| dc.description.abstract | It is widely accepted today that stem cells in the adult corneal epithelium is located to the limbus. No specific marker of limbal epithelial cells (LESCs) has been identified, yet many have been suggested, including ΔNp63α, ABCG2, vimentin and notch 1. Negative markers include amongst others the differentiation markers Ck3 and Ck12. The lack of an identified specific marker elucidates the need for establishment of more exact molecular markers of LESCs. Limbal stem cell deficiency (LSCD) may result from a variety of aetiologies, such as chemical and thermal injuries, and represents an important cause of loss of vision and blindness worldwide. There is an ongoing discussion about the definition of this condition and a diagnosis with clear criteria has not been established for LSCD. The treatment options vary depending on the presentation of the LSCD. In partial LSCD when the central cornea and the visual axis are not affected, conservative management is indicated. If there is involvement of the central cornea in partial LSCD, surgical management is indicated, including mechanical debridement of conjunctival epithelium from the corneal surface and/or amniotic membrane transplantation. When total LSCD is present, surgical management with replacement of the damaged or absent limbal stem cells is currently the treatment of choice. The transplants can either be large whole tissue limbal epithelial grafts, or ex vivo expanded limbal epithelial grafts from small biopsies of limbal epithelium. The expanded limbal epithelial cells can be autologous or allogenic. Ex vivo expansion of limbal epithelial cells in culture is a relatively new technique for the treatment of LSCD, and no international or national guidance has been established. This has resulted in several studies seeking to investigate this technique, but these studies are hard to compare due to different variables, such as methods of ex vivo expansion, allo- versus autografts, composition of the culture medium, the surgical management, postoperative management, and the definition of a successful outcome. The composition of the culture medium is essential for the culture of limbal epithelial cells, and fetal calf serum, various hormones and growth factors have been included in most studies. Concern has been raised about the use of animal-derived products in the culture systems where LESCs are expanded, as this implies a possibility for interspecies pathogen transfer when transplanting the grafts, including prion diseases. This risk is further augmented due to the fact that immunosuppression is required. In the past years, researches have investigated options trying to exclude animal-derived products. So far, transplantation of these grafts has shown promising results as a way of treating LSCD with an overall success rate of 76 %. Although this number is based on studies with a wide range of differences, the success rates seem to be fairly consistent, but long-term follow-up is needed. More research in this field is required to improve the established, but not yet standardised, techniques. Ideally an international guidance should be established for a culture method free of non-human derived products, and which is also governed by the principles of good manufacturing practice. | eng |