Distinct Results Under Different Pressure Overload In Neonatal Mice

【Background and objective】Chronic heart failure is a clinical syndrome of organic cardiovascular disease caused by different causes,which is closely associated with cardiac hypertrophy and fibrosis driven by pressure overload.Heart regeneration can repair the damaged myocardium and is deem as a promising treatment for heart failure.The heart regeneration after apical resection and myocardial infarction in neonatal mice has been studied for years.However,the response of neonatal mice heart to pressure overload was rarely mentioned.In this research,we investigated heart function and myocardial response under different pressure overload in neonatal mice,which provide new insights into the heart regeneration and pressure overload.【Method】1.Heart pressure overload was induced in neonatal mice through a transverse aortic constriction(TAC)with different-gauge needles.The changes in the growth rate and mortality of mice after surgery were recorded.2.Echocardiogram was used to measure EF,FS,LVEDD,LVESD and evaluate the change of heart function and structure.3.Immunofluorescence was used to detect pH3,Ki67,CD31,Brd U,and evaluate the degree of cardiomyocyte proliferation and angiogenesis.4.WGA,TUNEL,Masson staining were used to evaluate the degree of cardiac hypertrophy,apoptosis and fibrosis.5.Transmission electron microscope was used to observe the structural changes of myocardial fibers and mitochondria.6.RT-qPCR was used to detect the expression of fibrosis-related m RNA Timp1,Fn1,MMP9,COL1A1,cardiac hypertrophy-related m RNA Myh7,BNP,Acta1,Fhl1 and house-keeping gene β-actin in heart tissue.7.Western blotting was used to detect the expression of extracellular matrix components COL1A1,COL3,MMP9,fibrosis signal transduction pathway TGF-β,Smad3,p-Smad3 and house-keeping gene β-tubulin in heart tissue.【Results】1.As the degree of pressure overload increases,the growth rate of neonatal mice slows down.Mild pressure overload does not increase mortality,while moderate pressure overload significantly increases mortality.Severe pressure overload causes a large number of neonatal mice to die in the early postoperative period.2.Mild pressure overload does not affect heart function,while moderate pressure overload significantly impairs heart function.3.Mild pressure overload stimulates cardiomyocyte proliferation and angiogenesis,while moderate pressure overload has the opposite effect.4.Mild pressure overload induces adaptive hypertrophy,while moderate pressure overload induces pathological hypertrophy.5.Moderate pressure overload damages the structure of sarcomere and mitochondria.6.Moderate pressure overload leads to cardiac fibrosis via activating TGF-β/Smad3 signaling pathway.【Conclusion】In neonatal mice,cardiomyocyte can be effectively stimulated to proliferate under moderate pressure overload with a preserved heart function.