Despite advances in the pathophysiology of Chronic Obstructive Pulmonary Disease (COPD), there is a distinct lack of biochemical markers to aid clinical management. Microvesicles (MVs) have been implicated in the pathophysiology of inflammatory diseases including COPD but their association to COPD disease severity remains unknown. We analysed different MV populations in plasma and bronchoalveolar lavage fluid (BALF) taken from sixty-two patients with mild to very severe COPD (51% male; mean age: 65.9 years). These patients underwent comprehensive clinical evaluation (symptom scores, lung function, exercise testing) and the capacity of MVs to be clinical markers of disease severity was assessed. We successfully identified various MV subtype populations within BALF (leukocyte, PMN (polymorphonuclear leukocyte i.e. neutrophil), monocyte, epithelial and platelet MVs) and plasma (leukocyte, PMN, monocyte and endothelial MVs), and compared each MV population to disease severity. BALF neutrophil MVs were the only population to significantly correlate with the clinical evaluation scores including FEV1, mMRC dyspnoea score, 6-minute walk test, hyperinflation and gas transfer. BALF neutrophil MVs, but not neutrophil cell numbers, also strongly correlated with BODE index. We have undertaken, for the first time, a comprehensive evaluation of MV profiles within BALF/plasma of COPD patients. We demonstrate that BALF levels of neutrophil-derived MVs are unique in correlating with a number of key functional and clinically-relevant disease severity indices. Our results show the potential of BALF neutrophil MVs for a COPD biomarker that tightly links a key pathophysiological mechanism of COPD (intra-alveolar neutrophil activation) with clinical severity/outcome.

BackgroundDespite advances in understanding the pathophysiology of acute respiratory distress syndrome, effective pharmacological interventions have proven elusive. We believe this is a consequence of existing preclinical models being designed primarily to explore biological pathways, rather than predict treatment effects. Here, we describe a mouse model in which both therapeutic intervention and ventilation were superimposed onto existing injury and explored the impact of β-agonist treatment, which is effective in simple models but not clinically.MethodsMice had lung injury induced by intranasal lipopolysaccharide (LPS), which peaked at 48 hours post-LPS based on clinically relevant parameters including hypoxaemia and impaired mechanics. At this peak of injury, mice were treated intratracheally with either terbutaline or tumour necrosis factor (TNF) receptor 1-targeting domain antibody, and ventilated with moderate tidal volume (20 mL/kg) to induce secondary ventilator-induced lung injury (VILI).ResultsVentilation of LPS-injured mice at 20 mL/kg exacerbated injury compared with low tidal volume (8 mL/kg). While terbutaline attenuated VILI within non-LPS-treated animals, it was ineffective to reduce VILI in pre-injured mice, mimicking its lack of clinical efficacy. In contrast, anti-TNF receptor 1 antibody attenuated secondary VILI within pre-injured lungs, indicating that the model was treatable.ConclusionsWe propose adoption of a practical framework like that described here to reduce the number of ultimately ineffective drugs reaching clinical trials. Novel targets should be evaluated alongside interventions which have been previously tested clinically, using models that recapitulate the (lack of) clinical efficacy. Within such a framework, outperforming a failed pharmacologic should be a prerequisite for drugs entering trials.

Scientific Knowledge on the SubjectCyclophilin A (CypA) is a ubiquitously expressed cytosolic protein most known for its role in intracellular protein folding. The gene responsible for CypA expression has very recently been implicated in susceptibility to COVID-19 infection. A secreted form, extracellular CypA (eCypA) has been identified as having involvement in diseases such as rheumatoid arthritis and coronary artery disease, but little is known regarding any role within the lungs. What This Study Adds to the FieldWe have identified a novel role for secreted eCypA in the pathogenesis of ventilatorinduced lung injury (VILI). eCypA is secreted from epithelial cells during VILI in mice and promotes alveolar macrophage activation, such that in vivo inhibition attenuates development of injury. Furthermore eCypA levels are increased in bronchoalveolar AJRCCM Articles in Press.

Author contribution: YY.T. and K.P.O. conceived and designed the work, performed experiments, analyzed the data, and prepared the manuscript. DM.T. conceived and designed the work, performed experiments, and analyzed the data A.PS, M.W.K, and F.B performed experiments. M.T. conceived and designed the work, and prepared the manuscript. All authors approved the final version.