Networking to Optimize Dmd exon 53 Skipping in the Brain of mdx52 Mouse Model

Duchenne muscular dystrophy (DMD) is caused by mutations in the DMD gene that disrupt the open reading frame and thus prevent production of functional dystrophin proteins. Recent advances in DMD treatment, notably exon skipping and AAV gene therapy, have achieved some success aimed at alleviating the symptoms related to progressive muscle damage. However, they do not address the brain comorbidities associated with DMD, which remains a critical aspect of the disease. The mdx52 mouse model recapitulates one of the most frequent genetic pathogenic variants associated with brain involvement in DMD. Deletion of exon 52 impedes expression of two brain dystrophins, Dp427 and Dp140, expressed from distinct promoters. Interestingly, this mutation is eligible for exon skipping strategies aimed at excluding exon 51 or 53 from dystrophin mRNA. We previously showed that exon 51 skipping can restore partial expression of internally deleted yet functional Dp427 in the brain following intracerebroventricular (ICV) injection of antisense oligonucleotides (ASO). This was associated with a partial improvement of anxiety traits, unconditioned fear response, and Pavlovian fear learning and memory in the mdx52 mouse model. In the present study, we investigated in the same mouse model the skipping of exon 53 in order to restore expression of both Dp427 and Dp140. However, in contrast to exon 51, we found that exon 53 skipping was particularly difficult in mdx52 mice and a combination of multiple ASOs had to be used simultaneously to reach substantial levels of exon 53 skipping, regardless of their chemistry (tcDNA, PMO, or 2'MOE). Following ICV injection of a combination of ASO sequences, we measured up to 25% of exon 53 skipping in the hippocampus of treated mdx52 mice, but this did not elicit significant protein restoration. These findings indicate that skipping mouse dystrophin exon 53 is challenging. As such, it has not yet been possible to answer the pertinent question whether rescuing both Dp427 and Dp140 in the brain is imperative to more optimal treatment of neurological aspects of dystrophinopathy.

Different Mouse Models of Nemaline Myopathy Harboring Acta1 Mutations Display Differing Abnormalities Related to Mitochondrial Biology

ACTA1 encodes skeletal muscle-specific α-actin, which polymerizes to form the thin filament of the sarcomere. Mutations in ACTA1 are responsible for approximately 30% of nemaline myopathy (NM) cases. Previous studies of weakness in NM have focused on muscle structure and contractility, but genetic issues alone do not explain the phenotypic heterogeneity observed in patients with NM or NM mouse models. To identify additional biological processes related to NM phenotypic severity, proteomic analysis was performed using muscle protein isolates from wild-type mice in comparison to moderately affected knock-in (KI) Acta1H40Y and the minimally affected transgenic (Tg) ACTA1D286G NM mice. This analysis revealed abnormalities in mitochondrial function and stress-related pathways in both mouse models, supporting an in-depth assessment of mitochondrial biology. Interestingly, evaluating each model in comparison to its wild-type counterpart identified different degrees of mitochondrial abnormality that correlated well with the phenotypic severity of the mouse model. Muscle histology, mitochondrial respiration, electron transport chain function, and mitochondrial transmembrane potential were all normal or minimally affected in the TgACTA1D286G mouse model. In contrast, the more severely affected KI.Acta1H40Y mice displayed significant abnormalities in relation to muscle histology, mitochondrial respirometry, ATP, ADP, and phosphate content, and mitochondrial transmembrane potential. These findings suggest that abnormal energy metabolism is related to symptomatic severity in NM and may constitute a contributor to phenotypic variability and a novel treatment target.

Aberrations in Energetic Metabolism and Stress-Related Pathways Contribute to Pathophysiology in the Neb Conditional Knockout Mouse Model of Nemaline Myopathy

Nemaline myopathy (NM) is a genetically and clinically heterogeneous disease that is diagnosed on the basis of the presence of nemaline rods on skeletal muscle biopsy. Although NM has typically been classified by causative genes, disease severity or prognosis cannot be predicted. The common pathologic end point of nemaline rods (despite diverse genetic causes) and an unexplained range of muscle weakness suggest that shared secondary processes contribute to the pathogenesis of NM. We speculated that these processes could be identified through a proteome-wide interrogation using a mouse model of severe NM in combination with pathway validation and structural/functional analyses. A proteomic analysis was performed using skeletal muscle tissue from the Neb conditional knockout mouse model compared with its wild-type counterpart to identify pathophysiologically relevant biological processes that might impact disease severity or provide new treatment targets. A differential expression analysis and Ingenuity Pathway Core Analysis predicted perturbations in several cellular processes, including mitochondrial dysfunction and changes in energetic metabolism and stress-related pathways. Subsequent structural and functional studies demonstrated abnormal mitochondrial distribution, decreased mitochondrial respiratory function, an increase in mitochondrial transmembrane potential, and extremely low ATP content in Neb conditional knockout muscles relative to wild type. Overall, the findings of these studies support a role for severe mitochondrial dysfunction as a novel contributor to muscle weakness in NM.

Cerebro-spinal fluid glucose and lactate concentrations changes in response to therapies in patIents with primary brain injury: the START-TRIP study

INTRODUCTION

Altered levels of cerebrospinal fluid (CSF) glucose and lactate concentrations are associated with poor outcomes in acute brain injury patients. However, no data on changes in such metabolites consequently to therapeutic interventions are available. The aim of the study was to assess CSF glucose-to-lactate ratio (CGLR) changes related to therapies aimed at reducing intracranial pressure (ICP).

METHODS

A multicentric prospective cohort study was conducted in 12 intensive care units (ICUs) from September 2017 to March 2022. Adult (> 18 years) patients admitted after an acute brain injury were included if an external ventricular drain (EVD) for intracranial pressure (ICP) monitoring was inserted within 24 h of admission. During the first 48-72 h from admission, CGLR was measured before and 2 h after any intervention aiming to reduce ICP ("intervention"). Patients with normal ICP were also sampled at the same time points and served as the "control" group.

RESULTS

A total of 219 patients were included. In the intervention group (n = 115, 53%), ICP significantly decreased and CPP increased. After 2 h from the intervention, CGLR rose in both the intervention and control groups, although the magnitude was higher in the intervention than in the control group (20.2% vs 1.6%; p = 0.001). In a linear regression model adjusted for several confounders, therapies to manage ICP were independently associated with changes in CGLR. There was a weak inverse correlation between changes in ICP and CGRL in the intervention group.

