Limbal stem cell deficiency and its management

Fig. 1. 45 years old male with a history of chemical injury to his left eye. A, Pre-operative photograph of the left eye showing total limbal stem cell deficiency. B, 1 month after ex vivo expansion autologous limbal stem cell transplantation and C, 12 months after corneal transplantation.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 efficacy 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 efficacy is established by a formally structured clinical trial. Such a trial forms the main objective of our research project. We have successfully treated 8 consecutive patients with total unilateral LSCD using ex vivo expanded (animal free system and full GMP conditions) LSC autografts (Phase I study). Postoperatively, clinical and histological reversal of LSCD with the establishment of stable corneal epithelium was obtained in all eyes (100%) with significant improvements in both visual impairment and pain scores. This study demonstrates that transplantation of autologous limbal epithelial stem cells cultured on human amniotic membrane (HAM) without the use of non-human animal cells or products, is a safe and effective method of successfully treating patients with total LSCD. The full study has been recently published in the journal “Stem Cells”.

A larger study involving 24 new patients is currently underway with funding from the UK Medical Research Council. The aim of this Phase II study is to evaluate the long-term safety and efficacy of cultured human LSC for the treatment of patients with unilateral total LSCD.

This research project is a collaborative effort between:

Mr Francisco Figueiredo, Prof Majlinda Lako, Mr Sajjad Ahmad, Prof John Armitage, Dr Monica Berry, Prof Anne Dickinson, Prof Elaine McColl, Dr. Hardeep Mudhar, Prof Konrad Pesudovs, and Dr Nick Steen.

This project is the result of a strong partnership between North East England Stem Cell Institute (NESCI), the Institute of Genetics Medicine and the Eye Department at Royal Victoria Infirmary/Newcastle University.

Selected publications:

  • Baylis O, Figueiredo F, Henein C, Lako M, Ahmad S. "13 Years of Cultured Limbal Epithelial Cell Therapy: A Review of the Outcomes". Journal of Cellular Biochemistry. 2011;9999:1-11.
  • Ahmad S, Kolli S, Lako M, Figueiredo F, Daniels J. "Stem cell therapies for ocular surface disease" has been accepted for publication in Drug Discov Today. 2010 Apr; 15(7-8): 306-13. Epub 2010 Feb 10.
  • Kolli S, Ahmad S, Lako M, Figueiredo F. Successful Clinical Implementation of Corneal Epithelial Stem Cell Therapy for Treatment of Unilateral Limbal Stem Cell Deficiency. Stem Cells. 2010 Mar 31; 28(3): 597-610.
  • Ahmad S, Kolli S, Li D, Paiva C, Pryzborski S, Dimmick I, Armstrong L, Figueiredo F, Lako M. A putative role for RHAMM/HMMR as a negative marker of stem cell-containing population of human limbal epithelial cells. Regenerative Medicine 2008; 26(6): 1609-19.
  • Kolli S, Lako M, Figueiredo F, Ahmad S. Loss of corneal epithelial stem cell properties in outgrowths from human limbal explants cultured on intact amniotic membrane. Regenerative Medicine 2008; 3(3): 329-42.
  • Ahmad S, Stewart R, Yung S, Kolli S, Armstrong L, Stojkovic M, Figueiredp F, Lako M. Differentiation Of Human Embryonic Stem Cells Into Corneal Epithelial Like Cells By In Vitro Replication Of The Corneal Epithelial Stem Cell Niche. Stem Cells, 2007; 25 (5): 1145-1155 and front cover Stem Cells 25 (5).
  • Ahmad S, Figueiredo F, Lako M. Corneal epithelial stem cells: characterization, culture and transplantation. Regenerative Med. 2006, 1: 1-15.