| Background:Despite advances in medical and surgical procedures,heart failureremains a leading cause of cardiovascular morbidity and mortality.Although myocytemitosis and the presence of cardiac precursor cells in adult hearts have recently beenreported,the death of large numbers of cardiomyocytes results in the development ofheart failure.Many researchers have investigated cell transplantation and consideredit as an alternative treatment for heart disease.A variety of cell types have beenproposed as useful candidates,such as skeletal muscle satellite cells,fetalcardiomyocytes,embryonic stem cells,and so on.It is now accepted that an adherentpopulation of cells isolated from bone marrow is multipotential progenitor cells,which can differentiate into muscle,cartilage,bone and fat.The repair of onedamaged heart would likely require regenerated myocardium,new blood vessels,andelectrical and mechanical coupling of the restored tissue.Dramatic advances havebeen made in the clinical application of BM-MNCs in heart failure of ischemic origin,however,little information is available about the therapeutic potential of BM-MNCsfor chronic heart failure of nonischemic origin and the beneficial effects are mediatedby their differentiation into cardiomyocytes and vascular cells and by their supplyingangiogenic are still a debated object.Objectives:The heart failure model was induced by rapid right ventricular pacing,then we observed the feasibility of which BM-MNCs suspension was injected intomyocardium.After a month,the cardiac function was evaluated to observe ifBM-MNCs can improve LVEF.The cardiac muscle specimen was detected byimmunohistochemistry to observe if BM-MNCs can differentiate into cardiomyocytesand vascular endothelial cells,and improve secretion ofVEGF,bFGF and AKt.Methods:16 healthy adult mongrel dogs of either sex,weighing between 15 and 20kg each,were divided into two groups randomly,and model of heart failure wasproduced by rapid right ventricular pacing.A pacemaker wire was introduced into theright jugular vein and positioned in the right ventricle,and transthoracic restechocardiography was performed after 2-4 weeks of rapid right ventricular pacing.ifthe left ventricular ejection fraction (LVEF) is obviously lower,we confirmed that themodel of heart failure was established.Bone marrow aspirates were passed through adensity gradient to eliminate unwanted cell types,then the remaining purifiedBM-MNCs population was labeled with the cross-linkable membrane dye CM-DiIand were delivered via direct surgical intramyocardial injection (4-5 sites) within the cardiac apex.In the control group (n=6),the animals were received saline injectionsin the same manner.Before injection,the cells were thoroughly washed andresuspended in a 1-ml volume of saline (3×10~7-1×10~8/ml).After 4 weeks oftransplantation,echocardiography and Swan-Ganz were performed to observe thecardiac function.The Dogs' hearts were exposed by median sternotomy and quicklyremoved,and sliced in a bread-loaf manner into 4 transverse sections from apex tobase.Each section was separated into anterior,anterolateral,lateral,poster lateral,andposterior LV.Each section thickness was sliced in half;one half was frozen in liquidnitrogen,and the remainder was fixed in 10% formaldehyde.The effect of stem celltransplantation on angiogenesis was evaluated in paraffin-embedded sections bycounting the number of vessels in different wall sections (5 sections per heart)immunostained for the endothelial cell marker factorⅧ.The number of vessels wascounted under a light microscope in 5 random fields.The survival of engrafted cellswas identified by DiI positivecells in frozen sections made from the hearts.Potentialtransformation to cardiac-like cells from engrafted BM-MNCs was verified byantibody immunostaining for cardiac troponin T.All values were expressed asmean±SEM.All analyses were performed with SPSS 11.5 software.Results:1.The BM-MNCs that were implanted into the canine model of heartfailure showed clear red fluorescence.2.After 4 weeks of transplantation,echocardiography and Swan-Ganz showed that cardiac function in the transplantationgroup improved significantly (LVEF,37.29±6.75 vs.42.14±2.79,P＜0.05;SV,9.43±1.90 vs.13.28±1.80,P＜0.01;LVPWd,5.54±1.02 vs.6.12±1.43,P＜0.01;PAP,19.86±2.34 vs.16.29±1.90,P＜0.05;PCWP,14.71±3.15 vs.12.29±1.89,P＜0.05;CO,2.66±0.47 vs.2.95±0.40,P＜0.05).3.The number of vessels immunostained for theendothelial cell marker factorⅧand a-SMA was higer in the transplantation groupthan in the control group (vWF,7.29±2.03 vs.6.04±2.07,P=0.040;a-SMA,13.25±2.88 vs.10.95±3.63,P=0.033).4.CM-DiI labeled BM-MNCs were mainlylocated within the cardiac apex,and cTnT were positive immunofluorescently in theimplanted cardiac muscles.5.Compared with the control group,the expression ofVEGF,bFGF and AKt mRNA was increased in the transplantation group (VEGF,1.06±0.43 vs.0.32±0.18,P=0.000;bFGF,1.25±1.09 vs.0.50±0.53,P=0.040;1.15±0.55 vs.0.67±0.16,P=0.022).Conclusion:We demonstrate in this study that BM-MNCs transplantation in acanine model of heart failure leads to (1) induction of myogenesis and angiogenesis, (2) differentiation of transplanted MSCs into cardiomyocytes and vascular endothelialcells,(3) secretion of large amounts of VEGF,bFGF and AKt,and (4) improvementof cardiac function and inhibition of ventricular remodeling. |
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