For the first time ever in humans, neuroscientists have penetrated the stubborn barrier that protects the brain from toxins in the bloodstream. The breakthrough means that doctors can now deliver drugs to previously inaccessible parts of the brain, making it easier to treat cancer and neurodegenerative disorders.
Top image: C.J. Guerin, MRC Toxicology Unit / Science Source.
The blood-brain barrier (BBB) is an extremely important shield — a sheath of cells that wraps around blood vessels throughout the brain — that protects the brain from potentially disruptive hormones and neurotransmitters. It also protects the brain from foreign substances, which is good if you want to prevent toxins and bacteria from getting in, but bad if you're a doctor looking to deliver brain-healing medicines.
As we reported back in June, a team of scientists came up with a neat theory about getting cancer medicines out of the bloodstream and into targeted brain tumours. The plan was to use microbubbles in the blood to open up the layer between blood vessels and brain tissue. And to do it, they were going to use ultrasound.
Now, as reported in New Scientist, it actually worked:
With surgeon Alexandre Carpentier at Pitié-Salpêtrière Hospital in Paris, [Michael] Canney tested the approach in people with a recurrence of glioblastoma, the most aggressive type of brain tumour. People with this cancer have surgery to remove the tumours and then chemotherapy drugs, such as Carboplatin, are used to try to kill any remaining tumour cells. Tumours make the BBB leaky, allowing in a tiny amount of chemo drugs: if more could get through, their impact would be greater, says Canney.
The team tested the idea on four patients by implanting an ultrasound transducer through a hole already made in their skulls during tumour-removal surgery. They were then given an injection of microbubbles and had the transducer switched on for 2 minutes. This sent low-intensity pulses of ultrasound into a region of the brain just 10 millimetres by 4 mm. Canney reckons this makes the BBB in this region more permeable for about 6 hours. In this time window, each person received normal chemotherapy.
Since July, they have performed the technique once a month on each of the four patients. It will be a few months before Canney can determine the effect on tumours.
An MRI scan showed that a marker chemical, injected along with the microbubbles, was crossing the BBB. "We hope this means the chemotherapy drug is doing the same thing," says Canney, who presented his observations last week at the Focused Ultrasound symposium in North Bethesda, Maryland.
Encouragingly, similar interventions could be used to treat Alzheimer's. In fact, merely opening up the barrier — with no added drugs — results in a reduction in the protein plaques associated with the disease.
Read the entire article at New Scientist.