To evaluate the effectiveness of cultured human limbal epithelium for the treatment of limbal stem cell deficiency

The cornea is the clear window at the front of the eye and its clarity is vital for light transmission to the back of the eye for visual perception. Transparency of the cornea depends upon the integrity of its outermost layer called the epithelium, which is constantly regenerated throughout life by a population of stem cells found at the edge of the cornea in an area called the limbus, the so called limbal stem cells (LSC). If LSC becomes deficient as a result of injury or disease, this epithelium will breakdown leading to severe pain and blindness. This condition is often difficult to treat, however, the management of limbal stem cell deficiency (LSCD) has benefited from major breakthroughs in recent years. LSC from the patient?s own (one eye disease) or a relative healthy eye or from a cadaveric eye can grow in the laboratory and then transplanted to the diseased eye. This technique however uses animal products to help grow the cells with a great risk of diseases transmission. In addition, the safety and effectiveness of this treatment is rather difficult to establish due to the diversity and the small number of cases reported. Transplantation of cultured limbal epithelium can therefore not be recognized, enabling NHS funding, until its effectiveness and safety is determined by a formally structured clinical trial. Such a trial forms the main objective of this proposal. We have therefore developed an ?animal product free? technique for growing the cells in the laboratory in an ultra-clean environment and successfully transplanted 8 patients with LSCD in one eye by taking LSC from their healthy other eye. Despite of our success, this number of patients is not significant to draw proper conclusions. This proposal aims therefore to evaluate the safety and efficacy of our methods by treating more patients with total unilateral LSCD. Another aim of the project is to develop a freezing method of cultured human LSC for storage and to set-up a service to supply clinical grade cultured LSC for transplantation at other UK centres. In addition, this study will investigate the abnormal tear film in patients with LSCD to allow for a customised eye treatment. Finally, LSCD has an enormous impact on patient?s quality of life with serious detrimental effects on productivity and leisure activities. To that effect we have selected 4 questionnaires to look at different aspects of patients with LSCD and its treatment.

Limbal stem cell deficiency (LSCD) is a disease caused by the loss or dysfunction of limbal stem cells (LSC). In LSCD, the corneal epithelium integrity and function cannot be maintained and consequently epithelial defects occur causing persistent pain and severe visual impairment with marked patient morbidity, often affecting young adults and requiring frequent clinic visits. By far the most common cause is from chemical burns. The management of severe LSCD has benefited from major breakthroughs in recent years. In 1989, it was proposed that tissue limbal grafts could be used to treat LSCD. This involved tissue from the patient?s other healthy eye (autografts in unilateral cases) or from a living relative or cadaver (allografts in bilateral cases). In cases of autografts and living relatives, the donor eye is at risk of developing iatrogenic LSCD due to the large amounts of tissue required. In cases of allografts, systemic immunosuppression is required which is associated with enormous risk of toxicity. In 1997, Pellegrini and co-workers described a procedure using a small piece of autologous limbal tissue cultivated in vitro to treat two patients with unilateral alkali burns. This significantly reduces the risk of causing LSCD in the donor eye and eliminates the requirement of immunosuppression. Subsequently, other studies have been conducted, however the effectiveness of this treatment is impossible to establish due to the small number of cases reported and the heterogeneity of the studies. Transplantation of cultured limbal epithelium can therefore not be recognized as a treatment option for LSCD, enabling NHS funding, until its safety and effectiveness is established by a formally structured clinical trial. Such a trial forms the main objective of this proposal. We have successfully treated 8 consecutive patients with total unilateral LSCD using ex vivo expanded (animal free system and full GMP conditions) LSC autografts. Aims of this study is to evaluate:
? The safety and effectiveness of cultured human LSC for the treatment of patients with unilateral total LSCD;
? Patients reported outcomes before and after LSC transplantation;
? The tear film of patients with unilateral LSCD before and after LSC transplantation;
? The predictive value of pre-operative OCT in terms of visual outcomes and the need for further surgery, e.g., penetrating keratoplasty;
? To develop a cryopreservation method of culturing human LSC for storage and to set-up a national service to supply clinical grade ex vivo expanded LSC for transplantation at other UK centres.