Morphological and ultrastructural evaluation of the golden retriever muscular dystrophy trachea, lungs, and diaphragm muscle

Current Advances in 3D Dynamic Cell Culture Systems

The traditional two-dimensional (2D) cell culture methods have a long history of mimicking in vivo cell growth. However, these methods cannot fully represent physiological conditions, which lack two major indexes of the in vivo environment; one is a three-dimensional 3D cell environment, and the other is mechanical stimulation; therefore, they are incapable of replicating the essential cellular communications between cell to cell, cell to the extracellular matrix, and cellular responses to dynamic mechanical stimulation in a physiological condition of body movement and blood flow. To solve these problems and challenges, 3D cell carriers have been gradually developed to provide a 3D matrix-like structure for cell attachment, proliferation, differentiation, and communication in static and dynamic culture conditions. 3D cell carriers in dynamic culture systems could primarily provide different mechanical stimulations which further mimic the real in vivo microenvironment. In this review, the current advances in 3D dynamic cell culture approaches have been introduced, with their advantages and disadvantages being discussed in comparison to traditional 2D cell culture in static conditions.

Expiratory dysfunction in young dogs with golden retriever muscular dystrophy

Respiratory disease is a leading cause of morbidity in people with Duchenne muscular dystrophy and also occurs in the golden retriever muscular dystrophy (GRMD) model. We have previously shown that adult GRMD dogs have elevated expiratory flow as measured non-invasively during tidal breathing. This abnormality likely results from increased chest and diaphragmatic recoil associated with fibrosis and remodeling. Treatments must reverse pathologic effects on the diaphragm and other respiratory muscles to maximally reduce disease morbidity and mortality. Here, we extended our work in adults to younger GRMD dogs to define parameters that would be helpful in preclinical trials. Tidal breathing spirometry and respiratory inductance plethysmography were performed in GRMD dogs at approximately 3 and 6 months of age, corresponding to approximately 5-10 years in DMD, when clinical trials are often conducted. Expiratory flows were markedly elevated in GRMD versus normal dogs at 6 months. Values increased in GRMD dogs between 3 and 6 months, providing a 3-month window to assess treatment efficacy. These changes in breathing mechanics have not been previously identified at such an early age. Expiratory flow measured during tidal breathing of unsedated young GRMD dogs could be a valuable marker of respiratory mechanics during preclinical trials.

Morphological Characterization of Diaphragm in Common Squirrel Monkey (Saimiri sciureus)

The wall of the diaphragm can be affected by congenital or acquired alterations which allow the passage of viscera between the abdominal and chest cavities, allowing the formation of a diaphragmatic hernia. We characterized morphology and performed biometrics of the diaphragm in the common squirrel monkey Saimiri sciureus. After fixation, muscle fragments were collected and processed for optical microscopy. In this species the diaphragm muscle is attached to the lung by phrenopericardial ligament. It is also connected to the liver via the coronary and falciform ligaments. The muscle is composed of three segments in total: 1) sternal; 2) costal, and 3) a segment consisting of right and left diaphragmatic pillars. The anatomical structures analyzed were similar to those reported for other mammals. Histological analysis revealed stable, organized muscle fibers with alternation of light and dark streaks, indicating transverse striation.

Lung volume recruitment acutely increases respiratory system compliance in individuals with severe respiratory muscle weakness

The aim of the present study was to determine whether lung volume recruitment (LVR) acutely increases respiratory system compliance (C_rs) in individuals with severe respiratory muscle weakness (RMW).

Individuals with RMW resulting from neuromuscular disease or quadriplegia (n=12) and healthy controls (n=12) underwent pulmonary function testing and the measurement of C_rs at baseline, immediately after, 1 h after and 2 h after a single standardised session of LVR. The LVR session involved 10 consecutive supramaximal lung inflations with a manual resuscitation bag to the highest tolerable mouth pressure or a maximum of 50 cmH₂O. Each LVR inflation was followed by brief breath-hold and a maximal expiration to residual volume.

