Sphere formation of adipose stem cell engineered by poly-2-hydroxyethyl methacrylate induces in vitro angiogenesis through fibroblast growth factor 2

A number of researchers have been reporting a wide range of in vitro and in vivo studies of cell engraftment to enhance angiogenesis using stem cells. Despite these efforts, studies involving three-dimensional (3D) culture method that mimics in vivo environment have not reached its peak yet. In this study, we investigated the change and effects on cellular angiogenic growth factors through sphere formation of adipose stem cell (ASC) which is engineered by poly-2-hydroxyethyl methacrylate (Poly-HEMA). First of all, we successfully induced sphere formation of ASC (sph-ASC) on Poly-HEMA coated plates. sph-ASC represented significantly higher expression levels of anti-apoptotic and hypoxic factors compared to monolayer adherent ASC (adh-ASC). Interestingly, sph-ASC showed higher mRNA levels of the following genes; CD31, CD144, VWF, IGF-2, MCP-1, PDGF-A, VEGF-A, VEGF-C, and FGF-2. In addition, mRNA expressions of angiogenic growth factor receptors such as Flk1, FGFR1, FGFR2, and Tie2 were elevated in sph-ASC. In protein level, Cytokine/Chemokines antibody array revealed a significant increase of FGF-2 in sph-ASC (3.17-fold) compared to adh-ASC. To investigate the effects of FGF-2 on sph-ASC, Matrigel angiogenic invasion assay showed significant reduced level of FGF-2 in FGF-2 siRNA transfected sph-ASC (2.27-fold) compared to negative control siRNA transfected sph-ASC. These findings suggest that Poly-HEMA coated plates induce sphere formation of ASC which has significantly higher expression of FGF-2, and plays a critical role as a major regulating growth factor of in vitro angiogenesis.