There has been a recent questioning of the role of the limbal stem cell in corneal maintenance and the recent Association for Research in Vision and Ophthalmology (ARVO) meeting in Fort Lauderdale May 3 -7, 2009 saw some fairly hot debate son this topic. Professor Colin Green, University of Auckland, New Zealand reviews an interesting series of sessions for The Society for Clinical Ophthalmology.
The almost universally accepted “X,Y,Z” model for the natural turnover of corneal epithelial cells arose from the brief two page hypothesis of Thoft and Friend published in 1983 (Invest Ophthalmol Vis Sci. 1983;24:1442-3). Superficial cells are said to shed from the corneal surface by constant desquamation (Z component) and replaced from a population of stem cells which reside in the basal limbal region and continue to cycle slowly throughout life. Their daughter cells migrate centripetally (Y component) into the basal layer of the corneal epithelium and differentiate into upper layers of the cornea (X component) to become post-mitotic cells. The “X, Y, Z” hypothesis has been widely accepted and combined with the general belief that corneal epithelial stem cells reside in a highly specialised and protected limbal niche.
Recently Fran?�ois Majo and colleagues (Nature. 2008;456:250-4) suggested instead that oligopotent stem cells are distributed throughout the mammalian ocular surface and Chang et al. (Invest Ophthalmol Vis Sci. 2008;49:5279-86) have shown that the central human cornea expresses stem cell markers and is quite capable of healing after laser ablation in an ex vivo model.
Presentations at the recent ARVO meeting (May 3 -7) were set to be controversial and both poster and workshops sessions saw lively debate.
The full article can be accessed through the Society for Clinical Ophthalmology’s website, click here.
The Society welcomes submissins and comments from eye care practitioners across all specialities. If you were at ARVO, we are particularly keen to hear from you.
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Society for Clinical Ophthalmology