Effects of discoidin domain receptor 1 on intestinal inflammation and fibrosis in experimental colitis mice

Abstract

Objective To explore the function of discoidin domain receptor 1 (DDR1) in intestinal inflammation and fibrosis in mice with chronic colitis. Methods A 20 bp gRNA sequence targeting exon4 of DDR1 gene was designed and synthesized, and subsequently microinjected into the fertilized eggs of C57BL/6 mice after being mixed with Cas9 mRNA in order to generate DDR1 mutant mice. The F4-generation homozygous mice (DDR1-/-) as well as wild-type C57BL/6 mice (WT) were used to induce chronic colitis model by being given 2.5% dextran sodium sulfate (DSS) in drinking water. Disease activity index (DAI), body weight, colon length and histopathological changes were compared between the 2 groups. The contents of pro-inflammatory cytokines in peripheral blood were detected by ELISA. The severity of intestinal fibrosis and the expression of fibrosis related proteins were observed by Masson staining and Western blotting, respectively. Results PCR results identified that DDR1-/- mutant mice were successfully generated using CRISPR/Cas9 technology. As compared with the WT group, the DDR1-/- mice exhibited slower body weight loss, lower DAI scores and intestinal histopathology scores, and mild colon shortening (5.81±0.11 vs 5.19±0.05 cm, P < 0.05) after DSS drinking. The serum levels of IL-1β, TNF-α and TGF-β were decreased (P < 0.01), with down-regulated expression of TGF-β, α-SMA and COL1A1 proteins in the colon tissues of DDR1-/- mice. Masson staining displayed that collagen volume fraction was higher in the WT group than the DDR1-/- mice (41.43±0.08 vs 21.37±0.07 cm, P < 0.01). Conclusion DDR1 is probably involved in the development of chronic colitis, and DDR1 deletion may mitigate the symptoms and disease progression of chronic intestinal inflammation and fibrosis.

Keywords

• discoidin domain receptor 1
• crispr/cas 9 technology
• gene knockout
• colitis
• intestinal fibrosis