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J. Zhao, L. Chen, T. Nagasaki; Epithelial Cell Movements in a Vascularized Cornea. Invest. Ophthalmol. Vis. Sci. 2009;50(13):6290.
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In a normal, avascular cornea, epithelial cells exhibit constant centripetal movements, whereas in a totally vascularized cornea, such as a conjunctivalized cornea and a Dstncorn1 cornea, epithelial cells are mostly stationary. This study was initiated to investigate whether there is a causal relationship between homeostatic epithelial cell movements and development of an underlying vasculature.
Ubiquitous GFP mice were used. Epithelial movements were determined in vivo by tracking changes of epithelial GFP in a partially vascularized cornea, which was created by placing a 11-0 thread suture at two eccentric locations. Epithelial DNA synthesis was determined by incorporation of systemic 5-ethynyl-2'-deoxyuridine into DNA. To determine levels of diffusible blood components in a normal and a vascularized cornea, animals received fluorescently labeled dextran of various sizes systemically with an osmotic pump, and a steady-state level of fluorescence along the diameter of a cornea was determined by quantitative imaging microscopy.
Sutures triggered localized neovascularization from the limbus and several blood vessel trunks reached the suture in 1 to 2 weeks. The sutured area developed mild opacity but there was no stromal fibrosis. Before the surgery, epithelial cells moved centripetally toward a single point near the corneal center. After suturing and blood vessel formation, epithelial cells ceased to converge at this central point and they were instead diverted toward the nearer of the two sutured areas. This was not a typical epithelial wound healing reaction because epithelial cells were mostly intact at all times, except a minor one-time suturing damage. Cells directly above the blood vessels appeared to move slower than others. Sub-basal nerves in a sutured cornea were directed toward the nearest suture instead of the corneal center, matching the pattern of epithelial movements. There was no significant difference in DNA synthesis between epithelial cells of a vascularized and a non-vascularized area. A systemic labeling with fluorescently labeled dextran showed that a normal cornea exhibited a decreasing radial gradient of fluorescence from the limbus to the central cornea, while a vascularized cornea contained an increased level of fluorescence with no limbus-to-center gradient, suggesting that a concentration of blood components was elevated in a vascularized cornea.
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