Submitted on September 14, 2006
Accepted on February 18, 2007
Tissue-Specific Stem Cells
|
Characterization of the limbal epithelial stem cell niche: Novel imaging techniques permit in-vivo observation and targeted biopsy of limbal epithelial stem cells
Alex J. Shortt 1*,
Genevieve A. Secker 2,
Peter M. Munro 3,
Peng T. Khaw 4,
Stephen J. Tuft 5,
Julie T. Daniels 2
1 Cells for Sight Transplantation and Research Programme, UCL Institute of Ophthalmology, London, United Kingdom; Ocular Repair and Regeneration Biology Unit, UCL Institute of Ophthalmology, London, United Kingdom; Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom
2 Cells for Sight Transplantation and Research Programme, UCL Institute of Ophthalmology, London, United Kingdom; Ocular Repair and Regeneration Biology Unit, UCL Institute of Ophthalmology, London, United Kingdom
3 Ocular Repair and Regeneration Biology Unit, UCL Institute of Ophthalmology, London, United Kingdom
4 Ocular Repair and Regeneration Biology Unit, UCL Institute of Ophthalmology, London, United Kingdomsemi; Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom
5 Cells for Sight Transplantation and Research Programme, UCL Institute of Ophthalmology, London, United Kingdom; Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom
* To whom correspondence should be addressed. E-mail: a.shortt{at}ucl.ac.uk.
 |
Abstract |
|---|
It is anticipated that stem cell (SC) therapy will enable the regeneration of diseased tissues and organs. Understanding SC niches is an essential step towards realizing this goal. By virtue of its optical transparency and physical separation of SC and transient amplifying cell compartments, the human cornea provides a unique opportunity to visualize and observe a population of adult stem cells, limbal epithelial stem cells (LESC), in their niche environment. To date the characteristics of the LESC niche have remained unclear. State-of-the-art imaging techniques were used to construct a 3D view of the entire human corneal limbus and identify the structural characteristics of the LESC niche. Two distinct candidate LESC niche structures were identified. Cells within these structures express high levels of the putative limbal stem cell markers P63alpha and ABCG2 however, current methods cannot identify for certain which exact cells within this cell population are truly LESCs. These structures could be located and observed in-vivo in normal human subjects, but not in patients with clinically diagnosed corneal LESC deficiency. The distribution of these structures around the corneal circumference is not uniform. Biopsies targeted to limbal regions rich in LESC niche structures yielded significantly higher numbers of LESCs in culture. Our findings demonstrate how adult stem cell niches can be identified and observed in-vivo in humans and provide new biological insight into the importance of LESC niche structures in maintaining normal LESC function. Finally, the concept of targeted biopsy of adult SC niches improves stem cell yield and may prove to be essential for the successful development of novel adult stem cell therapies.
Key Words.
Stem cell, cornea, limbus corneae, somatic stem cell biology, human, stem cell transplantation, three dimensional imaging
