The Colonic Expression Of Flt3and Flt3L In The Mice Model Of Ulcerative Colitis

Objective: Ulcerative colitis (UC) is a kind of Inflammatory Bowel Disease (IBD),causing ulcerative changes in the mucosal and sub-mucosal layers, but the etiology ofUC still not so clear. In recent years, dendritic cell (DC) and regulatory T-Cell (T reg)are hot topic to study and we can find a lot of scholarly articles on these topics. Thecurrent opinion about immunomodulatory between DC and T reg play an important rolein UC inflammatory reaction. Fms-like tyrosine kinase3(Flt3) and its’ ligand (Flt3ligand, Flt3L) involved in regulation of inflammatory reaction between DC and T reg.We used the mice model of UC in this study and take record of mice’s general conditionand observed disease activity index. Hematoxylin and Eosin stain (H&E) of intestinalmucosa was used to find the pathological changes under light microscope. Moreover,the expression of DC and T reg were measured by cellular level detection method, anddivided into two groups according to normal expression and abnormal expression.Furthermore, Flt3/Flt3L expression was detected from the gene and its protein level.Our main objective was to discuss about the major role of DC, T reg and Flt3/Flt3L inthe process of UC development. Eventually, we would like to establish a theoreticalfoundation for the treatment of UC.Methods: The20BALB/c male mice models, weighing25g, were randomlydivided into two groups as normal group and model group. The animal model wasestablished by mice themselves drinking of dextran sulfate solution (DSS). Normalgroup drank distilled water. Model group drank50g/L DSS for7days. The micegeneral condition and DAI were recorded, and all of the mice were hanged after7daysto record the colonic mucosa damage index (CDMI). Hematoxylin and Eosin stain(H&E) of intestinal mucosa was used to find the pathological changes in UC model andnormal mice intestinal mucosa under light microscope. Moreover, the expression of DCand T-reg were detected by flow cytometry at cellular level, immunohistochemistry was used to detect the changes in ratio of Flt3expression, Flt3/Flt3L expression wasidentified by means of ELISA. Finally the Real-Time PCR was used to measure thegene changes of Flt3/Flt3L expression.Results:1． Model group DAI (3.15±0.28) and CDMI score (2.44±0.24) wassignificantly higher than the normal group (DAI0.00±0.00, CMDI0.00±0.00),(P<0.05),mentioned that the mice models are successful.2． Model group mucosal DC （0.19±0.18）%and T-reg expression on CD4+T cells （4.11±2.14）%detected by flow cytometry was significantly lower than thenormal group,(DC （2.83±1.52）%, T reg （14.02±1.73）%).(P<0.05)3． Density mean protein expression of colonic mucosal Flt3in model group（31.66±2.31）was lower than the normal group （82.19±5.34）, and model group hasaggregation.(P<0.05)4． Flt3L expression in blood of model group（36.25±6.34）pg/ml wassignificantly lower than normal （57.24±5.97）pg/ml and has statistical significant(P<0.05).5． Gene level mucosal Flt3mRNA expression（0.53±0.06）and Flt3L mRNAexpression （0.10±0.18）were significantly lower than normal Flt3（1.01±0.13）andFlt3L （1.01±0.25）.(P<0.05)Conclusions:Immuno-regulatory imbalance in DC and T reg are found in the mucosa of DSSinduced ulcerative colitis mice model, leading to impairing the signaling activity of Flt3and Flt3L in DC and T reg and eventually resulting in development of ulcerative colitis.