Abstract
Abstract: :
Purpose: Corneal epithelial stem cells are believed to be slow cycling (BrdU label retaining) and p63-positive. In adult cornea, the p63 positive cells are localized to the basal cells of the limbal epithelium, but not in the central cornea. The purpose of this study is to see if central cornea is devoid of p63-positive cells from the beginning of the postnatal life in rat. Methods: Cornea/limbus tissues obtained from rats of different ages were immunostained with antibodies to p63, PCNA, and keratin-3 , to delineate the developmental and differentiational changes of these there cell markers in rat cornea during postnatal development. Results: We found that in one day-old rats, corneal epithelium is one cell-thick and all the cells are strongly positive with p63, keratin-3 and PCNA. In two week-old rats, the cornea epithelium is 5 cell-thick and can be morphologically differentiated into squamous, wing, and basal cells. At this stage, the basal and suprabasal cells of the limbal epithelium are all p63, keratin-3 and PCNA positive. In the central cornea, both basal and suprabasal cells are all strongly positive with keratin-3. However, only the basal cells are positive with p63 and PCNA, whereas the suprabasal cells are negative with both antigens. In one month-old rats, the basal and suprabasal cells of the limbus are still all positive with p63, keratin-3 and PCNA. The expression of these three antigens in the central cornea are similar to that of the two week-old rats, however, there are some cells that are p63 and PCNA negative. In 3 month-old rats and older, the expression pattens of p63, keratin-3 and PCNA remain unchanged in the limbal basal and suprabasal cells. The expression of keratin-3 in the basal and suprabasal cells of the central cornea is also unchanged, however, at this stage, p63 and PCNA can no longer be detected in the central cornea. Conclusions: Currently, it is believed that the epithelial stem cells are p63 positive, the young TA cells are p63 and PCNA positive and the older TA cells are PCNA positive alone. Our observation appears to be discordante with this believe. During postnatal development, the distribution pattern of p63 in cornea/limbus seems to be more resemble to that of the cornea during wound repairing processes.
Keywords: cornea: epithelium