The Role of Fibrocyte in the Pathogenesis of Silicosis.

Exposure to free silica induces silicosis and myofibroblasts are regarded as primary effector cells. Fibrocytes can differentiate into myofibroblast. Therefore, the present study was designed to investigate whether fibrocytes participate in silicosis. The rat model of silicosis was established. Hematoxylin-eosin stainings and Masson stainings were used to evaluate the histopathology and collagen deposition. Flow cytometry and immunofluorescence were performed to detect the number of fibrocytes and their contribution to myofibroblasts. Results showed that fibrocytes participate in silicosis. Trend analysis of different sources of myofibroblasts during silicosis indicated that fibrocytes and lung type II epithelial cell-derived myofibroblasts play an important role in the early stage of silicosis, while resident lung fibroblast-derived myofibroblasts play a predominant role during the fibrosis formative period.

Crystalline Silica Promotes Rat Fibrocyte Differentiation in Vitro, and Fibrocytes Participate in Silicosis in Vivo.

OBJECTIVE: The aim of this study was to investigate the effects of SiO2 on fibrocytes and whether fibrocytes participate in silicosis in vivo. METHODS: A macrophagocyte (AM)/fibrocyte coculture system was established, and AMs were treated with 100 µg/mL SiO2. Flow cytometry was used to detect the number of fibrocytes. Real-time PCR was performed to measure the expression of collagen I, collagen III, and α-SMA mRNA. The levels of collagen I, collagen III, and TGF-ß1 protein were determined by ELISA. Immunohistochemical staining was performed to measure α-SMA protein expression. A rat silicosis model was induced by intratracheal instillation of SiO2. Lung histopathological evaluation was conducted using HE and Masson's trichrome staining after 1 and 9 weeks. The number of fibrocytes in peripheral blood or lung tissue of rat was detected by flow cytometry. Double-color immunofluorescence was applied to identify fibrocytes in the lung tissue. RESULTS: Peripheral blood monocytes were found to differentiate into fibrocytes in vitro in a time-dependent manner, and exposure to crystalline silica might potentiate fibrocyte differentiation. In addition, fibrocytes were able to migrate from peripheral blood to the lung tissue, and the number of fibrocytes was increased after SiO2 exposure. CONCLUSION: Silica exposure potentiates fibrocyte differentiation, and fibrocytes may participate in silicosis in vivo.

[The expression of vascular endothelial growth factor antibody in serum of coal workers with pneumoconiosis].

OBJECTIVE: To determine the role of serum VEGF-Ab in pneumoconiosis of coal workers. METHODS: Four groups of participants were recruited for this study, including 230 with early stage (less serious than stage one) changes in relation to pneumoconiosis, 328 with confirmed coal worker pneumoconiosis, 309 workers exposed to coal dust, and 393 healthy people. All participants completed a questionnaire, and have their peripheral venous blood sample taken. Serum VEGF-Ab was detected by ELISA. RESULTS: Compared with healthy controls and those with early stage changes, the participants with pneumoconiosis and those exposed to coal dust had higher levels of serum VEGF-Ab (P < 0.05). The level of serum VEGF-Ab increased with the progression of stages of pneumoconiosis but without statistical significance (P > 0.05). In those with early stage pneumoconiosis, higher levels of serum VEGF-Ab were found in their 20 yr. - and 40 yr. - compared with those in their 60 yr. - (P < 0.05). By contrast, in those with confirmed pneumoconiosis and the healthy controls, lower levels of serum VEGF-Ab were found in their 20 yr. - and 40 yr. - compared with those in their 60 yr. - (P < 0.05). In those with early stage or first-stage pneumoconiosis, longer than 25 years work experience was associated with higher levels of serum VEGF-Ahb (P < 0.05). In those with confirmed pneumoconiosis, coal mining workers had a higher level of serum VEGF-Ab than their colleagues involving in assistance tasks (P < 0.05). In those exposed to coal dust, tunnelling workers had a higher level of serum VEGF-Ab than their coal mining colleagues (P < 0.05). CONCLUSION: Serum VEGF-Ab is associated with the occurrence and development of coal worker pneumoconiosis. The level of serum VEGF-Ab increases with age and length of exposure to dust.