Dynamic changes of pneumocyte apoptosis and aspartate-specific cysteine proteases-3 expression in rats subjected to ischemia/reperfusion injury in lung tissue / 中国组织工程研究

ABSTRACT

BACKGROUND: The dynamic changes of pneumocyte apoptosis and aspartate-specific cysteine proteases-3 (caspase-3) expression in lung tissue of rats during the process of lung ischemia/reperfusion (I/R) injury and the possible action mechanisms remain unclear.OBJECTIVE: This study was to observe the dynamic changes of pneumocyte apoptosis and caspase-3 expression in the rat lung tissue during the process of lung I/R injury, and to analyze the role of pneumocyte apoptosis and the possible action mechanism.DESIGN: A randomized controlled animal experiment.SETTING: Emergency Center, First Hospital, Nanjing Medical University.MATERIALS This study was carried out in the Animal Laboratory of the First Hospital of Nanjing Medcial University and Nanjing Center for Radioimmunity between April 2006 and September 2006. Twenty-eight male healthy SD rats of clean grade, with body weight of 250 to 350 g, aged 49 to 76 days, were provided by the Experimental Animal Center of Nanjing Medical University. The involved rats were randomized into experimental group and control group, with 14 rats in each.METHODS: ①Experimental intervention Rats in the experimental group were created into models of lung I/R injury according to the method of Eppinger et al. They were occluded for 45 minutes at the porta of lung (no systolic and diastolic reactions in lung tissue being considered as successful occlusion), and then they were reperfused (recovery of systolic and diastolic function being considered as successful reperfusion); After that, lung tissues were harvested at 3 and 6 hours after lung I/R injury, 7 rats at each time point. Each rat in the control group was subjected to a thoracotony only, but lung tissues were isolated at the same time point by the same method. ②Experimental evaluation Apoptotic cells in the lung tissue were detected with a flow cytometer by Annexin-V-PI staining, and apoptosis rate was calculated. Caspase-3 expression in the lung tissue was observed by immunohistochemical method and image analysis. Wet to dry weight ratio(W/D) of lung tissue of rats in the two groups was calculated; the number of injured pulmonary alveoli at I/R 3 hours/that at I/R 6 hours was calculated for quantitative evaluation of injured lung tissue; Patho-morphological changes of lung tissue were observed by haematoxylin & eosin staining under an optical microscope.MAIN OUTCOME MEASURES: ①Pneumocyte apoptosis rate and caspase-3 expression in the lung tissue. ②W/D of lung tissue and quantitative evaluation of injured lung tissue. ③Patho-morphological changes of lung tissue.RESULTS: Twenty-eight rats were involved in the final analysis, without deletion. ①Pneumocyte apoptosis rates in the experimental group at I/R 3 and 6 hours were significantly increased as compared with control group (P＜0.01). In the experimental group, pneumocyte apoptosis rate was decreased a little at I/R 6 hours than at I/R 3 hours (P＜0.05). ②Caspase-3 expression in the lung tissue of rats of experimental group reached its top at I/R 3 hours, and was decreased a little at I/R 6 hours. At each time point, caspase-3 expression in the experimental group was increased as compared with control group (P＜0.01). ③In the experimental group, the number of injured pulmonary alveoli at I/R 3 hours/that at I/R 6 hours and W/D ratios of lung tissues were significantly increased as compared with control group (P＜0.01). In the experimental group, two ratios at I/R 6 hours were higher than those at I/R 3 hours (P＜0.05).④In the experimental group, the structure of pulmonary alveoli was destructed, collapsed and disappeared; lots of inflammatory cell infiltration was found; Patho-morphological changes of injured lung tissue at I/R 6 hours were severer than those at I/R 3 hours. No obvious changes were found in the control group.CONCLUSION: At the early stage of lung I/R injury, the alteration of caspase-3 maybe activate pneumocyte apoptosis and induce the apoptosis of lung tissue, and thereby leads to lung injury.