Astrocytes teach stem cells to become neurons

Astrocytes make up nearly half of the total number of brain cells, providing structural, metabolic and tropic support for neurons, but they were considered to play no active part in stem cell differentiation. In May 2 Nature, Hongjun Song and colleagues from The Salk Institute, La Jolla, California, show for the first time that adult astrocytes can induce neurogenesis by instructing the stem cells to adopt a neuronal fate (Nature 2002, 417:39-44).

Song et al. used cell culture systems and investigated the contributions made by different cell types to the fate specification of fibroblast growth factor-2 (FGF-2)-dependent stem cells derived from adult hippocampus. They observed that only hippocampal astrocytes actively regulated adult neurogenesis both by instructing neuronal fate commitment and promoting proliferation of adult neural stem cells. Astrocytes from adult spinal cord did not promote neurogenesis.

"Song et al.'s discoveries may lead to a...