New study shows implanted human stem cells are still safe 3 years later

Research recently published in the medical journal The Lancet, gives documentation on the medium to long-term safety and immune system tolerability for clinically using human embryonic stem cells (hESCs) in human patients.

The stem cells were implanted in 18 patients who had different forms of macular degeneration, and the transplants are deemed to still be safe three years after the transplant. The stem cell technology restored at least some level of sight in more than half of the patients.

“Embryonic stem cells have the potential to become any cell type in the body, but transplantation has been complicated by problems including the risk of teratoma formation and immune rejection,” lead author Professor Robert Lanza, chief scientific officer at Advanced Cell Technology, said in a news release. “As a result, immunoprivileged sites (that do not produce a strong immune response) such as the eye have become the first parts of the human body to benefit from this technology.”

In the initial experiments, hESCs were imbedded into retinal pigment epithelium cells and transplanted into nine patients with Stargardt’s macular dystrophy and nine patients with dry atrophic age-related macular degeneration, which are the leading causes of juvenile and adult blindness in the developed world, the release says. Besides the stem cell experiment results, researchers know of no documented effective treatments existing for either condition, which eventually causes the photoreceptor cells of the retina degenerate leading to complete blindness.

Each participant was injected with one of three different doses of retinal cells, ranging from 50,000, 100,000, and 150,000 stem cells, under the retina of the eye with worse vision.

Follow-up testing showed that 10 out of 18 treated eyes had noticeable improvements in how well they could see, with 8 patients reading , more than 15 additional letters in the first year after transplant. The visual abilities either stayed the same or roughly improved in seven patients, but decreased by more than 10 readable letters in one patient. Conversely, untreated eyes did not show similar visual improvements.

However, it took a while for these events to cut through the noise of public discourse, and educate people on the potential uses of these stem cell treatments.

“The work … is a major accomplishment, but the path to get to this point has not been smooth. Since the discovery of hESC in 1998, much has transpired, including political, ethical, and scientific debates, with an overall push to achieve the promise of human therapies,” said, Anthony Atala, director of the Wake Forest Institute for Regenerative Medicine, said.  “Much work remains to be done before hESC and induced pluripotent stem cell therapies go beyond regulatory trials, but the path is now set in motion.”

Information for this report is via a news release from Science Daily.

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