Fish oil attenuated dystrophic muscle markers of inflammation via FFA1 and FFA4 in the mdx mouse model of DMD.

In the present study we investigated the involvement of free fatty acid (FFA) receptors in the anti-inflammatory role of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in dystrophic muscles, by administering FFA blockers in the mdx mouse model of dystrophy. Mdx mice (3 months-old) were treated with fish oil capsules (FDC Vitamins; 0.4 g EPA and 0.2 g DHA; gavage) alone or concomitant to FFA1 and FFA4 blockers (GW1100 and AH7614; i.p.). C57BL/10 mice (3 months-old) and untreated-mdx mice received mineral oil and were used as controls. After 1 month of treatment, plasma markers of myonecrosis (total and cardiac creatine kinase; CK), the levels of FFA1 and FFA4 and of the markers of inflammation, nuclear transcription factor kappa B (NFkB), tumor necrosis factor alpha (TNF-α) and interleukin 1ß (IL-1ß) were analyzed in the diaphragm muscle and heart by western blot. Fish oil significantly reduced total CK, cardiac CK and the levels of NFkB (diaphragm), and of TNF-α and IL-1ß (diaphragm and heart) in mdx. In the dystrophic diaphragm, FFA1 was increased compared to normal. Blockers of FFA1 and FFA4 significantly inhibited the effects of fish oil treatment in both dystrophic muscles. The anti-inflammatory effects of fish oil in dystrophic diaphragm muscle and heart were mediated through FFA1 and FFA4.

No presente estudo investigamos o envolvimento de receptores de ácidos graxos livres (FFA) no efeito anti-inflamatório dos ácidos eicosapentaenoico (EPA) e docosahexaenoico (DHA) em músculos distróficos, administrando bloqueadores de FFA no camundongo mdx, modelo de distrofia. Camundongos mdx (3 meses de idade) foram tratados com cápsulas de óleo de peixe (FDC Vitamins; 0.4 g EPA e 0.2 g DHA; gavagem) ou com cápsulas de óleo de peixe concomitante a bloqueadores de FFA1 e FFA4 (GW1100 e AH7614; i.p.). Camundongos C57BL/10 (3 meses de idade) e camundongos mdx não tratados receberam óleo mineral e serviram de controle. Após 1 mês de tratamento, marcadores plasmáticos de mionecrose (creatina quinase total e cardíaca; CK), os níveis de FFA1 e FFA4 e dos marcadores de inflamação fator de transcrição nuclear kappa B (NFkB, nuclear transcription factor kappa B), fator de necrose tumoral alpha (TNF-α, tumor necrosis factor alpha) e interleucina 1ß (IL-1ß) foram analisados no músculo diafragma e no coração através de western blot. O óleo de peixe reduziu de forma significativa a CK total, CK cardíaca e os níveis de NFkB (diafragma), TNF-α e IL-1ß (diafragma e coração) no mdx. No diafragma distrófico, FFA1 estava aumentado comparado ao normal. Os bloqueadores de FFA1 e FFA4 inibiram de forma significativa os efeitos do tratamento com óleo de peixe em ambos músculos distróficos. Os efeitos anti-inflamatórios do óleo de peixe nos músculos distróficos diafragma e cardíaco foram mediados por FFA1 e FFA4.

Cardiac and skeletal muscle changes associated with rosuvastatin therapy in dystrophic mdx mice.

