The brake which halts the growth of young nerve fibers in adult mammals can be released by genetically inhibiting or abolishing a particular enzyme in the injured nerve cells. The work, online in Nature Neuroscience this week, suggests that targeting these enzymes may be beneficial to treat spinal cord injury.
Zhigang He and his colleagues studied a model of spinal cord injury in mice, and found that the activity of the growth- promoting enzyme mTOR was very low in injured adult neurons in the corticospinal tract. Increasing mTOR activity by genetically blocking its regulator, the enzyme PTEN, increased both the sprouting of the remaining intact nerve fibers and the ability of the injured nerve fibers themselves to re-grow and reconnect with nerve cells below the injury.
The authors did not examine whether the new connections formed by these regenerating nerve fibers translate to functional recovery or improved mobility and it remains to be seen if these findings can be effectively translated to humans. Nonetheless, this work suggests that drugs targeting the regulatory mechanisms that limit mTOR activity in the adult nervous systems may be beneficial to treat spinal cord injury