Cripto shapes macrophage plasticity and restricts EndMT in injured and diseased skeletal muscle.

Macrophages are characterized by a high plasticity in response to changes in tissue microenvironment, which allows them to acquire different phenotypes and to exert essential functions in complex processes, such as tissue regeneration. Here, we report that the membrane protein Cripto plays a key role in shaping macrophage plasticity in skeletal muscle during regeneration and disease. Conditional deletion of Cripto in the myeloid lineage (CriptoMy-LOF ) perturbs MP plasticity in acutely injured muscle and in mouse models of Duchenne muscular dystrophy (mdx). Specifically, CriptoMy-LOF macrophages infiltrate the muscle, but fail to properly expand as anti-inflammatory CD206+ macrophages, which is due, at least in part, to aberrant activation of TGFß/Smad signaling. This reduction in macrophage plasticity disturbs vascular remodeling by increasing Endothelial-to-Mesenchymal Transition (EndMT), reduces muscle regenerative potential, and leads to an exacerbation of the dystrophic phenotype. Thus, in muscle-infiltrating macrophages, Cripto is required to promote the expansion of the CD206+ anti-inflammatory macrophage type and to restrict the EndMT process, providing a direct functional link between this macrophage population and endothelial cells.

Repeat Screening Outcomes with Digital Breast Tomosynthesis Plus Synthetic Mammography for Breast Cancer Detection: Results from the Prospective Verona Pilot Study.

Background Few results are available about subsequent outcomes after screening with digital breast tomosynthesis (DBT). Purpose To compare the diagnostic accuracy of a screening round with DBT plus synthetic mammography (SM) (hereafter, DBT+SM) and the repeat screening round with DBT with SM (hereafter, DBT+SM) or full-field digital mammography (FFDM) with FFDM screening. Materials and Methods This prospective study (Verona Pilot Study, clinical trial identification: 2015/1238) included women screened with DBT+SM between April 2015 and March 2017 and rescreened with DBT+SM or FFDM between April 2017 and March 2019. Screening performance (recall rate, cancer detection rate [CDR], and positive predictive value of recall [PPV1]) was compared with that obtained from 28 680 women screened with FFDM between 2013 and 2014 (control group). Cancer stages were compared between modalities and screening rounds. A χ2 test was used to evaluate differences. P < .05 was indicative of a statistically significant difference. Results Of 34 638 women enrolled, 32 870 (median age, 58 years; age range, 52-71 years) underwent repeat screening-16 198 with DBT+SM and 16 672 with FFDM. The CDR was higher for repeat screening with DBT+SM than for the control group with FFDM (8.1 per 1000 women screened vs 4.5 per 1000 women screened, respectively; P < .01) and was not significantly lower for repeat screening with FFDM (3.5 per 1000 women screened vs 4.5 per 1000 women screened, respectively; P = .11). Compared with the control group, there was no difference in the recall rate at repeat screening with both DBT+SM (3.71% vs 3.40%, respectively; P = .10) and FFDM (3.71% vs 3.69%, P = .92), whereas PPV1 was higher only when repeat screening was performed with DBT+SM (23.8% vs 12.0%, P < .01). At repeat screening, the proportion of cancers stage II or higher was 14.5% (19 of 131 cancers) with DBT+SM and 8.5% (five of 59 cancers) with FFDM, both of which were lower than the proportion in the control group with FFDM (30 of 110 cancers, 27.3%) (P ≤ .01). Conclusion At repeat screening, digital breast tomosynthesis plus synthetic mammography depicted more cancers than full-field digital mammography (FFDM) and found a lower number of stage II cancers compared with FFDM. © RSNA, 2020 See also the editorial by Bae in this issue.

Macrophages Guard Endothelial Lineage by Hindering Endothelial-to-Mesenchymal Transition: Implications for the Pathogenesis of Systemic Sclerosis.

