Last week, researchers at the Sunnybrook Health Sciences Centre in Toronto successfully penetrated the blood-brain barrier (or BBB) to administer chemotherapy into the brain tumor of a patient. This method of injecting chemicals into the brain isn’t entirely new, however this is the first time doctors were able to get through the barrier non-surgically.
“The blood-brain barrier (BBB) has been a persistent obstacle to delivering valuable therapies to treat disease such as tumours,” explains lead investigator Dr. Todd Mainprize. “We are encouraged that we were able to temporarily open this barrier in a patient to deliver chemotherapy directly to the brain tumour.”
The BBB is made up of endothelial cells, which tightly fit together to form a barrier that keeps potentially toxic substances from entering the brain via the blood stream. It’s effectively like a thin layer of saran wrap that covers the small blood vessels in the brain. This is because the brain needs special microenvironments to function properly. Delicate cells in the brain can become damaged if exposed to the constant and drastic fluctuations of chemicals like hormones or potassium that your body undergoes. However, while it does a good job separating the blood in the rest of your body from the blood in your grey matter, it also blocks many medical substances from entering.
“The BBB prevents the brain uptake of >98% of all potential neurotherapeutics,” according to William Pardridge from the University of California, Los Angeles (UCLA) School of Medicine.
Researchers have been able to get around this obstacle in the past through osmotic disruption, a procedure involving a concentrated sugar solution being injected into the endothelial cells to make them shrink temporarily so that drugs can pass through. Despite this method’s success in clinical trials, it is still considered a surgical procedure. The new procedure used by the team at Sunnybrook’s means there is now a way to cross the blood-brain barrier in a non-invasive manner.
The team utilized MRI guided ultrasound to prompt the opening of the BBB’s tight junctions, injecting a chemotherapy drug and some microscopic bubbles into the brain of the patient. The bubbles, which were smaller than red blood cells, were then expanded and compressed with ultrasound waves that caused them to vibrate and loosen the intersections of the BBB’s cells.
Judging from the initial brain scans, the procedure seems to have went off without a hitch. Despite the blood-brain barrier being reversibly opened successfully, the team still doesn’t know how much of the chemotherapy drug reached its intended target. The patient’s status is currently being monitored as she recovers, with the team hoping to test the new procedure on several more patients like her later on. Until now, many therapeutics used to treat malignant brain tumors have been limited by their inability to pass through the BBB. There is still much more research needed to be done, the researchers admit, but the ability to send drugs directly to certain parts of the brain without surgery is a huge step forward in the fight against conditions like epilepsy, Alzheimer’s, and many more.
“Breaching this barrier opens up a new frontier in treating brain disorders,” says chairman of the Focused Ultrasound Foundation, Dr. Neal Kassell. “We are encouraged by the momentum building for the use of focused ultrasound to non-invasively deliver therapies for a number of brain disorders.”