Plasminogen activator inhibitor type 2 (PAI-2) is present in normal human conjunctiva

Area of Science:

• Ocular surface biology
• Cellular and molecular biology
• Biochemistry

Background:

• Plasminogen activator inhibitor type 2 (PAI-2) is a key regulator of the fibrinolytic system.
• Understanding PAI-2 expression in ocular tissues is crucial for comprehending ocular surface homeostasis and disease.
• Previous studies have characterized PAI-2 in corneal epithelia, but its distribution in conjunctival epithelia requires further elucidation.

Purpose of the Study:

• To characterize the expression and localization of plasminogen activator inhibitor type 2 (PAI-2) in normal human conjunctiva.
• To investigate the in vivo and in vitro expression patterns of PAI-2 in conjunctival epithelial cells.
• To compare PAI-2 distribution in conjunctival epithelia with that in corneal epithelia.

Main Methods:

• Immunohistochemistry and immunoblotting were employed to detect and quantify PAI-2 antigen in human conjunctival tissue and cultured conjunctival keratinocytes.
• Analysis of PAI-2 molecular weight and cellular localization was performed.
• The activity of PAI-2 was assessed by its ability to complex with urokinase plasminogen activator (uPA).

Main Results:

• PAI-2 was consistently detected in normal human conjunctival epithelia, primarily in superficial keratinocytes and sometimes in deeper layers, concentrated at the cell periphery.
• PAI-2 in conjunctival epithelial extracts and cultured cells exhibited an apparent molecular weight of 45 kDa (non-glycosylated form).
• Approximately 90% of PAI-2 was cell-associated, with a smaller, active, glycosylated form released into conditioned media over time. PAI-2 levels were higher in differentiated keratinocyte cultures.

Conclusions:

• PAI-2 is constitutively expressed by normal human conjunctival epithelial cells in vivo and in vitro.
• The distinct distribution of PAI-2 in conjunctival epithelia compared to corneal epithelia suggests tissue-specific functions.
• The role of PAI-2 in conjunctival and corneal epithelial cells warrants further investigation, potentially related to their unique physiological roles.