Firmly pressing down on shin bones for just a few minutes every day drastically improved movement and cognition in mice and pigs one week after they had a traumatic brain injury. The intervention stimulates bone cells that are sensitive to physical force, causing them to release substances that promote good brain health. How concussion can lead to brain damage – and what to do to prevent it Traumatic brain injuries are usually caused by a forceful bump, blow or jolt to the head or body, such as during a fall or car crash.
More than 1 million people in England and Wales attend emergency departments each year with recent head injuries, of which about 40,000 are a traumatic brain injury. Despite decades of effort, no approved drug restores lost brain function after a traumatic brain injury, and physical rehabilitation to improve symptoms has limited benefits. Previously, studies have shown that our bones release proteins and hormones that influence other organs, including the brain.
Xiaochun Bai at Southern Medical University in Guangzhou, China, and his colleagues have also found that hundreds of these molecules change in response to weight-bearing activity, like walking or running, and that traumatic brain injuries can accelerate the healing of fractured bones by releasing molecules that stimulate bone growth. This led them to wonder whether this communication goes both ways, which would mean that stimulating bones helps an injured brain. To find out, male mice were given moderate traumatic brain injuries, which can lead to long-term or lifelong health problems in people, while under anaesthesia.
The next day, their shin bones were compressed lengthwise, from knee to ankle, using a mechanical loading device about 15 times their body weight, a force mice can usually tolerate. This was applied for 2.5 minutes per day over five days. The mice’s motor and cognitive functions were then tested one week and eight weeks after their injuries.
The researchers found that the treated mice descended a pole more quickly than untreated mice at weeks one and eight, with the former group’s times being similar to those of mice without brain injuries. In a spatial memory test, where the mice learned to find a hidden platform in water, the mice in the bone-compression group crossed it nearly five times as often as the untreated mice one week after their injuries and about 1.5 times as often after eight weeks. Buried deep within bone are cells called osteocytes, which contain ion channels called Piezo1 that open when they sense force.
In another part of the experiment, the team knocked out Piezo1 in osteocytes in a different group of mice with traumatic brain injuries. Without Piezo1, bone compression had no impact on the mice’s motor or memory functions. Next, the researchers took serum – the liquid portion of blood – from the treated mice and found it contained elevated levels of three molecules: BDNF (which supports the survival, growth and maintenance of neurons), PF4 (which is involved in inflammation) and dopamine (a neurotransmitter involved in memory and movement).
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