Low Vision News: Edition 2 with Dr. Tseng

Scheffer C.G. Tseng, M.D., Ph.D., is the Director of Research and Development at Tissue Tech, Inc.; he is also Medical Director and Consultant for Bio-Tissue, Inc., and the Director of Ocular Surface Research and Education Foundation. He has been credited as the inventor of Corneal Stem Cell Transplantation. Loss of clarity to the cornea is one of the most common causes of blindness around the world.

Follow up:

LVN EDITOR- When did you first start your study of corneal stem cell transplantation?

Dr. Tseng- In 1986 I received a Fellowship in Corneal and External Diseases at Massachusetts Eye and Ear Infirmary in Boston. I worked with Dr. Kenneth R. Kenyon. Dr. Kenyon was interested in the way the cornea heals. The cornea is the clear covering of the front of the eye. It heals differently from other tissues in the body. Cells migrate to the wound site to close a wound before growing new cells and forming adhesions called desmosomes. In 1986 we did not know about the existence of stem cells. We did observe that the juncture where the cornea meets the sclera or white part of the eye, called the limbus, was vitally important for the cornea to heal. Now we know that this area is very rich in stem cells. Dr. Thoft was an advocate of conjunctival transplantation for chemical burns to the cornea. He did experiments on rabbit cornea and thought conjunctival tissue was able to replace the corneal tissue in a process called transdifferentiation. We subsequently found in rabbits that transdifferentiation was a result of incomplete removal of the limbus. This observation and later on new data from Dr. Tung-Tien Sun allowed Dr. Kenyon and me to test corneal stem cell transplantation in human patients.

LVN EDITOR- How did you realize there were stem cells at the limbus that transformed into corneal cells that healed corneal wounds?

Dr. Tseng- I learned this concept from my mentor, Dr. Tung-Tien Sun, who is now the Rudolf L. Baer Professor and Director of Epithelial Biology, Department of Dermatology, NYU School of Medicine. As explained above, he identified the limbus as the site for corneal stem cells to give rise to corneal epithelial cells. He identified the role of stem cells in the growth of epithelial cells. This important finding, which was later supported by the clinical data from human patients operated by Dr. Kenyon and myself, gave us the solid foundation to receive grant support from the National Institutes of Health to continue study how these stem cells are regulated and how they are damaged by different diseases so that we can improve our diagnosis and treatment for patients suffering from limbal stem cell deficiency. This research effort led us to develop the new surgical technique where a small portion of the limbus of the healthy eye can be removed, cultured and then transplanted back to the diseased eye.

LVN EDITOR- Can you describe your surgical treatment?

Dr. Tseng- First we harvest a patient's stem cells at the limbal junction. Then we grow tissue cultures, which can take several months. Once the tissue cultures are grown, they can be surgically transplanted like conventional keratoplasty. This surgical procedure is considered experimental at this stage and will require the approval from the FDA first.

LVN EDITOR- What new projects are you working on?

Dr. Tseng- Some people have such severe damage to both eyes by chemical burns, Stevens-Johnson Syndrome, and hereditary diseases like aniridia, that there is no healthy tissue one can grow. Besides using cells from the mouth, we are doing research to see if other types of cells, such as the amniotic tissue, may be used to support the stem cell cultures.

LVN EDITOR- We look forward to talking with you again to see how your new work turns out. Please feel free to visit Low Vision News.Com to see the hope it gives our readers.