Protein May Promote Nerve Regeneration

Researchers from the Salk Institute suggest that a certain protein found in the body can promote nerve regeneration, and eventually lead to breakthrough therapies for those who suffer from spinal cord injuries and paralysis.

According to the US Centers for Disease Control and Prevention (CDC), about 200,000 people are living with a spinal cord injury (SCI). These types of injuries are mostly caused by motor vehicle accidents, as well as falls, violence and sports.

All sorts of animals, with the exception of primates, have the natural ability to regrow nerves lost from a SPI - including frogs, dogs, snails and whales. But this study's findings, published in the journal PLOS Biology, offer the hope that a small molecule may be able to convince damaged nerves to grow and effectively rewire circuits.

"This research implies that we might be able to mimic neuronal repair processes that occur naturally in lower animals, which would be very exciting," study senior author Kuo-Fen Lee said in a Salk news release.

A damaged nerve is able to regain function when its long, signal-transmitting extensions, known as axons, grow and establish new connections with other cells.

When the spinal cord is injured, axons are crushed and torn the nerve cells that make up the insulating myelin sheath around axons, begin to die. Exposed axons degenerate, the connection between neurons is disrupted and the flow of information between the brain and the spinal cord is blocked, wrote EuroStemCell.

In a related study conducted by Lee and his colleagues in 2013, they found that the protein p45 promotes nerve regeneration by preventing the myelin from inhibiting regrowth. However, humans, primates and other advanced invertebrates lack this protein. They instead possess a different protein, p75, which binds to the axon's myelin when nerve damage occurs in these animals, halting growth in these damaged nerves.

"We don't know why this nerve regeneration doesn't occur in humans. We can speculate that the brain has so many neural connections that this regeneration is not absolutely necessary," Lee noted.

In the new study, researchers took a closer look at p75. Using nuclear magnetic resonance (NMR) technology, the Salk team found that the growth-promoting p45 could disrupt the pairing of two p75 proteins. When p45 comes into play, it decreases the amount of p75 pairs that bond to inhibitors released from myelin. With less p75 pairs available to bond to inhibitor signals, axons were able to regrow.

The findings suggest that a therapy involving breaking up this p75 pairing - whether it's using p45 or another disrupting molecule - could offer a possible therapy for spinal cord damage.

"Such an agent could possibly get through the blood-brain barrier and to the site of spinal cord injuries," Lee added.