Response to Electrostimulation Is Impaired in Muscle Cells from Patients with Chronic Obstructive Pulmonary Disease.

Among the comorbidities associated with chronic obstructive pulmonary disease (COPD), skeletal muscle weakness and atrophy are known to affect patient survival rate. In addition to muscle deconditioning, various systemic and intrinsic factors have been implicated in COPD muscle dysfunction but an impaired COPD muscle adaptation to contraction has never been extensively studied. We submitted cultured myotubes from nine healthy subjects and nine patients with COPD to an endurance-type protocol of electrical pulse stimulation (EPS). EPS induced a decrease in the diameter, covered surface and expression of MHC1 in COPD myotubes. Although the expression of protein degradation markers was not affected, expression of the protein synthesis marker mTOR was not induced in COPD compared to healthy myotubes after EPS. The expression of the differentiation markers p16INK4a and p21 was impaired, while expression of Myf5 and MyoD tended to be affected in COPD muscle cells in response to EPS. The expression of mitochondrial biogenesis markers PGC1α and MFN2 was affected and expression of TFAM and COX1 tended to be reduced in COPD compared to healthy myotubes upon EPS. Lipid peroxidation was increased and the expression of the antioxidant enzymes SOD2 and GPx4 was affected in COPD compared to healthy myotubes in response to EPS. Thus, we provide evidence of an impaired response of COPD muscle cells to contraction, which might be involved in the muscle weakness observed in patients with COPD.

Efficacy of a long-term pulmonary rehabilitation maintenance program for COPD patients in a real-life setting: a 5-year cohort study.

BACKGROUND: Pulmonary rehabilitation (PR) improves exercise capacity, health-related quality of life (HRQoL) and dyspnea in chronic obstructive pulmonary disease (COPD) patients. Maintenance programs can sustain the benefits for 12 to 24 months. Yet, the long-term effects (> 12 months) of pragmatic maintenance programs in real-life settings remain unknown. This prospective cohort study assessed the yearly evolution in the outcomes [6-min walking distance (6MWD), HRQoL, dyspnea] of a supervised self-help PR maintenance program for COPD patients followed for 5 years. The aim was to assess the change in the outcomes and survival probability for 1 to 5 years after PR program discharge in COPD patients following a PR maintenance program supported by supervised self-help associations. METHODS: Data were prospectively collected from 144 COPD patients who followed a pragmatic multidisciplinary PR maintenance program for 1 to 5 years. They were assessed yearly for 6MWD, HRQol (VQ11) and dyspnea (MRC). The 5-year survival probability was compared to that of a control PR group without a maintenance program. A trajectory-based cluster analysis identified the determinants of long-term response. RESULTS: Maintenance program patients showed significant PR benefits at 4 years for 6MWD and VQ11 and 5 years for MRC. The 5-year survival probability was higher than for PR patients without PR maintenance. Two clusters of response to long-term PR were identified, with responders being the less severe COPD patients. CONCLUSIONS: This study provides evidence of the efficacy of a pragmatic PR maintenance program in a real-life setting for more than 3 years. In contrast to short-term PR, long-term PR maintenance appeared more beneficial in less severe COPD patients.

COPD is deleterious for pericytes: implications during training-induced angiogenesis in skeletal muscle.

