Could Lost Retinal Cells Be Replaced?
Age-related macular degeneration (AMD) is a leading cause of vision loss, affecting the central vision people use for reading, driving, and recognizing faces. In dry AMD, specialized cells in the back of the eye gradually become damaged or lost, contributing to worsening vision over time.
A first-in-human clinical trial explored an exciting question: Could researchers replace some of these lost cells with healthy ones grown in a laboratory?
Researchers tested retinal pigment epithelium (RPE) progenitor cells made from adult retinal stem cells. These cells were transplanted beneath the retina with the goal of supporting an area of the eye affected by advanced dry AMD.
How Did the Study Work?
This Phase I/IIa trial is evaluating a cell therapy known as RPESC-RPE-4W. The cells originated from donated adult eye tissue and were grown in the laboratory before being developed into the type of RPE cells needed to support the retina.
This early report focused on the first six participants, each of whom received 50,000 cells in the eye with more advanced disease.
Researchers primarily wanted to answer two questions:
- Could the cells be transplanted safely?
- What happened to participants’ vision afterward?
Three participants entered the study with more advanced vision loss, while the other three began with better vision.
An Encouraging Change in Vision
Some of the most interesting results appeared in the participants who started with poorer vision. After 12 months, these three participants improved by an average of approximately 21.7 letters on a standardized eye chart.
Across all six participants, treated eyes had improved by an average of 11 letters at six months. The group that began with better vision experienced smaller improvements during the available follow-up period.
These results are especially interesting because improving vision was not the primary goal of this early phase of the trial. Researchers were first focused on determining whether the treatment could be performed safely.
What Did Researchers Find About Safety?
The initial safety results were encouraging. Researchers reported:
- No tumors
- No significant inflammation
- No serious adverse events related to the cell product
The trial met its primary safety goals for this first low-dose group. Based on the results, the study’s independent safety committee allowed researchers to move forward to a higher dose of 150,000 cells.
Why Are These Cells Important?
RPE cells may not be the cells that directly allow us to see, but they play an essential supporting role. They help maintain and protect the light-sensing cells of the retina that make vision possible.
As dry AMD progresses, losing these support cells can contribute to further retinal damage. The idea behind this therapy is different from simply trying to slow the disease, it aims to replace cells that have already been lost. That is what makes this study particularly interesting from a regenerative medicine perspective.
A Small Study With an Interesting Future
These findings are still very early. Only six people were included in this first report, there was no placebo group, and larger studies will be needed to determine how consistently the treatment works.
Still, this first group provided encouraging signs. The transplanted cells met the study’s initial safety goals, while some participants also experienced notable improvements in vision.
As researchers continue testing higher doses and following more patients, this study offers an intriguing glimpse at a future where regenerative medicine may help address vision loss by replacing damaged or missing cells in the eye.
Source
Rao RC, Arduini BL, Borden S, et al. Safety and tolerability of RPESC-RPE transplantation in patients with dry age-related macular degeneration: Low-dose clinical outcomes. Cell Stem Cell. 2025;32(11):1659–1670.e4. doi: 10.1016/j.stem.2025.08.012. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC12533590/
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