Neuronal differentiation of human iPS-cells in a rat cortical primary culture.

We tested the neuronal differentiation of human iPS-cells under in vitro conditions. For this purpose we pre-differentiated human (h) iPS-cells into neural stem cells and co-cultivated them with a cortical primary culture from embryonic rats. After 2 days of co-cultivation a certain number of hiPS-cells exhibited a clear neuronal morphology combined with expression of betaIII-tubulin and doublecortin. In addition, we found hiPS-cells without neuronal differentiation and cells already expressing betaIII-tubulin but not having yet distinctive axonal and dendritic processes. Human neuronal progenitors, starting neuronal differentiation, were contacted by both neuronal processes from rat neurons and oligodendrocytes, indicating a possible instructive influence by the primary culture on human cells. After 7 days of co-cultivation, however, we observed a complete degeneration of human iPS-derived cells and phagocytosis by microglial cells. Immunocytochemical stainings surprisingly revealed that microglial cells of the cortical primary culture express both CD8 and T-cell receptors.