Research

Stem cells are cells that on one hand, make more of themselves and on the other, can differentiate (be converted) to other cell types. It is this dual ability that makes them attractive and suitable for possible therapeutic purposes. The fertilized egg, on its way to the embryo, is one such stem cell. Hence the name ‘embryonic’ stem cells (ESCs). However, there are stem cells in certain other parts of the body, which, while not as versatile as ESCs, can be made to differentiate to desired cell types. These are called ‘adult’ stem cells (ASCs). Of the two, ASCs are ethically more acceptable to many people than ESCs.

The limbus of the eye (in the front portion, surrounding the cornea) contains stem cells (ASCs), which can be differentiated to produce some types of corneal cells. This property is very useful when we want to reconstruct any damage that has occurred to the front of the eye, as happens upon chemical or fie burns. The damage can be too severe to be treated by a simple graft of a donor cornea. In such situations, culturing limbal stem cells to generate the corneal outer layer (epithelium) becomes a very good option in order to reconstruct the damaged part and restore vision.

A team of clinicians and cell biologists at the LV Prasad Eye Institute, Hyderabad, India, have gainfully used this method to restore vision, in a significant manner, to over 400 people who had been blinded due to chemical or fire burns. They have taken a very tiny portion of the limbal issue from the good eye of the patient, and cultures the cells from there to produce a transparent, stitchable, functional corneal epithelium, and transplanted it on the patient and restore vision. Started in 2001, this mode of treatment on the eye happens to be the largest successful application of stem cell therapy anywhere.

When such a patient comes to the clinic with both eyes damaged, the clinician has had to depend on next of kin as donor for the limbal tissue, as the source of stem cells. Such ‘allogenic’ (non-self) transplants pose the possibility of rejection by the patient; in such cases, immuno-suppressive drugs need to be given for indefinite periods of time.

In order to overcome this difficulty, the LVPEI team has adopted a procedure (initiated by some Japanese colleagues) of taking a very small piece of tissue from the lower lip of the patient himself, culture it to generate the equivalent of the corneal epithelium and transplant it on the patient. This ‘autologous’ (self to self) procedure has been tried on a small number of patients with bilateral burns, successfully. These patients undergo a regular corneal graft at an appropriate time of healing.