Implication de la MAO-A dans l'insuffisance cardiaque et dans la sénescence intrinsèque du myocarde

L'insuffisance cardiaque (IC) est l'étape finale de nombreuses pathologies cardio-vasculaires (PCV). Son pronostic est sévère et plus sombre chez le sujet âgé, en raison de la sénescence intrinsèque du myocarde qui constitue un facteur de vulnérabilité. La MAO-A est une enzyme mitochondriale qui réalise la déamination oxydative des amines biogènes ; elle est une source de stress oxydant par la libération d'H2O2. Dans le cœur, cette enzyme augmente dans de nombreuses conditions pathologiques aiguës et chroniques, mais aussi au cours de la sénescence physiologique. Dans une première partie, nous avons étudié les conséquences fonctionnelles d'une augmentation de la MAO-A dans le cardiomyocyte grâce à un modèle murin surexprimant la MAO-A. Nous avons montré que ces souris présentaient un fort stress oxydant et évoluaient spontanément vers l'IC. Nous avons mis en évidence un lien entre la MAO-A, le stress oxydant, l'activation par phosphorylation de p53 et la mort des cardiomyocytes par nécrose. Dans une seconde partie, pour étudier le lien MAO-A/sénescence intrinsèque du myocarde, nous avons fait appel à plusieurs modèles animaux : la souris transgénique précédente, la souris KO-MAO-A, la souris sauvage et le rat. Nous avons mis en évidence : un lien entre la MAO-A et le remodelage au cours de la sénescence, l'augmentation des protéines p21 et p53, une fission mitochondriale qui peut être prévenue par l'inhibition de la MAO-A. Cette observation ouvre de nouvelles perspectives dans le domaine de la dynamique mitochondriale.Heart failure (HF) is often the end stage of many cardiovascular diseases (CVD). The prognosis of HF is severe and worse in the elderly. One reason is the intrinsic myocardial senescence constitutes a vulnerability factor. MAO-A is a mitochondrial enzyme that catalyzes the oxidative deamination of biogenic amines and is a source of oxidative stress by the release of H2O2. In the heart, this enzyme increases in many acute and chronic pathological conditions but also during physiological senescence. In the first part of our work, we investigated the functional consequences of increased MAO-A in the heart, thanks transgenic mice overexpressing MAO-A in the adult cardiomyocyte. Mice exhibited strong oxidative stress and spontaneous progressive HF. In addition, we have demonstrated a relationship between MAO-A, oxidative stress, activation of p53 by phosphorylation and necrotic death of cardiomyocytes. In the second part, we focused on the relationship between MAO-A and intrinsic myocardial aging. We studied different animal modeles: transgenic mice overexpressing MAO-A, MAO-A knock-out mice, wild type mice and rat. We have demonstrated : an association between MAO-A and the myocardial remodeling during aging, enhancement of p21 and p53, mitochondrial fission which can be prevented by inhibition of MAO-A.This data opens new perspectives in the field of mitochondrial dynamics

Evaluation of polyelectrolyte complex-based scaffolds for mesenchymal stem cell therapy in cardiac ischemia treatment

Three-dimensional (3D) scaffolds hold great potential for stem cell-based therapies. Indeed, recent results have shown that biomimetic scaffolds may enhance cell survival and promote an increase in the concentration of therapeutic cells at the injury site. The aim of this work was to engineer an original polymeric scaffold based on the respective beneficial effects of alginate and chitosan. Formulations were made from various alginate/chitosan ratios to form opposite-charge polyelectrolyte complexes (PECs). After freeze-drying, the resultant matrices presented a highly interconnected porous microstructure and mechanical properties suitable for cell culture. In vitro evaluation demonstrated their compatibility with mesenchymal stell cell (MSC) proliferation and their ability to maintain paracrine activity. Finally, the in vivo performance of seeded 3D PEC scaffolds with a polymeric ratio of 40/60 was evaluated after an acute myocardial infarction provoked in a rat model. Evaluation of cardiac function showed a significant increase in the ejection fraction, improved neovascularization, attenuated fibrosis as well as less left ventricular dilatation as compared to an animal control group. These results provide evidence that 3D PEC scaffolds prepared from alginate and chitosan offer an efficient environment for 3D culturing of MSCs and represent an innovative solution for tissue engineering

Case Report Beneficial Effect of Conversion to Belatacept in Kidney-Transplant Patients with a Low Glomerular-Filtration Rate

Belatacept has been found to be efficient at preserving good kidney function in maintenance kidney-transplant patients. Herein, we report on the use of belatacept as a rescue therapy for two kidney-transplant patients presenting with severe adverse events after treatment with calcineurin inhibitors (CNIs) and mammalian target-of-rapamycin (mTOR) inhibitors. Two kidney-transplant patients developed severely impaired kidney function after receiving CNIs. The use of everolimus was associated with severe angioedema. Belatacept was then successfully used to improve kidney function in both cases, even though estimated glomerularfiltration rate before conversion was <20 mL/min. These case reports show that belatacept can be used as a rescue therapy, even if kidney function is very low in kidney-transplant patients who cannot tolerate CNIs and/or mTOR inhibitors

A new HPF specimen carrier adapter for the use of high-pressure freezing with cryo-scanning electron microscope: two applications: stearic acid organization in a hydroxypropyl methylcellulose matrix and mice myocardium .

