Molecular mechanism of elastin and its regulatory factors on the formation and reversal of liver fibrosis in a mouse model of liver fibrosis

Objective To investigate the expression of elastin in a mouse model of carbon tetrachloride( CCl4)-induced liver fibrosis and the molecular mechanism of elastin deposition. Methods A mouse model of CCl4-induced liver fibrosis was established. Western blot,soluble protein,and Victoria blue staining were used to measure the change in elastin in the early stage of liver fibrosis( after 4 weeks of CCl4 injection) and the progressive stage of liver fibrosis( after 8 weeks of CCl4 injection). The mice treated with olive oil were enrolled as healthy control group. A model of spontaneous reversal of fibrosis was established; liquid chromatography-tandem mass spectrometry( LC-MS/MS) was used to measure the change in serum proteomics at different time points of reversal( at weeks 0,4,8,and 12 of reversal) and identify the potential molecules associated with elastin deposition,and qPCR was used for validation. A one-way analysis of variance was used for comparison of continuous data between multiple groups,and the least signficant difference Tukey test was used for further comparison between two groups. Results The relative expression of elastin was 0. 82 ± 0. 05 in the early fibrosis group and 1. 59 ± 0. 58 in the progressive fibrosis group,and compared with the healthy control group,the progressive fibrosis group had a significant increase in the expression of elastin( 1. 59 ± 0. 58 vs 1. 00 ± 0. 11,P < 0. 05). The measurement of insoluble elastin showed that compared with the healthy control group( 207. 9 ± 34. 7 μg/10 mg),the early fibrosis group had no significant change in insoluble elastin( 213. 5 ± 26. 7 μg/10 mg,P >0. 05),and the progressive fibrosis group had a significant increase in insoluble elastin( 352. 0 ± 57. 0 μg/10 mg,P < 0. 05). Elastin staining of liver tissue showed that compared with the healthy control group,the early fibrosis group and the progressive fibrosis group had a significant increase in the area of liver tissue with positive elastin expression( 2. 08 ± 0. 16/4. 39 ± 0. 51 vs 1. 03 ± 0. 14,both P < 0. 05). The mRNA expression of elastase 12 was measured,and the results showed that compared with the healthy control group,the early fibrosis group and the progressive fibrosis group had a significant increase in the mRNA expression of elastase 12( 15. 50 ± 2. 90/22. 70 ± 4. 10 vs 1. 30 ±0. 10,both P < 0. 05),suggesting that the mRNA expression of elastase 12 increased with the progression of liver fibrosis. During the reversal of liver fibrosis,45 proteins associated with the progression and reversal of liver fibrosis were isolated and identified by LC-MS/MS,among which lysyl oxidase-like protein-1( LOXL-1) and fibulin-1( FBLN-1) were associated with elastin deposition. Validation of LOXL-1 and FBLN-1 by q PCR showed that the mRNA expression of LOXL-1 and FBLN-1 reached the peak after 8 weeks of CCl4 injection( week 0 of reversal) and then gradually decreased over the time of reversal. Conclusion Elastin deposition is one of the important features in a mouse model of progressive liver fibrosis,and elastin deposition mediated by LOXL-1 and FBLN-1 may become a treatment target for liver fibrosis,liver cirrhosis,and end-stage liver disease.