Statins are prescribed to prevent and treat atherosclerotic cardiovascular and metabolic diseases but have controversial effects on skeletal muscles. While statins are a reported cause of myopathy, some studies have suggested that statins could potentially ameliorate dystrophy due to their pleiotropic effects on inflammation, myonecrosis, and autophagy. In the present study, we evaluated the potential benefit of rosuvastatin treatment on heart, limb, and diaphragm muscles in dystrophin-deficient mdx mice at an early stage (45 days of age) of disease. Mdx mice received rosuvastatin (10 mg/kg) by gavage for 30 days beginning at 15 days of age. Normal C57BL/10 mice received rosuvastatin by the same route over the same interval. In the mdx group, rosuvastatin significantly increased IgG-positive fibers (myonecrosis) and the inflammatory areas in the biceps brachii and diaphragm muscles and decreased the anterior limb muscle force (grip strength). Molecular markers of inflammation (TNF-α and NF-kB) and fibrosis (fibronectin) were not altered by rosuvastatin in mdx mice skeletal and cardiac muscles. In normal mice, rosuvastatin increased CK, TNF-α (heart), NF-kB (diaphragm), and fibronectin (heart and diaphragm). Inflammatory areas were seen in all normal muscles of rosuvastatin-treated mice. Rosuvastatin did not benefit dystrophy in the mdx mice and was associated with inflammation in normal cardiac and skeletal muscles.

Identification of plasma interleukins as biomarkers for deflazacort and omega-3 based Duchenne muscular dystrophy therapy.

Duchenne muscular dystrophy (DMD) is a progressive and fatal disease, characterized by the absence of dystrophin, muscle degeneration and cardiorespiratory failure. Creatine kinase is the classic marker to screen for DMD. However, other markers are needed to follow disease progression and to evaluate the response to therapy over longer periods. In the present study, we aim to identify interleukins in the plasma of the mdx mice model of DMD that could serve as biomarkers to monitor dystrophy progression, at distinct stages of the disease (1, 3 and 8 months of age). We used deflazacort and omega-3 therapies to validate the biomarkers studied. Plasma levels of TNF-α and TGF-ß were increased in mdx mice in relation to control, at all times studied. Differences in IFN-γ and IL-10 contents, comparing mdx x CTRL, were detected only at the early stage (1 month). IL-6 decreased at 3 and 8 months and IL-13 increased at 8 months in the mdx compared to control. Deflazacort and omega-3 reduced the plasma levels of the pro-inflammatory (TNF-α, INF-γ, IL-6) and pro-fibrotic (IL-13 and TGF-ß) interleukins and increased the plasma levels of IL-10. It is suggested that TNF-α and TGF-ß in plasma would be the best markers to follow disease progression. IL-6, INF-γ and IL-10 would be suitable markers to the earlier stages of dystrophy and IL-13 a suitable marker to the later stages of dystrophy.

Effects of dietary omega-3 on dystrophic cardiac and diaphragm muscles as evaluated by 1H magnetic resonance spectroscopy: Metabolic profile and calcium-related proteins.

BACKGROUND & AIMS: Duchenne muscular dystrophy (DMD) is characterized by the absence of dystrophin and muscle degeneration. Calcium dysregulation and oxidative stress also contribute to the disease progression. We evaluated the potential therapeutic benefits of supplementation with omega-3 on the metabolic profile, calcium-related proteins and oxidative stress response in the heart and diaphragm (DIA) of the mdx mouse model of DMD at later stages of the disease (13 months). METHODS: Mdx mice (8 months old) received omega-3 via a dietary supplement for 5 months. Metabolites were analyzed by 1H magnetic resonance spectroscopy. Muscle total calcium was evaluated by inductively coupled plasma-optical emission spectrometry. Calsequestrin, TRPC1 and 4-HNE were determined via Western blot. RESULTS: Omega-3 decreased the metabolites taurine (related to calcium regulation and oxidative stress), aspartate (related to inflammation) and oxypurinol (related to oxidative stress) in the heart (aspartate) and DIA (taurine, aspartate and oxypurinol). Omega-3 also significantly decreased total calcium and TRPC1 levels in cardiac and DIA muscles and increased the levels of calsequestrin (cardiac and skeletal) and decreased the oxidative stress marker 4-HNE. CONCLUSIONS: The current study suggests that supplementation with omega-3 may generate therapeutic benefits on dystrophy progression, at later stages of the disease, with changes in the metabolic profile that may be correlated to omega-3 therapy.

