Expression of Keratinocyte Transglutaminase in Cornea of Vitamin A–Deficient Rats.

Purpose : To determine the role played by keratinocyte transglutaminase (TG1, TG K ) in the abnormal keratinization of the cornea. Methods : Vitamin A–deficient rats were produced as a model of severe dry eyes, and the expression of the mRNA and the enzyme activity of TG1 were examined in the corneas. The envelope proteins and keratins of cornified cells were also examined immunohistochemically. Results : The expression and enzyme activity of TG1 mRNA on the ocular surface were significantly upregulated as the vitamin A deficiency developed. As the TG1 expression was upregulated, involucrin, loricrin, and keratin 10 began to be expressed on the epithelial cells of the cornea. Conclusions : Upregulation of TG1 expression followed by the appearance of the envelope proteins and keratin10 in cornified cells indicated that TG1 is involved in the abnormal keratinization of the cornea. [ABSTRACT FROM AUTHOR]