A team of scientists at Laval University, led by Alain Simard, have published a paper in the latest edition of the journal Neuron about a natural defense mechanism used by the body to counter the degeneration of brain cells in subjects suffering from Alzheimer’s disease titled Bone Marrow-Derived Microglia Play a Critical Role in Restricting Senile Plaque Formation in Alzheimer’s Disease.
To the non-expert, the abstract of the article can be quite intriguing… (EDIT: I’m not claiming that I’m an expert in the subject… far from that!)
Microglia are the immune cells of the brain. Here we show a massive infiltration of highly ramified and elongated microglia within the core of amyloid plaques in transgenic mouse models of Alzheimer’s disease (AD). Many of these cells originate from the bone marrow, and the ?-amyloid-40 and -42 isoforms are able to trigger this chemoattraction. These newly recruited cells also exhibit a specific immune reaction to both exogenous and endogenous ?-amyloid in the brain. Creation of a new AD transgenic mouse that expresses the thymidine kinase protein under the control of the CD11b promoter allowed us to show that blood-derived microglia and not their resident counterparts have the ability to eliminate amyloid deposits by a cell-specific phagocytic mechanism. These bone marrow-derived microglia are thus very efficient in restricting amyloid deposits. Therapeutic strategies aiming to improve their recruitment could potentially lead to a new powerful tool for the elimination of toxic senile plaques.
In a nutshell, they say that microglia possess an effective method to control the growth of the protein that causes the senile plaques in the brain. It’s the accumulation of those plaques that lead to the advanced states of Alzheimer’s disease. This study showed that blood-derived microglial cells that are associated with senile plaques are able to prevent the formation or eliminate the presence of amyloid deposits in mice that develop the major hallmark of AD.
Furthermore, the study shows that the prescription of anti-inflammatory drugs is not a good way to treat AD’s symptoms, because it hinders the microglia in their task of protecting the brain. The only effect that these drugs can have on the disease is to accelerate its development.
“The cellular therapy won’t help prevent Alzheimer’s disease, but in limiting the development of the senile plaques, we believe that it will help the patients to conserve their autonomy and their cognitive capabilities” said Dr. Serge Rivest, also part of this study. The other authors on the paper are Denis Soulet, Geneviève Gowing and Jean-Pierre Julien, all from Laval University.
The figure above shows microglia (in green) attacking proteins causing the neurons’ death in patients suffering from Alzheimer’s disease. This picture made the front page of Neuron.
This is a significant step towards understanding how to treat (or even cure!) Alzheimer’s disease. You can read the whole paper for free online, at the Neuron archives, hosted at Science Direct.
February 20th, 2006 | General Science