Dynamic change of intestinal cells apoptosis in intestinal injury of neonatal rat necrotizing enterocolitis model

Objective To observe the change of intestinal cells apoptosis severity in neonatal rate NEC progression,and analyze its correlation with intestinal injury.Methods Fourty neonatal Sprague-Dawley rats(48 hours olds,weight:5-10 g)were randomly divided into the model group(n=32)and the control group(n=8).Rats in the model group were fed with rat milk substitute after 48hours of life,and various stimulation(suffocated with 100% nitrogen gas for 90s,exposed under 4 ℃ condition for 10 minutes,two times a day)for longest duration of 3 days.Rats in the model group further subdivided evenly into four groups,and executed at 24 hours(M24,n=8),48 hours(M48,n=8),72 hours(M72,n=8)after stimulation started,and 96 hours later(24 hours after the last stimulation,M96,n=8).At the end of the experiment,the rats in the control group were also executed.Intestines of both groups were collected for electron microscopic observation and estimated the apoptosis rate of intestinal cells(flow cytometer).Histological score ≥2 were diagnosed as NEC.The ileocecum proximal intestine of one rat from each group was obtained for pathological examination and evaluating the score of intestinal injury.SPSS 11.0 software for Windows was used in all statistical tests.α=0.05 was considered significant.Results Transmission electron microscopy showed a large number of apoptotic cells in the model group's intestinal mucosa,and formatted apoptotic bodies.The score of intestinal injury in the control group,M24,M48,M72,M96 group were 0.08±0.15,1.38±0.42,1.46±0.69,1.58±0.30,3.33±0.59 and the apoptosis rate of intestinal cells were 4.8%±2.9%,12.8%±6.3%,14.9%±5.5%,17.7%±5.5%,27.6%±9.9%,respectively.The intestinal injury severity was significantly correlated with the cell apoptosis ratio positively(r=0.853,P0.01).Conclusion The increase of neonatal rate intestinal cells apoptosis ratio is the initial event of NEC intestinal tissue injury;as time progress,intestinal cell apoptosis would increase;the incensement of intestinal cell apoptosis is the fundamental pathophysiology in intestinal progressive injury.