Plasminogen activator inhibitor‐2 expression in inflamed appendix

Plasminogen activator inhibitors are thought to be responsible for the abolition of fibrinolytic activity in inflamed peritoneum. This reduction in the fibrin clearing capacity of the peritoneum promotes the formation of intraabdominal adhesions. High concentrations of plasminogen activator inhibitor‐2 (PAI‐2) have been previously found in inflamed peritoneal tissue using immunoassays, but it is undetectable in normal peritoneum. The aim of this study was to localize plasminogen activator inhibitor‐2 production in tissue by in situ mRNA hybridisation. Sections of normal and inflamed human appendix were hybridised with a digoxigenin labelled cDNA probe. In normal appendix staining was confined to macrophages in the mucosa. Macrophage staining was also seen in inflamed tissue but with a wider distribution throughout the appendix wall. PAI‐2 was also localized to mesothelial cells of inflamed but not normal appendix. Cell identities were confirmed using immunohistochemistry directed against cell specific markers. Staining was absent from control slides incubated with plasmid DNA or PAI‐2 probe following ribonuclease digestion. The identification of the cells expressing the PAI‐2 gene in peritoneum increases our understanding of the pathophysiological process leading to fibrin deposition within the abdomen during peritonitis.