TGF-β与CTGF在大鼠低压缺氧时右心室心肌纤维化中的作用

Roles of TGF-β and CTGF in hypobaric hypoxia-induced right cardiac ventricular fibrosis in rats

目的探讨转化生长因子β(transforming growth factorβ,TGF-β)、结缔组织生长因子(connective tissue growth factor,CTGF)在低压缺氧条件下发生右心室心肌纤维化与肥大中的作用。方法将50只8周龄雄性SD大鼠[体质量(188.6±19.3)g]随机分为常氧喂养对照组与低压缺氧喂养3、7、14和28 d实验组(n=10),低压缺氧大鼠置于模拟海拔6 000 m的低压舱内饲养。分离右心室,称量法计算右心室肥厚指数。采用荧光定量PCR与免疫印迹法分别检测右心室心肌组织中Ⅰ型胶原、TGF-β和CTGF的mRNA与蛋白表达水平,并分析低压缺氧相同天数TGF-β和CTGF与Ⅰ型胶原表达水平、右心室肥厚指数的相关性。结果与常氧组相比,右心室心肌组织中低压缺氧各组右心室肥厚指数均升高,其中低压缺氧7、14、28 d组右心室肥厚指数显著升高(P<0.05)。与常氧组相比,右心室心肌组织中低压缺氧各组Ⅰ型胶原水平均升高,其中低压缺氧7、14、28 d组水平显著升高(P<0.05)。与常氧组相比,低压缺氧3 d组右心室心肌组织中TGF-β(3.68±0.17)、CTGF(8.73±0.96)蛋白表达量均显著升高(P<0.05),低压缺氧28 d组右心室心肌组织中TGF-β(0.93±0.15)、CTGF(12.62±0.14)蛋白水平均显著升高(P<0.05),而低压缺氧7、14 d组两细胞因子表达量与对照组比较差异无统计学意义(P>0.05)。随低压缺氧时间增加,右心室心肌组织中两生长因子mRNA表达水平与右心室肥厚指数呈显著正相关(P<0.05),与Ⅰ型胶原的mRNA水平也呈显著正相关(P<0.05,低压缺氧28 d组除外);随低压缺氧时间增加,TGF-β的mRNA水平与CTGF的mRNA水平呈显著正相关(P<0.05)。结论随低压缺氧时间增加,右心室心肌组织中TGF-β、CTGF先增加后降低再增加的表达变化,参与了低压缺氧时右心室心肌纤维化、心肌肥大的过程。

Objective To investigate the roles of transforming growth factor β（ TGF-β） and connective tissue growth factor（ CTGF） in right cardiac ventricular fibrosis and hypertrophy under hypobaric hypoxia. Methods A total of 50 SD male rats（ 8 weeks old,weighting 188. 6 ± 19. 3 g） were randomly and equally divided into control group（ normoxia）,and hypobaric hypoxia groups for 3,7,14 and 28 d,respectively. The rats in hypobaric hypoxia groups were housed in a hypobaric chamber simulating high altitude at 6 000 m above sea level for corresponding days. Right ventricle hypertrophy index（ RVHI） was evaluated by the ratio of weight of the right ventricle to the weight of the left ventricle plus interventricular septum. Expression of type Ⅰ collagen（ COL-Ⅰ）,TGF-β and CTGF at mRNA and protein levels in the right ventricle was measured by real-time PCR and Western blotting. The correlation of the duration of hypobaric hypoxia with the expression of TGF-β,CTGF with COL-Ⅰ and RVHI were analyzed. Results Compared with normoxic control group,RVHI was significantly elevated in the hypoxia groups,with those of 7,14 and28 d hypoxia groups more significance（ P〈0. 05）. The mRNA and protein levels of COL-Ⅰ were significantly increased in the right cardiac ventricular of the rats after exposure under hypobaric hypoxia for 7,14 and 28 d（ P〈0. 05）. The protein levels of TGF-β（ 3. 68 ± 0. 17） and CTGF（ 8. 73 ± 0. 96） were significantly increased in the 3 d hypoxia group（ P〈0. 05）,and so were those of TGF-β（ 0. 93 ± 0. 15） and CTGF（ 12. 62 ± 0. 14） under hypoxia for 28 d（ P〈0. 05）. But there were no differences in the expression of the 2 cytokines between the rats under hypoxia for 7 and 14 d（ P〉0. 05）. With the increase of duration of hypobaric hypoxia,the mRNA levels of TGF-β and CTGF were significantly correlated to RVHI（ P〈0. 05） and to COL-ⅠmRNA level except for 28 d hypoxia group（ P〈0. 05）,and the mRNA level of TGF-β was positively associated with that of CTGF（ P〈0. 05）. Conclusion With the increase of the hypoxia duration,the expression of TGF-β is increased and then decreased,while the expression trend of CTGF is increased and then decreased,and the 2 cytokines are involved in the fibrosis and hypertrophy of rat right cardiac ventricule under hypobaric hypoxia exposure.