P2Y2 purinergic receptors are highly expressed in cardiac and diaphragm muscles of mdx mice, and their expression is decreased by suramin.

INTRODUCTION: In Duchenne muscular dystrophy (DMD) and in the mdx mouse model of DMD, the lack of dystrophin leads to increased calcium influx and muscle necrosis. Patients suffer progressive muscle loss, and cardiomyopathy is an important determinant of morbidity. P2 purinergic receptors participate in the increased calcium levels in dystrophic skeletal muscles. METHODS: In this study, we evaluated whether P2 receptors are involved in cardiomyopathy in mdx mice at later stages of the disease. RESULTS: Western blotting revealed that P2Y2 receptor levels were upregulated (54%) in dystrophic heart compared with a normal heart. Suramin reduced the levels of P2Y2 to almost normal values. Suramin also decreased heart necrosis (reduced CK-MB) and the expression of the stretch-activated calcium channel TRPC1. CONCLUSIONS: This study suggests that P2Y2 may participate in cardiomyopathy in mdx mice. P2-selective drugs with specific actions in the dystrophic heart may ameliorate cardiomyopathy in dystrophinopathies. Muscle Nerve 55: 116-121, 2017.

Effects of fish oil containing eicosapentaenoic acid and docosahexaenoic acid on dystrophic mdx mice hearts at later stages of dystrophy.

OBJECTIVE: In the present study, we investigated whether omega-3 would be effective against dystrophic cardiomyopathy at later stages (13 and 17 mo) of the disease. METHODS: Mdx mice (8 mo old) received omega-3 oil (commercially available fish oil; FDC vitamins; omega-3) for 5 mo. Untreated-mdx mice received mineral oil. Heart and diaphragm muscle were evaluated by morphometric (fibrosis), molecular (western blot, inflammatory markers), biochemical (creatine kinase), and functional (electrocardiogram) analyses. RESULTS: Mdx mice presented elevated plasma levels of cardiac creatine kinase (41.2 U/L in normal × 119.6 U/L in untreated-mdx mice), which were significantly decreased by omega-3 treatment. Heart fibrosis was significantly ameliorated by omega-3 treatment at 17 mo of age (untreated-mdx: 20.8% of fibrosis; omega-3-treated: 15.7% of fibrosis in right ventricle). Omega-3 improved some electrocardiogram parameters. Markers of inflammation (tumor necrosis factor alpha, matrix metalloprotease-9, and tissue inhibitor of metalloprotease 1) in mdx heart were significantly decreased by omega-3 treatment. Omega-3 increased ß-dystroglycan levels in mdx heart and did not affect the levels of the profibrotic transforming growth factor beta. Omega-3 ameliorated the dystrophic diaphragm in almost all of the parameters evaluated (fibrosis, transforming growth factor beta, metalloprotease-9, and tissue inhibitor of metalloprotease 1). CONCLUSIONS: The present study suggests that omega-3 may be useful in ameliorating dystrophic cardiomyopathy and diaphragm dystrophy in mdx mice at later stages of the disease, further supporting the use of omega-3 in DMD clinical trials.

Diaphragm degeneration and cardiac structure in mdx mouse: potential clinical implications for Duchenne muscular dystrophy.