Improvements in skeletal muscle endurance and oxygen uptake are blunted in patients with chronic obstructive pulmonary disease (COPD), possibly because of a limitation in the muscle capillary oxygen supply. Pericytes are critical for capillary blood flow adaptation during angiogenesis but may be impaired by COPD systemic effects, which are mediated by circulating factors. This study compared the pericyte coverage of muscle capillaries in response to 10 wk of exercise training in patients with COPD and sedentary healthy subjects (SHS). Fourteen patients with COPD were compared with seven matched SHS. SHS trained at moderate intensity corresponding to an individualized moderate-intensity patient with COPD trained at the same relative (%V̇o2: COPD-RI) or absolute (mL·min-1·kg-1: COPD-AI) intensity as SHS. Capillary-to-fiber ratio (C/F) and NG2+ pericyte coverage were assessed from vastus lateralis muscle biopsies, before and after 5 and 10 wk of training. We also tested in vitro the effect of COPD and SHS serum on pericyte morphology and mesenchymal stem cell (MSC) differentiation into pericytes. SHS showed greater improvement in aerobic capacity (V̇o2VT) than both patients with COPD-RI and patients with COPD-AI (Group × Time: P = 0.004). Despite a preserved increase in the C/F ratio, NG2+ pericyte coverage did not increase in patients with COPD in response to training, contrary to SHS (Group × Time: P = 0.011). Conversely to SHS serum, COPD serum altered pericyte morphology (P < 0.001) and drastically reduced MSC differentiation into pericytes (P < 0.001). Both functional capacities and pericyte coverage responses to exercise training are blunted in patients with COPD. We also provide direct evidence of the deleterious effect of COPD circulating factors on pericyte morphology and differentiation.NEW & NOTEWORTHY This work confirms the previously reported impairment in the functional response to exercise training of patients with COPD compared with SHS. Moreover, it shows for the first time that pericyte coverage of the skeletal capillaries is drastically reduced in patients with COPD compared with SHS during training-induced angiogenesis. Finally, it provides experimental evidence that circulating factors are involved in the impaired pericyte coverage of patients with COPD.

Effects of a human microenvironment on the differentiation of human myoblasts.

Myogenic differentiation mechanisms are generally assessed using a murine cell line placed in low concentrations of an animal-derived serum. To more closely approximate in vivo pathophysiological conditions, recent studies have combined the use of human muscle cells with human serum. Nevertheless, the in vitro studies of the effects of a human microenvironment on the differentiation process of human myoblasts require the identification of the culture conditions that would provide an optimal and reproducible differentiation process of human muscle cells. We assessed the differentiation variability resulting from the use of human myoblasts and serums from healthy subjects by measuring the myotube diameter, fusion index and surface covered by myotubes. We showed the preserved cell-dependent variability of the differentiation response of myoblasts cultured in human serums compared to FBS. We found that using a pool of serums reduced the serum-dependent variability of the myogenic response compared to individual serums. We validated our methodology by showing the atrophying effect of pooled serums from COPD patients on healthy human myotubes. By replacing animal-derived tissues with human myoblasts and serums, and by validating the sensitivity of cultured human muscle cells to a pathological microenvironment, this human cell culture model offers a valuable tool for studying the role of the microenvironment in chronic disease.

Impaired training-induced angiogenesis process with loss of pericyte-endothelium interactions is associated with an abnormal capillary remodelling in the skeletal muscle of COPD patients.

Chronic obstructive pulmonary disease (COPD) is associated with exercise intolerance and limits the functional gains in response to exercise training in patients compared to sedentary healthy subjects (SHS). The blunted skeletal muscle angiogenesis previously observed in COPD patients has been linked to these limited functional improvements, but its underlying mechanisms, as well as the potential role of oxidative stress, remain poorly understood. Therefore, we compared ultrastructural indexes of angiogenic process and capillary remodelling by transmission electron microscopy in 9 COPD patients and 7 SHS after 6 weeks of individualized moderate-intensity endurance training. We also assessed oxidative stress by plasma-free and esterified isoprostane (F2-IsoP) levels in both groups. We observed a capillary basement membrane thickening in COPD patients only (p = 0.008) and abnormal variations of endothelial nucleus density in response to exercise training in these patients when compared to SHS (p = 0.042). COPD patients had significantly fewer occurrences of pericyte/endothelium interdigitations, a morphologic marker of capillary maturation, than SHS (p = 0.014), and significantly higher levels of F2-IsoP (p = 0.048). Last, the changes in pericyte/endothelium interdigitations and F2-IsoP levels in response to exercise training were negatively correlated (r = - 0.62, p = 0.025). This study is the first to show abnormal capillary remodelling and to reveal impairments during the whole process of angiogenesis (capillary creation and maturation) in COPD patients. TRIAL REGISTRATION: NCT01183039 & NCT01183052, both registered 7 August 2010 (retrospectively registered).

