Objective To assess relationship between lymphatic hyperplasia and fibrosis process in silicosis pathogenesis.

Methods Fifty-six Wistar rats were randomly divided into control and silicosis model group. The silicosis model group was further divided into subgroups as 1, 7, 14, 28, 42, and 56 d by animal neutralization time, eight rats in each group. Ink-silver nitrate staining was used to observe lymphatic hyperplasia. The level of mRNA transcription of vascular endothelial growth factor receptor-3(VEGFR-3) was determined by real-time quantitative PCR; the levels of collagen Ⅰ and hydroxyproline(HYP) were detected by fluorescence and immunohistochemistry staining.

Results Compared with the control group, collagen Ⅰ in the lung tissue rose up significantly from 1 d(P < 0.05) and HYP from 7 d(P < 0.01) after silica exposure. Pulmonary lymphatics hyperplasia was found in the silicotic rats after 7 d of silica exposure, and along with the extension of exposure time, it was increased first and then decreased. The mRNA expression of VEGRF-3 was increased significantly from 7d(P < 0.01) after silica exposure. The results of Pearson correlation analysis showed that the contents of collagen Ⅰ and HYP were positively correlated with the level of VEGRF-3 before 28 d of silica exposure(r=0.974 4, P=0.025 6;r=0.998 5, P=0.001 5) and negatively after 28 d(r=-0.975 1, P=0.024 9; r=-0.974 4, P=0.025 7).

Conclusion Lymphatic hyperplasia occurs in lung tissue during the process of silicosis, and the severity is associated with silicotic fibrosis process.