The phase I/II trial looked at the safety of transplanting hESCs into two people with different types of eye disease: one person with Stargardt's macular dystrophy and one person with dry age-related macular degeneration (AMD). The researchers found no signs of rejection or abnormal cell growth indicating that hESCs may one day be safely used for therapeutic use in humans.
Researchers at Advanced Cell Technology, a biotech company which develops stem cell-based technologies, along with the Jules Stein Eye Institute at the University of California, Los Angeles, cultivated the hESCs using mouse skin cells into cell types found inside the eye. The cells were then purified and subsequently injected into specific locations within the eye.
'The cells seem to have transplanted into both patients without abnormal proliferation, tumour formation, graft rejection or any untoward pathological reactions or safety signals', the researchers said. However, they added that follow-up studies were needed to further establish the safety of the procedure.
After the injections of stem cells, the patients also demonstrated a functional improvement in their vision. The patient with Stargardt's macular degeneration could previously only determine hand motions, but two weeks after the injections they could reportedly count fingers using their treated eye. The patient with AMD also reported an improvement in vision, although the researchers could not see that the cells had survived the procedure.
Professor Daniel Brison, co-director of the North West Embryonic Stem Cell Centre, Manchester, described the results as a 'very exciting moment for embryonic stem cell therapies'.
'Although the study is limited to safety considerations, very small in scope, and at a very early stage, this is nonetheless a ground breaking moment for embryonic stem cell therapies', he said.
Professor Chris Mason, chair of Regenerative Medicine Bioprocessing, University College London described the findings as 'only the start of gathering the necessary safety data before it is possible to test if the therapy will have an impact on patients' vision'.
'Overall the process of testing for safety and efficacy is likely to take a minimum of 5-10 years before the potential therapy could enter routine clinical practice', he said.
The study was published in the Lancet.