Plasminogen activator inhibitor type 2 in human corneal epithelium.
OBJECTIVE
To examine normal human corneal epithelium in vivo and in vitro for expression and status of plasniinogcn activ:ltor inhibitor type 2 (PAI-2).


METHODS
Normal hiuman corneas were prepared for frozen sections and for culture of corneal keratinocytes. PAI-2 was analyzed by immunohistochemistry and western blot analysis uising antibodies that recognize all forms of PAI-2.


RESULTS
In vivo and in vitro, PAI-2 was immunohistochemically localized to the superficial corneal keratinocytes. Immunostaining also revealed the presence of PAI-2 in its relaxed (i.e., cleaved) conformation. In vivo, the staining pattern of the relaxed form was identical with that of total PAI-2, but in vitro the relaxed form was detected in a smaller subpopulation of superficial cells. In vitro, the staining pattern indicated a cytoplasmic localization for PAI-2. Western blot analysis revealed that most of the PAI-2 was cell associated and functionally active.


CONCLUSIONS
The present results are the first to show that PAI-2 is found in normal human corneal epithelium in vivo and in vitro, where it can be considered as a differentiation product. At least in vitro, all detectable PAI-2 is cell associated, with a cytoplasmic distribution. A subpopulation of keratinocytes also contains PAI-2 in its relaxed (i.e., cleaved) conformation. Cleavage by an as yet unidentified cytoplasmic proteinase may constitute a crucial aspect of the function of corneal epithelial PAI-2, which may be relevant to terminal differentiation and death of the corneal keratinocyte.
Department of Dermatology, University of Pennsylvania School of Medicine, Philadelphia 19104-6142, USA.
D L
DL
Williams
B
B
Risse
S
S
Kim
D
D
Saunders
S
S
Orlin
M S
MS
Baker
P J
PJ
Jensen
R M
RM
Lavker
D015153:Blotting, Western; D002478:Cells, Cultured; D019573:Epithelium, Corneal / Q000737:chemistry* / Q000166:cytology; D006801:Humans; D007124:Immunoenzyme Techniques; D017396:Plasminogen Activator Inhibitor 2 / Q000032:analysis*; D015842:Serine Proteinase Inhibitors / Q000032:analysis*
D017396:Plasminogen Activator Inhibitor 2; D015842:Serine Proteinase Inhibitors