coupling and rectifies the voltage dependence of GJC. Preliminary unitary recordings suggest a distinct formation of GJC of mixed Cx43/Cx45 composition in function of the Cx43:Cx45 ratio. Further investigations will provide better understanding on the distinct contributions of Cx43 and Cx45 in the GJC make-up, electrical properties and function of the Cx43/Cx45 expression pattern in regulating the cardiac impulse propagation in the healthy heart, and the pro-arrhythmic behavior in the diseased heart

Transient Receptor Potential Vanilloid 4 channel participates in mouse ventricular electrical activity

International audienc

Proteomic Analysis of Human Scleroderma Fibroblasts Response to Transforming Growth Factor-ss

Purpose Systemic sclerosis (SSc) is characterized by autoimmunity, vasculopathy and fibrosis. Fibrosis is due to an activation of fibroblasts by the transforming growth factor-ss (TGF-ss). This study investigates the proteomic response of SSc fibroblasts to TGF-ss. Experimental design Skin fibroblasts from diffuse SSc patients and healthy controls (HC) are cultured with or without TGF-ss. Two-dimensional differential in-gel electrophoresis and mass spectrometry (MS) combined with Ingenuity Pathway analysis (IPA) and Panther/David software analyze proteins differentially expressed between groups. Real-time cell analyzer (RTCA) assesses fibroblast proliferation and viability. Results Two-hundred-and-seventy-nine proteins are differentially expressed between groups. Principal component analysis shows significant differences between groups. IPA shows specific process networks such as actin cytoskeleton and integrin signaling. Panther and David software show predominant biological processes such as cellular and metabolic processes. TGF-ss enhances protein synthesis and protein pathways. IPA and RTCA suggest the involvement of epidermal growth factor receptor (EGFR) and phosphatidylinositol 3 kinase (Pi3K). Conclusions and clinical relevance That the proteome of fibroblasts differs between SSc patients and HC is confirmed, and it is demonstrated that fibroblasts exacerbate their proteomic phenotype upon stimulation with TGF-ss. EGFR and Pi3K are highlighted as proteins of interest in SSc fibroblasts

Regional Differences in Ca²⁺ Signaling and Transverse-Tubules across Left Atrium from Adult Sheep

Cardiac excitation-contraction coupling can be different between regions of the heart. Little is known at the atria level, specifically in different regions of the left atrium. This is important given the role of cardiac myocytes from the pulmonary vein sleeves, which are responsible for ectopic activity during atrial fibrillation. In this study, we present a new method to isolate atrial cardiac myocytes from four different regions of the left atrium of a large animal model, sheep, highly relevant to humans. Using collagenase/protease we obtained calcium-tolerant atrial cardiac myocytes from the epicardium, endocardium, free wall and pulmonary vein regions. Calcium transients were slower (time to peak and time to decay) in free wall and pulmonary vein myocytes compared to the epicardium and endocardium. This is associated with lower t-tubule density. Overall, these results suggest regional differences in calcium transient and t-tubule density across left atria, which may play a major role in the genesis of atrial fibrillation

Compartmentalized Structure of the Moderator Band Provides a Unique Substrate for Macroreentrant Ventricular Tachycardia

Background Papillary muscles are an important source of ventricular tachycardia (VT). Yet little is known about the role of the right ventricular (RV) endocavity structure, the moderator band (MB). The aim of this study was to determine the characteristics of the MB that may predispose to arrhythmia substrates. Methods Ventricular wedge preparations with intact MBs were studied from humans (n=2) and sheep (n=15; 40-50 kg). RV endocardium was optically mapped, and electrical recordings were measured along the MB and septum. S1S2 pacing of the RV free wall, MB, or combined S1-RV S2-MB sites were assessed. Human (n=2) and sheep (n=4) MB tissue constituents were assessed histologically. Results The MB structure was remarkably organized as 2 excitable, yet uncoupled compartments of myocardium and Purkinje. In humans, action potential duration heterogeneity between MB and RV myocardium was found (324.6±12.0 versus 364.0±8.4 ms; P<0.0001). S1S2-MB pacing induced unidirectional propagation via MB myocardium, permitting sustained macroreentrant VT. In sheep, the incidence of VT for RV, MB, and S1-RV S2-MB pacing was 1.3%, 5.1%, and 10.3%. Severing the MB led to VT termination, confirming a primary arrhythmic role. Inducible preparations had shorter action potential duration in the MB than RV (259.3±45.2 versus 300.7±38.5 ms; P<0.05), whereas noninducible preparations showed no difference (312.0±30.3 versus 310.0±24.6 ms, respectively). Conclusions The MB presents anatomic and electrical compartmentalization between myocardium and Purkinje fibers, providing a substrate for macroreentry. The vulnerability to sustain VT via this mechanism is dependent on MB structure and action potential duration gradients between the RV free wall and MB

Characteristics of patients with systemic sclerosis suffering from a lower limb amputation: Results of a French collaborative study

