Engineering Injectable Microporous Hydrogels for Brain Repair

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Project summary Stroke is the leading cause of adult disability with 800,000 new stroke patients per year in the US 1. After ischemic stroke both the brain vasculature and nerves are severely damaged leading to the neurological deficit that causes disability. Although better patient prognosis has been linked to increased angiogenesis and overall re-perfusion of the stroke area, no therapy currently exists to enhance angiogenesis within the stroke cavity to promote repair. Although hydrogel microstructure can be engineered to promote angiogenesis in vivo even in the absence of growth factors, current scaffolds to promote repair in the brain are not porous and, thus, their microstructure cannot be engineered. The studies in this grant aim to design and synthesize an injectable hydrogel formulation that can have a user defined microstructure to promote collective migration into the scaffold, leading to enhanced angiogenesis and neuroprogenitor (NPC) cell migration to the lesion site. In particular, we propose to inject into the stroke cavity a microporous annealed particle (MAP) hydrogel that releases vascular endothelial growth factor-A 165 (VEGF), platelet derived growth factor-BB (PDGF), and stromal derived factor 1 (SDF-1) with controlled release kinetics to promote the formation of a neurovascular niche within the stroke cavity. We believe that the generation of this neurovascular niche will promote functional recovery after stroke. Aim 1 of the proposed research investigates the generation of different microstructures and the role of MAP hydrogel microstructure on vascularization. Aim 2 will investigate the generation of MAP hydrogels that can release VEGF and PDGF with controlled kinetics and study the combined effects of microstructure and biochemical signal delivery. Last, in Aim 3, we will engineer the sustained release of SDF-1 from the MAP hydrogel and study the migration of NPCs towards the lesion site. Taken together we aim to (i) understand the relationship between hydrogel microstructure, bioactive signal release ad their combination on vascular patterning in vitro and in the brain and (ii) recruit endogenous NPCs to the stroke cavity and promote repair through SDF-1 gradients and active angiogenesis.