The signals that control endothelial plasticity in inflamed tissues have only been partially characterized. For example, it has been shown that inadequate vasculogenesis in systemic sclerosis (SSc) has been associated with an endothelial defect. We used a genetic lineage tracing model to investigate whether endothelial cells die or change phenotypically after fibrosis induction and whether signals released by cells of the innate immune system and in the blood of patients influence their commitment. We observed that in the lineage-tracing transgenic mice Cdh5-CreERT2::R26R-EYFP, endothelial-derived cells (EdCs) underwent fibrosis after treatment with bleomycin, and EdCs retrieved from the lung showed expression of endothelial-to-mesenchymal transition (EndoMT) markers. Liposome-encapsulated clodronate was used to assess macrophage impact on EdCs. Clodronate treatment affected the number of alternatively activated macrophages in the lung, with upregulated expression of EndoMT markers in lung EdCs. Endothelial fate and function were investigated in vitro upon challenge with serum signals from SSc patients or released by activated macrophages. Sera of SSc patients with anti-Scl70 Abs, at higher risk of visceral organ fibrosis, induced EndoMT and jeopardized endothelial function. In conclusion, EdCs in SSc might be defective because of commitment to a mesenchymal fate, which is sustained by soluble signals in the patient's blood. Macrophages contribute to preserve the endothelial identity of precursor cells. Altered macrophage-dependent plasticity of EdCs could contribute to link vasculopathy with fibrosis.

Comparison of breast cancers detected in the Verona screening program following transition to digital breast tomosynthesis screening with cancers detected at digital mammography screening.

BACKGROUND: The Verona population-based breast cancer (BC) screening program provides biennial mammography to women aged 50-69 years. Based on emerging evidence of enhanced detection, the program transitioned to digital breast tomosynthesis (DBT) screening. METHODS: This is a prospective pilot evaluation of DBT with synthesised 2D mammography screening implemented during April 2015-March 2017; the rate and characteristics of cancers detected at DBT screening were compared with those detected at the preceding digital mammography (DM) screening round (April 2013-March 2015) in the same screening program. Distribution of imaging and tumour characteristics were compared. RESULTS: Amongst 34,071 women screened in the Verona DBT pilot, 315 BCs were detected; 153 BCs were detected amongst 29,360 women in the DM screening round. Estimated CDRs were 9.2/1000 (95% CI 8.3-10.3) DBT screens versus 5.2/1000 (95% CI 4.4-6.1) DM screens, P < 0.001. Statistically significant differences were found in the distribution of whether recall by one/both screen readers (more BCs recalled by both readers at DBT than DM); whether detected on one/two views (higher proportion detected on only one view at DBT than DM); type of radiological lesions; tumour stage, pT and histological categories (lower proportion of DCIS/pTis, higher proportions of pT1a and pT1b, and higher proportion of invasive cancers of special types, at DBT than DM); and tumour grade (higher proportion of grade I at DBT than DM). There were no differences in distributions of nodal and hormone receptor (ER/PR) status. CONCLUSIONS: Our findings provide early insights into the extent that transitioning to DBT screening may modify the characteristics of screen-detected breast cancer to inform discussion regarding pros and cons of DBT screening; although our data provide some reassurance that DBT does not increase the proportion of screen-detected DCIS, they highlight mixed findings on comparative tumour characteristics, suggesting a potential for enhancing screening benefit and possibly also over-diagnosis from DBT screening.

Digital Breast Tomosynthesis with Synthesized Two-Dimensional Images versus Full-Field Digital Mammography for Population Screening: Outcomes from the Verona Screening Program.

