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Sidney Julio Sousa, Antonio Haddad; Proliferative Behavior of Male Albino Rabbit Corneal Epithelium. Invest. Ophthalmol. Vis. Sci. 2014;55(13):5159.
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To analyze the proliferative behavior of the rabbit corneal epithelium and establish if any region was preferentially involved in the epithelial maintenance.
Six rabbits were intravitreally injected with 3H-thymidine and killed 8 h afterwards. The distribution of labeled nuclei from limbus to the corneal center was measured at 0.25 mm steps. Four pairs of rabbits were killed at 6 h, 2, 28 and 90 days after a single intravitreal injection of the isotope. They were used to locate labeled nuclei inside the corneal epithelium. Two pairs of rabbits were intravitreally injected three times at intervals of four days and killed at 12 and 49 days after the first injection. The labeling index was estimated for the whole epithelium as well as for the epithelial layers of the cornea and limbus. Semithin sections of the cornea and the limbus were processed for high resolution autoradiography at the light microscope level.
Everywhere it was possible to detect segments with active replication (on) alternating with segments with no cell division (off), suggesting that the reproduction of the epithelial surface of the cornea follows an on/off mosaic pattern. The heavy labeling of the outermost layers coupled with few or no labeled nuclei at the basal stratum, found in the limbus, is an indication that this region is a site of quick cell differentiation and not home of slow cycling cells. The conspicuous and protracted labeling of the basal layer of the corneal epithelium suggest that its cells undergo repeated cycles of replication before being sent to the suprabasal strata. This is the model of replication more prone to generate label retaining cells.
If label retaining cells are adult stems cells, one must conclude that they reside in the corneal and not the limbal basal layer. One may also infer that the basal cells of the cornea and not of the limbus are the ones with the main burden of renewing the corneal epithelium.
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