Nerve cells in our limbs can regenerate after injury, but neurons in the central nervous system, which includes the brain and spinal cord, cannot. Figuring out why this is the case is critical to helping brain and spinal cord injuries heal.

A study published in the January 26 issue of Neuron may offer a promising solution. Not only did the researchers, Rachid El Bejjani and Marc Hammarlund of Yale University, identify what appears to be a key chemical regulator of neuron repair, but drugs that target this regulator already exist, making the path to clinical treatments easier.

The molecule they identified, called Notch, is a receptor that influences many biochemical pathways inside cells. Scientists used to think that Notch was active only during fetal and childhood development, but increasing evidence suggests that Notch is also involved in neurodegenerative conditions such as Alzheimer’s disease and stroke. Using C. elegans, a microscopic worm, El Bejjani and Hammarlund showed that Notch impeded neurons from healing themselves. When they blocked Notch’s activity with a drug, the neurons’ growth improved.

The drug used in the study is already being tested in rodents and humans for potential use in Alz­hei­mer’s and other disorders, although whether it can help damaged neurons regenerate in mammals is unclear. “We know that the Notch pathway is con­served in vertebrates, but we don’t know if the re­generation mechanism is conserved,” Hammarlund says. If Notch stops neurons from growing back in humans as it does in C. elegans, it could be a major breakthrough in spinal cord medicine.

This article was published in print as "Helping Neurons Heal."