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.
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'.