Stem Cells derived from a human embryo, have been proved to have caused patients none of the problems scientists feared, such as forming tumours, and reversed partial blindness in about half the eyes receiving transplants, researchers reported on Tuesday. The Lancet had published reports that could help re-invigorate the controversial quest to harness stem cells, which have the ability to turn into any of the 200 kinds of human cells, to treat diseases.

The study “provides the first evidence, in humans with any disease, of the long-term safety and possible biologic activity” of cells derived from embryos, said co-author Dr. Robert Lanza, chief scientific officer of Advanced Cell Technology, which produced the cells and funded the study.

Nine patients with Stargardt’s disease (which causes macular degeneration in childhood) and nine with dry age-related macular degeneration (a leading cause of adult blindness) received implants of the retinal cells in one eye. The other eye served as a control.Four eyes developed cataracts and two became inflamed, probably due to the patients’ age (median: 77) or the use of immune-suppressing transplant drugs. Attention in the field has shifted somewhat to so-called induced pluripotent stem cells, which can be made from skin rather than embryos.

The first clinical trial of a therapy derived from such cells began recently in Japan — to treat a form of macular degeneration. The eye is shaping up to be an early testing ground for various cell therapies, with several trials underway or planned.

One reason is that relatively few transplanted cells are needed. Another is that the eye is shielded to some extent from the immune system, making it less likely that transplanted cells will be rejected. Patients in the Lancet study used immune-suppressing drugs for only 13 weeks, while the recipient of a transplanted organ would most likely require such drugs for life.

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