To determine whether the gene expression pattern of our control hiPSC-astrocytes more resembles quiescent or reactive astrocytes, we compared them with an RNA-seq dataset of “proinflammatory” A1-type and “immunoregulatory” A2-type murine astrocytes, as well as their saline- and sham-treated controls (Zamanian et al., 2012). (Because these are in vivo cell types, whereby A1-type astrocytes are induced by a bacterial lipopolysaccharide [LPS] infection and A2-type astrocytes by middle cerebral artery occlusion [MCAO], no comparable dataset exists for human astrocytes.) hiPSC-astrocyte gene expression best clusters with the control conditions (Figures 3B and S3A), suggesting that hiPSC-astrocytes may be closer to the quiescent state than to reactive astrocytes.