Purpose To examine the outcomes of a breast cancer screening program based on digital breast tomosynthesis (DBT) plus synthesized two-dimensional (2D) mammography compared with those after full-field digital mammography (FFDM). Materials and Methods This prospective study included 16 666 asymptomatic women aged 50-69 years who were recruited in April 2015 through March 2016 for DBT plus synthetic 2D screening in the Verona screening program. A comparison cohort of women screened with FFDM (n = 14 423) in the previous year was included. Screening detection measures for the two groups were compared by calculating the proportions associated with each outcome, and the relative rates (RRs) were estimated with multivariate logistic regression. Results Cancer detection rate (CDR) for DBT plus synthetic 2D imaging was 9.30 per 1000 screening examinations versus 5.41 per 1000 screening examinations with FFDM (RR, 1.72; 95% confidence interval [CI]: 1.30, 2.29). CDR was significantly higher in patients screened with DBT plus synthetic 2D imaging than in those screened with FFDM among women classified as having low breast density (RR, 1.53; 95% CI: 1.13, 2.10) or high breast density (RR, 2.86; 95% CI: 1.42, 6.25). The positive predictive value (PPV) for recall was almost doubled with DBT plus synthetic 2D imaging: 23.3% versus 12.9% of recalled patients who were screened with FFDM (RR, 1.81; 95% CI: 1.34, 2.47). The recall rate was similar between groups (RR, 0.95; 95% CI: 0.84, 1.06), whereas the recall rate with invasive assessment was higher for DBT plus synthetic 2D imaging than for FFDM (RR, 1.93; 95% CI: 1.31, 2.03). The mean number of screening studies interpreted per hour was significantly lower for screening examinations performed with DBT plus synthetic 2D imaging (38.5 screens per hour) than with FFDM (60 screens per hour) (P < .001). Conclusion DBT plus synthetic 2D imaging increases CDRs with recall rates comparable to those of FFDM. DBT plus synthetic 2D imaging increased image reading time and the time needed for invasive assessments. © RSNA, 2017.

Hemogenic endothelium generates mesoangioblasts that contribute to several mesodermal lineages in vivo.

The embryonic endothelium is a known source of hematopoietic stem cells. Moreover, vessel-associated progenitors/stem cells with multilineage mesodermal differentiation potential, such as the 'embryonic mesoangioblasts', originate in vitro from the endothelium. Using a genetic lineage tracing approach, we show that early extra-embryonic endothelium generates, in a narrow time-window and prior to the hemogenic endothelium in the major embryonic arteries, hematopoietic cells that migrate to the embryo proper, and are subsequently found within the mesenchyme. A subpopulation of these cells, distinct from embryonic macrophages, co-expresses mesenchymal and hematopoietic markers. In addition, hemogenic endothelium-derived cells contribute to skeletal and smooth muscle, and to other mesodermal cells in vivo, and display features of embryonic mesoangioblasts in vitro. Therefore, we provide new insights on the distinctive characteristics of the extra-embryonic and embryonic hemogenic endothelium, and we identify the putative in vivo counterpart of embryonic mesoangioblasts, suggesting their identity and developmental ontogeny.

Requirement of inducible nitric oxide synthase for skeletal muscle regeneration after acute damage.

Adult skeletal muscle regeneration results from activation, proliferation, and fusion of muscle stem cells, such as myogenic precursor cells. Macrophages are consistently present in regenerating skeletal muscles and participate into the repair process. The signals involved in the cross-talk between various macrophage populations and myogenic precursor cells have been only partially identified. In this study, we show a key role of inducible NO synthase (iNOS), expressed by classically activated macrophages in the healing of skeletal muscle. We found that, after sterile injury, iNOS expression is required for effective regeneration of the tissue, as myogenic precursor cells in the muscle of injured iNOS(-/-) mice fail to proliferate and differentiate. We also found that iNOS modulates inflammatory cell recruitment: damaged muscles of iNOS(-/-) animals express significantly higher levels of chemokines such as MIP2, MCP1, MIP-1α, and MCP1, and display more infiltrating neutrophils after injury and a persistence of macrophages at later time points. Finally, we found that iNOS expression in the injured muscle is restricted to infiltrating macrophages. To our knowledge, these data thus provide the first evidence that iNOS expression by infiltrating macrophages contributes to muscle regeneration, revealing a novel mechanism of inflammation-dependent muscle healing.

Nitric oxide drives embryonic myogenesis in chicken through the upregulation of myogenic differentiation factors.

