You might have caught the reference to something called “optogenetics” in a January episode of the hit CBS series Limitless. Next month, a clinical trial in Texas will test whether optogenetics can restore vision to individuals with the degenerative disease retinitis pigmentosa. Whether this trial is successful will have implications far beyond the treatment of blindness.
Optogenetics is a technique where light-sensitive proteins (e.g., from algae) are inserted into cells that are not normally light-sensitive, such as an animal’s neurons. The modified cells can then be controlled by simply shining the correct type of light onto the cells. Optogenetics has generated a lot of interest among researchers in recent years, and experiments in animals such as mice and monkeys have demonstrated how the technique can potentially be used in a wide variety of ways, from treating Parkinson’s disease to implanting false memories. A major hurdle in adapting optogenetics for use in humans, however, is that the technique often requires invasive procedures to insert fiber optic cables into the organism in order to shine light onto a specific group of cells.
In this planned clinical trial in Texas, the problem of light delivery is avoided by using the technique on the eyes, which are naturally transparent and exposed to light. By packaging the genes that encode for the light-sensitive proteins into harmless viruses, and injecting the viruses into a patient’s eyes, the hope is that the gene will be delivered to nerve cells called ganglion cells, and turn these cells into light-sensitive cells and partially restore the patient’s vision.
If this trial is successful, it will be a major boost to the field of optogenetics, giving hope to neuroscientists and patients who wish to use this technique to tackle a variety of neurological and, perhaps, psychological conditions.
In recent years, the eye has been a popular target for gene therapy (the treatment of disease by modifying a cell’s DNA), largely because the eye is partially shielded from the body’s immune system, thus minimizing the chance of an immune response to the viruses used to deliver the therapy. Last October, promising results were reported for another clinical trial for gene therapy in the eye. Unlike the planned optogenetics trial, that ongoing clinical trial aims to directly restore the function of light-sensing retinal cells by delivering working copies of the defective gene into them.