Vascular endothelial growth factor-loaded injectable hydrogel enhances plasticity in the injured spinal cord.

We hypothesized that vascular endothelial growth factor (VEGF)-containing hydrogels that gelify in situ after injection into a traumatized spinal cord, could stimulate spinal cord regeneration. Injectable hydrogels composed of 0.5% Pronova UPMVG MVG alginate, supplemented or not with fibrinogen, were used. The addition of fibrinogen to alginate had no effect on cell proliferation in vitro but supported neurite growth ex vivo. When injected into a rat spinal cord in a hemisection model, alginate supplemented with fibrinogen was well tolerated. The release of VEGF that was incorporated into the hydrogel was influenced by the VEGF formulation [encapsulated in microspheres or in nanoparticles or in solution (free)]. A combination of free VEGF and VEGF-loaded nanoparticles was mixed with alginate:fibrinogen and injected into the lesion of the spinal cord. Four weeks post injection, angiogenesis and neurite growth were increased compared to hydrogel alone. The local delivery of VEGF by injectable alginate:fibrinogen-based hydrogel induced some plasticity in the injured spinal cord involving fiber growth into the lesion site.