Myocardium Elastic Modulus Modulates Angiogenesis In Cardiac Hypertrophy Via Integrin ?1/VEGF Signaling Pathway

Objective:Cardiac hypertrophy is an adaptive process response to physiological and pathological stress.Biomechanical stress is one of the most important triggers of cardiac hypertrophy,while the relative of stress on tissues is dependent on elastic modulus.Nevertheless,the way elastic modulus participates in cardiac hypertrophy and remodeling is not quite clear.In our research,we will try to find the correlation between the cardiac elastic modulus and angiogenesis.Methods:We will establish the pressure-overload model via transaortic constriction(TAC)and try to the correlation between cardiac elastic modulus and angiogenesis in hypertrophy by atomic force microscope(AFM),CD31 immunohistologic staining and Vevo2100 ultrasound.Meanwhile,we will make different elasticity cell culturing medium exam the ability of VEGF Paracrine in H9c2 cardiac myoblasts,which affects the migrate and tubulate ability of cardiac microvascular endothelial cells in angiogenesis,and try to find its mechanism.The test was tripled,data were expressed as means ± SEM.Student's t-test or two-way ANOVA was used to assess the statistical differences.SPSS 19.0 was used for analysis,P<0.05 was considered statistically significant.Results:Echocardiography analysis showed transaortic constriction significantly increased IVSd and LVAWd in 14 and 28 days,and WGA staining showed the myocytes cross-sectional area also increased,which indicated that we established the pressure-overload induced cardiac hypertrophy successfully.Atomic force microscope analysis showed an increasing of myocardium Elastic Modulus in 14 and 28 days after TAC,which had a correlation with the increased density of CD31+cells.Meanwhile,we will make cell-culturing microenvironment of different elasticity according to Pelham in vitro.We found the medium of H9c2 myoblasts who cultured on high EM gels had the ability to increase the migration and tabulation of cardiac microvascular endothelial cells,and it can be inhibited by VEGF monoclone antibody.Western-blot analysis showed VEGF increased in the medium of high-EM gels cultured H9c2 cells.Further analysis showed high-EM gels would increase the protein expression of Integrin beta 1,who will promote VEGF expression by assessing the activation of PI3K/AKT/HIF1? pathway.In addition,we knocked down the Integrin beta 1 expression with the help of siRNA,and found the increasing of VEGF expression and phosphorylation level of PI3K/AKT induced by high-EM culture could also be inhibited in H9c2 myoblasts.Conclusion:Cardiac elastic modulus increasing during the development of pressure-overload induced cardiac hypertrophy,and it has a positive correlation with angiogenesis;In addition,increasing of myocardial tissue elastic modulus may promote VEGF paracrine through Integrin PI3K/AKT/HIF1 alpha pathway in H9c2 cells.