Because it is insulated behind an impenetrable layer of tightly packed cells, the brain is a tough nut to crack. This layer of cells, known as the blood-brain barrier, is good for keeping out harmful chemicals and bacteria. The downside? It means it’s impossible to gain direct access for delivering medicine that could help treat neurodegenerative diseases such as Parkinson’s or Alzheimer’s.
To get drugs directly into the brain you have to drill into the skull, which is about as fun as it sounds. Most drugs administered orally or intravenously generally just can’t get to the brain and therefore are useless treatments for brain disease. What to do?
Neuroscientist Viviana Gradinaru and her colleagues at the California Institute of Technology think they have an answer: Viruses. Because viruses are able to enter cells and change the DNA of the cells, and because they also have protein shells that could potentially carry drug treatments within them, viruses may be the key for cracking the blood-brain barrier for therapeutic use. The idea is that a small amount of a harmless virus could be injected into the bloodstream along with the helpful treatment that could gain access to the brain.
In trials on mice, this theory proved to be successful. Through the use of color coding, the scientists could observe the viral concoction making its way all the way to the brain. And, even more encouraging, the viruses stayed there for as long as one full year. You can read more about how viruses were selected in this article in Scientific American. The full results are published in Nature Biotechnology.
In other heartening news, ongoing clinical trials using ultrasound to break the blood-brain barrier have had initial positive outcomes as well. Alexandre Carpentier, a neurosurgeon at the Pitié-Salpêtrière Hospital in Paris, found a way to deliver chemotherapy to tumors in the brain with a device called SonoCloud, which he has successfully implanted in fifteen brain cancer patients. Neal Kassell, founder of the Focused Ultrasound Foundation, said the French study “is the first time they’ve shown the safety of repetitively opening the blood-brain barrier in humans.”
Whether it’s with viruses or ultrasound, progress is being made to break down the stubborn blood-brain barrier, and both methods could prove to be extremely useful in treating a wide range of neurological diseases.