Regeneration and proliferation of embryonic and adult rat hippocampal neurons in culture.

Adult mammalian CNS neurons appear to be terminally differentiated and postmitotic. However, this conclusion may be due to nonpermissive conditions in the brain or in culture media. If embryonic rat hippocampal neurons are cultured in Neurobasal/B27 with FGF2, nearly all neurons proliferated until a maximum density was reached. Similarly, adult neurons can be cultured that fire action potentials and display immunoreactivity for neurofilament, MAP2, tau, and glutamate. Seventy percent of the 3000 isolated adult cells per milligram of brain tissue began to proliferate after 3 days in culture and incorporated BrdU. By 4 days of regeneration in culture, virtually all neuron-like cells with asymmetric processes were glutamate positive and immunoreactive for neurofilament. Immunoreactivity of the intermediate filament stem cell marker nestin increased in adult cells to levels present in freshly isolated embryonic neurons. These are the first studies to demonstrate that over 50% of adult CNS cells with neuron-like characteristics retain regenerative and proliferative potential.