Preliminary Exploration And Establishment Of The Rat Model Of Sepsis

Objective:Sepsis is a common syndrome but difficult to treat in clinical,and the mortality is high at present.Animal models of sepsis is a necessary experimental platform to investigate the pathogenesis and the prevention and treatment of sepsis;and is also a difficulty in sepsis research.At present,the construction of animal models of sepsis are various.To seek a stability animal model of sepsis on incidence and pathophysiological processes is extremely important.In this study,our aim is to provide a suitable experimental animal model for sepsis clinical research by comparing different groups.Methods:(1)Wistar rats were randomly divided into 12 groups to establish a model of cecal ligation and puncture(CLP)according to the following three variables:percentage of the cecal ligation length(25%,50%,75%),size of the puncture needle(12-gauge needle,16-gauge needle)and the application of antibiotics after postoperative.And a normal control group and the sham group were also established.(2)According to the experimental objectives,Wistar rats were randomly divided into four groups which were normal control group,sham group and CLP groups and colon ascendens stent peritonitis(CASP)groups;then CASP groups were divided three subgroups according to the diameter of the inserted stent(14-,16-,and 18-gauge).The survival rate of 72h was observed after operation.The body weight change and serum interleukin(IL)-6,10 and tumor necrosis factor(TNF)-a levels were analyzed by enzyme linked immunosorbent assay(ELISA)in the groups at 6,12,24,48h after operation.Results:1.CLP model:(1)Postoperative general observation:less clinical signs of bacteremia within 12h,but postoperative 12h rats gradually began to appear obvious morbid state including piloerection,curled up,fatigue,lack of exercise,listlessness,eat less,diarrhea,eye exudate.Sham group rats appeared freedom of movement,responsive and normal eating.(2)The survival rate:Sham-operated rats all survived within 72h.After 12h,CLP groups began to die,and the mortality peak was within 48h.With the increasing of the length of cecal ligation,the survival reduced and difference was statistically significant(P<0.05).Though the survival rate of 12-gauge and 16-gauge of puncture needles group did not show statistically significant difference(P>0.05),the survival rate in 12-gauge group was lower than the 16-gauge group.The antibiotic group of survival rate was higher than non-antibiotic group,but the difference was not statistically significant(P>0.05).(3)Levels of serum inflammatory cytokines:Levels of serum IL-6,IL-10 and TNF-?in CLP model group were higher than those in the normal group and the sham group(P<0.01)at each time point and increased in the six hours then reached a peak at 12 hours,then began to decline.With the increasing of the length of cecal ligation,serum IL-6,IL-10 and TNF-a levels elevated in CLP group at each time point(P<0.01).IL-6,IL-10 and TNF-a levels of the 12-gauge group were higher than the 16-gauge group at some point in time(P<0.05).Serum IL-6,IL-10 and TNF-a levels in antibiotic group were lower than the non-antibiotic group at some point time(P<0.05).2.Comparison of CLP and CASP model:(1)Abdominal situs was analyzed after 24h and we found that an intra-abdominal abscess exhibiting in CLP rat;but CASP rat appeared massive edema,paralysis of the intestine and vasodilation of intestinal vessels.(2)Survival:The survival rate in CLP group was 45.8%and was 50%in CASP-18G which was higher than in 16G(33.3%)and 14G(8.3%);the difference between these three groups was statistically significant(P<0.01).(3)Changes in body weight:Weight loss in septic model groups were higher than the sham group(P<0.05).Body weight change in CASP group at 24h was higher than the CLP group(P<0.05).(4)Levels of serum inflammatory cytokines:The levels of serum IL-6,IL-10 and TNF-a in sepsis model group at any time point were significantly higher than normal control group and sham group(P<0.01).Also,The levels of serum IL-6,IL-10 and TNF-? in CASP group at each time point were significantly higher than CLP group(P<0.01).With the diameter of the inserted stent increasing,serum IL-6,IL-10 and TNF-a levels elevated(P<0.05,except for IL-10 and TNF-? at 48h).Conclusion:(1)Establishment of septic infectious peritonitis rat model by CLP and CASP methods;(2)The length of cecal ligation and the size of diameter of the inserted stent were an important determinant factors on survival rate and the inflammatory response of rats in CLP and CASP model respectively.By changing the length of the cecal ligation or the size of diameter of the inserted stent can establish different extent infection of the septic rat models.(3)The CLP model focused on the pathological changes of intra-abdominal abscess formation.But CASP model was similar to the clinical course of diffuse peritonitis.To analyze different aspects of sepsis by CLP as well as CASP which offer different advantages.