Localization of plasminogen activator inhibitor‐1 production in inflamed appendix by in situ mRNA hybridization

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Abstract
The peritoneum has been shown to possess fibrinolytic activity which is thought to play a role in the prevention of intra‐abdominal adhesion formation. Recently inflamed peritoneal tissue has been shown to have reduced fibrinolytic activity secondary to increased levels of plasminogen activator inhibitor‐1 (PAI‐1). The aim of this study was to localize the production of PAI‐1 in appendix tissue using in situ mRNA hybridization. Sections of normal and inflamed appendix were hybridized with a digoxigenin‐labelled cDNA probe. PAI‐1 production was localized to both mcsothelium and serosal blood vessel endothelium in all inflamed appendix samples. Cell identities were confirmed using immunohistochemistry directed against mesothelial and endothlial cell markers. Staining was not seen on sections of normal appendix or on negative control slides of inflamed appendix (hybridization with plasmid DNA, PAI‐1 probe following ribonuclease digestion). The identification of the cells expressing the PAI‐1 gene in peritoneum increases our understanding of the pathophysiological changes in fibrinolytic activity which occur in inflammation and may lead to adhesion formation.