According to British scientists, the prospect of reversing blindness has made a significant leap.
An animal study in the journal Nature Biotechnology showed the part of the eye which actually detects light can be repaired using stem cells.
The team at Moorfields Eye Hospital and University College London say human trials are now, for the first time, a realistic prospect.
Experts described it as a “significant breakthrough” and “huge leap” forward.
Photoreceptors are the cells in the retina which react to light and convert it into an electrical signal which can be sent to the brain.
However, these cells can die off in some causes of blindness such as Stargardt’s disease and age-related macular degeneration.
There are already trials in people to use stem cells to replace the “support” cells in the eye which keep the photoreceptors alive.
Now the London-based team has shown it is possible to replace the light-sensing cells themselves, raising the prospect of reversing blindness.
An animal study in the journal Nature Biotechnology showed the part of the eye which actually detects light can be repaired using stem cells
They have used a new technique for building retinas in the laboratory. It was used to collect thousands of stem cells, which were primed to transform into photoreceptors, and injected them into the eyes of blind mice.
The study showed that these cells could hook up with the existing architecture of the eye and begin to function.
However, the effectiveness is still low. Only about 1,000 cells out of a transplant of 200,000 actually hooked up with the rest of the eye.
Lead researcher Prof. Robin Ali said: “This is a real proof of concept that photoreceptors can be transplanted from an embryonic stem cells source and it give us a route map to now do this in humans.
“That’s why we’re so excited, five years is a now a realistic aim for starting a clinical trial.”
The eye is one of the most advanced fields for stem cell research.
It is relatively simple as the light sensing cells only have to pass their electrical message on to one more cell in order to get their message to the brain, unlike an attempt to reverse dementia which would require cells to hook up with far more cells all across the brain.
The immune system is also very weak in the eye so there is a low chance of the transplant being rejected. A few cells can also make a big difference in the eye. Tens of thousands of stem cells in the eye could improve vision, but that number of stem cells would not regenerate a much larger organ such as a failing liver.
US scientists announce that human cloning has been used to produce early embryos, marking a “significant step” for medicine.
The cloned embryos were used as a source of stem cells, which can make new heart muscle, bone, brain tissue or any other type of cell in the body.
The study, published in the journal Cell, used methods like those that produced Dolly the sheep in the UK.
However, researchers say other sources of stem cells may be easier, cheaper and less controversial.
Opponents say it is unethical to experiment on human embryos and have called for a ban.
Stem cells are one of the great hopes for medicine. Being able to create new tissue might be able to heal the damage caused by a heart attack or repair a severed spinal cord.
There are already trials taking place using stem cells taken from donated embryos to restore people’s sight.
However, these donated cells do not match the patient so they would be rejected by the body. Cloning bypasses this problem.
The technique used – somatic cell nuclear transfer – has been well-known since Dolly the sheep became the first mammal to be cloned, in 1996.
The technique used for human cloning, somatic cell nuclear transfer, has been well-known since Dolly the sheep became the first mammal to be cloned
Skin cells were taken from an adult and the genetic information was placed inside a donor egg which had been stripped of its own DNA. Electricity was used to encourage the egg to develop into an embryo.
However, researchers have struggled to reproduce the feat in people. The egg does start dividing, but never goes past the 6-12 cell stage.
A South Korean scientist, Hwang Woo-suk, did claim to have created stem cells from cloned human embryos, but was found to have faked the evidence.
Now a team at the Oregon Health and Science University have developed the embryo to the blastocyst stage – around 150 cells – which is enough to provide a source of embryonic stem cells.
Dr. Shoukhrat Mitalipov said: “A thorough examination of the stem cells derived through this technique demonstrated their ability to convert just like normal embryonic stem cells, into several different cell types, including nerve cells, liver cells and heart cells.
“While there is much work to be done in developing safe and effective stem cell treatments, we believe this is a significant step forward in developing the cells that could be used in regenerative medicine.”
Embryonic stem cell research has repeatedly raised ethical concerns and human eggs are a scarce resource. This has led researchers to an alternative route to stem cells.
The technique takes the same sample of skin cells but converts them using proteins to “induced pluripotent” stem cells.
However, there are still questions about the quality of stem cells produced using this method compared with embryonic stem cells.
Opponents of the new technique argue that all embryos, whether created in the lab or not, have the potential to go on to become a fully-fledged human, and as such it is morally wrong to experiment on them.
They strongly advocate the use of stem cells from adult tissue.
However, advocates of the new technique say that the embryos created from this technique could never become viable human beings.
Researchers say that early results from the world’s first human trial using embryonic stem cells to treat diseases of the eye suggest the method is safe.
US firm Advanced Cell Technology told The Lancet how two patients who had received the retinal implants were doing well, four months on.
Trials of the same technique have also started at London’s Moorfields Eye Hospital.
But experts say it will be years before these treatments are proven.
The aim of these first human studies is to establish that the treatment is safe to use.
The treatment takes healthy immature cells from a human embryo, which are then manipulated to grow into the cells that line the back of the eye – the retina.
Experts hope that by injecting these cells into a diseased eye, they will be able to restore vision for people with currently incurable conditions such as Stargardt’s disease – one of the main causes of blindness in young people.
Advanced Cell Technology, along with the Jules Stein Eye Institute at the University of California, Los Angeles, are reporting their first experiences with this treatment in human trials.
The study involved one elderly patient in her 70’s with dry age-related macular degeneration – the leading cause of blindness in the developed world – and another female patient in her 50’s with Stargardt’s disease.
Both had very poor vision and were registered blind.
Each patient was given an injection containing 50,000 of the retinal pigment epithelium cells into one of their diseased eyes.
After surgery, structural evidence confirmed the cells had attached to the eye’s membrane as hoped, and continued to survive throughout the next 16 weeks of the study.
Furthermore, the procedure appeared to be safe, causing no signs of rejection or abnormal cell growth.
Although this study is not designed to see if the procedure actually works, the researchers say their results do suggest that their patients’ vision has improved slightly.
But they say it is still too soon to make any firm conclusions and that many more years of investigation will be needed to confirm that the treatment is both safe and effective.
The researchers told The Lancet: “The ultimate therapeutic goal will be to treat patients earlier in the disease processes, potentially increasing the likelihood of photoreceptor and central visual rescue.”
But even if this does become possible, such treatments would face stiff opposition by critics who say it is ethically wrong to use human embryonic tissue.
Dr. Dusko Ilic, Senior Lecturer in Stem Cell Science at Kings College London, said that these early findings did not necessarily hint towards a viable treatment.
“We should keep in mind that people are not rats.
“The number one priority of initial clinical trial is always patient safety. If everyone expects that the blind patients will see after being treated with human embryonic stem cell-derived retinal pigment epithelium, even if the treatment ends up being safe (which is what Advanced Cell Technology are trying to determine in this trial), they risk being unnecessarily disappointed.”