The muscle-specific variant of neuronal nitric oxide (NO) synthase (NOS-I), is developmentally regulated in mouse suggesting a role of NO during myogenesis. In chick embryo, a good model of development, we found that the expression of NOS-I is up-regulated, but only in the early phase of development. Through a pharmacological intervention in ovo we found that NO signalling plays a relevant role during embryonic development. The inhibition of NOS-I decreased the growth of embryo, in particular of muscle tissue, while the restoring of physiological NO levels, via administration of a NO donor, reversed this effect. We found a selective action of NO, produced by NOS-I, on regulatory factors involved in myogenic differentiation in the early phase of chick embryo development: inhibition of NO generation leads to a decreased expression of the Myocyte enhancer factor 2a (Mef2a), Mef2c, Myogenin and Myosin, which was reversed by the administration of a NO donor. NO had no effects on Myf5 and MyoD, the myogenic regulatory factors necessary for myogenic determination. The action of NO on the myogenic regulatory factors was mediated via generation of cyclic GMP (cGMP) and activation of the cGMP-dependent protein kinase G (PKG). Finally we found in myoblasts in vitro that the activation of Mef2c was the key event mediating the NO-induced modulation of myogenesis. Our results identify NO produced by NOS-I as a key messenger in the early phase of embryonic development of chicken, acting as a critical determinant of myogenesis through its physiological cGMP/PKG pathway.

ADAP2 in heart development: a candidate gene for the occurrence of cardiovascular malformations in NF1 microdeletion syndrome.

BACKGROUND: Cardiovascular malformations have a higher incidence in patients with NF1 microdeletion syndrome compared to NF1 patients with intragenic mutation, presumably owing to haploinsufficiency of one or more genes included in the deletion interval and involved in heart development. In order to identify which genes could be responsible for cardiovascular malformations in the deleted patients, we carried out expression studies in mouse embryos and functional studies in zebrafish. METHODS AND RESULTS: The expression analysis of three candidate genes included in the NF1 deletion interval, ADAP2, SUZ12 and UTP6, performed by in situ hybridisation, showed the expression of ADAP2 murine ortholog in heart during fundamental phases of cardiac morphogenesis. In order to investigate the role of ADAP2 in cardiac development, we performed loss-of-function experiments of zebrafish ADAP2 ortholog, adap2, by injecting two different morpholino oligos (adap2-MO and UTR-adap2-MO). adap2-MOs-injected embryos (morphants) displayed in vivo circulatory and heart shape defects. The molecular characterisation of morphants with cardiac specific markers showed that the injection of adap2-MOs causes defects in heart jogging and looping. Additionally, morphological and molecular analysis of adap2 morphants demonstrated that the loss of adap2 function leads to defective valvulogenesis, suggesting a correlation between ADAP2 haploinsufficiency and the occurrence of valve defects in NF1-microdeleted patients. CONCLUSIONS: Overall, our findings indicate that ADAP2 has a role in heart development, and might be a reliable candidate gene for the occurrence of cardiovascular malformations in patients with NF1 microdeletion and, more generally, for the occurrence of a subset of congenital heart defects.

Cripto regulates skeletal muscle regeneration and modulates satellite cell determination by antagonizing myostatin.

Skeletal muscle regeneration mainly depends on satellite cells, a population of resident muscle stem cells. However, our understanding of the molecular mechanisms underlying satellite cell activation is still largely undefined. Here, we show that Cripto, a regulator of early embryogenesis, is a novel regulator of muscle regeneration and satellite cell progression toward the myogenic lineage. Conditional inactivation of cripto in adult satellite cells compromises skeletal muscle regeneration, whereas gain of function of Cripto accelerates regeneration, leading to muscle hypertrophy. Moreover, we provide evidence that Cripto modulates myogenic cell determination and promotes proliferation by antagonizing the TGF-ß ligand myostatin. Our data provide unique insights into the molecular and cellular basis of Cripto activity in skeletal muscle regeneration and raise previously undescribed implications for stem cell biology and regenerative medicine.

Gastric cancer does not affect the expression of atrophy-related genes in human skeletal muscle.