We examined the effects of exercise on diaphragm degeneration and cardiomyopathy in dystrophin-deficient mdx mice. Mdx mice (11 months of age) were exercised (swimming) for 2 months to worsen diaphragm degeneration. Control mdx mice were kept sedentary. Morphological evaluation demonstrated increased fibrosis in the diaphragm of exercised mdx mice (33.3 ± 6.0% area of fibrosis) compared with control mdx mice (20.9 ± 1.7% area of fibrosis). Increased (26%) activity of MMP-2, a marker of fibrosis, was detected in the diaphragms from exercised mdx mice. Morphological evaluation of the heart demonstrated a 45% increase in fibrosis in the right ventricle (8.3 ± 0.6% in sedentary vs. 12.0 ± 0.6% of fibrosis in exercised) and in the left ventricle (35% increase) in the exercised mdx mice. The density of inflammatory cells-degenerating cardiomyocytes increased 95% in the right ventricle (2.3 ± 0.6 in sedentary vs. 4.5 ± 0.8 in exercised) and 71% in the left ventricle (1.4 ± 0.6 sedentary vs. 2.4 ± 0.5 exercised). The levels of both active MMP-2 and the pro-fibrotic factor transforming growth factor beta were elevated in the hearts of exercised compared with sedentary mdx mice. The wall thickness to lumen diameter ratio of the pulmonary trunk was significantly increased in the exercised mdx mice (0.11 ± 0.04 in sedentary vs. 0.28 ± 0.12 in exercised), as was the thickness of the right ventricle wall, which suggests the occurrence of pulmonary hypertension in those animals. It is suggested that diaphragm degeneration is a main contributor to right ventricle dystrophic pathology. These findings may be relevant for future interventional studies for Duchenne muscular dystrophy-associated cardiomyopathy.

Changes in calsequestrin, TNF-α, TGF-ß and MyoD levels during the progression of skeletal muscle dystrophy in mdx mice: a comparative analysis of the quadriceps, diaphragm and intrinsic laryngeal muscles.

In Duchenne muscular dystrophy (DMD), the search for new biomarkers to follow the evolution of the disease is of fundamental importance in the light of the evolving gene and pharmacological therapies. In addition to the lack of dystrophin, secondary events including changes in calcium levels, inflammation and fibrosis greatly contribute to DMD progression and the molecules involved in these events may represent potential biomarkers. In this study, we performed a comparative evaluation of the progression of dystrophy within muscles that are differently affected by dystrophy (diaphragm; DIA and quadriceps; QDR) or spared (intrinsic laryngeal muscles) using the mdx mice model of DMD. We assessed muscle levels of calsequestrin (calcium-related protein), tumour necrosis factor (TNF-α; pro-inflammatory cytokine), tumour growth factor (TGF-ß; pro-fibrotic factor) and MyoD (muscle proliferation) vs. histopathology at early (1 and 4 months of age) and late (9 months of age) stages of dystrophy. Fibrosis was the primary feature in the DIA of mdx mice (9 months: 32% fibrosis), which was greater than in the QDR (9 months: 0.6% fibrosis). Muscle regeneration was the primary feature in the QDR (9 months: 90% of centrally nucleated fibres areas vs. 33% in the DIA). The QDR expressed higher levels of calsequestrin than the DIA. Laryngeal muscles showed normal levels of TNF-α, TGF-ß and MyoD. A positive correlation between histopathology and cytokine levels was observed only in the diaphragm, suggesting that TNF-α and TGF-ß serve as markers of dystrophy primarily for the diaphragm.

Expression of calcium-buffering proteins in rat intrinsic laryngeal muscles.

Intrinsic laryngeal muscles (ILM) are highly specialized muscles involved in phonation and airway protection, with unique properties that allow them to perform extremely rapid contractions and to escape from damage in muscle dystrophy. Due to that, they may differ from limb muscles in several physiological aspects. Because a better ability to handle intracellular calcium has been suggested to explain ILM unique properties, we hypothesized that the profile of the proteins that regulate calcium levels in ILM is different from that in a limb muscle. Calcium-related proteins were analyzed in the ILM, cricothyroid (CT), and tibialis anterior (TA) muscles from male Sprague-Dawley rats (8 weeks of age) using quantitative PCR and western blotting. Higher expression of key Ca(2+) regulatory proteins was detected in ILM compared to TA, such as the sarcoplasmic reticulum (SR) Ca(2+)-reuptake proteins (Sercas 1 and 2), the Na(+)/Ca(2+) exchanger, phospholamban, and the Ca(2+)-binding protein calsequestrin. Parvalbumin, calmodulin and the ATPase, Ca(2+)-transporting, and plasma membrane 1 were also expressed at higher levels in ILM compared to TA. The store-operated calcium entry channel molecule was decreased in ILM compared to the limb muscle and the voltage-dependent L-type and ryanodine receptor were expressed at similar levels in ILM and TA. These results show that ILM have a calcium regulation system profile suggestive of a better ability to handle calcium changes in comparison to limb muscles, and this may provide a mechanistic insight for their unique pathophysiological properties.

