Bone marrow and brain: unexpected allies or accidental acquaintances?

Almost 10 yr have passed since we first entertained the idea that circulating blood cells originating in the bone marrow might contribute to central nervous system (CNS) cell lineages. Initially, we showed that microgalia are derived from bone marrow stem cells (BMSCs). Later, we found that BMSCs might also give rise to other neural cells--even neurons. We made our first observations in rodents, and then we examined human samples. In the brains of female patients who received bone marrow from male donors there are cells with neurons-specific markers together with the Y chromosome suggesting that they are the progeny donor bone marrow cells. All of our data and numerous recent experiments in the field suggest that circulating BM cells are quite plastic. Thus, they might be used in regenerative medicine to help heal or replace lost tissue in many different organs.