Abstract 3613: Mesenchymal Stem Cells Co-overexpressing Akt and Ang-1 Enhance Angiogenesis via Synergistic Expression of HIF-1α Dependent Angiogenic Factors
Background: We have previously shown that transplantation of mesenchymal stem cells (MSCs) co-overexpressing Angiopoietin-1 (Ang-1) and Akt prevented cell apoptosis, enhanced angiogenesis and improved heart function. The current study elucidated the underlying mechanism.
Methods and Results: MSCs were adenovirally transduced with genes encoding for green fluorescent protein (group-1) as control, Akt (group-2), Ang-1 (group-3) and both Akt and Ang-1 (group-4). After 48 hours of transduction, the cell lysate and conditioned medium from each group was collected. Simultaneous transduction of Akt and Ang-1 in group-4 synergistically enhanced transgenes overexpression besides showing significantly higher expression of HIF-1α, HO-1 and VEGFR2 as compared with group-2 and 3. Western blot showed that HIF-1α specific RNA interference markedly reduced HO-1 and VEGFR2 protein expression in group-4. Paracrine release of VEGF (pg/ml) in conditioned medium (CM) from group-4 MSCs was the highest as determined by ELISA and abolished after HIF-1α silencing by siRNA. Highest expression of VEGFR2 in group-4 MSCs was also confirmed by fluorescent immunostaining and flow cytometry. Four hours of VEGF treatment induced higher tube formation in group-4 as compared to group-1 MSCs. In transwell migration assays, VEGF exerted a stronger chemoattractant effect on group-4 as compared with group-1 MSCs. Group-4 MSCs showed higher expression of VEGFR2 after transplantation into a rat myocardial infarction model. Transplantation of group-4 MSCs also promoted the mobilization of VEGFR2 positive cells into the cell transplanted region.
Conclusion: Co-overexpression of Ang-1 and Akt synergizes release of HIF-1α dependent angiogenic mediators and promotes endothelial differentiation as well as recruitment of endothelial progenitor cells into the cell transplanted area to enhance angiogenesis.