Stem cell-based retinal implants have the potential to improve vision in patients with age-related macular degeneration (AMD), according to new reports in Science Translational Medicine and Nature Biotechnology. AMD results from the loss or dysfunction of retinal pigment epithelium (RPE) cells and is a common cause of visual impairment in older individuals.

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“Past studies indicate that stem cell-derived RPE cells are a viable option as a cell replacement therapy for macular degeneration,” comments Amir H. Kashani, the first author of the Science Translational Medicine paper. “Our proposed treatment — a polarized monolayer of RPE cells on a synthetic scaffold — was designed with the intent to replace atrophic or missing RPE cells in patients with advanced dry AMD.”

For their trial, Kashani and colleagues recruited five patients with advanced dry AMD. The team used a retinal implant known as CPCB-RPE1, which consists of human embryonic stem cell (hESC)-derived RPE cells on a synthetic parylene substrate. The implantation procedure was successfully completed in four of the five participants.

Postoperative imaging indicated effective integration of CPCB-RPE1 into the retina. Although the trial was designed primarily to assess the safety of the implant, one of the treated eyes showed an improvement in visual acuity and two showed improvements in visual fixation.

“The results presented in this publication are from a small subset of patients with severe and chronic AMD,” explains Kashani. “On completion of this trial, our plan is to conduct a multicentre trial with a larger cohort of individuals with more visual potential and less severe disease.”

In the second study, reported in Nature Biotechnology, a team led by Lyndon da Cruz at Moorfields Eye Hospital, London, UK, tested a different RPE implant in two patients with another form of AMD, known as neovascular or ‘wet’ AMD. The implant was found to be successfully integrated and well tolerated, and both participants experienced improvements in visual acuity in the 12 months following surgery.

“The results … provide an early indication of the safety and feasibility of manufacturing an hESC-RPE monolayer on a synthetic basement membrane and delivering the patch into the subretinal space as a potential treatment for AMD,” write da Cruz and colleagues. “Our data suggest … efficacy, stability, and safety of the RPE patch for up to 12 months in two patients with severe vision loss from very severe wet AMD.”

The findings of these two studies support further exploration of stem cell-based retinal implants as a treatment for AMD. As the researchers point out, the implants have only been tested in patients with advanced disease so far, and it will be interesting to see whether earlier intervention is more effective.