Understanding Macular Degeneration
Prevalence and Impact
Macular degeneration is a significant cause of vision loss among older adults, affecting nearly 10% of Americans over the age of 50. This condition arises from the death or dysfunction of cells in the macula, the central region of the retina responsible for high-resolution vision critical for tasks like reading and driving. As the disease progresses, individuals often experience a decline in central vision while their peripheral vision remains intact.
Potential for Cell Replacement Therapy
Researchers have hypothesized that replacing dead macular cells could slow down or potentially reverse the disease’s progression.
The London Project to Cure Blindness
Innovative Clinical Trial
Recently, a group of doctors in the United Kingdom conducted a phase I clinical trial, surgically implanting replacement cells derived from human stem cells into the eyes of two patients diagnosed with “wet” macular degeneration, the most severe form characterized by leaky blood vessels. The findings were published in the scientific journal Nature Biotechnology.
Stem Cell Characteristics
Human stem cells, which can be harvested from early-stage embryos, possess the capability to grow indefinitely in laboratory settings and can develop into various cell types in the body. For this study, researchers isolated stem cells that had differentiated into retinal cells, ensuring their suitability through rigorous testing.
Preparation of the Retinal Cell Patch
The retinal cells were implanted into laboratory animals, including mice and pigs, to confirm their safety and prevent tumor development. Once verified, these cells were cultivated on a specially-treated polyester membrane, forming a patch that mimicked the living surface of the eye.
Surgical Procedure and Follow-Up
The trial involved two patients, aged 60 and 84, who had recently experienced significant vision loss due to wet age-related macular degeneration. The surgical procedure, lasting one to two hours under general anesthesia, involved inserting the cell patch beneath the retina. A follow-up operation occurred ten weeks later under local anesthesia. Patients received anti-inflammatory medication for three weeks post-surgery, and an implant was placed in the eye to release additional anti-inflammatory drugs, minimizing the risk of rejection.
Monitoring and Results
Adverse Events
Patients were monitored for one year to assess any adverse effects and improvements in vision. Both individuals experienced serious complications requiring further surgery. However, these issues were attributed to the anti-inflammatory treatment and surgical procedures rather than the implanted patch or the stem cell-derived retinal cells.
Vision Improvements
One year post-surgery, the implanted cells remained functional. Notably, both patients reported significant enhancements in their vision. Visual acuity, assessed using an eye chart, improved markedly, with one patient’s reading speed increasing from 2 to 83 words per minute and the other from 0 to 80 words per minute. One patient expressed joy at being able to read the newspaper and tend to his garden once again.
Future Considerations
Researchers aim to continue monitoring these patients for several years to determine if the vision improvements are sustained and to identify any potential long-term side effects. It remains to be seen whether this procedure can benefit individuals with milder forms of age-related macular degeneration.
Conclusion
Overall, the initial results of this study are promising. Researchers hope to expand the trials to include more patients, with the aspiration that this innovative surgical technique could become a routine treatment option for age-related macular degeneration within five years.
References
(1) da Cruz, L., et al. “Phase 1 clinical study of an embryonic stem cell–derived retinal pigment epithelium patch in age-related macular degeneration.” Nature Biotechnology (2018).
(2) Rimmer, A. “Patients with severe wet AMD regain vision after stem cell treatment.” BMJ 360 (2018).
(3) Mehta, S. “Age-Related Macular Degeneration.” Primary Care: Clinics in Office Practice 42, 377-391 (2015).