Tracking Long-Term Survival of Intramyocardially Delivered Human Adipose Tissue-Derived Stem Cells Using Bioluminescence Imaging

Transplantation of a regenerative cell population derived from human subcutaneous adipose tissue (hASCs) for cardiac regeneration represents a promising therapy due to the capacity of these cells for proliferation and differentiation. Understanding the fate of injected hASCs would help to understand how hASCs work in vivo. The aim of this study was to track the long-term fate, including survival, differentiation, proliferation, apoptosis, migration, and growth factor secretion of intramyocardially injected hASCs following experimental acute myocardial infarction in an immunodeficient mouse model. Myocardial infarction was experimentally induced in severe combined immunodeficient mice by permanent ligation of the left anterior descending coronary artery. Lentivirally labeled hASCs (5 x 10(5); expressing green fluorescence protein [GFP] and luciferase) were injected into the peri-infarct region. Colony formation, growth kinetics, and differentiation of transduced hASCs were analyzed in vitro and compared to those of untransduced hASCs. The survival and migration of injected hASCs were tracked by luciferase-based bioluminescence imaging for 10 weeks. Immunofluorescence and terminal deoxynucleotidyl transferase dUTP nick end labeling staining were used to assess differentiation, proliferation, growth factor expression, or apoptosis of grafted hASCs in infarcted hearts and potential distribution to other tissues. Lentivirus transduction and GFP and luciferase expression did not influence proliferation or differentiation of hASCs. Bioluminescence imaging demonstrated that injected hASCs survived in infarcted hearts during the follow-up of 10 weeks. Immunofluorescence confirmed that hASCs engrafted in ischemic hearts expressed bFGF and IGF-1, and did not migrate into other organs. Of all engrafted hASCs, 3.5% differentiated into cardiomyocytes or endothelial cells. Other cells maintained their proliferative potential or underwent apoptosis. Luciferase-based bioluminescence imaging allows long-term tracking of intramyocardially injected hASCs in living mice. The hASCs might enhance function of injured hearts through long-term engraftment, growth factor secretion, and transdifferentiation to cardiomyocytes and endothelial cells.