Neurosurgeons withdrew the stem cells from the brains of adults during routine surgery for hydrocephalus, or water on the brain, a researcher at the Stockholm Karolinska Institute told the Swedish daily Svenska Dagbladet.
As long as an agent was present to induce cell division, the extracted stem cells created new and working brain cells.
"So far we have managed to produce several millions of new cells from the original stem cells.
About 25 percent of them are (active) neurons," Ulf Westerlund, who presented his doctoral thesis on the subject last week, told the paper.
When the researchers added glutamate, a salt that functions as a neurotransmitter in the central nervous system, the new cells communicated in a network, according to Westerlund.
Stem cells are nascent cells which can develop into replacement cells for damaged organs or body parts.
Researchers have long attempted to find ways of replacing dead brain cells with healthy ones in order to reverse the tragic effects of such diseases as Alzheimer's, Parkinson's and multiple sclerosis, in which the brain slowly dies.
In cooperation with the University of California at Los Angeles, Westerlund and other Swedish researchers have inserted the extracted human stem cells into the spinal marrow of rats, revealing that also there the cells continued to divide and create new cell neurons.
The injection of stem cells into the rats also appeared to lead to quicker recovery for allodynia, or pain that results from a non-injurious stimulus to the skin, according to Westerlund.
"The mere potential of these cells has had a significant impact of how we today evaluate the regenerative capacity of the central nervous system and, importantly, on the possible means for science to provide insights in neural repair," he wrote in his thesis.