HISTOLOGY AND HISTOPATHOLOGY

Cellular and Molecular Biology

 

Dipeptidyl peptidase IV (DPPIV) activity in the tear fluid as an indicator of the severity of corneal injury: a histochemical and biochemical study

J. Cejková, Z. Zvárová2 and C. Cejka1

1Department of Eye Histochemistry, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czech Republic and 2EuroMISE Center, Institute of Computer Science of the Academy of Sciences of the Czech Republic, Prague, Czech Republic

Offprint requests to: Prof. Jitka CejkováMD, PhD, DSc, Head, Department of Eye Histochemistry and Pharmacology, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Vídenska 1083, 14220, Prague 4. Fax: (420) 241062692 e-mail: cejkova@biomed.cas.cz

 

Summary. Comparative histochemical and biochemical studies on the catalytically active protease Dipeptidyl peptidase IV (DPPIV), have been performed in the rabbit cornea and the tear fluid using a sensitive fluorogenic substrate, Gly-Pro-7-amino-4-Trifluoromethyl Coumarine (AFC). In both normal and experimentally injured corneas, DPPIV activity was detected histochemically and in the tear fluid biochemically. In contrast to the normal cornea where DPPIV activity was absent and in the tear fluid where it was low, during continuous wearing of contact lenses or repeated irradiation of the cornea with UVB rays, slight DPPIV activity appeared first in the superficial layers of the corneal epithelium, while later increased activity was present in the whole epithelium. This paralleled elevated DPPIV activity in the tear fluid. Moreover, during continuous contact lens wear, the increased DPPIV activity in the tear fluid was, in many cases, coincidental with the presence of capillaries in the limbal part of the corneal stroma. After severe alkali burns when corneal ulcers appeared, collagen fragments were active for DPPIV, which was associated with high DPPIV activity in the tear fluid. In conclusion, Gly-Pro-AFC was found to be useful for comparative histochemical and biochemical studies on DPPIV activity in the experimentally injured rabbit eye. Using the method of the tear film collection by a short touch of substrate punches to the respective site of the cornea or conjunctiva we can show that in experimental injuries (wearing of contact lenses, irradiation of the cornea with UVB rays), the damaged corneal cells were the main source for DPPIV activity in the tear fluid. It is suggested that the activity of DPPIV measured in the tear fluid might serve as an indicator of early corneal disorders, e.g. corneal vascularization related to contact lens wear. Histol. Histopathol. 19, 669-676 (2004)

Key words: Dipeptidyl peptidase IV, tear fluid, corneal injury

DOI: 10.14670/HH-19.669