When your brain is severely concussed— whether via car crash or IED— individual neurons will retract like the arms of a sea anemone, severing important neural connections and constricting blood flow. Now, Harvard researchers believe they've figured out why.
Harvard bioengineer Kit Parker and his team built a simple neural network of engineered human blood vessels and rat neurons and then created devices to mimic blast waves moving through the tissue. They found that integrins, proteins that attach a cell's membrane structure to an exterior matrix (say, other neurons), when plucked or stretched beyond their normal limits, set off a signalling cascade along what's known as the the Rho–ROCK pathway. When this pathway becomes overstimulated it causes neuronal extensions to swell, then retract, and surrounding blood vessels to constrict as well. This results in ischemia, reduced cerebral blood flow, which itself can cause further brain damage and cell death. However, when a Rho–ROCK pathway inhibitor was applied, both contraction and constriction effects were either significantly delayed or prevented outright.
Granted, traumatic injuries to the body's most complex system probably aren't going to be resolved by simply inhibiting a single neural pathway. "I think the reality is that when the whole tissue undergoes deformation, you're probably going to get a combination," Ken Barbee, a bioengineer at Drexel University in Philadelphia. The initial results, however, are quite promising and may lead to better and faster treatment for severe head injuries. [Nature News - top art courtesy Tom Haex via Flickr]