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International audience; Skeletal muscle contains cell populations displaying aldehyde dehydrogenase (ALDH) activitythat confers proliferation, aldehyde detoxification, and survival capacities, and produces essentialmetabolites, such as retinoic acid. We previously distinguished two progenitor cell populationsbased on the expression of the extracellular marker CD34: ALDH+CD34- cells engage in amyogenic program in vitro and in vivo while ALDH+CD34+ cells differentiate towards amesenchymal program (i.e., osteogenic, chondrogenic, and adipose tissue). ALDH+ cells couldbe used for cell therapy, mandating more characterization in healthy and dystrophic tissues.Here, we investigated the presence and characteristics of total ALDH+ cells and the expressionof the 19 ALDH isoenzymes in aging and Duchenne muscular dystrophy (DMD) skeletalmuscles using the complementary methods of flow cytometry, immunofluorescence, andquantitative reverse-transcription polymerase chain reaction. In Humans (n=50), we found noinfluence of age (28-93 years old) and sex (25 women, 25 men) on the number of ALDH+ cells.In contrast, DMD was associated with a significant increase in total ALDH+ cells in both humanpatients' skeletal muscle and dog models. This increase was mostly driven by the non-myogenicALDH+CD34+ subpopulation and corresponded to increased interstitial cells expressing theisoenzymes ALDH1L1, ALDH3A2, and ALDH9A1.Our study suggests a pivotal role for ALDH metabolism in muscle, depending on whichisoenzymes are expressed. ALDH1A1, mostly expressed in healthy tissue and involved in theretinoic acid pathway, could contribute to homeostasis, while ALDH1L1, ALDH3A2, andALDH9A1 could participate in or result from the remodeling in dystrophic muscle (e.g., fibrosis,inflammation, and adipose tissue expansion). (Etienne et al., JCSM 2020; 11:1047-1069).

International audience; L’injection d’efgartigimod dans un modèle murin expérimental de myasthénie (anti-MuSK) permet une réduction importante du taux d’autoanticorps circulants avec comme corollaire une amélioration des signes cliniques et une augmentation des per formances physiques chez les souris traitées par rap port aux souris non-traitées [1].La Myasthenia Gravis (myasthénie, MG) est une maladie neuromusculaire auto-immune liée à une réaction immunitaire aberrante dirigée contre des constituants de la jonction neuromusculaire. Cette attaque est médiée par des auto-anticorps (Ac) ciblant des récepteurs post-synaptiques : le récepteur de l’acé- tylcholine (AchR) en premier lieu, le récepteur tyro- sine-kinase spécifique du muscle (MuSK), la lipopro tein-related protein 4 (LRP4), ou l’agrine. Ce processus diminue l’efficacité de la dépolarisation mus culaire, ce qui se traduit par une faiblesse musculaire fluctuante et une fatigabilité. Les patients atteints de MG avec Ac anti-MuSK (appelée aussi MuSK-MG, soit environ 5% des cas de MG) présentent souvent des signes respiratoires. La sévérité de la maladie est d’ail leurs liée au taux d’Ac circulants. Un modèle animal de MuSK-MG a pu être obtenu par transfert passif des Ac de patients à des souris immunodéficientes, une MG se développant chez elles en quelques jours.La diminution du titre des Ac circulants pathogènes est l’une des stratégies thérapeutiques mises au point dans la MG. Les séances de plasmaphérèse lors d’une poussée de la maladie (crise myasthé- nique) permettent de l’obtenir. Une autre approche innovante, cette fois-ci sous la forme d’une immu nothérapie vise à augmenter le catabolisme naturel de ces Ac. Ainsi, le récepteur néonatal Fc (FcRn) régule le catabolisme des immunoglobulines de type G (IgG) en diminuant leur dégradation lysosomale. L’utilisation d’antagonistes de ce FcRn empêche le recyclage des IgGs et favorise leur dégradation. Dans le contexte de la MG, ceci favoriserait la clai rance des IgG pathogènes et réduirait leur effet délé tère au niveau clinique. L’efgartigimod (ou ARGX- 113) est le fragment Fc d’un anticorps monoclonal de type IgG1 humain amputé du domaine variable (Fab). Ce fragment Fc a été modifié pour assurer une liaison de forte affinité aux FcRn, en particulier dans un environnement lysosomal acide.Dans cette étude, les souris ont reçu des Ac de patients Musk-MG d’abord quotidiennement, puis une combinaison d’Ac et d’efgartigimod versus pla cebo, pendant les onze jours suivants. Alors que les souris non traitées ou traitées par placebo ont vu leur état clinique se dégrader, les souris traitées par efgartigimod ont montré des signes d’amélioration. Sur le plan humoral, une réduction d’environ 80% du taux d’Ac humain anti-MuSK circulants a été observée. Sur le plan général, l’efgartigimod empêche la perte progressive de poids habituelle ment observée chez les souris malades. Au niveau fonctionnel, l’efgartigimod évite la perte de force détectée aux tests d’agrippement. Il réduit aussi la perte de force musculaire et la fatigabilité. En élec trophysiologie, on observe un décrément moindre lors de la stimulation nerveuse répétitive. En revanche, aucune différence n’a été notée entre les deux groupes concernant les aspects ultrastructu- raux de la jonction neuromusculaire. Ces résultats soulignent le potentiel thérapeutique intéressant de cette nouvelle molécule dans cette forme spécifique de MG

