SPP1 and brain ischemia: Intriguingly, cathodal tDCS led to upregulation of Spp1 encoding for the phosphoprotein osteopontin (OPN), possessing pleiotropic immunoregulatory properties after cerebral ischemia as well as beneficial effects on endogenous neural stem cells (Rabenstein et al., 2015, 2016; Ladwig et al., 2017).