Corneal Epithelium Repair and Therapy Using Autologous Limbal Stem Cell Transplantation

Overview

Corneal disease is a leading cause of blindness in the world. A shortage of corneal donor tissue has prevented many patients from regaining vision. Additionally, refractive error such as myopia is a major cause of impaired visual function worldwide. Although refractive error is correctable by procedures that modify the refractive power of the cornea, these procedures often weaken corneal integrity and have risk of complications. This study aims to evaluate the safety and efficacy of corneal surface epithelium repair and regeneration in the treatment of corneal surface diseases and refractive error using autologous limbal stem cell transplantation.

The corneal surface is comprised of a unique type of non-keratinized epithelial cell. These cells are arranged in an orderly fashion, which is essential for vision by maintaining the transparency of the visual axis. Chemical injury and pterygia may damage the limbus, the zone between the cornea and the bulbar conjunctiva, and cause limbal stem cell (LSC) deficiency. They represent major treatable causes of vision loss worldwide. A shortage of corneal donor tissue prevents many patients from regaining vision, necessitating new treatment strategies to circumvent this limitation. Transplantation of stem cells represents an appealing therapeutic strategy in regenerative medicine, and the use of endogenous stem cells provides a possible solution to the problem of immune rejection. Currently, LASIK (laser-assisted in situ keratomileusis) is the most commonly performed laser vision correction procedure in the world (over 10 million surgeries each year); however, it has a major disadvantage in that it weakens corneal integrity and structure and predisposes to complications such as keratectasia or keratoconus (bulging of the cornea) and vision loss. An alternative is photo-refractive keratectomy (PRK), which removes the corneal epithelium and anterior stroma while minimizing the incidence of keratectasia or keratoconus. The primary drawbacks of PRK are that it requires a longer recovery time (the corneal epithelium must regenerate from the patient's own LSCs) and may result in blurry vision and pain due to corneal pain nerve fiber exposure after removal of the epithelium. Coverage of exposed corneal stroma tissue immediately after surgery with LSC-derived corneal epithelial cells will solve this key bottleneck and make laser eye surgery safer and more comfortable for millions of people. It is known that corneal renewal and repair are mediated by stem cells in the limbus. Autologous LSC transplantation has been reported previously (Rama et al.). However, mouse feeder cells were required to expand LSCs in culture. We have successfully developed a feeder-free, chemically defined medium in which to expand LSCs. These expanded LSCs can repair and regenerate corneal surfaces (Ouyang et al., in press). Hypothesis: The trial will demonstrate whether a new technique, transplantation of LSCs expanded from limbal tissue of the uninjured eye, can improve the visual function of patients with unilateral corneal ocular surface disease. In addition, it will show whether there is more rapid recovery and improved visual outcomes following PRK if expanded LSCs are used to cover the cornea. The study will also compare the incidence of complications and characterize visual outcomes in patients treated with the new technique versus the control technique.