ST8SIA2 and brain ischemia: Of note, a previous study on human brain ischemia showed that the combination of polysialic acid (polySia, PSA, the main product of St8sia2) moiety and neural adhesion cell molecule (NCAM), abbreviated as PSA-NCAM, was significantly elevated in neuronal progenitor cells (NPCs) [33], implying the involvement of St8sia2 in this process.