Purification and culture of aOPCs from the adult rat brain
Density gradients have often been used to purify microglia and hippocampal NSPCs from adult rodent brains (gradients spanning 1.030–1.065 g/ml in the case of microglia16,17,18 and 1.065–1.074 g/ml in the case of NSPCs)17,18,19, as they allow less buoyant cells to be separated)19. In these purification procedures, the higher buoyancy (<1.04 g/ml) cell fractions are discarded, because they are regarded as consisting merely of accumulated debris, mainly myelin16,17,19.
However, our previous studies24 indicated that many unidentified cell types were present in these more buoyant fractions (<1.04 g/ml), especially those in the density gradient spanning 1.029–1.041 (Fig. 1a).