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S. Faria, R.M. Goes, E.M. Laicine, A. Haddad; An Autoradiograph Study of Regeneration of Rabbit Corneal Epithelium After Debridement on Its Central Region . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2757.
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damage to the corneal epithelium elicits stimulation to proliferation. The proliferative behavior of the peripheral cornea and limbal epithelium was investigated following scraping of the central corneal epithelium.
under general anesthesia, a 4 mm diameter circular portion of the epithelium was scraped from the right central cornea of 21 young adult rabbits (Oryctolagus cuniculus) and followed by intravitreal injection of 3H–thymidine (3H–TdR) into both eyes. Paraffin and resin semithin sections of the right (experimental) and left (control) corneas were processed for autoradiography. Estimations of epithelial labeling indices were done on rabbits killed in groups of three at 1, 2, 3, 4, 14, 28 and 60 days after debridement.
At 1 day the labeling indices were comparable in both eyes. The distribution of labeled nuclei was extremely uneven throughout the cornea, being possible to visualize segments of unlabeled epithelium larger than the width of the limbus. From the 2nd to the 60th days most of the epithelial cells surrounding the lesion as well as the ones making up the newly formed epithelium (72 – 91%) had their nuclei labeled with 3H–TdR. There was a decrease in the silver grain density over individual nuclei from the earliest (1day) to the latest (60 days) time interval but not in the percentage of labeled nuclei in the central region of the cornea. Labeled epithelial cells were also visualized in control corneas, although less frequently than in the experimental group, even at the 60–day time interval in all layers of the corneal epithelium. The labeling of the epithelium at the peripheral cornea as well as at the limbus was comparable in both groups. In both groups labeled nuclei were not visualized in the basal stratum of the limbus, from 21 days onwards.
No stimulation for epithelial proliferation was detected in the corneal periphery and limbus. Label–retaining cells were overwhelmingly localized in the central region, with some in the remainder of the peripheral cornea but not in the basal stratum of the limbus. Therefore, the results obtained in mice (Cotsarelis et al. Cell 57: 201, 1989; Lehrer et al. J Cell Sci 111: 2867, 1998) – proposing the concept of label–retaining cells – were not observed in the rabbit cornea.
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