Expression of Sp1 and KLF6 in the developing human cornea

To examine the temporal and spatial expression of Sp1 and Krüppel-like factor 6 (KLF6) in the cornea in fetal and adult human eyes.

Eyes from human fetus (F) of 7, 9, 10, 11, 13, and 27 weeks (w) of gestation, as well as corneas from 11 and 56-day (d)-old children and donors 2, 6, 16, 25, 40, 51, 69, and 83 years (y) of age were obtained. All specimens were fixed in 10% buffered formalin, processed for paraffin sections, and examined for Sp1 and KLF6 expression immunohistochemically.

Staining for Sp1 was evident at the earliest F7w time point in the cornea. From F7w to F27w, the moderate to strong Sp1 immunostaining was seen in the nuclei of epithelial and endothelial cells. Staining in keratocytes was also observed. The intensity of Sp1 staining in all layers of the cornea was substantially decreased 11d after birth and remained low thereafter. Positive KLF6 staining was also noted at F7w in all corneal layers. In the epithelium and endothelium, the staining was mostly cytoplasmic throughout the fetal stages. After birth, the KLF6 staining appeared in the nuclei of corneal epithelial cells along with that in the cytoplasm. The intensity of KLF6 staining in the epithelium and endothelium remained relatively constant from E47d to the 83y-old donor cornea. The KLF6 staining in the stroma however was reduced after F27w.

The present study indicates that the expression of Sp1 and KLF6 is developmentally regulated, providing a basis for further investigations on the regulation of the Sp1 and KLF6 gene during the course of corneal development and in corneal diseases such as keratoconus.