An optimized experimental strategy for efficient conversion of embryonic stem (ES)-derived mouse neural stem (NS) cells into a nearly homogeneous mature neuronal population.

NS cells are a homogeneous population of neural stem cells which were previously derived from embryonic stem cells as well as from the fetal and adult brain. Our previous reports have described a 21 day long neuronal differentiation protocol able to reproducibly convert adult SVZ-derived NS (aNS) cells into a population composed of 65% mature neurons and 35% glial cells. Here we have developed a different procedure specifically applicable to ES-derived NS cells in order to fully explore their neurogenic capacity. Differently from the aNS differentiation procedure, optimized neuronal output from ES-derived NS cells requires replating of the cells on appropriate substrates followed by sequential exposure to modified media. In these conditions, ES-derived NS cells differentiate into neurons with a barely appreciable quota of astrocytes and occasional oligodendrocytes. In particular, 21 days after the beginning of the treatment, 85% of the cells has differentiated into molecularly and electrophysiologically mature neurons belonging to the GABAergic lineage. The procedure, which is applicable with no considerable differences to different ES-derived NS cell lines and to NS cells at different passages, opens to the possibility of molecular and biochemical studies on close-to-uniform stem cell derived neurons.

Differentiating embryonic stem-derived neural stem cells show a maturation-dependent pattern of voltage-gated sodium current expression and graded action potentials.

A population of mouse embryonic stem (ES)-derived neural stem cells (named NS cells) that exhibits traits reminiscent of radial glia-like cell population and that can be homogeneously expanded in monolayer while remaining stable and highly neurogenic over multiple passages has been recently discovered. This novel population has provided a unique in vitro system in which to investigate physiological events occurring as stem cells lose multipotency and terminally differentiate. Here we analysed the timing, quality and quantity of the appearance of the excitability properties of differentiating NS cells which have been long-term expanded in vitro. To this end, we studied the biophysical properties of voltage-dependent Na(+) currents as an electrophysiological readout for neuronal maturation stages of differentiating NS cells toward the generation of fully functional neurons, since the expression of neuronal voltage-gated Na(+) channels is an essential hallmark of neuronal differentiation and crucial for signal transmission in the nervous system. Using the whole cell and single-channel cell-attached variations of the patch-clamp technique we found that the Na(+) currents in NS cells showed substantial electrophysiological changes during in vitro neuronal differentiation, consisting mainly in an increase of Na(+) current density and in a shift of the steady-state activation and inactivation curves toward more negative and more positive potentials respectively. The changes in the Na(+) channel system were closely related with the ability of differentiating NS cells to generate action potentials, and could therefore be exploited as an appropriate electrophysiological marker of ES-derived NS cells undergoing functional neuronal maturation.

Setting the conditions for efficient, robust and reproducible generation of functionally active neurons from adult subventricular zone-derived neural stem cells.

Although new culture conditions enable homogeneous and long-term propagation of radial glia-like neural stem (NS) cells in monolayer and serum-free conditions, the efficiency of the conversion of NS cells into terminally differentiated, functionally mature neurons is relatively limited and poorly characterized. We demonstrate that NS cells derived from adult mouse subventricular zone robustly develop properties of mature neurons when exposed to an optimized neuronal differentiation protocol. A high degree of cell viability was preserved. At 22 days in vitro, most cells (65%) were microtubule-associated protein 2(+) and coexpressed gamma-aminobutyric acid (GABA), GAD67, calbindin and parvalbumin. Nearly all neurons exhibited sodium, potassium and calcium currents, and 70% of them fired action potentials. These neurons expressed functional GABA(A) receptors, whereas activable kainate, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid and N-methyl-D-aspartic acid receptors were present in approximately 80, 30 and 2% of cells, respectively. Antigenic and functional properties were efficiently and reliably reproduced across experiments and cell passages (up to 68). This is the first report showing a consistent and reproducible generation of large amounts of neurons from long-term passaged adult neural stem cells. Remarkably, the neuronal progeny carries a defined set of antigenic, biochemical and functional characteristics that make this system suitable for studies of NS cell biology as well as for genetic and chemical screenings.