Stanford University scientists have partially restored vision to mice thought to have lost it permanently in an approach that could eventually lead to the restoration of vision in humans.
The team worked with mice whose optic nerves had been completely severed, mirroring the effects of glaucoma in humans, a leading cause of blindness in humans for which there is no cure, according to a statement. Ganglion nerve cells make up the optic nerve and, unlike nerve cells outside the central nervous system, do not regenerate if damaged.
In an attempt to induce these cells to regenerate, the scientists either exposed mice with one crushed optic nerve to daily visual stimulation comprising moving images of a black-and-white grid, used undisclosed "biochemical manipulations" to reactivate their mTOR pathway, the downregulation of which impairs the regenerative ability of the retinal ganglion cells, or treated them with both options.
Three weeks later, they examined the mice’s brains for regrowth of retinal ganglion axons as well as their reactions to visual stimuli. They found that while each of the treatments alone induced some regeneration, it was limited, and the axons didn’t reach the parts of the brain, which is required to regain sight. But when the treatments were combined, “substantial numbers” of axons grew, retracing their steps to the appropriate regions of the brain.
While vision was restored according to some tests, the mice failed other tests, suggesting only partial restoration, the team said. Next, they will focus on increasing the number of retinal ganglion axons that grow back into the brain and re-establish connections with target brain regions. They will also seek ways to target more or all of the 30 different subtypes of retinal ganglion cells.
- here's the statement
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