Oxidative stress regulates autophagy in cultured muscle cells of patients with chronic obstructive pulmonary disease.

The proteolytic autophagy pathway is enhanced in the lower limb muscles of patients with chronic obstructive pulmonary disease (COPD). Reactive oxygen species (ROS) have been shown to regulate autophagy in the skeletal muscles, but the role of oxidative stress in the muscle autophagy of patients with COPD is unknown. We used cultured myoblasts and myotubes from the quadriceps of eight healthy subjects and twelve patients with COPD (FEV1% predicted: 102.0% and 32.0%, respectively; p < 0.0001). We compared the autophagosome formation, the expression of autophagy markers, and the autophagic flux in healthy subjects and the patients with COPD, and we evaluated the effects of the 3-methyladenine (3-MA) autophagy inhibitor on the atrophy of COPD myotubes. Autophagy was also assessed in COPD myotubes treated with an antioxidant molecule, ascorbic acid. Autophagosome formation was increased in COPD myoblasts and myotubes (p = 0.011; p < 0.001), and the LC3 2/LC3 1 ratio (p = 0.002), SQSTM1 mRNA and protein expression (p = 0.023; p = 0.007), BNIP3 expression (p = 0.031), and autophagic flux (p = 0.002) were higher in COPD myoblasts. Inhibition of autophagy with 3-MA increased the COPD myotube diameter (p < 0.001) to a level similar to the diameter of healthy subject myotubes. Treatment of COPD myotubes with ascorbic acid decreased ROS concentration (p < 0.001), ROS-induced protein carbonylation (p = 0.019), the LC3 2/LC3 1 ratio (p = 0.037), the expression of SQSTM1 (p < 0.001) and BNIP3 (p < 0.001), and increased the COPD myotube diameter (p < 0.001). Thus, autophagy signaling is enhanced in cultured COPD muscle cells. Furthermore, the oxidative stress level contributes to the regulation of autophagy, which is involved in the atrophy of COPD myotubes in vitro.

Longitudinal Magnetic Resonance Imaging Analysis and Histological Characterization after Spinal Cord Injury in Two Mouse Strains with Different Functional Recovery: Gliosis as a Key Factor.

Spinal cord injuries (SCI) are disastrous neuropathologies causing permanent disabilities. The availability of different strains of mice is valuable for studying the pathophysiological mechanisms involved in SCI. However, strain differences have a profound effect on spontaneous functional recovery after SCI. CX3CR1+/eGFP and Aldh1l1-EGFP mice that express green fluorescent protein in microglia/monocytes and astrocytes, respectively, are particularly useful to study glial reactivity. Whereas CX3CR1+/eGFP mice have C57BL/6 background, Aldh1l1-EGFP are in Swiss Webster background. We first assessed spontaneous functional recovery in CX3CR1+/eGFP and Aldh1l1-EGFP mice over 6 weeks after lateral spinal cord hemisection. Second, we carried out a longitudinal follow-up of lesion evolution using in vivo T2-weighted magnetic resonance imaging (MRI). Finally, we performed in-depth analysis of the spinal cord tissue using ex vivo T2-weighted MRI as well as detailed histology. We demonstrate that CX3CR1+/eGFP mice have improved functional recovery and reduced anxiety after SCI compared with Aldh1l1-EGFP mice. We also found a strong correlation between in vivo MRI, ex vivo MRI, and histological analyses of the injured spinal cord in both strain of mice. All three modalities revealed no difference in lesion extension and volume between the two strains of mice. Importantly, histopathological analysis identified decreased gliosis and increased serotonergic axons in CX3CR1+/eGFP compared with Aldh1l1-EGFP mice following SCI. These results thus suggest that the strain-dependent improved functional recovery after SCI may be linked with reduced gliosis and increased serotonergic innervation.

