Spanish researchers have observed the ability of bone marrow-derived stem cells (BMDC) to contribute to a several different neural cell types in other areas of the brain besides the cerebellum, including the olfactory bulb, because of a mechanism of “plasticity”. BMDCs have been recognized as a source for transplantation because they have the capacity to contribute to different cell populations in several different organs under both normal and pathological conditions. Many BMDC studies have aimed at repairing damaged brain tissue or helping to restore lost neural function, and much of that research has focused on BMDC transplants to the cerebellum, which is located at the back of the brain.
Eduardo Weruaga of the University of Salamanca, Spain commented, “To our knowledge, ours is the first work reporting the BMDC’s contribution to the olfactory neurons, We have shown for the first time how BMDCs contribute to the central nervous system in different ways in the same animal depending on the region and cell-specific factors.”
Weruaga and his group grafted bone marrow cells into mutant mice that suffered from degeneration of specific neuronal populations at different ages. Then they compared these mice to similarly transplanted healthy controls, and they found that increased numbers of transplanted BMDCs did increase the number of bone marrow-derived stem cells in the experimental groups. However, six weeks after transplantation, more bone marrow-derived microglial cells were observed in the olfactory bulbs of the test animals even though degeneration of mitral cells was still in progress. Such a difference was not observed in the cerebellum where cell degeneration had been completed.
Weruaga noted: “Our findings demonstrate that the degree of neurodegenerative environment can foster the recruitment of neural elements derived from bone marrow. But we also have provided the first evidence that BMDCs can contribute simultaneously to different encephalic areas through different mechanisms of plasticity: cell fusion for Purkinje cells, which are among the largest and most elaborately dendritic neurons in the human brain, and differentiation for olfactory bulb interneurons.”
The Salamanca group also confirmed that BMDCs fuse with Purkinje cells in the cerebellum, but they also found that the neurodegenerative environment had no effect on the behavior of the BMDCs. “Interestingly, the contribution of BMDCs occurred through these two different plasticity mechanisms, which strongly suggests that plasticity mechanisms may be modulated by region and cell type-specific factors,” he said.
Paul R. Sanberg, distinguished professor of Neuroscience at the Center of Excellence for Aging and Brain Repair, University of South Florida made this observation about Weruaga’s study: “This study shows a potential new contribution of bone marrow derived cells following transplantation into the brain, making these cells highly versatile, in their ability to both differentiate into and fuse with endogenous neurons.” Bone marrow stem cells continue to surprise researchers with their plasticity and ability to become other cell types.