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Open Blood-Brain Barrier to Treat Cancer

Blood_Brain_Barrier

Image credit: Ben Brahim Mohammed

The blood-brain barrier is vital to our life, but in some cases, it might pose big obstacle to medical treatment to save life. It has been claimed by CarThera, a French company that it has identified an approach to open the barrier whenever necessary and close it again afterwards.

Being made from endothelial cells, the barrier could keep the extracellular fluids of the brain and blood apart. Its main function is to ensure those things necessary for the brain from the blood through, they include oxygen, water and sugar. At the same time, the barrier would keep out neurotoxins as well.

However, just like the case when the junk mail filter deal with your emails, in some instances, it malfunctions on both fronts, namely, it would let through things it should not manage while keep out some that are in need.

It is known that although all the large-molecule drugs have potential in treatment of brain conditions like tumors, they have difficulties in penetrating the blood-brain barrier, and even 98% of smaller therapeutic molecules are not included.

Therefore, scientists have been making great efforts to associate therapies to carriers which could penetrate the barrier, or to directly inject drugs into the brain. However theses two methods are not quite satisfactory, because it is natural for tumors to produce leaks in the barrier, thus ensuring chemotherapeutic drugs to pass through, but it also lead to the low efficiency; as a tiny portion get to the tumor, the rest would be kept in the bloodstream so as to cause side-effects.

To tackle such problem, the French company of CarThea chose the completely different path. By doing so, its researchers implanted ultrasound emitters in the brains of four patients with glioblastoma, the most dangerous type in terms of brain tumor. Afterwards, they injected microbubbles, and ultrasound pulses allowed the bubbles to vibrate, in the way to push apart cells of the blood-brain barrier. From MRI images, the microbubbles were shown to get into the extracellular fluid.

According to Michael Canney from CarThera, it was hoped that the chemotherapy drug was doing the same thing. CarThera had released its research results at Focused Ultrasound symposium in North Bethesda, Maryland recently. On the basi of animal models, it was estimated that the barrier would ensure drugs through for nearly 6 hours after the treatment of two minutes. The research on animal showed a 200-600% increases in the concentration of the chemotherapeutic agent at the place where the tumor was located in comparison of methods which mainly focused on local leakiness.

In practice, researchers placed the ultrasound emitters as close to the tumor as possible, and the barrier was just  weakened over a patch of 5cm2  so as to protect the rest of the brain. Further research should be carried out to identify its real effect on treatment of tumors.

From animal studies, the procedure had demonstrated an unexpected benefit. After having their barriers opened with the same technique, the numbers of plaque in animals with the similar symptom of Alzheimer’s disease had been reduced, even without being given drugs to fight the condition.

In Canney’s opinion, given the chance to cross the barrier, the immune cells of blood might do something necessary at least, and it should be true for tumors in the same way.

Image CC By 3.0

Source: New Scientist

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