Objective: To explore the correlation between expression level of miRNAs and pulmonary fibrosis on the basis of comparison the differential expression of miRNAs in rat pulmonary fibrosis induced by nano SiO₂ and micron SiO₂. Methods: Thirty-six healthy male SD rats weighting 180-220 g were randomly divided into 3 groups. They were instilled intratracheally with 1 ml suspension of saline, 25 mg/ml nanosized SiO₂ and microsized SiO₂ particles and sacrificed at 60 d and 90 d postexposure from each group with six rats. The change of pathological morphology and ultrastructure of lung were observed by optical and transmission electron microscopy. The differentially expressed microRNAs in lung tissue of the rats after instilled intrachcally nanosized SiO₂ and microsized SiO₂ particles at 60 d and 90 d were determined by Illumina HiSeq 2 000 sequencing technique. Target prediction for miRNAs was conducted by databases of Target-scan. Function-significant enrichment analysis and signal pathway analysis for predicted target genes were respectively conducted by the GO and the KEGG, then target genes related to pulmonary fibrosis were screened out. Results: Light microscope examination showed that wide bronchi, vessels, interlobular septa and slight fibrous connective tissue proliferation at 60 d and 90 d postexposure in 25 mg/ml nanosized SiO₂ group. A few fused nodules at 30 d postexposure, a lot of fused nodules at 60 d postexposure, fibrous cell nodules and compensatory emphysema around alveolar at 90 d postexposure in 25 mg/mL microsized SiO₂ group were observed. Electron microscopy demonstrated swelling and vacuolar degeneration of osmiophilic lamellar bodies in type Ⅱ alveolar epithelial cells, collagen fiber and elastic fiber hyperplasia in pulmonary interstitial at 60 d, 90 d postexposure in 25 mg/ml nanosized SiO₂ group. Increased and vacuoloid changed osmiophilic lamellar bodies in type Ⅱ alveolar epithelial cells, collagen fiber and elastic fiber hyperplasia in the interstitial at 60 d, 90 d postexposure in 25 mg/ml microsized SiO₂ group were observed. Comparing to saline control group, the number of miRNA up-regulated expression was 50, 70, and down-regulated expression was 22 and 24 at 60 d, 90 d postexposure in 25 mg/ml nanosized SiO₂ group respectively. There were 91,70 miRNAs up-regulated expression and 34,78 miRNAs down-regulated expression at 60 d, 90 d postexposure in 25 mg/ml microscale SiO₂ group. The common miRNA of differential up-regulated expression are miRNA-18a and miRNA-702-3p, down-regulated expression are miRNA-541, miRNA-127 and miRNA-379 both in nanosized SiO₂ and microscale SiO₂ group. The target genes related to pulmonary fibrosis were CTGF, IGF, BMP7, FGF7, TGF-β RIII, IGF1R and TGF-β1 respectively. Their biologic functions are to regulate signal pathway of TGF-β, MAPK and Wnt, and activation of fibroblast. Conclusion These findings suggested that same dose of nanosized SiO₂ particles could cause mainly characterized by pulmonary interstitial fibrosis differing from silicotic nodule caused by microsized SiO₂. miRNA-18a, miRNA-702-3p, miRNA-541, miRNA-127 and miRNA-379 may play a role in the process of pulmonary fibrosis in nanosized SiO₂ and microscale SiO₂ by regulating its target genes.

OBJECTIVETo Investigate the biological effects of miR-144 in rats' pulmanory injury induced by nanosized SiO₂preliminarily.

METHOD150 healthy SD rats were divided into five groups randomly: the control group, the nanosized SiO₂groups of 6.25, 12.5, 25.0 mg/ml, and the microsized SiO₂group of 25.0 mg/ml, 30 rats each group. Six rats were sacrificed for their pathological change on the 7th, 15th, 30th, 60th and 90th day after exposure. The expression levels of mature miR-144 in lung tissue of the rats after instilled intracheally nanosized SiO₂at 90d was detected by Quantitative Reverse Transcription PCR. Target prediction for miR-144 was conducted by databases of Target-scan, microRNA.org and miRDB. Function-significant enrichment analysis and signal pathway analysis for predicted target genes were respectively conducted by the Gene Ontology and the Kyoto Encyclopedia of Genes and Genomes, then target genes related to pulmonary fibrosis were screened out.

RESULTSThe expression of miR-144 was up-regulated in lung tissue of rats exposed to nanosized SiO₂. The result was consistent with the results of high-throughput sequencing Hiseq 2000. The target genes of miR-144 related to fibrosis or signal pathway involved in fibrosis were screened out.They are SMAD4, SMAD5, ADAMTS3, ADAMTS15 and ADAMTS19.

CONCLUSIONMiR-144 probably participate in the regulation of fibrosis, which may play an important role in pulmonary injury induced by nanosized SiO₂.

Animals ; Lung ; pathology ; Lung Injury ; chemically induced ; metabolism ; pathology ; MicroRNAs ; metabolism ; Nanoparticles ; adverse effects ; Pulmonary Fibrosis ; metabolism ; pathology ; Rats ; Rats, Sprague-Dawley ; Signal Transduction ; Silicon Dioxide ; toxicity