Astrocytes in injured adult rat spinal cord may acquire the potential of neural stem cells.

It has been well documented that in adult rats astrocytes in the subventricular zone and subgranular layer of the dentate gyrus are neural stem cells. Elsewhere in the CNS astrocytes are not generally recognized as stem cells. Here we describe nestin expression in a population of astrocytes in the spinal cord of adult rat following cord injury. In either hemitransectioned or longitudinally cut spinal cord, there was widespread nestin expression in astrocytes of both the gray and white matters. Isolation of the lateral part of the spinal cord from the central canal region, where stem cells may reside, could not block the appearance of nestin-immunoreactive astrocytes in the lateral cord, and none of them showed Fast DiI labeling after the central canal ependyma had been labeled by the dye, indicating that the nestin-immunoreactive astrocytes can evolve locally in the lateral cord. They were found to be undergoing a process of de-differentiation. Culture of the nestin-immunoreactive astrocytes of the lateral cord generated neurospheres, the cells of which had the ability of self-renewal, and were able to differentiate into neurons, astrocytes, or oligodendrocytes. Taken together, the results indicate that the astrocytes in injured adult rat spinal cord may acquire the potential of neural stem cells.