by Laura Spinney
Bone marrow cells can differentiate into muscle, tendon, bone, cartilage and fat. Now this bountiful, robust and ethically-neutral source seems capable of extending its repertoire to include neurons, too, according to Ira Black of the Department of Neuroscience and Cell Biology at the Robert Wood Johnson Medical School in Piscataway, New Jersey.
Black describes the adult bone marrow stromal cell (BMSC) as "a rather undistinguished-looking, pedestrian, flattened cell." But with their versatile nature, BMSCs seem to share many of the traits of a stem cell population.
When Black and his colleagues placed rat BMSCs in a dish with a neural induction medium, they found that they differentiated into something very distinguished indeed - cells that resembled neurons.
Subsequent genetic analyses showed that these putative neurons express a whole range of neuronal markers and, moreover, that they appear to go through the normal stages of neuronal differentiation.
Just like neuronal precursor cells, they express a protein called nestin very early on, but the nestin then disappears as differentiation proceeds.
Trk A, a receptor for Nerve Growth Factor, is also expressed early on, and persists.
Other markers related to synapse formation can be detected, suggesting that the cells are capable of active communication.
The same has turned out to be true for human BMSCs grown in a neural induction medium.
So they look like neurons in a dish, but do they feel at home in the nervous system of a living animal? In their most recent experiments, the researchers transplanted their putative BMSC-derived neurons into the brain and spinal cord of rats.
When transplanted into the dentate gyrus of the hippocampal formation, says Black, "they appear to have a migratory pattern out from a central core." They survive, extend processes terminating in growth cones, and trigger no inflammation: "The cells seem to thrive," he noted.
But the key question remains: do they function like neurons? The team is poised to perform the electrophysiological tests that will determine this. If the answer is yes, the prospects for their future use are exciting, says Black, who is a science adviser to the Christopher Reeve Paralysis Foundation.
Adult BMSCs have several advantages as a potential source of neurons for the treatment of neurological disease: they are plentiful in bone marrow, they grow robustly in culture, and there would be no ethical concerns over the use of embryonic tissue.
Laura Spinney is a freelance science
writer specializing mainly in psychology and neuroscience. She has also
worked as a writer at New Scientist.
© Elsevier Science Limited 2000