At baseline, individuals with RMW had lower C_rs than controls (37±5 cmH₂O versus 109±10 mL·cmH₂O⁻¹, p<0.001). Immediately after LVR, C_rs increased by 39.5±9.8% to 50±7 mL·cmH₂O⁻¹ in individuals with RMW (p<0.05), while no significant change occurred in controls (p=0.23). At 1 h and 2 h post-treatment, there were no within-group differences in C_rs compared to baseline (all p>0.05). LVR had no significant effect on measures of pulmonary function at any time point in either group (all p>0.05). During inflations, mean arterial pressure decreased significantly relative to baseline by 10.4±2.8 mmHg and 17.3±3.0 mmHg in individuals with RMW and controls, respectively (both p<0.05).

LVR acutely increases C_rs in individuals with RMW. However, the high airway pressures during inflations cause reductions in mean arterial pressure that should be considered when applying this technique.

Acute changes following lung volume recruitmenthttp://ow.ly/2dqE308g3oG

Anatomical and mesoscopic characterization of the dystrophic diaphragm: An in vivo nuclear magnetic resonance imaging study in the Golden retriever muscular dystrophy dog

Because respiratory failure remains a major issue in Duchenne Muscular Dystrophy patients, respiratory muscles are a key target of systemic therapies. In the Golden Retriever Muscular Dystrophy (GRMD) dogs, the disease shows strong clinical and histological similarities with the human pathology, making it a valuable model for preclinical therapeutic trials. We report here the first nuclear magnetic resonance (NMR) imaging anatomical study of the diaphragm in GRMD dogs and healthy controls. Both T1- and T2-weighted images of the diaphragm of seven healthy and thirteen GRMD dogs, from 3 to 36 months of age, were acquired on a 3 tesla NMR scanner. Abnormalities of texture and shape were revealed and consisted of increases in signal intensity on T2-weighted images and in signal heterogeneity on both T1- and T2-weighted images of the dystrophic diaphragm. These abnormalities were associated with a significant thickening of the muscle and we identified a clear 8-mm-threshold distinguishing clinically preserved GRMD dogs from those more severely affected. In this study, we demonstrated the feasibility of NMR imaging of the diaphragm and depicted several anatomical and mesoscopic anomalies in the dystrophic diaphragm. NMR imaging of the diaphragm shows a promise as an outcome measure in preclinical trials using GRMD dogs.

Respiratory impedance in patients with Duchenne muscular dystrophy

Impulse oscillometry (IOS) evaluates non-effort-dependent respiratory mechanics, and thus it may be useful to evaluate patients with Duchenne muscular dystrophy (DMD).

OBJECTIVES

We aimed (1) to describe the behavior of IOS parameters in patients with DMD, and compare it to those from a control group; (2) to determine whether resistances and reactances differ in relation to the severity of DMD; and (3) to compare IOS parameters with spirometry and maximal inspiratory (MIP) and expiratory (MEP) pressures.

METHODS

Children and adolescents (<20 years old) with biopsy-confirmed DMD and age-paired subjects were cross-sectionally evaluated. All results were transformed to z scores with respect to the healthy subjects (reference population).

RESULTS

Anthropometric characteristics did not differ between the 31 patients and 69 controls included in the study. Compared with controls, patients with DMD had higher IOS resistances and lower reactances. As expected, FEV₁ and FVC were lower in patients and always declined as age increased. By contrast, MIP and MEP were lower-than-normal in youngest patients, tended to improve around puberty initiation, and declined thereafter. In general, there was a poor correlation between IOS parameters and spirometric variables or respiratory pressures, excepting for X20 Hz, which had an inverse correlation with FEV₁ . Interestingly, IOS resistances were higher in patients with less disability (lower Vignos score; better FVC), but tended to be normalized in advanced stages of the disease.

CONCLUSION

This study showed that IOS is feasible in children and adolescents with DMD and yields information about respiratory function not achievable with the usual forced techniques. Pediatr Pulmonol. 2016;51:1072-1079. © 2016 Wiley Periodicals, Inc.

