高氧致慢性肺疾病早产鼠肺组织CDK4 p21的表达及意义

目的：早产儿慢性肺疾病（CLD）的发病机制目前研究还不十分清楚，但CLD的最终病理变化与肺细胞增殖有关。该文采用高氧诱导早产鼠CLD模型为对象，探讨CDK4和p21基因动态表达与肺细胞增殖调控的关系。方法：高浓度氧致早产鼠CLD模型（实验组）和正常对照组各40例为研究对象，每组分别于实验后的1，3，7，14和21 d随机选取8只大鼠处死, 取出肺组织,常规制成5 μm切片。检测观察：①肺组织形态学；②肺组织纤维化评分；③采用免疫组化检测肺组织内PCNA表达；④采用原位杂交检测肺组织CDK4 mRNA和p21 mRNA的表达。结果：两组肺组织细胞PCNA指数：与对照组比较，实验组1 d，3 d PCNA表达均减弱（P﹤0.05），7 d开始表达增强（P＜0.01）, 14 d和21 d明显高于对照组（P＜0.01）。两组肺组织细胞CDK4 mRNA表达强度： 从7 d开始实验组高于对照组（P﹤0.05）, 14 d，21 d明显高于对照组（P﹤0.01）。两组肺组织细胞p21 mRNA表达强度：实验组1 d，3 d表达明显高于对照组（P﹤0.01）, 7 d 后持续下降, 但也高于对照组（P﹤0.05）。7~21 d肺组织细胞CDK4 mRNA，p21 mRNA 表达分别与PCNA呈显著正、负相关（r分别为0.83和-0.81，P﹤0.05）。结论：高氧可诱导早产鼠肺细胞增殖。肺组织细胞CDK4基因的过度表达、p21基因的表达下降,可能是高氧诱导肺细胞增殖的机制之一。［中国当代儿科杂志，2007，9（6）：595-600］

Expression and roles of CDK4 and p21 in lung tissues of premature rats with hyperoxia-induced chronic lung disease

OBJECTIVE: The pathogenic mechanisms of chronic lung disease (CLD) of premature infants are not fully understood. Its final pathological changes have been shown to relate with lung cell proliferation. The aim of the study was to explore the relationship of the expression of cyclin dependent kinase 4 (CDK4) mRNA and cyclin dependent kinase inhibitor (CDKI) p21 mRNA with lung cell proliferation. METHODS: Eighty premature rats were randomly assigned to a hyperoxia group and a control group (n=40 each). The hyperoxia group was exposed to high concentration of oxygen (FiO2 >0.90 and developed CLD. The control group was exposed to room air (FiO2 =0.21). The rats were randomly subdivided into groups sacrificed at 1, 3, 7, 14 and 21 days of exposure. Lung tissues were collected and made into 5 microm sections. Expression of proliferating cell nuclear antigen (PCNA) in lung tissues was detected by immunohistochemistry. Dynamic expression of CDK4 mRNA and p21 mRNA were detected by in situ hybridization. Lung histomorphology and fibrosis were observed by microscopy. RESULTS: Expression of PCNA and CDK4 mRNA of lung cells in the hyperoxia group increased significantly after 7 days of exposure, and further increased after 14 and 21 days compared with controls. p21 mRNA expression in the hyperoxia group significantly increased after 1 and 3 days of exposure. After 7 days, p21 mRNA expression progressively decreased, but remained at a higher level than control through 21 days of exposure. PCNA expression was positively correlated to CDK4 mRNA expression (r=0.83, P < 0.05) and negatively correlated to p21 mRNA expression (r=-0.81, P < 0.05) in the hyperoxia group between 7 and 21 days of exposure. CONCLUSIONS: Hyperoxia can induce lung cell proliferation in premature rats. The over-expression of CDK4 gene and the decreased expression of p21 gene in lung tissues may be associated with lung cell proliferation induced by hyperoxia.