| Even use current optimal treatment, ischemic heart disease is still one of the leading cause of death all over the world. Because of the lack of effective therapies,myocardial ischaemia/reperfusion(I/R) injury remains one of the major problem in medical today. The best way to treat myocardial ischaemia disease now is rapid reperfusion, which could reduce myocardial infarction, cardiomyocyte apoptosis and finally improve heart contractile dysfunction. Reduction in infarct size by reperfusion in patients with myocardial infarction was also quickly used in clinical practise;however, reperfusion could also induce potential secondary injury, such as overproduction of reactive oxygen species(ROS), autophagy dysfunction,mitochondrial stress and over-loading of calcium in the reperfusion period.Unbalanced and high steady-state levels of reactive oxygen and nitrogen species may induce contractile dysfunction and cell death. Oxidative stress resulting from the overload of toxic ROS could also induce various modifications of proteins, DNA, and lipids that involved in cell proliferation, growth arrest, apoptosis or necrosis. In our previous study, we have proved that the b FGF treatment immediately after reperfusion could protected the heart from myocardial I/R injuries. However, the molecular mechanism of b FGF in the treatment of myocardial injury in the early-stage after reperfusion is still unclear. So, in our president study, we will try to investigate the molecular mechanism of b FGF treatment in the protection of myocardial I/R injuries.After the above study, we found that FGF could only work well in shortterm. To achieve more effectiveness in growth factor therapies in long run, we developed a coacervate protein delivery platform that consists of a polycation and heparin to deliver heparin-binding proteins. In vitro experiments revealed several advantages of this platform including high affinity to heparin-binding growth factors, ability to control their release in a steady fashion and well-maintained bioactivity of the released factors. Subcutaneous injection of FGF coacervate induced substantial and mature vessel formation and exhibited higher bioactivity than naked FGF. These laid the groundwork for the current study on the effectiveness of FGF coacervate in a mouse model that mimicked human acute myocardial infarction(MI). The hypothesisof this study was that high bioactivity of FGF1 coacervate can effectively reduce the impact of ischemic injury and improve cardiac function post-MI.In our present study, we choose ischemic heart disease animal model, at first two parts of our studies, we investigated the role of b FGF in the recovery from myocardial I/R injuries, preliminary elucidates the possible mechanism of b FGF in repairing oxidative stress-induced cardiomyocyte apoptosis and regulating autophagy and ubiquitinated protein accumulation induced by myocardial I/R. Besides the mechanism study, we also developed a coacervate protein delivery platform that consists of a polycation and heparin to deliver FGF proteins. Specifically includes the following three points:(1) We demonstrate that b FGF treatment could inhibit the myocardial I/R induced endoplasmic reticulum(ER) stress and mitochondrial dysfunction. In vitro,b FGF could protect H9C2 cell by inhibiting the mitochondrial dysfunction and ER stress response associate proteins induced by TBHP. And all these effects of b FGF are related to the activation of two important signaling pathways, PI3K/Akt and ERK1/2.However, when we use Akt and ERK1/2 pathways specific inhibitors, LY294002 and PD98059, both of them partially abolished the protective effect of b FGF. Overall, our results shown that the cardioprotective role of b FGF related to the inhibitation of ER stress and mitochondrial dysfunction in ischemic reperfusion models and TBHP-induced H9C2 cell injury; furthermore, these effects through the activation of the Akt and ERK1/2 signaling pathways.(2) The cardioprotective effect of b FGF is related to the inhibition of LC3 II protein expression. On another hand, b FGF improve the clearance of Ub by p62 and increases the survival rate of H9C2 cells. Moreover, Si RNA p62 partially blocks the clearance of Ub and decrease the anti-apoptosis effect of b FGF. An sh RNA against the autophagic machinery Atg7 increased the survival of H9C2 cells. Furthermore,b FGF could activates the downstream signaling of the PI3K/Akt/m TOR pathway.These results shown that the role of cardioprotective role of b FGF is related to the inhibition of excessive autophagy and enhancement of ubiquitinated protein clearance through the activation of PI3K/Akt/m TOR signaling pathway. In conclusion, our research shown a new trend for b FGF drug development in heart diseases and autophagy as a target for heart disease treatment.(3) Emerging evidence supports the beneficial effect of FGF on heart diseases,but its application has been hindered by the short half-life of the free protein. Toachieve effective growth factor delivery, we designed an injectable coacervate which could protects growth factors and preserves their bioactivities. In this study, acute myocardial infarction(AMI) model was established and the cardioprotective effect of the FGF1 coacervate was investigated. Histological examination revealed that FGF1 coacervate reduced inflammation and fibrosis post-MI, significantly increased the proliferation of endothelial and mural cells, and resulted in stable capillaries and arterioles. Besides these effects, FGF1 coacervate improved the proliferation of cardiac stem cells at 6 weeks post-MI. On the contrary, identical dosage of free FGF1 showed no statistical difference from saline group. As shown in the echocardiographic results, FGF1 coacervate inhibited ventricular dilation and preserved cardiac contractibility more than free FGF1 and saline group within the 6-week duration of the experiments. In conclusion, our results showed that injection of FGF1 coacervate attenuated the injury caused by MI and may be a potential new therapy for myocardial infarction in long run. |
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