INTRODUCTION: We evaluated the gene expression levels of atrogin-1, MuRF1, myostatin, follistatin, activin A, and inhibin alpha in skeletal muscle samples of patients with gastric cancer and controls. METHODS: We studied 38 cancer patients and 12 controls who underwent surgery for gastric adenocarcinoma and benign abdominal diseases, respectively. A biopsy specimen was obtained from the rectus abdominis muscle from all participants. The relative gene expression of atrogin-1, MuRF1, myostatin, follistatin, activin A, and inhibin alpha was determined by quantitative real-time polymerase chain reaction analysis. RESULTS: Atrogin-1 and MuRF1 mRNA expression was similar between cancer patients and controls and was unaffected by the disease stage or the severity of body weight loss. Transcript levels of myostatin and follistatin did not differ between cases and controls and were similar across disease stages and categories of weight loss. Finally, no differences were detected in activin A and inhibin alpha gene expression between cancer patients and controls. CONCLUSIONS: In skeletal muscle, the gene expression of atrogin-1, MuRF1, myostatin, follistatin, activin A, and inhibin alpha is not affected by the presence of cancer. The expression of atrophy-related genes is unaffected by the disease stage and the degree of weight loss.

Transplanted mesoangioblasts require macrophage IL-10 for survival in a mouse model of muscle injury.

The aim of this study was to verify whether macrophages influence the fate of transplanted mesoangioblasts--vessel-associated myogenic precursors--in a model of sterile toxin-induced skeletal muscle injury. We have observed that in the absence of macrophages, transplanted mesoangioblasts do not yield novel fibers. Macrophages retrieved from skeletal muscles at various times after injury display features that resemble those of immunoregulatory macrophages. Indeed, they secrete IL-10 and express CD206 and CD163 membrane receptors and high amounts of arginase I. We have reconstituted the muscle-associated macrophage population by injecting polarized macrophages before mesoangioblast injection: alternatively activated, immunoregulatory macrophages only support mesoangioblast survival and function. This action depends on the secretion of IL-10 in the tissue. Our results reveal an unanticipated role for tissue macrophages in mesoangioblast function. Consequently, the treatment of muscle disorders with mesoangioblasts should take into consideration coexisting inflammatory pathways, whose activation may prove crucial for its success.

Integration of 3D digital mammography with tomosynthesis for population breast-cancer screening (STORM): a prospective comparison study.

BACKGROUND: Digital breast tomosynthesis with 3D images might overcome some of the limitations of conventional 2D mammography for detection of breast cancer. We investigated the effect of integrated 2D and 3D mammography in population breast-cancer screening. METHODS: Screening with Tomosynthesis OR standard Mammography (STORM) was a prospective comparative study. We recruited asymptomatic women aged 48 years or older who attended population-based breast-cancer screening through the Trento and Verona screening services (Italy) from August, 2011, to June, 2012. We did screen-reading in two sequential phases-2D only and integrated 2D and 3D mammography-yielding paired data for each screen. Standard double-reading by breast radiologists determined whether to recall the participant based on positive mammography at either screen read. Outcomes were measured from final assessment or excision histology. Primary outcome measures were the number of detected cancers, the number of detected cancers per 1000 screens, the number and proportion of false positive recalls, and incremental cancer detection attributable to integrated 2D and 3D mammography. We compared paired binary data with McNemar's test. FINDINGS: 7292 women were screened (median age 58 years [IQR 54-63]). We detected 59 breast cancers (including 52 invasive cancers) in 57 women. Both 2D and integrated 2D and 3D screening detected 39 cancers. We detected 20 cancers with integrated 2D and 3D only versus none with 2D screening only (p<0.0001). Cancer detection rates were 5.3 cancers per 1000 screens (95% CI 3.8-7.3) for 2D only, and 8.1 cancers per 1000 screens (6.2-10.4) for integrated 2D and 3D screening. The incremental cancer detection rate attributable to integrated 2D and 3D mammography was 2.7 cancers per 1000 screens (1.7-4.2). 395 screens (5.5%; 95% CI 5.0-6.0) resulted in false positive recalls: 181 at both screen reads, and 141 with 2D only versus 73 with integrated 2D and 3D screening (p<0.0001). We estimated that conditional recall (positive integrated 2D and 3D mammography as a condition to recall) could have reduced false positive recalls by 17.2% (95% CI 13.6-21.3) without missing any of the cancers detected in the study population. INTERPRETATION: Integrated 2D and 3D mammography improves breast-cancer detection and has the potential to reduce false positive recalls. Randomised controlled trials are needed to compare integrated 2D and 3D mammography with 2D mammography for breast cancer screening. FUNDING: National Breast Cancer Foundation, Australia; National Health and Medical Research Council, Australia; Hologic, USA; Technologic, Italy.

