Glaucoma is a group of eye conditions that damage the optic nerve and lead to progressive, irreversible loss of vision. With over 80 million people affected by the condition, glaucoma is the second-leading cause of blindness, behind only age-related macular degeneration.
Although there are several different risk factors, the most understood and treatable risk factor for glaucoma involves controlling the eye’s intraocular pressure, or IOP. When left unaddressed, glaucoma progressively leads to vision loss resulting from damage to axons and associated retinal ganglion cells (RGCs) responsible for transmitting visual information from the eye to the brain. While current treatments for glaucoma are primarily pharmacologic, laser-based, and surgical procedures designed to lower and/or control IOP, they are unable to reverse or restore vision lost as a result of previous damage to the affected axons, RGCs, and the collective optic nerve.
Chanling, Slush, and Zack’s article aim to assess current literature and developments exploring the potential of using human stem cells to further study, and potentially treat, glaucoma and other conditions affecting the optic nerve. For the purposes of this review, the authors divide their discussion into four key areas: stem cell-derived trabecular meshwork cells to control IOP; stem cells as a source of RGCs; stem cell-derived RGCs for transplantation and vision restoration; and stem cells as a source for neurotrophic factors.
Stem Cell-Derived Trabecular Meshwork Cells to Control IOP
Insufficient drainage of the eye’s aqueous humor results in increasing IOP. Current medication for the treatment of this condition reduces aqueous production and or increases aqueous outflow through the trabecular meshwork (TM). Since the TM is a known source of stem cells, researchers hypothesize that these cells and specifically mesenchymal stem cells (MSCs) could be used to repair IOP function and potentially restore vision lost as a result of this condition.
Recent studies have shown promising results, leading researchers to believe that there is a strong possibility of using stem cell-derived TM cells to preserve optic nerve function and reduce IOP.
Stem cells as a Source of RCGs
In addition to assisting with regulating IOP, researchers believe that stem cells may also be able to preserve, and even restore, RCG function – which is ultimately responsible for vision loss caused by glaucoma.
Specifically, the authors point to a number of animal studies that have demonstrated positive responses in a number of signaling pathways and neuroprotective compounds responsible for promoting RNC function and survival. The authors also point out that, while these studies are promising, none have made it to the clinic.
Stem Cell-Derived RGCs for Transplantation and Vision Restoration
While still a relatively new concept, there has been tremendous progress made in the ability to transplant RCEs and photoreceptor cells in the eye. Coupled with the observed differentiation of RGCs, researchers believe the ability to successfully transplant RGCs, with the intent of restoring glaucoma-related vision loss, is not far off.
The authors note that, while these findings are promising, there is still much work and additional research to be completed in this area and that the process of transplanting RCGs is much more complicated than the process used for transplanting retinal pigment epithelial cells (RPEs) and photoreceptors cells.
Stem Cells as a Source for Neurotrophic Factors (NTFs)
Research suggests that deprivation of the NTF required for maintenance and survival of neurons is a leading factor in the progression of glaucoma. As a result, additional research has reported that supplementing additional BDNF and other NTFs, through the use of stem cells appears to support the health and survival of RGC. The authors point out that, while promising, the process required during this procedure is challenging, primarily because it requires the blood-retinal barrier to be circumvented.
The authors of this review conclude that, as a result of the rapidly advancing pace of ocular stem cell research and related ongoing advancements in stem cell technology, there are ongoing opportunities to better understand and improve upon the current glaucoma-related biology and to develop pharmacological models that include cell-based therapies in the effort to restore vision to those affected by glaucoma.
Source: (n.d.). The Potential of Human Stem Cells for the Study and … – IOVS from https://iovs.arvojournals.org/article.aspx?articleid=2518375