The transparent portion of the center of our eyes is called the cornea. Scars on the cornea can cause an infuriating haziness across the eye. However, healing these cloudy corneas might be as simple as growing stem cells from a tiny biopsy of the patient’s undamaged eye and placing them on the injury site. This hope comes from experiments in a mouse model system conducted by researchers at the University of Pittsburgh School of Medicine. These findings were published in Science Translational Medicine and could one day rescue vision for millions of people worldwide and decrease the need for corneal transplants.
According to statistics compiled by the National Eye Institute, which is a branch of the National Institutes of Health, globally, corneal infectious diseases have compromised the vision of more than 250 million people and have blinded over 6 million of them. Additionally, trauma from burns is also a leading cause of corneal scarring.
James L. Funderburgh, Ph.D., professor of ophthalmology at Pitt and associate director of the Louis J. Fox Center for Vision Restoration of UPMC and the University of Pittsburgh, a joint program of UPMC Eye Center and the McGowan Institute for Regenerative Medicine, said, “The cornea is a living window to the world, and damage to it leads to cloudiness or haziness that makes it hard or impossible to see. The body usually responds to corneal injuries by making scar tissue. We found that delivery of stem cells initiates regeneration of healthy corneal tissue rather than scar leaving a clear, smooth surface.”
The lead author of this study, Sayan Basu, is a corneal surgeon who works at the L.V. Prasad Eye Institute in Hyderabad, India. Dr. Basu who joined with Dr. Funderburgh’s lab, has developed a technique to isolate ocular stem cells from tiny biopsies from the surface of the eye and a region between the cornea and sclera known as the limbus. Such a small biopsy heals rapidly with little discomfort and no disruption of vision. Such biopsies are banked in tissue banks and then expanded in culture, and several tests shows that even after isolation and expansion, these cells are still corneal stem cells.
“Using the patient’s own cells from the uninjured eye for this process could let us bypass rejection concerns,” Dr. Basu noted. “That could be very helpful, particularly in places that don’t have corneal tissue banks for transplant.”
Basu in collaboration with Funderburgh’s team tested these human limbal stem cells in a mouse model of corneal injury. This team used goo made of fibrin to glue the cells to the injury site. Fibrin is the protein found in blood clots, but it is also commonly used as a surgical adhesive. Application of these limbal stem cells not only induced healing of the mouse corneas, their eyes became clear again within four weeks of treatment. On the other hand, the eyes of mice that were not treated with limbal stem cells remained cloudy.
In fact, the healing was so good that Funderburgh said: “Even at the microscopic level, we couldn’t tell the difference between the tissues that were treated with stem cells and undamaged cornea. We were also excited to see that the stem cells appeared to induce healing beyond the immediate vicinity of where they were placed. That suggests the cells are producing factors that promote regeneration, not just replacing lost tissue.”
This work is the impetus behind a small pilot study presently underway in Hyderabad which will treat a handful of patients with their own corneal stem cells.