Human amniotic fluid stem cells: neural differentiation in vitro and in vivo.

The successful integration of stem cells after their implantation into the brain has become a central issue in modern neuroscience. In this study, we test the neural differentiation potential of c-Kit(+)/Oct-4(+) human amniotic fluid stem cells (hAFSCs) in vitro and their survival and integration in vivo. hAFSCs were induced towards neural differentiation and specific markers (GFAP, β-III tubulin, CNPase, MAP2, NeuN, synapsines, S100, PMP22) were detected by immunofluorescence and Western blot analysis. Glial proteins were expressed as early as 2 weeks after the initial differentiation stimulus, whereas neuronal markers started to appear from the third week of differentiation under culturing conditions of high cell density. This timeline suggested that glial cells possessed a promoting role in the differentiation of hAFSCs towards a neuronal fate. hAFSCs were then implanted into the lateral ventricle of the brain of 1-day-old rats, since neuronal development occurs up to 1 month after birth in this animal model. Our data showed that hAFSCs survived for up to 6 weeks post-implantation, were integrated into various areas of the central nervous system and migrated away from the graft giving rise to mature neurons and oligodendrocytes. We conclude that hAFSCs are able to differentiate and integrate into nervous tissue during development in vivo.