Cellular interactions and microenvironment dynamics in skeletal muscle regeneration and disease.

Skeletal muscle regeneration relies on the intricate interplay of various cell populations within the muscle niche-an environment crucial for regulating the behavior of muscle stem cells (MuSCs) and ensuring postnatal tissue maintenance and regeneration. This review delves into the dynamic interactions among key players of this process, including MuSCs, macrophages (MPs), fibro-adipogenic progenitors (FAPs), endothelial cells (ECs), and pericytes (PCs), each assuming pivotal roles in orchestrating homeostasis and regeneration. Dysfunctions in these interactions can lead not only to pathological conditions but also exacerbate muscular dystrophies. The exploration of cellular and molecular crosstalk among these populations in both physiological and dystrophic conditions provides insights into the multifaceted communication networks governing muscle regeneration. Furthermore, this review discusses emerging strategies to modulate the muscle-regenerating niche, presenting a comprehensive overview of current understanding and innovative approaches.

Nitric oxide sustains long-term skeletal muscle regeneration by regulating fate of satellite cells via signaling pathways requiring Vangl2 and cyclic GMP.

Satellite cells are myogenic precursors that proliferate, activate, and differentiate on muscle injury to sustain the regenerative capacity of adult skeletal muscle; in this process, they self-renew through the return to quiescence of the cycling progeny. This mechanism, while efficient in physiological conditions does not prevent exhaustion of satellite cells in pathologies such as muscular dystrophy where numerous rounds of damage occur. Here, we describe a key role of nitric oxide, an important signaling molecule in adult skeletal muscle, on satellite cells maintenance, studied ex vivo on isolated myofibers and in vivo using the α-sarcoglycan null mouse model of dystrophy and a cardiotoxin-induced model of repetitive damage. Nitric oxide stimulated satellite cells proliferation in a pathway dependent on cGMP generation. Furthermore, it increased the number of Pax7(+)/Myf5(-) cells in a cGMP-independent pathway requiring enhanced expression of Vangl2, a member of the planar cell polarity pathway involved in the Wnt noncanonical pathway. The enhanced self-renewal ability of satellite cells induced by nitric oxide is sufficient to delay the reduction of the satellite cell pool during repetitive acute and chronic damages, favoring muscle regeneration; in the α-sarcoglycan null dystrophic mouse, it also slowed disease progression persistently. These results identify nitric oxide as a key messenger in satellite cells maintenance, expand the significance of the Vangl2-dependent Wnt noncanonical pathway in myogenesis, and indicate novel strategies to optimize nitric oxide-based therapies for muscular dystrophy.

SOX3 is required during the formation of the hypothalamo-pituitary axis.

The pituitary develops from the interaction of the infundibulum, a region of the ventral diencephalon, and Rathke's pouch, a derivative of oral ectoderm. Postnatally, its secretory functions are controlled by hypothalamic neurons, which also derive from the ventral diencephalon. In humans, mutations affecting the X-linked transcription factor SOX3 are associated with hypopituitarism and mental retardation, but nothing is known of their etiology. We find that deletion of Sox3 in mice leads to defects of pituitary function and of specific central nervous system (CNS) midline structures. Cells in the ventral diencephalon, where Sox3 is usually highly expressed, have altered properties in mutant embryos, leading to abnormal development of Rathke's pouch, which does not express the gene. Pituitary and hypothalamic defects persist postnatally, and SOX3 may also function in a subset of hypothalamic neurons. This study shows how sensitive the pituitary is to subtle developmental defects and how one gene can act at several levels in the hypothalamic-pituitary axis.

