While the majority of tissues in the human body can regenerate after injury, some of the most important ones can’t. That includes axons, the long nerve fibers that pass signals between neurons. But now, researchers at Temple University have found that boosting a certain protein helps patch up axons, returning more movement and feeling to mice with spinal cord injuries.
Axons are the long nerve fibers that protrude from neurons, acting like electrical cables that shuttle signals around the body. They’re a crucial conduit for the brain to issue instructions to muscles, as well as for tissues to report back pain and other touch sensations. But despite their importance, axons don’t recover from damage, which is why spinal injuries are so debilitating.
Now the Temple team may have uncovered a potential new target for treatment. The key is a protein called Lin28, which is expressed in high amounts in embryonic stem cells before it drops off later in life. In past studies, ramping up levels of Lin28 has been found to help mice regrow skin, bone, cartilage and other tissues. In the new study, the researchers tested whether it could also help repair damaged axons.
First the team engineered mice that overexpressed Lin28 in certain tissues. When these mice were fully grown, they were then given injuries to the spinal cord or the optic nerve, which connects the eye to the brain. In another group, mice with normal Lin28 production were given injections of the molecule after the same injuries.
The researchers found that across the board, the extra Lin28 helped axons regenerate, spreading as far as 3 mm beyond the damaged area in the spinal cord, and along the entire optic nerve tract. Interestingly, the injections seemed to be the most effective method, restoring more coordination and sensation to the mice with injured spinal cords.
"Our findings show that Lin28 is a major regulator of axon regeneration and a promising therapeutic target for central nervous system injuries," says Shuxin Li, senior investigator on the study. "We observed a lot of axon regrowth, which could be very significant clinically, since there currently are no regenerative treatments for spinal cord injury or optic nerve injury.”
Next, the researchers want to investigate ways to deliver the Lin28 molecule to human patients. Other related growth signaling molecules could also be bundled together with Lin28 for even better results, the team says.
The research was published in the journal Molecular Therapy.
Source: Temple University