CONCLUSIONS

In this study, CGLR significantly changed over time, regardless of the study group. However, these effects were more significant in those patients receiving interventions to reduce ICP.

Cellular and molecular features of COVID-19 associated ARDS: therapeutic relevance

The severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection can be asymptomatic or cause a disease (COVID-19) characterized by different levels of severity. The main cause of severe COVID-19 and death is represented by acute (or acute on chronic) respiratory failure and acute respiratory distress syndrome (ARDS), often requiring hospital admission and ventilator support.The molecular pathogenesis of COVID-19-related ARDS (by now termed c-ARDS) is still poorly understood. In this review we will discuss the genetic susceptibility to COVID-19, the pathogenesis and the local and systemic biomarkers correlated with c-ARDS and the therapeutic options that target the cell signalling pathways of c-ARDS.

Investigating the Impact of Delivery Routes for Exon Skipping Therapies in the CNS of DMD Mouse Models

Nucleic acid-based therapies have demonstrated great potential for the treatment of monogenetic diseases, including neurologic disorders. To date, regulatory approval has been received for a dozen antisense oligonucleotides (ASOs); however, these chemistries cannot readily cross the blood–brain barrier when administered systemically. Therefore, an investigation of their potential effects within the central nervous system (CNS) requires local delivery. Here, we studied the brain distribution and exon-skipping efficacy of two ASO chemistries, PMO and tcDNA, when delivered to the cerebrospinal fluid (CSF) of mice carrying a deletion in exon 52 of the dystrophin gene, a model of Duchenne muscular dystrophy (DMD). Following intracerebroventricular (ICV) delivery (unilateral, bilateral, bolus vs. slow rate, repeated via cannula or very slow via osmotic pumps), ASO levels were quantified across brain regions and exon 51 skipping was evaluated, revealing that tcDNA treatment invariably generates comparable or more skipping relative to that with PMO, even when the PMO was administered at higher doses. We also performed intra-cisterna magna (ICM) delivery as an alternative route for CSF delivery and found a biased distribution of the ASOs towards posterior brain regions, including the cerebellum, hindbrain, and the cervical part of the spinal cord. Finally, we combined both ICV and ICM injection methods to assess the potential of an additive effect of this methodology in inducing efficient exon skipping across different brain regions. Our results provide useful insights into the local delivery and associated efficacy of ASOs in the CNS in mouse models of DMD. These findings pave the way for further ASO-based therapy application to the CNS for neurological disease.

Heterogeneity of Ventilation/Perfusion Mismatch at Different Levels of PEEP and in Mechanical Phenotypes of COVID-19 ARDS

BACKGROUND

COVID-19-related ARDS is characterized by severe hypoxemia with initially preserved lung compliance and impaired ventilation/perfusion (V̇/Q̇) matching. PEEP can increase end-expiratory lung volume, but its effect on V̇/Q̇ mismatch in COVID-19-related ARDS is not clear.

METHODS

We enrolled intubated and mechanically ventilated subjects with COVID-19 ARDS and used the automatic lung parameter estimator (ALPE) to measure V̇/Q̇. Respiratory mechanics measurements, shunt, and V̇/Q̇ mismatch (low V̇/Q̇ and high V̇/Q̇) were collected at 3 PEEP levels (clinical PEEP = intermediate PEEP, low PEEP [clinical - 50%], and high PEEP [clinical + 50%]). A mixed-effect model was used to evaluate the impact of PEEP on V̇/Q̇. We also investigated if PEEP might have a different effect on V̇/Q̇ mismatch in 2 different respiratory mechanics phenotypes, that is, high elastance/low compliance (phenotype H) and low elastance/high compliance (phenotype L).

RESULTS

Seventeen subjects with COVID-related ARDS age 66 [60-71] y with a PaO2 /FIO2 of 141 ± 74 mm Hg were studied at low PEEP = 5.6 ± 2.2 cm H2O, intermediate PEEP = 10.6 ± 3.8 cm H2O, and high PEEP = 15 ± 5 cm H2O. Shunt, low V̇/Q̇, high V̇/Q̇, and alveolar dead space were not significantly influenced, on average, by PEEP. Respiratory system compliance decreased significantly when increasing PEEP without significant variation of PaO2 /FIO2 (P = .26). In the 2 phenotypes, PEEP had opposite effects on shunt, with a decrease in the phenotype L and an increase in phenotype H (P = .048).

CONCLUSIONS

In subjects with COVID-related ARDS placed on invasive mechanical ventilation for > 48 h, PEEP had a heterogeneous effect on V̇/Q̇ mismatch and, on average, higher levels were not able to reduce shunt. The subject's compliance could influence the effect of PEEP on V̇/Q̇ mismatch since an increased shunt was observed in subjects with lower compliance, whereas the opposite occurred in those with higher compliance.

Fever management in critically ill COVID-19 patients: a retrospective analysis

BACKGROUND

Fever has been reported as a common symptom in COVID-19 patients. The aim of the study was to describe the characteristics of COVID-19 critically ill patients with fever and to assess if fever management had an impact on some physiologic variables.

METHODS

This is a retrospective monocentric cohort analysis of critically ill COVID-19 patients admitted to the Department of Intensive Care Unit (ICU) of Erasme Hospital, Brussels, Belgium, between March 2020 and May 2020. Fever was defined as body temperature ≥ 38° C during the ICU stay. We assessed the independent predictors of fever during ICU stay. We reported the clinical and physiological variables before and after the first treated episode of fever during the ICU stay.

RESULTS

A total of 72 critically ill COVID-19 patients were admitted to the ICU over the study period and were all eligible for the final analysis; 53 (74%) of them developed fever, after a median of 4 [0-13] hours since ICU admission. In the multivariable analysis, male gender (OR 5.41 [C.I. 95% 1.34-21.92]; p=0.02) and low PaO2/FiO2 ratio (OR 0.99 [C.I. 95% 0.99-1.00]; p=0.04) were independently associated with fever. After the treatment of the first febrile episode, heart rate and respiratory rate significantly decreased together with an increase in PaO2 and SaO2.

CONCLUSIONS

In our study, male gender and severe impairment of oxygenation were independently associated with fever in critically ill COVID-19 patients. Fever treatment reduced heart rate and respiratory rate and improved systemic oxygenation.

