The eye and stem cells on the way to treating blindness eurostemcell

The eye and stem cells: Toward a Treatment for BlindnessOur sense of sight may well be the most important of our senses, being essential to help us navigate our surroundings. Its loss has an enormous impact on a person's life, but many diseases that cause blindness remain difficult or impossible to treat.

Researchers are now using stem cell technology to try to develop new treatments for vision loss.

Treatments for most diseases that cause vision loss are difficult or not yet possible.

Specialized cells in the eye serve specific functions, e.g. B. Focusing light and converting what is seen into signals that are sent to the brain. The eye contains several types of stem cells that constantly renew specialized cells that are worn out or damaged.

Holoclar® is currently the only clinically approved stem cell therapy for the eye. This treatment restores vision to patients with damaged corneas (the clear outermost part of the eye) by transplanting limbal stem cells from the lab into areas of the eye where these cells are missing.

Holoclar® only works if patients still have their own limbal stem cells in the eye. These are then used to grow further cells in the laboratory. New methods of creating limbal cells from pluripotent stem cells for people without their own limbal stem cells are currently in the developmental stage.

Researchers are studying how transplantation of retinal pigment epithelial cells derived from pluripotent stem cells could prevent vision loss in patients with diseases such as age-related macular degeneration.

In addition, researchers are using stem cells to study many different aspects of the eye – from how the eye is formed to the causes of eye diseases and their treatments.

Many diseases that lead to blindness are not yet treatable. Researchers are working to understand what causes these diseases, what other types of stem cells are found in the eye, and how stem cells could be used to repair or even restore a patient's vision. Many of these studies are still in early stages. Just as it took over twenty years to develop Holoclar® into a safe and successful treatment option, today's research projects and discoveries will take time before they can be safely and reliably used to treat other types of blindness.

The eye is the one of our organs that is responsible for the visual perception of our environment. It is able to sense ambient light and transmit information about it to our brain. It is a very complicated organ, which, similar to a camera, is composed of several, specialized individual parts. These parts, or ties, are in turn composed of many different types of cells, each of which has a specific function, enabling the tie to perform its specific task.

The eye: A complex organ composed of layers of different cell types.

The most important parts of the eye are:


Pigment epithelium

Eye diseases occur when one or more of these individual parts is damaged and/or no longer functions properly. Depending on which part is affected, different diseases can develop. Their treatment is complicated by the fact that, unlike the electronic parts of a camera, new biological parts are not readily available. This is where stem cell technology could come into play. Stem cells can serve as a source of new, healthy, specialized cells, helping to replace damaged cells in the eye. Depending on the type of eye disease, different stem cell types could be used in a variety of ways. So what is the current research focused on?

the eye and stem cells on the way to treating blindness eurostemcell

Limbal stem cells from the human cornea with a protein called p63 stained yellow. Cell nuclei (containing DNA) are colored red. The cells of the cornea (the transparent part of the eye) are expanded by blinking. constantly damaged by external influences. To repair this damage, we have a small number of stem cells that sit at the edge of the cornea called limbal stem cells. They are responsible for producing new corneal cells to replace damaged cells. When disease leads to the loss of these stem cells, the cornea can no longer be repaired. This influences the incidence of light into the eye. Leads to significant vision loss.

Years of painstaking research have led to the development of a technique in which limbal stem cells are harvested from a suitable healthy donor or, in the case of bilateral injury, from remaining healthy limbus. These can be expanded in the laboratory and then transplanted in sufficient numbers into the damaged eye. Clinical studies have shown that transplantation of limbal stem cells derived from a healthy eye can repair the cornea and permanently restore vision. In order to avoid immune rejection, such a treatment is only successful if the patient has preserved a healthy part of the limbus from which limbal stem cells can be derived.

The eye and stem cells on the way to treating blindness eurostemcell

Restoration of the cornea: currently the only stem cell-based therapy of the eye that has been successfully tested in clinical trials.

This is currently the only available stem cell treatment for the eye that has been proven successful in clinical trials. In 2015, the European Commission (in agreement with the European Medicines Agency) authorized the marketing of an "advanced therapy medicinal product" that incorporates limbal stem cells. This is the final step for clinical implementation after a successfully completed trial. The therapy, called Holoclar ®, is based on more than twenty years of research by a team of scientists internationally recognized in the field of epithelial stem cell biology. It is produced in GMP certified facilities and in accordance with European legislation by a company called Holostem Terapie Avanzate S.r.l, an offshoot of an Italian university, manufactured and sold by Chiesi Farmaceutici S.p.a. marketed.

If the corneas of both eyes are affected (bilateral limbal deficiency), this therapy does not work because in this case there are no remaining limbal stem cells available. For the treatment of such cases, researchers are currently investigating a different approach – the use of embryonic stem cells, induced pluripotent (iPS) cells or oral mucosal stem cells – to generate new limbal stem cells in the laboratory. This method could eliminate the complicated surgery that must be performed to engraft limbal stem cells. Furthermore, this would have created a theoretically inexhaustible source of limbal stem cells. There is hope that this method will be available for future patients.

