OBJECTIVETo establish a method for organotypic slice culture of neonatal rat cortex in a modified condition and investigate the effect of spatial signals on neural stem cell (NSC) differentiation.

METHODSThe brain slices (200 µm in thickness) of neonatal SD rats (3 to 5 days old) were prepared and cultured in modified serum-free DMEM/F12 medium at 37 degrees celsius; with 95% O(2) and 5% CO(2). The organotypic slice cultures were observed regularly. NSCs isolated from the cortex of rat embryos (14-15 embryonic days) were cultured in serum-free DMEM/F12 supplemented with B27 and N2, and the passage 3 NSCs were labeled by CM-DiI before transplanted onto the organotypic slices cultured for 2 weeks. The survival of transplanted NSCs was assessed, and the cell differentiation was identified by immunofluorescence staining.

RESULTSThe organotypic slice cultures were well maintained for at least 4 weeks in the modified medium. The thickness of the organotypic slices reduced from 200 µm to 130 µm after 2-week culture in vitro due to the migration of the cells on the edge of the slices. CM-DiI-labeled NSCs survived well and differentiated into GFAP(+) glia and β-tubullin III(+) neurons.

CONCLUSIONNeonatal rat organotypic brain slice can be successfully cultured in a modified condition to serve as a model for studying NSC differentiation induced by spatial signals.