Neuroscientists from Case Western Reserve University School of Medicine suggest that a neural network they discovered may help restore diaphragm function after a spinal cord injury, by allowing it to contract without input from the brain.
“Respiratory signals originate in the brain and are relayed to motor neurons in the spinal cord, which then allow the diaphragm to contract. These signals are cut off after cervical spinal cord injury,” says Jared Cregg, Neurosciences graduate student at Case Western Reserve University School of Medicine in Cleveland, first author of a study published recently in Cell Reports.
Constant mechanical ventilation significantly increases a person’s risk of fatal infection. Bacteria can colonize breathing tubes in direct contact with the lungs, leading to pneumonia or septicemia—leading causes of death for spinal cord injury patients. Patients using ventilators can also experience diaphragm muscle atrophy from lack of use, eliminating their chances of ever breathing independently, explains a media release from Case Western Reserve University.
In light of this, Cregg and colleagues Jerry Silver, PhD, and a research team consisting of members of the Spinal Cord and Brain Injury Research Center in the Department of Neuroscience at the University of Kentucky College of Medicine performed the study to try to find ways to reduce patients’ reliance on ventilators.
In the study, mice that underwent complete cervical spinal cord injury were treated with pharmacologic agents enabling the researchers to induce “bursts” of electricity and show they originated in the spinal cord—not the brain.
The researchers then used a laboratory technique called optogenetics to harness the impulses and induce electrical signals in the diaphragm.
In neonatal mouse experiments, C1 spinal cord injuries eliminated brain-derived respiration. But, the researchers discovered electrical signals could still be transmitted from the spinal cord to the diaphragm in these mice. Even with severe spinal cord injury, the mice could maintain intermittent electrical bursts in their diaphragms consistent with breathing patterns. The findings show that the diaphragm can operate via nerve circuitry entirely separate from the brain, the release continues.
“Our results unexpectedly showed that diaphragm motor neurons can be controlled by two independent networks—the classical breathing network in the brain, and a spinal cord network we identify for the first time. Importantly, while previous studies hypothesized that these were parts of the same network, we show that they act completely independently,” Cregg states.
The researchers suggest, per the release, that the neural network may be able to help spinal cord injury patients bypass missing brain signals and restore motor function below injury sites. This could include diaphragm function, to ultimately reduce their reliance on ventilators.
“Our technology is still far out in terms of developing a corollary approach in humans, as our experiments indicating that we can control diaphragm motor output after cervical spinal cord injury were performed in rodent models. The technology will still need to undergo a lot of future development before it could ever be implemented as an approach to solving the human condition,” Cregg cautions.
[Source(s): Case Western Reserve University, Newswise]