Hematopoietic Stem Cell (HSC)-Independent Progenitors Are Susceptible to Mll-Af9-Induced Leukemic Transformation.

Infant acute myeloid leukemia (AML) is a heterogeneous disease, genetically distinct from its adult counterpart. Chromosomal translocations involving the KMT2A gene (MLL) are especially common in affected infants of less than 1 year of age, and are associated with a dismal prognosis. While these rearrangements are likely to arise in utero, the cell of origin has not been conclusively identified. This knowledge could lead to a better understanding of the biology of the disease and support the identification of new therapeutic vulnerabilities. Over the last few years, important progress in understanding the dynamics of fetal hematopoiesis has been made. Several reports have highlighted how hematopoietic stem cells (HSC) provide little contribution to fetal hematopoiesis, which is instead largely sustained by HSC-independent progenitors. Here, we used conditional Cre-Lox transgenic mouse models to engineer the Mll-Af9 translocation in defined subsets of embryonic hematopoietic progenitors. We show that embryonic hematopoiesis is generally permissive for Mll-Af9-induced leukemic transformation. Surprisingly, the selective introduction of Mll-Af9 in HSC-independent progenitors generated a transplantable myeloid leukemia, whereas it did not when introduced in embryonic HSC-derived cells. Ex vivo engineering of the Mll-Af9 rearrangement in HSC-independent progenitors using a CRISPR/Cas9-based approach resulted in the activation of an aberrant myeloid-biased self-renewal program. Overall, our results demonstrate that HSC-independent hematopoietic progenitors represent a permissive environment for Mll-Af9-induced leukemic transformation, and can likely act as cells of origin of infant AML.

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.

Nitric oxide donor and non steroidal anti inflammatory drugs as a therapy for muscular dystrophies: evidence from a safety study with pilot efficacy measures in adult dystrophic patients.

This open-label, single centre pilot study was designed to evaluate safety and tolerability of the combination of the drugs isosorbide dinitrate, a nitric oxide donor, and ibuprofen, a non steroid anti-inflammatory drug, in a cohort of adult dystrophic patients (Duchenne, Becker and Limb-Girdle Muscular Dystrophy). Seventy-one patients were recruited: 35, treated with the drug combination for 12 months, and 36 untreated. Safety and adverse events were assessed by reported signs and symptoms, physical examinations, blood tests, cardiac and respiratory function tests. Exploratory outcomes measure, such as the motor function measure scale, were also applied. Good safety and tolerability profiles of the long-term co-administration of the drugs were demonstrated. Few and transient side effects (i.e. headache and low blood pressure) were reported. Additionally, exploratory outcomes measures were feasible in all the disease population studied and evidenced a trend towards amelioration that reached statistical significance in one dimension of the MFM scale. Systemic administration of ibuprofen and isosorbide dinitrate provides an adequate safety margin for clinical studies aimed at assessing efficacy.

One Size Does Not Fit All: Heterogeneity in Developmental Hematopoiesis.

Our knowledge of the complexity of the developing hematopoietic system has dramatically expanded over the course of the last few decades. We now know that, while hematopoietic stem cells (HSCs) firmly reside at the top of the adult hematopoietic hierarchy, multiple HSC-independent progenitor populations play variegated and fundamental roles during fetal life, which reflect on adult physiology and can lead to disease if subject to perturbations. The importance of obtaining a high-resolution picture of the mechanisms by which the developing embryo establishes a functional hematopoietic system is demonstrated by many recent indications showing that ontogeny is a primary determinant of function of multiple critical cell types. This review will specifically focus on exploring the diversity of hematopoietic stem and progenitor cells unique to embryonic and fetal life. We will initially examine the evidence demonstrating heterogeneity within the hemogenic endothelium, precursor to all definitive hematopoietic cells. Next, we will summarize the dynamics and characteristics of the so-called "hematopoietic waves" taking place during vertebrate development. For each of these waves, we will define the cellular identities of their components, the extent and relevance of their respective contributions as well as potential drivers of heterogeneity.