Inositol 1,4,5-trisphosphate (IP3)-dependent Ca2+ signaling mediates delayed myogenesis in Duchenne muscular dystrophy fetal muscle.

Duchenne muscular dystrophy (DMD) is a progressive neuromuscular disorder characterized by muscle wasting and premature death. The defective gene is dystrophin, a structural protein, absence of which causes membrane fragility and myofiber necrosis. Several lines of evidence showed that in adult DMD patients dystrophin is involved in signaling pathways that regulate calcium homeostasis and differentiation programs. However, secondary aspects of the disease, such as inflammation and fibrosis development, might represent a bias in the analysis. Because fetal muscle is not influenced by gravity and does not suffer from mechanical load and/or inflammation, we investigated 12-week-old fetal DMD skeletal muscles, highlighting for the first time early alterations in signaling pathways mediated by the absence of dystrophin itself. We found that PLC/IP3/IP3R/Ryr1/Ca(2+) signaling is widely active in fetal DMD skeletal muscles and, through the calcium-dependent PKCα protein, exerts a fundamental regulatory role in delaying myogenesis and in myofiber commitment. These data provide new insights into the origin of DMD pathology during muscle development.

25(OH)D Levels in Relation to Gender, Overweight, Insulin Resistance, and Inflammation in a Cross-Sectional Cohort of Northern Italian Workers: Evidence in Support of Preventive Health Care Programs.

OBJECTIVE: In recent years, the welfare of workers and the prevention of chronic disabling diseases has become a topic of great interest. This study investigates serum levels of total 25-hydroxyvitamin D (25(OH)D) in a cohort of overweight-obese and insulin-resistant northern Italian indoor workers in apparent good health followed a nutritional education program. METHODS: An observational cross-sectional study on 385 patients (females = 291, males = 94), age range 18-69 years and body mass index (BMI) > 25 kg/m2, was performed at the Department of Occupational Medicine Milan, Italy, latitude 45.465454 N. We evaluated nutritional intakes, occupational and leisure physical activity, anthropometric measurements, impedance evaluation, blood pressure, the presence of metabolic syndrome (MetS) and nonalcoholic fatty liver diseases (NAFLD) by fatty liver index (FLI). Hematologic and biochemical parameters and (25(OH)D) levels were evaluated from fasting blood samples. RESULTS: Only 10.91% of subjects had optimal values of 25(OH)D; 17.40% of the remaining 89.09% subjects were severely deficient, with no gender difference and insufficient intake of vitamin D. Only 28% declared leisure physical activity; 39.48% had metabolic syndrome and 62.60% had an FLI > 30. An inverse relationship between 25(OH)D levels and BMI was found, with a significant reduction of total 25(OH)D serum concentrations in winter. The homeostasis model assessment-insulin resistance (HOMA-IR) is positively related to BMI and inversely related to 25(OH)D concentrations. A positive correlation between vitamin D and leisure physical activity was found. At univariate analysis adjusted for age, gender and BMI, an inverse relationship between vitamin D and FLI was observed in both genders. The correlation between 25(OH)D levels, inflammation markers, BMI, and FLI showed an increased risk of cardiovascular disease in this cohort of workers. CONCLUSION: Our results suggest the rationale for a large-scale screening program for vitamin D by means of easily implementable low-cost preventive supplementation.

Therapeutic Potential of Immunoproteasome Inhibition in Duchenne Muscular Dystrophy.

Duchenne muscular dystrophy is an inherited fatal genetic disease characterized by mutations in dystrophin gene, causing membrane fragility leading to myofiber necrosis and inflammatory cell recruitment in dystrophic muscles. The resulting environment enriched in proinflammatory cytokines, like IFN-γ and TNF-α, determines the transformation of myofiber constitutive proteasome into the immunoproteasome, a multisubunit complex involved in the activation of cell-mediate immunity. This event has a fundamental role in producing peptides for antigen presentation by MHC class I, for the immune response and also for cytokine production and T-cell differentiation. Here, we characterized for the first time the presence of T-lymphocytes activated against revertant dystrophin epitopes, in the animal model of Duchenne muscular dystrophy, the mdx mice. Moreover, we specifically blocked i-proteasome subunit LMP7, which was up-regulated in dystrophic skeletal muscles, and we demonstrated the rescue of the dystrophin expression and the amelioration of the dystrophic phenotype. The i-proteasome blocking lowered myofiber MHC class I expression and self-antigen presentation to T cells, thus reducing the specific antidystrophin T cell response, the muscular cell infiltrate, and proinflammatory cytokine production, together with muscle force recovery. We suggest that i-proteasome inhibition should be considered as new promising therapeutic approach for Duchenne muscular dystrophy pathology.