Cryogenic transmission electron microscopy of high-pressure freezing (HPF) samples is a well-established technique for the analysis of liquid containing specimens. This technique enables observation without removing water or other volatile components. The HPF technique is less used in scanning electron microscopy (SEM) due to the lack of a suitable HPF specimen carrier adapter. The traditional SEM cryotransfer system (PP3000T Quorum Laughton, East Sussex, UK; Alto Gatan, Pleasanton, CA, USA) usually uses nitrogen slush. Unfortunately, and unlike HPF, nitrogen slush produces water crystal artefacts. So, we propose a new HPF specimen carrier adapter for sample transfer from HPF system to cryogenic-scanning electronic microscope (Cryo-SEM). The new transfer system is validated using technical two applications, a stearic acid in hydroxypropyl methylcellulose solution and mice myocardium. Preservation of samples is suitable in both cases. Cryo-SEM examination of HPF samples enables a good correlation between acid stearic liquid concentration and acid stearic occupation surface (only for homogeneous solution). For biological samples as myocardium, cytoplasmic structures of cardiomyocyte are easily recognized with adequate preservation of organelle contacts and inner cell organization. We expect this new HPF specimen carrier adapter would enable more SEM-studies using HPF

Evaluation of polyelectrolyte complex-based scaffolds for mesenchymal stem cell therapy in cardiac ischemia treatment

b s t r a c t Three-dimensional (3D) scaffolds hold great potential for stem cell-based therapies. Indeed, recent results have shown that biomimetic scaffolds may enhance cell survival and promote an increase in the concentration of therapeutic cells at the injury site. The aim of this work was to engineer an original polymeric scaffold based on the respective beneficial effects of alginate and chitosan. Formulations were made from various alginate/chitosan ratios to form opposite-charge polyelectrolyte complexes (PECs). After freeze-drying, the resultant matrices presented a highly interconnected porous microstructure and mechanical properties suitable for cell culture. In vitro evaluation demonstrated their compatibility with mesenchymal stell cell (MSC) proliferation and their ability to maintain paracrine activity. Finally, the in vivo performance of seeded 3D PEC scaffolds with a polymeric ratio of 40/60 was evaluated after an acute myocardial infarction provoked in a rat model. Evaluation of cardiac function showed a significant increase in the ejection fraction, improved neovascularization, attenuated fibrosis as well as less left ventricular dilatation as compared to an animal control group. These results provide evidence that 3D PEC scaffolds prepared from alginate and chitosan offer an efficient environment for 3D culturing of MSCs and represent an innovative solution for tissue engineering

Étude du statut de la protéine éphrine B1 dans le glomérule rénal (modèle murin et application humaine, la glomérulopathie d'allogreffe)

TOULOUSE3-BU Santé-Centrale (315552105) / SudocSudocFranceF

Biophysical properties of cardiomyocyte surface explored by multiparametric AFM

International audiencePeakForce Quantitative Nanomechanical Mapping (PeakForce QNM) multiparametric AFM mode was adapted to qualitative and quantitative study of the lateral membrane of cardiomyocytes (CMs), extending this powerful mode to the study of soft cells. On living CM, PeakForce QNM depicted the crests and hollows periodic alternation of cell surface architecture previously described using AFM Force Volume (FV) mode. PeakForce QNM analysis provided better resolution in terms of pixel number compared to FV mode and reduced acquisition time, thus limiting the consequences of spontaneous living adult CM dedifferentiation once isolated from the cardiac tissue. PeakForce QNM mode on fixed CMs clearly visualized subsarcolem-mal mitochondria (SSM) and their loss following formamide treatment, concomitant with the interfibrillar mitochondria climbing up and forming heaps at the cell surface. Interestingly, formamide-promoted SSM loss allowed visualization of the sarcomeric apparatus ultrastructure below the plasma membrane. High PeakForce QNM resolution led to better contrasted mechanical maps than FV mode and provided correlation between adhesion, dissipation, mechanical and topographical maps. Modified hydrophobic AFM tip enhanced contrast on adhesion and dissipation maps and suggested that CM surface crests and hollows exhibit distinct chemical properties. Finally, two-dimensional Fast Fourier Transform to objectively quantify AFM maps allowed characterization of periodicity of both sarcomeric Z-line and M-band. Overall, this study validated PeakForce QNM as a valuable and innovative mode for the exploration of living and fixed CMs. In the future, it could be applied to depict cell membrane architectural, mechanical and chemical defects as well as sarcomeric abnormalities associated with cardiac diseases

Atomic Force Microscopy: an innovative technology to explore cardiomyocyte cell surface in cardiac physio/pathophysiology

International audienceAtomic Force Microscopy (AFM) has emerged these recent years as a multifunctional toolbox for studying biological samples in physiological conditions. Although its use has spread among biologists community, cardiology remains a scientific field where not been extensively used yet. Heart diseases are nowadays a major human threat, and cause the death of millions of people each year. A convergent point to all heart diseases seems to be related to the defect of the cardiomyocyte, the contractile unit of the he reason, many scientists got interested in this cell type. However, very few studies use a technology such as AFM and its derivatives (force spectroscopy, multiparametric imaging) to explore this cell. The aim of this review is thus to give a comprehensive an interest of the biophysical approach made possible by AFM studies. We will show how AFM has been and can be used to study fix living cardiomyocytes, and, how combined with other types of microscopy, it can help getting a better understanding o pathologies or drugs. This review is the first dedicated to the use of AFM technics in cardiology, and gives new insights in fundamental questions surrounding cardiomyocytes, that can be answered using such a technology