What are committed stem cells

Stem cells for the eyes

A fine seam on the edge of the cornea of ​​the eye - the so-called "limbus" - is irreplaceable for vision. This is where the stem cells grow and migrate into the cornea and renew its tissue. Due to this constant regeneration, the cornea remains translucent. If the "limbal stem cells" are destroyed by accidents such as burns or chemical burns, the cornea gradually perishes. Those affected go blind, says Prof. Daniel Meller, senior physician at the Essen University Eye Clinic.

"One function of the corneal stem cell is the regeneration of the cornea. The other function is a barrier function. The corneal stem cells hold the conjunctival cells up. And if these are lost, they grow unhindered on the cornea. They overgrow the cornea and then lead to one relatively rapid clouding of the corneal surface. "

In 2003 the ophthalmologist developed a new method to help accident victims. If only one eye is affected, the doctor removes a two-square-millimeter piece of tissue with stem cells from the other, healthy eye. The removed stem cells are then multiplied in an incubator - on a membrane made of amniotic sac tissue, which is made available by the gynecological clinic of the University of Essen with the consent of the woman giving birth. This is the only way, explains Daniel Meller, that the stem cells remain active

"This culture medium that we use is the amniotic membrane - it is said - that is the innermost layer of the amniotic sac. This amniotic membrane has biological properties that are very important for us eye clinicians. We can use this to imitate the so-called stem cell niche. You have to know that It is not only the stem cells that are important, but also their niche where they live. And the amniotic membrane in particular has the ability to imitate such a niche, and we use this in our cell culture system. "

The stem cells multiply in the incubator for around 14 days, then they are transferred to the diseased eye. Just a few weeks later, the clouding of the cornea visibly decreases. However, complete healing is not achieved with the procedure. At best, some patients were able to regain 40 percent of their original vision

"The first goal is to reconstruct the surface of the eye. We have a cloudy cornea, and we want to give the patient a clear cornea again. If we can do that, we give the patient the basis for better vision. The second goal is then also shown in the vision improvement our patients have shown over the long term. "

Around 100 patients have already been treated with the stem cell method. Successful in 75 percent, the corneal opacity decreased: however, patients were only able to see to a limited extent. For the other 25 percent, the therapy was unsuccessful because the stem cells did not grow. The cure rate is even lower if the stem cells come from foreign donors, for example relatives. This is always the case when both eyes of a patient are burned and no stem cells of their own are available. The scientist now wants to further optimize the culture conditions for the stem cells - for better results. Essen is the only clinic that offers the procedure in Germany. And it will probably stay that way, according to the judgment of many eye experts. Prof. Frank Holz, for example, heads the University Eye Clinic in Bonn:

"These are procedures where it certainly makes sense that it is reserved for specialized centers. There are also many high-specializations in ophthalmology, and it is quite common for a center - we in Bonn also have our high-level specializations in certain directions - specialized, because the number of affected patients is also relatively low with the indication for stem cell therapy. And then the expertise is bundled in one place. "