Anna Innocenzi

Mesoangioblast stem cells ameliorate muscle function in dystrophic dogs.

Duchenne muscular dystrophy remains an untreatable genetic disease that severely limits motility and life expectancy in affected children. The only animal model specifically reproducing the alterations in the dystrophin gene and the full spectrum of human pathology is the golden retriever dog model. Affected animals present a single mutation in intron 6, resulting in complete absence of the dystrophin protein, and early and severe muscle degeneration with nearly complete loss of motility and walking ability. Death usually occurs at about 1 year of age as a result of failure of respiratory muscles. Here we report that intra-arterial delivery of wild-type canine mesoangioblasts (vessel-associated stem cells) results in an extensive recovery of dystrophin expression, normal muscle morphology and function (confirmed by measurement of contraction force on single fibres). The outcome is a remarkable clinical amelioration and preservation of active motility. These data qualify mesoangioblasts as candidates for future stem cell therapy for Duchenne patients.

Pericytes resident in postnatal skeletal muscle differentiate into muscle fibres and generate satellite cells

Skeletal muscle fibres form by fusion of mesoderm progenitors called myoblasts. After birth, muscle fibres do not increase in number but continue to grow in size because of fusion of satellite cells, the postnatal myogenic cells, responsible for muscle growth and regeneration. Numerous studies suggest that, on transplantation, non-myogenic cells also may contribute to muscle regeneration. However, there is currently no evidence that such a contribution represents a natural developmental option of these non-myogenic cells, rather than a consequence of experimental manipulation resulting in cell fusion. Here we show that pericytes, transgenically labelled with an inducible Alkaline Phosphatase CreERT2, but not endothelial cells, fuse with developing myofibres and enter the satellite cell compartment during unperturbed postnatal development. This contribution increases significantly during acute injury or in chronically regenerating dystrophic muscle. These data show that pericytes, resident in small vessels of skeletal muscle, contribute to its growth and regeneration during postnatal life.

Nitric oxide release combined with nonsteroidal antiinflammatory activity prevents muscular dystrophy pathology and enhances stem cell therapy

Duchenne muscular dystrophy is a relatively common disease that affects skeletal muscle, leading to progressive paralysis and death. There is currently no resolutive therapy. We have developed a treatment in which we combined the effects of nitric oxide with nonsteroidal antiinflammatory activity by using HCT 1026, a nitric oxide-releasing derivative of flurbiprofen. Here, we report the results of long-term (1-year) oral treatment with HCT 1026 of two murine models for limb girdle and Duchenne muscular dystrophies (α-sarcoglycan-null and mdx mice). In both models, HCT 1026 significantly ameliorated the morphological, biochemical, and functional phenotype in the absence of secondary effects, efficiently slowing down disease progression. HCT 1026 acted by reducing inflammation, preventing muscle damage, and preserving the number and function of satellite cells. HCT 1026 was significantly more effective than the corticosteroid prednisolone, which was analyzed in parallel. As an additional beneficial effect, HCT 1026 enhanced the therapeutic efficacy of arterially delivered donor stem cells, by increasing 4-fold their ability to migrate and reconstitute muscle fibers. The therapeutic strategy we propose is not selective for a subset of mutations; it provides ground for immediate clinical experimentation with HCT 1026 alone, which is approved for use in humans; and it sets the stage for combined therapies with donor or autologous, genetically corrected stem cells.

Mesoangioblasts, Vessel-Associated Multipotent Stem Cells, Repair the Infarcted Heart by Multiple Cellular Mechanisms A Comparison With Bone Marrow Progenitors, Fibroblasts, and Endothelial Cells

