Rationale: Adipose tissue-derived mesenchymal stromal cells (AT-MSCs) may contribute repairing ischemic cardiovascular tissue. The engraftment and survival of transplanted cells in the harmful microenvironment of host tissue may be improved by combining stem cells with scaffolds to delay apoptosis and enhance their regenerative properties.
Objectives: We examined whether poly (lactide-co-glycolide) (PLGA) microspheres functionalized with vascular endothelial growth factor (VEGF) enhance survival, growth, and differentiation of AT-MSCs, and the therapeutic efficacy of transplanted AT-MSCs conjugated with VEGF-microspheres or injection of conditioned medium from AT-MSCs in a murine model of acute myocardial infarction (AMI).
Methods: Non-functionalized (empty) or VEGF-releasing microspheres were produced and coated with murine AT-MSCs. Twelve month-old male C57BL/6 mice underwent coronary artery ligation, followed by randomization into 7 groups (n=5/group): Sham operation, AMI control (saline 20 μl), intramyocardial injection with AT-MSCs only (2.5x105 cells/20 μl), or concentrated medium from AT-MSCs (CM, 20 μl), or AT-MSCs (2.5x105 cells/20 μl) conjugated with empty microspheres or VEGF-releasing microspheres.
Results: Growth-curve and differentiation assays showed that VEGF-releasing microspheres do not impact proliferation or osteogenic and adipogenic differentiation of AT-MSCs. Conversely, H2O2-induced apoptosis was inhibited in AT-MSCs conjugated with VEGF-releasing microspheres, and this effect was dependent on the VEGF/Akt axis, since reverted by pre-incubation with the Akt inhibitor LY294002 or an anti-VEGF receptor antibody. In a Matrigel assay, AT-MSCs conjugated with VEGF-releasing microspheres were more pro-angiogenic than AT-MSCs alone. Finally, when compared with AT-MSCs alone, AT-MSCs conjugated with VEGF-releasing microspheres decreased the area of fibrosis and increased myogenic marker expression, arteriogenesis, number of cardiac-resident c-Kit positive cells and fractional shortening when transplanted into the infarcted hearts of C57 mice, effects that were paralleled by the injection of CM (p<0.01 vs AMI control by ANOVA) .
Conclusions: The delivery of the AT-MSCs conjugated with VEGF-releasing microspheres or injection of CM may have therapeutic applications for enhancing arteriogenesis and survival of AT-MSCs and for improving left ventricular function after AMI.