A recent article published in the New England Journal of Medicine reported on the use of stem cell transplant to help patients who have had severe burn damage, either chemical or heat burns, to the cornea of their eyes in order to help them regain their eyesight. Normal corneas have a layer of stem cells called the limbus which act a source of new cells for cornea and thus maintain the cornea. In fact, the cornea is replaced every 9 to 12 months by these stem cells. The researchers noted that severe burns can destroy this layer of stem cells in the eye, and thus targeted the condition for treatment with stem cell therapy.
Limbal stem cells were obtain from one of the patient’s eyes and grown in a cell culture. They were then used to help the patients build a clear cornea, which is critical for eyesight. Patients who have received burns to their eyes often have a cornea which is scarred over and the scar tissue may contain blood vessels. It was the hope of researchers that the use of limbal stem cells would allow the patients to grow a normal cornea from an implanted layer of limbal stem cells.
While the procedure did not restore normal vision in all the patients, it was found to be remarkably successful. In fact about three fourths of patients had a clear cornea which could adequately repair itself after the procedure, and the result appeared to last at least up to ten years. This approach using stem cells may have been successful because the normal human cornea does contain a layer of stem cells in the limbus layer. Thus researchers were able to restore normal bodily functioning with this procedure. Other treatments involving the use of stem cells would be more like engineering, rather than simply restoring a lost bodily function.
Obviously, this treatment is groundbreaking and could be applied to thousands of patients worldwide who have suffered burn injuries to their corneas. But what does this say about the use of stem cells in general?
There is no organ in the human body exactly like the limbus in the cornea, which may be more amenable to stem cell therapy than say regenerating a liver in a patient with chronic liver cirrhosis. Nonetheless, clinical research is underway regarding the use of using stem cells in disorders such as liver cirrhosis and heart failure. Recently, a kidney failure patient who received a type of stem cell therapy developed abnormal blood vessel formation at the site of injection of the stem cells and later died. I was believe that this patient was actually harmed by the stem cell therapy given to him.
This may mean that building a scaffold for stem cells to migrate to and develop on may be very important for the use stem cell therapy. In the case of limbal stem cell therapy, the stem cells may have been confined to a geometrically two dimensional sort of space, whereas the injection of stem cells into failing organs may result in disordered growth in many cases.
In the future, stem cell therapy will likely play an ever increasingly role in medical care. Perhaps stem cell transplants will one day supplant many different organ transplant procedure as a first line therapy. However, much more research is needed before the procedure can be perfected to address more common medical conditions such as heart disease and kidney failure.