Objective—To test the potential of mesoangioblasts (Mabs) in reducing postischemic injury in comparison with bone marrow progenitor cells (BMPCs), fibroblasts (Fbs), and embryonic stem cell–derived endothelial cells (ECs), and to identify putative cellular protective mechanisms. Methods and Results—Cells were injected percutaneously in the left ventricular (LV) chamber of C57BL/6 mice, 3 to 6 hours after coronary ligation, and detected in the hearts 2 days and 6 weeks later. Echocardiographic examinations were performed at 6 weeks. LV dilation was reduced and LV shortening fraction was improved with Mabs and BMPCs but not with ECs and Fbs. Donor cell colonization of the host myocardium was modest and predominantly in the smooth muscle layer of vessels. Capillary density was higher in the peripheral infarct area and apoptotic cardiomyocytes were fewer with Mabs and BMPCs. Mabs and BMPCs, but not Fbs or ECs, promoted survival of cultured cardiocytes under low-oxygen in culture. This activity was present in Mab-conditioned medium and could be replaced by a combination of basic fibroblast growth factor (bFGF), insulin-like growth factor (IGF)-1, and hepatocyte growth factor (HGF), all of which are produced by these cells. Conditioned medium from Mabs, but not from Fbs, stimulated proliferation of smooth muscle cells in vitro. Conclusions—Mabs appear as effective as BMPCs in reducing postinfarction LV dysfunction, likely through production of antiapoptotic and angiogenic factors.

Necdin mediates skeletal muscle regeneration by promoting myoblast survival and differentiation.

Regeneration of muscle fibers that are lost during pathological muscle degeneration or after injuries is sustained by the production of new myofibers. An important cell type involved in muscle regeneration is the satellite cell. Necdin is a protein expressed in satellite cell–derived myogenic precursors during perinatal growth. However, its function in myogenesis is not known. We compare transgenic mice that overexpress necdin in skeletal muscle with both wild-type and necdin null mice. After muscle injury the necdin null mice show a considerable defect in muscle healing, whereas mice that overexpress necdin show a substantial increase in myofiber regeneration. We also find that in muscle, necdin increases myogenin expression, accelerates differentiation, and counteracts myoblast apoptosis. Collectively, these data clarify the function and mechanism of necdin in skeletal muscle and show the importance of necdin in muscle regeneration.

Corrigendum: Mesoangioblast stem cells ameliorate muscle function in dystrophic dogs

This corrects the article DOI: 10.1038/nature05282

Bhlhb5 is expressed in the CNS and sensory organs during mouse embryonic development.

Basic loop helix transcription factors have been shown to be implicated in the specification of various cell types, and many are involved in different aspects of neural development. Here we describe the expression of Bhlhb5, belonging to the beta3 subfamily, in mouse embryos ranging from 9 to 16.5dpc. Bhlhb5 is initially detected at 9.5dpc in the neural tube, restricted to longitudinal ventral columns of neurons, extending from the hindbrain to the caudal spinal cord. At later stages the expression is maintained in the central nervous system, in particular in the brain, where it is detected in the outer and more mature layer of the forming cerebral cortex and in the spinal cord. In addition Bhlhb5 is expressed in the developing eye and hair follicles, in the epithelial layer of the cochlea in the developing inner, and in the nasal epithelium.

An evolutionarily acquired genotoxic response discriminates MyoD from Myf5, and differentially regulates hypaxial and epaxial myogenesis

Despite having distinct expression patterns and phenotypes in mutant mice, the myogenic regulatory factors Myf5 and MyoD have been considered to be functionally equivalent. Here, we report that these factors have a different response to DNA damage, due to the presence in MyoD and absence in Myf5 of a consensus site for Abl‐mediated tyrosine phosphorylation that inhibits MyoD activity in response to DNA damage. Genotoxins failed to repress skeletal myogenesis in MyoD‐null embryos; reintroduction of wild‐type MyoD, but not mutant Abl phosphorylation‐resistant MyoD, restored the DNA‐damage‐dependent inhibition of muscle differentiation. Conversely, introduction of the Abl‐responsive phosphorylation motif converts Myf5 into a DNA‐damage‐sensitive transcription factor. Gene‐dosage‐dependent reduction of Abl kinase activity in MyoD‐expressing cells attenuated the DNA‐damage‐dependent inhibition of myogenesis. The presence of a DNA‐damage‐responsive phosphorylation motif in vertebrate, but not in invertebrate MyoD suggests an evolved response to environmental stress, originated from basic helix–loop–helix gene duplication in vertebrate myogenesis.

Erratum: Mesoangioblast stem cells ameliorate muscle function in dystrophic dogs (Nature (2013) 494 (506) DOI: 10.1038/nature11976))

This corrects the article DOI: 10.1038/nature05282

Erratum: Mesoangioblast stem cells ameliorate muscle function in dystrophic dogs (Nature (2006) 444 (574-579) DOI:10.1038/nature05282)

This corrects the article DOI: 10.1038/nature05282