International audience

International audience; Several autoimmune diseases are mediated by antibodies produced after deregulations of the immune system and directed against self antigens. Myasthenia Gravis (MG) is a rare disease in which pathogenicity is due to autoantibodies directed against the neuromuscular endplate. MG is not really cured, corticosteroids and azathioprin are commonly used, however they trigger severe side-effects, mandating the setup of novel therapies. Mesenchymal Stromal/Stem Cells (MSC) are multipotent progenitor cells that can be isolated from various human tissues and can modulate the immune system via soluble mediators and cell-cell contacts. Our team has recently validated a new animal model of MG, in which we demonstrated that the transfer of MSC conditioned by peripheral blood mononucleated cells (PBMC) improved the clinical status of the animals (Sudres et al., JCI Insight 2017). To develop this immunomodulating approach in clinical perspective, we compared the phenotypes of research-grade (RG) and clinical-grade (CG) MSC testing a series of 60 antibodies (Ab) directed against surface antigens by flow cytometry. We evaluated the variations introduced by different conditioning treatments (activation by gamma-interferon, cross-stimulation by PBMC or monocytes). Markers involved in immunomodulation (recognition, activation, function of complement, co-stimulation, immune checkpoints) were increased or decreased depending on treatment. Adhesion molecules and receptors were also differentially modified (integrins, selectins, cell-cell adhesion molecules, growth factor receptors, tetraspanins). These results suggest that the conditioning regimens act through different pathways. From this panel, we derived a second one of 31 Ab allowing simultaneous labeling of MSC at single cell level by mass cytometry (CyTOF). We defined MSC clusters which were modulated upon activation. In parallel, we evaluated the functional activity of resting or conditioned CG MSC through a cell proliferation assay, and through the quantification by ELISA of secreted immunomodulating products. The conditioning regimens differentially modulated the secretion of Prostaglandin E2 and TGFbeta1, and inhibited PBMC proliferation. This work unveiled phenotypic and functional markers of MSC along with their modulations according to different treatments, and will contribute to validate a cell therapy product for immunomodulation purposes.