Calculation of Transpulmonary Pressure From Regional Ventilation Displayed by Electrical Impedance Tomography in Acute Respiratory Distress Syndrome

Transpulmonary driving pressure (DP_L) corresponds to the cyclical stress imposed on the lung parenchyma during tidal breathing and, therefore, can be used to assess the risk of ventilator-induced lung injury (VILI). Its measurement at the bedside requires the use of esophageal pressure (Peso), which is sometimes technically challenging. Recently, it has been demonstrated how in an animal model of ARDS, the transpulmonary pressure (P_L) measured with Peso calculated with the absolute values method (P_L = Paw—Peso) is equivalent to the transpulmonary pressure directly measured using pleural sensors in the central-dependent part of the lung. We hypothesized that, since the P_L derived from Peso reflects the regional behavior of the lung, it could exist a relationship between regional parameters measured by electrical impedance tomography (EIT) and driving P_L (DP_L). Moreover, we explored if, by integrating airways pressure data and EIT data, it could be possible to estimate non-invasively DP_L and consequently lung elastance (EL) and elastance-derived inspiratory P_L (PI). We analyzed 59 measurements from 20 patients with ARDS. There was a significant intra-patient correlation between EIT derived regional compliance in regions of interest (ROI1) (r = 0.5, p = 0.001), ROI2 (r = −0.68, p < 0.001), and ROI3 (r = −0.4, p = 0.002), and DP_L. A multiple linear regression successfully predicted DP_L based on respiratory system elastance (Ers), ideal body weight (IBW), roi1%, roi2%, and roi3% (R² = 0.84, p < 0.001). The corresponding Bland-Altmann analysis showed a bias of −1.4e-007 cmH₂O and limits of agreement (LoA) of −2.4–2.4 cmH₂O. EL and PI calculated using EIT showed good agreement (R² = 0.89, p < 0.001 and R² = 0.75, p < 0.001) with the esophageal derived correspondent variables. In conclusion, DP_L has a good correlation with EIT-derived parameters in the central lung. DP_L, PI, and EL can be estimated with good accuracy non-invasively combining information coming from EIT and airway pressure.

Management of Intraoperative Mechanical Ventilation to Prevent Postoperative Complications after General Anesthesia: A Narrative Review

Mechanical ventilation (MV) is still necessary in many surgical procedures; nonetheless, intraoperative MV is not free from harmful effects. Protective ventilation strategies, which include the combination of low tidal volume and adequate positive end expiratory pressure (PEEP) levels, are usually adopted to minimize the ventilation-induced lung injury and to avoid post-operative pulmonary complications (PPCs). Even so, volutrauma and atelectrauma may co-exist at different levels of tidal volume and PEEP, and therefore, the physiological response to the MV settings should be monitored in each patient. A personalized perioperative approach is gaining relevance in the field of intraoperative MV; in particular, many efforts have been made to individualize PEEP, giving more emphasis on physiological and functional status to the whole body. In this review, we summarized the latest findings about the optimization of PEEP and intraoperative MV in different surgical settings. Starting from a physiological point of view, we described how to approach the individualized MV and monitor the effects of MV on lung function.

Proteomic analysis identifies key differences in the cardiac interactomes of dystrophin and micro-dystrophin

ΔR4-R23/ΔCT micro-dystrophin (μDys) is a miniaturized version of dystrophin currently evaluated in a Duchenne muscular dystrophy (DMD) gene therapy trial to treat skeletal and cardiac muscle disease. In pre-clinical studies, μDys efficiently rescues cardiac histopathology, but only partially normalizes cardiac function. To gain insights into factors that may impact the cardiac therapeutic efficacy of μDys, we compared by mass spectrometry the composition of purified dystrophin and μDys protein complexes in the mouse heart. We report that compared to dystrophin, μDys has altered associations with α1- and β2-syntrophins, as well as cavins, a group of caveolae-associated signaling proteins. In particular, we found that membrane localization of cavin-1 and cavin-4 in cardiomyocytes requires dystrophin and is profoundly disrupted in the heart of mdx^5cv mice, a model of DMD. Following cardiac stress/damage, membrane-associated cavin-4 recruits the signaling molecule ERK to caveolae, which activates key cardio-protective responses. Evaluation of ERK signaling revealed a profound inhibition, below physiological baseline, in the mdx^5cv mouse heart. Expression of μDys in mdx^5cv mice prevented the development of cardiac histopathology but did not rescue membrane localization of cavins nor did it normalize ERK signaling. Our study provides the first comparative analysis of purified protein complexes assembled in vivo by full-length dystrophin and a therapeutic micro-dystrophin construct. This has revealed disruptions in cavins and ERK signaling that may contribute to DMD cardiomyopathy. This new knowledge is important for ongoing efforts to prevent and treat heart disease in DMD patients.

Regulation of the dystrophin-associated glycoprotein complex composition by the metabolic properties of muscle fibres

The dystrophin-glycoprotein complex (DGC) links the muscle cytoskeleton to the extracellular matrix and is responsible for force transduction and protects the muscle fibres from contraction induced damage. Mutations in components of the DGC are responsible for muscular dystrophies and congenital myopathies. Expression of DGC components have been shown to be altered in many myopathies. In contrast we have very little evidence of whether adaptive changes in muscle impact on DGC expression. In this study we investigated connection between muscle fibre phenotype and the DGC. Our study reveals that the levels of DGC proteins at the sarcolemma differ in highly glycolytic muscle compared to wild-type and that these changes can be normalised by the super-imposition of an oxidative metabolic programme. Importantly we show that the metabolic properties of the muscle do not impact on the total amount of DGC components at the protein level. Our work shows that the metabolic property of a muscle fibre is a key factor in regulating the expression of DGC proteins at the sarcolemma.

Cardiac-Specific Expression of ΔH2-R15 Mini-Dystrophin Normalized All Electrocardiogram Abnormalities and the End-Diastolic Volume in a 23-Month-Old Mouse Model of Duchenne Dilated Cardiomyopathy

Heart disease is a major health threat for Duchenne/Becker muscular dystrophy patients and carriers. Expression of a 6-8 kb mini-dystrophin gene in the heart holds promise to change the disease course dramatically. However, the mini-dystrophin gene cannot be easily studied with adeno-associated virus (AAV) gene delivery because the size of the minigene exceeds AAV packaging capacity. Cardiac protection of the ΔH2-R19 minigene was previously studied using the cardiac-specific transgenic approach. Although this minigene fully normalized skeletal muscle force, it only partially corrected electrocardiogram and heart hemodynamics in dystrophin-null mdx mice that had moderate cardiomyopathy. This study evaluated the ΔH2-R15 minigene using the same transgenic approach in mdx mice that had more severe cardiomyopathy. In contrast to the ΔH2-R19 minigene, the ΔH2-R15 minigene carries dystrophin spectrin-like repeats 16 to 19 (R16-19), a region that has been suggested to protect the heart in clinical studies. Cardiac expression of the ΔH2-R15 minigene normalized all aberrant electrocardiogram changes and improved hemodynamics. Importantly, it corrected the end-diastolic volume, an important diastolic parameter not rescued by ΔH2-R19 mini-dystrophin. It is concluded that that ΔH2-R15 mini-dystrophin is a superior candidate gene for heart protection. This finding has important implications in the design of the mini/micro-dystrophin gene for Duchenne cardiomyopathy therapy.

