In what could be called a key breakthrough, scientists have found that tiny blood vessels in brain spit to survive.
A team at Northwestern University has, in fact, discovered that capillaries have a unique method of expelling debris, such as blood clots, cholesterol or calcium plaque, which blocks the flow of essential nutrients to brain cells.
The capillaries spit out the blockage by growing a membrane that envelopes the obstruction and then shoves it out of the blood vessel. And, this critical process is 30 to 50 per cent slower in an ageing brain and likely results in the death of more capillaries, say the scientists.
"The slowdown may be a factor in age-related cognitive decline and may also explain why elderly patients who get strokes do not recover as well as younger patients. Their recovery is much slower," said lead scientist Prof Jaime Grutzendler.
The findings, published in the 'Nature' journal have been based on a study of mice.
Researchers have long understood how large blood vessels clear blockages: blood pressure pushes against the clot and may eventually break it down and flush it away, or clot busting enzymes rush to the scene to dissolve a blockage.
But little was known about how capillaries clear blockages.
The Northwestern study first demonstrated that enzymes and blood pressure aren't efficient at clearing capillary clots within the critical 24 to 48 hours.
Those mechanisms work half the time and only when blood clots are involved, not other types of debris, particularly cholesterol, which is difficult to dissolve.