Thursday June 3 12:10 AM ET
Cell Transplant Procedure Restores Sight In Study
By Tony Munroe
BOSTON (Reuters) - Japanese researchers have found they can restore vision to some people with severe eye injuries by replacing damaged regenerative ''stem'' cells with healthy cells transplanted from donors.
The new stem cells allow the outermost layer of the cornea to continually regenerate, solving a once-intractable problem for some patients with severe damage to the surface of their eyes, the researchers reported in Thursday's New England Journal of Medicine.
Previous treatments, such as standard corneal transplant surgery, were ineffective after a few months when a patient's stem cells had been damaged.
Led by Dr. Kazuo Tsubota of the department of ophthalmology at the Tokyo Dental College, researchers found the transplant treatment effective in 51 percent of cases studied.
The study corroborates earlier research conducted at the University of Minnesota, giving hope to thousands of patients with damage to the stem cells of the outer skin of the cornea, said Dr. Edward Holland, an author of the earlier study, who co-wrote an accompanying editorial in Thursday's Journal.
When the outer skin of the cornea, or epithelium, is damaged, it eventually grows back, just as ordinary skin does. When healthy, the epithelium periodically sloughs off and regrows.
However, when the epithelium's stem cells are damaged, a condition known as conjunctivalization occurs. It is characterized by nontransparent, blood-vessel-laced tissue growing over the eye and obstructing vision.
Standard corneal transplants performed on patients with damaged stem cells are sometimes effective for a few months, before conjunctivalization sets in and the patient is blinded, Dr. Holland told Reuters.
But the Japanese researchers performed 70 epithelium stem cell transplants on 43 eyes of 39 patients. In 28 of the eyes, Tsubota's team also performed standard corneal transplants. If the stem cell transplants were initially ineffective, the researchers repeated the procedure, which was the case in 19 of the patients.
Researchers followed up with the patients for a minimum of one year, with a mean follow-up time of more than three years, and found that in 22 of the 43 eyes, treatment was effective.
''We found that transplantation of corneal epithelial stem-cell grafts was efficacious for the treatment of severe ocular-surface disorders,'' the researchers wrote.
In the accompanying editorial, Holland and Dr. Gary Schwartz wrote, ''success depends on the continuous turnover of stable corneal epithelium, which must be supplied from a viable source of epithelial stem cells.''
To those not in the field, the 51 percent success rate might not at first seem significant, Holland and Schwartz wrote, but they noted, ''without epithelial transplantation, none of these patients would have had clear corneas. All would be functionally blind.''
Tsubota's team wrote that the transplant procedure could prove more effective if complications such as ocular hypertension, dry eye, and graft rejection are controlled. |
