Study On The Predictive Effect Of The Ectodomain Of Discoidin Domain Receptor 1 (DDR1) On Liver Fibrosis

【Objective】Discoidin domain receptor 1(DDR1)is one kind of transmembrane collagen receptor of the tyrosine kinases(RTKs)family,which is activated by collagens in epithelial cells.In fibrotic condition,DDR1 reconstructs collagen alignment through mechanical reorganization.At the same time,under the condition of collagen binding,DDR1 cleaving occurs,then a significant amount of shedding released into the blood.There is a lot of collagen deposition around the liver cells in patients with fibrosis.Whether extracellular DDR1 can be detected in serum as a shedding fragment and as a serum marker to diagnose and evaluate liver fibrosis has not been reported in the literature.By observing the relationship between the concentrations of N-terminal fragment from serum and hepatic fibrosis,this paper tries to find a new method to predict hepatic fibrosis.【Methods】1.By stimulating HEK293 T cells overexpressing DDR1 with different concentrations of collagen I and at different time points,we detected whether exfoliated DDR1 existed in the supernatant of culture medium.Type I collagen was used to stimulate normal hepatocytes of mice and normal hepatocytes of human at different time points.Subsequently,we observed the concentration of DDR1 in the supernatant of the culture medium.2.Then we established BDL and CCL4 models of liver fibrosis in mice,observed the degree of liver fibrosis and collagen deposition,and detected the relationship between the degree of liver fibrosis and serum extracellular DDR1 concentration.3.Observe the pathological changes of liver cirrhosis tissue samples,and collect the serum of normal people and patients with liver cirrhosis for detection,and compare the difference of serum extracellular DDR1 concentration.【Results】1.HEK293 T cell lines were treated with collagen I at 0,2,4,6,8 hours and at different concentrations of collagen I at 0,25,50 and 75 ug/ml,respectively.At the same time,collagen I at 50 ug/ml concentration stimulated mice and human normal hepatocyte lines at 0,4,8,18 and 24 hours,respectively.It was found that the extracellular shedding of DDR1 increased with the prolongation of collagen treatment time and the increase of collagen concentration.2.Collagen deposition is related to the degree of hepatic fibrosis in vivo: In CCL4 and BDL mice models,after 0,6,9,12 weeks and 2,5,10 and 15 days of treatment,histopathological findings showed that hepatic fibrosis gradually increased with the prolongation of treatment time,and collagen deposition increased with the aggravation of fibrosis,while the content of serum extracellular DDR1 increased.3.With the preliminary clinical study,56 patients with hepatic fibrosis and 200 normal people with non-hepatic fibrosis were studied.According to Laennec classification,the deposition of collagen fibers in liver increased with the severity of grading.At the same time,the content of DDR1 in serum of patients with hepatic cirrhosis was significantly higher than that of patients with non-hepatic cirrhosis.【Conclusion】In this study,we found that collagen deposition around the liver increased with the aggravation of fibrosis,and collagen-stimulated extracellular shedding of discoid domain receptor-1 increased in serum.The serum level of discoid domain receptor-1 in patients with hepatic fibrosis and non-hepatic fibrosis normal subjects showed that it could be used as a new serological marker for predicting hepatic fibrosis.