Changes Of Some Cytokines And Its Correlation With Myocardial Fibrosis Under Hypobaric Hypoxia

Background and objective:Tissue fibrosis can be induced in a variety of organs, sustainable fibrosis can damage organ and its function, and even failure, which is a serious threat to human health and life. Injury of variable etiology gives rise to complex cascades involving several cell-types and molecular signals, leading to the excessive deposition of extracellular matrix(ECM) that promotes fibrosis and eventually leads to organ failure. Inflammation is the main pathological process to tissue fibrosis, which can cause organ parenchyma cell necrosis, excessive deposition in the extracellular matrix. Cardiac fibrosis is a dynamic process caused by ischemia, hypertrophy, volume- and pressure-overload, aging and diabetes mellitus and so on. Cardiac fibrosis caused by hypobaric hypoxia is a chronic disease, which is characterized with the right ventricle hypertrophy and myocardial fibrosis induced by significant HPH, along with inflammation, release of cytokines, at last, it can lead to cardiac failure and even death. Profibrogentic cytokines can stimulate prodibrogentic cells, such as fibrocyte, fibroblast migration, proliferation, differentiation and secretion of collagen, inflammatory cytokines can recruit white blood cells, regulate cardiac function, repair tissue injure, enhance of inhibit cardiac myocyte viability, they together participate in the progression of cardiac fibrosis. Therefore, we put rats in hypobaric hypoxic chamber to set the HPH model to study the changes of cytokines and profibrogentic cells under the hypobaric hypoxia exposure in the right ventricle and their relationship with cardiac fibrosis. To investigate the interaction between cytokines, profibrogentic cells and fibrosis, it can seek for novel targets of effective prevention and therapy of cardiac fibrosis. Methods: 1. Animals and hypoxiaMale SD rats(n=50) were randomly divided into 0 d(control group), 3 d, 7 d, 14 d, 28 d under hypobaric hypoxia groups. The rats in hypobaric hypoxia group were continuously housed in a hypobaric hypoxia chamber(simulated altitude of 6000 m) for 0 d, 3 d, 7 d, 14 d or 28 d. 2. Cells and hypoxiaH9c2 cells were randomly divided into normobaric normoxia(control group), 6 h, 12 h, 24 h, 48 h under normobaric hypoxia. 3. MethodsThe hemodynamicata such as RVSP and PAP by cardiac catheterization. The RVHI was evaluated by the ratio of weight of the RV over the weight of the LV plus S weight. The structure of the right ventricle was observed by HE staining in the cardia tissue paraffin section. Collagen deposit in right ventricle was observed by masson staining in the cardia tissue paraffin section. The fibrocyte was observed by immunofluorescence in the cardia tissue paraffin section. The expression of CTGF, TGF-β, FPR, Anx A1, CRAMP, COL- Ⅰ in the right ventricle were assayed by RT2-q PCR and western blot. The expression of CTGF, TGF-β, Anx A1, in the H9c2 cells were assayed by RT2-q PCR. Result: 1. Hemodynamic changesPAP and RVSP were significantly increased in hypoxic group(hypoxia 3 d, 7 d, 14 d, and 28 d) than the control group and the difference was statistically significant(P<0.05). 2. The changes of cardiac structureVHI were significantly increased in hypoxic group(hypoxia 7 d, 14 d, and 28 d) than the control group and the difference was statistically significant(P<0.05). Observating by HE staining, with the time of hypobaric hypoxia increasing, structure of right ventricle was destroyed, cardiac muscle was enlarged, and extracellular matrix was increasing. 3. The feature of right ventricle fibrosisObservating by MASSON staining, COL-Ⅰ increasingly deposited in the right ventricle under the hypobaric hypoxia. The RT2-PCR a results showed that, compared with the control group, the m RNA and protein levels of COL- Ⅰ were significantly increased in the right cardiac ventricular of the rats after exposure under hypobaric hypoxia for 7 d, 14 d, 28 d groups,(P<0.05). 4. The changes of fibrocyte in the right ventricle under the hypobaric hypoxiaThe fibrocyte infiltrated into the right ventricle under the hypobaric hypoxia 3 d. 5. Changes of cytokines in the right ventricleThe m RNA and protein levels of TGF-β, CTGF were significantly increased in hypoxia 3 d group(P<0.05). The protein levels of TGF-β, CTGF were significantly upregulated in hypoxia 28 d group(P<0.05); the protein level of CRAMP were significantly increased in hypoxia 7 d, 14 d, 28 d groups(P<0.05); the m RNA and protein level of FPR were significantly upregulated in hypoxia 3 d, 28 d groups(P<0.05); the protein level of Anx A1 were significantly upregulated in hypoxia 3 d, 7 d, 14 d groups(P<0.05). 6. The expression of cytokines in the H9c2 cellThe m RNA levels of TGF-β was significantly increased in normobaric hypoxia 6 h, 12 h(P<0.05). The m RNA levels of CTGF was significantly increased in normobaric hypoxia 12 h, 24 h(P<0.05). The m RNA levels of Anx A1 was significantly increased in normobaric hypoxia 6 h(P<0.05). 7. The correlation ship between TGF-β,CTGF,COL-Ⅰand RVHIThe relationship between COL-Ⅰand RVHI was positive in 0d, hypoxia 3 d, 7 d, 14 d, 28 d groups(P<0.05); the relationship between TGF-β, CTGF and COL-Ⅰ was positive in hypoxia 3 d, 7 d, 14 d groups(P<0.05); the relationship between TGF-β, CTGF and RVHI was positive in hypoxia 3 d, 7 d, 14 d,28 d groups(P<0.05). ConclusionThe early time of hypobaric hypoxia time, the right ventricle fibrosis and the infiltration of fibrocytes are increased; along the hypobaric hypoxia, the fibrosis is increasing; the early time of hypobaric hypoxia time, the expression of TGF-β, Anx A1 and CTGF is increased, then dropped down, at last CTGF is rebounded up; the expression of CRAMP is increasing with the hypoxia time. fibrocytes, TGF- β, CTGF are expected to become the keys of the anoxic heart disease diagnosis.