Expressions And Mechanisms Of VEGF And Ang In Model Rats With Lung Injury Of Hyperoxia

Bronchopulmonary dysplasia (BPD) is an important complication of premature infants, and it is a common chronic diseases of respiratory system for infants. But its certain etiological factors and pathogenesis are not clear completely, inhaling hyperoxia for a long time to lead to lung injury is a main reason, and some investigations showed that arrested lung development was the main pathological change. As well as known that immature lung development and oxygen toxicity are the key risk factors. Inhaling hyperoxia is one of the leading causes for prmature babies’ bronchopulmonary dysplasia. Normal vascular development of lung includes vasculogenesis and angiogenesis. Recently, some researches considered that abnormal expression of lung development regulating factors would influence the normal morphological and vascular development of lung. Vascular endothelial growth factor(VEGF) and Angiopoietin(Ang) are two main factors which play an important role in morphological development of lung, tissue moulding and vascular remodeling. At present, it is considered that inhaling hyperoxia leading to abnormal expression of VEGF and Ang is significant in arrested lung development. Explore related pathological mechanism of VEGF and Ang in model rats with lung injury caused by hypoxia and their influence of alveoli and vascular development of lung will provide a new strategy and direction in prevention and cure of neonatal bronchopulmonary dysplasia.Objectives1. Make a neonatal rats BPD model by hypoxia, to observe the pathological change of lung, reveal the pathological mechanism of BPD in further to provide experimental fundation for new ways about early intervention and gene intervention therapy.2. Explore expression characters of VEGF and Ang mRNA and protein in neonatal rats’lungs with lung injury by hyperoxia, invesigate the relationship between them and bronchopulmonary dysplasia to provide experimental fundation for research about mechanism of BPD.Methods1. The neonatal Sprague-Dawley rats were used as study objects after birth for2-3days, and exposured to hyperoxia(≥95%) for1,3or7days to make a model with BPD.2. The neonatal rats were divided into contol groups and hyperoxia groups at random; lung histological changes of neonatal Sprague-Dawley rats in each group were observed and compared through light microscope. Number, diameter, area of alveoli and alveolar septum thickness were measured by image manipulation and analysis software. Quantitive analysis of histological changes were did for comparing difference of lung histomophology appearnce between groups.3. Expression of VEGF and Ang mRNA were detected by real time fluorescent quantitation polymerase chain reaction, and the interference effect of VEGF and Ang for lung development were evaluated combined with the morphological changes of lung.4. Protein expression of VEGF and Ang were detected by Western blotting, and the interference effect of VEGF and Ang for lung development were evaluated combined with the morphological changes of lung.Results1. Make a model with lung injury, BPD of neonatal rats:neonatal rats were exposed to hyperoxia(≥95%) for7days, without activity, dull reaction, their weight and length increased slowly; compared rats’ weight and length of model group with control group, it was very different (P<0.05).2. Observation of lung histological changes of rats in each group with light microscope:in low view, the lung tissue in noraml rats showed clear and alveolar structure, uniform size, no fluid exudation; the lung tissue of hyperoxia groups displayed thinner walls of alveoli, simple alveolar structure, fewer and larger alveoli, expanded and shrinked alveoli, decreased area of alveoli. In high sight, the lung tissue in normal rats showed complete walls of alveoli, no cells in alveoli; the lung tissue of model groups with hyperoxia showed few red cells, macrophages and AECⅡ in space of alveoli. Compare area, diameter of alveoli and thickness of alveolar septum of model groups with control groups, it was very different (P<0.05).3. VEGF mRNA and protein expressions of control groups detected by real time fluorescent quantitation polymerase chain reaction and Western blotting:VEGF mRNA relative expression in control groups were1.000±0.366,0.931±0.370or0.722±0.372; VEGF protein relative expression in control groups were1.000±0.498,0.787±0.544or0.632±0.289; compared VEGF mRNA and protein expressions between them, it wasn’t different (P>0.05).4. Ang mRNA and protein expressions of control groups detected by real time fluorescent quantitation polymerase chain reaction and Western blotting:Ang mRNA relative expression in control groups were1.000±1.108,0.907±1.019or 0.828±0.462; Ang protein relative expression in control groups were1.000±0.858,0.995±0.871or0.573±0.436; compared Ang mRNA and protein expressions between them, it wasn’t different (P>0.05).5. VEGF mRNA and protein expressions of hyperoxia groups detected by real time fluorescent quantitation polymerase chain reaction and Western blotting:VEGF mRNA relative expression in control groups were0.985±0.403,0.897±0.512or0.239±0.293; VEGF protein relative expression in control groups were0.960±0.619,0.730±0.342or0.358±0.128; compared VEGF mRNA and protein expressions of the7th days between control group and hyperoxia group, it was very different (P<0.05).6. Ang mRNA and protein expressions of hyperoxia groups detected by real time fluorescent quantitation polymerase chain reaction and Western blotting:Ang mRNA relative expression in control groups were1.011±1.131,0.843±0.388or0.327±0.184; Ang protein relative expression in control groups were0.755±0.414,0.711±0.539or0.204±0.068; compared Ang mRNA and protein expressions of the7th days between control group and hyperoxia group, it was very different (P<0.05).Conclusions1. Inhaling hyperoxia(≥95%) for7days persistantly could induced lung injury leading to a model of BPD.2. VEGF and Ang mRNA and protein expression decreased with lung injury by hyperoxia, which showed that VEGF and Ang might take important part in the pathological mechanism of model rats with BPD by hyperoxia through promoting alveoli and vascular development of lung.3. Inhaling hyperoxia persistantly could induced lung injury leading to a model of BPD, and the lung tissue of hyperoxia groups displayed thinner walls of alveoli, simple alveolar structure, fewer and larger alveoli, expanded and shrinked alveoli, decreased area of alveoli, which showed that VEGF and Ang might take an important part in lung development from lung injure of hyperoxia, and they mighty cooperate or restrict with each other..