Bone marrow-derived stem cells can become neurons in humans

Findings from an autopsy study suggest that hematopoietic stem cells can become neurons, astrocytes, and microglia in humans — an observation that could have important therapeutic implications for neurodegenerative disorders like Parkinson’s disease.

This is the strongest human evidence to date that bone marrow-derived stem cells can become neurons and supporting cells, senior author Dr. Edward W. Scott, from the University of Florida in Gainesville, told Reuters Health. “A number of reports in murine systems have described bone marrow cells becoming brain cells at low levels,” Dr. Scott noted. “But, there’s lots of controversy regarding whether this is real or the result of fusion events. Our results suggest that transdifferentiation does, in fact, occur.” The new findings, which are reported in the May 1st issue of The Lancet, are based on a study of three women who underwent hematopoietic stem cell transplantation as a treatment for leukemia. In all cases, the patient’s brother served as the stem cell donor and none of the women had ever given birth to a male offspring.Analysis of autopsy brain specimens revealed Y-chromosome-positive hippocampal cells in all three patients. In fact, in one patient, such cells were observed 6 years after transplantation. In two of the patients, only transgender microglia were observed, whereas in the remaining patient, transgender neurons and astrocytes were also seen.The transgender cells accounted for 1% to 2% of the brain cells present. The lack of an extra X chromosome indicated that fusion events were not responsible for the findings, the researchers note.Dr. Scott believes that stem cell therapy may prove useful for disorders like Parkinson’s diseases, provided that treatment is begun early. “If we start treatment early enough we can probably prevent disease progression. However, if the disease is too advanced, the stem cells can be put there, but there’re no cells left to tell them what to do,” he explained.”We are now expanding the study to include an additional 64 patients,” Dr. Scott said. “It looks like transdifferentiation occurs at very low levels and in the larger study we’ll be looking at the factors that influence this. The results from this analysis should be available sometime next year.” (Source: Lancet 2004;363:1432-1437: Reuters Health News: Anthony J. Brown, MD: Oncolink: May 2004)