Embryonic stem cells can be turned into a therapy to help the sight of the nearly blind. Stem cells injected into the eyes of blind patients have cured them for the first time with no side effects. The breakthrough has proved safe three years after patients were injected with stem cells derived from human embryos.
In a report published in the journal Lancet, scientists led by Dr. Robert Lanza, chief scientific officer at Advanced Cell Technology, provide the first evidence that stem cells from human embryos can be a safe and effective source of therapies for two types of eye diseases—age-related macular degeneration, the most common cause of vision loss in people over age 60, and Stargardt’s macular dystrophy, a rarer, inherited condition that can leave patients legally blind and only able to sense hand motions.
This is the first time that clinical benefits have been demonstrated in the medium to long term in patients with any disese treated with hESC-derived cells, and is a major milestone in the development of the field of regenerative medicine. It’s an achievement that is due to many years of animal research.
Follow-up testing showed that 10 out of 18 treated eyes had substantial improvements in how well they could see, with 8 patients reading over 15 additional letters in the first year after transplant.
Visual acuity remained the same or improved in seven patients, but decreased by more than 10 letters in one patient. Importantly, untreated eyes did not show similar visual improvements.
"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," said lead author professor Robert Lanza, chief scientific officer at Advanced Cell Technology in the USA.
"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 two phase studies, hESCs were differentiated 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, the leading causes of juvenile and adult blindness in the developed world, respectively.
No effective treatments exist for either condition and eventually the light-receiving (photoreceptor) cells of the retina degenerate leading to complete blindness. All participants were injected with one of three different doses of retinal cells (50000, 100000 and 150000 cells) into the sub retinal space (under the retina) of the eye with the worse vision.
The hESC-derived cells were well tolerated for up to 37 months after transplantation. No safety concerns (hyper proliferation or rejection) in the treated eyes were detected during a median follow-up of 22 months.
Co-author professor Steven Schwartz from the Jules Stein Eye Institute, Los Angeles added "Our results suggest the safety and promise of hESCs to alter progressive vision loss in people with degenerative diseases and mark an exciting step towards using hESC-derived stem cells as a safe source of cells for the treatment of various medical disorders requiring tissue repair or replacement".
About half of the patients had an improvement in visual acuity of three lines or more, which corresponds to a doubling of the visual angle, and is generally accepted as clinically significant," Dr Lanza said.
One 75-year-old rancher from Kansas, who was effectively blind in one eye before the treatment, improved to such an extent that he was able to ride a horse again. Other patients reported that they could use their computers or could go shopping, Dr Lanza said.
“Our goal was to prevent further progression of the disease, not reverse it and see visual improvement,” says Lanza. “But seeing the improvement in vision was frosting on the cake.”- TNN
No comments:
Post a Comment