Long-Term Therapy With Omega-3 Ameliorates Myonecrosis and Benefits Skeletal Muscle Regeneration in Mdx Mice.

In Duchenne muscle dystrophy (DMD) and in the mdx mouse model of DMD, a lack of dystrophin leads to myonecrosis and cardiorespiratory failure. Several lines of evidence suggest a detrimental role of the inflammatory process in the dystrophic process. Previously, we demonstrated that short-term therapy with eicosapentaenoic acid (EPA), at early stages of disease, ameliorated dystrophy progression in the mdx mouse. In the present study, we evaluated the effects of a long-term therapy with omega-3 later in dystrophy progression. Three-month-old mdx mice received omega-3 (300 mg/kg) or vehicle by gavage for 5 months. The quadriceps and diaphragm muscles were removed and processed for histopathology and Western blot. Long-term therapy with omega-3 increased the regulatory protein MyoD and muscle regeneration and reduced markers of inflammation (TNF-α and NF-kB) in both muscles studied. The present study supports the long-term use of omega-3 at later stages of dystrophy as a promising option to be investigated in DMD clinical trials.

Co-administration of deflazacort and doxycycline: a potential pharmacotherapy for Duchenne muscular dystrophy.

The standard therapy used in the treatment of Duchenne muscle dystrophy (DMD) is corticoids, such as deflazacort and prednisone. However, they have limited therapeutic value, and their combination with drugs already in use to treat other human diseases could potentially increase corticoid outcomes in DMD. In the present study, we evaluated whether a combined therapy of the corticoid deflazacort with doxycycline could result in greater improvement in mdx dystrophy than deflazacort alone. Deflazacort alone or deflazacort/doxycycline were administered for 36 days (starting on postnatal day 0) in drinking water. Histopathological, biochemical (creatine kinase), functional (forelimb muscle grip strength and fatigue) parameters and inflammatory markers (MMP-9, TNF-α, NF-kB) were evaluated in biceps brachii and diaphragm muscles of the mdx mice. The combined therapy was superior in improving the dystrophic phenotype compared to monotherapy. The primary results were observed in attenuating muscle fatigue, decreasing muscle total calcium and inflammatory markers and increasing ß-dystroglycan, a main component of the dystrophin-protein complex. Furthermore, the combined therapy was effective in preventing the loss of body mass observed with deflazacort alone at this very early stage of therapy. The present study offers preclinical data to support further studies with deflazacort/doxycycline combined therapy in DMD clinical trials.

Understanding the beneficial effects of doxycycline on the dystrophic phenotype of the mdx mouse.

INTRODUCTION: The purpose of this study was to better understand the beneficial effects of doxycycline on the dystrophic muscles of the mdx mouse. METHODS: Doxycycline (DOX) was administered for 36 days, starting on postnatal day 0, via drinking water. Untreated mdx mice received plain water for the same period and served as a control group. RESULTS: DOX decreased the levels of metalloproteinase-9 and tumor necrosis factor-alpha in the biceps brachii and diaphragm of the mdx mice. It also reduced the total amount of calcium in the muscles studied, concomitant with an increase in the levels of calsequestrin 1. CONCLUSIONS: The results show that DOX can affect factors that are important in dystrophic pathogenesis and highlight its potential as a readily accessible therapy in clinical trials for treatment of Duchenne muscular dystrophy.

EPA protects against muscle damage in the mdx mouse model of Duchenne muscular dystrophy by promoting a shift from the M1 to M2 macrophage phenotype.

