Effect Of Claudin-7 And P53 On Lung Tissue Of Hyperoxia-induced Neonatal Rats With BPD

Objective:Bronchopulmonary dysplasia（BPD）is a chronic respiratory disease commonly seen in premature infants,which is characterized by extremely low birth weight or ultra-low birth weight infants.Due to the development of obstetric medicine and neonatal care,the treatment rate of premature infants with low gestational age and birth weight is increasing,but the risk of bronchopulmonary dysplasia has not decreased.The damage of alveolar epithelial cells is the main link of BPD.The typical pathological features are microvascular and alveolar dysplasia,and the main early manifestations are pulmonary edema.In recent years,experiments have confirmed that Claudin-7 is involved in lung injury and regulating the function of alveolar cell development,and the p53 pathway is related to it,which is an important pathway for the occurrence and development of BPD.This study aims to explore the difference in its expression between the BPD model group and the control group,as well as the expression changes of P53 protein,so as to clarify whether Claudin-7 and p53 play an important role in the occurrence and development of BPD,and whether they are expected to become new therapeutic targets.Methods:Neonatal rats within 12 hours of birth were randomly divided into normal oxygen control group（RA group）（FiO₂=21%）and high oxygen model group（BPD group）（FiO₂=85%）,and the moment was defined as day0.On day 4,day 7,day 10 and day 14,8 rats were randomly selected to take lung tissues and observe the pathological morphology of lung tissues.Part of the tissues were selected to make paraffin sections for HE staining and immunohistochemistry.The remaining tissues were rapidly frozen to improve Western Blot and QRT-PCR detection.The expression levels of Claudin-7protein and p53m RNA were determined by QRT-PCR,and the relative expression levels were expressed by 2^-ΔΔCT.The expressions of Claudin-7 and p53 were detected by Western Blot.The expression of Claudin-7 protein in alveolar epithelial cells was detected by immunohistochemistry.Results:（1）The model was established successfully by observing the morphology of fresh lung tissue and paraffin sections stained by HE.With the increase of age,the lung tissue in RA group was soft and elastic,and the alveoli were well developed.BPD group lung tissue edema,poor elasticity,alveolar neoteny phenomenon.RAC results showed that compared with RA group,BPD group had enlarged alveolar cavity,obvious alveolar fusion,decreased alveolar number,and developmental disorder,and the differences were statistically significant（P<0.05）.（2）Compared with RA group,Claudin-7 m RNA level in BPDgroup decreased at four time points,whereas p53 m RNA level increased,the difference was statistically significant（P<0.05）.（3）Western blot results showed that,compared with RA group,Claudin-7 protein expression in BPD group decreased to different degrees,p53 protein expression increased,and the difference was statistically significant（P<0.05）.（4）Immunohistochemical results showed that Claudin-7 was mainly expressed in the cytoplasm.Semi-quantitative analysis showed that Claudin-7expression in lung tissue of RA group was higher than that of BPD group,and the difference was statistically significant（P<0.05）.Conclusion:In this study,it was confirmed by animal experiments that Claudin-7transcription and protein decreased in the lung tissue of neonatal rats in the high oxygen group,while p53 transcription and expression increased,and the two were negatively correlated,indicating that Claudin-7 and p53 may have negative feedback regulation or some inhibition to adapt to the response of alveolar epithelial cells to disease repair.Regulation of Claudin-7 expression may be a potential method for diagnosis,treatment and prevention of BPD.