Can Human Pluripotent Stem Cell-Derived Cardiomyocytes Advance Understanding of Muscular Dystrophies?

Muscular dystrophies (MDs) are clinically and molecularly a highly heterogeneous group of single-gene disorders that primarily affect striated muscles. Cardiac disease is present in several MDs where it is an important contributor to morbidity and mortality. Careful monitoring of cardiac issues is necessary but current management of cardiac involvement does not effectively protect from disease progression and cardiac failure. There is a critical need to gain new knowledge on the diverse molecular underpinnings of cardiac disease in MDs in order to guide cardiac treatment development and assist in reaching a clearer consensus on cardiac disease management in the clinic. Animal models are available for the majority of MDs and have been invaluable tools in probing disease mechanisms and in pre-clinical screens. However, there are recognized genetic, physiological, and structural differences between human and animal hearts that impact disease progression, manifestation, and response to pharmacological interventions. Therefore, there is a need to develop parallel human systems to model cardiac disease in MDs. This review discusses the current status of cardiomyocytes (CMs) derived from human induced pluripotent stem cells (hiPSC) to model cardiac disease, with a focus on Duchenne muscular dystrophy (DMD) and myotonic dystrophy (DM1). We seek to provide a balanced view of opportunities and limitations offered by this system in elucidating disease mechanisms pertinent to human cardiac physiology and as a platform for treatment development or refinement.

Link between MHC Fiber Type and Restoration of Dystrophin Expression and Key Components of the DAPC by Tricyclo-DNA-Mediated Exon Skipping

Exon skipping mediated by tricyclo-DNA (tc-DNA) antisense oligonucleotides has been shown to induce significant levels of dystrophin restoration in mdx, a mouse model of Duchenne muscular dystrophy. This translates into significant improvement in key disease indicators in muscle, cardio-respiratory function, heart, and the CNS. Here we examine the relationship between muscle fiber type, based on myosin heavy chain (MHC) profile, and the ability of tc-DNA to restore not only dystrophin but also other members of the dystrophin-associated glycoprotein complex (DAPC). We first profiled this relationship in untreated mdx muscle, and we found that all fiber types support reversion events to a dystrophin-positive state, in an unbiased manner. Importantly, we show that only a small fraction of revertant fibers expressed other members of the DAPC. Immunoblot analysis of protein levels, however, revealed robust expression of these components, which failed to correctly localize to the sarcolemma. We then show that tc-DNA treatment leads to nearly all fibers expressing not only dystrophin but also other key components of the DAPC. Of significance, our work shows that MHC fiber type does not bias the expression of any of these important proteins. This work also highlights that the improved muscle physiology following tc-DNA treatment reported previously results from the complete restoration of the dystrophin complex in all MHCII fibers with equal efficiencies.

A randomized, double-blind, placebo-controlled, multicenter study of a ginger extract in the management of chemotherapy-induced nausea and vomiting (CINV) in patients receiving high-dose cisplatin

BACKGROUND

The activity of ginger in the management of chemotherapy-induced nausea and vomiting (CINV) has been suggested, but design inadequacies, heterogeneity of the population, small numbers and poor quality of tested products limit the possibility to offer generalizable results.

PATIENTS AND METHODS

We conducted a randomized, double-blind, placebo-controlled, multicenter study in patients planned to receive ≥2 chemotherapy cycles with high dose (>50 mg/m2) cisplatin. Patients received ginger 160 mg/day (with standardized dose of bioactive compounds) or placebo in addition to the standard antiemetic prophylaxis for CINV, starting from the day after cisplatin administration. CINV was assessed through daily visual-analogue scale and Functional Living Index Emesis questionnaires. The main objective was protection from delayed nausea; secondary end points included intercycle nausea and nausea anticipatory symptoms.

RESULTS

In total, 121 patients received ginger and 123 placebo. Lung (49%) and head and neck cancer (HNC; 35%) were the most represented tumors. No differences were reported in terms of safety profile or compliance. The incidence of delayed, intercycle and anticipatory nausea did not differ between the two arms in the first cycle and second cycle. A benefit of ginger over placebo in Functional Living Index Emesis nausea score differences (day 6-day 1) was identified for females (P = 0.048) and HNC patients (P = 0.038).

CONCLUSIONS

In patients treated with high-dose cisplatin, the daily addition of ginger, even if safe, did not result in a protective effect on CINV. The favorable effect observed on nausea in subgroups at particular risk of nausea (females; HNC) deserves specific investigation.

Efficient method for site-directed mutagenesis in large plasmids without subcloning

Commonly used methods for site-directed DNA mutagenesis require copying the entire target plasmid. These methods allow relatively easy modification of DNA sequences in small plasmids but become less efficient and faithful for large plasmids, necessitating full sequence verification. Introduction of mutations in larger plasmids requires subcloning, a slow and labor-intensive process, especially for multiple mutations. We have developed an efficient DNA mutagenesis technique, UnRestricted Mutagenesis and Cloning (URMAC) that replaces subcloning steps with quick biochemical reactions. URMAC does not suffer from plasmid size constraints and allows simultaneous introduction of multiple mutations. URMAC involves manipulation of only the mutagenesis target site(s), not the entire plasmid being mutagenized, therefore only partial sequence verification is required. Basic URMAC requires two PCR reactions, each followed by a ligation reaction to circularize the product, with an optional third enrichment PCR step followed by a traditional cloning step that requires two restriction sites. Here, we demonstrate URMAC’s speed, accuracy, and efficiency through several examples, creating insertions, deletions or substitutions in plasmids ranging from 2.6 kb to 17 kb without subcloning.

