Might Stem Cells Be the Long Awaited Cure For Glaucoma?
Glaucoma is known as one of the most common causes of vision loss and blindness in older Americans. Despite its prevalence, there is still no cure for it. While treatments can prevent the disease from worsening, nothing can reverse the damage caused by glaucoma. Scientists are now studying the applications of regenerative medicine to determine exactly how stem cells might be able to contribute to the treatment of glaucoma.
Basic Facts About Glaucoma
Glaucoma forms when the eye’s optic nerve becomes damaged over time and hinders the ability to see clearly. The optic nerve is a small yet vital collection of more than one million nerve fibers responsible for connecting the retina, the light sensitive tissue at the back of the eye, to the brain. In most cases of glaucoma, the optic nerve sustains damage from a buildup of pressure inside the eye called intraocular pressure, which develops when the liquid in the front part of the eye fails to circulate properly. Over time, intraocular pressure prevents the brain from receiving images of what the eye can see, which is why glaucoma leads to vision loss and blindness.
Glaucoma tends to impact people over the age of 40 the most, especially those of African American and Hispanic descent. Though the original causes of intraocular pressure aren’t entirely understood, glaucoma is believed to be a condition passed down genetically. Common symptoms that indicate glaucoma include seeing halos around lights, eye pain, narrowed vision, and vision loss.Though glaucoma cannot be prevented or cured, it can be treated if diagnosed early enough.
Using Stem Cell Secretions to Treat Glaucoma
The current treatments for glaucoma include eye drops, laser surgery, and microsurgery, but researchers at the National Eye Institute (NEI) are now performing research in rodents that could uncover a new treatment method harnessing the power of stem cells.
Mesenchymal stem cells (MSCs) are multipotent stem cells that can differentiate into many different cell types, including bone cells, cartilage cells, muscle cells, and fat cells. Ben Mead, Ph.D, a fellow at the NEI, led a study that set out to isolate the exosome secretions of MSCs. Exosomes can best be defined, according to BioMed Central, as “Extracellular vesicles that are released from cells upon fusion with a plasma membrane.” Mead successfully isolated the exosomes and tested their effects when applied to the damaged optic nerves of rats.
The exosomes, also known as stem cell secretions, were injected into the fluid found in the center of the eye. Each rat received one injection each week, and since Mead and his team stained the exosomes with fluorescent market, they were able to track them as they traveled into the inner retinal layers and retinal ganglion cells.
The Promise of Stem Cell Secretions
After just three weeks, Mead’s team performed a variety of tests of the rats that had been treated with stem cell secretions, including optical coherence tomography, immunohistochemistry, and electroretinography. Their results were dramatic: the optically injured rats treated with exosomes had lost only 30 percent of their retinal ganglion cells, but the untreated rats had lost nearly 90 percent of their retinal ganglion cells. Even further, the retinal ganglion cells treated with exosomes maintained normal functionality and were not compromised by the glaucoma conditions.
The researchers involved in this study reported that exosomes have this protective impact on retinal ganglion cells because the miRNA in the exosomes stops gene expression. Of course, more information is needed to apply stem cell secretions to human treatment. Stanislav Tomarev, PhD, the study’s co-author, stated, “We need to know which particular microRNA – there are more than 2000 different microRNA molecules – are delivered into the retinal ganglion cells and what proteins or signaling pathways are being targeted upon arrival. We also need to attempt to target exosomes to specific sets of neurons and other cell types.”
The NEI will no doubt be pursuing the answers to these additional questions in order to further develop “the use of BMSC-derived exosomes as a cell-free therapy for traumatic and degenerative ocular disease.” Considering that exosomes can be “purified, stored, and precisely dosed in ways that stem cells cannot,” according to Mead, exosome therapy offers unique potential advantages to help prevent vision loss due to glaucoma.
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