Inhibitory effect of circulating fibrocytes on injury repair in acute lung injury/acute respiratory distress syndrome mice model.

The study was aimed to explore the functions of circulating fibrocytes (CFs) on injury repair in acute lung injury/acute respiratory distress syndrome (ALI/ARDS) mice model and its clinical value as a biomarker for ALI/ARDS. ALI/ARDS mice model was established by intratracheal instillation of lipopolysaccharide (LPS). Mononuclear cells were isolated from peripheral blood of ALI/ARDS model and flow cytometry was used to measure CFs defined as cells positive for CD45 and collagen-1. Histological changes of lung tissues were evaluated by H&E staining and Masson's trichrome staining. The correlations of CFs counts with damnification of lung tissue and the severity of pulmonary fibrosis were evaluated by Pearson correlation analyses. Western blot was used to detect the protein expression of collagen-1. ELISA was applied to determine cytokine CXCL12 concentration. Clinical relevance between CFs and ALI/ARDS was investigated. The greater number of CFs in the ALI/ARDS group implied higher degree of lung injury and more severe pulmonary fibrosis. The protein expression of collagen-1 and concentration of cytokine CXCL12 in ALI/ARDS group were higher than that in control group. Clinical and prognostic analysis revealed the higher injury degree and death rates in ALI/ARDS group than those in control group, and identified a greater severity and mortality for patients with ARDS than those with ALI. ROC curve analysis indicated the counts of CFs greater than 5.85% can predict death rates with AUC = 0.928. CFs had an inhibitory effect on injury repair in ALI/ARDS mice model. This might be unfavorable as a clinical marker for progression of ALI/ARDS.