Development of the cardiorespiratory system in dogs from days 16 to 46 of pregnancy

Dogs have been studied for several reasons, such as the genetic improvement, their use as experimental models, in zoonotic research, cell therapy and as a model for human diseases. However, many features relating to the embryonic development of dogs remain unknown because of the absence of embryological studies. Considering the importance of the cardiorespiratory system in the development of embryos, the aim of this study was to investigate the development of the main cardiorespiratory organs of dog embryos and foetuses with estimated gestational ages from 16 to 46 days using macro- and microscopic descriptions. On day 16 of development, the neural tube and crest were formed, the anterior and posterior neuropore closure had begun and the somites had developed. Between days 22 and 27 of gestation, the lung buds and the initial formation of the primary bronchi and heart chambers were observed. The heart chambers exhibited the endo-, myo- and epicardial layers but did not have obvious differences in thickness among each other. Between days 41 and 46 of gestation, the nasal conchae and septa and trachea were formed, which exhibited characteristic epithelia. The lung formation and lobation were complete. The heart and major vessels exhibited mature histological architecture when their anatomical development was complete. The results of this study contribute to a more accurate definition of the embryonic and foetal developmental stages in dogs.

Concurrent Label-Free Mass Spectrometric Analysis of Dystrophin Isoform Dp427 and the Myofibrosis Marker Collagen in Crude Extracts from mdx-4cv Skeletal Muscles

The full-length dystrophin protein isoform of 427 kDa (Dp427), the absence of which represents the principal abnormality in X-linked muscular dystrophy, is difficult to identify and characterize by routine proteomic screening approaches of crude tissue extracts. This is probably related to its large molecular size, its close association with the sarcolemmal membrane, and its existence within a heterogeneous glycoprotein complex. Here, we used a careful extraction procedure to isolate the total protein repertoire from normal versus dystrophic mdx-4cv skeletal muscles, in conjunction with label-free mass spectrometry, and successfully identified Dp427 by proteomic means. In contrast to a considerable number of previous comparative studies of the total skeletal muscle proteome, using whole tissue proteomics we show here for the first time that the reduced expression of this membrane cytoskeletal protein is the most significant alteration in dystrophinopathy. This agrees with the pathobiochemical concept that the almost complete absence of dystrophin is the main defect in Duchenne muscular dystrophy and that the mdx-4cv mouse model of dystrophinopathy exhibits only very few revertant fibers. Significant increases in collagens and associated fibrotic marker proteins, such as fibronectin, biglycan, asporin, decorin, prolargin, mimecan, and lumican were identified in dystrophin-deficient muscles. The up-regulation of collagen in mdx-4cv muscles was confirmed by immunofluorescence microscopy and immunoblotting. Thus, this is the first mass spectrometric study of crude tissue extracts that puts the proteomic identification of dystrophin in its proper pathophysiological context.

Pathoproteomic profiling of the skeletal muscle matrisome in dystrophinopathy associated myofibrosis

The gradual accumulation of collagen and associated proteins of the extracellular matrix is a crucial myopathological parameter of many neuromuscular disorders. Progressive tissue damage and fibrosis play a key pathobiochemical role in the dysregulation of contractile functions and often correlates with poor motor outcome in muscular dystrophies. Following a brief introduction into the role of the extracellular matrix in skeletal muscles, we review here the proteomic profiling of myofibrosis and its intrinsic role in X-linked muscular dystrophy. Although Duchenne muscular dystrophy is primarily a disease of the membrane cytoskeleton, one of its most striking histopathological features is a hyperactive connective tissue and tissue scarring. We outline the identification of novel factors involved in the modulation of the extracellular matrix in muscular dystrophy, such as matricellular proteins. The establishment of novel proteomic markers will be helpful in improving the diagnosis, prognosis, and therapy monitoring in relation to fibrotic substitution of contractile tissue. In the future, the prevention of fibrosis will be crucial for providing optimum conditions to apply novel pharmacological treatments, as well as establish cell-based approaches or gene therapeutic interventions. The elimination of secondary abnormalities in the matrisome promises to reduce tissue scarring and the loss of skeletal muscle elasticity.