Background
Adipose-derived stem cells (ASCs) hold a great promise for myocardial infarction, but therapeutic efficacy appears to be limited by their poor survival and engraftment. Integrins are transmembrane proteins known to regulate the biological behaviors of stem cells. Integrin β2 (ITGB2) specifically binds to intercellular cell adhesion molecule-1 (ICAM-1), which is upregulated in infarcted myocardium. ASCs typically express an insufficient amount of ITGB2, and this may limit their homing and engraftment abilities.
Conclusions
ITGB2 overexpression of ASCs enhanced cell viability, proliferation, and migration and induced differentiation in vitro. ITGB2 overexpression significantly improved the survival and engraftment of ASCs into infarcted myocardium via ITGB2/ICAM-1 interaction, augmented angiogenesis, and ultimately improved blood perfusion in infarcted myocardium.
Methods
ASCs were lentivirally transduced to overexpress ITGB2. ITGB2 messenger RNA (mRNA) and protein expression were examined by quantitative polymerase chain reaction (PCR) and western blot. Cell viability, proliferation, and migration were assessed in vitro. Adipogenic and osteogenic differentiation were induced, and the mRNA expressions of specific differentiation markers were quantified by PCR. ICAM-1 expression in the infarcted myocardium was quantified at 3 and 7 days after myocardial infarction. ITGB2-transfected ASCs (ITGB2-ASCs), control ASCs (CTRL-ASCs), and phosphate-buffered saline (PBS) were intramyocardially injected into the peri-infarct region at 3 days after coronary ligation. Four weeks after transplantation, myocardial blood perfusion was measured by 13N·NH3·H2O2 positron emission tomography (PET)/computed tomography (CT). Explanted hearts were then processed for the measurement of capillary density, the quantification of survived green fluorescent protein (GFP+) ASCs, and the identification of ASCs coexpressing angiogenic growth factors.
Results
ICAM-1 expression peaked at 3 days after myocardial infarction and remained elevated over the remote normal myocardium at 7 days after myocardial infarction. ITGB2-ASCs displayed a significant increase in cell viability, proliferation rate, and migration index when compared with CTRL-ASCs. Adipogenic and osteogenic differentiation were more enhanced in ITGB2-ASCs than in CTRL-ASCs. Four weeks after transplantation, surviving GFP+ ASCs were significantly increased, ASCs expressing angiogenic growth factors were more pronounced, capillary density was substantially enlarged, and myocardial blood perfusion was markedly improved in the hearts that received ITGB2-ASCs implantation when compared to those that underwent CTRL-ASC treatment. Conclusions: ITGB2 overexpression of ASCs enhanced cell viability, proliferation, and migration and induced differentiation in vitro. ITGB2 overexpression significantly improved the survival and engraftment of ASCs into infarcted myocardium via ITGB2/ICAM-1 interaction, augmented angiogenesis, and ultimately improved blood perfusion in infarcted myocardium.