Stem Cells Restore Vision in Lab Study of Retinal Disease
In a research paper recently published in the Proceedings of the National Academy of Sciences, investigators from the University College of London (UCL) reported on their successful integration of stem cell transplants in six mouse models of retinal disease, including those for retinitis pigmentosa (RP), Leber congenital amaurosis and congenital stationary night blindness (CSNB). The most successful transplantation results were observed in mice with CSNB, which were completely blind before having their vision restored.
The knowledge gained from the study is valuable in planning and designing forthcoming clinical trials of stem cell therapies for people with these and other inherited retinal conditions.
The scientists noted that neither the severity nor rate of retinal degeneration were consistent factors in the success of the transplantation across the different models. In some models, including the CSNB mice, cell integration was more effective at a late stage of disease. In other models, integration was more successful at an early stage.
The investigators did, however, identify two factors related to retinal structure that were common to transplantation success across all models: 1) disruption of the outer limiting membrane (OLM); and 2) minimal scarring of Müller glial cells.
The OLM is a seal between the light-sensing outer segments of photoreceptors, the cells that make vision possible, from the inner portion of the retina. Their research showed that when the seal is broken from degeneration, transplanted stem cells can more effectively migrate and integrate where they are needed to restore vision.
Müller glial cells, located in the inner retina, have a broad-ranging role in photoreceptor health, including waste removal and recycling, as well as maintenance of the retina’s structure. Scarring appears to limit the ability for Müller glia to perform these critical tasks.
“Integration is the biggest hurdle as clinicians move toward human studies of stem cells for transplanation to restore vision,” says Dr. Stephen Rose, chief research officer, Foundation Fighting Blindness. “The important knowledge being gained by UCL and other research groups in the field is moving us closer to where we need to be. We are very excited about the progress being made.”
Through its Translational Research Acceleration Program, the Foundation Fighting Blindness is funding Dr. David Gamm, of the University of Wisconsin-Madison, and Dr. Thomas Reh, of the University of Washington, to address the same stem cell transplantation challenges and prepare for clinical trials.
Also, the U.K. company ReNeuron, in collaboration with Dr. Michael Young, of Massachusetts Eye and Ear Infirmary at Harvard University, is planning to launch a clinical trial of its stem cell treatment for people with RP in late 2013.
Two companies have stem cell clinical trials underway for retinal diseases. Advanced Cell Technology (ACT) and StemCells, Inc. are currently conducting early-stage clinical studies of stem cell treatments for people with dry age-related macular degeneration. ACT’s treatment is also being evaluated in a clinical trial for people with Stargardt disease.