The blood-brain barrier has long been a significant block against getting drugs and therapies into the brain to exact their effect. However, for the first time, this hurdle has been overcome. Clinicians have been able to punch temporary holes in the blood-brain barrier with the aim to introduce therapies that can cross these newly formed pores. But how does it work?
The blood-brain barrier is a selective barrier that protects the brain from infection and harmful substances in circulation. It divides the circulating blood from the brain extracellular fluid and is comprised of specialised barrier cells, called endothelial cells. They are held together by tight junction connections that prevent the passage of materials to the brain and provide a selective nature to the barrier.
The new technique involves the injection of microbubbles of gas into the bloodstream and then applying focused ultrasound to the patient’s skull. This process causes the bubbles to vibrate and push through the blood-brain barrier along with the chemotherapy or treatment, allowing the therapy to localise to the correct place. The practice of using microbubbles and ultrasound has recently been in the media for its ability to control brain cells in worms. As it stands, the technique has only been tested in one patient. A Canadian team at Sunnybrook Health Sciences Centre was able to treat 56-year-old, brain tumour patient, Bonny Hall, whose tumour required more aggressive and specific therapy. The treatment was conducted alongside chemotherapy to help tackle her brain tumour and, following a scan, it was suggested that the technique had worked. More detailed analysis of her tumour will follow to determine the extent of the barrier penetration.
Lead researcher, Dr. Todd Mainprize, stated: “The results are preliminary at this point because we don’t have the levels of chemotherapy – but based on the gadolinium MRI scan, we were clearly able to open up the blood-brain barrier non-invasively, reversibly and, it appears, quite safely”.
But what are the implications for future treatment? Some skepticism over its practical use in treating brain tumours has arisen. Professor Dylan Edwards, Chair of Cancer Studies, Professor of Cancer Biology and researcher from UEA’s School of Biological Sciences said: “I think it may prove useful for getting drugs into the brain for a variety of conditions, but in glioblastoma the blood-brain barrier is leaky anyway due to the tumour vessels being leaky”. This would suggest that the applications for cancers may not be certain, but the possibility for treatments for other conditions may be hopeful.
It is important to consider this a starting point, an exciting concept that is not yet fully tested or researched. There are concerns for example with altering the blood-brain barrier, the long term implications of the treatment are not yet known and there may be concerns with patients who are immune compromised. There is hope that this method would be able to treat a number of diseases, not just cancers, such as Alzheimer’s and other neurodegenerative diseases. Six to ten more patients will undergo the procedure.