A newly-identified therapeutic target could lead to a more effective treatment of glaucoma, researchers say.
Glaucoma is a neurodegenerative disease that causes vision loss and blindness due to a damaged optic nerve. Glaucoma affects more than 200,000 people in the United States each year. Unfortunately, there is currently no treatment.
The researchers found neurons use mitochondria for a steady source of energy, and restoring mitochondrial homeostasis in the diseased neurons can protect the optic nerve cells from damage.
“Age-related neurodegenerative disease, which includes glaucoma, Parkinson’s disease, and amyotrophic lateral sclerosis (ALS), is the biggest global health problem,” says Arupratan Das, assistant professor of ophthalmology at Indiana University and principal investigator of the study in Communications Biology.
“The fundamental mechanisms that we discovered can be used to protect neurons in glaucoma and be tested for the other diseases. We have identified a critical step of complex mitochondrial homeostasis process, which rejuvenates the dying neuron, similar to giving a lifeline to a dying person.”
The researchers used induced pluripotent stem cells (iPSCs) from patients with and without glaucoma as well as clustered regularly interspaced short palindromic repeats (CRISPR) engineered human embryonic stem cells with glaucoma mutation.
Using stem cell differentiated retinal ganglion cells (hRGCs) of the optic nerve, electron microscopy, and metabolic analysis, they identified glaucomatous retinal ganglion cells suffer mitochondrial deficiency with more metabolic burden on each mitochondrion. This leads to mitochondrial damage and degeneration. Mitochondria are the tube like structures in cells which produce adenosine triphosphate, cell’s energy source.
However, the process could be reversed by enhancing mitochondrial biogenesis by a pharmacological agent. The team showed retinal ganglion cells are highly efficient in degrading bad mitochondria, but at the same time producing more to maintain homeostasis.
“Finding that retinal ganglion cells with glaucoma produce more adenosine triphosphate even with less mitochondria was astonishing,” Das says. “However, when triggered to produce more mitochondria, the adenosine triphosphate production load was distributed among more mitochondrion which restored the organelle physiology.
“It is similar to a situation where a heavy stone is carried by fewer people versus a greater number of people—each person will have less pain and injury, just like each mitochondrion will have less difficulty and damage.”
In the future, Das would like to test if these mechanisms protect the optic nerve in animal models under injury before testing in humans to hopefully lead to new clinical interventions.
Source: Indiana University
