Experimental Research Of Effects Of Dexamethasone On Intrauterine Infection Cause Fetal Mouse Tissue Expression Of TNF-α、S-100and White Matter Damage

Objectives：1.To research the effect of tumor necrosis factor-α and S-100proteinexpressions in brain tissue of fetal rats with intrauterine infection and the role ofTNF-α and S-100in white matter damage.2. To study the effect of dexamethasone on the expression of TNF-ɑ,S-100inthe brain tissue of fetal rats induced by intrauterine infection and to exploredexamethasone on cerebral white matter damage in fetal rats with intrauterineinfection protection.Methods：1.Grouping：A total of40clean healthy adult Sprague-Dawley (SD) rats (male10, weight:300~350g;female30,weight:200~250g) were left at room temperature for18℃~20℃,relative humidity40%~70%of the barrier system.After a week ofenvironment adaption, they would be pressured in workenvironment cage at17:00PM which divided by3:1.Surfing finding Yin Shuai as the first day of gestation in thenext morning at six o’clock.The17,18days of pregnant SD rats were randomlydivided into three groups(n=10in each group):1.normal saline control group(Controlgroup);2.the intrauterine infection group(LPS group);3.the Dexamethasonegroup(Dex group).2.Model building and intervention:Building intrauterine infection modelaccorded to Bell’s method.we set the LPS group rats through intraperitoneal LPSadministration (350μg/kg);In Dex group,the rats were treated with LPS350μg/kg andafter1hour Dex5mg/kg simultaneously;In control group,the rats were administratedof the same volume of pyrogen-free saline,placed in a clean cage after theoperation,feeding as usual.3.Observing and testing: To observe the generation of pregnant rats after druginfusion,weather there is the phenomenon such as abortion,stillbirth and record thenumber of newborn mice,body weight and brain weight.Brain tissues were collectedfrom the fetal rat after drug infusion3h,6h,24h,48h(eight rats at each time point) to test the following indexes:the pathological of uterus,placental and brain tissue wereobserved by microscope;The expressions of TNF-α andS-100in injured brain cellswere detected by immunohistochemistry methods.Results：1.The general appearances and childbirth of the pregnant rats:Thee groups ofpregnant rats had no abnormal phenomenon after injection.There were no stillbirthand miscarriage,99survival newborns or fetuses in NS group.There were2stillbirths,7dead fetus and86newborns or fetuses in LPS group.In Dex group,1stillbirth and91newborns or fetal rats.2. The changes of weight and brain weight from fetal rats in each group: Theweight and brain weight of rats in LPS group is lighter than the control group,whichwere significantly (P＜0.05);the weight and brain weight from the Dex groupcompared with the LPS group were significantly increased(P＜0.05),but reducedwhen it compared with the control group,which the difference was not statisticallysignificant(P>0.05).3.The pathological changes of placenta and uterine：Observed by HE stainingunder optical microscope. In the LPS group,the placenta fibrous tissue washyperplasia,the vessel wall was thickening and the bureaucratic was irregular whichthere was neutrophil infiltration in severe position.The uterus congestion,he-morrhage,edema,a large of number of neutrophils and lymphocytes infiltration wereclearly visible. While in the control group, such changes could be observed: the colorof placental was bright red,a lot of trophoblast cells and red blood cells werevisible,the blood supply was rich as well as there was no significant inflammatoryresponse in the uterus.The placental from the Dex group blood supply was richer thanthe LPS group,but still had some inflammatory cells.the placental had no significantcongestion and a small amount of neutrophil infiltration.4. The pathological changes of brain tissue：In the LPS group:the brain tissuecellular was level clear,the neuronal morphology and structure was basic completeafter injection of3hours.the nerve cells were edema,the tissue was loose and thelumen gap was increased after injection of6hours.the number of nerve cells wassignificantly reduced,the cells were enlargement, cytoplasm lightly stained,nuclear chromatin unclear and focal hemorrhage after injection of24hours. The nerve fibersin the white matter were disorder,thickness uneven and intraventricular hemorrhageand capillary bleeding were also observed after injection of48hours.Comparing tothe LPS group,the fetal rat brain tissue morphological changes had different degreesof improvement at the corresponding time.In the control group,the nerve cells’structure were integrity and orderly layout,nuclear light,nucleoli clear.5. Expressions of TNF-α and S-100protein in each group:The expressions ofTNF-α and S-100protein in the control group were weakly positive and no significantdifferences at each time(P>0.05);While in LPS group,the expressions of TNF-α andS-100protein were significantly increased compared with the controlgroup(P<0.01);In Dex group,the expression level of TNF-α and S-100proteincompared with the LPS group were significantly decreased(P<0.01),compared withthe control group increased significantly (P<0.01).6.The correlation analysis between expressions of S-100and TNF-ɑ:S-100andTNF-ɑ positive expressions at different time points were correlated （In LPSgroup:r=0.547，P<0.01;In Dex group:r=0.843，P<0.01）。Conclusions：1. The rat model of intrauterine infection established by intraperitoneal injectionof LPS in17、18days of pregnant rats causing fetal rat body weight and brain weightreduced and the number of nerve cells decreased,edema,the nerve fibers in whitematter disorder,uneven thickness and focal hemorrhage,suggest that intrauterineinfection can cause brain damage,the occurrence of white matter lesions.2.The change of brain tissue of S-100and TNF-α expressions from fetal ratscaused by intrauterine infection,indicating that S-100and TNF-α may be involved inthe pathogenesis of cerebral white matter injury.3.The expressions of cytokines TNF-alpha and S-100protein from fetal ratsbrain tissue had the same trend which was positively correlated after intrauterineinfection,suggesting that TNF-α and S-100may have a synergistic effect in the whitematter damage. 4.Dexamethasone plays a protective role in cerebral white matter injury causedby intrauterine infection by inhibiting the expression of brain tissue S-100and TNF-αso as to reducing nerve cell inflammatory reaction.