September 2009




Regenerative corneas: The future is now beginning

by Maxine Lipner Senior EyeWorld Contributing Editor


Substitute corneas built with patients’ own cells in early studies

Imagine being able to restore patients’ corneal function with tissue grown from their own cells. While that sounds like science fiction, that’s just the type of regenerative approach with which investigators are beginning to make real strides, according to May Griffith, Ph.D., professor, University of Ottawa, and senior scientist, Ottawa Health Research Institute, Ottawa. In the January 2009 issue of Eye, Dr. Griffith and fellow researchers reported on where their work with the approach now stands.

While practitioners these days use donor tissue for corneas that are no longer functional, Dr. Griffith sees a real need for regenerative substitutes. “Worldwide there’s a [donor cornea] shortage of about 10 million,” Dr. Griffith said. “The United States is the only self-sufficient country.” Roadblocks in other countries run the gamut from tissue testing costs to religious beliefs. “There are some countries with legislation that doesn’t allow harvesting the same way the United States does,” Dr. Griffith said. Also, in places such as the United Kingdom there’s extensive need to keep testing tissue. “Instead of just screening for HIV and [hepatitis], there’s now the question of whether to screen for Prion disease,” Dr. Griffith said. “There’s at least one documented case of rabies being transmitted, something you don’t normally think about.” As a result, costs for traditional donor corneas keep climbing.

Substitute material

Dr. Griffith’s group has been working on material for a regenerative medicine approach. “We’ve been making synthetic corneas because, first of all, they’re synthetic,” she said. “You can do a lot more batch control, and you don’t have the risk of transmission of disease because everything is manufactured.” This makes it possible to control the conditions and test for everything of concern. “The cost is lower and you’ve got better control,” Dr. Griffith said. “That’s why people are making artificial corneas.”

The approach centers on use of recombinant human collagen. “It is human collagen but it’s produced in yeast so that it can be tested for toxins and other things,” Dr. Griffith said. “Then we take these and chemically crosslink them and mold them to form corneas.” This acts like biointeractive scaffolding. “It stimulates the progenitor cells from the host to re-grow the tissue,” Dr. Griffith said. As a result, cells from the periphery start to populate the substitute corneas. So far the material has only been used for keratoconus and central scars. It has been tried on 10 patients to date. “The patients range from a teenager who was 18 to a 75-year-old,” Dr. Griffith said. “At six months everything looks good—there have been no complications.” While the 12-month data hasn’t yet been released, Dr. Griffith is optimistic about the way things are going. “All I can say is that things are going well, which is why we will be writing up and releasing the 12-month data and then continuing with the trials,” she said.

The study currently has been limited to safety and efficacy. “We have to start with the basic material,” Dr. Griffith said. The idea of the work to date has been to prove to regulatory agencies that the synthetic, recombinant collagen won’t have any adverse effect. “With this base material we know that it seems to work okay for patients with scarring, but we don’t know too much about it because this is only a Phase I safety study,” Dr. Griffith said. “We have not had a chance to test different methods of implantation and whether these make a difference.”

Future corneas

In addition to corneal scarring, Dr. Griffith projects that the regenerative material now being tested could have other uses as well. “At least for anterior lamellar grafts this would be fine,” she said. “We also think that this may be OK for the posterior and other things.”

Dr. Griffith’s team is also starting work on a new generation of materials. “This is supposed to target a variety of indications, but we haven’t gotten to the human stage yet,” Dr. Griffith said. “However, we’ve recently published animal studies showing that this stuff is pretty tough. It’s fairly resistant to enzymes and holds up to ultraviolet light, so we’re pretty hopeful with that material.”

Going forward, Dr. Griffith envisions a day when practitioners can pick the substitute corneal material for the condition at hand. “I think that there are going to be a range of materials because there are a whole range of indications,” she said. “I don’t believe that there will be one single material that’s going to cure blindness.” Phase II efficacy studies will likely start in the next year or two. Ultimately, Dr. Griffith foresees it taking about five to 10 years before this approach begins to come to practical fruition.

Editors’ note: Dr. Griffith has no financial interests related to her comments.

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