Valproic acid reduces muscle susceptibility to contraction-induced functional loss but increases weakness in two murine models of Duchenne muscular dystrophy.

Skeletal muscles in animal models of Duchenne muscular dystrophy (DMD) are more susceptible to contraction-induced functional loss, which is not related to fatigue. Valproic acid (VPA) reportedly improves serological and histological markers of damage in dystrophin-deficient murine muscle. Here, we tested whether VPA would reduce the susceptibility to contraction-induced functional loss in two murine DMD models. Adult female mdx (mild) and D2-mdx (severe) DMD murine models were administered VPA (240 mg/kg) or saline for 7 days. Some VPA-treated mdx mice also performed voluntary running in a wheel, which is known to reduce the susceptibility to contraction-induced functional loss; that is, isometric force drop following eccentric contractions. In situ muscle function was assessed before, during and after eccentric contractions. Muscle utrophin and desmin expression were also evaluated using immunoblotting. Interestingly, VPA reduced the isometric force drop following eccentric contractions in both murine models, without change in the relative eccentric maximal force and in the expression of utrophin and desmin. VPA for 7 days combined with voluntary running had no additive effect compared to VPA alone. Furthermore, VPA reduced the absolute isometric maximal force before eccentric contractions in both murine models. The results of our study indicated that VPA in both murine DMD models reduced the susceptibility to contraction-induced functional loss but increased muscle weakness.

Novel Cardiokine GDF3 Predicts Adverse Fibrotic Remodeling After Myocardial Infarction.

BACKGROUND: Myocardial infarction (MI) induces a repair response that ultimately generates a stable fibrotic scar. Although the scar prevents cardiac rupture, an excessive profibrotic response impairs optimal recovery by promoting the development of noncontractile fibrotic areas. The mechanisms that lead to cardiac fibrosis are diverse and incompletely characterized. We explored whether the expansion of cardiac fibroblasts after MI can be regulated through a paracrine action of cardiac stromal cells. METHODS: We performed a bioinformatic secretome analysis of cardiac stromal PW1+ cells isolated from normal and post-MI mouse hearts to identify novel secreted proteins. Functional assays were used to screen secreted proteins that promote fibroblast proliferation. The expressions of candidates were subsequently analyzed in mouse and human hearts and plasmas. The relationship between levels of circulating protein candidates and adverse post-MI cardiac remodeling was examined in a cohort of 80 patients with a first ST-segment-elevation MI and serial cardiac magnetic resonance imaging evaluations. RESULTS: Cardiac stromal PW1+ cells undergo a change in paracrine behavior after MI, and the conditioned media from these cells induced a significant increase in the proliferation of fibroblasts. We identified a total of 12 candidates as secreted proteins overexpressed by cardiac PW1+ cells after MI. Among these factors, GDF3 (growth differentiation factor 3), a member of the TGF-ß (transforming growth factor-ß) family, was markedly upregulated in the ischemic hearts. Conditioned media specifically enriched with GDF3 induced fibroblast proliferation at a high level by stimulation of activin-receptor-like kinases. In line with the secretory nature of this protein, we next found that GDF3 can be detected in mice and human plasma samples, with a significant increase in the days after MI. In humans, higher GDF3 circulating levels (measured in the plasma at day 4 after MI) were significantly associated with an increased risk of adverse remodeling 6 months after MI (adjusted odds ratio, 1.76 [1.03-3.00]; P=0.037), including lower left ventricular ejection fraction and a higher proportion of akinetic segments. CONCLUSIONS: Our findings define a mechanism for the profibrotic action of cardiac stromal cells through secreted cardiokines, such as GDF3, a candidate marker of adverse fibrotic remodeling after MI. REGISTRATION: URL: https://www. CLINICALTRIALS: gov; Unique identifier: NCT01113268.

[Integrins in cardiac fibrosis]. / Rôle des intégrines dans la fibrose cardiaque.

For the last 20 years, integrins have been a therapeutic target of interest in the treatment of fibrotic diseases, particularly regarding the integrins of the αV family. Initially developed as anti-cancer drugs but with modest benefits, inhibitors of integrins (such as the anti-αV cilengitide) have shown interesting anti-fibrotic effects in different organs including the heart. Cardiac fibrosis is defined as an accumulation of stiff extracellular matrix in the myocardium, and ultimately leads to heart failure, one of the leading causes of mortality worldwide. Understanding the determinants of cardiac fibrosis and the involvement of integrins is a major matter of public health. This review presents the current knowledge on the different types of cardiac fibrosis and their etiologies, and report on first data supporting specific integrin inhibition therapy as a novel anti-fibrotic strategy, in particular to treat cardiac fibrosis.

