Purpose: Skeletal muscle dysfunction is common in patients with chronic obstructive pulmonary disease (COPD) and is associated with a poor prognosis. Abnormal muscle quantity of the lower limbs is a manifestation of skeletal muscle dysfunction in patients with COPD. Shear wave ultrasound elastography (SWE) is a novel and possible tool to evaluate qualitative muscle parameters. This study explores the feasibility of SWE to measure the stiffness of the rectus femoris and evaluates its value in predicting sarcopenia in patients with COPD.Methods: Ultrasound examination of the rectus femoris was performed to determine the mean elasticity index (SWE_mean), cross-sectional area (RF_csa), and thickness (RF_thick) using grayscale ultrasonography (US) and SWE in 53 patients with COPD and 23 age-matched non-COPD healthy controls. The serum levels of circulating biomarkers (GDF15, resistin, and TNF-α) were measured using ELISA. The definition of sarcopenia followed the guidelines from the Asian Working Group for Sarcopenia. Receiver operating characteristic (ROC) curve analysis of the SWE_mean, RF_thick, and RF_csa was used to evaluate their predictive ability for sarcopenia.Results: The intraobserver and interobserver repeatability of SWE performance was excellent (all correlation coefficients > 0.95; p < 0.05). The SWE_mean of the rectus femoris in patients with COPD (8.98 ± 3.12 kPa) was decreased compared with that in healthy controls (17.00 ± 5.14 kPa) and decreased with advanced global initiative for chronic obstructive lung disease (GOLD) stage. Furthermore, SWE_mean was found to be independent of sex, height, and body mass, and a lower SWE_mean in patients with COPD was positively associated with reduced pulmonary function, worse physical function, poor exercise tolerance, decreased muscle strength, and worse dyspnea index score. The correlation between physical function [five-repetition sit-to-stand test (5STST)], muscle function, and SWE_mean was higher than those of RF_thick and RF_csa. In addition, SWE_mean was negatively correlated with serum GDF15 levels (r = −0.472, p < 0.001), serum resistin levels (r = −0.291, p = 0.035), and serum TNF-α levels (r = −0.433, p = 0.001). Finally, the predictive power of SWE_mean [area under the curve (AUC): 0.863] in the diagnosis of sarcopenia was higher than that of RF_thick (AUC: 0.802) and RF_csa (AUC: 0.816).Conclusion: Compared with grayscale US, SWE was not affected by the patient’s height, weight, or BMI and better represented skeletal muscle function and physical function. Furthermore, SWE is a promising potential tool to predict sarcopenia in patients with COPD.

Chronic inflammatory airway diseases, characterized by airway inflammation and airway remodelling, are increasing as a cause of morbidity and mortality for all age groups and races across the world. The underlying molecular mechanisms involved in chronic inflammatory airway diseases have not been fully explored. MicroRNAs (miRNAs) and long noncoding RNAs (lncRNAs) have recently attracted much attention for their roles in the regulation of a variety of biological processes. A number of studies have confirmed that both lncRNAs and miRNAs can regulate the initiation and progression of chronic airway diseases by targeting mRNAs and regulating different cellular processes, such as proliferation, apoptosis, inflammation, migration, and epithelial–mesenchymal transition (EMT). Recently, accumulative evidence has shown that the novel regulatory mechanism underlying the interaction among lncRNAs, miRNAs and messenger RNAs (mRNAs) plays a critical role in the pathophysiological processes of chronic inflammatory airway diseases. In this review, we comprehensively summarized the regulatory roles of the lncRNA–miRNA–mRNA network in different cell types and their potential roles as biomarkers, indicators of comorbidities or therapeutic targets for chronic inflammatory airway diseases, particularly chronic obstructive pulmonary disease (COPD) and asthma.

Background: Pulmonary fibrosis is a respiratory disease caused by the proliferation of fibroblasts and accumulation of the extracellular matrix (ECM). It is known that the lung ECM is mainly composed of a three-dimensional fiber mesh filled with various high-molecular-weight proteins. However, the small-molecular-weight proteins in the lung ECM and their differences between normal and fibrotic lung ECM are largely unknown. Methods: Healthy adult male Sprague-Dawley rats (Rattus norvegicus) weighing about 150 to 200 g were randomly divided into three groups using random number table: A, B, and C and each group contained five rats. The rats in Group A were administered a single intragastric (i.g.) dose of 500 μL of saline as control, and those in Groups B and C were administered a single i.g. dose of paraquat (PQ) dissolved in 500 μL of saline (20 mg/kg). After 2 weeks, the lungs of rats in Group B were harvested for histological observation, preparation of de-cellularized lung scaffolds, and proteomic analysis for small-molecular-weight proteins, and similar procedures were performed on Group C and A after 4 weeks. The differentially expressed small-molecular-weight proteins (DESMPs) between different groups and the subcellular locations were analyzed. Results: Of the 1626 small-molecular-weight proteins identified, 1047 were quantifiable. There were 97 up-regulated and 45 down-regulated proteins in B vs. A, 274 up-regulated and 31 down-regulated proteins in C vs. A, and 237 up-regulated and 28 down-regulated proteins identified in C vs. B. Both the up-regulated and down-regulated proteins in the three comparisons were mainly distributed in single-organism processes and cellular processes within biological process, cell and organelle within cellular component, and binding within molecular function. Further, more up-regulated than down-regulated proteins were identified in most sub-cellular locations. The interactions of DESMPs identified in extracellular location in all comparisons showed that serum albumin (Alb) harbored the highest degree of node (25), followed by prolyl 4-hydroxylase beta polypeptide (12), integrin β1 (10), apolipoprotein A1 (9), and fibrinogen gamma chain (9). Conclusions: Numerous PQ-induced DESMPs were identified in de-cellularized lungs of rats by high throughput proteomics analysis. The DESMPs between the control and treatment groups showed diversity in molecular functions, biological processes, and pathways. In addition, the interactions of extracellular DESMPs suggested that the extracellular proteins Alb, Itgb1, Apoa1, P4hb, and Fgg in ECM could be potentially used as biomarker candidates for pulmonary fibrosis. These results provided useful information and new insights regarding pulmonary fibrosis.

Purpose: Sarcopenia, an age-related loss of skeletal muscle mass and function, is frequent in patients with chronic obstructive pulmonary disease (COPD) and is linked to a poor prognosis. The diagnosis of sarcopenia requires specific equipment and is inconvenient to introduce into clinical practice. Ultrasound is an innovative method to assess muscle quantity. The objective of this research was to evaluate the use of ultrasound for prospectively screening for sarcopenia in COPD patients. Patients and Methods: A total of 235 stable patients with COPD were included in this observational study and divided into development and validation sets. The Asian Working Group for Sarcopenia standards were used to define sarcopenia. The thickness (RF_thick) and cross-sectional area (RF_csa) of the rectus femoris were measured using ultrasound. Receiver operating characteristic curve analysis of RF_thick and RF_csa was used to predict sarcopenia. Nomogram models were constructed based on RF_thick, RF_csa, age and body mass index to identify sarcopenia. Results: Sarcopenia was present in 83 (35.32%) patients. Patients with sarcopenia had advanced age, decreased pulmonary function, decreased physical function and poor clinical outcomes. RF_thick and RF_csa showed good predictive ability for sarcopenia in the development and validation sets. The nomogram based on RF_thick and RF_csa could detect sarcopenia in COPD patients, and all had significant predictive performance in the development and validation sets. The calibration plot showed good agreement between the nomogram predictions and actual observations. Conclusion: The ultrasound measurement of the rectus femoris has potential for the clinical assessment of sarcopenia in patients with COPD.