For many people, sight is the most imperative of the five senses that help us perceive the environment. Up to 80% of learning and other cognitive activities are performed through vision. Unfortunately, the World Health Organization estimates that almost 39 million people worldwide suffer from blindness. For this reason, numerous researchers and ophthalmologists have been working tirelessly to find innovative treatments for blindness.
In the past, scientists have focused on stem cells (undifferentiated cells that can give rise to specialized cells). The use of stem cells to treat blindness is now an established practice. A new technique, on the other hand, attempts to use algae. Yes, you read that correctly. Chlamydomonas reinhardtii are simple, unicellular green algae that can be found in water and dirt. These eukaryotes are not only drastically different from humans, they also have poor eyesight. How eyeronic! These algae have a primitive eye or eyespot that detects sunlight, which is essential for the process of photosynthesis. Their eyespot contains the same light-sensitive proteins that are also found in human eyes. One of these algal proteins is called channelrhodopsin-2. If it were implanted into the retina of a blind patient, it could potentially restore their eyesight. Although the process may sound unbelievable, it has proven to be plausible. In fact, RetroSense Therapeutics—a company native to Ann Arbor, Michigan—began human clinical trials in August 2015 to test this development. This American organization chose fifteen patients who suffered from retinitis pigmentosa, a genetic eye diseases that caused the deterioration of the rods and cones—the photoreceptors that allow us to see—in the eye. Nevertheless, the whole process is a little bit more complex than simply inserting channelrhodopsin-2 into the patients’ retina. In practice, a virus is used to insert copies of the channelrhodopsin-2 gene into the neurons of the retina and then translated into corresponding proteins. Neurons, generally, do not respond to light. However, once these channelrhodopsin-2 proteins are embedded within the neurons, researchers can then provoke brain circuits with light. This technique—using light to control cells in living tissues—is called optogenetics. Specifically, once light passes through the layers of neurons and hits the light-sensitive cones and rods in the retina, electrical signals are sent through the interconnected webs of neurons to the brain. Since the last layer of neurons are targeted and will become light sensitive when the channelrhodopsin-2 protein is inserted, the front, damaged layers of neurons in visually impaired eyes can be bypassed. Another reason why this method is more complicated than it seems is because there are millions of retinal ganglion cells that comprise the last layer of the eye. It is difficult to introduce channelrhodopsin-2 into enough of these cells to successfully revive the patient’s vision.
Insertion of this algal protein is not easy… but it is possible. On March 21st, 2016, RetroSense announced some promising news: the trial’s first patient was successfully given the channelrhodopsin-2 (the company refers to it as RST-001). Although all those involved agreed this is a major milestone, they are aware success is not guaranteed. David Birch, Ph.D and executive officer of the Retina Foundation of the Southwest, acknowledged this, saying that “patients enrolling in the trial understand that we are exploring brand new territory but are excited about the possibility of restoring some vision.” Those interested in this topic can visit the company’s website (www.retro-sense.com) to keep updated on the progress of this clinical trial.
April 4, 2016
Author: Simran Dhadda
Editor: Annie Yu