Development of biological and synthetic substrates for the ex-vivo expansion of conjunctival epithelium for ocular surface reconstruction

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Background The conjunctiva is a thin membrane that covers and protects the surface of the eye. It lines the inner surfaces of the upper and lower eyelids creating anatomical spaces between the eyelids and eyeball known as conjunctival fornices. The conjunctiva may become irreversibly damaged and the fornices obliterated by scarring following injuries such as chemical burns, severe infections or autoimmune disease. When severe, this prevents eyelid closure, restricts movement and causes lid deformity leading to painful blindness when the cornea (optically clear structure on the eye's surface) becomes opaque due to progressive abrasion and scarring. Such patients comprise up to ten percent of patients attending specialist ocular surface clinics. So far techniques to replace conjunctiva have failed as a result of recurrent scarring or because the graft has been insufficient in size. These patients invariably suffer visual loss due to corneal disease which cannot be addressed with clear corneal grafts unless the ocular surface is restored first. I will develop a novel biological and synthetic material on which the patient's own conjunctival cells will be cultivated to create larger grafts for transplantation. Conjunctiva will be retrieved from a cadaver and the cellular (living components) removed leaving behind a 'biological scaffold'. Eventually this research will lead to a patient's own cells being seeded on the developed substrate and the resulting graft transplanted into the same individuals so that an immune reaction should not occur. Examples of biological scaffolds successfully transplanted in humans include skin, heart valves and trachea. The synthetic substrate will be developed on a well tolerated biomaterial (ePTFE), commonly known as 'Gore-Tex', also used in medical devices such as grafts for blood vessel repair. This has been previously shown to support fornix reconstruction but growth of conjunctiva on its surface would be novel. I plan to render the surface conducive to cell growth by incorporating chemical groups and proteins on the ePTFE surface. My preliminary work has shown conjunctival growth on gas plasma treated ePTFE but further development is required to achieve optimal results. Aim: To develop decellularised human conjunctiva and ePTFE with novel surface chemistry to enable conjunctival expansion for future use as grafts.How research will be conducted Human conjunctival tissue will be obtained from deceased patients at the Royal Liverpool University Hospital and the research carried out in laboratories in the University of Liverpool. A novel protocol for the decellularisation of conjunctiva will be developed through collaboration with NHS Blood and Transplant, Liverpool. The ePTFE will undergo chemical modification by a process that changes surface chemistry (gas plasma treatment) and binding of proteins. Once both substrates have been developed, cadaveric conjunctival biopsies will be cultured on the two novel surfaces leading to the production of two conjunctival constructs. The physical and biological properties of the engineered constructs will be tested and compared to natural human conjunctiva.Expected outcomes This research will benefit patients who require conjunctival replacement for reasons including glaucoma surgery, excision of conjunctival growths and fornix reconstruction. The greatest impact of this research will be in patients with severe ocular surface disease ranging from autoimmune conditions such as mucous membrane pemphigoid to those with chemical burns. These novel grafts will enable ophthalmologists to develop new surgical strategies to reconstruct the surface of the eye. This will profoundly reduce pain and improve visual outcomes for patients with severe conjunctival disease. The novel materials developed through this fellowship could also lead to cell replacement therapies to treat other incurable eye diseases in the future.