ObjectiveTo investigate the role of Krüppel-like factor 4 (KLF4) mediated monocyte/macrophage subtype switch in the pathological progression of pulmonary fibrosis.MethodsThirty-six patients with interstitial pneumonia were recruited from Characteristic Medical Center of the Chinese People's Armed Police Force between May 2015 and January 2017. Peripheral venous blood and bronchoalveolar lavage fluid were collected in the morning. Pulmonary function and arterial blood gas were tested after admission. Flow cytometry was used to test monocyte subtypes of peripheral blood and macrophage subtypes of bronchoalveolar lavage fluid. KLF4 of peripheral blood was detected by enzyme linked immunosorbent assay. Thirty normal subjects were selected as control group of peripheral blood mononuclear cell subtypes and KLF4 (control group A), and 10 patients without pulmonary fibrosis who needed bronchoscopy were selected as control group of macrophage subtypes in alveolar lavage fluid (control group B). The relationship between the expression of KLF4 and the differentiation of monocytes and macrophages were observed. Furthermore, the relationship between the differentiation of monocytes subtypes, macrophages subtypes and lung function were observed.ResultsMonocyte of CD14++CD16– subtype in pulmonary fibrosis group was significantly lower than that in control group A (P<0.05). Monocyte of CD14++CD16+ subtype in pulmonary fibrosis group was significantly higher than that in control group A (P<0.05). No significant difference was found between the two groups regarding CD14+CD16++. No correlation was found between three subtypes of monocyte and DLCO of patients and between three subtypes of monocyte and PaO2 of patients. M1 macrophage in pulmonary fibrosis group was significantly lower than that in control group B (P<0.05). M2 macrophage in pulmonary fibrosis group was significantly higher than that in control group B (P<0.05). Negative correlation was found between the ratio of M2 subtypes and DLCO of patients and between the ratio of M2 subtypes and PaO2 of patients (P<0.05). KLF4 protein of blood in pulmonary fibrosis group was significantly higher than that in control group A (P<0.05). Positive correlation was found between the ratio of M2 subtypes and KLF4 protein (P<0.05).ConclusionsCD16+ monocyte plays a role in the occurrence and development of pulmonary fibrosis, but no evidence is found there is a direct correlation between monocyte subtypes of peripheral blood and fibrosis degree of lung tissue. M2 macrophage subtype plays an important role in the development of interstitial pneumonia. The number of M2 macrophages is positively correlated with the severity of pulmonary fibrosis. Monocyte/macrophage subtype differentiation by KLF4 may play a role in the pathological progression of pulmonary fibrosis.
Objective To investigate the expression and significance of Krüppel-like factor 4 ( KLF4) in the lung tissues of mice with bleomycin-induced pulmonary fibrosis.Methods C57BL/6 mice were randomly divided into a control group and a BLM group. The mice in the BLM group were given a single intratracheal injection of bleomycin ( 2.5 mg/kg) , while those in the control group were injected with isodose physiological saline. The mice were sacrificed at the 12h and on the day 1, 2, 3, 7, 14 and 28, then HE stain and Masson’s trichrome stain were used to detect the architecture of alveolar and the deposition of cellularity and collagen. Real time-polymerase chain reaction ( RT-PCR ) and immunohistochemical technology were performed to investigate the expression of KLF4. Results In the bleomycin-induced pulmonary fibrosis, acute inflammation was observed on the day 1, 2 and 3, the inflammation was exacerbated and the collagen deposition began to be observed on the day 7, the architecture of alveolar was destroyed and the collagen deposition was more obvious on the day 14, while the alveolar structure was nearly recovered to normal, and the inflammation and collagen deposition were attenuated on the day 28. The expression of KLF4 mRNA increased from the day 1, then decreased, arrived at the minimumon the day 3, and then gradually increased until the day 28. The trend of KLF4 protein expression showed roughly the same as the KLF4 mRNA level, which started to increase on the day 1, then decreased, arrived at the minimum on the day 3,then gradually increased until the day 14 and then decreased again. Conclusion The expressions of KLF4 mRNA and protein are dynamically changed in the process of experimental pulmonary fibrosis, suggesting KLF4 may contribute to the pathogenesis of pulmonary fibrosis.