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The Neuromuscular Junction (NMJ) is a chemical synapse localized between the terminal branches of the spinal motor neurons and myofibers. In the past two decades coculture systems to generate the NMJ in culture are developed to address concerns about animal models, despite the complexity of its highly specialized structure makes the in vitro modeling a challenging task. Microfluidics, unlike mass cocultures, allow spatial and temporal control over different microenvironment by manipulating either neural cells or muscle cell populations independently. Therefore, exploiting an organ‐on‐a‐chip approach, the aim is to obtain a reliable and predictive in vitro human model of NMJ in physiological and pathological conditions, to investigate the occurrence of synapse detriment in α‐sarcoglycanopathy, a subtype of limb‐girdle muscular dystrophy. For this purpose, motor neurons derived from human induced pluripotent stem cells (hiPSCs) and either healthy or α‐sarcoglycan mutant human myogenic progenitors are seeded in two separated chambers of a microfluidic device. Differentiated myotubes and hiPSCs‐derived motor neurons on‐chip are able to establish points of interaction where pre‐ and postsynaptic structures colocalize. Moreover, the attraction of motor neurons axons by muscle fibers and the NMJ maturation appear to be affected by the muscular compartment, being impaired by the dystrophic cellular component. [ABSTRACT FROM AUTHOR]

The Notch receptor mediates cell fate decision in multiple organs. In the current work we tested the hypothesis that Nkx2.5 is a target gene of Notchi and raised the possibility that Notchi regulates myocyte commitment in the adult heart. Cardiac progenitor cells (CPC5) in the niches express Notch 1 receptor, and the supporting cells exhibit the Notch ligand Jaggedi. The nuclear translocation of Notchi intracellular domain (N1ICD) up-regulates Nkx2.5 in CPC5 and promotes the formation of cycling myocytes in vitro. N1ICD and RBP-Jk form a protein complex, which in turn binds to the Nkx2.5 promoter initiating transcription and myocyte differentiation. In contrast, transcription factors of vascular cells are down-regulated by Jaggedi activation of the Notch1 pathway. Importantly, inhibition of Notchi in infarcted mice impairs the commitment of resident CPC5 to the myocyte lineage opposing cardiomyogenesis. These observations indicate that Notchl favors the early specification of CPC5 to the myocyte phenotype but maintains the newly formed cells in a highly proliferative state. Dividing Nkx2.5-positive myocytes correspond to transit amplifying cells, which condition the replicative capacity of the heart. In conclusion, Notchi may have critical implications in the control of heart homeostasis and its adaptation to pathologic states. [ABSTRACT FROM AUTHOR]

The possibility that adult bone marrow cells (BMCs) retain a remark- able degree of developmental plasticity and acquire the cardiomyocyte lineage after infarction has been challenged, and the notion of BMC transdifferentiation has been questioned. The center of the controversy is the lack of unequivocal evidence in favor of myocardial regeneration by the injection of BMCs in the infarcted heart. Because of the interest in cell-based therapy for heart failure, several approaches including gene reporter assay, genetic tagging, cell genotyping, PCR-based detection of donor genes, and direct immunofluorescence with quantum dots were used to prove or disprove BMC transdifferentiation. Our results indicate that BMCs engraft, survive, and grow within the spared myocardium after infarction by forming junctional complexes with resident myocytes. BMC5 and myocytes express at their interface connexin 43 and N-cadherin, and this interaction may be critical for BMCs to adopt the card iomyogenic fate. With time, a large number of myocytes and coronary vessels are generated. Myocytes show a diploid DNA content and carry, at most, two sex chromosomes. Old and new myocytes show synchronicity in calcium transients, providing strong evidence in favor of the functional coupling of these two cell populations. Thus, BMC5 transdifferentiate and acquire the cardiomyogenic and vascular phenotypes restoring the infarcted heart. Together, our studies reveal that locally delivered BMC5 generate de novo myocardium composed of integrated cardiomyocytes and coronary vessels. This process occurs independently of cell fusion and ameliorates structurally and functionally the outcome of the heart after infarction. [ABSTRACT FROM AUTHOR]

The Cdkn2a locus is one of the most studied tumor suppressor loci in the context of several cancer types. However, in the last years, its expression has also been linked to terminal differentiation and the activation of the senescence program in different cellular subtypes. Knock-out (KO) of the entire locus enhances the capability of stem cells to proliferate in some tissues and respond to severe physiological and non-physiological damages in different organs, including the heart. Emery–Dreifuss muscular dystrophy (EDMD) is characterized by severe contractures and muscle loss at the level of skeletal muscles of the elbows, ankles and neck, and by dilated cardiomyopathy. We have recently demonstrated, using the LMNA Δ8–11 murine model of Emery–Dreifuss muscular dystrophy (EDMD), that dystrophic muscle stem cells prematurely express non-lineage-specific genes early on during postnatal growth, leading to rapid exhaustion of the muscle stem cell pool. Knock-out of the Cdkn2a locus in EDMD dystrophic mice partially restores muscle stem cell properties. In the present study, we describe the cardiac phenotype of the LMNA Δ8–11 mouse model and functionally characterize the effects of KO of the Cdkn2a locus on heart functions and life expectancy. [ABSTRACT FROM AUTHOR]

The recent advances, offered by cell therapy in the regenerative medicine field, offer a revolutionary potential for the development of innovative cures to restore compromised physiological functions or organs. Adult myogenic precursors, such as myoblasts or satellite cells, possess a marked regenerative capacity, but the exploitation of this potential still encounters significant challenges in clinical application, due to low rate of proliferation in vitro, as well as a reduced self-renewal capacity. In this scenario, induced pluripotent stem cells (iPSCs) can offer not only an inexhaustible source of cells for regenerative therapeutic approaches, but also a valuable alternative for in vitro modeling of patient-specific diseases. In this study we established a reliable protocol to induce the myogenic differentiation of iPSCs, generated from pericytes and fibroblasts, exploiting skeletal muscle-derived extracellular vesicles (EVs), in combination with chemically defined factors. This genetic integration-free approach generates functional skeletal myotubes maintaining the engraftment ability in vivo. Our results demonstrate evidence that EVs can act as biological "shuttles" to deliver specific bioactive molecules for a successful transgene-free differentiation offering new opportunities for disease modeling and regenerative approaches. [ABSTRACT FROM AUTHOR]