The influence of bone marrow-derived multipotent stromal cells on myocardial scar healing in experimental myocardial infarction L. Kakturskiy * , T. Fatkhudinov * Institute of Human Morphology, Central Laboratory of Pathology, Moscow, Russia Objective: Previous studies have shown the benefits of intracoronary infusion of bone marrow-derived multipotent stromal cells (BM-MSCs) in heart disease. Our aim was to study engraftment, differentiation of BM-MSCs and its role in myocardial reparation. Method: Acute myocardial ischemia was produced by transient occlusion (total of 20 min) of the proximal left anterior descending coronary artery and followed by reperfusion. BM-MSCs were isolated, expanded by standard and labeled with PKH26 (Sigma). Cells were CD90 and CD105 positive. 30 days after occlusion during cross-clamping of aorta the cells were administered into the cavity of the left ventricle at the concentration 5×106 in saline solution. In 1 day, 2, 4 and 6 weeks after transplantation the labeled cells were detected in the cryosections and heart morphometry was performed. Results: BM-MSCs were detected only in the scar tissue and had a fibroblast-like phenotype. They neither differentiated into cardiomyocytes nor into the cells of blood vessels. In 4 weeks after transplantation the scar thickness was higher in the group with cell transplantation (p<0.001). Conclusion: Engrafted BM-MSCs promote myocardial fibrosis only in the scar, but not in the perifocal myocardium, provided strengthening of the scar, remodelling of outflow tract, and improvements the myocardial function.