[A version of this item appears in: Dementia: the Latest Evidence Newsletter (RWHT), Volume 1 Issue 10, May 2011].
A new way of delivering drugs to the brain uses the body’s own “transporters”, called exosomes. This technique of drugs delivery could be vital for treating diseases such as Alzheimer’s, Parkinson’s and Muscular Dystrophy.
Previously, one of the medical challenges in treating diseases of the brain has been getting treatments across the blood-brain barrier, which prevents bacteria from crossing over from the blood while allowing oxygen to get through. Drugs can be blocked by this barrier. In a study on mice the researchers used exosomes to cross the blood-brain barrier.
Researchers harvested exosomes from mouse dentritic cells, and then fused these exosomes with targeting proteins from the rabies virus which binds to acetylcholine receptors in brain cells (so that the exosome would target the brain). The exosomes were filled with a piece of genetic code, siRNA, and injected into mice, where the siRNA was delivered to the brain cells and “turned off” a gene, BACE1, which is involved in Alzheimer’s disease. There appeared to be no immune response to these modified cells.
The research group believes that this new method could modified to treat other conditions and other parts of the body. It can be made specific by changing the drug used. The team expect to begin trials in human patients within five years.
Exosomes may have other potential medical applications. Exosomes could be used to prime the immune system to recognize and destroy cancer cells, thereby making them a potential tool as cancer vaccines. Exosomes might form the basis of many future nanoscale drug delivery systems.
Note: This is early research and the technology has not been tested in human cells. There are several genes associated with Alzheimer’s Disease, so it is unclear whether switching off the activity of one of them might yield benefits. More research is needed. There are technical and ethical issues associated with gene therapy in humans.
Gallagher, J. (2011). Breakthrough in delivering drugs to the brain. London: BBC Health News, March 20th 2011.
New gene therapy ‘may target’ Alzheimer’s. London: NHS Choices, March 21st 2011.
Links to the original article:
Full Text Link (Note: A subscription is required to read the entire article).
Alvarez-Erviti, L. Seow, Y. [and] Yin, H. [et al] (2011). Delivery of siRNA to the mouse brain by systemic injection of targeted exosomes. Nature Biotechnology, March 2011, Vol.29(4), pp.341-5. (Click here to view the PubMed abstract).
An entirely different approach to breaching the human brain barrier, possibly also of interest:
Roberts, M. (2015). Scientists breach brain barrier to treat sick patient. London: BBC Health News, November 10th 2015.