Relationships of Smad2,Smad7 and transforming growth factor-β1 proteins in the lung tissues with airway remodeling in asthmatic mice
Objective To observe the expressions of Smad2,Smad7 and transforming growth factor-β1(TGF-β1)in the lung tissues of asthmatic mice during airway remodeling,and to analyze the relationships of Smad2,Smad7 and TGF-β1 with airway remodeling.Methods Forty-eight SPF BALB/C female mice were randomly divided into model group and control group,with 24 mice in each group.The mice in model group were sensitized by intraperitoneal injection of suspension containing 20 μg ovalbumin and 100 μg aluminum hydroxide by day 0 and 14 of the experiment,the asthma models were induced by inhaling 2.5％ovalbumin for 30 min once every other day by day 21.The mice in control group were given an equivalent volume of normal saline.Within 24 h after 2,4 and 8 weeks of provocation test,8 mice in each group were killed randomly,and the left lung tissues and main bronchus were obtained for histopathological examination by HE staining to measure the morphological parameters of airway such as total wall area(WAt)/basement membrane perimeter(Pbm),inner wall area(WAi)/Pbm and smooth muscle wall area(WAm)/Pbm.The expressions of Smad2,Smad7 and TGF-β1 proteins in the lung tissues were detected by immunohistochemical SP method.The optical density(OD)value was detected.Pearson correlation analysis was done to assess the correlations of the OD values of Smad2,Smad7 and TGF-β1 proteins with WAt/Pbm and WAm/Pbm in model group.Results(1)Within 24 h after 2,4 and 8 weeks of provocation test in model group,there were a large number of inflammatory cells infiltrated in the bronchial wall and around the blood vessels,some incompletely exfoliated epithelial cells in the bronchioles,proliferated goblet cells complicated with mucus secretion,proliferated airway smooth muscle cells,and thickened basement membrane;and the proliferation of airway smooth muscle cells and thickening of basement membrane were more obvious with the prolonging of provocation test.(2)After 2,4 and 8 weeks of provocation test,the WAt/Pbm values were greater in model group[(71.8±15.2),(68.8±10.2),(101.1±6.9)μm2/μm]than those in control group[(44.9±6.1),(39.9±4.1),(45.7±8.3)μm2/μm](P＜0.05),and WAi/Pbm values showed no significant differences between two groups(P＞0.05).The WAm/Pbm values after 4 and 8 weeks were greater in model group[(8.2±1.4),(10.9± 2.9)μm2/μm]than those in control group[(6.2±1.0),(6.0±1.4)μmz/μm](t=3.291,P=0.005;t=4.302,P=0.001).There was no significant difference in the WAm/Pbm value after 2 weeks between model group[(7.2± 1.1)μm2/μm]and control group[(6.6±0.6)μm2/μm](P＞0.05).The WAt/Pbm and WAm/Pbm values were greater after 8 weeks than those after 2 and 4 weeks in model group(P＜0.05),and showed no significant differences after 2 weeks compared with those after 4 weeks(P＞0.05).The WAi/Pbm showed no significant difference in model group after 2,4 and 8 weeks(P＞0.05).All WAt/Pbm,WAi/Pbm and WAm/Pbm values showed no significant differences in control group after 2,4 and 8 weeks(P＞0.05).(3)After 2,4 and 8 weeks,the OD values of Smad2 protein were higher in model group(0.24±0.01,0.25±0.01,0.26±0.01)than those in control group(0.21±0.01,0.21±0.02,0.20±0.01)(P＜0.05).The OD values of Smad7 protein were lower in model group(0.19±0.01,0.17±0.01,0.15±0.01)than those in control group(0.28±0.06,0.29±0.04,0.29±0.02)(P＜0.05).The OD values of TGF-β1 protein after 4 and 8 weeks were higher in model group(0.17±0.01,0.16±0.01)than those in control group(0.14±0.01,0.14±0.01)(P＜0.05).There was no significant difference in the OD value after 2 weeks between model group(0.15±0.02)and control group(0.14±0.01)(P＞0.05).The OD value of Smad2 protein in model group was higher at 8 weeks than that at 2 and 4 weeks(P＜0.05),and showed no significant difference after 2 weeks compared with that after 4 weeks(P＞0.05).The OD value of Smad7 protein in model group decreased sequentially after 2,4 and 8 weeks(P＜0.05).There were no significant differences in the OD value of TGF-β1 protein in model group and in the OD values of Smad2,Smad7 and TGF-β1 proteins in control group after 2,4 and 8 weeks(P＞0.05).(4)After 2,4 and 8 weeks,the OD values of Smad2 and TGF-β1 proteins were positively correlated with WAt/Pbm and WAm/Pbm in model group(P＜0.05),and the OD value of Smad7 protein was negatively correlated with WAt/Pbm and WAm/Pbm(P＜0.05).Conclusions The increased expressions of Smad2 and TGF-β1 and decreased expression of Smad7 participate in the airway remodeling in asthmatic mice.With the prolonging of provocation test,the expressions of Smad2 and Smad7 change dynamically,and TGF-β1 expression has no obvious change.
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