Discussion
AE is a zoonotic parasitic disease that seriously endangers human health20. The study of E. multilocularis has always lacked stable experimental animal models. The traditional infection models are secondary infection mouse models constructed by intraperitoneal injection and liver puncture 21, 22. Although it can reflect that the body is infected by E. multilocularis to a certain extent, the infection mode is far from the natural infection. During natural infection, humans become infected when they inadvertently ingest soil, water, or food contaminated with Echinococcus eggs excreted in dog feces. The eggs germinate in the small intestine to form hexacarcinoma, which can adhere and penetrate the intestinal wall, enter blood vessels, and reach and parasitize in the liver tissue along with the blood circulation23, 24. In recent years, Abuduaini Abulizi and his colleagues established a novel mouse model of infection by injecting E. multilocularis through the hepatic portal vein25. This model can more accurately simulate the natural infection process.
In this study, the infection mouse model was constructed by injectingE. multiloculari s through the hepatic portal vein. After 3 months of infection, B-ultrasound results found that the liver of the mice in the infection group had obvious lesions and E. multiloculari s antigen-specific antibodies in serum significantly increased, which indicates that the infection mouse model was successfully constructed. The results of HE and Masson staining showed that the infection ofE. multiloculari s could cause liver damage, and a large number of collagen fibers were formed. In addition, the level of ALT and AST in serum were increased. These results suggested that E. multiloculari s infection can cause liver tissue damage, however, the mechanism of liver injury is still unclear. Thus, the present study explored the mechanism of liver injury from the perspective of miRNA by using RNA seq technique. Total 71 differential expression miRNAs were obtained and a total of 36 mouse miRNAs with |FC|>0.585 were screened out. Target gene prediction and functional enrichment of target genes were carried out on the 36 miRNAs screened out, the results showed that target gene were involved in many biologocal process, such as “inflammatory response”, “immune response” and “signal transduction”. KEGG analysis showed that a series of pathways(“Notch signaling pathway”, “ferroptosis”, “cysteine and methionine metablism”) were involved in liver disease, indicating that E. multiloculari s induced the liver immunity reaction of hosts and activated signaling pathways related to immune response, such as Notch signaling pathway.
E. multiloculari s enters the liver tissue along with the blood circulation, the liver tissue will also generate immune response to resist infection and recruit a large number of inflammatory cells at the same time to release inflammatory cytokines, and finally play an anti-infection immune process. With the expansion of the parasite infection focus, the unbalanced between formation and degradation of fibrosis will aggravate the degree of liver fibrosis. Therefore, this study focuses on three aspects(inflammatory response, immune response and fibrosis formation) to search for miRNAs related to liver injury. In this study, we screened a total of four miRNAs and four miRNA target genes, which were mmu-miR-30e-3p and IL-1rn, mmu-miR-203-3p and ctss, mmu-miR-125b-5p and was, mmu-miR-30c-2-3p and prr5l. Wei Cong and colleagues suggested that mmu-miR-30e-3p were also differentially expressed in liver tissue from rats with acute Toxoplasma gondiiinfection26, however, mmu-miR-30e-3p targeting IL-1rn regulates the inflammatory response caused by parasitic infections and no studies have been reported. Hu Y and his colleagues found that miR-203-3p may bind to vascular endothelial growth factor A (Vegfa)and participate in snhg8-mediated apoptosis and angiogenesis in AML cells27. Moreover, mmu-miR-203-3p identified as potential diagnostic biomarkers and indicators of Sjögren’s Syndrome28, however, there are no studies have been reported on mmu-miR-203-3p in liver injury caused by parasitic infections. mmu-miR-125b-5p is extensively involved in biological processes such as tua protein phosphorylation, cerebral ischemic tolerance and neuroregeneration29. In recent years, it has also been reported that mmu-miR-125b-5p was found to be downregulated in the peripheral blood of Trichinella-infected mice30. None of the four liver injury-associated miRNAs screened in this study have been studied in models of liver injury, and these miRNAs may serve as potential diagnostic targets for AE.