Title: Rôle des intégrines dans la fibrose cardiaque. Abstract: Ces vingt dernières années, l'intérêt pour les intégrines n'a cessé de grandir et les découvertes ont ouvert de nouvelles perspectives thérapeutiques, notamment dans le cadre de la fibrose, particulièrement pour les intégrines de la famille aV. Après les revers de la thérapie anti-angiogénique utilisée contre le cancer, de nouvelles molécules inhibitrices de ces intégrines se sont révélées intéressantes pour le traitement de la fibrose tissulaire de différents organes, notamment le cœur. La fibrose cardiaque conduit à terme à l'insuffisance cardiaque, une des premières causes de mortalité dans le monde. La compréhension des déterminants de la fibrose cardiaque et l'implication des intégrines dans son développement représentent un enjeu majeur de santé publique. Dans cette revue, nous présentons les différents types de fibrose cardiaque et leurs étiologies. Nous évoquons ensuite les premières applications de stratégies anti-fibrosantes reposant sur l'inhibition d'intégrines spécifiques, comme traitement futur contre le développement de la fibrose cardiaque.

The beneficial effect of chronic muscular exercise on muscle fragility is increased by Prox1 gene transfer in dystrophic mdx muscle.

PURPOSE: Greater muscle fragility is thought to cause the exhaustion of the muscle stem cells during successive degeneration/repair cycles, leading to muscle wasting and weakness in Duchenne muscular dystrophy. Chronic voluntary exercise can partially reduce the susceptibility to contraction induced-muscle damage, i.e., muscle fragility, as shown by a reduced immediate maximal force drop following lengthening contractions, in the dystrophic mdx mice. Here, we studied the effect of Prospero-related homeobox factor 1 gene (Prox1) transfer (overexpression) using an AAV on fragility in chronically exercised mdx mice, because Prox1 promotes slower type fibres in healthy mice and slower fibres are less fragile in mdx muscle. METHODS: Both tibialis anterior muscles of the same mdx mouse received the transfer of Prox1 and PBS and the mice performed voluntary running into a wheel during 1 month. We also performed Prox1 transfer in sedentary mdx mice. In situ maximal force production of the muscle in response to nerve stimulation was assessed before, during and after 10 lengthening contractions. Molecular muscle parameters were also evaluated. RESULTS: Interestingly, Prox1 transfer reduced the isometric force drop following lengthening contractions in exercised mdx mice (p < 0.05 to 0.01), but not in sedentary mdx mice. It also increased the muscle expression of Myh7 (p < 0.001), MHC-2x (p < 0.01) and Trpc1 (p < 0.01), whereas it reduced that one of Myh4 (p < 0.001) and MHC-2b (p < 0.01) in exercised mdx mice. Moreover, Prox1 transfer decreased the absolute maximal isometric force (p < 0.01), but not the specific maximal isometric force, before lengthening contraction in exercised (p < 0.01) and sedentary mdx mice. CONCLUSION: Our results indicate that Prox1 transfer increased the beneficial effect of chronic exercise on muscle fragility in mdx mice, but reduced absolute maximal force. Thus, the potential clinical benefit of the transfer of Prox1 into exercised dystrophic muscle can merit further investigation.

FIBER-ML, an Open-Source Supervised Machine Learning Tool for Quantification of Fibrosis in Tissue Sections.

Pathologic fibrosis is a major hallmark of tissue insult in many chronic diseases. Although the amount of fibrosis is recognized as a direct indicator of the extent of disease, there is no consentaneous method for its quantification in tissue sections. This study tested FIBER-ML, a semi-automated, open-source freeware that uses a machine-learning approach to quantify fibrosis automatically after a short user-controlled learning phase. Fibrosis was quantified in sirius red-stained tissue sections from two fibrogenic animal models: acute stress-induced cardiomyopathy in rats (Takotsubo syndrome-like) and HIV-induced nephropathy in mice (chronic kidney disease). The quantitative results of FIBER-ML software version 1.0 were compared with those of ImageJ in Takotsubo syndrome, and with those of inForm in chronic kidney disease. Intra- and inter-operator and inter-software correlation and agreement were assessed. All correlations were excellent (>0.95) in both data sets. The values of discriminatory power between the pathologic and healthy groups were <10-3 for data on Takotsubo syndrome and <10-4 for data on chronic kidney disease. Intra-operator agreement, assessed by intra-class coefficient correlation, was good (>0.8), while inter-operator and inter-software agreement ranged from moderate to good (>0.7). FIBER-ML performed in a fast and user-friendly manner, with reproducible and consistent quantification of fibrosis in tissue sections. It offers an open-source alternative to currently used software, including quality control and file management.

Cytotoxic CD8+ T cells promote granzyme B-dependent adverse post-ischemic cardiac remodeling.

Acute myocardial infarction is a common condition responsible for heart failure and sudden death. Here, we show that following acute myocardial infarction in mice, CD8+ T lymphocytes are recruited and activated in the ischemic heart tissue and release Granzyme B, leading to cardiomyocyte apoptosis, adverse ventricular remodeling and deterioration of myocardial function. Depletion of CD8+ T lymphocytes decreases apoptosis within the ischemic myocardium, hampers inflammatory response, limits myocardial injury and improves heart function. These effects are recapitulated in mice with Granzyme B-deficient CD8+ T cells. The protective effect of CD8 depletion on heart function is confirmed by using a model of ischemia/reperfusion in pigs. Finally, we reveal that elevated circulating levels of GRANZYME B in patients with acute myocardial infarction predict increased risk of death at 1-year follow-up. Our work unravels a deleterious role of CD8+ T lymphocytes following acute ischemia, and suggests potential therapeutic strategies targeting pathogenic CD8+ T lymphocytes in the setting of acute myocardial infarction.