NF-κB-mediated Pax7 dysregulation in the muscle microenvironment promotes cancer cachexia

Cachexia is a debilitating condition characterized by extreme skeletal muscle wasting that contributes significantly to morbidity and mortality. Efforts to elucidate the underlying mechanisms of muscle loss have predominantly focused on events intrinsic to the myofiber. In contrast, less regard has been given to potential contributory factors outside the fiber within the muscle microenvironment. In tumor-bearing mice and patients with pancreatic cancer, we found that cachexia was associated with a type of muscle damage resulting in activation of both satellite and nonsatellite muscle progenitor cells. These muscle progenitors committed to a myogenic program, but were inhibited from completing differentiation by an event linked with persistent expression of the self-renewing factor Pax7. Overexpression of Pax7 was sufficient to induce atrophy in normal muscle, while under tumor conditions, the reduction of Pax7 or exogenous addition of its downstream target, MyoD, reversed wasting by restoring cell differentiation and fusion with injured fibers. Furthermore, Pax7 was induced by serum factors from cachectic mice and patients, in an NF-κB-dependent manner, both in vitro and in vivo. Together, these results suggest that Pax7 responds to NF-κB by impairing the regenerative capacity of myogenic cells in the muscle microenvironment to drive muscle wasting in cancer.

The ZZ domain of dystrophin in DMD: making sense of missense mutations

Duchenne muscular dystrophy (DMD) is associated with the loss of dystrophin, which plays an important role in myofiber integrity via interactions with β-dystroglycan and other members of the transmembrane dystrophin-associated protein complex. The ZZ domain, a cysteine-rich zinc-finger domain near the dystrophin C-terminus, is implicated in forming a stable interaction between dystrophin and β-dystroglycan, but the mechanism of pathogenesis of ZZ missense mutations has remained unclear because not all such mutations have been shown to alter β-dystroglycan binding in previous experimental systems. We engineered three ZZ mutations (p.Cys3313Phe, p.Asp3335His, and p.Cys3340Tyr) into a short construct similar to the Dp71 dystrophin isoform for in vitro and in vivo studies and delineated their effect on protein expression, folding properties, and binding partners. Our results demonstrate two distinct pathogenic mechanisms for ZZ missense mutations. The cysteine mutations result in diminished or absent subsarcolemmal expression because of protein instability, likely due to misfolding. In contrast, the aspartic acid mutation disrupts binding with β-dystroglycan despite an almost normal expression at the membrane, confirming a role for the ZZ domain in β-dystroglycan binding but surprisingly demonstrating that such binding is not required for subsarcolemmal localization of dystrophin, even in the absence of actin binding domains.

Identification of new dystroglycan complexes in skeletal muscle

The dystroglycan complex contains the transmembrane protein β-dystroglycan and its interacting extracellular mucin-like protein α-dystroglycan. In skeletal muscle fibers, the dystroglycan complex plays an important structural role by linking the cytoskeletal protein dystrophin to laminin in the extracellular matrix. Mutations that affect any of the proteins involved in this structural axis lead to myofiber degeneration and are associated with muscular dystrophies and congenital myopathies. Because loss of dystrophin in Duchenne muscular dystrophy (DMD) leads to an almost complete loss of dystroglycan complexes at the myofiber membrane, it is generally assumed that the vast majority of dystroglycan complexes within skeletal muscle fibers interact with dystrophin. The residual dystroglycan present in dystrophin-deficient muscle is thought to be preserved by utrophin, a structural homolog of dystrophin that is up-regulated in dystrophic muscles. However, we found that dystroglycan complexes are still present at the myofiber membrane in the absence of both dystrophin and utrophin. Our data show that only a minority of dystroglycan complexes associate with dystrophin in wild type muscle. Furthermore, we provide evidence for at least three separate pools of dystroglycan complexes within myofibers that differ in composition and are differentially affected by loss of dystrophin. Our findings indicate a more complex role of dystroglycan in muscle than currently recognized and may help explain differences in disease pathology and severity among myopathies linked to mutations in DAPC members.

Muscle side population cells from dystrophic or injured muscle adopt a fibro-adipogenic fate

Muscle side population (SP) cells are rare multipotent stem cells that can participate in myogenesis and muscle regeneration upon transplantation. While they have been primarily studied for the development of cell-based therapies for Duchenne muscular dystrophy, little is known regarding their non-muscle lineage choices or whether the dystrophic muscle environment affects their ability to repair muscle. Unfortunately, the study of muscle SP cells has been challenged by their low abundance and the absence of specific SP cell markers. To address these issues, we developed culture conditions for the propagation and spontaneous multi-lineage differentiation of muscle SP cells. Using this approach, we show that SP cells from wild type muscle robustly differentiate into satellite cells and form myotubes without requiring co-culture with myogenic cells. Furthermore, this myogenic activity is associated with SP cells negative for immune (CD45) and vascular (CD31) markers but positive for Pax7, Sca1, and the mesenchymal progenitor marker PDGFRα. Additionally, our studies revealed that SP cells isolated from dystrophic or cardiotoxin-injured muscle fail to undergo myogenesis. Instead, these SP cells rapidly expand giving rise to fibroblast and adipocyte progenitors (FAPs) and to their differentiated progeny, fibroblasts and adipocytes. Our findings indicate that muscle damage affects the lineage choices of muscle SP cells, promoting their differentiation along fibro-adipogenic lineages while inhibiting myogenesis. These results have implications for a possible role of muscle SP cells in fibrosis and fat deposition in muscular dystrophy. In addition, our studies provide a useful in vitro system to analyze SP cell biology in both normal and pathological conditions.

Comparative proteomic profiling of dystroglycan-associated proteins in wild type, mdx, and Galgt2 transgenic mouse skeletal muscle

Dystroglycan is a major cell surface glycoprotein receptor for the extracellular matrix in skeletal muscle. Defects in dystroglycan glycosylation cause muscular dystrophy and alterations in dystroglycan glycosylation can impact extracellular matrix binding. Here we describe an immunoprecipitation technique that allows isolation of beta dystroglycan with members of the dystrophin-associated protein complex (DAPC) from detergent-solubilized skeletal muscle. Immunoprecipitation, coupled with shotgun proteomics, has allowed us to identify new dystroglycan-associated proteins and define changed associations that occur within the DAPC in dystrophic skeletal muscles. In addition, we describe changes that result from overexpression of Galgt2, a normally synaptic muscle glycosyltransferase that can modify alpha dystroglycan and inhibit the development of muscular dystrophy when it is overexpressed. These studies identify new dystroglycan-associated proteins that may participate in dystroglycan's roles, both positive and negative, in muscular dystrophy.

mdx(⁵cv) mice manifest more severe muscle dysfunction and diaphragm force deficits than do mdx Mice

