Damage to the cornea can impair vision
Umbilical cord stem cells may help treat people whose vision is damaged by a cloudy cornea, US research suggests.
The cornea is the transparent front part of the eye, which protects the delicate structures underneath and helps focus light.
But disease or injury can make it go cloudy, impairing vision, and corneas for transplant are in short supply.
A US team used human umbilical cord stem cells to treat laboratory mice with abnormally thin, cloudy corneas.
The University of Cincinnati study was presented at an American Society for Cell Biology conference.
The mice had been bred to lack a protein essential for the formation and maintenance of a transparent cornea.
The cells - known as human umbilical cord mesenchymal stem cells (UMSCs) - have the ability to become any of a wide range of adult cell types.
They survived in the mouse cornea for three months with minimal signs of rejection.
They appeared to take on the properties of standard corneal cells called keratocytes.
Following the transplant, the thickness and transparency of the animals' corneas improved significantly.
In contrast, transplants using a different type of cell - human umbilical hematopoietic stem cells, which can give rise to all blood cell types - produced disappointing results.
They vanished rapidly from the mouse corneas when transplanted into the animals' eyes.
Easy to isolate
Lead researcher Dr Winston Kao said unlike donated corneas, the supply of UMSCs for use in transplants was almost unlimited.
He said the cells were easy to isolate from the umbilical cord, could be grown effectively in culture and stored easily in liquid nitrogen.
Dr Kao said: "Corneal transplantation is currently the only true cure for restoration of eyesight that may have been lost due to corneal scarring caused by infection, mechanical and chemical wounds and congenital defects of genetic mutations.
"Worldwide, there is a shortage of suitable corneas for transplantation.
"These findings have the potential to create new and better treatments and an improved quality of life for patients with vision loss due to corneal injury."
Dr Bruce Allan, a consultant ophthalmic surgeon at London's Moorfields Eye Hospital, said: "Access to cells to build new tissue-engineered corneal constructs may well lead to viable alternatives to conventional transplantation in future.
"The cornea is a relatively simple organ and cell therapies, including those based on mesenchymal stem cells, should ultimately succeed.
"But for the medium term at least, transplantation is likely to continue."
Dr Francisco Arnalich, another expert from Moorfields, has carried out similar work in rabbits using mesenchymal stem cells derived from fat tissue.
He said a US team had also had success using stem cells taken from human corneas.
He said: "There is still a long way to go from saying that they achieved clear corneas - moreover they just state that they improved transparency, not that they reach normal transparency - to say that this could be a substitute of corneal grafting."