Cornea successfully grown from stem cells

In one of the first experiments to grow tissue from adult stem cell, scientists have grown corneas in the lab.

Researchers were able to grow the eye tissue after discovering a marker of a type of stem cell found in the eye that is essential for corneal development, maintenance and repair. The researchers say their findings could lead to treatment of eye diseases, as well as helping victims of burns and those injured by chemicals.

Dr Bruce Ksander, co-lead author of the study, from Massachusetts Eye and Ear, said: 'This finding will now make it much easier to restore the corneal surface'.

The cornea is the front section of the eye which acts as a barrier and also aids in vision by refracting light. The outermost layer of the cornea is maintained by the division of a type of stem cell, so-called limbal stem cells (LSCs). Loss of these LSCs due to disease or injury is a major cause of blindness throughout the world.

The main therapy for this type of blindness is a corneal transplant, but it is difficult to tell whether the grafts contain the cells required for the cornea to regenerate. 'Limbal stem cells are very rare, and successful transplants are dependent upon these rare cells', said Dr Ksander.

The researchers discovered a key molecular marker — a kind of signpost — that identified these hard-to-find cells. They demonstrated that this marker, a protein called ABCB5, was specific to LSCs. When the ABCB5 gene was inactivated in mice, they did not have many LSCs, making their corneas defective so they healed poorly after injury.

Having demonstrated that limbal stem cells with ABCB5 were needed for corneal regeneration, the team then used the ABCB5 protein to isolate LSCs from donated human corneas. After transplanting these stem cells into mice that lacked their own LSCs, the researchers were able to grow fully functional human corneas. This is one of the first examples of generating a functioning tissue from adult stem cells.

Professor Markus Frank from Boston Children's Hospital, a lead author on the study, told the BBC: 'The main significance for human disease is we have established a molecularly defined population of cells that we can extract from donor tissue'.

He added: 'These cells have a remarkable ability to self-regenerate. We hope to drive this research forward so this can be used as a therapy'.