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Verena E. Chankiewitz, Erik Chankiewitz, Mona Eulitz, Carsten Theiss, Daniel Meller, Beate Brand-Saberi; The Chick Eye As A New Model For The Limbal Stem Cell Niche. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5112.
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The maintenance of a transparent ocular surface requires the continuous regeneration of the corneal epithelium. For this a special stem cell population is located at the corneal limbus. This anatomical structure connects the corneal and the conjunctival epithelium. It is characterized by the so-called limbal crypts constituting the putative stem cell niche. An insufficiency of limbal stem cells leads to complete vision loss. Therefore the reconstruction of the ocular surface by replacement with stem cells grown in cell culture is an important matter for clinical and scientific investigation. The efforts to develop advanced substitutes by tissue engineering are limited because of an incomplete molecular characterization of the limbal stem cells and their niche. One reason for this is the rareness of suitable human tissues from organ donations and the lack of an adequate animal model. The cornea of mice and rabbits has a different morphology and an alternative mechanism of stem cell dynamics has been suggested for mice. The aim of this study was the establishment of the chick eye as a new model for the limbal stem cell niche.
The eyes of chick embryos were investigated using scanning and transmission electron microscopy. Paraffin sections were stained with antibodies against stem cell markers.
The morphology of chick cornea and limbal region is highly similar to the human one.Especially the Bowman’s layer can be clearly distinguished in chick histological sections in contrast to mammalian models. The transmission electron microscopic analysis visualized a small number of basal located cells which could be identified as putative stem cells. They were characterized by a dark nucleus surrounded small cytoplasmic rim. Via scanning microscopy the topology of the corresponding area could be invetigated more closely. Structures analog to limbal crypts were detected. The immune histochemistry data supported the interpretation of the morphological findings.
From this we conclude that the chick corneal limbus because of its structur and morphology will be an appropriated model for investigations concerning the molecular nature of limbal stem cells and their niche. The major advantages of the new model are the easy access and the possibility of direct manipulation of gene expression by electroporation techniques. This opens a new field for further studies addressing the molecular mechanisms underlying human limbal stem cell insufficiency and improvement of curative strategies.
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