Efficient generation of neural precursors from adult human skin: astrocytes promote neurogenesis from skin-derived stem cells.

BACKGROUND

Neural stem cells are a potential source of cells for drug screening or cell-based treatments for neurodegenerative diseases. However, ethical and practical considerations limit the availability of neural stem cells derived from human embryonic tissue. An alternative source of human neural stem cells is needed; a source that is readily accessible, easily expanded, and reliably induced to a neural fate.

METHODS

Dermis isolated from biopsy samples of adult human skin was cultured and expanded in the presence of the mitogens epidermal growth factor (EGF) and fibroblast growth factor 2 (FGF 2), and then by serum. We used immunocytochemical techniques, clonal analysis, and physiological characterisation to assess neural differentiation after the treatment of expanded cells with novel induction media.

FINDINGS

Initial characterisation of skin samples confirmed the absence of nestin, a neural precursor marker. Sequential culture in EGF and FGF 2 followed by adherent expansion in serum, and re-exposure to mitogens in substrate-free conditions resulted in large numbers of nestin-positive/musashi-positive neural precursors. Subsequent exposure of these precursors to hippocampal-astrocyte-derived signals resulted in cells of neuronal morphology that had stable expression of markers of neuronal differentiation (neurofilament, beta tubulin). We also show the presence of voltage-dependent calcium transients, and demonstrate monoclonal neural potential.

INTERPRETATION

We describe the isolation and characterisation of cells derived from adult human dermis that can be expanded for extended periods of time in vitro, while retaining inducible neural potential. The generation of almost limitless numbers of neural precursors from a readily accessible autologous adult human source provides a platform for further experimental studies and has potential therapeutic implications.