Adipose-derived mesenchymal stromal cells decrease prion-induced glial inflammation in vitro

Prion diseases are characterized by the cellular prion protein, PrP^C, misfolding and aggregating into the infectious prion protein, PrP^Sc, which leads to neurodegeneration and death. An early sign of disease is inflammation in the brain and the shift of resting glial cells to reactive astrocytes and activated microglia. Few therapeutics target this stage of disease. Mesenchymal stromal cells produce anti-inflammatory molecules when exposed to inflammatory signals and damaged tissue. Here, we show that adipose-derived mesenchymal stromal cells (AdMSCs) migrate toward prion-infected brain homogenate and produce the anti-inflammatory molecules transforming growth factor β (TGFβ) and tumor necrosis factor-stimulated gene 6 (TSG-6). In an in vitro model of prion exposure of both primary mixed glia and BV2 microglial cell line, co-culturing with AdMSCs led to a significant decrease in inflammatory cytokine mRNA and markers of reactive astrocytes and activated microglia. This protection against in vitro prion-associated inflammatory responses is independent of PrP^Sc replication. These data support a role for AdMSCs as a beneficial therapeutic for decreasing the early onset of glial inflammation and reprogramming glial cells to a protective phenotype.