Replacing retinal pigment epithelial cells

Retinal pigment epithelium (RPE) cells fulfill

A whole range of important tasks, including supplying the adjacent retina. When these cells stop functioning properly due to damage or disease, certain parts of the retina die off. Since the retina is the part of the eye responsible for perceiving light, this leads to blindness. RPE cells can be damaged by a wide variety of diseases, including age-related macular degeneration (AMD), retinitis pigmentosa and Leber's congenital amaurosis (LCA).

One method to treat these diseases would be to replace damaged RPE cells with transplanted healthy cells. Unfortunately, it is not possible to obtain healthy RPE cells from donors, so another source of cells must be found for transplantation. Scientists recently succeeded in creating new RPE cells from both embryonic stem cells and iPS cells in the laboratory. The safety of embryonic stem cell-derived RPE cells has been tested in phase I/II clinical trials. The study involved patients with Stargardt's disease, a macular degeneration, and AMD, and was conducted by a biotechnology company called Advanced Cell Technologies. Results published in 2014 proved the safety of the method. Engraftment (growth) of the transplanted RPE cells. However, some study participants experienced adverse side effects due to immunosuppression and the transplantation procedure itself. Interestingly, although this was not the intended goal of the study, several patients reported improvement in their vision.

A second phase I/II study is currently underway in the U.K. This study will investigate whether RPE cells derived from human embryonic stem cells are suitable for the treatment of patients with "wet" AMD. In September 2015, cells were transplanted into a first patient. The ongoing study, led by Prof. Pete Coffey to lead, is taking place at Moorfields Eye Hospital and is part of the London Project to Cure Blindness.

Japanese researcher Dr. Masayo Takahashi is leading a clinical trial in Japan in which RPE cells generated from iPS cells are being used in patients with wet AMD. The results of the study, which began in June 2016, are widely anticipated.

There are several other phase I or phase I/II clinical trials around the world with a small number of participants using pluripotent stem cells. These studies are mainly aimed at the safety, and in some cases efficacy, of the method using RPE cells generated from pluripotent stem cells for both dry and wet AMD and Stargardt's disease. Replacing damaged RPE cells will only be successful in patients who still have an at least partially functional retina, and thus some residual vision (e.g.B. in early stages of the disease), have. This is based on the fact that the RPE cells are not the cells that "see" themselves, but are responsible for supporting the "seeing" retina. Vision is lost in this type of disease because the retina degenerates as the RPE cells can no longer perform their function. These must be replaced at a time when there is still a functioning retina that needs to be repaired. There is hope that the transplantation of RPE cells can stop the progressive, permanent loss of vision, and in some cases even improve vision to a certain extent.

Replacement of retinal pigment epithelial cells: Methods are currently being developed and tested in early clinical trials that allow cells to be grown in the laboratory for therapeutic purposes.

Replacement of retinal nerve cells

Loss of vision in many cases is due to a problem in the nerve plexus located in the retina. Different diseases occur when certain specialized cells in this nerve plexus either stop functioning properly or die off. Although the retina is more complicated than other parts of the eye, there is hope that a source of new retinal cells will be found. Then damaged or dying cells could be replaced. The retina must be repaired. In addition, this approach could also be used to repair damage to the optic nerve.

In this case, too, scientists have turned to stem cell technology to find a source of replacement cells. Several studies have now reported that different types of retinal cells can be generated in the laboratory from both embryonic stem and iPS cells. One particular type of cell in the eye, called Muller cells, is known to be able to produce retinal cells in some species, such as z.B. in zebrafish, act as a stem cell. There is evidence that this may also be the case in humans. In this case, Muller cells could be another source of cells that could be used to repair the retina.

In contrast to transplantation of RPE cells, repair of the retina in patients who are already blind could restore vision to a certain extent. This gives hope to patients who have z.B. stage of age-related macular degeneration are. In whom the light-sensitive photoreceptors of the retina have already been lost.

This type of research could also lead to new treatments for people with retinal diseases such as z.B. produce retinitis pigmentosa or glaucoma. However, despite promising results, this field of research is still in its infancy. No clinical trials of this kind are currently planned in patients either, as more intensive research needs to be done first.

Replacing retinal nerve cells: Current research is trying to understand how retinal nerve cells could be made for treatment purposes in the future.

Stem cell technology has great potential for improving the lives of people with vision problems. Numerous studies are currently underway to develop new methods to treat and/or prevent vision loss. A central point of all these studies is to understand how different types of stem cells behave, and how best to harness their potential. A tailored approach must be used depending on the problem of each patient. Stem cells are not a panacea, but they have a great potential for the production of new biological components for the repair of the eye.

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