Richard Kramer, from the University of California, Berkeley, has discovered a method of returning photo sensitivity to blind mice. By injecting a particular chemical into the mice, Kramer claims to have been able to repair ganglion cells in their eyes, so that they now respond to lighting changes. Ganglion cells are responsible for carrying signals from cones and rods to the brain, in mice and in humans. Consequently, there is hope that this drug therapy could be used to return vision to people whose light sensitive eye cells have been compromised, or have deteriorated with age.
Kramer’s initial discovery, with a different drug, only returned sensitivity to ultra violet light. Upon further investigation, a drug was created that worked for visible light wavelengths. Only 6 hours after injection, the previously blind mice showed the same responses to light as fully sighted animals. It is currently unknown whether these mice have regained full vision, or simply the ability to detect changes in lighting. This discovery will certainly have triggered interest in the idea, and should inspire further experiments to be conducted.
When the effects on the retinal cells of the mice were studied in more detail, it became apparent to researchers that the drug repaired compromised cells and left healthy ones unaffected. “That’s what’s particularly remarkable and hopeful about this,” says Kramer. “It’s possible that if you put this drug in a partially [affected] eye it would restore vision to the [affected] regions and leave the healthy areas unaffected”.
Gene therapy is another technique that has seen recent success in repairing eyesight. By modifying a person’s genes, some types of inherited diseases can be prevented or reversed. This therapeutic procedure could also have the potential to repair eyesight caused by age related macular degeneration. A ‘vector’, which in most cases is a virus, is used to insert a correctly functioning gene into a cell which contains a defective gene. This method of gene therapy can be applied to many different types of cell, and therefore has the potential to cure myriad other diseases. The only issue with gene therapy is that the long term effects are unknown and may be permanent.
Another alternative idea for repairing eyesight is stem cell treatment. Last year, research at University College London was conducted by Robin Ali into the matter. Ali’s experiment used embryonic stem cells to created light sensing cells, which were then transplanted into the eyes of blind mice.
Both gene therapy and stem cell treatment are being pursued in further research, though it is hoped that drug therapy will also become more prominent. One of the key benefits that Kramer claims for his new drug therapy idea, is that any side effects would probably be reversible, unlike in other types of treatment. The process of injecting someone with a drug is also much simpler than the potential alternatives.
Further research into the use of drug therapy will undoubtedly be required before it can make any meaningful contribution to modern medicine. Regarding Kramer’s research, Professor Ali commented that: “The light responses that are generated could be very noisy […]. Or perhaps the brain could learn to interpret the new information. [Though] this needs to be demonstrated.”
If Kramer’s research results in the successful repairing of eye cells in humans, how many other experiments into drug therapy might he have inspired? What other potential benefits might these experiments find in the use of drug therapy?