International audience; Aldehyde dehydrogenases (ALDH) participate to the metabolism and detoxification of aldehydes and play important roles in cell survival. Moreover, the coordinated expression of several isoenzymes (e.g. ALDH-1A1, -1A2, -1A3, -1B1, -8A1) is finely tuned to regulate the production of retinoic acid involved in the formation of several tissues. However, the localization of ALDHs-expressing cells within muscle tissues, their evolution during ageing or in pathological contexts, their potential functions, are scarcely described. In skeletal muscle, we previously described a population of ALDH+ /CD34- cells harboring myogenic capacities amenable to use in cell therapy. Here, we explored the presence and persistence of these cells in tissues of human donors (healthy, young or aged, versus patients presenting Duchenne muscular dystrophy), of non-human primates (healthy, several anatomical territories being compared), and of dogs (healthy versus the Golden Retriever model of Duchenne muscular Dystrophy). While no significant variation was observed with ageing or between anatomical territories, important changes were manifested between healthy and pathological tissues. We identified extracellular markers associated with expression of ALDH activity. Phenotypic characterization indicated that human ALDH+ /CD34- cells are mainly associated with the extracellular markers CD9, CD36, CD49a, CD49c, CD49f, CD106, CD146, CD184, some being associated to myogenic capacities. We identified several isoenzymes expressed by myogenic and non-myogenic cells present in muscle ex vivo and in vitro at the protein and mRNA levels. Histological analysis ex vivo documented the presence of different cell types harboring isoenzymes in specific anatomical locations, i.e. inside muscle fibers, or in satellite-like position, or in the endomysium, or participating to vessel or neural architectures. Cytological analysis identified cell populations expressing different isoenzymes in vitro (ALDH-1A1, -1A2, -1A3, -2, -3A1, -3A2, -3B1, - 3B2, -4A1, -7A1, -8A1). Finally the analysis of gene expression suggested that, at least, ALDH-1A1, -1A3, -1B1, -2, -3A2, -7A1, -8A1 and -9A1 isoenzymes are involved in muscle homeostasis. This study therefore unveils the importance of the ALDH isoenzymes family in skeletal muscle physiology

Heart failure is a major concern for public health systems, and several approaches of cellular therapy are being investigated with the goal of improving the function of these failing hearts. Many cell types have been used (skeletal myoblasts, hematopoietic, endothelial or mesenchymal progenitors, cardiac cells…), most often in the indication of post-ischemic heart failure rather than in the indication of genetic dilated cardiomyopathy. It is easier, indeed, to target a restricted area than the whole myocardium. Several clinical trials have reported slight but encouraging functional benefits, but their interpretations were frequently limited by the small sizes of cohorts, and by the biological variabilities inherent to the patients status and to the biology of the cells. These trials also shed light on unexpected mechanisms of action of the cells, which are changing the concepts and methodologies of the studies. The functional benefits observed would be due, indeed, to the secretion of trophic factors by the cells, instead of their true structural and mechanical integration within the myocardial tissue. Accordingly, the new generations of clinical trials aim at improving the size and homogeneity of the patient cohorts to increase the statistical power. On the other hand, several studies are associating or conditionning cells with biomaterials or cocktails of cytokines to improve their survival and their biological efficacy. In parallel, bio-engineering investigates several ways to support cells in vitro and in vivo, to sustain the architectural structure of the failing myocardium, to produce ex vivo some true substitutive cardiac tissue, or to purely replace the cells by their active secreted products. Several therapeutic devices should emerge from these researches, and the choice of their respective use will be ultimately guided by the medical indication., L’insuffisance cardiaque est un problème majeur de santé publique et différentes approches de thérapie cellulaire sont expérimentées pour améliorer la fonction de myocardes défaillants. De nombreux types cellulaires ont été utilisés (myoblastes squelettiques, cellules hématopoïétiques, endothéliales ou mésenchymateuses, cellules d’origine cardiaque…), plus souvent dans des indications d’insuffisance post-ischémique que de cardiomyopathie dilatée génétique. Il est en effet plus aisé de cibler une zone de réparation localisée que l’ensemble du tissu myocardique. De nombreux essais cliniques ont fait état de résultats fonctionnels de faibles ampleurs mais encourageants, dont l’interprétation est souvent limitée par la taille des cohortes et les variabilités biologiques liées aux patients et aux candidats cellulaires. Ces essais ont aussi mis en lumière des mécanismes d’action inattendus, qui changent les concepts et méthodologies de traitement. En effet, les bénéfices proviendraient de sécrétions de facteurs trophiques, plutôt que d’une intégration structurale des cellules au sein du myocarde. Par conséquent, les nouvelles générations d’essais visent à accroître la taille et l’homogénéité des cohortes de patients afin d’améliorer la puissance statistique. Par ailleurs, des études misent sur l’accompagnement et/ou le conditionnement des cellules à l’aide de biomatériaux et/ou de cocktails de cytokines, en vue d’améliorer leur survie et leur fonctionnement. En parallèle, de nombreuses recherches en bio-ingénierie s’intéressent au soutien des cellules, au maintien de la structure du myocarde, à la fabrication ex vivo de tissu cardiaque de substitution, et finalement à la possibilité de remplacer les cellules par leurs produits actifs de sécrétion. Plusieurs dispositifs devraient émerger de ces recherches, dont le choix sera guidé par l’indication médicale.

