Comparing Study Of The Effect Of Nanosized Silicon Dioxide And Microsized Silicon Dioxide On Fibrogenesis

ObjectiveIt is well known that silicosis is a kind of pneumoconiosis caused by the inhalation of silicon dioxide dust, which is characterized by lung fibrosis. We conducted an experimental study in rats by means of intratracheal instillation with nanosized silicon dioxide ( nanosized SiO2) and microsized silicon dioxide (microsized SiO2) to compare the different effect of nanosized SiO2 and mircosized SiO2 on fibrogenesis and on Interleukin - 4 (IL - 4) and Transforming growth factor - β1 (TGF - β1) in lungs of rats, which may provide experimental basis for discussing the potential toxicity and mechanism of nanosized SiO2 and assessing safety of nanomaterials.Methods1. Equal proportions of male and female Wistar rats all came from Center of experimental Animals of China Medical University. Animals were divided randomly into the following three experimental groups: (1) nanosized SiO2 group; (2) microsized SiO2 group; (3) saline control group ( control group). Rats were instilled intratracheally with 20mg of nanosized SiO2, 20mg of microsized SiO2 or saline.2. 7 ~ 8 rats of each group were sacrificed at 1 and 2 months after instillation respectively. The lungs of rats were analysed for the changes of lung/body coefficient and hydroxyproline content. Changes in pathology and fibrotic grade were observed by use of hematoxylin and eosin and Van Gieson dyeing. The expression of interleukin -4 (IL -4) and transforming growth factor - β1 (TGF -β1) was observed by use of immunohistochemical technique, and protein expression quantitatively analysed by image analysis.3. Statistical analysis methods we utilized were analysis of variance using SPSS10.0 software and then significant difference was examined by Q test. Differences were considered to be significant at P <0.05.Results1. Lung/body coefficient: At 1 month or 2 months after instillation, the lung/body coefficient of nanosized SiO2 group were significantly lower than those of microsized SiO2 group (P<0.05 or P<0.01) , but without significant differences from those of the control group.2. Hydroxyproline content: At 1 month or 2 months after instillation, the lung hydroxyproline contents of nanosized SiO2 group were significantly lower than those of microsized SiO2 group ( P <0. 05) , but without significant differences from those of the control group.3. Pathologic examination: The fibrotic degree of rats lung was much lighter in nanosized SiO2 group than that of microsized SiO2 group, and lighter 1/2 ~ 2 grade.4. Immunohistochemical results of IL -4 and TGF - β1: Quantity image a-nalysis showed that at 1 month or 2 months after instillation, integrated OD totals of IL -4 and TGF - β1 positive cell in nanosized SiO2 group were significantly lower than those of microsized SiO2 group (P <0. 01) , but without significant differences from those of the control group.Conclusion1. In our experiments, nanosized SiO2 could increase synthesization of lung collagen, however the effect was lower than that of microsized SiO2.2. In our experiments, nanosized SiO2 could induce fibrogenesis in lung, however the effect was milder than that of microsized SiO2.3. In our experiments, nanosized SiO2 could enhance expression of IL - 4...