Biomarkers for Duchenne muscular dystrophy: myonecrosis, inflammation and oxidative stress.

Duchenne muscular dystrophy (DMD) is a lethal, X-linked disease that causes severe loss of muscle mass and function in young children. Promising therapies for DMD are being developed, but the long lead times required when using clinical outcome measures are hindering progress. This progress would be facilitated by robust molecular biomarkers in biofluids, such as blood and urine, which could be used to monitor disease progression and severity, as well as to determine optimal drug dosing before a full clinical trial.

Macrophage Depletion in Elderly Mice Improves Response to Tumor Immunotherapy, Increases Anti-tumor T Cell Activity and Reduces Treatment-Induced Cachexia.

Most cancers emerge in the elderly, including lung cancer and mesothelioma, yet the elderly remain an underrepresented population in pre-clinical cancer studies and clinical trials. The immune system plays a critical role in the effectiveness of many anti-cancer therapies in young hosts via tumor-specific T cells. However, immunosuppressive macrophages can constitute up to 50% of the tumor burden and impair anti-tumor T cell activity.

Aged neutrophils accumulate in lymphoid tissues from healthy elderly mice and infiltrate T- and B-cell zones.

The average age of the human population is rising, leading to an increasing burden of age-related diseases, including increased susceptibility to infection. However, immune function can decrease with age which could impact on processes that require a functional immune system. Aging is also characterized by chronic low-grade inflammation which could further impact immune cell function.

Molecular analyses provide insight into mechanisms underlying sarcopenia and myofibre denervation in old skeletal muscles of mice.

Molecular mechanisms that are associated with age-related denervation and loss of skeletal muscle mass and function (sarcopenia) are described for female C57Bl/6J mice aged 3, 15, 24, 27 and 29 months (m). Changes in mRNAs and proteins associated with myofibre denervation and protein metabolism in ageing muscles are reported, across the transition from healthy adult myofibres to sarcopenia that occurs between 15 and 24 m. This onset of sarcopenia at 24 m, corresponded with increased expression of genes associated with neuromuscular junction denervation including Chnrg, Chrnd, Ncam1, Runx1, Gadd45a and Myog.

Lipid accumulation in dysferlin-deficient muscles.

Dysferlin is a membrane associated protein involved in vesicle trafficking and fusion. Defects in dysferlin result in limb-girdle muscular dystrophy type 2B and Miyoshi myopathy in humans and myopathy in A/J(dys-/-) and BLAJ mice, but the pathomechanism of the myopathy is not understood. Oil Red O staining showed many lipid droplets within the psoas and quadriceps muscles of dysferlin-deficient A/J(dys-/-) mice aged 8 and 12 months, and lipid droplets were also conspicuous within human myofibers from patients with dysferlinopathy (but not other myopathies).

Dystropathology increases energy expenditure and protein turnover in the mdx mouse model of duchenne muscular dystrophy.

The skeletal muscles in Duchenne muscular dystrophy and the mdx mouse model lack functional dystrophin and undergo repeated bouts of necrosis, regeneration, and growth. These processes have a high metabolic cost. However, the consequences for whole body energy and protein metabolism, and on the dietary requirements for these macronutrients at different stages of the disease, are not well-understood.

Targeting macrophages rescues age-related immune deficiencies in C57BL/6J geriatric mice.

Changes to innate cells, such as macrophages and myeloid-derived suppressor cells (MDSCs), during aging in healthy or tumor-bearing hosts are not well understood. We compared macrophage subpopulations and MDSCs from healthy young (6-8 weeks) C57BL/6J mice to those from healthy geriatric (24-28 months) mice. Spleens, lymph nodes, and bone marrow of geriatric hosts contained significantly more M2 macrophages and MDSCs than their younger counterparts.

Oxidative stress and pathology in muscular dystrophies: focus on protein thiol oxidation and dysferlinopathies.

The muscular dystrophies comprise more than 30 clinical disorders that are characterized by progressive skeletal muscle wasting and degeneration. Although the genetic basis for many of these disorders has been identified, the exact mechanism for pathogenesis generally remains unknown. It is considered that disturbed levels of reactive oxygen species (ROS) contribute to the pathology of many muscular dystrophies.

N-Acetylcysteine treatment of dystrophic mdx mice results in protein thiol modifications and inhibition of exercise induced myofibre necrosis.

Oxidative stress is implicated as a factor that increases necrosis of skeletal muscles in Duchenne Muscular Dystrophy (DMD) and the dystrophic mdx mouse. Consequently, drugs that minimize oxidative stress are potential treatments for muscular dystrophy. This study examined the in vivo benefits to mdx mice of an antioxidant treatment with the cysteine precursor N-acetylcysteine (NAC), administered in drinking water.

The different impact of a high fat diet on dystrophic mdx and control C57Bl/10 mice.

The absence of functional dystrophin protein in patients with Duchenne muscular dystrophy (DMD) and dystrophic mdx mice leads to fragile myofibre membranes and cycles of myofibre necrosis and regeneration. It is proposed that both DMD patients and mdx mice have an altered metabolism and impaired energy status and that nutritional supplementation may reduce the severity of dystropathology. This research compares the in vivo responses of dystrophic mdx and normal control C57Bl/10 mice to a high protein (50%) or a high fat (16%) diet.

A single 30 min treadmill exercise session is suitable for 'proof-of concept studies' in adult mdx mice: a comparison of the early consequences of two different treadmill protocols.

The extent of muscle pathology in sedentary adult mdx mice is very low and treadmill exercise is often used to increase myofibre necrosis; however, the early events in dystrophic muscle and blood in response to treadmill exercise (leading to myofibre necrosis) are unknown. This study describes in detail two standardised protocols for the treadmill exercise of mdx mice and profiles changes in molecular and cellular events after a single 30 min treadmill session (Protocol A) or after 4 weeks of (twice weekly) treadmill exercise (Protocol B). Both treadmill protocols increased multiple markers of muscle damage.

Identification of muscle necrosis in the mdx mouse model of Duchenne muscular dystrophy using three-dimensional optical coherence tomography.

Three-dimensional optical coherence tomography (3D-OCT) was used to image the structure and pathology of skeletal muscle tissue from the treadmill-exercised mdx mouse model of human Duchenne muscular dystrophy. Optical coherence tomography (OCT) images of excised muscle samples were compared with co-registered hematoxylin and eosin-stained and Evans blue dye fluorescence histology. We show, for the first time, structural 3D-OCT images of skeletal muscle dystropathology well correlated with co-located histology.

Myofiber Damage Evaluation by Evans Blue Dye Injection.

Evans blue dye (EBD) can be used in live mice to study muscle pathology or injury, including exercise-induced muscle damage. EBD is excluded from intact cell membranes but leaks into cells, including muscle fibers, when the cell membrane is ruptured. EBD can be visualized by its autofluorescence under a fluorescence microscope.