Macular Degeneration remains the leading cause of irreversible blindness in the developed world. The number of people suffering from this condition is increasing rapidly and medical experts suggest the number of cases will surpass 196 million by 2020.
Fortunately, researchers are making some significant breakthroughs in their quest to find a cure for macular degeneration. Some scientists are using stem cells from umbilical cord tissue to regenerate the macula and restore vision. Here is an update on the latest stem cell research projects focused on macular degeneration.
Understanding macular degeneration
The macula is a small portion of the retina that helps us see things directly in front of us. Light enters the eye, where is received by the macula before being translated into electrical signals. Those signals are sent to the brain via the optic nerve.
The macula is essential for detailed activities that use our central vision, like reading, writing and discerning colours. Macular degeneration can also make it difficult to see in low light conditions and causes the quality of a person’s vision to fluctuate.
As we get older, the cells that make up the macula sometimes fail to function properly. This can lead to a deterioration of central vision over time. Eventually, it can cause permanent blindness. There are two forms of macular degeneration:
1. Dry macular degeneration – With this form of the disease, small yellow deposits called drusen form under the macula. These deposits cause the retinal pigment epithelial cells that form the macula to thin and dry out, leading to vision loss. This form of macular degeneration accounts for about 85% to 90% of cases and progresses slowly.
2. Wet macular degeneration – Wet macular degeneration is caused by the growth of abnormal blood vessels underneath the retina and macula. These blood vessels can break, leaking fluid and causing the macula to change shape. Vision losses usually occur very rapidly in people with this form of the condition.
Age is the most significant risk-factor for age-related macular degeneration. A person who is aged between 50 and 60 has a 2% risk of having the condition, which increases to 30% by the time they are over 75.
Scientists are still unsure about the causes of macular degeneration. However, they believe that certain genetic and environmental factors may be responsible.
Using umbilical cord tissue to treat macular degeneration
Researchers have already discovered that umbilical cord tissue is a valuable source of multipotent stem cells. Multipotent cells have the ability to differentiate into other types of cells, including retinal cells. Many researchers believe that these stem cells can regenerate the cells that make up the macula, halting or even reversing the progression of macular degeneration.
A phase II trial in the United States is currently testing if multipotent stem cells from umbilical cord tissue can safely treat the dry form of macular degeneration. The researchers are converting stem cells from umbilical cord tissue into retinal cells, and then transplanting them into patient’s eyes.
The researchers have developed a specialised catheter to perform the transplant without damaging other components of the eye. They believe that the retinal cells can prevent further loss of the cells that make up the macula, halting the progression of the disease. They are hopeful that it may also restore some vision.
This treatment may be useful for patients who are in the early stages of dry macular degeneration. The study is being carried out by scientists from the UIC College of Medicine and its findings should be released later this year. It is a large national trial that will involve many patients.
Other small scale studies have already discovered that stem cells can halt the progression of macular degeneration. Although these studies have demonstrated positive results, they have only involved a handful of patients. They include:
- Autologous Induced Stem-Cell–Derived Retinal Cells for Macular Degeneration
- CXCL12/SDF-1-Dependent Retinal Migration of Endogenous Bone Marrow-Derived Stem Cells Improves Visual Function
- Pluripotent stem cells: A therapeutic source for age-related macular degeneration
One of the challenges faced by scientists when transplanting stem cells into the eye is cellular rejection. However, various research projects have already found stem cells to be safe web used to treat macular rejection. One such project was performed by Japanese scientists in early 2017.
The Japanese researchers converted donor-derived induced pluripotent stem (IPS) into retinal pigment epithelial (RPE) cells. These RPE cells were then transplanted into monkeys with the dry form of macular degeneration. The cells did not trigger an immune system reaction in the animals.
The same group of scientists has begun a trial that will test the use of IPS-derived retinal pigment epithelial (RPE) cells on humans with dry macular degeneration. This trial started earlier this year and is expected to be completed in 2018.
References
- World Health Organization. (2017). Causes of blindness and visual impairment. [online] Available at: http://www.who.int/blindness/causes/en/ [Accessed 21 Sep. 2017].
- BrightFocus Foundation. (2017). Age-Related Macular Degeneration: Facts & Figures. [online] Available at: https://www.brightfocus.org/macular/article/age-related-macular-facts-figures [Accessed 21 Sep. 2017].
- Parmet, S. (2017). Clinical trial tests cord tissue to treat macular degeneration | UIC Today. [online] News.uic.edu. Available at: https://news.uic.edu/clinical-trial-tests-cord-blood-cells-to-treat-macular-degeneration [Accessed 21 Sep. 2017].
- Commences, S. (2017). Stem Cell Trial for Eye Disease Commences. [online] The Scientist. Available at: http://www.the-scientist.com/?articles.view/articleNo/40976/title/Stem-Cell-Trial-for-Eye-Disease-Commences/ [Accessed 21 Sep. 2017].
- New England Journal of Medicine. (2017). Autologous Induced Stem-Cell–Derived Retinal Cells for Macular Degeneration — NEJM. [online] Available at: http://www.nejm.org/doi/full/10.1056/NEJMoa1608368#t=article [Accessed 21 Sep. 2017].
- Enzmann, V., Lecaudé, S., Kruschinski, A. and Vater, A. (2017). CXCL12/SDF-1-Dependent Retinal Migration of Endogenous Bone Marrow-Derived Stem Cells Improves Visual Function after Pharmacologically Induced Retinal Degeneration.
- Krishnakumar, S. and Parameswaran, S. (2017). Pluripotent stem cells: A therapeutic source for age-related macular degeneration.
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