Limbal stem cells to the rescue

Simple Limbal Epithelial Transplantation (SLET) has demolished the invisible walls that had made limbal stem cell transplantation an exclusive procedure.

The body generates new cells to replace worn-out cells through special reservoir cells known as stem cells, which have an unlimited potential for regeneration.

The Surgery

The procedure involves a relatively minor surgery to remove the tissue, which is then cultured in a laboratory on a human amniotic membrane. After almost a fortnight, it is then transplanted to the patient. Following surgery, the patient is checked in the clinic, with follow-up visits scheduled every four to six weeks till it is found satisfactory,” he says.

Limbal stem cell culturing is useful for patients needing large amounts of stem cell replacement, when too many cells taken from the donor eye may cause a deficiency there. “In autograft the patient’s own tissue is used (after culturing) to treat the diseased eye. This reduces the risk of rejection, as compared to a donor tissue,” says Dr Sayan Basu.

He adds, “Autograft also implies minimal use of steroid immuno-suppressants, which means avoiding life-long dependence on drugs, as well as reduced side-effects of drugs.”

Prevent eye injuries

The most common cause of injury leading to stem cell deficiency is chuna or common lime. “We have found that 80 per cent of injuries that cause grave stem cell damage are caused by exposure to chuna. Parents and guardians must be very careful and ensure that children never have access to chuna packets. Adults must also guard against accidental exposure to packets of chuna if they burst,” he warns.

The need for stem cell transplantation
Until recently, organ failure was treated with direct transplantation of donated organs and tissues, like liver transplants, kidney transplants, and heart transplants.

“The understanding of the functioning of stem cells made it possible to treat certain diseases by culturing these cells in the laboratory. However, the only areas where stem cells are probably being used clinically in human beings, globally, are blood disorders (bone marrow transplant) and eye diseases,” says Dr Sayan Basu, consultant ophthalmologist and scientist cornea and anterior segment services, L.V. Prasad Eye Institute.

The stem cell transplantation technique involves “culturing” or growing cells in the laboratory by taking a small bit of tissue, and then transplanting them into the stem cell deficient area. So, how are stem cells used for treating eye disorders? “All eye disorders cannot be treated with stem cells; only the front part of the eye can be treated. The eye’s outer surface is exposed to the environment, and has a constant turnover of cells to maintain the optical transparency of the cornea.

These cells are regenerated from reserve stem cells, known as limbal stem cells, which are found in an area called the limbus. The function of limbal stem cells is to regenerate the epithelial (surface) cells of the cornea, while also serving as a barrier to ensure that the conjunctival cells do not grow over the cornea and mar its transparency,” he says.

Limbal stem cells help regenerate the surface of the cornea when there is any decay or damage. However, in cases of chemical burns, allergic reactions to drugs and auto-immune diseases, the limbal stem cells may become damaged and lose their ability to regenerate new cells. “The damage to the limbal cells may be partial or total; it may be unilateral — in one eye — or bilateral — in both eyes. Based on the extent of damage, doctors make a clinical decision whether a graft from the same eye will be sufficient, or whether there is a need to take it from the other eye,” explains Dr Sayan.

There are two types of grafts — allograft and autograft. In allograft, the cells used for culturing are taken from a relative or donor, while in autograft the cells for culturing are taken from the patient.