| Objective:To establish a neonatal rat model of acute respiratory distress syndrome(ARDS)lung injury by intraperitoneal injection of lipopolysaccharide(LPS).The expression levels of miR-34 a and TNF-ɑ in rat lung tissues at different time points were detected,and the pathological morphological changes of rat lung tissues were observed.To explore the changes and interactions of miR-34 a and TNF-ɑ in neonatal acute respiratory distress syndrome(NARDS).It provides a possible theoretical basis for the early diagnosis and treatment of NARDS.Methods: 1.Eighty 7-day-old neonatal SD rats were randomly divided into 2 groups with40 rats in each group.The animal model of NARDS was established by intraperitoneal injection of 4mg/kg LPS solution,and the experimental group was established.A healthy reference group was established by intraperitoneal injection of 4m L/kg isotonic Na CL solution.2.The mental response,nasolabial color,appetite and other performance of newborn SD rats in the experimental group and the control group at 3h、6h、12h and 24 h were observed respectively,and the changes of heart rate,respiratory rate and body temperature were collected and recorded for comparison.3.The surface changes of the lung tissue of the experimental group and the control group in the above four phase groups were observed by naked eye,the W/D value of the lung tissue was determined,and the lung tissue was chemically stained(HE staining)to observe the pathological changes of the lung tissue under the optical microscope,and the pathological score of lung injury was performed.4.Quantitative Real-time PCR(q RT-PCR)and Enzyme-linked immune sorbent were used assay(ELISA)was used to measure the expression levels of miR-34 a and TNF-ɑ in lung tissues of the experimental group and control group in the above four time periods.5.Statistical analysis of experimental data was performed using SPSS22.0 statistical software package for statistical processing,P<0.05 was considered statistically significant.Result:1.At the beginning of the experiment,it was observed that the coat of rats in the normal reference group was glossy,and their response to external stimuli,eating ability and general condition were normal,without morbidity.However,with the time of injury,the rats,which were injected with LPS solution intraperitoneally,showed dull coat,cyanosis at the ends of lips and limbs,respiratory distress,indifferent response to external stimuli,significant decrease in activity,food resistance,and whole body temperature reduction.2.The macroscopic observation of the lung tissue of rats showed that the morphology and performance of the lung tissue of rats in the normal control group were normal,the surface of the lung tissue was smooth and elastic,and no hyperemia,edema and exudation were observed.With the increase of LPS injury time,the lung tissue volume of rats in the experimental group increased,elasticity decreased,bleeding,edema and exudation became more obvious,and the lung tissue injury of rats in the LPS-24 h group was the most serious,some disseminated bleeding could be seen,which could affect multiple lung lobes.3.Pathological structure of lung tissue was observed under light microscope,and the structure of alveolar cavity in the lung tissue of rats in the normal reference group was clear and complete,without exudation;In the experimental group,as time went by,the pulmonary tissue edema of rats was gradually more obvious than before,the structure of alveolar cavity was disorganized,and red blood cell infiltration could be seen in the alveolar cavity and the interstitium.The alveolar cavity collapsed,and part of the alveolar burst and fused into pulmonary bulla.4.At four time conditions(3h、6h、12h、24h),the experimental group and the control group were compared respectively,and the difference of lung tissue pathological score was significant(P<0.05).The difference was statistically significant(P<0.05).5.The W/D value of neonatal rat lung tissue in the experimental group increased gradually with the extension of time,reached the peak value at 12 h,and then began to decrease gradually,and was basically close to the control group at 24 h,and there was no statistical significance in the W/D value of lung tissue between 3h and 24h(P>0.05).There was significant difference between 6h and 12h(P<0.05).6.The expression level of miR-34 a and TNF-ɑ in the lung tissues of the experimental group was significantly different from that of the control group(P < 0.05),and the concentration of TNF-ɑ reached its peak in the LPS-12 h group.Subsequently,inter-group comparison of the experimental group was carried out for each phase group,and the differences were also statistically significant(P<0.05).The expression amount of miR-34 a and TNF-ɑ in lung tissues of the experimental group increased with the extension of LPS injury time.7.Pearson correlation statistical analysis showed that the expression of miR-34 a and TNF-ɑ in the lung tissues of newborn rats in the experimental group had a positive linear correlation(r=0.607,P<0.05),while no significant linear correlation was found in the expression of mir-34 a and TNF-alpha in the lung tissues of control group(r=0.131,P>0.05).Conclusion:1.A stable animal model of NARDS was successfully established by intraperitoneal injection of LPS(4mg/kg).2.When neonatal rats develop NARDS,the expression of miR-34 a in lung tissue is significantly increased and has a sequential nature.miR-34 a is expected to be an early biomarker for the diagnosis of NARDS.3.When neonatal rats develop NARDS,the expression level of TNF-ɑ in lung tissue is significantly increased,and is positively correlated with the expression level of miR-34 a.It is speculated that miR-34 a may act on a certain signaling pathway or mediate the expression of TNF-ɑ through inflammatory response,thereby regulating the lung tissue injury induced by LPS.Participate in the molecular regulation mechanism and pathogenesis of NARDS,and thus affect the progression of NARDS. |
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