Hyaluronic acid particle hydrogels decrease cerebral atrophy and promote pro-reparative astrocyte/axonal infiltration after ischemic stroke

Abstract

The death rate due to stroke is decreasing, resulting in more individuals living with stroke related disabilities. Following stroke, dying cells contribute to the large influx of highly reactive astrocytes and pro-inflammatory microglia that release cytokines and lead to a cytotoxic environment that causes further brain damage and prevents endogenous repair. Paradoxically, these same cells also activate pro-repair mechanisms that contribute to endogenous repair and brain plasticity. Here, we show that the direct injection of a hyaluronic acid based microporous annealed particle (HA-MAP) hydrogel into the stroke core reduces the percent of highly reactive astrocytes and increases the percent of alternatively activated microglia in and around the lesion. Further, we show that HA-MAP hydrogel promotes reparative astrocyte infiltration into the lesion, which directly coincides with axonal penetration into the lesion. Additionally, HA-MAP injection decreases cerebral atrophy and preserves nigrostriatal bundles after stroke. This work shows that the injection of a porous scaffold into the stroke core can lead to clinically relevant decrease in cerebral atrophy and modulates the phenotype of astrocytes and microglia towards a pro-repair phenotype.