Neurons throughout the human body are different and behave differently. Those found in the central nervous system do not heal after injury. Damage caused to either the brain or the spinal cord is of a permanent nature.
A team of researchers at the Washington University School of Medicine, St. Louis carried out a series of experiments on mice to study the working of the nerves in the peripheral nervous system (PNS).
The research gave promising results. The team is hopeful that the neurons in the central nervous system (CNS) might be able to recover after injuries.
Valeria Cavalli, an associate professor of neuroscience in the Department of Neuroscience was a part of the team that conducted the research. She said, “We’ve figured out some of the events that are required for injured peripheral nerves to repair themselves, and we can see that these things fail to happen in the central nervous system. So now we’re trying to see if turning on these networks can help spinal cord neurons regenerate.”
Thousands of people worldwide are victims of spinal cord injury. The US alone has more than 10000 reported cases annually. The cause of the injuries may be varied. Ranging from a sports injury to car accidents the list is ever growing but there is no solution to it.
While the neurons found in the CNS and the PNS are generally the same the main difference is their ability to regenerate.
The neurons that make up the spinal cord and the brain are not programmed to self-heal. Prompt medical care can curtail the injury to a certain degree but the reversal is not possible.
Valeria investigated the functioning of the neurons in the peripheral nervous system. The aim of the study was to find out why the PNS neurons regenerate while the CNS ones don’t. Naturally, the center of her research was the dorsal root ganglion.
Dorsal root ganglion (DRG) is a neuron that spans across both the central and the peripheral nervous system. The DRG has long tendrils known as axons and has 2 branches. One of the branches is linked up with body’s periphery and can heal up. The other side is connected with the cells in the spinal cord and cannot regenerate if injured.
Cavalli, with her team of researchers, performed a series of experiments on mice. The experiments included investigating and understanding the regeneration of the axons and the sciatic nerve.
The sciatic nerve runs through the leg and into the spinal cord. The research proved successful as the team was successful in identifying the particular genes that must be ‘switched off’ so that the axons can regenerate.
“Other people also have shown that a big swath of genes is turned down during regeneration, but as a field, we’ve just said, ‘Eh’ and ignored them to focus on the genes that are activated. Here, we showed that establishing a regeneration program means some genes have to be turned on but a lot have to be turned off.” Cavalli said.
Perhaps the most alarming finding in the experiment was that the neuron can either repair itself or perform the task of a neuron.
“The injured neuron has to stop functioning as a neuron and focus on repairing itself. This means the neuron has to transition back to an immature state so it can re-engage developmental programs and regrow.” Cavalli said.
The idea that cells must become less mature in order to regenerate is not new, but Cavalli and Oh’s study provides evidence in support of that idea. The researchers identified the key molecular and genetic players involved in regressing to a less mature state and showed that the timing of the regression was crucial to successful recovery.
The team is working tirelessly on finding the exact genes which must be turned off for the regeneration. It must also be taken into account that the neuron must be able to act as a neuron afterward too.
“If you’re triggering a system that makes the neuron less mature, you have to make sure it’s not forever. It has to remain a neuron, albeit an immature one, so it can re-mature and start functioning again after it repairs itself.” Cavalli said.
Cavalli commented on the issue saying, “We haven’t found a cure, but we have a better understanding now of what injured neurons do. From here, we can build new hypotheses and work toward applying them to people.”
The team and its work are of pivotal importance in understanding the repair of the central nervous system neurons. This technology might not make it to the commercial market in the next few years but it is a step in the right direction.