Duchenne muscular dystrophy (DMD) is characterized by progressive skeletal muscle dysfunction leading to premature death by the third decade of life. The mdx mouse, the most widely used animal model of DMD, has been extremely useful to study disease mechanisms and to screen new therapeutics. However, unlike patients with DMD, mdx mice have a very mild motor function deficit, posing significant limitations for its use as a platform to assess the impact of treatments on motor function. It has been suggested that an mdx variant, the mdx(5cv) mouse, might be more severely affected. Here, we compared the motor activity, histopathology, and individual muscle force measurements of mdx and mdx(⁵cv) mice. Our study revealed that mdx(⁵cv) mice showed more severe exercise-induced fatigue, Rotarod performance deficits, and gait anomalies than mdx mice and that these deficits began at a younger age. Muscle force studies showed more severe strength deficits in the diaphragm of mdx(⁵cv) mice compared to mdx mice, but similar force generation in the extensor digitorum longus. Muscle histology was similar between the two strains. Differences in genetic background (genetic modifiers) probably account for these functional differences between mdx strains. Overall, our findings indicate that the mdx and mdx(⁵cv) mouse models of DMD are not interchangeable and identify the mdx(⁵cv) mouse as a valuable platform for preclinical studies that require assessment of muscle function in live animals.

BMP-9-induced muscle heterotopic ossification requires changes to the skeletal muscle microenvironment

Heterotopic ossification (HO) is defined as the formation of bone inside soft tissue. Symptoms include joint stiffness, swelling, and pain. Apart from the inherited form, the common traumatic form generally occurs at sites of injury in damaged muscles and is often associated with brain injury. We investigated bone morphogenetic protein 9 (BMP-9), which possesses a strong osteoinductive capacity, for its involvement in muscle HO physiopathology. We found that BMP-9 had an osteoinductive influence on mouse muscle resident stromal cells by increasing their alkaline phosphatase activity and bone-specific marker expression. Interestingly, BMP-9 induced HO only in damaged muscle, whereas BMP-2 promoted HO in skeletal muscle regardless of its state. The addition of the soluble form of the ALK1 protein (the BMP-9 receptor) significantly inhibited the osteoinductive potential of BMP-9 in cells and HO in damaged muscles. BMP-9 thus should be considered a candidate for involvement in HO physiopathology, with its activity depending on the skeletal muscle microenvironment.

Isolation and transcriptome analysis of adult zebrafish cells enriched for skeletal muscle progenitors

INTRODUCTION

Over the past 10 years, the use of zebrafish for scientific research in the area of muscle development has increased dramatically. Although several protocols exist for the isolation of adult myoblast progenitors from larger fish, no standardized protocol exists for the isolation of myogenic progenitors from adult zebrafish muscle.

METHODS

Using a variant of a mammalian myoblast isolation protocol, zebrafish muscle progenitors have been isolated from the total dorsal myotome. These zebrafish myoblast progenitors can be cultured for several passages and then differentiated into multinucleated, mature myotubes.

RESULTS

Transcriptome analysis of these cells during myogenic differentiation revealed a strong downregulation of pluripotency genes, while, conversely, showing an upregulation of myogenic signaling and structural genes.

CONCLUSIONS

Together these studies provide a simple, yet detailed method for the isolation and culture of myogenic progenitors from adult zebrafish, while further promoting their therapeutic potential for the study of muscle disease and drug screening.

Analysis of dystrophin deletion mutations predicts age of cardiomyopathy onset in becker muscular dystrophy

BACKGROUND

Becker muscular dystrophy (BMD) and X-linked dilated cardiomyopathy often result from deletion mutations in the dystrophin gene that may lead to expression of an altered dystrophin protein in cardiac muscle. Cardiac involvement is present in approximately 70% of BMD and all X-linked dilated cardiomyopathy cases. To date, the timing of cardiomyopathy development remains unpredictable. We analyzed 78 BMD and X-linked dilated cardiomyopathy patients with common deletion mutations predicted to alter the dystrophin protein and correlated their mutations to cardiomyopathy age of onset. This approach was chosen to connect dystrophin structure with function in the heart.

METHODS AND RESULTS

Detailed cardiac information was collected for BMD and X-linked dilated cardiomyopathy patients with defined dystrophin gene deletion mutations. Patients were grouped based on the dystrophin protein domain affected by the deletion. Deletions affecting the amino-terminal domain are associated with early-onset dilated cardiomyopathy (DCM; mid-20s), whereas deletions removing part of the rod domain and hinge 3 have a later-onset DCM (mid-40s). Further, we modeled the effects of the most common mutations occurring in the rod domain on the overall structure of the dystrophin protein. By combining genetic and protein information, this analysis revealed a strong correlation between specific protein structural modifications and DCM age of onset.

CONCLUSIONS

We identified specific regions of the dystrophin gene that when mutated predispose BMD patients to early-onset DCM. In addition, we propose that some mutations lead to early-onset DCM by specific alterations in protein folding. These findings have potential implications for early intervention in the cardiac care of BMD patients and for therapeutic approaches that target the heart in dystrophinopathies.

Current understanding and management of dilated cardiomyopathy in Duchenne and Becker muscular dystrophy

PURPOSE

To review the current understanding of the pathophysiology of dilated cardiomyopathy (DCM) in patients with Duchenne and Becker muscular dystrophies, assessment of cardiac dysfunction for these patients, and the recommended pharmacological treatment options and ongoing research directions.

DATA SOURCES

Reviews and original research articles from scholarly journals and books.

CONCLUSIONS

Duchenne and Becker muscular dystrophies are debilitating neuromuscular disorders, both caused by mutations in the dystrophin gene. Most patients develop DCM as part of the disease course; in fact, DCM is the leading cause of death among these patients. Cardiac surveillance, including routine monitoring of electrocardiograms, echocardiograms, and appropriate blood biomarkers, may detect early DCM development. Although previous studies have shown that early administration of cardiac medications may delay the development of DCM, current standard of care does not emphasize cardiac surveillance and timely treatment. This, in turn, limits clinicians, including advanced practice nurses, to be optimally engaged in providing the most aggressive and proactive patient care.

IMPLICATIONS FOR PRACTICE

Implementing a routine cardiac assessment and timely pharmacological treatment in primary or specialty care settings is highlighted as an important step to optimize cardiac health among patients with Duchenne and Becker muscular dystrophies.

