Researchers have found a new immune cell with neuroregenerative properties that has potential to help repair serious nerve damage, according to a new study published in Nature Immunology. The team found that the cell, which resembles a common form of white blood cell, promotes the repair of neuronal axons in the central nervous system of mouse models.
Therapeutic options for people with severe nervous system injuries are currently limited. One of the stumbling blocks for treatment is the inability of the body to repair injuries to major nerves. Not only that but damage is usually far too complex for doctors to simply stitch it back together. Potential future therapies for nerve injury range from creating scaffolds loaded with cells that promote nerve growth to inserting computer chips into the site of injury to convey signals from the brain. While the field is promising, it is still in its infancy.
Now researchers from the University of Michigan and Ohio State University believe they have found a new immune cell that may enable transected neurons to regenerate. When tested on mouse models with nerve injury, the cells released a cocktail of growth factors that drove the regeneration of neurons.
"This immune cell subset secretes growth factors that enhance the survival of nerve cells following traumatic injury to the central nervous system. It stimulates severed nerve fibers to regrow in the central nervous system, which is really unprecedented," said Dr Benjamin Segal, a professor and chair of the Department of Neurology at The Ohio State College of Medicine, in a statement.
The research focused on spinal neurons and the neural layer of the retina, a layer at the back of the eyeball that detects entering light before passing the information along the optic nerve to create an image.
To find the special immune cells, the researchers used microscopy and flow cytometry to analyze the cell composition of samples taken from sites of neuron injury. They found high levels of neutrophils around the axons of damaged neurons, a possible indication that neutrophils are driving regrowth.
Neutrophils are the most abundant form of white blood cell and have multiple roles, including the release of pro-inflammatory signals that cause inflammation at infection sites and engulfing pathogens to prevent infection. Within these neutrophils, there's a subpopulation of cells that look similar to immature neutrophils. Upon further analysis, the researchers found that these cells are alternatively activated myeloid cells, meaning they are likely involved with wound healing.
When these cells were injected into a site of neuron injury, they appeared to promote neuron regeneration and survival by secreting an array of growth factors. The results suggest that isolating these cells and targeting them at specific injury sites may be a potential therapy for severe nerve damage.
"In the future, this line of research might ultimately lead to the development of novel cell-based therapies that restore lost neurological functions across a range of conditions," said Dr Segal.
Studies in animal models may not translate to humans in the same way, so more research is needed to confirm the team's findings. The researchers are now looking into ways of stimulating the neuroregenerative cells to migrate to sites of injury as well as investigating how to generate these cells from bone marrow precursors ex vivo.
