Bone marrow stem cells are able to differentiate into a number of cell types, including liver, lung, and neuronal cells in rodents, but it has been unclear if cells transplanted into human brains can differentiate into neurons. In the January 21 early edition of the
Mezey et al. examined post-mortem brain samples from females who had previously received male bone marrow cell transplants. They examined sections from different brain regions from all four patients and observed that a number of cells (including neurons) contained Y chromosomes. This was particularly marked in samples from the hippocampus and cerebral cortex. One 3-year-old patient (who lived the...