| Sepsis is a common severe disease in intensive care unit,its incidence and mortality rates are still high.Studies showed that there are 21 million population infection induced sepsis globally every year.The intestinal barrier dysfunction usually occurred in early sepsis,it can directly cause the increase of intestinal permeability and leads to the translocation of bacteria from the intestine into the blood,which can aggravate sepsis and cause the multiple organ dysfunction syndromes(MODS).Therefore,protecting the intestinal barrier function in sepsis is important.Mesenchymal stem cells(MSC),a kind of pluripotent stem cells,can differentiate into epithelial cells,adipocytes,osteoblasts,and secrete a variety of nutrition chemokines to repair tissue damage.Studies demonstrated that MSC could improve the survival rates in sepsis rats.In addition,MSC has beneficial effect for intestinal barrier in many kinds of gut diseases like inflammatory bowel disease,radioactive intestinal injury,ischemia reperfusion injury and so on.While whether MSC has protective effect on intestinal barrier dysfunction in sepsis is not clear.MSC still has some immunogenicity,and easy to take place apoptosis when transplanted into the body,thus how to enhance the efficacy of MSC has become an urgent issue.Poly(I:C)(inosine acid cytidine acid)is defined as a double-stranded RNA analogues,which belongs to toll-like 3 agonist.Previous studies confirmed that Poly(I:C)could enhance the protective effects of MSC in liver,heart through increasing its migration ability and paracrine function.However,whether Poly(I:C)could enhance the protective of MSC on intestinal barrier function in sepsis rats is not known.With cecal ligation and puncture(CLP)sepsis rats and lipopolysaccharide-stimulated intestinal epithelial cell,the effects and underlying mechanism of MSC and Poly(I:C)pre-stimulated MSC on intestinal barrier function in sepsis rats were observed.The main research contents:Experiments divided into two parts:(1)Part I,with sepsis rats,the intestinal permeability,the intestinal pathological morphology and the expression of ZO-1 in vivo were observed.In vitro,the trans-epithelial electrical resistance(TER)and tight junction protein ZO-1 of intestinal epithelial cell(IEC-6)were measured to observe the effects of MSC and Poly(I:C)pretreatment to intestinal barrier function.(2)Part II,the direct and indirect mechanism including MSC planted in intestine and the paracrine function of MSC were observed.The main results:PartⅠ: The protective effect of MSC and pre-stimulated by Poly(I:C)on intestinal barrier function after sepsis.1.As compared with normal control group,the intestinal permeability,blood D-Lac and endotoxin in sepsis rats were significantly increased.The intestinal villi and the expression of tight junction ZO-1 in intestinal tissue were significantly decreased.After conventional treatment,the intestinal barrier function was slightly improved.The levels of blood D-Lac and endotoxin were slightly reduced.The intestinal injury had some extent of alleviation.MSC treatment had better effect on intestinal barrier function than the CT treatment.The levels of blood D-Lac and endotoxin were obviously reduced.Poly(I:C)pre-stimulation significantly enhanced the protective effects of MSC on intestinal barrier function.The concentration of blood D-Lac and endotoxin were significantly reduced in poly(I:C)pre-stimulated MSC group.The intestinal glands and villi were obviously increased and the inflammatory cells were significantly decreased in this group.The expression of ZO-1 in intestine was also obviously increased in this group.2.As compared with the normal control group,the intestinal epithelial cell permeability indicated by TER and the expression of ZO-1 were significantly decreased after LPS stimulated.After co-cultured with MSC,the intestinal epithelial cell permeability(TER)and the expression of ZO-1 were significantly increased.Poly(I:C)pre-stimulation MSC significantly enhanced the protective effect of MSC on intestinal epithelial cell after LPS stimulation.The intestinal epithelial cell permeability was significantly improved in this group.These results indicate that MSC has protective effects on intestinal barrier function in sepsis rats and Poly(I:C)can enhance the protection of MSC.PartⅡ: The mechanism of MSC on intestinal barrier function in sepsis rats.1.MSC repairs the intestinal tissue damage by directly planted in intestinal mucosa.The results showed that the plantation of MSC marked by GFP in intestinal mucosa was found after infusion in sepsis rats.After Poly(I:C)stimulation,more MSCs planted in intestinal mucosa.This indicates that Poly(I:C)enhances the protective effects of MSC by increasing its survival numbers in rats.2.The paracrine function of MSC: After MSC treatment,the fibroblast growth factor(FGF),transforming growth factors(TGF-β),stromalcell-derived factor-1α(SDF-1α)were obviously increased.Poly(I:C)pre-stimulation could enhance the paracrine function of MSC.Further study found that the supernatant of MSC could protect intestinal epithelial cell from the injury induced by LPS.It could increase the expression of ZO-1 and improve the permeability of intestinal epithelial cells after LPS stimulation.Conclusion:1.MSC can protect the intestinal barrier function in sepsis rats.Poly(I:C)pre-stimulation can enhance the protective effects of MSC on intestinal barrier function.2.The mechanism that MSC protects the intestinal barrier function is mainly related to the plantation of MSC in intestinal mucosa and its paracrine function.Poly(I:C)can enhance the therapeutic effects of MSC in sepsis rats by increasing the survival numbers and paracrine function of MSC. |
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