Transparent again
The cornea is the outer layer of the eye, which should be perfectly transparent for normal vision. Stem cells contained in the limb – the transition zone between the cornea and the sclera with a width of about 1 mm – support the health of the cornea.
In patients with chemical burns of the eye, the limbal area is often affected to such an extent that new cells can no longer be created. Limbal stem cell deficiency can also be caused by infections, complications of prolonged contact lens wear, and other causes.
In addition to vision loss, patients with chemical eye burns often experience pain and discomfort in the affected eye. Existing treatment strategies include transplantation of a donor or artificial cornea (which carries the risk of infection and the development of glaucoma), as well as a method of transplantation of stem cells from a healthy eye – conjunctival limbal autograft (conjunctival limbal autograft, CLAU).
Surgeons from the Massachusetts Eye and Ear Hospital restored the cornea to four patients, each of whom had a chemical burn of one eye, using their own stem cells taken from a paired healthy eye. They applied a new method of transplantation of cultured autologous limbal epithelial cells (cultured autologous limbal epithelial cell transplantation, CALEC). The CALEC technique was developed in collaboration with researchers from the Dana-Farber Cancer Institute and Boston Children's Hospital. Unlike CLAU, the new method requires a much smaller volume of healthy tissue, since stem cells are not transplanted directly into the diseased eye, but are pre-cultured in vitro.
Four cases are described that are part of an ongoing clinical trial, they represent the first procedures of this kind conducted in the United States. Under the leadership of Uly Yurkunas, the group performed the first CALEC procedure in April 2018. A biopsy with stem cells was taken from the patient's healthy eye two weeks before surgery. Corneal (limbal) stem cells were multiplied and grown on a special membrane. After the cells covered the entire membrane and the graft was ready for transplantation, surgeons removed the scar tissue on the damaged cornea and transplanted CALEC.
Since then, three more patients have received CALEC treatment. Two patients received a transplant after the first biopsy. One patient's cells did not grow in sufficient numbers during the first biopsy, but the second attempt was successful. The cells of another patient included in this phase of the study did not grow well enough to carry out the transplant. In total, four of the five patients included in this study received a CALEC transplant. Four patients who received CALEC treatment no longer experienced the same pain shortly after the CALEC transplant procedure. They will be monitored for a long time.
It should be noted that the purpose of limbal stem cell transplantation, such as CALEC and CLAU, is to restore the healthy surface of the damaged eye using cells from the other eye, avoiding the use of donor or artificial tissue; therefore, it will only help patients with limbal stem cell insufficiency in one eye. After the restoration of a healthy surface, these patients may need a routine corneal transplant. Healthy limbal stem cells are necessary for the maintenance and engraftment of transplanted corneal tissue.
Now that the feasibility and safety of the method have been demonstrated, researchers have begun recruiting patients with corneal damage for the second phase of the study, which will last until 2021. In addition to safety and feasibility, it will assess whether CALEC transplantation can lead to vision restoration on its own or whether it should be used only as a preparatory stage for the transplantation of a donor or artificial cornea.
The process of isolating, growing and preparing limbal stem cells for transplantation was developed in collaboration with Dr. Miriam Armant of Boston Children's Hospital. The production process is carried out in strictly sterile conditions. It takes approximately three weeks from taking the material to creating a transplant ready for transplantation.
The method does not carry the risk of rejection, like some other procedures, because the cells belong to the patient himself. Accordingly, patients receiving CALEC and CLAU do not need long-term use of steroids or immunosuppressants. Aminat Adzhieva, portal "Eternal Youth" http://vechnayamolodost.ru based on the materials of the Dana-Farber Cancer Institute: Dana-Farber collaborates with Mass. Eye and Ear to rebuild damaged corneas using patients’ own stem cells for first time in United States.