Abstract
Abstract: :
Purpose. The expression of keratin 12 (K12) signifies the corneal type epithelial differentiation, whereas K14 is expressed by basal cells of all stratified epithelia. The expression pattern of K14 and k12 was used to elucidate the kinetics of corneal epithelium differentiation and maturation during embryonic development and postnatal growth. Methods. Paraffin sections were prepared from eyes of time mated FVB/N mouse embryos (E15.5 through E19.5) and postnatal day P30, P60 and P90 and 7 months, and were subjected to immunofluorescence staining with anti–K12 and K14 antibodies. In another series of experiments, cell suspension prepared from corneal epithelium of P30, P60 and P90 were double stained with both antibodies. Results. During embryonic development, it was found that K12 expression commenced at E15 and peaked at E17.5, and then gradually declined to a very low level at birth. The K12 expression increased from P4 and reached to a plateau three week after birth. During this period (E15.5–P21), the expression of K12 was limited to the suprabasal cells of corneal epithelium, while the K14 expression was found in the basal cells. After P21, sporadic K12 expression could be detected in the basal corneal epithelium, and the number of K12–positive basal cells increased as the mice grew older. Flat mount staining with anti–K12 revealed that basal cells remained negative at P21 and positive at 7 months. Double immune staining of epithelial cell suspension with anti–K12 and K14 antibodies indicated that the number of K14 positive cells simultaneously expressing K12 increased with ages of the experimental mice, 31.7 ± 11.5 % in P30, 34.7 ± 5.4 % in P60, and 50.0 ± 7.3 % in P90. Conclusions. Our observations are consistent with the notion that basal corneal epithelial cells of young mice (<p21) are K12 negative and may maintain limbal stem cell characteristics.
Keywords: cornea: epithelium • keratitis • immunohistochemistry