Exosomes are what doctors and biologists call microvesicles—tiny spheres of cellular membrane that cells use to communicate with each other. Exosomes are secreted and received by most cells within the body, and carry everything from genetic material and cellular signals to proteins.
Researchers have known about exosomes for quite a while, but only recently started to understand their critical role in retinal health. Most recently, the National Eye Institute released an optimistic report that claims exosomes secreted by stem cells are protective to the retina. This new understanding could break ground for novel glaucoma treatments in the future.
What role do exosomes play in the human eye?
No one knows exactly how many roles exosomes play in the human body, but researchers have been studying the function of exosomes in the eye with particular interest due to their potential use as a drug delivery vehicle or as a therapy in and of themselves. A few studies indicate exosomes are critical in the health of the retina (specifically in the retinal pigment epithelium and retinal ganglion cells) and are essential for cellular repair. But how could these little bubbles of fat be so important to ocular health?
The molecules within exosomes could act as signals to other cells and cause them to change their behavior from business-as-usual to repairing their surroundings—critical to preventing damage from building up within the eye from ocular stress.In one study, researchers found that retinal pigment epithelium cells are constantly under stress, which causes small amounts of damage to the nerve cells in the retina responsible for vision. Conditions like glaucoma also produce cellular damage in tiny amounts at a time. Therapeutically administered exosomes could potentially help decrease glaucoma damage.
Could exosomes be used to treat glaucoma?
In the study by the NEI, researchers fluorescently labeled exosomes and then tracked the cells the exosomes merged with upon their arrival. The result: optic nerve tissue sustained 60% less damage from ethanol when bolstered with added exosomes in comparison to those that weren’t. This is because exosomes in the retina carry microRNAs which are responsible for flipping cellular switches relating to repair.
These findings suggest that supplementing other glaucoma therapies with an exosome treatment might act as an additional guard against vision loss, effectively beefing up the eye’s natural mechanisms for self- repair. The researchers also point out that exosomes are an appealing therapy option for glaucoma in comparison to other speculative treatments like stem cells, because they’re easy to produce, store, and deliver to patients safely via eye drops or injections. There’s even talk about developing a pill that could prompt extra exosome production to help with ocular repair.
Another upside to this potential treatment is that exosomes are also unlikely to cause side effects in and of themselves, as they’re already common in the eye. Unlike eye drops with chemical additives, exosomes won’t cause red eyes, dryness, itchiness, or excessive tearing up when administered.
For now, the biggest barrier between exosomes and the clinic is a lack of research into how exosomes are altered during the course of glaucoma. It’s not clear how exosomes are impacted by the progression of glaucoma, or how exosome supplementation would work long term for patients. Before exosomes can start to displace less comfortable or convenient glaucoma treatments, many studies remain to answer critical questions about their use.
First posted on May 19, 2017; Reviewed on May 12, 2022