Injection Of Bone Marrow Mesenchymal Stem Cells In The Borderline Area Of Infarcted Myocardium: Heart Status And Cell Distribution

Objective:Stem cell therapy has emerged as a promising approach for the treatment of myocardial infarction(MI).The transplanted cell's retention, migration is affected not only by the transplanted approach,but also by the heart status.This preclinical study was to test the intramyocardially injected bone marrow(BM) mesenchymal stem cells(MSCs) cell distribution in different heart statues(arresting or beating) in a porcine myocardial infarction (MI) model.Methods:In vitro study:BM was aspirated from the iliac crest of male swine.Bone marrow MSCs were expanded and incubated with SPIO for 48 hours.The labeling efficiency was tested through Prussian blue staining,and cells viability was tested through Trypan blue rejection method.In vivo study:An occlusive angioplasty balloon was advanced into the proximal left anterior descending coronary artery via percutaneous approach.Acute MI was induced by inflating the balloon for 90 minutes followed by artery perfusion.1 week after creation of MI in female swine,the survivals were randomly divided into 4 groups.Cardiopulmonary bypass was set up to arrest heart,and then labeled cells(1×10~8) were intramyocardially injected into the borderline of infracted zone in Group 1(n=6).Same volumes of cells were grafted in the beating heart in Group 2(n=6).In Group 3 and 4,the same volume of saline was injected in either arresting or beating heart(n=6 respectively).3 days later,cell distribution was assessed by T2~* change with magnetic resonance imaging and sex-determining region on Y-chromosome (SRY) with quantitive polymerase chain reaction.The interested segment of heart,liver,spleen,lung,and kidney tissues were collected for Prussian Blue Staining.Results:In vitro study:Prussian blue staining of SPIO-labeled MSCs revealed the presence of numerous blue staining iron-containing vesicles or particles in the cytoplasm of nearly every cell.The labeling efficiency reached approximately 100%.More than 95%labeled cells were not stained with Trypan Blue.In vivo study:The cells were identified in heart,spleen,lung and liver.Most of injected cells were localized in the myocardium in Group 1 and 2,however, the amount of detained cells was much higher in Group 1(T2~* change: 22.3±2.2 versus 17.00±0.84;SRY gene:0.150±0.062 versus 0.072±0.003). The injected sites containing labeled cells could all be detected through MRI and were confirmed on pathology.Conclusion:Even after intramyocardially injection,many cells migrated to extracardiac organs especially to the spleen.Our results indicated injection in the arresting heart could favor more cells be retained in myocardium and thus it was an optimal approach to deliver MSCs during open chest surgery. Backgroud:Transcorocnary infusion of the therapeutic stem cells is the most popular delivery approach of cell transplantation to improve cardiac function for the injured heart,but few data is reported about the retention,distribution, and migration of the implanted cells.Systemic distribution of bone marrow stromal cells(BMSCs) after intracoronary infusion(ICI) and the role of cardiopulmonary bypass(CPB) in cell distribution still remain unclear.This study was designed o analyze the cell distribution after ICI in variations of heart status in a swine myocardial infarction(MI) model.Methods:After inducing an MI,iron oxide labeled male cells(1×10~8) were infused through the coronary artery of the beating swine heart in Group 1.In group 2,CPB was set up and then the same volume of cells was infused after cadioplegic arrest.In Group 3 and 4,the animals underwent either beating or arrested ICI with the same volume of saline.Three days later,cell distribution was assessed by T2~* change with magnetic resonance imaging and sex-determining region on Y-chromosome with quantitive polymerase chain reaction. Results:Only a few transplanted cells were localized in the heart and no difference was found between groups 1 and 2.The majority of BMSCs would be trapped in extracardial organs,and more cells resided in the spleen in arrested heart status.The percentage of the apoptotic cells in the implanted cells in Group 1 was lower than that in Group 2.Expression of the muscle-specific markers wasn't observed at 3 days in Prussian blue-positive cells.Conclusion:The majority of BMSCs transplanted by ICI would be entrapped by the extracardial organs.The arrested heart with CPB during ICI does not favor more cells retention in the injured myocardium.The optimal approach of delivery of BMSCs still needs further investigation.