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S.L. McGowan, D.R. Whikehart; Evidence for Stem Cells Found in the Posterior Limbus. Destination: The Corneal Endothelium? . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3013.
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© ARVO (1962-2015); The Authors (2016-present)
Investigators have long accepted that human corneal endothelial cells (HCECs) are reluctant to divide. However, recent evidence of an increased endothelial cell population at the periphery of the human cornea has prompted research into the potential existence of stem cells or stem–like cells in the endothelial periphery. Identifying and isolating stem cells or transient amplifying cells in the endothelial periphery might explain the origin of HCECs and indicate a source of theses cells in wound repair. In addition, these cells may be of value in culturing and in corneal transplants.
Human corneas with attached scleral rims were obtained from eye banks and assayed for the presence of nestin. Whole corneas were frozen and sectioned transversely, ensuring the presence of trabecular meshwork and limbus. Nestin fluoresence staining, using a monoclonal primary antibody and a fluorescein congugated secondary antibody, was performed. Sample slides consisting of unlabeled, primary antibody only and secondary antibody only were used as negative controls. A172 glial cells were stained as a positive control.
The sectioned tissues consistently exhibited strong fluorescence due to nestin in the trabecular meshwork. In addition, occasional fluorescence was observed in the region of Schwalbe's line. No fluorescence was seen in any region of the cornea: endothelium, stroma and epithelium. There was also no fluorescence observed at the anterior region of the limbus.
The results suggest that stem cells may be present in the trabecular meshwork and, possibly, in the surrounding region where the endothelium joins the trabecular meshwork (i. e., Schwalbe's line). Nestin is an intermediate filament protein, which is expressed in undifferentited cells and has been well–documented in multiple systems to be a reliable marker of stem cells from the neural crest. This cell population at the posterior limbus has the potential of generating new cells for the corneal endothelium after wounding.
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