International audienceObjective:Systemic sclerosis mainly affects the microvascular network. However, macrovascular manifestations have been reported. We aimed to investigate the characteristics of systemic sclerosis patients with an amputation of a lower limb segment.Methods:We designed a retrospective, case-control, multicentric study on systemic sclerosis patients with amputation of a lower limb segment secondary to critical ischemia via the French Research Group on Systemic Sclerosis. For each case, a control (systemic sclerosis patient without lower limb symptom) was matched with sex, age (+/- 5 years), and cutaneous subset of systemic sclerosis.Results:In total, 26 systemic sclerosis patients (mean age of 67.2 +/- 10.9 years, 20 females, 21 limited cutaneous forms) with a lower limb amputation and 26 matched controls (mean age of 67.3 +/- 11.2 years, 20 females, 22 limited cutaneous forms) were included. At the time of amputation, the mean disease duration was 12.8 (+/- 8.6) years. In comparison to controls, systemic sclerosis patients with amputation had more digital ulcers (p = 0.048), history of digital ulcers (p = 0.026), and a higher prevalence of pulmonary arterial hypertension (p = 0.024). Systemic sclerosis patients with amputation were more often smokers (p = 0.008) and under corticosteroids (p = 0.015). In the multivariate model, pulmonary arterial hypertension, smoking status, and corticosteroids were independent markers associated with lower limb amputation in systemic sclerosis. In the follow-up, 10 patients (38.5%) had recurrent ischemia requiring a new limb amputation, and five patients (19.2%) had an amputation of the contralateral limb.Conclusion:This study identifies some markers associated with lower limb amputation in systemic sclerosis such as digital ulcers and pulmonary arterial hypertension and points out the high risk associated with tobacco consumption and corticosteroid use

Heart and systemic sclerosis—findings from a national cohort study

International audienceAbstract Objectives Heart involvement is one of the leading causes of death in SSc. The prevalence of SSc-related cardiac involvement is poorly known. Our objective was to investigate the prevalence and prognosis burden of different heart diseases in a nationwide cohort of patients with SSc. Methods We used data from a multicentric prospective study using the French SSc national database. Focusing on SSc-related cardiac involvement, we aimed to determine its incidence and risk factors. Results Of the 3528 patients with SSc, 312 (10.9%) had SSc-related cardiac involvement at baseline. They tended to have a diffuse SSc subtype more frequently and to have more severe clinical features, and presented more cardiovascular risk factors. From the 1646 patients available for follow-up analysis, SSc-related cardiac involvement was associated with an increased risk of death. There was no significant difference in overall survival between SSc-related cardiac involvement, ischaemic heart disease or pulmonary arterial hypertension. Regarding survival analysis, 98 patients developed SSc-related cardiac involvement at 5 years (5-year event rate 11.15%). Regarding reduced left ventricular ejection fraction &lt;50% and left ventricular diastolic dysfunction, the 5-year event rate was 2.49% and 5.84%, respectively. Pericarditis cumulative incidence at 5 years was 3%. Diffuse SSc subtype was a risk factor for SSc-related cardiac involvement and pericarditis. Female sex was associated with less left ventricular diastolic dysfunction incidence. Conclusions Our results describe the incidence and prognostic burden of SSc-related cardiac involvement at a large scale, with gender and diffuse SSc subtype as risk factors. Further analyses should assess the potential impact of treatment on these various cardiac outcomes

Roadmap on Wavefront Shaping and deep imaging in complex media

submitted to J.Phys Photonics (IOP), 116 pages, 23 sectionsThe last decade has seen the development of a wide set of tools, such as wavefront shaping, computational or fundamental methods, that allow to understand and control light propagation in a complex medium, such as biological tissues or multimode fibers. A vibrant and diverse community is now working on this field, that has revolutionized the prospect of diffraction-limited imaging at depth in tissues. This roadmap highlights several key aspects of this fast developing field, and some of the challenges and opportunities ahead

Low incidence of SARS-CoV-2, risk factors of mortality and the course of illness in the French national cohort of dialysis patients

International audienceThe aim of this study was to estimate the incidence of COVID-19 disease in the French national population of dialysis patients, their course of illness and to identify the risk factors associated with mortality. Our study included all patients on dialysis recorded in the French REIN Registry in April 2020. Clinical characteristics at last follow-up and the evolution of COVID-19 illness severity over time were recorded for diagnosed cases (either suspicious clinical symptoms, characteristic signs on the chest scan or a positive reverse transcription polymerase chain reaction) for SARS-CoV-2. A total of 1,621 infected patients were reported on the REIN registry from March 16th, 2020 to May 4th, 2020. Of these, 344 died. The prevalence of COVID-19 patients varied from less than 1% to 10% between regions. The probability of being a case was higher in males, patients with diabetes, those in need of assistance for transfer or treated at a self-care unit. Dialysis at home was associated with a lower probability of being infected as was being a smoker, a former smoker, having an active malignancy, or peripheral vascular disease. Mortality in diagnosed cases (21%) was associated with the same causes as in the general population. Higher age, hypoalbuminemia and the presence of an ischemic heart disease were statistically independently associated with a higher risk of death. Being treated at a selfcare unit was associated with a lower risk. Thus, our study showed a relatively low frequency of COVID-19 among dialysis patients contrary to what might have been assumed