In dystrophic mdx mice and in Duchenne muscular dystrophy, inflammation contributes to myonecrosis. Previously, we demonstrated that eicosapentaenoic acid (EPA) decreased inflammation and necrosis in dystrophic muscle. In the present study, we examined the effects of EPA and the corticoid deflazacort (DFZ) as modulators of M1 (iNOS-expressing cells) and M2 (CD206-expressing cells) macrophages. Mdx mice (14 days old) received EPA or DFZ for 16 days. The diaphragm, biceps brachii and quadriceps muscles were studied. Immunofluorescence, immunoblotting and ELISA assays showed that EPA increased interleucin-10, reduced interferon-γ and was more effective than DFZ in promoting a shift from M1 to M2.

Effects of fish oil containing eicosapentaenoic acid and docosahexaenoic acid on dystrophic mdx mice.

BACKGROUND & AIMS: In Duchenne muscular dystrophy (DMD) and in the mdx mouse model of DMD, the lack of dystrophin leads to muscle degeneration and inflammation contributes to progression of the disease. In this study, we evaluated the effects of commercially available fish oil containing EPA and docosahexaenoic acid (DHA) on mdx. METHODS: Mdx mice (14 days old) were treated with fish oil (FDC Vitamins; 0.002 g EPA and 0.001 g DHA) for 16 days by gavage. Control mdx mice received mineral oil (Nujol). Grip strength measurement was used for functional evaluation. The sternomastoid, diaphragm and biceps brachii muscles were removed and processed for histopathology and Western blot analysis. RESULTS: Fish oil decreased creatine kinase and myonecrosis. In all muscles studied, the inflammatory area was significantly reduced after treatment (18.0 ± 3.0% inflammatory area in untreated mdx mice versus 4.0 ± 1% in treated mdx mice). Fish oil protected against the loss of muscle strength. Fish oil significantly reduced the levels of TNF-α and the levels of 4-HNE-protein adducts (30-34% reduction for both) in all muscles studied. CONCLUSIONS: Commercially available fish oil may be potentially useful to ameliorate dystrophic progression of skeletal muscles, deserving further clinical trials in DMD patients.

Suramin affects metalloproteinase-9 activity and increases ß-dystroglycan levels in the diaphragm of the dystrophin-deficient mdx mouse.

INTRODUCTION: In Duchenne muscular dystrophy and in the mdx mouse, muscle fiber degeneration and subsequent fibrosis lead to cardiorespiratory failure. Previously, we demonstrated that the anti-fibrotic agent suramin was effective in decreasing fibrosis in mdx muscles. In this study, we were interested to see whether suramin could affect metalloproteinases (MMP) and improve the functional activity of the mdx diaphragm muscle. METHODS: Zymography was performed to evaluate MMP-2 and MMP-9 activity. Western blotting was used to analyze the levels of beta-dystroglycan. Muscle function was assessed in hemidiaphragm in vitro preparations. RESULTS: We found that suramin affects metalloproteinase-9 activity and increases beta-dystroglycan. Furthermore, suramin also protects against diaphragm muscle fatigue over time. CONCLUSIONS: These results show the potential benefits of suramin in maintaining the structure of the dystrophin-glycoprotein complex.

Ascorbic acid protects the diaphragm muscle against myonecrosis in mdx mice.

OBJECTIVE: Oxidative stress contributes to myonecrosis in the dystrophin-deficient fibers of mdx mice and in Duchenne's muscular dystrophy. We examined the effects of ascorbic acid (AA), an antioxidant and free radical scavenger, on the dystrophic diaphragm muscle. METHODS: Mdx mice (14 d old) received AA for 14 d. Control mdx mice received saline. The muscle damage was visualized by the penetration of Evans blue dye into myofibers and the extent of inflammation was assessed by histologic analysis. Creatine kinase levels were measured for the biochemical evaluation of muscle fiber degeneration. The levels of tumor necrosis factor-α (a proinflammatory cytokine) and 4-hydroxynonenal (a marker of lipid peroxidation) were analyzed by immunoblotting. RESULTS: Ascorbic acid decreased creatine kinase levels, myonecrosis, inflammation, and the levels of tumor necrosis factor-α and 4-hydroxynonenal. CONCLUSION: The present results suggest that AA plays a protective role in dystrophic muscle degeneration, possibly by decreasing reactive oxygen species, and support further investigations of AA as a potential therapy for dystrophinopathies.

