Fucoidan in a 3D scaffold interacts with vascular endothelial growth factor and promotes neovascularization in mice

The aim of this study was to functionalize 3D porous cross-linked scaffolds with natural non-animal sulfated polysaccharide fucoidans in order to allow a delivery of vascular endothelial growth factor (VEGF) and potentiate its angiogenic activity. Microporous (20 mu m) and macroporous (200 mu m) scaffolds were functionalized with low, medium, or high molecular weight fucoidans (named LMWF, MMWF, and HMWF, respectively). In vitro, addition of fucoidans promoted endothelial progenitor cells proliferation in both micro- and macroporous scaffolds. While control scaffolds without fucoidans loaded with VEGF(165) (100 ng) showed a fast burst release in PBS during the first 24 h, MMWF significantly reduced the VEGF(165) release (p < 0.001). Surface plasmon resonance experiments confirmed a direct interaction between MMWF and VEGF(165), characterized by an affinity K-D (K-d/K-a) of 1x10(-9) M. In a subcutaneous angiogenesis model in mice, fucoidan functionalized scaffolds showed a more intense vascularization response than control groups. Expression of isolectin-B4 and alpha-smoothmuscle actin, as well as confinement of erythrocytes, demonstrated the neoformed blood vessels functionality. There was a significant difference in neovessel area and neovessel density between MMWF scaffolds or VEGF(165) scaffolds and MMWF+VEGF(165) scaffolds (p < 0.001 for all cases). Here, we demonstrate that fucoidan sequesters VEGF(165) and delivers biological cues promoting angiogenesis. In conclusion, this study shows that hydrogels functionalized with fucoidan can direct the formation of mature vasculature through a local release of VEGF(165) and can be a useful tool in ischemic tissues to guide therapeutic angiogenesis.