Growing limbal stem cells without using human scaffold
R. PRASAD

Stem cells may get infected or contract some unknown diseases if amniotic membrane is used

Polymer scaffold: Limbal stem cells from the healthy eye were expanded on the polymer scaffold and transplanted to the damaged eye.

Using stem cells present in the limbus region of eye to restore vision in people who have damaged cornea and limbus as a result of chemical or thermal injuries, or are suffering from Stevens-Johnson syndrome is nothing new. It is being done for the last few years.

Corneal cells are destroyed or worn out every day. The limbal stem cells produce new corneal cells and ensure that eyesight is not affected. Restoring sight in the damaged eye is done by transplanting the limbal stem cells from the healthy eye to the damaged eye.

Since removal of large amounts of limbal stem cells from the undamaged eye may lead to depletion of stem cells, doctors usually remove a small quantity of limbal stem cells from the healthy eye and expand (increase in number) them in the laboratory by culturing.

The conventional way of culturing the stem cells to increase their numbers is to use a human amniotic membrane, a thin membrane found in the placenta, as a scaffold. But scientists are not very comfortable using a human membrane — there are chances of stem cells getting infected or contracting some unknown disease.

Scientists have been on a hot pursuit of a non-living material such as collagen as a scaffold. The Vision Research Foundation (Sankara Nethralaya), Chennai, along with the Nichi-in Centre for Regenerative Medicine, Chennai, appear to have found one such scaffold.

Scientists have used a polymer as a scaffold to grow stem cells harvested from the eyes of rabbits. The results of the animal study have been published in the journal of Tissue Engineering: Part A.

Twelve rabbits have been studied and two used as control. One eye of all the rabbits was damaged and limbal stem cells from the other eye were taken and expanded on the polymer scaffold. When transplanted to the damaged eye, seven rabbits had their sight fully restored. There was partial success with two rabbits and failure in three.

“Partial success was because the rabbits which underwent transplantation earlier kept scratching their eyes during the initial days,” said Dr. Samuel Abraham, Director of Nichi-in Centre.

“So we put a restraint (cover) on the eye of others and thereafter everything went well.”

According to him, the quantity of undifferentiated stem cells is more when the polymer scaffold was used. And more the stem cells better are the chances of vision restoration.

The polymer was first standardised on humans. Corneal limbal stem cells derived from human cadavers were used for standardisation. It was later standardised in rabbits at Sankara Nethralaya.

More research needs to be done on animals and trials in humans before the safety and efficacy of the technique can be assessed.