Experimental Study Of Recombinant Human Intestinal Trefoil Factor On Intestinal Mucosal Barrier Function In Burned Mice

Objective To observe the effects of recombinant human intestinal trefoil factor(rhITF) on intestinal mucosal barrier function in burned mice and explore its possiblemechanism.Methods Two hundred and seventy adult BALB/c mice (weighing20g to25g)were randomly divided into normal control (C) group, burn control (B) group, and burns+rhITF (B+I) group. Group C received anesthesia and shaving, but not burn; group Band B+I were treated with90℃water soak for7seconds [1], caused30%total bodysurface area of full thickness burn. After burn injury, groups were fed with normal dietand drinking water; In group B+I (6h after burn injury or recovery from anesthesia)intragastric administration of rhITF (1mg/kg.d, bid), B group were perfused with thesame volume of saline (bid).(1) The histomorphology changes of mouse ileum post burn12h,24h,48h,72hwere observed by HE staining;(2) The changes of mouse ileum mucous chemical properties post burn12h,24h,48h,72h were observed by histochemical staining;(3) The mouse ileal mucus thickness, content of mucoprotein and hexose inmucus post burn12h,24h,48h,72h were detected by using alcian blue binding,coomassie brilliant blue (G-250),phenol;(4) The intestinal intraepithelial lymphocytes(IELs) of mouse were extracted bydensity gradient centrifugation and the apoptosis rate of IEL was tested by flowcytometry post burn12h,24h,48h,72h;(5) The contents of IFN-γ and IL-4in the culture supernatants of IEL post burn12h,24h,48h,72h were measured by ELISA.Results (1) Compared with group C, the obvious pathological changes occurredin the group B, the intestinal mucosal edema, hyperemia at12post-burn hours(PBH);the intestinal mucosal cell degeneration, villous collapse at24PBH; the villi fell off,microvilli disappeared,capillary injection at48PBH; the villi fractured,necrosed, fell off,a large number of lymphocytes increased, submucosal congested at72PBH; compared with group B, the damage of group B+I reduced to a different extent, mainly for the villiswelling, mucosal congestion and edema, capillary hyperemi.(2) Compared with groupC, the neutral mucus secretion increased, while the acid mucus especially sulphatemucus secretion decreased in group B; compared with group B, the acidic mucussecretion increased, and neutral mucus secretion decreased in group B+I.(3) Comparedwith group C, the intestinal mucus thickness and the content of mucoprotein in group Bincreased temporarily at12PBH, then gradually decreased, both of them had significantdifferences at72PBH (P<0.01), while the content of hexose gradually reduced,48-72hafter injury was remarkably lower (P<0.01);compared with group B, the intestinalmucus thickness and the content of hexose in group B+I increased,48-72h after injurywere notably higher (P<0.01),but the content of mucoprotein had no significantdifferences (P>0.05).(4) Compared with group C, the apoptosis rate of IEL increased ingroup B, especially at12PBH (P<0.01), compared with group B, the apoptosis rate ofIEL decreased in group B+I.(5) Compared with group C, the content of IFN-γ in theculture supernatants of IEL decreased in group B, especially at24PBH (P<0.01),andthe content of IL-4in the culture supernatants reduced at12PBH, then graduallyincreased，there was notably difference at72PBH (P<0.01); compared with group B,the content of IFN-γ increased in varying degrees in group B+I,while the content ofIL-4decreased in different degrees.Conclusion (1) Intestinal mucus properties is changed after severe burns, ITFcan promote the differentiation and maturation of goblet cells, increase intestinal mucussecretion and maintain the normal chemical structure, then effectively maintainintestinal mucus barrier;(2) Intestinal mucosal structure and function are destroyed bysevere burns, ITF can reduce the intestinal mucosa damage, promote epithelial cellrepair and the structural integrity of intestinal epithelium;(3) IEL apoptosis increasedafter burn injury, ITF can reduce the apoptosis rate of IEL, maintain the stability ofintestinal immune function;(4) The contents of Th1and Th2cytokines secreted by IELlost the balance after burns, ITF can rebuild the balance between Th1and Th2, andmaintain the intestinal mucosal immune homeostasis.