Adaptive Immune Response Impairs the Efficacy of Autologous Transplantation of Engineered Stem Cells in Dystrophic Dogs.

Duchenne muscular dystrophy is the most common genetic muscular dystrophy. It is caused by mutations in the dystrophin gene, leading to absence of muscular dystrophin and to progressive degeneration of skeletal muscle. We have demonstrated that the exon skipping method safely and efficiently brings to the expression of a functional dystrophin in dystrophic CD133+ cells injected scid/mdx mice. Golden Retriever muscular dystrophic (GRMD) dogs represent the best preclinical model of Duchenne muscular dystrophy, mimicking the human pathology in genotypic and phenotypic aspects. Here, we assess the capacity of intra-arterial delivered autologous engineered canine CD133+ cells of restoring dystrophin expression in Golden Retriever muscular dystrophy. This is the first demonstration of five-year follow up study, showing initial clinical amelioration followed by stabilization in mild and severe affected Golden Retriever muscular dystrophy dogs. The occurrence of T-cell response in three Golden Retriever muscular dystrophy dogs, consistent with a memory response boosted by the exon skipped-dystrophin protein, suggests an adaptive immune response against dystrophin.

Sox6 enhances erythroid differentiation in human erythroid progenitors.

Sox6 belongs to the Sry (sex-determining region Y)-related high-mobility-group-box family of transcription factors, which control cell-fate specification of many cell types. Here, we explored the role of Sox6 in human erythropoiesis by its overexpression both in the erythroleukemic K562 cell line and in primary erythroid cultures from human cord blood CD34+ cells. Sox6 induced significant erythroid differentiation in both models. K562 cells underwent hemoglobinization and, despite their leukemic origin, died within 9 days after transduction; primary erythroid cultures accelerated their kinetics of erythroid maturation and increased the number of cells that reached the final enucleation step. Searching for direct Sox6 targets, we found SOCS3 (suppressor of cytokine signaling-3), a known mediator of cytokine response. Sox6 was bound in vitro and in vivo to an evolutionarily conserved regulatory SOCS3 element, which induced transcriptional activation. SOCS3 overexpression in K562 cells and in primary erythroid cells recapitulated the growth inhibition induced by Sox6, which demonstrates that SOCS3 is a relevant Sox6 effector.

A highly conserved SOX6 double binding site mediates SOX6 gene downregulation in erythroid cells.

The Sox6 transcription factor plays critical roles in various cell types, including erythroid cells. Sox6-deficient mice are anemic due to impaired red cell maturation and show inappropriate globin gene expression in definitive erythrocytes. To identify new Sox6 target genes in erythroid cells, we used the known repressive double Sox6 consensus within the εy-globin promoter to perform a bioinformatic genome-wide search for similar, evolutionarily conserved motifs located within genes whose expression changes during erythropoiesis. We found a highly conserved Sox6 consensus within the Sox6 human gene promoter itself. This sequence is bound by Sox6 in vitro and in vivo, and mediates transcriptional repression in transient transfections in human erythroleukemic K562 cells and in primary erythroblasts. The binding of a lentiviral transduced Sox6FLAG protein to the endogenous Sox6 promoter is accompanied, in erythroid cells, by strong downregulation of the endogenous Sox6 transcript and by decreased in vivo chromatin accessibility of this region to the PstI restriction enzyme. These observations suggest that the negative Sox6 autoregulation, mediated by the double Sox6 binding site within its own promoter, may be relevant to control the Sox6 transcriptional downregulation that we observe in human erythroid cultures and in mouse bone marrow cells in late erythroid maturation.

Bone marrow-derived cells can acquire cardiac stem cells properties in damaged heart.