Age-related changes in dystrophin-glycoprotein complex and in utrophin are not correlated with intrinsic laryngeal muscles protection in mdx mice.

In this study we investigate whether dystrophic intrinsic laryngeal muscles (ILM) from aged mdx mice show alterations in dystrophin-glycoprotein complex (DGC) components.Immunofluorescence and immunoblotting analyses of beta-sarcoglycan, beta-dystroglycan, and utrophin showed that aged ILM had a similar pattern of changes in aged affected muscles (diaphragm and limb), suggesting that aging leads to changes in utrophin and DGC proteins in dystrophic ILM that cannot be correlated with their protection from dystrophic change.

Stretch-activated calcium channel protein TRPC1 is correlated with the different degrees of the dystrophic phenotype in mdx mice.

In Duchenne muscular dystrophy (DMD) and in the mdx mouse model of DMD, the lack of dystrophin is related to enhanced calcium influx and muscle degeneration. Stretch-activated channels (SACs) might be directly involved in the pathology of DMD, and transient receptor potential cation channels have been proposed as likely candidates of SACs. We investigated the levels of transient receptor potential canonical channel 1 (TRPC1) and the effects of streptomycin, a SAC blocker, in muscles showing different degrees of the dystrophic phenotype. Mdx mice (18 days old, n = 16) received daily intraperitoneal injections of streptomycin (182 mg/kg body wt) for 18 days, followed by removal of the diaphragm, sternomastoid (STN), biceps brachii, and tibialis anterior muscles. Control mdx mice (n = 37) were injected with saline. Western blot analysis showed higher levels of TRPC1 in diaphragm muscle compared with STN and limb muscles. Streptomycin reduced creatine kinase and prevented exercise-induced increases of total calcium and Evans blue dye uptake in diaphragm and in STN muscles. It is suggested that different levels of the stretch-activated calcium channel protein TRPC1 may contribute to the different degrees of the dystrophic phenotype seen in mdx mice. Early treatment designed to regulate the activity of these channels may ameliorate the progression of dystrophy in the most affected muscle, the diaphragm.

Surgical anatomy of the Guyon canal in children.

OBJECT: The anatomy of the Guyon canal is crucial for open and endoscopic surgeries for ulnar canal syndrome at the wrist level. It is also of interest for surgical treatment of carpal canal syndromes. Whereas the Guyon canal is largely described in adults, no studies exist in children. In the present study, the authors examined the Guyon canal in children. METHODS: Sectional anatomy was used. Thirty-two formalin-fixed cadavers (64 sides) were examined (age range 2-11 years). The hands were transversely cut into 2-3-mm-thick slices. Slices were placed in embedding medium, and transverse sections (10 µm thick) were stained with histological methods and photographed under a light microscope. RESULTS: The roof of the Guyon canal was attached to the flexor retinaculum laterally to the hamulus of the hamate bone. Thus, the radial boundary of the Guyon canal was lateral to the hamulus, which became part of the floor of the Guyon canal. An ulnar neurovascular bundle was found directly volar to the hamulus in 93.8% of the cases and slightly medial to the hamulus (to the ulnar side) in 6.2% of the cases. Proximally, the ulnar artery and nerve were sustained by the flexor retinaculum in direct apposition to the carpal canal. CONCLUSIONS: In children, the Guyon canal displays an anatomical particularity regarding the topography of the ulnar artery and nerve that may be of relevance for intraoperative orientation and endoscopic navigation to avoid lesions to the ulnar nerve and artery in carpal and Guyon canal syndromes.