A Pro-Regenerative Form of Neutrophil Encourages Nerve Regrowth
Researchers have identified a subset of the population of the immune cells called neutrophils that can promote nervous system regeneration. Nerves are one of the least regenerative tissue types, and thus numerous research groups are in search of ways to promote nerve regeneration following injury, or to promote better maintenance of nervous system tissue in later life. The example here is an interesting one; the immune system is deeply involved in regeneration, and it makes sense for there to be ways to manipulate that relationship, even quite crudely, such as by finding specific classes of immune cell and increasing their numbers in injured tissue.
Using a mouse model, researchers discovered a new type of immune cell that not only rescues damaged nerve cells from death, but partially reverses nerve fiber damage. The research team also identified a human immune cell line, with similar characteristics, that promotes nervous system repair. "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."
The cell discovered by these researchers is a granulocyte, a type of white blood cell that has small granules. The most common granulocytes, neutrophils, normally help the body fight off infection. The unique cell type resembles an immature neutrophil but is distinctive in possessing neuroprotective and neuroregenerative properties. It drives central nervous system axon (nerve) regrowth in vivo, in part through the secretion of a cocktail of growth factors. "We found that this pro-regenerative neutrophil promotes repair in the optic nerve and spinal cord, demonstrating its relevance across central nervous system compartments and neuronal populations. A human cell line with characteristics of immature neutrophils also exhibited neuroregenerative capacity, suggesting that our observations might be translatable to the clinic."
Researchers demonstrated the therapeutic potency of the immature neutrophil subset by injecting them into mice with crush injury to the optic nerve or lacerated nerve fibers in the spinal cord. Mice injected with the new neutrophil subset, but not more typical mature neutrophils, grew new nerve fibers.
Link: https://www.eurekalert.org/pub_releases/2020-10/m-don101920.php