Experimental data suggest that cell-based therapies may be useful for cardiac regeneration following ischaemic heart disease. Bone marrow (BM) cells have been reported to contribute to tissue repair after myocardial infarction (MI) by a variety of humoural and cellular mechanisms. However, there is no direct evidence, so far, that BM cells can generate cardiac stem cells (CSCs). To investigate whether BM cells contribute to repopulate the Kit(+) CSCs pool, we transplanted BM cells from transgenic mice, expressing green fluorescent protein under the control of Kit regulatory elements, into wild-type irradiated recipients. Following haematological reconstitution and MI, CSCs were cultured from cardiac explants to generate 'cardiospheres', a microtissue normally originating in vitro from CSCs. These were all green fluorescent (i.e. BM derived) and contained cells capable of initiating differentiation into cells expressing the cardiac marker Nkx2.5. These findings indicate that, at least in conditions of local acute cardiac damage, BM cells can home into the heart and give rise to cells that share properties of resident Kit(+) CSCs.

Green fluorescent protein transgene driven by Kit regulatory sequences is expressed in hematopoietic stem cells.

BACKGROUND: The transcriptional regulation of stem cell genes is still poorly understood. Kit, encoding the stem cell factor receptor, is a pivotal molecule for multiple types of stem/progenitor cells. We previously generated mouse lines expressing transgenic green fluorescent protein under the control of Kit promoter/first intron regulatory elements, and we demonstrated expression in hematopoietic progenitors. DESIGN AND METHODS: In the present work we investigated whether the transgene is also expressed in hematopoietic stem cells of adult bone marrow and fetal liver. To this purpose, we tested, in long-term repopulating assays, cell fractions expressing different levels of green fluorescent protein within Kit-positive or SLAM-selected populations. RESULTS: The experiments demonstrated transgene expression in both fetal and adult hematopoietic stem cells and indicated that the transgene is transcribed at distinctly lower levels in hematopoietic stem cells than in pluripotent and committed progenitors. CONCLUSIONS: These results, together with previous data, show that a limited subset of DNA sequences drives gene expression in number of stem cell types (hematopoietic stem cells, primordial germ cells, cardiac stem cells). Additionally, our results might help to further improve high level purification of hematopoietic stem cells for experimental purposes. Finally, as the Kit/green fluorescent protein transgene is expressed in multiple stem cell types, our transgenic model provides powerful in vivo system to track these cells during development and tissue regeneration.

Stem Cell-Mediated Exon Skipping of the Dystrophin Gene by the Bystander Effect.

Duchenne muscular dystrophy (DMD) is characterized by the loss of a functional dystrophin protein; the muscles of DMD patients progressively degenerate as a result of mechanical stress during contractions, and the condition eventually leads to premature death. By means antisense oligonucleotides (AONs), it is possible to modulate pre-mRNA splicing eliminating mutated exons and restoring dystrophin open reading frame. To overcome the hurdles in using AONs for therapeutic interventions, we exerted engineered human DMD stem cells with a lentivirus, which permanently and efficiently delivered the cloned AONs. Here we describe for the first time the exosome-mediated release of AONs from engineered human DMD CD133+ stem cells allowing the rescue of murine dystrophin expression. Finally, upon release, AONs could be internalized by host cells suggesting a potential role of exosomes acting as vesicular carriers for DMD gene therapy.

Perspectives of stem cell therapy in Duchenne muscular dystrophy.

Muscular dystrophies are heritable and heterogeneous neuromuscular disorders characterized by the primary wasting of skeletal muscle, usually caused by mutations in the proteins forming the link between the cytoskeleton and the basal lamina. As a result of mutations in the dystrophin gene, Duchenne muscular dystrophy patients suffer from progressive muscle atrophy and an exhaustion of muscular regenerative capacity. No efficient therapies are available. The evidence that adult stem cells were capable of participating in the regeneration of more than their resident organ led to the development of potential stem cell treatments for degenerative disorder. In the present review, we describe the different types of myogenic stem cells and their possible use for the progression of cell therapy in Duchenne muscular dystrophy.

Full-length dysferlin expression driven by engineered human dystrophic blood derived CD133+ stem cells.

