A New Way to Regrow Human Corneas

My apologies to my readers, but I was at the Free Methodist Bible Quizzing Finals at Greenville College in Illinois for the last week. I am recovering and have only the energy to write a short post for today.

The cornea is the transparent covering of the eye that transmits light from the environment to the inside of the eye, to the photoreceptor-rich retina that interprets the light information and translates them into neural signals that are sent to the visual centers of the brain.

The cornea is subject to constant wear and tear, but fortunately, a stem cell population called limbal stem cells. These stem cells constantly regenerate the cornea, and the conjunctiva, which is otherwise known as the “whites of the eye.”

Limbal stem cells


Unfortunately, the limbal stem cells can be damaged by chemicals, sparks from a welding, genetically inherited conditions, or physical trauma. Such conditions can prevent proper replacement of constantly sloughed cornea and conjunctival cells. This can seriously compromise the structural integrity and function la of the eye.

To treat patients with corneal limbal stem defects, eye surgeons have transplanted limbal cells from cadavers or used small excisions of limbal cell populations from the unaffected eye and transplanted them into the affected eye. These so-called “autologous limbal cell transplants” tend to work quite well, but there are two cuts that need to be made. Is there are way to expand limbal stem cells for clinical use? Now it appears that there is.

Scientists from the Massachusetts Eye and Ear Infirmary have used sophisticated key tracer molecules to pin down the precise cells in the eye that are capable of regeneration and repair. They then transplanted these regenerative stem cells into mice to create fully functioning corneas.

This work was published in the international journal Nature, and they predict that this method may one day help restore the sight of victims of burns and chemical injuries.

Limbal stem cells (LSC) completely renew our corneas every few weeks and repair the cornea and conjunctiva whenever they are injured. Without LSCs the cornea becomes cloudy, which severely disrupts vision. In fact, LSC deficiencies are among the commonest reasons behind blindness worldwide.

Unfortunately, the LSC population is embedded in a part of the eye where they share space with a matrix of other structures in the limbal part of the eye (FYI – the limbus is the junction between the cornea and the white of the eye).

Enter the work from the Massachusetts Eye and Ear Infirmary in Boston at the Boston Children’s Hospital, Brigham and Women’s Hospital and in collaboration with the VA Boston Healthcare System have identified a key molecule known as ABCB5, which is naturally present on the surface of LSCs.

Although ABCB5 has been known about for some time in other parts of the body, this is the first time ABCB5 has been identified on the surfaces of LSCs. Also, it is clear that ABCB5 can effectively mark LSCs.

By using molecules linked to fluorescent molecules, these scientists were able to instantly identify a pool of LSCs on donated human corneas. After transplanting these cells into the eyes of mice, they discovered that the transplanted cells were able to generate fully functioning human corneas.

Prof Markus Frank, of Boston Children’s Hospital, a lead author in the research, 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.

“And these cells have the remarkable ability to self-regenerate. We hope to drive this research forward so this can be used as a therapy.”

Harminder Dua, professor of ophthalmology at the University of Nottingham, who was not involved in this study, said: “This paper represents a very comprehensive and well conducted piece of work that takes use closer to the precise identification of stem cells.

“Applying this knowledge to a clinical setting could help improve the outcomes for patients who need corneal reconstruction.”