One Shot of Gene Therapy and Children with Congenital Blindness Can Now See
from University of Pennsylvania School of Medicine , Oct 24, 2009
Born with a retinal disease that made him legally blind, and would eventually leave him totally sightless, the nine-year-old boy used to sit in the back of the classroom, relying on the large print on an electronic screen and assisted by teacher aides. Now, after a single injection of genes that produce light-sensitive pigments in the back of his eye, he sits in front with classmates and participates in class without extra help. In the playground, he joins his classmates in playing his first game of softball.
His treatment represents the next step toward medical science's goal of using gene therapy to cure disease. Extending a preliminary study published last year on three young adults, the full study reports successful, sustained results that showed notable improvement in children with congenital blindness.
Researchers from the University of Pennsylvania School of Medicine and the Center for Cellular and Molecular Therapeutics at the Children's Hospital of Philadelphia have used gene therapy to safely improve eyesight
The study, conducted by researchers from the University of Pennsylvania School of Medicine and the Center for Cellular and Molecular Therapeutics at The Children's Hospital of Philadelphia, used gene therapy to safely improve vision in five children and seven adults with Leber's congenital amaurosis (LCA). The greatest improvements occurred in the children, all of whom are now able to navigate a low-light obstacle course—one result that the researchers call "spectacular." Although the patients did not attain normal eyesight, half of them (six of 12) improved enough that they may no longer be classified as legally blind. "The clinical benefits have persisted for nearly two years since the first subjects were treated with injections of therapeutic genes into their retinas," said senior author Jean Bennett, M.D., Ph.D., F.M. Kirby professor of Ophthalmology at the University of Pennsylvania School of Medicine. For Bennett, the results build on nearly 20 years of gene studies on hereditary blindness, starting with pioneering work in mice and dogs. "These remarkable results," she added, "have laid a foundation for applying gene therapy not only to other forms of childhood-onset retinal disease, but also to more common retinal degenerations."
"Children who were treated with gene therapy are now able to walk and play just like any normally sighted child," said co-first author Albert M. Maguire, M.D., an associate professor of Ophthalmology at Penn and a physician at Children's Hospital. "They can also carry out classroom activities without visual aids."
Maguire and Bennett have been researching inherited retinal degenerations for nearly 20 years. Leber's congenital amaurosis, the target of this current study, is a group of inherited blinding diseases that damages light receptors in the retina. It usually begins stealing sight in early childhood and causes total blindness during a patient's twenties or thirties. Currently, there is no treatment for LCA.
Walking along a dimly lit, simulated street route, the children were able to negotiate barriers they bumped into before the surgery. Another child, who since birth, could only see light and shadows, stared into his father's face and said he could see the color of his eyes. Later they played soccer together.
For children and adults in the study, functional improvements in vision followed single injections of genes that produced proteins to make light receptors work in their retinas.
The 12 subjects ranged in age from 8 to 44 years old at the time of treatment. Four of the children, aged 8 to 11, are the world's youngest individuals to receive gene therapy for a non-lethal disease (A fifth subject was 17 years old). On the other end of the age scale, the 35-year-old man and 44-year-old woman are the oldest patients to ever receive gene therapy for retinal degeneration.
from Advanced Cell Technology, Inc and Technology Review , June 17, 2009
An experimental therapy using human embryonic stem cells to treat degenerative eye diseases has proved safe and effective in animal studies, and may begin early human trials in the next few months if it receives approval from the Food and Drug Administration. If granted approval, the therapy will be the second embryonic-stem-cell-based treatment to progress to human trials, and it will provide a test case for further applications of stem cells.
While scientists have made huge advances using stem cells to treat diseases in animal models, testing these experimental therapies in humans poses some unique challenges. One is proving that the cells are safe: embryonic stem cells, which can develop into any tissue type in the body, carry the risk of forming tumors. Another challenge is the threat of immune rejection of the transplanted cells; in most cases, introducing foreign cells would require a patient to take powerful drugs for life to suppress the immune system, as is the case with organ transplants. For that reason, the first stem-cell therapies have focused on the eye and nervous system, so-called immune-privileged sites that do not experience this response to foreign cells.
Geron, a biotech company based in Menlo Park, CA, received FDA approval in January for a trial to treat patients with acute spinal-cord injuries with cells derived from embryonic stem cells.
This latest treatment for eye disease, developed byAdvanced Cell Technology (ACT), based in Worcester, MA, uses human embryonic stem cells to re-create a type of cell in the retina that supports the photoreceptors needed for vision. These cells, called retinal pigment epithelium (RPE), are often the first to die off in age-related macular degeneration and other eye diseases, which in turn leads to loss of vision. Several years ago, scientists found that human embryonic stem cells could be a source of RPE cells, and subsequent studies found that these cells could restore vision in mouse models of macular degeneration.
This microscopic image shows a cross section of the retina of a rat with a degenerative eye disease that received a transplant of retinal cells derived from human embryonic stem cells. The middle layer of speckled green represents several layers of photoreceptors, which developed in response to the transplant. Untreated animals lost all but a single layer.
Credit: Advanced Cell Technology
In a recent study published online in the journal Stem Cells, researchers from ACT and Oregon Health Sciences University show that their stem-cell therapy provides a long-term benefit in animal models of vision loss. A second experiment tested the long-term safety of the cells in mice--an important requirement for moving into human testing--and found no evidence that the cells cause tumors.
To test the efficacy of the cell transplants, the researchers injected RPE cells derived from embryonic-stem-cell lines into the eyes of rats with a genetic defect in their RPE that causes their vision to gradually deteriorate. After three months, the retinas of treated rats had many more photoreceptors than those of untreated diseased rats, and the treated animals performed better in vision tests; however, their performance in the tests diminished with time. The transplants were also able to improve vision in a mouse model of Stargardt's disease, a rare but untreatable illness that causes blindness early in life.
Stem Cell Contact Lenses Can Cure Blindness in Less Than a Month
from the Australian, May 28, 2009
Three Australians have had their sight restored thanks to their own stem cells and ordinary contact lenses
Individuals with low or no vision will be excited about a new research effort in Australia that restored sight to 3 blind individuals in less than a month by contact lenses cultured in stem cells.
To obtain the stem cells the Researchers took less than a millimeter on the side of each patients cornea. They then cultured stem cells from the tissue in extended wear contact lenses.
The surface of the patients' corneas was cleaned and and the lenses inserted. Within 10 to 14 days the stem cells began to attach to the cornea, replenishing damaged cells. Satisfied that the stem cells were doing their job, the researcher removed the lenses and the patients have been seeing with new eyes for the last 18 months.
Although the innovative technique was used to reverse blinding corneal disease, it promises to be a quick, painless and cheap treatment for other visual disorders. To read more about it, click here.
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