The protein dysferlin is abundantly expressed in skeletal and cardiac muscles, where its main function is membrane repair. Mutations in the dysferlin gene are involved in two autosomal recessive muscular dystrophies: Miyoshi myopathy and limb-girdle muscular dystrophy type 2B. Development of effective therapies remains a great challenge. Strategies to repair the dysferlin gene by skipping mutated exons, using antisense oligonucleotides (AONs), may be suitable only for a subset of mutations, while cell and gene therapy can be extended to all mutations. AON-treated blood-derived CD133+ stem cells isolated from patients with Miyoshi myopathy led to partial dysferlin reconstitution in vitro but failed to express dysferlin after intramuscular transplantation into scid/blAJ dysferlin null mice. We thus extended these experiments producing the full-length dysferlin mediated by a lentiviral vector in blood-derived CD133+ stem cells isolated from the same patients. Transplantation of engineered blood-derived CD133+ stem cells into scid/blAJ mice resulted in sufficient dysferlin expression to correct functional deficits in skeletal muscle membrane repair. Our data suggest for the first time that lentivirus-mediated delivery of full-length dysferlin in stem cells isolated from Miyoshi myopathy patients could represent an alternative therapeutic approach for treatment of dysferlinopathies.

The role of stem cells in muscular dystrophies.

Muscular dystrophies are heterogeneous neuromuscular disorders of inherited origin, including Duchenne muscular dystrophy (DMD). Cell-based therapies were used to promote muscle regeneration with the hope that the host cells repopulated the muscle and improved muscle function and pathology. Stem cells were preferable for therapeutic applications, due to their capacity of self-renewal and differentiative potential. In the last years, encouraging results were obtained with adult stem cells to treat muscular dystrophies. Adult stem cells were found into various tissues of the body and they were able to maintain, generate, and replace terminally differentiated cells within their own specific tissue because of cell turnover or tissue injury. Moreover, it became clear that these cells could participate into regeneration of more than just their resident organ. Here, we described multiple types of muscle and non muscle-derived myogenic stem cells, their characterization and their possible use to treat muscular dystrophies. We also underlined that most promising possibility for the management and therapy of DMD is a combination of different approaches, such as gene and stem cell therapy.

Hmgb3 is regulated by microRNA-206 during muscle regeneration.

BACKGROUND: MicroRNAs (miRNAs) have been recently involved in most of human diseases as targets for potential strategies to rescue the pathological phenotype. Since the skeletal muscle is a spread-wide highly differentiated and organized tissue, rescue of severely compromised muscle still remains distant from nowadays. For this reason, we aimed to identify a subset of miRNAs major involved in muscle remodelling and regeneration by analysing the miRNA-profile of single fibres isolated from dystrophic muscle, which was here considered as a model of chronic damage. METHODOLOGY/PRINCIPAL FINDINGS: The miRNA-signature associated to regenerating (newly formed) and remodelling (resting) fibres was investigated in animal models of muscular dystrophies and acute damage, in order to distinguish which miRNAs are primary related to muscle regeneration. In this study we identify fourteen miRNAs associated to dystrophic fibres responsible for muscle regeneration and remodelling, and confirm over-expression of the previously identified regeneration-associated myomiR-206. In particular, a functional binding site for myomiR-206 was identified and validated in the 3'untranslated region (3'UTR) of an X-linked member of a family of sequence independent chromatin-binding proteins (Hmgb3) that is preferentially expressed in hematopoietic stem cells. During regeneration of single muscle fibres, Hmgb3 messenger RNA (mRNA) and protein expression was gradually reduced, concurrent with the up-regulation of miR-206. CONCLUSION/SIGNIFICANCE: Our results elucidate a negative feedback circuit in which myomiR-206 represses Hmgb3 expression to modulate the regeneration of single muscle fibres after acute and chronic muscle damage. These findings suggest that myomiR-206 may be a potential therapeutic target in muscle diseases.

Expression of CD20 reveals a new store-operated calcium entry modulator in skeletal muscle.

Among the scarce available data about the biological role of the membrane protein CD20, there is some evidence that this protein functions as a store-operated Ca(2+) channel and/or regulates transmembrane Ca(2+) trafficking. Recent findings indicate that store-operated Ca(2+) entry (SOCE) plays a central role in skeletal muscle function and development, but there remain a number of unresolved issues relating to SOCE modulation in this tissue. Here we describe CD20 expression in skeletal muscle, verifying its membrane localization in myoblasts and adult muscle fibers. Additionally, we show that inhibition of CD20 through antibody binding or gene silencing resulted in specific impairment of SOCE in C2C12 myoblasts. Our results provide novel insights into the CD20 expression pattern, and suggest that functional CD20 is required for SOCE to consistently occur in C2C12 myoblasts. These findings may contribute to future identification of mechanisms and molecules involved in the fine regulation of store-operated Ca(2+) entry in skeletal muscle.