Anti-integrin αv therapy improves cardiac fibrosis after myocardial infarction by blunting cardiac PW1+ stromal cells.

There is currently no therapy to limit the development of cardiac fibrosis and consequent heart failure. We have recently shown that cardiac fibrosis post-myocardial infarction (MI) can be regulated by resident cardiac cells with a fibrogenic signature and identified by the expression of PW1 (Peg3). Here we identify αV-integrin (CD51) as an essential regulator of cardiac PW1+ cells fibrogenic behavior. We used transcriptomic and proteomic approaches to identify specific cell-surface markers for cardiac PW1+ cells and found that αV-integrin (CD51) was expressed in almost all cardiac PW1+ cells (93% ± 1%), predominantly as the αVß1 complex. αV-integrin is a subunit member of the integrin family of cell adhesion receptors and was found to activate complex of latent transforming growth factor beta (TGFß at the surface of cardiac PW1+ cells. Pharmacological inhibition of αV-integrin reduced the profibrotic action of cardiac PW1+CD51+ cells and was associated with improved cardiac function and animal survival following MI coupled with a reduced infarct size and fibrotic lesion. These data identify a targetable pathway that regulates cardiac fibrosis in response to an ischemic injury and demonstrate that pharmacological inhibition of αV-integrin could reduce pathological outcomes following cardiac ischemia.

Desmin prevents muscle wasting, exaggerated weakness and fragility, and fatigue in dystrophic mdx mouse.

KEY POINTS: Desmin, similar to dystrophin, is associated with costameric structures bridging sarcomeres to the extracellular matrix. Deletion of the desmin gene in mdx mice [double knockout (DKO) mice] induces marked muscle weakness and fatigue resistance compared to mdx mice. Muscle fragility (higher susceptibility to contraction-induced injury) was also aggravated in DKO mice compared to mdx mice. By contrast to mdx mice, the DKO mice did not undergo muscle hypertrophy. Desmin cDNA transfer with adeno-associated virus in newborn mdx mice reduced muscle weakness. Overall, desmin plays important and beneficial roles in muscle wasting, performance and fragility in dystrophic muscle. ABSTRACT: Duchenne muscular dystrophy (DMD) is a severe neuromuscular disease caused by dystrophin deficiency. Desmin, similar to dystrophin, is associated with costameric structures bridging sarcomeres to the extracellular matrix that contributes to muscle function. In the present study, we attempted to provide further insight into the roles of desmin, for which the expression is increased in the muscle from the mouse mdx DMD model. We show that a deletion of the desmin gene (Des) in mdx mice [double knockout (DKO) mice, mdx:desmin-/-] induces a marked muscle weakness; namely, a reduced absolute maximal force production and increased fatigue compared to that in mdx mice. Fragility (i.e. higher susceptibility to contraction-induced injury) was also aggravated in DKO mice compared to mdx mice, despite the promotion of supposedly less fragile muscle fibres in DKO mice, and this worsening of fragility was related to a decreased muscle excitability. Moreover, in contrast to mdx mice, the DKO mice did not undergo muscle hypertrophy, as indicated by smaller and fewer fibres, with a reduced percentage of centronucleated fibres, potentially explaining the severe muscle weakness. Notably, Desmin cDNA transfer with adeno-associated virus in newborn mdx mice improved specific maximal force normalized to muscle weight. Overall, desmin plays important and beneficial roles in muscle wasting, performance and fragility in dystrophic mdx mice, which differ, at least in part, from those observed in healthy muscle.

Improvement of Dystrophic Muscle Fragility by Short-Term Voluntary Exercise through Activation of Calcineurin Pathway in mdx Mice.

Dystrophin deficiency in mdx mice, a model for Duchenne muscular dystrophy, leads to muscle weakness revealed by a reduced specific maximal force as well as fragility (ie, higher susceptibility to contraction-induced injury, as shown by a greater force decrease after lengthening contractions). Both symptoms could be improved with dystrophin restoration-based therapies and long-term (months) voluntary exercise. Herein, we evaluated the effect of short-term (1-week) voluntary wheel running. We found that running improved fragility of tibialis anterior muscle (TA), but not plantaris muscle, independently of utrophin up-regulation, without affecting weakness. Moreover, TA muscle excitability was also preserved by running, as shown by compound muscle action potential measurements after lengthening contractions. Of interest, the calcineurin inhibitor cyclosporin A prevented the effect of running on both muscle fragility and excitability. Cyclosporin also prevented the running-induced changes in expression of genes involved in excitability (Scn4a and Cacna1s) and slower contractile phenotype (Myh2 and Tnni1) in TA muscle. In conclusion, short-term voluntary exercise improves TA muscle fragility in mdx mice, without worsening weakness. Its effect was related to preserved excitability, calcineurin pathway activation, and changes in the program of genes involved in excitability and slower contractile phenotype. Thus, remediation of muscle fragility of Duchenne muscular dystrophy patients through appropriate exercise training deserves to be explored in more detail.