Deletion of Neurotrophin Signaling through the Glucocorticoid Receptor Pathway Causes Tau Neuropathology.

Glucocorticoid resistance is a risk factor for Alzheimer's disease (AD). Molecular and cellular mechanisms of glucocorticoid resistance in the brain have remained unknown and are potential therapeutic targets. Phosphorylation of glucocorticoid receptors (GR) by brain-derived neurotrophic factor (BDNF) signaling integrates both pathways for remodeling synaptic structure and plasticity. The goal of this study is to test the role of the BDNF-dependent pathway on glucocorticoid signaling in a mouse model of glucocorticoid resistance. We report that deletion of GR phosphorylation at BDNF-responding sites and downstream signaling via the MAPK-phosphatase DUSP1 triggers tau phosphorylation and dendritic spine atrophy in mouse cortex. In human cortex, DUSP1 protein expression correlates with tau phosphorylation, synaptic defects and cognitive decline in subjects diagnosed with AD. These findings provide evidence for a causal role of BDNF-dependent GR signaling in tau neuropathology and indicate that DUSP1 is a potential target for therapeutic interventions.

Redistribution of PDGFRß cells and NG2DsRed pericytes at the cerebrovasculature after status epilepticus.

PURPOSE: The role of cerebrovascular dysfunction in seizure disorders is recognized. Blood-brain barrier (BBB) damage in epilepsy has been linked to endothelial and glial pathophysiological changes. Little is known about the involvement of pericytes, a cell type that contributes to BBB function. METHODS: NG2DsRed mice were used to visualize cerebrovascular pericytes. The pattern of vascular and parenchymal distributions of platelet-derived growth factor receptor beta (PDGFRß) cells was evaluated by immunohistochemistry. Status epilepticus was induced in NG2DsRed or C57BL/6J mice by intraperitoneal kainic acid (KA). Animals were perfused intracardially using FITC-Dextran or FITC-Albumin to visualize the cerebrovasculature. Colocalization was performed between NG2DsRed, PDGFRß and microglia IBA-1. Confocal 3D vessel reconstruction was used to visualize changes in cell morphology and position. PDGFRß expression was also evaluated in vitro using organotypic hippocampal cultures (OHC) treated with kainic acid to induce seizure-like activity. Co-localization of PDGFRß with the vascular marker RECA-1 and NG2 was performed. Finally, we assessed the expression of PDGFRß in brain specimens obtained from a cohort of patients affected by drug resistant epilepsy compared to available autoptic brain. RESULTS: In vivo, severe status epilepticus (SE) altered NG2DsRed vascular coverage. We found dishomogenous NG2DsRed perivascular ramifications after SE and compared to control. Concomitantly, PDGFRß(+) cells re-distributed towards the cerebrovasculature after severe SE. Cerebrovascular NG2DsRed partially colocalized with PDGFRß(+) while parenchymal PDGFRß(+) cells did not colocalize with IBA-1(+) microglia. Using in vitro OHC we found decreased NG2 vascular staining and increased PDGFRß(+) ramifications associated with RECA-1(+) microvessels after seizure-like activity. Cellular PDGFRß and NG2(+) colocalization was observed in the parenchyma. Finally, analysis of human TLE brains revealed perivascular and parenchymal PDGFRß(+) cell distributions resembling the murine in vivo and in vitro results. PDGFRß(+) cells at the cerebrovasculature were more frequent in TLE brain tissues as compared to the autoptic control. CONCLUSIONS: The rearrangement of PDGFRß(+) and vascular NG2DsRed cells after SE suggests a possible involvement of pericytes in the cerebrovascular modifications observed in epilepsy. The functional role of vascular-parenchymal PDGFRß(+) cell redistribution and the relevance of a pericyte response to SE remain to be fully elucidated.