BackgroundAlthough aberrant proliferation and activation of lung fibroblasts are implicated in the initiation and progression of idiopathic pulmonary fibrosis (IPF), the underlying mechanisms are not well characterized. Numerous microRNAs (miRNAs) have been implicated in this process; however, miRNAs derived from exosomes and their relevance to fibroblast-to-myofibroblast differentiation have not been fully elucidated. In this study, we aimed to identify exosome-derived miRNAs relevant to fibrosis development. MethodsWe profiled exosome-derived miRNAs expression in sera of C57BL/6 mice exhibiting bleomycin-induced pulmonary fibrosis by miRNA array analysis. After validating a selected miRNA by quantitative reverse-transcription polymerase chain reaction, its effect on fibroblastto-myofibroblast differentiation was investigated using human lung fibroblasts. Furthermore, we determined the role of the selected miRNA in an in-vivo pulmonary fibrosis model. ResultsMiRNA array analysis revealed that miR-22 expression was increased by up to 2 fold on day 7 after bleomycin treatment compared with that in vehicle-treated mice. In vitro, miR-22 transfection suppressed TGF-β1-induced α-SMA expression. This was mediated via the 3 inhibition of the ERK1/2 pathway. Baseline α-SMA expression was increased upon miR-22 inhibitor transfection. Furthermore, miR-22 negatively regulated connective tissue growth factor expression in the presence of TGF-β1. In vivo, administration of a miR-22 mimic on day 10 after bleomycin challenge ameliorated pulmonary fibrosis lesions accompanied by decreased α-SMA expression in the model mice. ConclusionsExosomal miR-22 modulates fibroblast-to-myofibroblast differentiation. The present study warrants further investigations to shed light on miR-22 as a novel therapeutic target for patients with IPF.

BackgroundIdiopathic pulmonary fibrosis (IPF) is a progressive disease with high mortality, and the pathogenesis of the disease is still incompletely understood. Although lymphocytes, especially CD4+CD25+FoxP3+ regulatory T cells (Tregs), have been implicated in the development of IPF, contradictory results have been reported regarding the contribution of Tregs to fibrosis both in animals and humans. The aim of this study was to investigate whether a specific T cell subset has therapeutic potential in inhibiting bleomycin (BLM)-induced murine pulmonary fibrosis.MethodsC57BL/6 mice received BLM (100 mg/kg body weight) with osmotic pumps (day 0), and pulmonary fibrosis was induced. Then, splenocytes or Tregs were adoptively transferred via the tail vein. The lungs were removed and subjected to histological and biochemical examinations to study the effects of these cells on pulmonary fibrosis, and blood samples were collected by cardiac punctures to measure relevant cytokines by enzyme-linked immunosorbent assay. Tregs isolated from an interleukin (IL)-10 knock-out mice were used to assess the effect of this mediator. To determine the roles of the spleen in this model, spleen vessels were carefully cauterized and the spleen was removed either on day 0 or 14 after BLM challenge.ResultsSplenocytes significantly ameliorated BLM-induced pulmonary fibrosis when they were administered on day 14. This effect was abrogated by depleting Tregs with an anti-CD25 monoclonal antibody. Adoptive transfer of Tregs on day 14 after a BLM challenge significantly attenuated pulmonary fibrosis, and this was accompanied by decreased production of fibroblast growth factor (FGF) 9-positive cells bearing the morphology of alveolar epithelial cells. In addition, BLM-induced plasma IL-10 expression reverted to basal levels after adoptive transfer of Tregs. Moreover, BLM-induced fibrocyte chemoattractant chemokine (CC motif) ligand-2 production was significantly ameliorated by Treg adoptive transfer in lung homogenates, accompanied by reduced accumulation of bone-marrow derived fibrocytes. Genetic ablation of IL-10 abrogated the ameliorating effect of Tregs on pulmonary fibrosis. Finally, splenectomy on day 0 after a BLM challenge significantly ameliorated lung fibrosis, whereas splenectomy on day 14 had no effect.ConclusionsThese findings warrant further investigations to develop a cell-based therapy using Tregs for treating IPF.

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Objectives Acute exacerbation of idiopathic pulmonary fibrosis (IPF-AE) has been recognized as a fatal pulmonary disorder, but the exact prognostic factors are unknown. The aim of the present study was to analyze the clinical characteristics of patients with IPF-AE and identify the prognostic factors. Methods The medical records of 59 cases of IPF-AE were retrospectively reviewed. Clinical data, laboratory data, radiographic findings, treatment, and time from the onset of symptoms to the initiation of corticosteroid pulse therapy, i.e. symptom duration, and outcome were analyzed. Results The IPF Stage, Gender-Age-Physiology (GAP) Index, symptom duration, and the high-resolution computed tomography (HRCT) score were significantly related to the prognosis in the univariate analysis. In the multivariate analysis, the symptom duration remained a significant prognostic factor (hazard ratio of 1-day increase, 1.11; 95% confidence interval, 1.01-1.15; p=0.0427). The area under the receiver operating characteristics curve of symptom duration was statistically significant for survivors versus non-survivors (area under the curve, 0.73; p=0.012). The survival period was significantly shorter in the late-treatment groups (≥5 days; n=30) than in the early-treatment groups (<5 days; n=29; log-rank test; p<0.0001). Conclusion The time interval between the onset of symptoms and the initiation of corticosteroid pulse therapy may be an independent prognostic factor in patients with IPF-AE.

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