Predictors of mortality of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF), a disease with histological features corresponding to usual interstitial pneumonia (UIP), is a disorder of unknown cause. Not only it is the most common subtype of idiopathic interstitial pneumonias but it is also associated with the highest mortality rate. Despite a good number of studies investigating the mortality of patients with UIP the prognostic factors that have been studied have several limitations. To date it is unclear when in the course of the disease and with what modality these patients should be treated. According to the literature we subcategorized predictors of mortality into (a) baseline predictors; (b) dynamic predictors. IPF perspectives in therapy have been also analyzed. Moreover, the principal aims of this review were: (1) to analyze and to clarify the clinical utility of different prognostic factors for IPF; (2) to enable clinicians to better evaluate the eligibility criteria for lung transplantation in the clinical practice.

[Mesothelioma incidence and time trend in the worlds]

BACKGROUND

Due to its adaptability to different uses, asbestos was increasingly employed in many working and domestic areas up to the 1970s-1980s, when its aetiological role in the onset of pleural mesothelioma (Mm) was recognized. Since then Mm cases have been continuously increasing and no decline is expected until 2020, despite the fact that most industrialized countries banned asbestos use a few decades ago.

OBJECTIVES

The aim of this study was to analyse Mm incidence in the World during the last ten years, also considering asbestos consumption in diferent areas.

METHODS

Incidence age-standardized rates (ASR) from Cancer Registries included in Cancer Incidence in Five Continents, Vol. VII and VIII, and, when appropriate, standardized rate ratio (SRR) with confidence interval were estimated.

RESULTS

The highest incidence rates among males were observed in Liguria and Australia. After Liguria, Maastricht and Scotland in Europe, North East Regions and Piedmont in Italy showed high rates. Among females, the highest incidence rates were observed in Liguria, among black women in New Orleans and in the province of Varese. SRRs revealed increased rates, not always significant, in almost all areas among males and in about 50% of the areas among females, although the variation was significant only in Varese.

CONCLUSIONS

These results confirmed a relationship between Mm risk and asbestos use, revealing high incidence rates in Australia (mining), Italy (shipyards, building, goods handling, heavy industries and sea trade) and Great Britain (shipyards). Mm cases increased in areas with elevated incidence rates, suggesting that larger amounts of asbestos were probably used for a longer period. Finally, no Mm cases were registered in some areas, which probably signifies a lack (or a delay) of risk referred to the investigated period.

Incidence of pleural mesothelioma in Liguria Region, Italy (1996–2002)

In this study, incidence of pleural malignant mesothelioma (PMM) in the Liguria Region (Italy) (approximately 1.6 million inhabitants), in the presence of asbestos exposure was investigated. New PMM cases recorded by the Mesothelioma Registry of Liguria, from 1996 to 2002 and interviews reported on a standardised questionnaire were analysed according to demographical and etiological characteristics. Nine hundred and forty five PMM cases were recorded (757 males and 188 females); the age standardised (European population) incidence rates per 100,000 were 8.51 and 1.43, respectively. The rates among the four provinces ranged between 1.18 and 13.7 for males and 0.68 and 1.44 for females. The questionnaire was evaluated for 786 PMM cases (or next-of-kin). Higher incidence rates were reported in the provinces with larger industrial and harbour areas, including shipyards (construction and repair), dockyards, building activities, chemical and heavy industrial activities. Asbestos exposure was unlikely or unknown for 57.5% females and 15% males. A major role of environmental asbestos exposure in the etiology of PMM is hypothesised for females and for a minor proportion of males.

Epidemiologic surveillance for primary prevention of malignant mesothelioma: the Italian experience

BACKGROUND

The Italian National Mesothelioma Registry (ReNaM) was set up at the National Institute for Occupational Safety and Health (ISPESL) to estimate Italian incidence of malignant mesothelioma (MM), define modalities of asbestos exposures, assess impact and diffusion of MM, identify underestimated sources of environmental contamination.

OBJECTIVES

To describe ReNaM activity, database dimension and epidemiological characteristics of the caselist.

METHODS

Regional Operating Centers (COR) in 16 Italian regions were set up to identify and investigate all cases of MM diagnosed in each region, applying national guidelines. COR collect cases in health care institutions. Occupational history, lifestyle and residence are obtained by direct interview using a standard questionnaire. Exposure modalities are classified by industrial hygienists, evaluating whether work, private life or any particular environmental condition could have involved asbestos exposure.

RESULTS

Data refer to 3,446 cases collected in 9 Italian regions during 1993-2001. Pleural mesothelioma affected 94% cases, pleural/peritoneal ratio was 16:1. Gender ratio (M/F) was 2.7:1 (1.3:1 for peritoneum). There was a variety of occupational exposures, some already known as high risk sectors and others unexpected. The most common exposures occurred in building and construction, metallurgy and steel, shipbuilding, and railway stock. High risk categories were encountered such as bricklayers, plumbers, carpenters, electricians, welders, installers and maintenance workers in metallurgy and the steel industry, general labourers, tool makers and painters in shipbuilding/repair/demolition.

CONCLUSIONS

Despite some ReNam's limitations, identification of MM cases and analysis of modality of exposure, with standardized criteria, are a fundamental tool for primary prevention of asbestos related diseases.

δ-Sarcoglycan is required for early zebrafish muscle organization

Mutations in sarcoglycans (alpha-, beta-, gamma-, and delta-) have been linked with limb girdle muscular dystrophy (LGMD) types 2C-F in humans. We have cloned the zebrafish orthologue encoding delta-sarcoglycan and mapped the gene to linkage group 21. The predicted zebrafish delta-sarcoglycan protein is highly homologous with its human orthologue including conservation of two of the three predicted glycosylation sites. Like other members of the dystrophin-associated protein complex (DAPC), delta-sarcoglycan localizes to the sarcolemmal membrane of the myofiber in adult zebrafish, but is more apparent at the myosepta in developing embryos. Zebrafish embryos injected with morpholinos against delta-sarcoglycan were relatively inactive at 5 dpf, their myofibers were disorganized, and swim bladders uninflated. Immunohistochemical and immunoblotting experiments show that delta-, beta-, and gamma-sarcoglycans were all downregulated in the morphants, whereas dystrophin expression was unaffected. Whereas humans lacking delta-sarcoglycan primarily show adult phenotypes, our results suggest that delta-sarcoglycan plays a role in early zebrafish muscle development.