International audience; Facioscapulohumeral muscular dystrophy type 1 (FSHD1) is one of the most frequent adult myopathies (1/20.000), with selective involvement of specific groups of muscles : facial, scapular fixator, anterior foreleg muscles, abdominal and humeral muscles. Vastus lateralis (VL) is usually spared clinically until late stages of the disease, and myoblasts grown from VL have similar behaviour in vivo and in vitro than myoblasts from control patients-> Proposal:Transplantation of autologous myoblast from spared muscle (VL) into an affected muscle as the Tibialis anterior (TA) muscle could locally improve the muscle’s regenerative capacities. Results and discussion: Cell productions were feasible but the quality of the initial muscle biopsy is important. Cell administrations were feasible and clinically well tolerated by all patients but one. The control of local cell distribution may be improved by echographic monitoring. Results show slight increases in twitch response and slight decrease in fatigue in the 3rd group. The combination of cell type (myoblasts) and of the modality (dense multisite injections) may have positively affected the TA muscle, BUT: No clinically significant gain of function perceived by FSHD patients, and no significant changes were noted at MRI and PET-Scan.The local FSHD1 degenerated muscle environment may be detrimental to the stability of the fibers or of the niches, and muscle regeneration may have been inefficient, too transitory, aborted or too unstable.The slight muscle strength increase may not be clinically significant for FSHD patients, but may improve the quality of life of patients with more advanced muscle loss (e.g. DMD patients) in other indications.

International audience; Background— Skeletal myoblast (SM) transplantation (Tx) in a post-myocardial infarction (MI) scar experimentally improves left ventricular (LV) ejection fraction (EF). Short-term follow-up (FU) studies have suggested that a similar benefit could clinically occur despite an increased risk of LV arrhythmias. Methods and Results— We report the long-term FU of the first worldwide cohort of grafted patients (n =9, 61.8±11.6 years, previous MI, EF ≤35%) operated on (autologous SM Tx and bypass surgery) in 2000 to 2001 and evaluated before Tx, at 1 month (M1) and at a median FU of 52 (18 to 58) months after Tx (37 patient-years). NYHA class improved from 2.5±0.5 to 1.8±0.4 at M1 ( P =0.004 versus baseline) and 1.7±0.5 at FU ( P =not significant versus M1; P =0.0007 versus baseline). EF increased from 24.3±4% to 31±4.1% at M1 (+28%, P =0.001 versus baseline) and remained stable thereafter (28.7±8.1%, +18% versus baseline). There were 5 hospitalizations for heart failure in 3 patients at 28.6±9.9 months, allowing implant in 2 patients with a resynchronization pacemaker. An automatic cardiac defibrillator (ACD) was implanted in 5 patients for nonsustained (n =1) or sustained (n =4) ventricular tachycardia at 12.2±18.6 (1 to 45) months. Despite a beta-blocker/amiodarone combination therapy, there were 14 appropriate shocks for 3 arrhythmic storms in 3 patients at 6, 7, and 18 months after ACD implantation. Conclusions— In this cohort of severe heart failure patients both clinical status and EF stably improve over time with a strikingly low incidence of hospitalizations for heart failure (0.13/patient-years) and the arrhythmic risk can be controlled by medical therapy and/or on-request ACD implantation.