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Open AccessArticle

Characterization of Human Transition Zone Reveals a Putative Progenitor-Enriched Niche of Corneal Endothelium

1
Tissue Engineering and Stem Cell Group, Singapore Eye Research Institute, Singapore 169856, Singapore
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Eye-Academic Clinical Program, Duke-National University of Singapore (NUS) Graduate Medical School, Singapore 169857, Singapore
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Department of Ophthalmology, Duke University School of Medicine, Durham, NC 27705, USA
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Data Science Group, Singapore Eye Research Institute, Singapore 169856, Singapore
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Department of Ophthalmology, Claude Bernard Lyon 1 Université, 69622 Villeurbanne, France
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Singapore National Eye Centre, Singapore, Singapore 168751, Singapore
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School of Material Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
*
Authors to whom correspondence should be addressed.
Cells 2019, 8(10), 1244; https://doi.org/10.3390/cells8101244
Received: 10 August 2019 / Revised: 9 October 2019 / Accepted: 10 October 2019 / Published: 12 October 2019
(This article belongs to the Section Stem Cells)
The corneal endothelium regulates corneal hydration to maintain the transparency of cornea. Lacking regenerative capacity, corneal endothelial cell loss due to aging and diseases can lead to corneal edema and vision loss. There is limited information on the existence of corneal endothelial progenitors. We conducted ultrastructural examinations and expression analyses on the human transition zone (TZ) at the posterior limbus of corneal periphery, to elucidate if the TZ harbored progenitor-like cells, and to reveal their niche characteristics. Within the narrow TZ (~190 μm width), the inner TZ—adjacent to the peripheral endothelium (PE)—contained cells expressing stem/progenitor markers (Sox2, Lgr5, CD34, Pitx2, telomerase). They were located on the inner TZ surface and in its underlying stroma. Lgr5 positive cells projected as multicellular clusters into the PE. Under transmission electron microscopy and serial block face-scanning electron microscopy and three-dimensional (3D) reconstruction, the terminal margin of Descemet’s membrane was inserted beneath the TZ surface, with the distance akin to the inner TZ breadth. Porcine TZ cells were isolated and proliferated into a confluent monolayer and differentiated to cells expressing corneal endothelial markers (ZO1, Na+K+ATPase) on cell surface. In conclusion, we have identified a novel inner TZ containing progenitor-like cells, which could serve the regenerative potential for corneal endothelium. View Full-Text
Keywords: corneal endothelium; posterior limbus; transition zone; corneal endothelial progenitors; morphology; cell culture corneal endothelium; posterior limbus; transition zone; corneal endothelial progenitors; morphology; cell culture
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MDPI and ACS Style

Yam, G. .-F.; Seah, X.; Yusoff, N.Z.B.M.; Setiawan, M.; Wahlig, S.; Htoon, H.M.; Peh, G.S.; Kocaba, V.; Mehta, J.S. Characterization of Human Transition Zone Reveals a Putative Progenitor-Enriched Niche of Corneal Endothelium. Cells 2019, 8, 1244.

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