Demystifying SP cell purification: viability, yield, and phenotype are defined by isolation parameters

Side population (SP) cells isolated from bone marrow, skeletal muscle, and skin have been shown to engraft in dystrophic muscle. However, there have been questions on the phenotypical heterogeneity, tissue of origin, and relationships among SP cell populations extracted from different tissues. Studies on bone marrow SP cells have followed a consistent protocol for their isolation and results obtained are concordant. In contrast, protocols for the isolation of muscle SP cells vary greatly, and consequently reports on their phenotype, differentiation potential and origin have been inconsistent. To address this controversy, we demonstrate that isolation parameters, such as tissue dissociation, cell counting, Hoechst concentration, and stringency in the selection of SP cells, have an effect on the yield, viability, and homogeneity of SP cells derived from bone marrow, skeletal muscle, and skin. In this paper, we demonstrate that SP cells isolated from the bone marrow are distinct from SP cells extracted from skeletal muscle and skin tissues. This study offers an explanation for the controversy surrounding muscle SP cells, provides a detailed standardized protocol for their isolation, and highlights basic guidelines for reproducible and reliable isolation of SP cells from any tissue.

Expression profiling and identification of novel genes involved in myogenic differentiation

Skeletal muscle differentiation is a complex, highly coordinated process that relies on precise temporal gene expression patterns. To better understand this cascade of transcriptional events, we used expression profiling to analyze gene expression in a 12-day time course of differentiating C2C12 myoblasts. Cluster analysis specific for time-ordered microarray experiments classified 2895 genes and ESTs with variable expression levels between proliferating and differentiating cells into 22 clusters with distinct expression patterns during myogenesis. Expression patterns for several known and novel genes were independently confirmed by real-time quantitative RT-PCR and/or Western blotting and immunofluorescence. MyoD and MEF family members exhibited unique expression kinetics that were highly coordinated with cell-cycle withdrawal regulators. Among genes with peak expression levels during cell cycle withdrawal were Vcam1, Itgb3, Itga5, Vcl, as well as Ptger4, a gene not previously associated with the process of myogenesis. One interesting uncharacterized transcript that is highly induced during myogenesis encodes several immunoglobulin repeats with sequence similarity to titin, a large sarcomeric protein. These data sets identify many additional uncharacterized transcripts that may play important functions in muscle cell proliferation and differentiation and provide a baseline for comparison with C2C12 cells expressing various mutant genes involved in myopathic disorders.

Skeletal muscle engraftment potential of adult mouse skin side population cells

Adult bone marrow and skeletal muscle have been shown to contain a subpopulation of cells, called side population (SP) cells, that can be isolated with the fluorescence-activated cell sorter. We used a similar method to identify SP cells in the skin of adult mice. These cells express surface markers similar to SP cells isolated from skeletal muscle, but differ from bone marrow SP cells and do not express hematopoietic markers. When transplanted into nonirradiated mdx mice, nuclei from donor skin SP cells are found within myofibers that express dystrophin. Thus, adult skin SP cells can engraft in dystrophic skeletal muscle even in the absence of total body irradiation.

Targeting dystroglycan in the brain

The dystrophin-glycoprotein complex is a multisubunit complex that connects the extracellular matrix components to the cytoskeletal matrix of muscle fiber cells and is required for muscle integrity. Mutations in this complex are associated with muscular dystrophy. Although the role of dystroglycan has been explored mainly in the context of muscle, recent work has also demonstrated a novel role for dystroglycan in the CNS and thus provides potential insights into the brain abnormalities associated with some forms of muscular dystrophy.

[Occupational exposure to asbestos and recognition of pleural mesothelioma as occupational disease in the province of Genoa]

The present study compares the data of pleural mesothelioma (PM) patients resident in the province of Genoa (Italy) who, in the period 1994-1996, applied to the Italian National Insurance Institute for Work Accident (INAIL), for workers' compensation for asbestos-related diseases due to occupational exposure, with the dataset of PM patients collected by the Mesothelioma Registry of Liguria (REM) in the same period and in the same area. As PM is a malignant tumor of a prevalently occupational origin, it is recognized and acknowledged as such by INAIL when clinical and etiological characteristics are matched. Objectives of this study were to describe observed PM cases, to evaluate completeness of collected data and differences between those who requested compensation and those who did not. The REM describes the incidence of PM among Ligurian residents, proposing patients with a specific questionnaire to assess occupational, environmental and indoor asbestos exposures. The REM collected 199 new cases of PM among the residents of both the city of Genoa (1994-96) and the province of Genoa (1995-96). In the same period, INAIL received 48 (24%) applications for compensation. Among these, 43 subjects were included in a subgroup of 98 patients registered in the REM as cases with definite diagnosis and ascertained asbestos exposure; 32 were awarded compensation, while 11 are under evaluation. The data collected by REM do not show proven asbestos exposure and/or PM diagnosis for five other subjects (two compensated and three under judgment). This study reveals that: a) only a 24% of the patients with a diagnosis of PM and asbestos exposure apply for compensation; b) an exchange of information among institutions involved in primary prevention, in the evaluation of occupational exposures to carcinogens and in insurance compensation is useful.

[Mesothelioma registry of the Liguria region. Incidence and occupational etiology in a high risk area]

This paper presents the epidemiological analyses based on the first 5 years of activity of the Mesothelioma Registry of Liguria (REM). REM is a population-based cancer registry specialized in the study of both the incidence and etiology of primary pleural and peritoneal mesothelioma in Liguria (Italy). The REM completes normal clinical information with occupational and environmental anamnestic data in order to identify working and living areas at risk for asbestos-related pathologies. The REM started its activity in 1994 describing the incidence of pleural mesothelioma (PM) exclusively in the population resident in the city of Genoa (660,000 inhabitants); since 1996 the REM has studied the entire Liguria Region (1,640,000 inhabitants), where nearly 120 new cases of PM are diagnosed annually (20% are women). In the city of Genoa, between 1986-1987 and 1997-1998, PM crude incidence rate rose from 13.8 to 26.7 per 100,000 males over 40 years old. From 1994 to 1998 the REM registered 495 new patients with histologically (62%) and cytologically (9%) confirmed diagnosis of PM. 54% of them were immunocytohistochemically evaluated. Occupational information has been gathered for 248 subjects, i.e., 61% of cases with sure or probable diagnosis of PM. For 126 patients, occupational asbestos exposure (direct, indirect or only presence in the workplace) was identified on average 40 years before diagnosis. In particular, asbestos exposure was documented in shipyards, docks and cargo handling settings, building trades, iron and steel industries. Interestingly, during the same period (1955-1960), a large fraction of subjects without proved or declared direct asbestos exposure claimed to have worked in the same occupational settings. This suggests a possible unconscious indirect exposure to asbestos fibers in the workplace.