Effect Of DDR1a On Th17/Treg Balance In Experimental Colitis Mice

Objective:To investigate whether DDR1a affects Th17/Treg balance in mice with ulcerative colitis and its possible mechanism.Methods:Wild Balb/c mice and DDR1a^+/-Balb/c mice（6-8 weeks,20±2g）were used in the experiment.The mice were divided into 4 groups（7 mice in each group）:wild type mouse normal control group（WT+CON）,wild type mouse model group（WT+DSS）,DDR1a^+/-mouse control group(DDR1a^+/-+CON),DDR1a^+/-mouse model group(DDR1a^+/-+DSS).The control group was given distilled water,and the model was given 3%DSS solution for 7 days to induce the mouse ulcerative colitis model.During the experiment,the mice’s daily activity,weight change,occult blood,blood in the stool and other indicators were recorded.On the 8th day,the mice were anesthetized with 5%chloral hydrate,and the mice’s blood was collected.After cervical dislocation,the colon and spleen were collected.Flow cytometry was used to detect the ratio of Th17 and Treg cells to CD4+T cells in the blood and spleen of the mice.RT-PCR was used to detect the expression of RORγt,Foxp3,IL-17A and IL-10in the intestinal tissue.Results:（1）The wild type mice and DDR1a^+/-mice modeled by DSS all showed different degrees of loose stools,blood in the stool,weight loss and other symptoms.The pathological score of the KO DSS group was significantly lower than that of the WT DSS group.（5.67±0.58 vs 10.33±0.42,p<0.001）;（2）Compared with the WT CON group,the Th17/CD4+T ratio in the blood of the WT DSS group is（1.43±0.14 vs 0.76±0.10,p<0.01）,the ratio of Th17/CD4+T in the spleen is（1.83±0.16 vs 0.64±0.11,p<0.001）;Compared with the DDR1a^+/-CON group,the Th17/CD4+T ratio in the blood of the DDR1a^+/-DSS group is（0.95±0.32 vs 0.72±0.18,p>0.05）,the ratio of Th17/CD4+T in the spleen is（1.10±0.33 vs 0.92±0.06,p>0.05）;Compared with the WT CON group,the ratio of Treg/CD4+T in the blood of the WT DSS group is（0.28±0.15 vs 0.72±0.07,p<0.05）,the ratio of Treg/CD4+T in the spleen is（1.03±0.21 vs 3.24±0.90,p>0.05）;Compared with the DDR1a^+/-CON group,the ratio of Treg/CD4+T in the blood of the DDR1a^+/-DSS group is（0.26±0.16vs 0.24±0.12,p>0.05）,the ratio of Treg/CD4+T in the spleen is（3.24±0.61 vs4.46±1.37,p>0.05）;（3）Comparison of RORγt in DDR1a^+/-DSS group with mice in WT DSS group（27.69±34.01 vs 67.75±22.55,p<0.05）;comparison of IL-17A in DDR1a^+/-DSS group with mice in WT DSS group（505.70±249.10 vs 3541.12±3987.23,p<0.001）;Fxop3 in DDR1a^+/-DSS group compared with WT DSS group（546.10±722.30 vs1170.42±1785.37,p<0.05）;IL-10 in DDR1a^+/-DSS group and WT DSS group Compared（33.70±13.84 vs 50.76±6.29,p<0.001）.Conclusions:（1）Knockdown of DDR1a reduces DSS-induced colitis in mice;（2）Knockdown of DDR1a may play an anti-inflammatory effect by affecting the balance of Th17/Treg and inhibiting the expression of the inflammatory cytokine IL-17A;（3）DDR1a may become a new target for clinical treatment of UC.