Since they were first separated in 16 years ago, human embryonic stem cells have been thought to have enough capacity to replace the bodys worn-out tissues and cure numerous deadly eye diseases. The improvement has been quite slow,however scientists are confident of an innovative measure.
A therapy for eye diseases that was derived from stem cells appeared to be safe and might have improved the vision of some patients, according to a new study.
The results, published on Tuesday evening by the journal The Lancet, represent the most extensive human data yet on any treatment derived from such embryonic stem cells. The 18 patients in the study were followed for a median of 22 months, two of them for more than three years.
This is a promising study, and it provides a lot of hope for regenerative medicine, said Dr. Steven D. Schwartz, a retina specialist at the University of California, Los Angeles, and the lead author of the paper. However, theres a lot of work to be done.
Embryonic stem cells, from a woman with Type 1 diabetes, were induced to turn into insulin-making beta cells, in hopes they could be implanted to cure the disease.
Human embryonic stem cells have been the focus of pitched ethical and political battles because they are typically created by destroying human embryos. Advanced Cell Technology, the company that sponsored this study, says it can create embryonic cells without destroying embryos, although at least one embryo was destroyed for the stem cells used in this study.
Stem cells, which can be turned into any type of cell in the body, could become a source of replacement tissue. But there has been concern that such cells, once put into the body, might turn into unwanted types of cells ” bone cells in the eye, for instance ” or form tumors.
In this study, that did not happen. If it had, it could have set the field back.
Advanced Cell Technology transformed embryonic stem cells into retinal pigment epithelium cells, which provide support for the light-sensing cells in the eye.
These pigmented cells were implanted in a short surgical procedure into one eye in each of the 18 patients. Half the patients had the dry form of age-related macular degeneration, and the others had another degenerative retinal disease called Stargardts macular dystrophy.
Vision improved by what is considered a significant amount in eight of the 18 treated eyes. By comparison, the untreated eyes of those same patients did not show an improvement.
Dr. Robert Lanza, the chief scientific officer of Advanced Cell Technology, said one rancher was able to ride his horse again. Another patient, a man, cried and hugged me, he said.
But outside experts said the improvements might have been caused not by the transplanted cells but by the procedure, the cataract surgeries some patients also had or a placebo effect, since patients knew which eye was treated.
You stick a needle in a mouse eye, you get an effect, said Dr. Martin Friedlander, a professor of cell and molecular biology at the Scripps Research Institute. You cant really say anything about efficacy at this point.
The researchers said pigment levels increased in 13 eyes, a sign that the transplanted cells might have taken up residence, but increased pigment did not correlate with improved vision. And some other measures of retinal health did not improve.
Its not to the point where its going to make me jump up and down for joy, Steve Rose, chief research officer at the Foundation Fighting Blindness, said of the data. He noted that while the cells themselves were apparently safe, there were side effects from the immune-suppressing drugs taken to prevent rejection of the cells as well as an infection from the surgical procedure.
Dr. Schwartz and Dr. Lanza were criticized by their colleagues for premature optimism when they published an earlier paper on this study in early 2012, after only two patients had been treated and followed for only a few months.
The trial is one of only a few involving human embryonic stem cells. Asterias Biotherapeutics is planning a trial in patients with spinal cord injury, following up on a trial that was halted in 2011 by a different company, Geron. ViaCyte will soon begin testing insulin-producing cells derived from embryonic stem cells as a treatment for Type 1 diabetes.
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 of the major reason why few transplanted cells are actually needed. Then the eye is shielded to a great extent from the immune system, turning into least possibility that transplanted cells will be unaccepted. Patients in the Lancet study utilized immune-suppressing drugs for about 91 days, while the recipient of a transplanted body organ will most likely need such drug dosage for life.