Stem Cells: New Hope for Macular Degeneration
Embryonic Stem Cells Safe; Some Vision Gained in First 2 Patients Treated
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Retina Cells From Embryonic Stem Cells
While both of the treated women have macular degeneration, they suffer from different diseases. Stargardt's disease is a genetic defect, while dry macular degeneration is an immune defect. But both diseases destroy retinal pigment epithelium (RPE).
In the study, the women received new RPE cells grown from human embryonic stem cells. Embryonic stem cells have been tested in humans only once before -- in paralyzed patients with injured spinal cords. Results of those studies, now canceled, were never officially reported.
That makes the Schwartz/Lanza study the first official report of a treatment using human embryonic stem cells.
Advanced Cell Technology has developed a technique for obtaining embryonic stem cells without harming the embryo. But the current study, begun before this technique was invented, uses cells from an extra embryo created and discarded during an in vitro fertilization procedure.
Because the new retinal cells came from an unrelated embryo, there's the chance that patients' immune systems will reject the cells. There's very little of this kind of immune response within the eye, but patients in the study still undergo treatment with immunity-suppressing drugs.
Lanza says the two treated patients continue to do well six months after treatment. These women received 50,000 stem-cell-derived RPE cells. Dosages will be increased in subsequent patients up to 200,000 cells.
For comparison purposes, each patient is treated in one eye only.
A 24-patient European phase I trial, similar to the U.S. study, last week began enrolling patients.
If the treatment continues to prove safe -- still a big question mark -- larger studies will be planned. Even if everything goes perfectly, it will be years before a large-scale clinical trial begins accepting patients.
At least two patients may not have to wait that long. Lanza says the first two patients have each asked to be treated in the other eye.
"Much remains to be seen -- literally," Atala writes in an editorial accompanying the Schwartz/Lanza report in the Jan. 23 online issue of The Lancet.