This is exciting -- many years from being a treatment (if ever) -- but exciting.
Potent protein regenerates damaged eye nerves
15 May 2006 - NewScientist.com news service - A potent molecule that causes more regeneration of eye nerves than any other known has been found by researchers. The damaged eye nerves of rats that received injections of the protein showed five times better recovery than those that did not.
Drugs developed from the newly isolated protein – called oncomodulin – might one day even help heal spinal cord injury in humans. But experts stress that they have not yet tested to see if spinal cells respond to the molecule.
Several years ago, Larry Benowitz of the Children’s Hospital Boston, Massachusetts, US, and his colleagues demonstrated that the inflammatory response triggered by eye injury somehow promoted nerve regeneration in that organ. The body usually shuts down nerve regeneration after injury, probably to prevent erroneous re-connections being made, but the eye seems to be an exception in this instance. Nonetheless, isolating the molecule that promoted this healing remained a tough task.
Using biochemical methods, researchers separated the proteins produced by immune cells called macrophages, which drive the inflammatory response. They then embarked on the time-consuming task of individually testing each of the isolated proteins on nerve cells in a dish. The cells came from the rat retina, part of the back of the eye that translates light into nerve signals.
Among all of the isolated proteins, oncomodulin caused significantly more nerve cell growth than the rest.
Scientists have known about oncomodulin for over two decades, but they have not understood much about its function, according to Benowitz. It was found in tumour cells and the placenta before it was known to be present in the eye. “How you put that all together, we have no idea,” he admits.
Oncomodulin has not yet been isolated in humans, Benowitz explains. But he adds that humans are thought to produce the protein because we have the same gene that rats rely on to make it.
In another part of their most recent experiment, Benowitz and his colleagues mixed oncomodulin with a sugar called mannose and a compound known as forskolin. This combination helps receptors on the outside of cells become sensitised to protein messengers.
Oncomodulin, plus these two helper compounds, caused 45% of retinal nerve extensions – called axons – to grow. This was 50% more growth than that caused by the next best molecule, ciliary neurotrophic factor, or CNTF, under the same conditions.
Researchers also injected oncomodulin into the eyes of live rats with damaged optic nerves, which send signals from the retina to the brain. This increased regeneration of axons of the optic nerve by five times that seen in control rodents.
Benowitz’s team hopes to explore how spinal cells respond to oncomodulin in the future.